Aims

Subalpine forest ecosystems are sensitive to climate change, and extracellular enzyme activities and microbial metabolic limitation in soils are influenced by multiple factors including climate. The study aims to reveal the extracellular enzyme characteristics and microbial metabolic limitation in soils and their key drivers along an elevation gradient in subalpine forest ecosystems.

Methods

Microbial metabolic limitations in bulk and rhizosphere soils under Quercus aquifolioides forest along an elevation gradient (3100-4180 m a.s.l) of Pamuling Mountain on the eastern Qinghai-Tibetan Plateau were investigated by enzyme stoichiometry theory and path modelling analysis.

Results

Elevation had significant effects on the carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzyme activities, but the difference between bulk and rhizosphere soil was non-significant. Microbial metabolism was mainly limited by C and P, and showed a tendency to gradual shift from C and P limitation to C and N limitation at high elevation. The C limitation of microbial metabolism showed an increasing trend with elevation, implying greater C limitation at higher elevations where temperatures were lower. Therefore, we infer that the increase in temperature may help to alleviate C limitation of microbial metabolism in subalpine forest. Soil available nutrients affected N and P limitations of microbial metabolism, and soil pH, nutrient ratios and available nutrients mainly affected C limitation.

Conclusions

There were significant influences of elevation on soil enzyme activities and C limitation of microbial metabolism. Soil pH, nutrient stoichiometric characteristics and available nutrients were the key factors affecting soil microbial metabolism in subalpine Q. aquifolioides forest ecosystems.

中文翻译：

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青藏高原东部亚高山森林生态系统土壤细胞外酶特征及微生物代谢限制

目标

亚高山森林生态系统对气候变化敏感，土壤细胞外酶活性和微生物代谢受限受气候等多种因素的影响。该研究旨在揭示亚高山森林生态系统中沿海拔梯度的土壤中的细胞外酶特征和微生物代谢限制及其关键驱动因素。

方法

通过酶化学计量理论和路径模拟分析，研究了青藏高原东部帕木岭山海拔梯度（3100-4180 m asl）栎林下块体和根际土壤的微生物代谢限制。

结果

海拔对碳 (C)-、氮 (N)- 和磷 (P)- 获取酶活性有显着影响，但块状土壤和根际土壤之间的差异不显着。微生物代谢主要受C、P限制，在高海拔地区呈现由C、P限制逐渐向C、N限制转变的趋势。微生物代谢的 C 限制随着海拔的升高呈增加趋势，这意味着在温度较低的较高海拔处更大的 C 限制。因此，我们推断温度的升高可能有助于缓解亚高山森林微生物代谢的 C 限制。土壤速效养分影响微生物代谢的N和P限制，土壤pH、养分比和速效养分主要影响C限制。

结论

海拔对土壤酶活性和微生物代谢的碳限制有显着影响。土壤 pH 值、养分化学计量特征和有效养分是影响亚高山Q. aquifolioides森林生态系统土壤微生物代谢的关键因素。