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.
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.
This study intends to develop the soil N, P and K balance in peat soils by quantifying the input, internal flow and output of the nutrients under different water table conditions, with and without ...the pineapple crops uptake. The soil samples for each water table conditions were analyzed for total-N, mineral-N, available-P and exchangeable K. Results showed that pineapple of the variety Moris requires high input of N and K compare to P. Without crops uptake, all treatments indicate positive soil nutrient balance where the treatment with fluctuating water table between 40-80 cm depth showed highest positive balances. In contrast, negative nutrient balance occurred in the presence of uptake by pineapple, where treatment with fluctuating water table between 0-40 cm recorded the highest nutrient deficiency. It is suggested that fluctuating water table influence the soil nutrient dynamics and soil nutrient balance and in this case act as the main pathways of nutrient loss through leaching.
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.
This study was conducted to test the difference in growth performance of Acacia mangium on rich and poor sites created by windrowing as the usual site preparation method for large scale plantations. ...The experimental plots were laid out in Ulu Sedili Forest Reserve in a one-year-old plantation. Soil samples were analyzed and trees were measured in 1985 and 1989. Basal area development and volume increment as well as timber production were calculated. After one year as well as after five years planting there was a significant difference between dimensions of trees of both sites.
Foliar elemental levels, determined in different canopy tiers of Acacia mangium growing on two different soil types, were compared with soil textural and chemical data. Foliage of trees growing on ...relatively fertile Jambu soils had higher elemental concentrations than those growing on nutrient impoverished Rhudua soils. On both soil types, foliar elemental levels differed in the different canopy tiers, but their distributions among tiers did not conform with observed patterns in other taxa. It is recommended that for an evaluation of the fertility status of A. mangium, the lower tier of sun-exposed foliage should be sampled for N and P levels and the top tier for other elemental levels. Kepekatan nutrien daun pada bahagian atas, tengah dan bawah silara A. mangium yang hidup pada dua jenis tanah pantai dibandingkan dengan tektur dan data kimia tanah. Kepekatan nutrien pada daun pokokyang hidup di atas tanah jenis Jambu yang subur (secara relatif) adalah lebih tinggi jika di bandingkan dengan daun pokokyang tumbuh di atas tanah jenis Rhudua (yang ketandusan zat nutrien). Pada kedua-dua jenis tanah yang dikaji, kadar zat nutrein pada daun berbeza pada ketiga-tiga bahagian silara, di mana kepekatan zat nutriennya tidak seperti yang lazim terjadi pada spesies yang lain. Kajian ini menunjukkan bahawa bagi penentuan kepekatan zat nitrogen dan fosporan, daun A. mangium dari bahagian bawah silara yang terdedah pada cahaya matahari bolehlah di sampel bagi kedua-dua jenis tanah yang di kaji. Bagi zat nutrien yang lain pula, daun dari bahagian atas silara adalah di syorkan.
PDF
