Soil spatial heterogeneity has been recognized as an important dimension of plants’ ecological niches. Despite the significant role of soil in partitioning forest niches, a mechanistic understanding of soil spatial heterogeneity is still incomplete, especially for fine-scale (defined here as smaller than 1 ha) variations in tropical rainforests. Few studies have examined how heterogeneity of soil properties is affected by litterfall at fine spatial scales.
Prof. CHEN Jin and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study within a 20-ha forest dynamics plot (21° 37′ 08″ N, 101° 35′ 07″ E), in a tropical seasonal rainforest in Xishuangbanna, SW China. They aimed to provide a mechanism that explained fine-scale soil heterogeneity. They performed high-density soil and litterfall sampling throughout a 1 ha tropical rainforest and measured soil properties (pH, N, P, and K) and corresponding litterfall properties (mass, N, P, and K). They then mapped the spatial distributions of these variables and calculated topographic position indexes using geostatistical analysis. Finally, they detected scale-dependent variation of all variables and tested effects of litterfall and topography on soil chemical heterogeneity along scale gradients using wavelet analysis.
The researchers found that soil properties had large and distinct spatial variability within their 1 ha plot. The wavelet variance indicated two main recurrent features: a peak of variation at intermediate scales (~25 m) and a rapid increase in variation at larger scales (>25 m). The result suggested that two different processes influenced soil heterogeneity. The low level of topographic variation within that small area was strongly associated with soil pH but poorly associated with all soil nutrients. Soil nutrients were significantly correlated to litterfall chemical fluxes.
Their finding supports the hypothesis that spatial heterogeneity of soil macronutrients in tropical rainforests can be strongly affected by biotic factors, while soil pH is strongly influenced by geochemical processes and that biotic factors act at smaller scales than geochemical processes.
Their study provides new insights from a soil-plant interaction perspective. The study extends the finding of plant feedback on soil nutrients from studies that look at individuals or species grown in monoculture, to patterns of fine-scale soil heterogeneity under a natural rainforest community.
Author Contact
CHEN Jin, Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Tel: 86 691 8715457
Fax: 86 691 8715070
E-mail: cj@xtbg.org.cn
Key Words
Tropical forest, soil heterogeneity, litterfall, soil nutrients, plant, Xishuangbanna
