Journal Article

Soil nutrients and beta diversity in the Bornean Dipterocarpaceae: evidence for niche partitioning by tropical rain forest trees

Curran, L.M, Zak, D.R, Paoli, G.D

2006

Overview

1. The relative importance of niche- and dispersal-mediated processes in structuring diverse tropical plant communities remains poorly understood. Here, we link mesoscale beta diversity to soil variation throughout a lowland Bornean watershed underlain by alluvium, sedimentary and granite parent materials (c. 340 ha, 8-200 m a.s.l.). We test the hypothesis that species turnover across the habitat gradient reflects interspecific partitioning of soil resources. 2. Floristic inventories (greater than or equal to 1 cm d.b.h.) of the Dipterocarpaceae, the dominant Bornean canopy tree family, were combined with extensive soil analyses in 30 (0.16 ha) plots. Six samples per plot were analysed for total C, N, P, K, Ca and Mg, exchangeable K, Ca and Mg, extractable P, texture, and pH. 3. Extractable P, exchangeable K, and total C, N and P varied significantly among substrates and were highest on alluvium. Thirty-one dipterocarp species (n = 2634 individuals, five genera) were recorded. Dipterocarp density was similar across substrates, but richness and diversity were highest on nutrient-poor granite and lowest on nutrient-rich alluvium. 4. Eighteen of 22 species were positively or negatively associated with parent material. In 8 of 16 abundant species, tree distribution (greater than or equal to 10 cm d.b.h.) was more strongly non-random than juveniles (1-10 cm d.b.h.), suggesting higher juvenile mortality in unsuitable habitats. The dominant species Dipterocarpus sublamellatus (> 50% of stems) was indifferent to substrate, but nine of 11 'subdominant' species (> 8 individuals ha(-1)) were substrate specialists. 5. Eighteen of 22 species were significantly associated with soil nutrients, especially P, Mg and Ca. Floristic variation was significantly correlated with edaphic and geographical distance for all stems greater than or equal to 1 cm d.b.h. in Mantel analyses. However, juvenile variation (1-10 cm d.b.h.) was more strongly related to geographical distance than edaphic factors, while the converse held for established trees (greater than or equal to 10 cm d.b.h.), suggesting increased importance of niche processes with size class. 6. Pervasive dipterocarp associations with soil factors suggest that niche partitioning structures dipterocarp tree communities. Yet, much floristic variation unrelated to soil was correlated with geographical distance between plots, suggesting that dispersal and niche processes jointly determine mesoscale beta diversity in the Bornean Dipterocarpaceae.

• Publisher: British Ecological Society,Blackwell Science Ltd,Blackwell Science,Blackwell Publishing Ltd
• Subject: Alluvium / Animal and plant ecology / Animal, plant and microbial ecology / beta diversity / Biodiversity / Biological and medical sciences / Biological taxonomies / Borneo / botanical composition / Botany / Dipterocarpaceae / diversity / dominance / ecological function / Edaphic factors / Flowers & plants / Forest ecology / Forest habitats / forest trees / Fundamental and applied biological sciences. Psychology / General aspects / Genetic Diversity and Species Richness / habitats / Human ecology / magnesium / mass effects / mesoscale / neutral / niche / niche partitioning / niches / phosphorus / Plant ecology / Rainforests / seed dispersal / Shorea / Soil ecology / soil fertility / Soil nutrients / soil parent materials / soil pH / Soil sciences / soil texture / spatial distribution / spatial variation / species diversity / Tropical forests / Tropical rain forests / Watersheds