Patterns and regulating mechanisms of soil nitrogen mineralization and temperature sensitivity in Chinese terrestrial ecosystems

Abstract

A B S T R A C TThe mineralization (or decomposition) processes of soil organic matter (SOM), from organic to inorganic, play important roles in supplying most of nutrient for plant growth. Thus, understanding the spatial pattern and regulating mechanisms of soil nitrogen mineralization rate (N min ) and its temperature sensitivity (Q 10 ) is of great significance for evaluating ecosystem productivity and the supply of soil available nitrogen (N). Here, data derived from 212 published papers in Chinese terrestrial ecosystems were used to explore the spatial pattern and regulating mechanisms of N min and Q 10 . The results showed that the average N min was 2.78 AE 0.18 mg N kg À1 d À1 at an incubation conditions of 25 C across Chinese terrestrial ecosystems, and it decreased gradually with increasing latitude (P < 0.01). The N min values were the highest in farmlands (3.08 AE 0.20 mg N kg À1 d ). The Q 10 values differed significantly among different ecosystems (P < 0.01), with an average of 1.58. The Q 10 values increased significantly with increasing latitude, supporting the hypothesis that the Q 10 values are higher in colder regions. Path analysis showed that N min is mainly affected by mean annual temperature and SOM content, whereas Q 10 is primarily affected by soil total nitrogen. The activation energy (E a ) of N min and substrate quality index (A) was strongly negatively correlated, indicating that the carbon-quality temperature hypothesis is applicable to N min at a large spatial scale. These findings provide new evidence that soil N availability in colder regions is likely to increase due to higher Q 10 under global warming scenarios, which may promote ecosystem productivity at higher latitudes.

Effects of aridity on soil microbial communities and functions across soil depths on the Mongolian Plateau

“…Soil C/N also strongly influenced total microbial biomass, bacterial biomass and MCS in deep soil layers, although its effects were not as strong as those of aridity. Given the substantial effects of substrate quality (as indicated by the C/N ratio) and quantity (as indicated by the SOC) on soil micro‐organisms, researchers generally agree that microbial communities quickly respond to changes in soil C/N ratio (Colman & Schimel, ; Liu et al, ). Interestingly, our results showed that the negative direct effects of aridity on fungal biomass were stronger in surface soil layers than deep soil layers, indicating that the effect of aridity was more important than that of soil substrates on fungal biomass in surface soils.…”

“…The strong positive relationships between SOC and soil C or N mineralization rates in our results are reasonable because SOC is the main source of energy for soil micro‐organisms (Colman & Schimel, ; Dungait et al, ; Kuzyakov, ). For instance, previous research showed that SOC content and clay concentration were direct drivers of soil C or N mineralization, while aridity had an indirect effect on SOC content (Bai et al, ; Colman & Schimel, ; Liu et al, ). The significant association between soil microbial properties and C or N mineralization rates indicates that soil micro‐organisms are largely responsible for C and N mineralization (Rousk, Michelsen, & Rousk, ; Schimel & Schaeffer, ).…”

“…The consistent importance of SOC and microbial properties for soil C mineralization throughout the four soil layers in the present study is partly in line with previous research conducted on mountain grassland soils (Garcia‐Pausas et al, ), which showed that soil C mineralization was positively correlated with extractable C content and that microbial activity in surface layers was positively correlated with N availability in deep soil layers. The strong direct effects of aridity on N mineralization rates in the deep soil layer (60–100 cm) indicate that aridity was the primary determinant of soil N mineralization in areas where the climate is harsh and soil substrates are scarce on the Mongolian Plateau (Cheng et al, ; Liu et al, ). The large percentage of the unexplained variance in soil mineralization in deep soil layers may possibly result from soil mineralization being controlled by multiple competing processes.…”

“…Although researchers have long recognized that soil C and N cycling are affected by climatic variables, soil substrates and edaphic properties (Dungait, Hopkins, Gregory, & Whitmore, ; Schimel & Schaeffer, ), which factors have been found to be most important differs among studies. For example, some studies have shown that the variations in soil N mineralization rates were mainly explained by the soil C/N ratio (Bai et al, ; Colman & Schimel, ; Liu et al, ), whereas other studies found that soil microbial biomass and activity (Rustad et al, ) or soil pH (Cheng et al, ; Liu et al, ) determined surface soil N mineralization rates at local or regional scales. Furthermore, because soil microbial biomass, SOM content and other soil properties change with soil depth, the importance of these factors for N mineralization might also change with soil depth.…”

Asymmetric responses of soil heterotrophic respiration to rising and decreasing temperatures

“…Temperature sensitivity (Q 10 ) is a useful index to describe the proportional change in R S with a 10 C increase in temperature (Lloyd and Taylor, 1994). Previous studies have demonstrated that Q 10 values vary greatly at different temperatures and in different ecosystems, ranging from nearly 1 to over 12 (Hamdi et al, 2013;Liu et al, 2015). Usually, higher Q 10 values are detected under colder temperatures versus warmer temperatures (Kirschbaum, 1995).…”