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Forest Stands (forest + stand)
Selected AbstractsModelling Tree Roots in Mixed Forest Stands by Inhomogeneous Marked Gibbs Point ProcessesBIOMETRICAL JOURNAL, Issue 3 2009Stefanie Eckel Abstract The aim of the paper is to apply point processes to root data modelling. We propose a new approach to parametric inference when the data are inhomogeneous replicated marked point patterns. We generalize Geyer's saturation point process to a model, which combines inhomogeneity, marks and interaction between the marked points. Furthermore, the inhomogeneity influences the definition of the neighbourhood of points. Using the maximum pseudolikelihood method, this model is then fitted to root data from mixed stands of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) to quantify the degree of root aggregation in such mixed stands. According to the analysis there is no evidence that the two root systems are not independent. [source] Genetic Variation in Fragmented Forest Stands of the Andean Oak Quercus humboldtii Bonpl. (Fagaceae),BIOTROPICA, Issue 1 2007Juan F. Fernández-M. ABSTRACT Quercus humboldtii is a montane forest dominant species in Colombia, which has experienced significant habitat loss. Using three microsatellite loci, we compared the genetic diversity of adults and seedlings in fragments of small and large size. Results show high genetic diversity, comparable to other temperate oak species (Ho= 0.813, He= 0.780, and f=,0.044). However, allelic richness reduction in seedlings of the most fragmented part of the landscape, suggested restricted gene flow and risk of future genetic bottlenecks, if larger tracts of forest disappear. RESUMEN Quercus humboldtii es una especie dominante de las montañas colombianas que ha sufrido una importante perdida de hábitat. Usando marcadores microsatélites, comparamos la diversidad genética de adultos y plántulas en fragmentos pequeños y grandes. Encontramos una alta diversidad genética, comparable a las especies de robles de zonas templadas (Ho= 0.813, He= 0.780 y f=,0.044). Sin embargo, existe una reducción en la riqueza alélica de las plántulas de la zona más fragmentada, sugiriendo que deben conservarse grandes áreas boscosas para evitar riesgos futuros de pérdida de la diversidad genética. [source] Effect of selective logging on forest structure and nutrient cycling in a seasonally dry Brazilian Atlantic forestJOURNAL OF BIOGEOGRAPHY, Issue 3 2006Dora Maria Villela Abstract Aim, The Brazilian Atlantic forest covers c. 10% of its original extent, and some areas are still being logged. Although several ecological studies in Atlantic forest have been published over the past two to three decades, there has been little research on forest dynamics and there is a particular lack of information on the effects of disturbance. The aim of the present study was to assess the impact of selective logging on forest structure, floristic composition soil nutrients, litterfall and litter layer in a seasonally dry Atlantic forest. Location, The Mata do Carvão is located in the Guaxindiba Ecological Reserve in São Francisco do ltabapoana district (21°24, S, 41°04, W), Rio de Janeiro, Brazil. Methods, Four plots (50 × 50 m) were set up in 1995 in each of two stands: unlogged and logged. In each plot, all trees , 10 cm d.b.h. were enumerated, identified and measured. Vouchers were lodged at UENF Herbarium. Five surface soil samples were collected in each plot in the dry season (in October 1995). Litterfall was collected in eight traps (0.50 m2) in each plot over a year from 14 November 1995 to 11 November 1996. The litter layer was sampled in eight quadrats (0.25 m2) in each plot in the dry and wet seasons. Soils were air-dried, sieved, and chemically analysed. The litter was dried (80 °C), sorted into six fractions, weighed and bulked samples analysed for nutrients. Results, Forest stands did not differ in stem density and total basal area, with a total of 1137 individuals sampled in 1996 (564 unlogged and 573 logged), and a total basal area of 15 m2 (unlogged) and 13.0 m2 (logged). However, unlogged stands had more large trees (, 30 cm in d.b.h.) and greater mean canopy height. Among the families, Rutaceae and Leguminosae were the most abundant families in both sites, although the Rutaceae had a higher density in unlogged and Leguminosae in the logged stand. The species diversity index was similar between stands. Late-successional species, such as Metrodorea nigra var. brevifolia and Paratecoma peroba, were less abundant in the logged stand. Selective logging did not affect nutrient concentrations in the soil or in the litter. However, quantities of the nutrients in the total litterfall and in the leaf litterfall and litter layer were higher in unlogged than in logged stands, mainly as a result of fallen M. nigra leaves. Metrodorea nigra was considered a key species in the nutrients dynamics in Carvão forest. Main conclusions, Despite the fact that effects on tree diversity and soil nutrients were not clear, selective logging in this Atlantic forest altered canopy structure, increased the relative abundance of some early-secondary species and decreased the litter input and stock of nutrients. Detailed information on the influence of logging on the distribution and structure of plant populations and in nutrient processes is fundamental for a sustainable logging system to be developed. [source] Spatiotemporal changes of beetle communities across a tree diversity gradientDIVERSITY AND DISTRIBUTIONS, Issue 4 2009Stephanie Sobek Abstract Aim, Plant and arthropod diversity are often related, but data on the role of mature tree diversity on canopy insect communities are fragmentary. We compare species richness of canopy beetles across a tree diversity gradient ranging from mono-dominant beech to mixed stands within a deciduous forest, and analyse community composition changes across space and time. Location, Germany's largest exclusively deciduous forest, the Hainich National Park (Thuringia). Methods, We used flight interception traps to assess the beetle fauna of various tree species, and applied additive partitioning to examine spatiotemporal patterns of diversity. Results, Species richness of beetle communities increased across the tree diversity gradient from 99 to 181 species per forest stand. Intra- and interspecific spatial turnover among trees contributed more than temporal turnover among months to the total ,-beetle diversity of the sampled stands. However, due to parallel increases in the number of habitat generalists and the number of species in each feeding guild (herbivores, predators and fungivores), no proportional changes in community composition could be observed. If only beech trees were analysed across the gradient, patterns were similar but temporal (monthly) species turnover was higher compared to spatial turnover among trees and not related to tree diversity. Main conclusions, The changes in species richness and community composition across the gradient can be explained by habitat heterogeneity, which increased with the mix of tree species. We conclude that understanding temporal and spatial species turnover is the key to understanding biodiversity patterns. Mono-dominant beech stands are insufficient to conserve fully the regional species richness of the remaining semi-natural deciduous forest habitats in Central Europe, and analysing beech alone would have resulted in the misleading conclusion that temporal (monthly) turnover contributes more to beetle diversity than spatial turnover among different tree species or tree individuals. [source] 6000 years of forest dynamics in Suserup Skov, a seminatural Danish woodlandGLOBAL ECOLOGY, Issue 2 2000Gina E. Hannon Abstract 1The history of a forest stand over the last 6000 years has been reconstructed by studying pollen, macrofossils and charcoal from a small, wet hollow in Suserup Skov on the island of Sjælland in eastern Denmark. 2The earliest recorded forest was Tilia -dominated but contained an intimate mixture of many different tree species that included Acer campestre, A. platanoides, Alnus glutinosa, Betula pubescens, Corylus avellana, Frangula alnus, Fraxinus excelsior, Malus sylvestris, Populus tremula, Pinus sylvestris, Quercus robur, Q. petraea, Salix spp., Sorbus aucuparia, Tilia cordata and T. platyphyllos. The preserved fruits of T. platyphyllos confirm its hitherto doubtful status as a native member of the Danish flora. 3The present-day woodland developed after a period of intensive anthropogenic disturbance between , 600 bc and ad 900, during which time open canopy conditions prevailed at Suserup. Fagus sylvatica and Fraxinus excelsior are the dominant trees at present, together with some Quercus robur and Ulmus glabra.4,Charcoal was present in the sediments from most time periods except at the Ulmus decline. In the last 1000 years of the sequence , the period of Fagus dominance , charcoal counts were consistently low. 5Pinus sylvestris was a natural component of this primarily deciduous forest, and the last macrofossil find dates from c. ad 900. Macrofossil Pinus cone scales recorded c. ad 1800 originate from planted individuals. Prior to Fagus dominance, the forest had an open structure partly caused by frequent, low-intensity fires associated with the presence of Pinus sylvestris. 6The replacement of Tilia by Fagus in this forest was catalysed by human activity. If the forest had not been so disturbed, the rich diversity of trees would most probably have persisted up to the present time, with only a moderate-sized Fagus population. [source] An overview of the field and modelling studies on the effects of forest devastation on flooding and environmental issuesHYDROLOGICAL PROCESSES, Issue 5 2010Yuichi Onda Abstract Intensive field observations as well as monitoring of discharge, water quality, and soil erosion have been conducted in forest plantations in order to identify the effects of forest cover and management practices on runoff generation, sediment transport, and downstream environmental issues. Five experimental catchments, each with rather uniform lithology, were established in both managed and unmanaged plantations of Japanese cypress and cedar, as well as broadleaf forests. Field monitoring was conducted from sub-plots (e.g. splash cups) to small hillslope plots (0·5 × 2 m) to large hillslope-scale plots to first order streams (0·1,4 ha) and finally to larger catchments (>4 ha) in a nested structure. Remote sensing techniques were employed to identify broad scale forest stand and soil surface conditions. As part of this integrated study, these field-based monitoring and remote sensing techniques provide information for modelling runoff generation and developing adaptive management schemes with respect to catchment-scale water resources. Copyright © 2010 John Wiley & Sons, Ltd. [source] Measurements of transpiration in four tropical rainforest types of north Queensland, AustraliaHYDROLOGICAL PROCESSES, Issue 26 2007David McJannet Abstract Transpiration of four different rainforest types in north Queensland, Australia, was determined using the heat pulse technique for periods ranging between 391 and 657 days. Despite the complexity of the natural rainforest systems being studied, the relationship between sample tree size and daily water use was found to be strong, thus providing a robust means by which to scale transpiration from individual trees to the entire forest stand. Transpiration was shown to be dependent on solar radiation and atmospheric demand for moisture with little evidence of limitation by soil moisture supply. Total stand transpiration was controlled by forest characteristics such as stem density, size distribution and sapwood area. Annual transpiration for each of the four sites ranged between 353 mm for cloud forest and 591 mm for montane rainforest. In comparison with the international literature, transpiration from Australian rainforests is low; the reasons for this could be related to a combination of differences in forest structure, climatic conditions, canopy wetness duration and tree physiology. Copyright © 2007 John Wiley & Sons, Ltd. [source] The solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site, southern ChileHYDROLOGICAL PROCESSES, Issue 13 2002Geertrui Y. P. Uyttendaele Abstract Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44,S, 73°10,W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca2+ l,1, 0·13 mg K+ l,1, 0·11 mg Mg2+ l,1 and <0·08 mg NH4,N l,1), except for sodium (1·10 mg l,1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO3,N l,1, total flux 6·3 kg NO3,N ha,1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l,1) for all events. Stream-flow pH was 6·3 and conductivity was 28·3 ,s. Stream-water chemistry was also dominated by sodium (2·70 mg l,1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l,1). The solute budget indicated a net loss of 3·8 kg Na+ ha,1 year,1, 5·4 kg Mg2+ ha,1 year,1, 1·5 kg Ca2+ ha,1 year,1 and 0·9 kg K+ ha,1 year,1, while 4·9 kg NO3,N ha,1 year,1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO3,N ha,1 year,1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na+ ha,1 year,1, 21·5 kg K+ ha,1 year,1, 5·1 kg Mg2+ ha,1 year,1) compared with the secondary native forest site (24·7 kg Na+ ha,1 year,1, 18·9 kg K+ ha,1 year,1 and 4·4 kg Mg2+ ha,1 year,1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca2+ ha,1 year,1) compared with the pine stand (12·6 kg Ca2+ ha,1 year,1). Copyright © 2002 John Wiley & Sons, Ltd. [source] Soil frost effects on soil water and runoff dynamics along a boreal forest transect: 1.HYDROLOGICAL PROCESSES, Issue 6 2001Field investigations Abstract To determine how soil frost changes flowpaths of runoff water along a hillslope, a transect consisting of four soil profiles directed towards a small stream in a mature forest stand was investigated at Svartberget, near Vindeln in northern Sweden. Soil temperature, unfrozen water content, groundwater level and snow depth were investigated along the transect, which started at the riparian peat, and extended 30 m upslope into mineral soils. The two, more organic-rich profiles closest to the stream had higher water retention and wetter autumn conditions than the sandy mineral soils further upslope. The organic content of the soil influenced the variation in frost along the transect. The first winter (1995,96) had abnormally low snow precipitation, which gave a deep frost down to 40,80 cm, whereas the two following winters had frost depths of 5,20 cm. During winter 1995,96, the two organic profiles close to the stream had a shallower frost depth than the mineral soil profile higher upslope, but a considerably larger amount of frozen water. The fraction of water that did not freeze despite several minus degrees in the soil was 5,7 vol.% in the mineral soil and 10,15 vol.% in the organic soil. From the measurements there were no signs of perched water tables during any of the three snowmelt periods, which would have been strong evidence for changed water flowpaths due to soil frost. When shallow soil layers became saturated during snowmelt, especially in 1997 and 1998, it was because of rising groundwater levels. Several rain on frozen ground events during spring 1996 resulted in little runoff, since most of the rain either froze in the soil or filled up the soil water storage. Copyright © 2001 John Wiley & Sons, Ltd. [source] The millennial dynamics of a boreal forest stand from buried treesJOURNAL OF ECOLOGY, Issue 3 2004DOMINIQUE ARSENEAULT Summary 1We reconstructed the dynamics of a black spruce (Picea mariana) and jack pine (Pinus banksiana) forest stand in northern Québec using a continuous, 5200-year-long sequence of stem remains buried in adjacent peatland. Simulations of recruitment of such remains provided guidelines for inferring past ecosystem structure and composition at the stand scale. 2Compared with the late Holocene (4650,0 cal. year BP (CYBP)), the mid Holocene (5200,4650 CYBP) period was characterized by faster tree growth, larger stems and higher stem density, indicating higher forest productivity in association with a milder climate. 3The presence of stem remains of both species from 17 out of 20 contiguous 250-year time intervals suggests that the spruce-pine stand exhibited high compositional stability, with both species regenerating after fire from canopy-stored seed banks. 4Relative species abundance closely followed the duration of past fire intervals deduced from the number of tree rings in buried conifers. Time periods of long (4650,3950, 3400,1850 and 250,0 CYBP) and short fire intervals (4950,4650, 3950,3400 and 1850,250 CYBP) were associated, respectively, with decreasing and increasing pine abundance, probably reflecting faster juvenile growth, lower shade tolerance, earlier sexual maturity and shorter longevity in jack pine compared with black spruce. 5We conclude that both climate change and climate-induced fire disturbance have been driving long-term ecosystem dynamics. Our field evidence supports the idea that interactions between disturbances and the life-history traits of species modulate the impact of climate change at the scale of forest stands. At the same time, disturbances may result in long-term stability of disturbance-adapted ecosystems. [source] Soil nutrient supply and biomass production in a mixed forest on a skeleton-rich soil and an adjacent beech forestJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2002Dirk Hölscher Abstract In the natural forest communities of Central Europe, beech (Fagus sylvatica L.) predominates in the tree layer over a wide range of soil conditions. An exception with respect to the dominance of beech are skeleton-rich soils such as screes where up to 10 broad-leaved trees co-exist. In such a Tilia-Fagus-Fraxinus-Acer-Ulmus forest and an adjacent mono-specific beech forest we compared (1) soil nutrient pools and net nitrogen mineralization rates, (2) leaf nutrient levels, and (3) leaf litter production and stem increment rates in order to evaluate the relationship between soil conditions and tree species composition. In the mixed forest only a small quantity of fine earth was present (35 g l,1) which was distributed in patches between basalt stones; whereas a significantly higher (P < 0.05) soil quantity (182 g l,1) was found in the beech forest. In the soil patches of the mixed forest C and N concentrations and also concentrations of exchangeable nutrients (K, Ca, Mg) were significantly higher than in the beech forest. Net N mineralization rates on soil dry weight basis in the mixed forest exceeded those in the beech forest by a factor of 2.6. Due to differences in fine earth and stone contents, the volume related soil K pool and the N mineralization rate were lower in the mixed forest (52 kg N ha,1 yr,1, 0,10 cm depth) than in the beech forest (105 kg N ha,1 yr,1). The leaf N and K concentrations of the beech trees did not differ significantly between the stands, which suggests that plant nutrition was not impaired. In the mixed forest leaf litter fall (11,%) and the increment rate of stem basal area (52,%) were lower than in the beech forest. Thus, compared with the adjacent beech forest, the mixed forest stand was characterized by a low volume of patchy distributed nutrient-rich soil, a lower volume related K pool and N mineralization rate, and low rates of stem increment. Together with other factors such as water availability these patterns may contribute to an explanation of the diverse tree species composition on Central European screes. Bodennährstoffangebot und Biomasseproduktion in einem Mischwald auf einem stark skeletthaltigen Standort und in einem benachbarten Buchenwald In den natürlichen Waldgesellschaften Mitteleuropas dominiert die Buche (Fagus sylvatica L.) über ein weites Spektrum an bodenchemischen Standortsbedingungen. Eine Ausnahme in Bezug auf die Buchendominaz bilden stark skeletthaltige Standorte, wie etwa Blockhalden, wo bis zu 10 Laubbaumarten gemeinsam vorkommen. In solch einem Tilia-Fagus-Fraxinus-Acer-Ulmus -Wald und einem benachbarten Buchenreinbestand haben wir (1) die Bodennährstoffvorräte und Stickstoffmineralisationsraten, (2) den Blattnährstoffstatus und (3) die Blattproduktion und die Stammzuwachsraten vergleichend untersucht, um die Beziehung zwischen den Bodenbedingungen und der Baumartenzusammensetzung zu charakterisieren. In dem Mischwald fanden wir nur eine geringe Menge an Feinboden (35 g l,1), die sich in Taschen zwischen den Basaltsteinen befand, wohingegen ein signifikant (P < 0.05) höherer Gehalt an Feinboden (182 g l,1) in dem Buchenwald vorhanden war. In den Bodentaschen des Mischwaldes waren die C- und N-Konzentrationen und auch die Konzentrationen an austauschbar gebundenem K, Ca und Mg signifikant höher als im Buchenwald. Die Netto-N-Mineralisation pro Gewichtseinheit im Mischwald überstieg diejenige im Buchenwald um den Faktor 2,6. Wegen der unterschiedlichen Anteile an Feinboden und Skelett waren der volumenbezogene K-Vorrat und die volumenbezogene N-Mineralisationsrate im Mischwald (52 kg N ha,1 yr,1, 0,10 cm Tiefe) geringer als im Buchenwald (105 kg N ha,1 yr,1). Die Blattnährstoffgehalte von Buchen unterschieden sich zwischen den beiden Beständen nicht signifikant, was darauf hinweist, dass die Pflanzenernährung nicht beeinträchtigt war. Der herbstliche Blattstreufall (11,%) und die Zuwachsraten der Stammquerflächen (52,%) waren im Mischwald geringer als im Buchenwald. Im Vergleich mit dem benachbarten Buchenwald wies der Mischwald somit einen geringen Gehalt an sehr ungleichmäßig verteiltem, nährstoffreichen Boden, geringere volumenbezogene K-Vorräte und N-Mineralisationsraten und geringe Stammzuwächse auf. Gemeinsam mit anderen Faktoren, wie etwa der Wasserverfügbarkeit, können diese Muster zu einer Erklärung der Baumartenvielfalt auf mitteleuropäischen Blockstandorten beitragen. [source] A Novel System for Spectral Analysis of Solar Radiation within a Mixed Beech-Spruce StandPLANT BIOLOGY, Issue 2 2002H. Reitmayer Abstract: A multi-sensor system is described, based on a 1024 channel diode array spectrometer, to measure spectral radiant flux density in the range of 380 nm to 850 nm, with a resolution of 0.8 nm in minimal 16 milliseconds integration time per sensor (noon, clear sky conditions). 264 space-integrating 4, sensors deployed in the canopies and 2 m above stand floor are sequentially connected to the spectrometer by means of 30-m long fibre optics. During low-level conditions (dawn, overcast sky) the system automatically lengthens the integration time of the spectrometer. About 3 sec per sensor, i.e., 13 min for the total of 264 sensors (worst case) are needed to collect spectral energy data, store them on hard disk and move the channel multiplexer to the next fibre optic position. The detection limit of quartz fibre sensors is 0.2 W/m2; precision and absolute error of radiant flux density are smaller than 3 % and 10 %, respectively. The system, operating since 1999, is derived from a 20-sensor pilot system developed for PAR measurements (PMMA fibre sensor, 400nm to 700 nm). Data achieved with the system serve to determine vertical profiles of wavelength dependent radiation extinction, with special respect to R/FR ratios and to develop a model of spectral radiation distribution in a mature forest stand, prerequisites for the computation of carbon gain of the stand and the evaluation of stand growth models. [source] Influence of Forest Type and Tree Species on Canopy-Dwelling Beetles in Budongo Forest, Uganda,BIOTROPICA, Issue 3 2000Thomas Wagner ABSTRACT Beetles were collected on 64 trees of four species (Cynometra alexandri C. H. Wright, Rinorea beniemis (Welwitsch ex Olivier) Kuntze, Teclea nobilis Delile, and Trichilia rubescens Olivier) in Budongo Forest, Uganda, using an insecticidal fogging technique. Selected tree species were abundant, taxonomically not closely related, and different in the shape of leaves, growth form, and size, with heights between 7 and 35 m. Trees were fogged in an old primary forest stand, in an area of secondary forest where selective logging was performed, and in a swamp forest. Eight conspecific trees per forest type were fogged. A total of 29,736 beetles were collected from all trees that could be assigned to 1433 (morpho)-species; 41.6 percent were singletons and 89.6 percent of species were found with less than ten individuals. Abundant beetle taxa included Latridiidae (N= 4093), Chrysomelidae (3952), Staphylinidae (2931), Apioninae (2621), and Curculionidae (2457). Most species-rich groups were Staphylinidae (N= 196 spp.), Curculionidae (189), and Chrysomelidae (148). Abundance increased in the order: primary < secondary < swamp forest. Due to the relatively high dominance of some species in the secondary forest, species richness increased in the order: secondary < primary < swamp forest. Beta diversity measures and factor analysis showed distinct differences among forest types but higher similarity of beetle communities on different tree species within one forest type. The taxonomic distribution of beetles in the secondary forest was more heterogeneous than in the primary forest. Analyses of the data revealed low host specificity even for phytophagous beetles, underlining the importance of habitat structure and chance effects on the spatial distribution of beetles in the canopy of Budongo Forest. [source] Forest Stand Dynamics and Livestock Grazing in Historical ContextCONSERVATION BIOLOGY, Issue 5 2005MICHAEL M. BORMAN clima; incendio forestal; pastoreo histórico; pino ponderosa; supresión de fuego Abstract:,Livestock grazing has been implicated as a cause of the unhealthy condition of ponderosa pine forest stands in the western United States. An evaluation of livestock grazing impacts on natural resources requires an understanding of the context in which grazing occurred. Context should include timing of grazing, duration of grazing, intensity of grazing, and species of grazing animal. Historical context, when and under what circumstances grazing occurred, is also an important consideration. Many of the dense ponderosa pine forests and less-than-desirable forest health conditions of today originated in the early 1900s. Contributing to that condition was a convergence of fire, climate, and grazing factors that were unique to that time. During that time period, substantially fewer low-intensity ground fires (those that thinned dense stands of younger trees) were the result of reduced fine fuels (grazing), a substantial reduction in fires initiated by Native Americans, and effective fire-suppression programs. Especially favorable climate years for tree reproduction occurred during the early 1900s. Exceptionally heavy, unregulated, unmanaged grazing by very large numbers of horses, cattle, and sheep during the late nineteenth and early twentieth centuries occurred in most of the U.S. West and beginning earlier in portions of the Southwest. Today, livestock numbers on public lands are substantially lower than they were during this time and grazing is generally managed. Grazing then and grazing now are not the same. Resumen:,El pastoreo de ganado ha sido implicado como una causa de la mala salud de los bosques de pino ponderosa en el occidente de Estados Unidos. La evaluación de los impactos del pastoreo sobre los recursos naturales requiere de conocimiento del contexto en que ocurrió el pastoreo. El contexto debe incluir al período de ocurrencia, la duración y la intensidad del pastoreo, así como la especie de animal que pastoreó. El contexto histórico, cuando y bajo que circunstancias ocurrió el pastoreo, también es una consideración importante. Muchos de los bosques densos de pino ponderosa y de las condiciones, menos que deseables, de salud de los bosques actuales se originaron al principio del siglo pasado. Contribuyó a esa condición una convergencia de factores, fuego, clima y pastoreo, que fueron únicos en ese tiempo. Durante ese período, hubo sustancialmente menos incendios superficiales de baja intensidad (que afectaron a grupos densos de árboles más jóvenes) como resultado de la reducción de combustibles finos (pastoreo), una reducción sustancial en los incendios iniciados por Americanos Nativos y programas efectivos de supresión de incendios. Al inicio del siglo pasado hubo años con clima especialmente favorable para la reproducción de árboles. Al final del siglo diecinueve y comienzo del veinte hubo pastoreo no regulado ni manejado, excepcionalmente intensivo, por una gran cantidad de caballos, reses y ovejas en la mayor parte del oeste de E.U.A. y aun antes en porciones del suroeste. En la actualidad, el número de semovientes en terrenos públicos es sustancialmente menor al de ese tiempo, y el pastoreo generalmente es manejado. El pastoreo entonces y el pastoreo ahora no son lo mismo. [source] Scale dependence of effective specialization: its analysis and implications for estimates of global insect species richnessDIVERSITY AND DISTRIBUTIONS, Issue 1 2007Jon C. Gering ABSTRACT Estimates of global insect species richness are sometimes based on effective specialization, a calculation used to estimate the number of insect species that is restricted to a particular tree species. Yet it is not clear how effective specialization is influenced by spatial scale or characteristics of the insect community itself (e.g. species richness). We investigated scale dependence and community predictors of effective specialization using 15,907 beetles (583 species) collected by insecticide fogging from the crowns of 96 trees (including 32 Quercus trees) located in Ohio and Indiana. Trees were distributed across 24 forest stands (,1 ha) nested within six sites (,10,100 km2) and two ecoregions (> 1000 km2). Using paired-sample randomization tests, we found that effective specialization (fk) exhibited negative scale-dependence in early (May,June 2000) and late (August,September 2000) sampling periods. Our average effective specialization (F) values , those that are comparable to Erwin's (1982) estimates , ranged from 19% to 97%, and increased as spatial scale decreased. We also found that beetle species richness and the number of shared beetle species across host trees were significant and consistent negative predictors of F. This shows that increases in spatial scale, species richness, and the number of trees (and/or tree species) all coincide with decreases in effective specialization. Collectively, our results indicate that estimates of global insect species richness based on effective specialization at a single spatial scale are overestimating the magnitude of global insect species richness. We propose that scale dependence should be promoted to a central concept in the research program on global estimates of species richness. [source] Effects of forest harvesting on the occurrence of landslides and debris flows in steep terrain of central JapanEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2008Fumitoshi Imaizumi Abstract Landslides and debris flows associated with forest harvesting can cause much destruction and the influence of the timing of harvesting on these mass wasting processes therefore needs to be assessed in order to protect aquatic ecosystems and develop improved strategies for disaster prevention. We examined the effects of forest harvesting on the frequency of landslides and debris flows in the Sanko catchment (central Japan) using nine aerial photo periods covering 1964 to 2003. These photographs showed a mosaic of different forest ages attributable to the rotational management in this area since 1912. Geology and slope gradient are rather uniformly distributed in the Sanko catchment, facilitating assessment of forest harvesting effects on mass wasting without complication of other factors. Trends of new landslides and debris flows correspond to changes in slope stability explained by root strength decay and recovery; the direct impact of clearcutting on landslide occurrence was greatest in forest stands that were clearcut 1 to 10 yr earlier with progressively lesser impacts continuing up to 25 yr after harvesting. Sediment supply rate from landslides in forests clearcut 1 to 10 yr earlier was about 10-fold higher than in control sites. Total landslide volume in forest stands clearcut 0 to 25 yr earlier was 5·8 × 103 m3 km,2 compared with 1·3 × 103 m3 km,2 in clearcuts >25 yr, indicating a fourfold increase compared with control sites during the period when harvesting affected slope stability. Because landslide scars continue to produce sediment after initial failure, sediment supply from landslides continues for 45 yr in the Sanko catchment. To estimate the effect of forest harvesting and subsequent regeneration on the occurrence of mass wasting in other regions, changes in root strength caused by decay and recovery of roots should be investigated for various species and environmental conditions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effects of landscape composition and substrate availability on saproxylic beetles in boreal forests: a study using experimental logs for monitoring assemblagesECOGRAPHY, Issue 2 2006Heloise Gibb Intensive forestry practises in the Swedish landscape have led to the loss and fragmentation of stable old-growth habitats. We investigated relationships between landscape composition at multiple scales and the composition of saproxylic beetle assemblages in nine clear-cut, mature managed and old-growth spruce-dominated forest stands in the central boreal zone of Sweden. We set out fresh spruce and birch logs and created spruce snags in 2001,2002 to experimentally test the effects of coarse woody debris (CWD) type and forest management on the composition of early and late successional, and red-listed saproxylic beetle assemblages. We examined effects of CWD availability at 100 m, and landscape composition at 1 and 10 km on saproxylic beetle abundances. Additionally, we tested whether assemblage similarity decreased with increasing distance between sites. We collected beetles from the experimental logs using eclector and window traps in four periods during 2003. CWD was measured and landscape composition data was obtained from maps of remotely sensed data. The composition of saproxylic beetles differed among different CWD substrates and between clear-cuts and the older stand types, however differences between mature managed and old-growth forests were significant only for red-listed species. Assemblage similarities for red-listed species on clear-cuts were more different at greater distances apart, indicating that they have more localised distributions. CWD availability within 100 m of the study sites was rarely important in determining the abundance of species, suggesting that early successional saproxylic beetles can disperse further than this distance. At a larger scale, a large area of suitable stand types within both 1 and 10 km resulted in greater abundances in the study sites for several common and habitat-specific species. The availability of suitable habitat at scales of 1,10 km is thus likely to be important in the survival of many saproxylic species in forestry-fragmented areas. [source] Spatial analysis of an invasion front of Acer platanoides: dynamic inferences from static dataECOGRAPHY, Issue 3 2005Wei Fang It is an open question whether the invading tree species Acer platanoides is invading and displacing native trees within pre-existing forest stands, or merely preferentially occupying new stands of secondary forest growth at the edges of existing forests. Several threads of spatial pattern analyses were used to assess the invasibility of A. platanoides, and to link the invasion to the structure of a plant community in the deciduous forest of the northeastern United States. The analyses were based on maps of a contiguous 100×50 m area along an A. platanoides infestation gradient. The distribution of A. platanoides was highly aggregated and the population importance value increased from 28.1 to 38.5% according to mortality estimated from standing dead trees, while the distribution of native tree species was close to random and importance value of Quercus spp. decreased from 33.4 to 26.9% over time. The size distributions of each tree species across distance indicated that A. platanoides was progressively invading the interior of the forest while the native species (including A. rubrum) were not spreading back towards the A. platanoides monospecific patch. The null hypothesis of no invasibility was rejected based on quantile regressions. There were negative correlations between A. platanoides density and the densities of native species in different functional groups, and negative correlation of A. platanoides density and the species diversity in forest understory. The null hypothesis that A. platanoides invasion did not suppress native trees or understory was rejected based on Dutilleul's modified t-test for correlation, consistent with experimental results in the same study site. The combination of multiple spatial analyses of static data can be used to infer historical dynamical processes that shape a plant community structure. The concept of "envelop effects" was discussed and further developed. [source] Long-term succession in a Danish temperate deciduous forestECOGRAPHY, Issue 2 2005Richard H. W. Bradshaw Forest successional trajectories covering the last 2000 yr from a mixed deciduous forest in Denmark show a gradual shift in dominance from Tilia cordata to Fagus sylvatica and a recent increase in total forest basal area since direct management ceased in 1948. The successions are reconstructed by combining a fifty-year record of direct tree observations with local pollen diagrams from Draved Forest, Denmark. Five of the seven successions record a heathland phase of Viking Age dating from 830 AD. The anthropogenic influence is considerable throughout the period of study even though Draved contains some of the most pristine forest stands in Denmark. Anthropogenic influence including felling masks the underlying natural dynamics, with the least disturbed sites showing the smallest compositional change. Some effects of former management, such as loss of Tilia cordata dominance, are irreversible. Artificial disturbance, particularly drainage, has accelerated and amplified the shift towards Fagus dominance that would have occurred on a smaller scale and at a slower rate in the absence of human intervention. [source] Seedling dynamics of shrubs in a fully closed temperate forest: greater than expectedECOGRAPHY, Issue 5 2004N. A. Laskurain Shrub seedling emergences were studied in a beech-birch forest in the Basque Country (Spain). During four years (1998,2001) all emerging shrubs were tagged and regularly monitored in 198 1 m2 plots. Seedling emergence was intense during the entire study period and primarily occurred in early spring. Emerging seedlings mainly belonged to Hedera helix, Rubus gr. glandulosus and several heath species (including genera Erica, Calluna and Daboecia). In contrast, some dominant species components of the shrub layer (Vaccinium myrtillus and Lonicera periclymenum) showed no emergences. While small seeded species (heath species and Rubus) showed clear microsite preferences, avoiding litter for emergence, that was not the case of large seeded Hedera helix. Strict microsite requirements appear clearly associated with having seed bank, suggesting that this trait may allow these species to select favourable microenvironment prior to germination. Average life varied largely among the different taxa. It was very low for Rubus (7.4 months) and heath (4.9), and high for Hedera seedlings (23.1). Final survival was extremely low in the case of small-seeded species. Survival of Hedera seedlings was high, although their growth was very low, suggesting the existence of a conspicuous seedling bank. Our results clearly show that several shrubs species have dramatic seedling dynamics in full closed forest stands. Small seeded species preferentially emerge on bare surfaces in early spring from the soil seed banks. On the other hand, Hedera seedlings are able to emerge on litter and maintain a conspicuous seedling bank based on an efficient dispersal capability. [source] Persistence of a biocontrol strain of Phlebiopsis gigantea in conifer stumps and its effects on within-species genetic diversityFOREST PATHOLOGY, Issue 5 2001E. J. Vainio Fungal isolations and genetic fingerprinting were used to determine whether Phlebiopsis gigantea stump treatment against Heterobasidion annosum sl. using a single genotype (Rotstop) would affect the genetic diversity of P. gigantea populations. The survival time of P. gigantea was longer in Norway spruce (Picea abies) stumps compared to Scots pine (Pinus sylvestris) as no isolates were obtained from pine stumps 6 years after treatment, whereas in about half of the spruce stumps the fungus was still present. The usage of Rotstop did not seem to increase the occurrence of the fungus 5 years after the treatment in fresh (1-year-old) untreated stumps within the same forest stands. All the isolates from the 6-year-old treated spruce stumps were identical in genotype with the Rotstop-strain, whereas all isolates from the fresh untreated spruce and pine stumps differed from it. Within the treated pine stand, the biocontrol usage seemed to have caused a slight reduction in genetic markers not related to Rotstop, but there were no statistically significant differences between the marker frequencies and the local natural population. Thus, Rotstop is not likely to cause any immediate threat to the genetic diversity of P. gigantea. Persistance dans les souches de conifères d'un génotype de Phlebiopsis gigantea utilisée en lutte biologique, et effets sur la diversité génétique de l'espèce L'isolement et l'empreinte génétique ont été utilisés pour savoir si le traitement de souches contre Heterobasidion annosum avec un seul génotype de Phlebiopsis gigantea (Rotstop) peut affecter la diversité génétique des populations de P. gigantea. La durée de survie de P. gigantea a été plus longue dans les souches de Picea abies que dans celles de Pinus sylvestris. Chez celles-ci, aucun isolat n'a été obtenu six ans après le traitement alors que chez environ la moitié des souches d'épicéa le champignon était encore présent. Dans les mêmes peuplements, cinq ans après l'application du Rotstop, l'incidence du champignon ne semblait pas avoir augmenté chez les souches fraîches non traitées, âgées de un an. Tous les isolats obtenus à partir des souches traitées six ans auparavant avaient le même génotype que l'isolat du Rotstop, alors que tous ceux issus de souches fraîches non traitées d'épicéa et de pin étaient différents. Chez le peuplement de pins, le traitement biologique semblait avoir causé une légère réduction des marqueurs génétiques non liés au Rotstop, mais leur fréquence n'était pas statistiquement différente de celle de la population naturelle locale. Ainsi, il apparaît peu probable que le Rotstop soit une menace immédiate pour la diversité génétique du P. gigantea. Persistenz eines Phlebiopsis gigantea -Isolates in Koniferenstümpfen und seine Auswirkungen auf die intraspezifische genetische Diversität Mit Isolierungen und genetischem Fingerprinting wurde untersucht, ob eine Stumpfbehandlung mit einem einzelnen Genotyp von Phlebiopsis gigantea (Rotstop) gegen Heterobasidion annosum sl. die genetische Diversität von P. gigantea -Populationen beeinträchtigen könnte. P. giganteaüberlebte auf Stümpfen von Picea abies länger als auf solchen von Pinus sylvestris. Auf Kiefernstümpfen konnte der Pilz sechs Jahre nach der Behandlung nicht mehr nachgewiesen werden, während er auf 50% der Fichtenstümpfe noch vorhanden war. Eine Rotstop-Anwendung 5 Jahre zuvor hatte offenbar keinen Einfluss auf das Vorkommen von P. gigantea in frischen (einjährigen) unbehandelten Stümpfen im gleichen Bestand. Alle Isolate von den sechs Jahre alten behandelten Fichtenstümpfen hatten den gleichen Genotyp wie das Rotstop-Isolat, während alle Isolate von den frischen (unbehandelten) Fichten-und Kiefernstümpfen anderen Genotypen angehörten. In dem behandelten Kiefernbestand war die Frequenz der nicht mit dem Rotstop-Isolat assoziierten genetischen Marker etwas verringert, der Unterschied zur lokalen natürlichen Population war aber statistisch nicht signifikant. Die Anwendung von Rotstop dürfte somit keine kurzfristige Bedrohung der genetischen Diversität von P. gigantea darstellen. [source] Nitrate leaching from three afforestation chronosequences on former arable land in DenmarkGLOBAL CHANGE BIOLOGY, Issue 6 2007KARIN HANSEN Abstract In regions dominated by agricultural activities, nitrogen (N) is recognized as a major pollutant in aquatic environments. In north-western Europe, afforestation of agricultural land is part of a strategy to improve water quality. In Denmark, former arable land has been afforested during the past 40,50 years. This study evaluated the effect of afforestation of former arable land on nitrate leaching, based on three afforestation chronosequences. Precipitation, canopy throughfall and soil water were collected and soil moisture was monitored at two Danish locations, Vestskoven (nutrient-rich, medium deposition) and Gejlvang (nutrient-poor, high deposition). Afforestation was performed using Norway spruce [Picea abies (Karst.) L.] and common oak (Quercus robur L.) at Vestskoven and Norway spruce at Gejlvang. The results suggest that afforestation of former arable land initially leads to lower nitrate leaching than that occurring under the former agricultural land use, and largely below the standard of 50 mg NO,3 L,1 for groundwater to be utilized as drinking water. Nitrate concentrations became almost negligible in forest stands of 5,20 years of age. However, after canopy closure (>20 years) nitrate concentrations below the root zone and nitrate leaching tended to increase. This was attributed to increased N deposition with increasing canopy development and decreased N demand once the most N-rich biomass compartments had been built up. Nitrate leaching started to increase at a throughfall deposition level of about 10 kg N ha,1 yr,1. Compared with nutrient-poor sandy soils, nutrient-rich clayey soils appeared more vulnerable to disturbance of the N cycle and to increased N deposition, leading to N saturation and enhanced nitrate leaching. In approximately the first 35 years after afforestation, nitrate leaching below the root zone was generally higher below oak than below Norway spruce. [source] Partitioning sources of soil respiration in boreal black spruce forest using radiocarbonGLOBAL CHANGE BIOLOGY, Issue 2 2006Edward A.G. Schuur Abstract Separating ecosystem and soil respiration into autotrophic and heterotrophic component sources is necessary for understanding how the net ecosystem exchange of carbon (C) will respond to current and future changes in climate and vegetation. Here, we use an isotope mass balance method based on radiocarbon to partition respiration sources in three mature black spruce forest stands in Alaska. Radiocarbon (,14C) signatures of respired C reflect the age of substrate C and can be used to differentiate source pools within ecosystems. Recently-fixed C that fuels plant or microbial metabolism has ,14C values close to that of current atmospheric CO2, while C respired from litter and soil organic matter decomposition will reflect the longer residence time of C in plant and soil C pools. Contrary to our expectations, the ,14C of C respired by recently excised black spruce roots averaged 14, greater than expected for recently fixed photosynthetic products, indicating that some portion of the C fueling root metabolism was derived from C storage pools with turnover times of at least several years. The ,14C values of C respired by heterotrophs in laboratory incubations of soil organic matter averaged 60, higher than the contemporary atmosphere ,14CO2, indicating that the major contributors to decomposition are derived from a combination of sources consistent with a mean residence time of up to a decade. Comparing autotrophic and heterotrophic ,14C end members with measurements of the ,14C of total soil respiration, we calculated that 47,63% of soil CO2 emissions were derived from heterotrophic respiration across all three sites. Our limited temporal sampling also observed no significant differences in the partitioning of soil respiration in the early season compared with the late season. Future work is needed to address the reasons for high ,14C values in root respiration and issues of whether this method fully captures the contribution of rhizosphere respiration. [source] Comparison of structure and biodiversity in the Rajhenav virgin forest remnant and managed forest in the Dinaric region of SloveniaGLOBAL ECOLOGY, Issue 3 2000Andrej Boncina Abstract Comparisons are made between a virgin forest remnant (primeval forest) and a lightly managed (near-to-nature) forest with regard to horizontal forest structures, the structure of forest stands, and the diversity of plant and bird species. In the virgin forest remnant the proportion of canopy gaps is smaller, there are no stands in the developmental phase of a pole stand (10 < cm d.b.h. < 30 cm), and both the growing stock and the proportion of less vigorous trees are considerably greater. In addition, there is a higher percentage of dead trees, a smaller proportion of minor tree species and a considerably lower diversity of plants. The diversity of bird species is similar for each forest type, but rare bird species are confined to the virgin forest remnant. The biological differences between the two types of forest have led to changes in the physical site conditions. The results of the research are valuable in assessing the consequences of near-to-nature forest management. [source] Biomass allocation and leaf life span in relation to light interception by tropical forest plants during the first years of secondary successionJOURNAL OF ECOLOGY, Issue 6 2008N. Galia Selaya Summary 1We related above-ground biomass allocation to light interception by trees and lianas growing in three tropical rain forest stands that were 0.5, 2 and 3-year-old regeneration stages after slash and burn agriculture. 2Stem height and diameter, leaf angle, the vertical distribution of total above-ground biomass and leaf longevity were measured in individuals of three short-lived pioneers (SLP), four later successional species (LS) and three lianas (L). Daily light capture per individual (,d) was calculated with a canopy model. Mean daily light interception per unit leaf area (,area), leaf mass (,leaf mass) and above-ground mass (,mass) were used as measures of instantaneous efficiency of biomass use for light capture. 3With increasing stand age, vegetation height and leaf area index increased while light at the forest floor declined from 34 to 5%. The SLP, Trema micanthra and Ochroma pyramidale, dominated the canopy early in succession and became three times taller than the other species. SLP had lower leaf mass fractions and leaf area ratios than the other groups and this difference increased with stand age. 4Over time, the SLP intercepted increasingly more light per unit leaf mass than the other species. Lianas, which in the earliest stage were self-supporting and started climbing later on, gradually became taller at a given mass and diameter than the trees. Yet, they were not more efficient than trees in light interception. 5SLP had at least three-fold shorter leaf life spans than LS and lianas. Consequently, total light interception calculated over the mean life span of leaves (,leaf mass total = ,area × SLAdeath leaves× leaf longevity) was considerably lower for the SLP than for the other groups. 6Synthesis. We suggest that early dominance in secondary forest is associated with a high rate of leaf turnover which in turn causes inefficient long-term use of biomass for light capture, whereas persistence in the shade is associated with long leaf life spans. This analysis shows how inherent tradeoffs in crown and leaf traits drive long-term competition for light, and it presents a conceptual tool to explain why early dominants are not also the long-term dominants. [source] The millennial dynamics of a boreal forest stand from buried treesJOURNAL OF ECOLOGY, Issue 3 2004DOMINIQUE ARSENEAULT Summary 1We reconstructed the dynamics of a black spruce (Picea mariana) and jack pine (Pinus banksiana) forest stand in northern Québec using a continuous, 5200-year-long sequence of stem remains buried in adjacent peatland. Simulations of recruitment of such remains provided guidelines for inferring past ecosystem structure and composition at the stand scale. 2Compared with the late Holocene (4650,0 cal. year BP (CYBP)), the mid Holocene (5200,4650 CYBP) period was characterized by faster tree growth, larger stems and higher stem density, indicating higher forest productivity in association with a milder climate. 3The presence of stem remains of both species from 17 out of 20 contiguous 250-year time intervals suggests that the spruce-pine stand exhibited high compositional stability, with both species regenerating after fire from canopy-stored seed banks. 4Relative species abundance closely followed the duration of past fire intervals deduced from the number of tree rings in buried conifers. Time periods of long (4650,3950, 3400,1850 and 250,0 CYBP) and short fire intervals (4950,4650, 3950,3400 and 1850,250 CYBP) were associated, respectively, with decreasing and increasing pine abundance, probably reflecting faster juvenile growth, lower shade tolerance, earlier sexual maturity and shorter longevity in jack pine compared with black spruce. 5We conclude that both climate change and climate-induced fire disturbance have been driving long-term ecosystem dynamics. Our field evidence supports the idea that interactions between disturbances and the life-history traits of species modulate the impact of climate change at the scale of forest stands. At the same time, disturbances may result in long-term stability of disturbance-adapted ecosystems. [source] Soil N dynamics in relation to leaf litter quality and soil fertility in north-western Patagonian forestsJOURNAL OF ECOLOGY, Issue 2 2003Patricia Satti Summary 1We examined the relationships among soil N dynamics, soil chemistry and leaf litter quality in 28 forest stands dominated by conifers, woody broad-leaf deciduous species or broad-leaf evergreens. Potential net N mineralization, net nitrification and microbial biomass N were used as indicators of soil N dynamics; pH, organic C, total N, exchangeable cations and extractable P as indicators of soil chemistry and N concentration, lignin concentration, C : N ratio and lignin : N ratio in senescent leaves as indicators of leaf litter quality. N dynamics were assessed in two consecutive years with contrasting precipitation. 2Net N mineralization was lower in stands of the three conifers and one of three broad-leaf evergreen species than in stands of the other six broad-leaf species (40,77 vs. 87,250 mg N kg,1 after 16-week incubations) and higher in the wetter year. 3The proportion of N nitrified was high beneath most species regardless of mineralization rates, soil N fertility and leaf litter quality, and was significantly higher for the wetter year. Ammonium was the predominant form of N in three sites affected by seasonal waterlogging and in two sites the predominant form changed from ammonium in the drier year to nitrate during the wetter year, probably due to differences in soil texture affecting soil moisture. 4Net N mineralization was linearly related to microbial biomass N, implying that the microbial activity per biomass unit was quite similar beneath all species. Constant microbial biomass during the wetter year suggested that as mineralization/nitrification increased, there was a higher potential risk of N losses. 5Although the litter lignin : N ratio allowed differentiation of soil N dynamics between broad-leaf species and conifers, its constant value (23,28) in all broad-leaf species made it a poor predictor of the differences found within this group. Across all sites and between broad-leaf species, soil N dynamics were best explained by a combination of leaf litter lignin and soil chemistry indicators, particularly soil total N for net N mineralization and net nitrification, and soil organic C for microbial biomass N. [source] Fine-scale environmental variation and structure of understorey plant communities in two old-growth pine forestsJOURNAL OF ECOLOGY, Issue 2 2003Lee E. Frelich Summary 1Although it is well established that nitrogen and light play major roles in structuring plant communities across the landscape, it is not as clear how they structure communities within forest stands. Virtually nothing is known about within-stand structure of understorey communities of herbs and small shrubs in near-boreal forests. 2We tested the hypothesis that fine-scale (5,20 m) variability in N and light structure forest-floor plant communities in two old-growth mixed Pinus resinosa and Pinus strobus forests in north-eastern Minnesota, USA. 3In each forest, all trees > 1.4 m tall were mapped on a 0.75,1.0 ha area. A grid of subplots 5,10 m apart was established (total n = 147), and N mineralization (µg g,1 soil day,1), soil depth (cm), light (% canopy openness), and percentage cover of all herbs and small shrubs were measured on each subplot. 4Cluster analysis showed that the dominant understorey species fall into three groups. Group 1 is unrelated to N and light, and is negatively associated with a midstorey of the small tree Acer rubrum and the most abundant tall shrub Corylus cornuta. Group 2 reaches maximum abundance in places (mostly gaps) with relatively high light, but is unrelated to within-stand variation in N availability. Group 3 consists of a single species, Aster macrophyllus, and reaches maximum abundance in areas with low N availability and low abundance of Corylus, but higher than average abundance of P. strobus and Betula papyrifera overstorey trees. 5N and light have a moderate influence on understorey plant community structure. The plant species do arrange themselves along N and light gradients, but the gradients are likely to be too narrow to allow the degree of differentiation seen at the landscape level. Spatial patterning of the species groups is probably influenced by other factors, including disturbance history, chance and neighbourhood effects such as clonal reproduction. [source] Forest change and stream fish habitat: lessons from ,Olde' and New EnglandJOURNAL OF FISH BIOLOGY, Issue 2005K. H. Nislow The North Atlantic region has a long history of land use change that has influenced and will continue to influence stream ecosystems and fisheries production. This paper explores and compares the potential consequences of changes in forest cover for fish production in upland, coldwater stream environments in New England, U.S.A. and the British Isles, two regions which share important similarities with respect to overall physical, biotic and socio-economic setting. Both regions were extensively deforested and essentially no extensive old-growth forest stands remain. In New England, recovering forests, consisting almost entirely of naturally-regenerated native species, now cover >60% of the landscape. Associated with this large-scale reforestation, open landscapes, common in the 19th and first half the 20th century, are currently rare and declining in this region. In the British Isles, forests still cover <20% of the landscape, and existing forests largely consist of exotic conifer plantations stocked at high stand densities and harvested at frequent rotations. While forest restoration and conservation is frequently recommended as a fisheries habitat conservation and restoration tool, consideration of the way in which forests affect essential aspects of fish habitat suggests that response of upland stream fish to landscape change is inherently complex. Under certain environmental settings and reforestation practices, conversion of open landscapes to young-mature forests can negatively impact fish production. Further, the effects of re-establishing old-growth forests are difficult to predict for the two regions (due to the current absence of such landscapes), and are likely to depend strongly on the extent to which critical ecosystem attributes (large-scale disturbances, fish migrations, keystone species, large woody debris recruitment) are allowed to be re-established. Understanding these context-dependencies is critical for predicting fish responses, and should help managers set realistic conservation, management and restoration goals. Management may best be served by promoting a diversity of land cover types in a way that emulates natural landscape and disturbance dynamics. This goal presents very different challenges in New England and the British Isles due to differences in current and predicted land use trajectories, along with differences in ecological context and public perception. [source] Chernozem,Soil of the Year 2005JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2005Manfred Altermann Abstract The proclamation of the "Soil of the Year" was made for the first time in Germany in 2005 on occasion of the World Soil Day. Chernozems were selected for this purpose. In this paper an overview of these groups of soils is given. Chernozems are concentrated in the drought region of Central Germany. A standard profile from the core area of Chernozems developed from loess is presented with comprehensive laboratory analysis. Chernozems developed primarily upon carbonatic loess substrates under summer-dry climatic conditions in an open park-like landscape with isolated forest stands. The development of Chernozems began as early as the late glacial period, and they were fully developed by the Atlantikum age. The far-reaching, uniformly thick humus horizons indicate substrate differences in the loess cover, which are partly the result of bioturbation. Within Germany, Chernozems and Chernozem-like soils make up approx. 3% of the surface area and 5% (approx. 11,000 km2) of the arable land. The results of the Static Fertilization Experiment in Bad Lauchstädt, founded in 1902, clarify the high value of Chernozem for biomass production and the environment. Each loss due to erosion or decrease in surface area reduces the fulfillment of soil ecological functions of the soils and is comparable to a loss of animal and plant species. Therefore, soil scientists and the results of soil research must be more comprehensively implemented for soil preservation, protection, and politics. For acceptance of these goals among the general public and the political-decision makers, the campaign "Soil of the Year" should give some thought-provoking impulses. Schwarzerde , Boden des Jahres 2005 Anlässlich des Weltbodentages wurde in Deutschland für 2005 mit der Schwarzerde erstmalig ein ,Boden des Jahres" proklamiert. Damit soll in der Bevölkerung und bei politischen Entscheidungsträgern ein stärkeres Bewusstsein für den Boden und ein höheres Engagement für den Bodenschutz angeregt werden. Im Beitrag wird ein Überblick über diese Bodengruppe gegeben und ein Standardprofil aus dem Kerngebiet der Schwarzerden aus Löss (Mitteldeutsches Trockengebiet) mit umfassenden Laboranalysen exemplarisch präsentiert. Schwarzerden entwickelten sich vorwiegend auf kalkreichen Lössen unter sommertrockenen Klimabedingungen in einer offenen parkähnlichen Landschaft mit Waldinseln. Die Entstehung der Schwarzerden setzte bereits im Spätglazial ein, und im Atlantikum waren sie voll entwickelt. Die weiträumig gleiche Mächtigkeit der Humushorizonte zeichnet primäre Substratunterschiede in der Lössdecke nach; sie sind nicht nur das Ergebnis einer Bioturbation. In Deutschland nehmen die Schwarzerden und schwarzerdeähnlichen Böden etwa 3 % der Bodenfläche bzw. 5 % (ca. 11.000 km2) der landwirtschaftlichen Nutzfläche ein. Die Ergebnisse des seit 1902 bestehenden Statischen Düngungsversuchs Bad Lauchstädt verdeutlichen den hohen Wert der Schwarzerden für Biomasseproduktion und Umwelt. Jeder Verlust durch Erosion oder Flächenentzug mindert die Erfüllung ökologischer Funktionen der Böden und ist dem Artenverlust von Tieren und Pflanzen gleichzustellen. In der Bodenpolitik müssen deshalb die Ergebnisse der Bodenforschung zum Erhalt und Schutz unserer Böden umfassender als bisher umgesetzt und Bodenwissenschaftler stärker in politische Entscheidungen eingebunden werden. Für die Akzeptanz und Umsetzung dieser Ziele in der Öffentlichkeit soll der ,Boden des Jahres" Impulse geben. [source] | |||||||||||||||||||||||||||||||