Regional‐scale patterns of soil microbes and nematodes across grasslands on the Mongolian plateau: relationships with climate, soil, and plants

Abstract

Belowground communities exert major controls over the carbon and nitrogen balances of terrestrial ecosystems by regulating decomposition and nutrient availability for plants. Yet little is known about the patterns of belowground communities and their relationships with environmental factors, particularly at the regional scale where multiple environmental gradients co‐vary. Here, we describe the patterns of belowground communities (microbes and nematodes) and their relationships with environmental factors based on two parallel studies: a field survey with two regional‐scale transects across the Mongolia plateau and a water‐addition experiment in a typical steppe. In the field survey, soils and plants were collected across two large‐scale transects (a 2000‐km east–west transect and a 900‐km south–north transect). At the regional‐scale, the variations in soil microbes (e.g. bacterial PLFA, fungal PLFA, and F/B ratio) were mainly explained by precipitation and soil factors. In contrast, the variation in soil nematodes (e.g. density of trophic groups and the bacterial‐feeding/fungal‐feeding nematode ratio) were primarily explained by precipitation. These variations of microbe or nematode variables explained by environmental factors at regional scale were derived from different vegetation types. Along the gradient from nutrient‐poor to nutrient‐rich vegetation types, the total variation in soil microbes explained by precipitation increased and that explained by plant and soil decreased, while the opposite was true for soil nematodes. Experimental water addition, which increased rainfall by 30% during the growing season, increased biomass or density of belowground communities, with the nematodes being more responsive than the microbes. The different responses of soil microbial and nematode communities to environmental gradients at the regional scale likely reflect their different adaptations to climate, soil nutrients, and plants. Our findings suggest that the soil nematode and microbial communities are strongly controlled by bottom‐up effects of precipitation alone or in combination with soil conditions.

Short-term grazing exclusion has no impact on soil properties and nutrients of degraded alpine grassland in Tibet, China

“…Therefore, the soil properties and nutrients of alpine grasslands in Tibet were primarily driven by the climate gradient distributions but not by grazing exclusion treatments. Climatic factors, including temperature and precipitation, can directly or indirectly impact soil quality status by controlling soil environmental conditions, soil weathering process, soil microbe and enzyme activities, substrate availability, translocation of dissolved ions, and so on (Barthold et al, 2013;Clarholm and Skyllberg, 2013;Chen et al, 2015).…”

Patterns and drivers of soil microbial communities in Tibetan alpine and global terrestrial ecosystems

“…For example, the soil nutrient status may drive a shift in the composition of soil microbial communities. Previous studies have also demonstrated that biotic factors such as the community-weighted means of plant functional traits, aboveground biomass (AGB) and plant species richness (SR) can explain spatial variations in soil microbial communities at the regional scale (de Vries et al, 2012;Chen et al, 2014aChen et al, , 2015. Furthermore, mean annual precipitation (MAP) may regulate soil microbial communities via changes in soil properties and biotic factors such as vegetation composition (de Vries et al, 2012;Chen et al, 2014a).…”

“…First, previous studies mainly targeted temperate grasslands (Drenovsky et al, 2010;de Vries et al, 2012;Chen et al, 2014aChen et al, , 2015Hu et al, 2014;Ma et al, 2015). First, previous studies mainly targeted temperate grasslands (Drenovsky et al, 2010;de Vries et al, 2012;Chen et al, 2014aChen et al, , 2015Hu et al, 2014;Ma et al, 2015).…”

Unusual soil nematode communities on karst mountain peaks in southwest China

“…Previous studies of soil nematode communities have mainly focused on agricultural, forest, and grassland ecosystems (Yeates, 2003;Ferris et al, 2004;Zhao et al, 2011;Chen et al, 2013aChen et al, , 2014Neher et al, 2014;Zhao and Neher, 2014;Zhao et al, 2014b;Zhang et al, 2015). Soil nematode communities have also been studied in deserts (Liang et al, 2002;Pen-Mouratov and Steinberger, 2005), the tundra (Sohlenius and Bostr€ om, 1999), and in polar regions (Freckman and Virginia, 1997;Velasco-Castrill on and Stevens, 2014).…”