Carbon and nitrogen contents in particle–size fractions of topsoil along a 3000 km aridity gradient in grasslands of northern China

Abstract

Abstract. Climate factors such as aridity significantly influence soil carbon (C) and nitrogen (N) stocks in terrestrial ecosystems. Further, soil texture plays an important role in driving changes of soil C and N contents at regional scale. However, it remains uncertain whether such changes resulted from the variation of different soil particle–size factions and/or the C and N concentrations in those fractions. We examined the distribution of total C and N in both bulk soil and different soil particle–size fractions, including sand (53–2000 µm), silt (2–53 µm), and clay (< 2 µm), along a 3000 km transect in arid and semi-arid grasslands of northern China. Across the whole transect, sand content was positively and silt content was negatively correlated with increasing aridity. Carbon content in bulk soils (0–10 cm) ranged from 4.36 to 46.16 Mg C ha−1, while N content ranged from 0.22 to 4.28 Mg N ha−1 across different sampling sites on the transect. The total C and N concentrations and contents in bulk soils as well as in the three particle–size fractions tended to be negatively correlated with aridity. The concentrations and contents of total C and N in bulk soils were positively correlated with silt and clay contents and negatively correlated with sand content. Positive correlations were observed between the concentrations and contents of C or N in bulk soils and the C or N concentrations in the three soil particle–size fractions. By characterizing such a large scale aridity gradient, our results highlight that aridity would decrease soil C and N contents both by favoring increased sand content and by decreasing C and N concentrations in all the three soil fractions. These patterns thus have significant implications for understanding soil C and N sequestration under scenarios of increasing aridity in global drylands that are predicted to occur this century.

Phosphorus transformations along a large‐scale climosequence in arid and semiarid grasslands of northern China

“…All surface soils across the transect are sands or sandy loams, with >60% sand and a strong acid reaction (Figure S2) [ Wang et al ., , ]. The elemental composition of surface soil is similar in all three soil classes, with composition after ignition dominated by SiO 2 (70–76%), with smaller amounts of Al 2 O 3 (11–12%) and Fe 2 O 3 (3–4%) [ Lei et al ., ; Shi et al ., ].…”

Large‐Scale Distribution of Molecular Components in Chinese Grassland Soils: The Influence of Input and Decomposition Processes

“…Alpine grasslands on the QTP are characterized by high belowground biomass (BGB) (Fan et al, ; Liu et al, ), prevailing low temperatures and widespread frozen soils (Baumann et al, ; Shang et al, ), leading to an enhanced preservation of SOM (Liu et al, ; Shang et al, ; Yang et al, ). In contrast, temperate grasslands are developed under an arid and semiarid climate with precipitation recognized as a critical factor in controlling primary production and microbial activity (Bai et al, ; Chen et al, ; Wang, Sistla, et al, ). Soil OC in the temperate grasslands tends to decrease with increasing temperature (Wang, Sistla, et al, ; Yang et al, ), as temperature increase enhances microbial decomposition more than plant detrital production in this water‐limited ecosystem (Wang, Sistla, et al, ; Yang et al, ).…”

“…Soil OC in the temperate grasslands tends to decrease with increasing temperature (Wang, Sistla, et al, ; Yang et al, ), as temperature increase enhances microbial decomposition more than plant detrital production in this water‐limited ecosystem (Wang, Sistla, et al, ; Yang et al, ). Nonetheless, grasslands in both regions are shown to be highly susceptible to climatic and environmental changes (Chen et al, ; Liu et al, ), which may result in grassland degradation and alterations to carbon exchanges between soil and the atmosphere (Baumann et al, ; Wang, Sistla, et al, ; Yang et al, ). However, most of the current studies have relied on bulk measurements of total soil OC and nitrogen (N) contents to examine SOM dynamics.…”

“…Organic carbon (OC) stored in the soil organic matter (SOM) of grasslands accounts for approximately one third of soil OC stock in China . Therefore, soil OC dynamics in China's grasslands have attracted considerable attention in recent decades Liu et al, 2017;Wang, Sistla, et al, 2016;Yang et al, 2010). developed under an arid and semiarid climate with precipitation recognized as a critical factor in controlling primary production and microbial activity (Bai et al, 2004;Chen et al, 2015;Wang, Sistla, et al, 2016).…”

“…Therefore, soil OC dynamics in China's grasslands have attracted considerable attention in recent decades Liu et al, 2017;Wang, Sistla, et al, 2016;Yang et al, 2010). developed under an arid and semiarid climate with precipitation recognized as a critical factor in controlling primary production and microbial activity (Bai et al, 2004;Chen et al, 2015;Wang, Sistla, et al, 2016). Soil OC in the temperate grasslands tends to decrease with increasing temperature (Wang, Sistla, et al, 2016;Yang et al, 2010), as temperature increase enhances microbial decomposition more than plant detrital production in this water-limited ecosystem (Wang, Sistla, et al, 2016;Yang et al, 2010).…”