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M Tall (m + tall)
Selected AbstractsImpact of Forest Fragmentation on Understory Plant Species Richness in AmazoniaCONSERVATION BIOLOGY, Issue 2 2003Julieta Benítez-Malvido In Central Amazonia, 9 to 19 years after fragmentation, we recorded species richness and net seedling recruitment rate in forest fragments of 1, 10, and 100 ha and in continuous forest. In 1991 all seedlings 5,100 cm tall within permanent 1-m2 plots in fragments and continuous forest were counted and grouped into tree, liana, palm, and herb life-form classes. In 1993 we manually removed all seedlings that were <1 m tall from the permanent plots. Six years and 5 months later ( 1999 ), all new seedlings recruited into the plots were counted, grouped into different life forms, and classified into distinct morphospecies. The species richness of recruited tree, liana, herb, and palm seedlings was lower in forest fragments than in continuous forest, with the 1-ha fragment having the poorest species richness. The total number of recruited individuals was 40% less than that previously present for all life forms, except lianas. Liana recruitment was 7% to 500% higher than the original abundance in the forest fragments and continuous forest. In general, species similarity was higher among fragments than between fragments and continuous forest, with the 1-ha fragment being less similar. Species rank/abundance curves showed that continuous forest species in all life forms tended to disappear in forest fragments, whereas common species in forest fragments were absent from continuous forest. Overall, our results suggest that the life-form composition and structure of the regenerative plant pool in fragments were shifting toward a species-poor seedling community. Losses of understory species diversity, but especially of tree seedlings, threaten the maintenance of rainforest biodiversity and compromise future forest regeneration. Resumen: La fragmentación de las selvas tropicales afecta severamente a a los árboles de gran porte, sin embargo, su efecto sobre otros estadíos y formas de vida de las plantas es poco conocido. En la Amazonia central, de 9 a 19 años después de la fragmentación, se registró la riqueza de especies y la tasa neta de reclutamiento de plántulas en fragmentos de selva de 1, 10, y 100 ha y en selva contínua. En 1991, todas las plántulas de 5,100 cm de altura dentro de cuadrantes permanentes de 1-m2 en los fragmentos y en la selva contínua, fueron contadas y agrupadas en diferentes formas de vida: árboles, lianas, palmas y hierbas. En 1993 se removieron manualmente todas las plántulas <1 m de altura dentro de los cuadrantes. Seis años y cinco meses más tarde (1999) se contaron todas las plántulas reclutadas dentro de los cuadrantes, se agruparon en diferentes formas de vida v se clasificaron en morfoespecies distintivas. La riqueza de especies de plántulas reclutadas en todas las formas de vida fue menor en los fragmentos que en la selva contínua, con el fragmento de 1 ha presentando la menor riqueza de especies. El número total de individuos reclutados fue 40% menor que los previamente presentes para todas las formas de vida, excepto lianas. El reclutamiento de lianas fué de 7 a 500% mayor que la abundancia original en los fragmentos y en la selva contínua. En general la similitud de especies fué mayor entre fragmentos que entre fragmentos y selva contínua, con el fragmento de 1-ha siendo el menos similar. Las curvas de rango/abundancia de especies, mostraron que las especies de selva contínua en todas las formas de vida tendieron a desaparecer de los fragmentos, mientras que las especies comunes en los fragmentos estuvieron ausentes en la selva contínua. En general, nuestros resultados sugieren que la composición de formas de vida y la estructura del banco regenerativo en fragmentos tienden a convertirse en una comunidad de plántulas pobre en especies. La pérdida de diversidad de especies del sotobosque, pero especialmente de plántulas de árboles, amenaza el mantenimiento de la biodiversidad y pone en peligro la regeneración futura de la selva. [source] Water savings in mature deciduous forest trees under elevated CO2GLOBAL CHANGE BIOLOGY, Issue 12 2007SEBASTIAN LEUZINGER Abstract Stomatal conductance of plants exposed to elevated CO2 is often reduced. Whether this leads to water savings in tall forest-trees under future CO2 concentrations is largely unknown but could have significant implications for climate and hydrology. We used three different sets of measurements (sap flow, soil moisture and canopy temperature) to quantify potential water savings under elevated CO2 in a ca. 35 m tall, ca. 100 years old mixed deciduous forest. Part of the forest canopy was exposed to 540 ppm CO2 during daylight hours using free air CO2 enrichment (FACE) and the Swiss Canopy Crane (SCC). Across species and a wide range of weather conditions, sap flow was reduced by 14% in trees subjected to elevated CO2, yielding ca. 10% reduction in evapotranspiration. This signal is likely to diminish as atmospheric feedback through reduced moistening of the air comes into play at landscape scale. Vapour pressure deficit (VPD)-sap flow response curves show that the CO2 effect is greatest at low VPD, and that sap flow saturation tends to occur at lower VPD in CO2 -treated trees. Matching stomatal response data, the CO2 effect was largely produced by Carpinus and Fagus, with Quercus contributing little. In line with these findings, soil moisture at 10 cm depth decreased at a slower rate under high-CO2 trees than under control trees during rainless periods, with a reversal of this trend during prolonged drought when CO2 -treated trees take advantage from initial water savings. High-resolution thermal images taken at different heights above the forest canopy did detect reduced water loss through altered energy balance only at <5 m distance (0.44 K leaf warming of CO2 -treated Fagus trees). Short discontinuations of CO2 supply during morning hours had no measurable canopy temperature effects, most likely because the stomatal effects were small compared with the aerodynamic constraints in these dense, broad-leaved canopies. Hence, on a seasonal basis, these data suggest a <10% reduction in water consumption in this type of forest when the atmosphere reaches 540% ppm CO2. [source] Vegetation and disturbance history of a rare dwarf pitch pine community in western New England, USAJOURNAL OF BIOGEOGRAPHY, Issue 10-11 2002Glenn Motzkin Abstract Aim, This study documents the vegetation history and age-structure of a rare, ridgetop dwarf pine,oak community and compares the dynamics of this unusual vegetation with similar dwarf pine communities found elsewhere in the north-eastern United States (US). Location, The study area is located on the summit of Mt Everett in the Taconic Mountains of south-western Berkshire County, Massachusetts, USA (42°06,N 73°26,W). Methods, Vegetation composition, tree age-structure, physical site characteristics, and evidence of fire and other disturbances were determined for twelve 15 × 15 m plots in dwarf pine,oak vegetation and two plots in oak forests on the summit. Age-structure analyses, tree-ring patterns, and historical records of human and natural disturbance were used to investigate the long-term history and dynamics of the summit vegetation. Results, The summit of Mt Everett has been dominated by dwarf pines (1,3 m tall) and ericaceous shrubs similar to the modern vegetation throughout the historical period; there is no evidence that tall-stature forests occurred on the site at any point in the past few centuries. The summit supports uneven-aged stands; pitch pine (Pinus rigida) recruitment began in the 1830s and occurred in every decade since the 1860s. Average pitch pine age is seventy-eight with a range of 12,170 years. Red oak (Quercus rubra) and red maple (Acer rubrum) increased in importance in the twentieth century, with most stems establishing from 1940 to 1980. Pitch pine radial growth rates averaged <0.5 mm year,1 while red oak and red maple averaged 1.0 and 0.8 mm year,1, respectively. In some areas, hardwoods have overtopped pitch pines, apparently resulting in pitch pine mortality. Whereas most dwarf pitch pine communities occur on sites that burn frequently and have a high degree of cone serotiny, we found no evidence of recent fires or cone serotiny. Small amounts of macroscopic charcoal that we documented may have resulted from fires in the pre-European or early historical periods. Conclusions, Harsh edaphic conditions and chronic low-level disturbances on the summit, including frequent winter storms, have apparently contributed to the establishment, long-term persistence, and slow radial growth of dwarf pitch pines on Mt Everett. The ability of dwarf pines to persist on a site in the absence of frequent fire is highly unusual among North-eastern barrens and has not been well-incorporated into previous conceptual ecological models of these communities. Our results suggest that even among North-eastern barrens, the summit of Mt Everett is characterized by highly unusual vegetation and dynamics. The site has long been recognized as regionally significant and should be afforded the strictest conservation protection. With no evident history of human disturbance or recent fire, there is no apparent need for immediate active management of the site. [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] Neighbourhood interactions and environmental factors influencing old-pasture succession in the Central PyreneesJOURNAL OF VEGETATION SCIENCE, Issue 1 2004í Dole Abstract. The shrub Buxus sempervirens and the trees Abies alba and Fagus sylvatica have recently recolonized old-pastures in the Central Pyrenees. We mapped all live and dead individuals (> 1.3 m tall) in a large forest plot in Ordesa Valley to examine the importance of density-dependent processes during recolonization. Biotic interactions were inferred from changes in horizontal structure and the influences of neighbours on tree survival. Buxus differentially influenced establishment and survival of tree species, thereby controlling future canopy composition and spatial structure. The rapidly invading Abies formed denser patches on elevated sites less occupied by Buxus, whereas Fagus preferentially established within shrubs. Abies reached densities which led to intense intraspecific competition and high mortality rates among saplings. Self-thinning in Abies led to smaller numbers of regularly spaced survivors, and greater relative dominance of Fagus. Disregarding intraspecific effects and abiotic environment, Abies survival was significantly lower under Buxus shrubs, which suggests that the spatial location and abundance of Abies was constrained by the location of Buxus. Fagus survival was not related to Buxus density, but remained significantly lower in denser Abies patches. The higher mortality of Fagus in denser Abies patches, and the resulting spatial segregation of the species, reflects asymmetric interspecific competition. Inhibition from Buxus shrubs and intraspecific competition prevent invading Abies from dominating and may therefore help in maintaining a mixed Abies-Fagus stand. [source] Micro-coaxial Ka-band Gysel power dividersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2010Yuya Saito Abstract Monolithic, 450-,m tall, rectangular coaxial Gysel divider is presented in this article. The divider is fabricated by a surface micromachining process with six sequentially deposited copper layers. Athree-port, resistor-less divider has overall loss of 0.6 dB at 30 GHz, input port reflection coefficient better than ,10 dB, and output amplitude and phase misbalances of ±0.18 dB and ±1.8°, respectively, throughout Ka-band. The device is designed in a way that permits straightforward realization of a Gysel divider with integrated resistors. Electromagnetic and electrothermal analyses and design of the divider are conducted, and good agreement with measurements is obtained. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 474,478, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.24956 [source] Development of eight polymorphic microsatellites for an Australasian rainforest tree species, Cryptocarya mackinnoniana (Lauraceae)MOLECULAR ECOLOGY RESOURCES, Issue 6 2007J. A. WELLS Abstract We developed eight microsatellite markers for Cryptocarya mackinnoniana to study the spatial genetic structure and ecological correlates of parentage in secondary rainforests in Australia's Wet Tropics. The microsatellite loci were screened in 99 trees, and 623 seedlings < 0.24 m tall, at a site extending from primary rainforest into adjacent 50-year-old secondary rainforest. The eight loci were polymorphic, exhibiting between three and 11 alleles, and gene diversity (HE) from 0.25 to 0.84. For the trees, no departures from Hardy,Weinberg equilibrium were detected, except at locus Cm03, which had an estimated null allele frequency of 0.0903. No locus combinations exhibited linkage disequilibrium. [source] Photosynthesis, light and nitrogen relationships in a young deciduous forest canopy under open-air CO2 enrichmentPLANT CELL & ENVIRONMENT, Issue 12 2001Y. Takeuchi Abstract Leaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides trees in a developing canopy under free-air CO2 enrichment in Wisconsin, USA. After 2 years of growth, the trees averaged 1·5 and 1·6 m tall under ambient and elevated CO2, respectively, at the beginning of the study period in 1999. They grew to 2·6 and 2·9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloud-free days (PPFDday,sat) around the lowermost branches was 16·8 ± 0·8 and 8·7 ± 0·2% of values at the top for the ambient and elevated CO2 canopies, respectively. Elevated CO2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFDday,sat throughout the canopies, and elevated CO2 did not affect that relationship. Leaf Ps light-response curves responded differently to elevated CO2, depending upon canopy position. Elevated CO2 increased Pssat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO2. Consequently, estimated daily integrated Ps on cloud-free days (Psday,sat) was stimulated by elevated CO2 only in the upper canopy. Psday,sat of the lowermost branches was actually lower with elevated CO2 because of the darker light environment. The lack of CO2 stimulation at the mid- and lower canopy was probably related to significant down-regulation of photosynthetic capacity; there was no down-regulation of Ps in the upper canopy. The relationship between Psday,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole-canopy Ps or photosynthetic N use efficiency. Elevated CO2 had no effect on the optimization of canopy N allocation. [source] Hurricane Impacts on a Mangrove Forest in the Dominican Republic: Damage Patterns and Early Recovery,BIOTROPICA, Issue 3 2001Ruth E. Sherman ABSTRACT On 22 September 1998, Hurricane Georges passed over the Dominican Republic causing extensive damage to a 4700 ha mangrove forest that has been the site of a detailed study of vegetation and ecosystem dynamics since 1994. We resurveyed the vegetation in permanent plots at 7 and 18 months after the hurricane to document structural damage of the forest and evaluate early recovery patterns. The intensity of damage was patchy across the landscape. Mortality (>5 cm DBH) ranged from 14 to 100 percent (by density) among the 23 different plots and averaged 47.7 percent across all plots. Reductions in total basal area ranged from 9 to 100 percent, averaging 42.4 percent. Mortality increased by 9 percent between surveys at 7 and 18 months post-hurricane. Interspecific differences in susceptibility to wind damage appeared to be a primary factor contributing to spatial patterns in mortality. Laguncularia racemosa experienced much less mortality (26%) than either Rhizophora mangle (50%) or Avicennia germinans (64%), and plot-level mortality was strongly associated with differences in species composition. There were no clear relationships between canopy height and tree damage at this site. Over 80 percent of the of the surviving R. mangle trees exhibited less than 50 percent crown damage, whereas ca 60 percent of the L. racemosa survivors suffered almost complete (75,100%) crown loss. By 18 months after the hurricane, the percentage of L. racemosa trees in the 75 to 100 percent damage class was reduced to 20 percent; in contrast, the health of many R. mangle individuals appeared to be declining, as the percentage of trees in the 50 to 100 percent damage class increased from 16 to 36 percent. Understory light levels, as measured by the gap light index, increased from an average value of 3 percent in the pre-hurricane forest to 51 percent at 7 months after the hurricane and decreased slightly to 47 percent at 18 months. Few saplings (>1 m tall and <5 cm DBH) survived the hurricane; 72 percent of the tagged individuals in transect-based plots and 66 percent of saplings in pre-hurricane canopy gaps were killed. Seedling and sapling populations of all three species appear to be recovering rapidly although their densities still are lower than in the pre-hurricane forest. It is too early to predict the trajectory of forest recovery, and continued monitoring of the spatial and temporal patterns of forest development is needed to improve our understanding of the role that large-scale disturbance events play on the dynamics of mangrove forest ecosystems. RESUMES El 22 de septiembre de 1998, el huracán Georges pasó sobre la República Dominicana causando daños extensos a 47 km2 de manglar que ha sido objeto un estudio detallado de vegetacion y dinámica de la communidad desde 1994. Se tomarón muestras de la vegetación en parcelas permanentes 7 y 18 meses después de paso del huracán para documentar los daños estructurales del bosque y evaluar los modelos de recuperacion temprana que siguieron posteriormente. La intensidad del daño fue irregular a través del paisaje. La mortalidad (>5 cm de dap) fue de 14 a 100 por ciento (para la densidad) en las 23 parcelas con un promedio de 47.7 por ciento. La reducción en área basal total fue de 9 a 100 por ciento con un promedio de 42.4 por ciento. La mortalidad aumentó 9 por ciento a los 7 y 18 meses después del huracán. Las diferencias interspecificas en la susceptibilidad a los daños causados por el viento fueron un factor contribuyente importante en los patrones espacios de mortalidad. Laguncularia racemosa sufrió menor mortalidad (26%) que Rhizophora mangle (50%) o Avicennia germinans (64%), la mortalidad en las parcelas estuvo asociada fuertemente con la diferencia en composición de especies. No hubo ningún patron definido entre la altura del dosel y el daño del árbol. Más del 80 por ciento de los árboles sobrevivientes de R. mangle exhibieron daoñres menores de 50 por ciento en sus copas, mientras que ca 60 por ciento de los L. racemosa sobrevivientes sufrió una perdida casi total (75-100%). Dieciocho meses despues del huracan, el porcentaje de arboles de L. racemosa con daños del 75-100 por ciento se redujó a 20 por ciento; en contraste, la salud de muchos individuos de R. mangle disminuyó conforme el porcentaje de árboles con daños del 50-100 por ciento aumentó de 16 a 36 por ciento. Los niveles de penetración de luz en el sotobosque, medidos como el indice de iluminacion en los claros, aumentó de un promedio de 3 por ciento antes del huracán. a 51 por ciento 7 meses después del huracán, y disminuyo ligeramente a 47 por [source] | ||||||||||