Soil nematodes are one of the most important components in soil ecosystems and food webs, indirectly or directly participating in the major soil ecological processes. As a key bioindicator sensitive to environmental disturbance, soil nematodes are often affected by soil properties and climatic variables. To better understand the spatial dynamics of soil nematodes, it is vital to integrate the latitudinal and altitudinal gradients. However, most studies focus on single geographical gradient, which leads to incomplete knowledge about spatial distribution patterns of soil nematodes, as well as potential mechanisms. 

Supervised by Prof. DING Jianqing and Prof. HUANG Wei, LIU Jia, PhD from Wuhan Botanical Garden, conducted field surveys to examine how soil nematodes under tallow tree (Triadica sebifera) changed and which factors affected soil nematode communities, along the latitudinal (19.44~33.56°N) and altitudinal (Tianzhu Mountain, 100~1000 m a.s.l.) gradient in China. 

They found that the latitudinal and altitudinal patterns of soil nematodes under T. sebifera were quite different, respectively expressed as quadratic and linear trends. Moreover, soil carbon, nitrogen, moisture and annual precipitation were significant impact factors in the latitude survey, whereas no significant factor was found in the altitude study. 

These results further emphasize the importance of multidimensional and multifactorial studies for exploring spatial patterns of soil nematodes. Furthermore, these findings suggest that more cautions are needed in predicting the altitudinal pattern of biotic communities from latitudinal pattern, and vice versa, since altitudinal gradient is always not a simple repetition of latitudinal gradient. 

This work was supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China. Relevant research results have been published in Plant Ecology entitled "Latitudinal and altitudinal patterns of soil nematode communities under tallow tree (Triadica sebifera) in China". 

Sampling locations for soil nematodes under Triadica sebifera (Left) and the results of canonical correspondence analysis (Right) (Image by LIU Jia) 

The abundance of soil nematodes along latitudinal gradient (a) and altitudinal gradient (b) (Image by LIU Jia)