Home About us Contact
|
Home About us Contact | ||
|
|
||
Forest Plants (forest + plant)
Terms modified by Forest Plants Selected AbstractsA 3.5 ka record of paleoenvironments and human occupation at Angkor Borei, Mekong Delta, southern CambodiaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2003Paul Bishop Microfossil and sedimentological data from a 3.1 m core extracted from a reservoir (baray) at the ancient Cambodian settlement of Angkor Borei in the Mekong Delta have provided a continuous record of sedimentation and paleoenvironments dating from about 2000 cal yr B.C. Palynological data indicate that for much of the cal. 1st and 2nd millennia B.C. mangroves dominated the regional vegetation, while extensively and regularly burnt grasslands dominated the local vegetation. Turbid, nutrient-rich standing water characterized the core locality, perhaps suggesting a connection with rivers in the area. An abrupt change during the cal. 5th to 6th centuries A.D. involved a dramatic reduction in grasslands and the expansion of secondary forest or re-growth taxa. These changes are synchronous with an abrupt decline in the concentration of microscopic charcoal particles in the sediments, and the colonization of the core locality by swamp forest plants. These changes are taken to indicate a shift in land-use strategies or, possibly, a period of land abandonment. The age for the construction of the baray is interpreted to be in the 17th,19th centuries, but this dating remains speculative. Construction of the Angkor Borei baray exploited a preexisting body of standing water, so its construction was fundamentally different from the methods used at the Angkorian capital in northern Cambodia. © 2003 Wiley Periodicals, Inc. [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] Homogenization of forest plant communities and weakening of species,environment relationships via agricultural land useJOURNAL OF ECOLOGY, Issue 3 2007MARK VELLEND Summary 1Disturbance may cause community composition across sites to become more or less homogenous, depending on the importance of different processes involved in community assembly. In north-eastern North America and Europe local (alpha) diversity of forest plants is lower in forests growing on former agricultural fields (recent forests) than in older (ancient) forests, but little is known about the influence of land-use history on the degree of compositional differentiation among sites (beta diversity). 2Here we analyse data from 1446 sites in ancient and recent forests across 11 different landscapes in north-eastern North America and Europe to demonstrate decreases in beta diversity and in the strength of species,environment relationships in recent vs. ancient forests. 3The magnitude of environmental variability among sites did not differ between the two forest types. This suggests the difference in beta diversity between ancient and recent forests was not due to different degrees of environmental heterogeneity, but rather to dispersal filters that constrain the pool of species initially colonizing recent forests. 4The observed effects of community homogenization and weakened relationships between species distributions and environmental gradients appear to persist for decades or longer. The legacy of human land-use history in spatial patterns of biodiversity may endure, both within individual sites and across sites, for decades if not centuries. [source] Effects of mesoscale environmental heterogeneity and dispersal limitation on floristic variation in rain forest fernsJOURNAL OF ECOLOGY, Issue 1 2006MIRKKA M. JONES Summary 1Field studies to evaluate the roles of environmental variation and random dispersal in explaining variation in the floristic composition of rain forest plants at landscape to regional scales have yet to reach a consensus. Moreover, only one study has focused on scales below 10 km2, where the effects of dispersal limitation are expected to be easiest to observe. 2In the present study, we estimate the importance of differences in some key environmental variables (describing canopy openness, soils and topography) relative to the geographical distances between sample plots as determinants of differences in pteridophyte (ferns and fern allies) species composition between plots within a c. 5.7 km2 lowland rain forest site in Costa Rica. 3To assess the relative importance of environmental vs. geographical distances in relation to the length of environmental gradient covered, we compared the results obtained over the full range of soil types, including swamps, with those for upland soils alone. 4Environmental variability was found to be a far stronger predictor of changes in floristic differences than the geographical distance between sample plots. In particular, differences in soil nutrient content, drainage and canopy openness correlated with floristic differences. 5The decline in mean floristic similarity with increasing geographical distance was stronger than proposed by the random dispersal model over short distances (up to c. 100 m), which is probably attributable to both dispersal limitation and environmental changes. The scatter around the mean was large at all distances. 6Our initial expectation was that the effects of dispersal limitation (represented by geographical distance) on observed patterns of floristic similarity would be stronger, and those of environmental differences weaker, than at broader spatial scales. Instead, these results suggest that the niche assembly view is a more accurate representation of pteridophyte communities at local to mesoscales than the dispersal assembly view. [source] The relative importance of dispersal limitation of vascular plants in secondary forest succession in Muizen Forest, BelgiumJOURNAL OF ECOLOGY, Issue 5 2001Kris Verheyen Abstract 1,Distribution patterns (frequency and percentage cover) of 18 forest plant species were studied in 34 ha of mixed deciduous forest (Muizen Forest, north Belgium). Stands varied in age between 6 and more than 223 years and both slow and fast colonizing species were studied. 2,Detailed land use history data were combined with the species distribution maps to identify species-specific colonization sources and calculate colonization distances. 3,A multiple logistic regression model was constructed with four covariables: pH (which can impose limits on the potential species-distribution), secondary forest age, distance from nearest colonization source and age,distance interaction, to allow us to account for the gradual completion of colonization over time. 4,We could distinguish species which are limited by both dispersal and recruitment (Primula elatior, Arum maculatum and Lamium galeobdolon), mainly by dispersal (Anemone nemorosa, Deschampsia cespitosa), mainly by recruitment (Paris quadrifolia and Polygonatum multiflorum) and by neither (Geum urbanum, Ranunculus ficaria, Glechoma hederacea, Aegopodium podagraria, Ajuga reptans, Adoxa moschatellina and Oxalis acetosella). 5,The low colonizing capacity of ancient forest plants cannot be attributed to a single cause; rather both dispersal and recruitment are limiting but the relative importance varies. [source] Regulation of Light Energy Utilization and Distribution of Photosynthesis in Five Subtropical Woody PlantsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 3 2007Nan Liu Abstract The adaptations and responses of photosynthesis to long- and short-term growth light gradient treatments were investigated in five subtropical forest plants, namely Pinus massoniana Lamb., Schima superba Gardn. et Champ., Castanopsis fissa (Champ. ex Benth.) Rehd. et Wils., Acmena acuminatissima (BI.) Merr et Perry, and Cryptocarya concinna Hance. With diurnal changes in sunlight and air temperature, the de-epoxidation state and lutein content in the five woody plants under three light intensities first increased and then decreased during the day. However, maximal photochemical efficiency (Fv/Fm; where Fm is the maximum fluorescence yield and Fv is variable fluorescence) and the photochemical quantum yields of photosystem (PS) II (,PSII) of the species examined changed in the opposite manner, with those in plants grown under 100% natural light changing the most. After long-term treatment (21 months), anti-oxidant capacity (1, 1-diphenyl-2-picrylhydrazyl radical (DPPH·)-scavenging capacity) and utilization of excitation energy showed differences in modulation by different light intensities. It was shown that A. acuminatissima and C. concinna, as dominant species in the late succession stage of a subtropical forest in Dinghu mountain, South China, were better able to adapt to different light environments. However, P. massoniana, the pioneer species of this forest, exhibited less adaptation to low light intensity and was definitely eliminated by the forest succession process. [source] Plant Community Structure in Tropical Rain Forest Fragments of the Western Ghats, India,BIOTROPICA, Issue 2 2006S. Muthuramkumar ABSTRACT Changes in tree, liana, and understory plant diversity and community composition in five tropical rain forest fragments varying in area (18,2600 ha) and disturbance levels were studied on the Valparai plateau, Western Ghats. Systematic sampling using small quadrats (totaling 4 ha for trees and lianas, 0.16 ha for understory plants) enumerated 312 species in 103 families: 1968 trees (144 species), 2250 lianas (60 species), and 6123 understory plants (108 species). Tree species density, stem density, and basal area were higher in the three larger (> 100 ha) rain forest fragments but were negatively correlated with disturbance scores rather than area per se. Liana species density, stem density, and basal area were higher in moderately disturbed and lower in heavily disturbed fragments than in the three larger fragments. Understory species density was highest in the highly disturbed 18-ha fragment, due to weedy invasive species occurring with rain forest plants. Nonmetric multidimensional scaling and Mantel tests revealed significant and similar patterns of floristic variation suggesting similar effects of disturbance on community compositional change for the three life-forms. The five fragments encompassed substantial plant diversity in the regional landscape, harbored at least 70 endemic species (3.21% of the endemic flora of the Western Ghats,Sri Lanka biodiversity hotspot), and supported many endemic and threatened animals. The study indicates the significant conservation value of rain forest fragments in the Western Ghats, signals the need to protect them from further disturbances, and provides useful benchmarks for restoration and monitoring efforts. [source] Responses to Fire in Selected Tropical Dry Forest Trees,BIOTROPICA, Issue 5 2006Sarah M. Otterstrom ABSTRACT Fire is a frequent disturbance in the tropical dry forests of Central America, yet very little is known about how native species respond to such events. We conducted an experimental burn in a tropical dry forest of western Nicaragua to evaluate plant responses to fire with respect to survivorship and recruitment. Measurements of woody vegetation of all size classes were carried out prior to the prescribed burn and three successive years post fire. We selected the 15 most abundant species <10 cm DBH to assess percent survivorship and sprouting responses post fire. Changes in seedling densities for these 15 most abundant species and the 15 least abundant species were analyzed using a repeated measure ANOVA. We also assessed changes in seedling densities for three species of international conservation concern. We found three major fire-coping strategies among common dry forests plants: resisters (low fire-induced mortality), resprouters (vigorous sprouting), and recruiters (increased seeding post-fire). While survivorship was generally high relative to tropical moist forest species, those species with lower survivorship used either seeding or sprouting as an alternative strategy for persisting in the forest community. Seed dispersal mechanisms, particularly wind dispersal, appear to be an important factor in recruitment success post-fire. Burn treatment led to a significant increase in the density of seedlings for two species of conservation concern: Guaiacum sanctum and Swietenia humilis. Results of this study suggest that common dry forest species in western Nicaragua are fire tolerant. Further study of individual species and their fire responses is merited. RESUMEN El incendio forestal causa perturbación frecuente en los bosques secos tropicales de Centroamérica, sin embargo se conoce poco del comportamiento de las especies nativas a ésta perturbación. Nosotros llevamos a acabo una quema experimental en un bosque seco tropical de Nicaragua occidental para evaluar el comportamiento de la flora con respecto a la sobrevivencia y reclutamiento de las especies después de la quema. Se midió todas las clases diamétricas de la vegetación leñosa antes de la quema controlada y durante 3 años consecutivos después de la quema. Seleccionamos las 15 especies más abundantes en la clase diametrica <10 dap para evaluar el porcentaje de sobrevivencia y la actividad de rebrote después de la quema. Cambios en la densidad de plántulas para las 15 especies más abundantes y para las 15 especies menos abundantes fueron analizadas utilizando el análisis de varianza de medición repetido (ANOVA). También, evaluamos cambios en la densidad de plántulas para tres especies de interés a nivel internacional con respecto a su conservación. En la flora común del bosque seco se encontró tres estrategias principales utilizadas por las especies para contender con los incendios forestales, estas fueron: resistores (baja mortalidad por el incendio), rebrotadores (rebrotamiento vigoroso), y reclutores (reclutamiento elevado pos-incendio). Mientras la sobrevivencia de especies en el bosque seco en general fue relativamente alta a la de especies de bosque húmedo tropical, las especies con menor sobrevivencia utilizaron el reclutamiento ó rebrotamiento como estrategia para persistir en la comunidad boscosa. El mecanismo de dispersión de semilla, particularmente la dispersión eólica, parece ser un factor importante en el éxito de reclutamiento después de la quema. Las quemas controladas produjeron un aumento significativo en la densidad de plántulas para dos de las especies de interés para la conservación: Guaiacum sanctum L. (Zygophyllaceae) y Swietenia humilis Zucc. (Meliaceae). Resultados de esta investigación sugieren que las especies comunes del bosque seco de Nicaragua son tolerantes al fuego. Por lo tanto, es merecido hacer más estudios de estas especies y su comportamiento ante la perturbación del fuego. [source] | ||||||||||