中国科学院水利部水土保持研究所机构知识库

Global nitrogen (N) deposition can change the contents and stoichiometry of soil resources and thus of microbial
communities, which can drive the flow of carbon (C) and nutrients in food webs in forest ecosystems. It is critical
to understand the status of soil elements required for microbial growth, the elements of microbial growth, and
how soil microorganisms would reallocate resources and release extracellular enzymes for adjusting the imbalance
between resources and microorganisms due to N deposition. We chose a plantation of Pinus tabuliformis
where N had been added across a gradient (0–9 gNm−2 y−1) for two years to reveal how matters flow and soil
resources were reallocated by microbes to cope N addition. Our results showed that although two years of N
inputs only significantly affect the ratio between the activities of β-1,4-N‑acetylglucosaminidase and alkaline
phosphatase in the 0–20 cm soil layer, activities for both organic N and organic phosphorus (P) acquisition
enzymes scale with C acquisition with slope of about 1, following the global ecoenzymatic patterns. Contents and
elemental ratios of soil organic carbon (SOC), total N (TN) and total phosphorus (TP) were changed after this
short-term N addition. Ratios of SMBC, SMBN and SMBP were concentrated from soil and lower than ratios of
soil resources. Soil microbial communities under N addition were limited by N and co-limited by P at 3 and
6 gNm−2 y−1. Although imbalance between soil and microbes caused by N addition, in the 0–20 and 20–40 cm
layers, C: N relationship between soil and the microbial community indicated microbial community maintained
homeostasis. However, C:P relationship between soil and the microbial community indicated no microbial
community homeostasis. In addition, both soil resources elemental stoichiometry and contents can affect soil
microbial communities. Further study of the structure of soil microbial communities, identifying the microbes
that are more adaptive to high N concentrations and N deposition, is needed for a better understanding of the
mechanisms of nutrient flow in the food web and how to maintain microbial homeostasis in response to N
deposition in forest ecosystems.