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

The 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 +/- 0.18 mg N kg(-1) d(-1) at an incubation conditions of 25 degrees 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 +/- 0.20 mg N kg(-1) d(-1)), followed by forests (2.35 +/- 0.42 mg N kg(-1), d(-1)) and grasslands (0.57 +/- 0.13 mg N kg(-1) d(-1)). 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. (C) 2015 Elsevier B.V. All rights reserved.