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Northern Hardwood Forest (northern + hardwood_forest)
Selected AbstractsSusceptibility of a Northern Hardwood Forest to Exotic Earthworm InvasionCONSERVATION BIOLOGY, Issue 4 2005MICHAEL J. GUNDALE Acer saccharum; Bosque Nacional Ottawa; lombrices invasoras; Sylvania Wilderness Area; uso del suelo Abstract:,Numerous exotic earthworm species are colonizing northern hardwood forests of North America, where no native earthworms exist. Upon invasion, earthworms have been shown to alter the surface soil environment and plant populations and communities. We sought to identify land-use factors in the Ottawa National Forest (ONF), Michigan (U.S.A.), that contribute to earthworm invasion in forest dominated by sugar maple (Acer saccharum Marsh.) so that the susceptibility to additional colonization could be evaluated. We sampled earthworm communities in Sylvania Wilderness Area, a unique old-growth hardwood forest, and nonwilderness sites influenced by recreational fishing, recent timber harvesting, or roads. All the nonwilderness sites contained one to five species of exotic earthworms. In contrast, only 50% of wilderness sites contained exotic earthworms, all of a single species. Nonwilderness sites also had thinner litter and duff layers, higher soil C and N content, and higher nitrogen mineralization potentials than Sylvania sites. Two central differences between Sylvania and nonwilderness sites were that all nonwilderness sites were in close contact with roads and had a history of timber harvest, whereas these factors were not present in Sylvania Wilderness Area. Using average rates of colonization, we constructed two geographic information system models to estimate the percentage of sugar maple on the ONF falling within a theoretical 100-year invasion distance of roads and of second-growth sugar maple as relative indices of susceptibility to invasion. Both models indicated high susceptibility to invasion, with 91.7% and 98.9% of sugar maple habitat falling within a theoretical 100-year invasion distance of roads or historical harvests, respectively. Resumen:,Numerosas especies de lombrices exóticas están colonizando los bosques boreales, en los que previamente no existían lombrices terrestres nativas. Por encima de la invasión, se ha demostrado que las lombrices alteran el ambiente superficial del suelo, así como a las comunidades y poblaciones de plantas. Tratamos de identificar factores de uso del suelo en el Bosque Nacional Ottawa (BNO), Michigan, E. U. A., que contribuyen a la invasión de lombrices en bosques dominados por arces (Acer saccharum Marsh.), para poder evaluar la susceptibilidad a futuras invasiones. Muestreamos comunidades de lombrices en Sylvania Wilderness Area, un bosque maduro único, y en sitios no silvestres influenciados por pesca deportiva, cosecha reciente de madera o caminos. Todas las áreas no silvestres contenían 1 - 5 especies de lombrices exóticas. En contraste, solo 50% de los sitios silvestres contenían lombrices exóticas, todas de una sola especie. Los sitios no silvestres también tenían capas de hojarasca y de mantillo más delgadas, mayor contenido de C y N del suelo y mayor potencial de mineralización del nitrógeno que los sitios en Sylvania. Dos diferencias centrales entre Sylvania y los sitios no silvestres fueron que estos estaban en contacto cercano con caminos y tenían una historia de cosecha de madera, mientras que estos factores no estuvieron presentes en Sylvania Wilderness Area. Utilizando tasas promedio de colonización, construimos dos modelos de sistemas de información geográfica para estimar el porcentaje de arces en el BNO que queda a una distancia teórica de invasión en 100 años; con caminos y arce de crecimiento secundario como índices relativos de susceptibilidad a la invasión. Ambos modelos indicaron alta susceptibilidad a la invasión, con 91.7% y 98.9% del hábitat de arce dentro de la distancia teórica de invasión en 100 años o con cosechas históricas, respectivamente. [source] Comparison of two plant functional approaches to evaluate natural restoration along an old-field , deciduous forest chronosequenceJOURNAL OF VEGETATION SCIENCE, Issue 2 2009Isabelle Aubin Abstract Question: Are direct and indirect trait-based approaches similar in their usefulness to synthesize species responses to successional stages? Location: Northern hardwood forests, Québec, Canada (45°01,,45°08,N; 73°58,,74°21,W). Methods: Two different trait-based approaches were used to relate plant functional traits to succession on an old-field , deciduous forest chronosequence: (i) a frequently used approach based on co-occurrence of traits (emergent groups), and (ii) a new version of a direct functional approach at the trait level (the fourth-corner method). Additionally, we selected two different cut-off levels for the herb subset of the emergent group classification in order to test its robustness and ecological relevance. Results: Clear patterns of trait associations with stand developmental stages emerged from both the emergent group and the direct approach at the trait level. However, the emergent group classification was found to hide some trait-level differences such as a shift in seed size, light requirement and plant form along the chronosequence. Contrasting results were obtained for the seven or nine group classification of the herbaceous subset, illustrating how critical is the number of groups for emergent group classification. Conclusion: The simultaneous use of two different trait-based approaches provided a robust and comprehensive characterization of vegetation responses in the old-field , deciduous forest chronosequence. It also underlines the different goals as well as the limitations and benefits of these two approaches. Both approaches indicated that abandoned pastures of the northern hardwood biome have good potential for natural recovery. Conversion of these lands to other functions may lead to irremediable loss of biodiversity. [source] Environmental control of fine root dynamics in a northern hardwood forestGLOBAL CHANGE BIOLOGY, Issue 5 2003GERALDINE L. TIERNEY Abstract Understanding how exogenous and endogenous factors control the distribution, production and mortality of fine roots is fundamental to assessing the implications of global change, yet our knowledge of control over fine root dynamics remains rudimentary. To improve understanding of these processes, the present study developed regression relationships between environmental variables and fine root dynamics within a northern hardwood forest in New Hampshire, USA, which was experimentally manipulated with a snow removal treatment. Fine roots (< 1 mm diameter) were observed using minirhizotrons for 2 years in sugar maple and yellow birch stands and analyzed in relation to temperature, water and nutrient availability. Fine root dynamics at this site fluctuated seasonally, with growth and mortality peaking during warmer months. Monthly fine root production was strongly associated with mean monthly air temperature and neither soil moisture nor nutrient availability added additional predictive power to this relationship. This relationship exhibited a seasonal temperature hysteresis, which was altered by snow removal treatment. These results suggest that both exogenous and endogenous cues may be important in controlling fine root growth in this system. Proportional fine root mortality was directly associated with mean monthly soil temperature, and proportional fine root mortality during the over-winter interval was strongly related to whether the soil froze. The strong relationship between fine root production and air temperature reported herein contrasts with findings from some hardwood forest sites and indicates that controls on fine root dynamics vary geographically. Future research must more clearly distinguish between endogenous and exogenous control over fine root dynamics in various ecosystems. [source] Effects of bird predation on arthropod abundance and tree growth across an elevational gradientJOURNAL OF AVIAN BIOLOGY, Issue 4 2010W. Scott Schwenk Considerable uncertainty surrounds the conditions under which birds can cause trophic cascades. In a three-year experiment, we studied the direct and indirect effects of insectivorous birds on arthropod abundance, herbivory, and growth of striped maple Acer pensylvanicum saplings in a northern hardwood forest of central New Hampshire, USA. We manipulated bird predation by erecting exclosures around saplings and directly manipulated herbivory by removing herbivores. We also examined how climate modifies these interactions by replicating the experiment at three locations along an elevational gradient. Effects of bird predation were variable. Overall, mean arthropod biomass was 20% greater on saplings within bird exclosures than on controls (p<0.05). The mean biomass of leaf-chewing herbivores, primarily Lepidoptera larvae, was 25% greater within exclosures but not statistically different from controls. To a lesser degree, mean herbivore damage to foliage within exclosures exceeded that of controls but differences were not significant. We also did not detect significant treatment effects on sapling shoot growth. The high understory vegetation density relative to bird abundance, and low rate of herbivory during the study (mean 5% leaf area removed, controls), may have limited the ability of birds to affect sapling growth. Climate effects operated at multiple scales, resulting in a complex interplay of interactions within the food web. Regional synchrony of climatic conditions resulted in annual fluctuations in herbivore abundance and tree growth that were shared across elevations. At the same time, local environmental variation resulted in site differences in the plant, herbivore, and bird communities. These patterns resulted in a mosaic of top,down strengths across time and space, suggesting an overall pattern of limited effects of birds on plant growth, possibly interspersed with hotspots of trophic cascades. [source] Predators at bird nests in a northern hardwood forest in New HampshireJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2006David I. King ABSTRACT Nest predation is the primary cause of nest failure in most passerine birds, and increases in nest predation associated with anthropogenic habitat disturbance are invoked as explanations for population declines of some bird species. In most cases, however, the identity of the nest predators is not known with certainty. We monitored active bird nests with infrared time-lapse video cameras to determine which nest predators were responsible for depredating bird nests in northern New Hampshire. We monitored 64 nests of 11 bird species during three breeding seasons, and identified seven species of predators during 14 predation events. In addition, we recorded two instances of birds defending nests from predators and, in both cases, these nests were ultimately lost to predation. These results contrast with other studies in terms of the relatively high proportion of nests depredated by raptors and mice, as well as the absence of any predation by snakes. The diverse suite of predators in this and other studies is likely to confound our understanding of patterns of nest predation relative to fragmentation and habitat structure. SINOPSIS La depredación de nidos es la causa principal del fracaso de anidamiento de muchos paserinos. El incremento en depredación ha sido asociado a disturbio antropogénico de habitat y considerado como la causa de la disminución poblacional de muchas especies de aves. En la mayoría de los casos, no se sabe a ciencia cierta quién es el depredador. Monitoreamos nidos activos con cámaras infrarojas de video que tomaban la acción en lapsos para determinar que depredadores eran responsables de la pérdida de nidos en el norte de New Hampshire. A lo largo de tres temporadas reproductivas monitoreamos 64 nidos, pertenecientes a 11 especies, e identificamos siete depredadores en 14 actos de depredación. Además, pudimos grabar dos casos en donde los aves defendieron sus nidos, aunque los nidos eventualmente fueron depredados posteriormente. Estos resultados contrastan con otros estudios en términos de la alta proporción de depredación por parte de rapaces y ratoncitos, y en la ausencia de depredación por parte de culebras. La diversidad de depredadores en este y otros estudios ampliará los conocimiento sobre los patrones de depredación en nidos, y su relación con la fragmentación y la estructura del hábitat. [source] Susceptibility of a Northern Hardwood Forest to Exotic Earthworm InvasionCONSERVATION BIOLOGY, Issue 4 2005MICHAEL J. GUNDALE Acer saccharum; Bosque Nacional Ottawa; lombrices invasoras; Sylvania Wilderness Area; uso del suelo Abstract:,Numerous exotic earthworm species are colonizing northern hardwood forests of North America, where no native earthworms exist. Upon invasion, earthworms have been shown to alter the surface soil environment and plant populations and communities. We sought to identify land-use factors in the Ottawa National Forest (ONF), Michigan (U.S.A.), that contribute to earthworm invasion in forest dominated by sugar maple (Acer saccharum Marsh.) so that the susceptibility to additional colonization could be evaluated. We sampled earthworm communities in Sylvania Wilderness Area, a unique old-growth hardwood forest, and nonwilderness sites influenced by recreational fishing, recent timber harvesting, or roads. All the nonwilderness sites contained one to five species of exotic earthworms. In contrast, only 50% of wilderness sites contained exotic earthworms, all of a single species. Nonwilderness sites also had thinner litter and duff layers, higher soil C and N content, and higher nitrogen mineralization potentials than Sylvania sites. Two central differences between Sylvania and nonwilderness sites were that all nonwilderness sites were in close contact with roads and had a history of timber harvest, whereas these factors were not present in Sylvania Wilderness Area. Using average rates of colonization, we constructed two geographic information system models to estimate the percentage of sugar maple on the ONF falling within a theoretical 100-year invasion distance of roads and of second-growth sugar maple as relative indices of susceptibility to invasion. Both models indicated high susceptibility to invasion, with 91.7% and 98.9% of sugar maple habitat falling within a theoretical 100-year invasion distance of roads or historical harvests, respectively. Resumen:,Numerosas especies de lombrices exóticas están colonizando los bosques boreales, en los que previamente no existían lombrices terrestres nativas. Por encima de la invasión, se ha demostrado que las lombrices alteran el ambiente superficial del suelo, así como a las comunidades y poblaciones de plantas. Tratamos de identificar factores de uso del suelo en el Bosque Nacional Ottawa (BNO), Michigan, E. U. A., que contribuyen a la invasión de lombrices en bosques dominados por arces (Acer saccharum Marsh.), para poder evaluar la susceptibilidad a futuras invasiones. Muestreamos comunidades de lombrices en Sylvania Wilderness Area, un bosque maduro único, y en sitios no silvestres influenciados por pesca deportiva, cosecha reciente de madera o caminos. Todas las áreas no silvestres contenían 1 - 5 especies de lombrices exóticas. En contraste, solo 50% de los sitios silvestres contenían lombrices exóticas, todas de una sola especie. Los sitios no silvestres también tenían capas de hojarasca y de mantillo más delgadas, mayor contenido de C y N del suelo y mayor potencial de mineralización del nitrógeno que los sitios en Sylvania. Dos diferencias centrales entre Sylvania y los sitios no silvestres fueron que estos estaban en contacto cercano con caminos y tenían una historia de cosecha de madera, mientras que estos factores no estuvieron presentes en Sylvania Wilderness Area. Utilizando tasas promedio de colonización, construimos dos modelos de sistemas de información geográfica para estimar el porcentaje de arces en el BNO que queda a una distancia teórica de invasión en 100 años; con caminos y arce de crecimiento secundario como índices relativos de susceptibilidad a la invasión. Ambos modelos indicaron alta susceptibilidad a la invasión, con 91.7% y 98.9% del hábitat de arce dentro de la distancia teórica de invasión en 100 años o con cosechas históricas, respectivamente. [source] Patterns of rhizosphere carbon flux in sugar maple (Acer saccharum) and yellow birch (Betula allegheniensis) saplingsGLOBAL CHANGE BIOLOGY, Issue 6 2005Richard P. Phillips Abstract Despite its importance in the terrestrial C cycle rhizosphere carbon flux (RCF) has rarely been measured for intact root,soil systems. We measured RCF for 8-year-old saplings of sugar maple (Acer saccharum) and yellow birch (Betula allegheniensis) collected from the Hubbard Brook Experimental Forest (HBEF), NH and transplanted into pots with native soil horizons intact. Five saplings of each species were pulse labeled with 13CO2 at ambient CO2 concentrations for 4,6 h, and the 13C label was chased through rhizosphere and bulk soil pools in organic and mineral horizons for 7 days. We hypothesized yellow birch roots would supply more labile C to the rhizosphere than sugar maple roots based on the presumed greater C requirements of ectomycorrhizal roots. We observed appearance of the label in rhizosphere soil of both species within the first 24 h, and a striking difference between species in the timing of 13C release to soil. In sugar maple, peak concentration of the label appeared 1 day after labeling and declined over time whereas in birch the label increased in concentration over the 7-day chase period. The sum of root and rhizomicrobial respiration in the pots was 19% and 26% of total soil respiration in sugar maple and yellow birch, respectively. Our estimate of the total amount of RCF released by roots was 6.9,7.1% of assimilated C in sugar maple and 11.2,13.0% of assimilated C in yellow birch. These fluxes extrapolate to 55,57 and 90,104 g C m,2 yr,1 from sugar maple and yellow birch roots, respectively. These results suggest RCF from both arbuscular mycorrhizal and ectomycorrhizal roots represents a substantial flux of C to soil in northern hardwood forests with important implications for soil microbial activity, nutrient availability and C storage. [source] Performance of the invasive weevil Polydrusus sericeus is influenced by atmospheric CO2 and host speciesAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010Michael L. Hillstrom 1Natural forest systems constitute a major portion of the world's land area, and are subject to the potentially negative effects of both global climate change and invasion by exotic insects. A suite of invasive weevils has become established in the northern hardwood forests of North America. How these insects will respond to increasing CO2 or O3 is unknown. 2The present study examined the effects of elevated atmospheric CO2 and O3 on the invasive weevil Polydrusus sericeus Schaller at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, Wisconsin. A performance assay was conducted in the laboratory during the summer of 2007 using mated pairs of P. sericeus fed a combination of aspen, birch and maple foliage. We recorded leaf area consumption, oviposition and adult longevity. We also conducted visual abundance surveys in the field from 2004 to 2007 on aspen and birch at Aspen FACE. 3Elevated CO2, but not O3, significantly affected P. sericeus performance. Female, but not male, longevity was reduced under elevated CO2. Polydrusus sericeus also produced fewer eggs under elevated CO2 conditions compared with ambient conditions. Adult P. sericeus strongly preferred birch over both aspen and maple, regardless of fumigation treatment. 4The effects of elevated CO2 on P. sericeus populations at Aspen FACE were minimal, and varied among years and host tree species. Polydrusus sericeus abundance was significantly greater on birch than aspen. Over the long term, elevated CO2 may reduce adult female longevity and fecundity of P. sericeus. Further studies are needed to evaluate how this information may scale to ecosystem impacts. [source] | |||||||||||||