Ren Yan, Wang Ying, Zhang Xiulan, Liu Xionghui, Liu Pei, Chen Liang
Faculty of Life Science and Technology, Central South University of Forestry and Technology, Changsha 410004, China.
Huitong National Station for Scientific Observation and Research of Chinese Fir Plantation Ecosystems in Hunan Province, Huitong 438107, China.
Microorganisms. 2024 Aug 20;12(8):1716. doi: 10.3390/microorganisms12081716.
Increasing nitrogen (N) deposition alters the availability of soil nutrients and is likely to intensify phosphorus (P) limitations, especially in P-limited tropical and subtropical forests. Soil microorganisms play vital roles in carbon (C) and nutrient cycling, but it is unclear whether and how much N and P imbalances affect the soil's microbial metabolism and mechanisms of nutrient limitations. In this study, a 3-year field experiment of N and P addition (control (CK), 100 kg N ha yr (N), 50 kg P ha yr (P), and NP) was set up to analyze the extracellular enzyme activities and stoichiometry characteristics of the top mineral soils in Chinese fir plantations with different stand ages (7, 20, and 33 years old). The results showed that the enzyme activities associated with the acquisition of C (β-1,4-glucosidase (BG) and β-d-cellobiohydrolase (CBH)) and P (acid phosphatases (APs)) in the N treatment were significantly higher than those in the CK treatment. Moreover, vector analysis revealed that both the vector's length and angle increased in stands of all ages, which indicated that N addition aggravated microbial C and P limitations. The P and NP treatments both significantly decreased the activity of AP and the enzymes' N:P ratio, thereby alleviating microbial P limitations, as revealed by the reduction in the vector's angle. Stand age was found to promote all enzymatic activities but had no obvious effects on the limitation of microbial metabolism with or without added nutrients in the soils under Chinese fir. Available N, Olsen-P, and pH were the main drivers of microbial metabolic limitations related to C nutrients. These results provide useful data for understanding the change in soil microbial activity in response to environmental changes, and suggest that P fertilization should be considered for management to improve productivity and C sequestration in Chinese fir plantation in the context of increased deposition of N.
氮（N）沉降增加会改变土壤养分的有效性，并可能加剧磷（P）限制，尤其是在P限制的热带和亚热带森林中。土壤微生物在碳（C）和养分循环中起着至关重要的作用，但尚不清楚N和P失衡是否以及在多大程度上影响土壤微生物代谢和养分限制机制。在本研究中，设置了一个为期3年的N和P添加田间试验（对照（CK）、100 kg N·ha⁻¹·yr⁻¹（N）、50 kg P·ha⁻¹·yr⁻¹（P）和NP），以分析不同林龄（7、20和33年）杉木人工林表层矿质土壤的胞外酶活性和化学计量特征。结果表明，N处理中与C获取相关的酶活性（β-1,4-葡萄糖苷酶（BG）和β-d-纤维二糖水解酶（CBH））和P获取相关的酶活性（酸性磷酸酶（APs））显著高于CK处理。此外，向量分析表明，所有林龄林分中向量的长度和角度均增加，这表明添加N加剧了微生物对C和P的限制。P和NP处理均显著降低了AP的活性和酶的N:P比，从而减轻了微生物对P的限制，这一点从向量角度的减小可以看出。研究发现，林龄促进了所有酶活性，但对杉木林下土壤中添加或不添加养分时微生物代谢的限制没有明显影响。有效N、 Olsen-P和pH是与C养分相关的微生物代谢限制的主要驱动因素。这些结果为理解土壤微生物活性响应环境变化的变化提供了有用的数据，并表明在N沉降增加的背景下，应考虑施肥管理以提高杉木人工林的生产力和碳固存。
