Competition for nitrogen between plants and microorganisms in grasslands: Effect of nitrogen application rate and plant acquisition strategy

Several studies have investigated how nitrogen (N) addition changes N competition between focal plant species and soil microorganisms; still, the impact on community-level plant-microbial N competition and the underlying mechanisms remain unclear. We conducted a short-term (4 h) 15N labeling experiment in an alpine meadow subjected to 7 years of NH4NO3 additions (0, 5, 10, and 15 g N m−2 year−1), by monitoring changes in soil properties (e.g., pH, Al3+, NH4+, NO3−), microbial biomass (MB), plant community composition, root traits (e.g., root length, root area, specific root length), as well as the plant (nine focal species and at the community level) and microbial N uptake. Change in the N competition between the nine focal plant species and microorganisms following N addition depended on the species. At the community level, the N addition rate did not affect plant-microbial competition for NH4 + and NO3 − (P > 0.05). Nitrogen addition directly decreased  NH4+competition (β= −0.700) ..., , , # Competition for nitrogen between plants and microorganisms in grasslands: effect of nitrogen application rate and plant acquisition strategy

# Description of the data and file structure

N form - N form of plant uptake

AM- N form of NH4+

NT- N form of NO3-

N addition rate - Nitrogen addition treatment: 0, 5, 10, and 15 g N m-2 year-1

Rep Replicates

AN - Available N, the first axis of a PCA of NH4+ (mg kg-1) and NO3- (mg kg-1)

pH - Soil pH

Al3+ -Aluminium ion content in soil (mg kg-1)

base_pca- The first axis of a PCA of soil base cations (Ca2+ (mg kg-1), K+ (mg kg-1) , Mg2+ (mg kg-1) )

MB_pca- The first axis of a PCA of microbial carbon (mg kg-1) and nitrogen (mg kg-1)

SR Species Richness

lgplant/MB - log-transformed of plant-microbial competition

多项研究已探讨氮（Nitrogen, N）添加如何改变目标植物物种与土壤微生物之间的氮竞争，但氮添加对群落尺度植物-微生物氮竞争的影响及其潜在作用机制仍不明晰。我们在经历7年硝酸铵（NH₄NO₃）添加处理（施氮梯度为0、5、10、15 g N m⁻²·year⁻¹）的高寒草甸中开展了时长4小时的短期¹⁵N标记试验，监测了土壤性质（如pH、铝离子（Al³+）、铵态氮（NH₄+）、硝态氮（NO₃⁻））、微生物生物量（Microbial Biomass, MB）、植物群落组成、根系性状（如根长、根表面积、比根长），以及植物（9种目标物种及群落尺度）和微生物的氮吸收量。

氮添加后9种目标植物物种与微生物间的氮竞争变化因物种而异。在群落尺度上，施氮速率并未显著影响植物与微生物对NH₄+和NO₃⁻的竞争（P > 0.05）。施氮直接降低了对NH₄+的竞争（β= -0.700）……

# 草地植物与微生物间的氮竞争：施氮速率与植物获取策略的影响

## 数据与文件结构说明
N form - 植物吸收的氮素形态
AM - 铵态氮（NH₄+）对应的氮形态
NT - 硝态氮（NO₃⁻）对应的氮形态
N addition rate - 施氮处理梯度：0、5、10、15 g N m⁻²·year⁻¹
Rep - 重复样本
AN - 有效氮（Available N），即铵态氮（NH₄+, 单位mg kg⁻¹）与硝态氮（NO₃⁻, 单位mg kg⁻¹）的主成分分析（Principal Component Analysis, PCA）第一轴得分
pH - 土壤pH值
Al3+ - 土壤铝离子含量（单位mg kg⁻¹）
base_pca - 土壤盐基阳离子（钙离子Ca²+、钾离子K+、镁离子Mg²+，单位均为mg kg⁻¹）的主成分分析第一轴得分
MB_pca - 微生物生物量碳（单位mg kg⁻¹）与微生物生物量氮（单位mg kg⁻¹）的主成分分析第一轴得分
SR Species Richness - 物种丰富度
lgplant/MB - 植物-微生物竞争强度的对数转换值