Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with ...variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24–50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9–34% and 5–29%, respectively), and all environmental variables together explain 13–39% of compositional variation within a plot. A large fraction of variation (19–37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe.
Savannakhet Province, Lao People's Democratic Republic (PDR), is a small area that is connected to Thailand, other areas of Lao PDR, and Vietnam via road No. 9. This province has been increasingly ...affected by carbon dioxide (CO2) emitted from the transport corridors that have been developed across the region. To determine the effect of the CO2 increases caused by deforestation and emissions, the total above-ground biomass (AGB) and carbon stocks for different land-cover types were assessed. This study estimated the AGB and carbon stocks (t/ha) of vegetation and soil using standard sampling techniques and allometric equations. Overall, 81 plots, each measuring 1600 m2, were established to represent samples from dry evergreen forest (DEF), mixed deciduous forest (MDF), dry dipterocarp forest (DDF), disturbed forest (DF), and paddy fields (PFi). In each plot, the diameter at breast height (DBH) and height (H) of the overstory trees were measured. Soil samples (composite n = 2) were collected at depths of 0-30 cm. Soil carbon was assessed using the soil depth, soil bulk density, and carbon content. Remote sensing (RS; Landsat Thematic Mapper (TM) image) was used for land-cover classification and development of the AGB estimation model. The relationships between the AGB and RS data (e.g., single TM band, various vegetation indices (VIs), and elevation) were investigated using a multiple linear regression analysis. The results of the total carbon stock assessments from the ground data showed that the MDF site had the highest value, followed by the DEF, DDF, DF, and PFi sites. The RS data showed that the MDF site had the highest area coverage, followed by the DDF, PFi, DF, and DEF sites. The results indicated significant relationships between the AGB and RS data. The strongest correlation was found for the PFi site, followed by the MDF, DDF, DEF, and DF sites.
Background. Many Thai farmers who live in national parks farmlands lack a formal education. They usually lack of knowledge on soil quality improvement and proper use of fertilizer. They illegally ...trespass in forest areas because of soil deterioration in their own limited expanses of farmland. Consequently, most of them are arrested, creating individual and family problems.
Aim. This “soil analysis and appropriate fertilizer use game” (SAAFU game) was designed for farmers having low-formal education to realize the soil analysis before planting and improve the appropriate chemical fertilizer usage.
Method.This quasi-experiential research used pre- and post-tests to evaluate the game session processes and learning of the players. The important steps were: 1) analysis of soil in the land box; 2) making decisions to buy fertilizer; 3) calculating, harvesting and selling products. Debriefing was also used to discuss and exchange their knowledge and experiences. Follow up process was also performed.
Results. The pre- and post-test score showed the better understanding of appropriate fertilizer use of the players. Soon after the gaming sessions, players went to their fields and collected 31 soil samples for soil nutrient analysis. Players also disseminated knowledge to their relatives and neighbors. As a result, non-players of Dongbak(22), Wangmon(9) and Chaimongkol(2) collected soil samples for soil nutrient analysis. Moreover, they grouping together to buy quicklime and fertilizers to get cheaper price.
Conclusion. This simple game can be used effectively with farmers having low-formal education. After the game and simulation, most of them realized how important of soil nutrients and soil analysis before planting and were able to teach their relatives and neighbours about soil collecting. This indicated the successful of this game.
Importance of Demographic Niches to Tree Diversity Condit, Richard; Ashton, Peter; Bunyavejchewin, Sarayudh ...
Science (American Association for the Advancement of Science),
07/2006, Volume:
313, Issue:
5783
Journal Article
Peer reviewed
Open access
Most ecological hypotheses about species coexistence hinge on species differences, but quantifying trait differences across species in diverse communities is often unfeasible. We examined the ...variation of demographic traits using a global tropical forest data set covering 4500 species in 10 large-scale tree inventories. With a hierarchical Bayesian approach, we quantified the distribution of mortality and growth rates of all tree species at each site. This allowed us to test the prediction that demographic differences facilitate species richness, as suggested by the theory that a tradeoff between high growth and high survival allows species to coexist. Contrary to the prediction, the most diverse forests had the least demographic variation. Although demographic differences may foster coexistence, they do not explain any of the 16-fold variation in tree species richness observed across the tropics.
The integration of ecology and evolutionary biology requires an understanding of the evolutionary lability in species' ecological niches. For tropical trees, specialization for particular soil ...resource and topographic conditions is an important part of the habitat niche, influencing the distributions of individual species and overall tree community structure at the local scale. However, little is known about how these habitat niches are related to the evolutionary history of species. We assessed the relationship between taxonomic rank and tree species' soil resource and topographic niches in eight large (24–50 ha) tropical forest dynamics plots. Niche overlap values, indicating the similarity of two species' distributions along soil or topographic axes, were calculated for all pairwise combinations of co-occurring tree species at each study site. Congeneric species pairs often showed greater niche overlap (i.e., more similar niches) than non-congeneric pairs along both soil and topographic axes, though significant effects were found for only five sites based on Mantel tests. No evidence for taxonomic effects was found at the family level. Our results indicate that local habitat niches of trees exhibit varying degrees of phylogenetic signal at different sites, which may have important ramifications for the phylogenetic structure of these communities.
The protection of tropical forests is one of the most urgent issues in conservation biology because of the rapid deforestation that has occurred over the last 50 years. Even in protected forests, the ...anthropogenic effects from newly expanding villages such as harvesting of medicinal plants, pasturing cattle and forest fires can induce environmental modifications, especially on the forest floor. We evaluated the anthropogenic effects of the daily activities of neighboring residents on natural forests in 12 plots extending from the village boundary into a natural forest in Thailand. The basal area per unit land area did not present a significant trend; however, the species diversity of woody plants decreased linearly towards the village boundary, which caused a loss of individual density because of severe declines in small saplings compared with adult trees and large saplings in proximity to the village. An analysis of tree-size categories indicates a lack of small samplings near the village boundary. The current forest appears to be well protected based on the adult tree canopy, but regeneration of the present-day forests is unlikely because of the loss of seedlings.
Long‐term surveys of entire communities of species are needed to measure fluctuations in natural populations and elucidate the mechanisms driving population dynamics and community assembly. We ...analysed changes in abundance of over 4000 tree species in 12 forests across the world over periods of 6–28 years. Abundance fluctuations in all forests are large and consistent with population dynamics models in which temporal environmental variance plays a central role. At some sites we identify clear environmental drivers, such as fire and drought, that could underlie these patterns, but at other sites there is a need for further research to identify drivers. In addition, cross‐site comparisons showed that abundance fluctuations were smaller at species‐rich sites, consistent with the idea that stable environmental conditions promote higher diversity. Much community ecology theory emphasises demographic variance and niche stabilisation; we encourage the development of theory in which temporal environmental variance plays a central role.
Accurately projecting global carbon dynamics requires understanding controls over temporal and spatial tropical forest biomass variation. Changes in tropical forest aboveground biomass per area are ...most commonly estimated using repeat forest plot censuses, but errors in these estimates can be relatively large, limiting our ability to detect real changes in forest carbon. One source of error is nonstandard heights of diameter measurement, which are common in tropical forests because buttressed trees are usually measured above buttresses. Nonstandard and temporally variable measurement heights affect biomass change estimates because tree trunks taper—higher measurements result in smaller diameters and, thus, smaller estimated biomass. Modeling trunk taper is a potential way to correct for biases associated with nonstandard and changing measurement heights. We measured trunk taper for 260 buttressed trees in five lowland tropical forests to assess variation in taper within and among sites. Trunks taper more slowly in trees with larger diameters above buttress, taller buttresses, and higher wood density; these variables together explain 29% of taper variation. We also used plot data to quantify the distribution of measurement heights—and potential for bias in biomass estimates. We found significant variation in measurement heights among plots, and over time within plots. At the site level, our general taper model (taper predicted from diameter above buttress, buttress height, and wood density) produced site‐level biomass estimates within 3.4%, on average, of estimates from measured taper. We recommend using this model to reduce bias from nonstandard measurement heights in studies of tropical forest biomass variation.
in Spanish is available with online material.
Resumen
Para entender la dinámica del carbono en los bosques tropicales se requiere conocer los factores que determinan la vairación espacial y temporal de la biomasa aérea. En los bosques tropicales, los cambios de la biomasa aérea por unidad de área se estiman principalmente usando medidas repetidas sobre parcelas permanentes. Sin embargo, errores debido a sesgos en los estimados pueden ser realtivamente altos, lo cual limita nuestra capacidad de detectar los cambios reales en las reservas de carbono almacenadas en los bosques. Una causa común de sesgo es la medición del diámetro a diferentes alturas. La imposibilidad de estandarizar la altura de medición de los diámetros a 1,3 m en los bosques tropicales, se da en buena medida por la presencia de gambas/bambas Cambios en la altura de medición del diámetro afectan las estimaciones de biomasa de forma proporcional al aumento en la conicidad de los troncos (disminución del diámetro con la altura). Es decir, mientras más alto sea el punto de medición del diámetro, menor va a ser la biomasa total estimada. Por esta razón, los modelos de conicidad aparecen como un método potencialmente útil para corregir los sesgos causados por la medición de diámetros a diferentes alturas. En este estudio, medimos la forma del tronco de 260 árboles en 5 bosques tropicales de tierras bajas para evaluar la variación de la conicidad dentro y entre bosques. Se encontró que la conicidad disminuye a medida que incrementa el tamaño del diámetro por encima de las gambas, incrementa al altura de las gambas e incrementa la densidad de madera; estas variables juntas explican el 29% de la variación de forma de los troncos. Adicionalmente, usamos datos de las parcelas para cuantificar la distribución de las alturas de medición y el potencial de sesgo en las estimaciones de biomasa, encontrando una variación significativa en las alturas de medición entre parcelas, así como una variación temporal dentro de las mismas. A nivel de sitio, nuestro modelo general para predecir la conicidad del tronco (usando el diámetro por encima de la gamba, la altura de la gamba y la densidad de la madera) resultó en estimaciones de biomasa dentro del 3.4%, en promedio, de las estimaciones de la forma del tronco medida. Se recomienda el uso de este modelo de conicidad para reducir el sesgo producido por la medición de diámetros a diferentes alturas en estudios de variación de biomasa de bosques tropicales.
In tropical forest plots, the diameters of large, buttressed trees are measured above the usual measurement height of 1.3 m. Cushman et al. used 3D photogrammetry and plot data to explore how trunk shape and measurement heights vary within and among five tropical forest plots, potentially biasing estimates of aboveground biomass from pantropical allometries.
Organisms of all species must balance their allocation to growth, survival and recruitment. Among tree species, evolution has resulted in different life‐history strategies for partitioning resources ...to these key demographic processes. Life‐history strategies in tropical forests have often been shown to align along a trade‐off between fast growth and high survival, that is, the well‐known fast–slow continuum. In addition, an orthogonal trade‐off has been proposed between tall stature—resulting from fast growth and high survival—and recruitment success, that is, a stature−recruitment trade‐off. However, it is not clear whether these two independent dimensions of life‐history variation structure tropical forests worldwide.
We used data from 13 large‐scale and long‐term tropical forest monitoring plots in three continents to explore the principal trade‐offs in annual growth, survival and recruitment as well as tree stature. These forests included relatively undisturbed forests as well as typhoon‐disturbed forests. Life‐history variation in 12 forests was structured by two orthogonal trade‐offs, the growth−survival trade‐off and the stature−recruitment trade‐off. Pairwise Procrustes analysis revealed a high similarity of demographic relationships among forests. The small deviations were related to differences between African and Asian plots.
Synthesis. The fast–slow continuum and tree stature are two independent dimensions structuring many, but not all tropical tree communities. Our discovery of the consistency of demographic trade‐offs and life‐history strategies across different forest types from three continents substantially improves our ability to predict tropical forest dynamics worldwide.
Zusammenfassung
Individuen aller Arten müssen ihrer Ressourcen zwischen Wachstum, Überleben und Nachwuchsrekrutierung allozieren. Baumarten haben, evolutionär bedingt, verschiedene biologische Strategien entwickelt, wie sie ihre Ressourcen auf diese wichtigen demografischen Prozesse verteilen. In tropischen Wäldern lassen sich die biologischen Strategien der Bäume oft entlang eines Gradienten anordnen, welcher Arten mit schnellem Wachstum von Arten mit langem Überleben trennt, i.e. das bekannte Fast‐Slow‐Kontinuum. Ein weiterer orthogonaler Trade‐off welcher Arten die durch schnelles Wachstum und langes Überleben eine hohe Statur erreichen können von solchen Arten trennt, die eine hohe Rekrutierungsrate vorweisen (i.e. ein Statur‐Rekrutierungs‐Trade‐off) wurde bisher zwar postuliert, aber es wurde noch nicht geklärt, ob die tropischen Wälder auch global von diesen beiden unabhängigen Dimensionen der biologischen Strategien strukturiert werden.
In dieser Studie haben wir die Daten von 13 großflächigen und langfristigen Plots in tropischen Wäldern über drei Kontinente analysiert und die vorherrschenden Trade‐offs zwischen den jährlichen Wachstums‐, Überlebens‐ und Rekrutierungsraten sowie der Statur der lokalen Baumarten bestimmt. Die untersuchten Flächen umfassten dabei relative ungestörte, sowie Taifun‐gestörte Wälder. In zwölf dieser Wälder ordneten sich die biologischen Strategien der lokalen Baumarten entlang zweier orthogonaler Trade‐offs an, einem Trade‐off zwischen Wachstum und Überleben und einem Trade‐off zwischen Statur und Rekrutierung. Anschließende paarweise Procrustes‐Analysen zeigten eine hohe Ähnlichkeit in den Korrelationen zwischen den artspezifischen demografischen Raten zwischen diesen unterschiedlichen Wäldern. Wir fanden auch kleinere, aber signifikante Unterschiede, zwischen den Wäldern in Afrika und Asien.
Synthesis. Das Fast‐Slow‐Kontinuum und die Statur der Baumarten stellen zwei unabhängige Dimensionen dar, welche viele, aber nicht alle tropischen Baumgemeinschaften strukturieren. Unsere Ergebnisse zur Übereinstimmung der demographischen Trade‐offs und den resultierenden biologischen Strategien über Wälder und Kontinente hinweg, ermöglicht es uns in Zukunft die Entwicklung von tropischen Wäldern weltweit besser vorherzusagen.
All species must balance their allocation to growth, survival and recruitment, resulting in different life‐history strategies for partitioning resources to these demographic processes. Across 13 (sub)tropical forests, the diversity of life‐history strategies in tropical tree communities is often, but not always, structured along two independent dimensions that are related to the fast–slow continuum and to a gradient in tree stature.
Editor's Choice
The theory of metabolic ecology predicts specific relationships among tree stem diameter, biomass, height, growth and mortality. As demographic rates are important to estimates of carbon fluxes in ...forests, this theory might offer important insights into the global carbon budget, and deserves careful assessment. We assembled data from 10 old‐growth tropical forests encompassing censuses of 367 ha and > 1.7 million trees to test the theory's predictions. We also developed a set of alternative predictions that retained some assumptions of metabolic ecology while also considering how availability of a key limiting resource, light, changes with tree size. Our results show that there are no universal scaling relationships of growth or mortality with size among trees in tropical forests. Observed patterns were consistent with our alternative model in the one site where we had the data necessary to evaluate it, and were inconsistent with the predictions of metabolic ecology in all forests.
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