Liu Meihua, Gan Bingping, Li Quan, Xiao Wenfa, Song Xinzhang
State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou, China.
Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, China.
Front Plant Sci. 2022 Mar 9;13:834184. doi: 10.3389/fpls.2022.834184. eCollection 2022.
Soil extracellular enzymes play an important role in microbial functions and soil nutrient cycling in the context of increasing N deposition globally. This is particularly important for Chinese fir () forests because of the decline in soil fertility induced by successive rotation. In this study, we aimed to determine the effects of simulated N deposition (N30: 30 kg ha year; N60: 60 kg ha year) and phosphorus addition (P20: 20 mg kg; P40: 40 mg kg) on the activity and stoichiometry of soil extracellular enzymes related to soil C, N, and P cycling in Chinese fir. The results showed that N addition alone increased the activity of soil β-1,4 glucosidase (BG) but decreased the activity of -acetyl-β-d-glucosidase (NAG) and leucine aminopeptidase (LAP). N addition increased the ratios of soil enzymes, C:N and C:P, alleviated microbial N-limitation, and aggravated microbial C-limitation. P addition alone increased enzyme activity, and P40 addition increased the ratio of BG to soil microbial biomass carbon (MBC), and (NAG + LAP):MBC activity ratio, thereby aggravating C restriction. N and P co-addition significantly affected soil extracellular enzyme activity and stoichiometry. For instance, BG activity and BG:MBC activity ratio increased significantly under the N30 + P40 treatment, which intensified C-limitation. Soil pH was the main factor influencing enzyme activity, and these variables were positively correlated. The stoichiometric relationships of enzyme reactions were coupled with soil pH, total nitrogen (TN), and available phosphorus (AP). Our results indicate that changes in soil characteristics induced by N and P inputs influence the activities of soil microorganisms and result in changes in microbial resource acquisition strategies. This study provides useful insights into the development of management strategies to improve the productivity of Chinese fir forests under scenarios of increasing N deposition.
在全球氮沉降增加的背景下，土壤胞外酶在微生物功能和土壤养分循环中发挥着重要作用。由于连栽导致土壤肥力下降，这对杉木林尤为重要。在本研究中，我们旨在确定模拟氮沉降（N30：30千克·公顷⁻¹·年⁻¹；N60：60千克·公顷⁻¹·年⁻¹）和磷添加（P20：20毫克·千克⁻¹；P40：40毫克·千克⁻¹）对杉木林中与土壤碳、氮和磷循环相关的土壤胞外酶活性和化学计量的影响。结果表明，单独添加氮增加了土壤β-1,4-葡萄糖苷酶（BG）的活性，但降低了N-乙酰-β-D-葡萄糖苷酶（NAG）和亮氨酸氨肽酶（LAP）的活性。添加氮增加了土壤酶的C:N和C:P比率，缓解了微生物的氮限制，并加剧了微生物的碳限制。单独添加磷增加了酶活性，添加P40增加了BG与土壤微生物生物量碳（MBC）的比率以及（NAG + LAP）:MBC活性比率，从而加剧了碳限制。氮和磷共同添加显著影响土壤胞外酶活性和化学计量。例如，在N30 + P40处理下，BG活性和BG:MBC活性比率显著增加，这加剧了碳限制。土壤pH是影响酶活性的主要因素，这些变量呈正相关。酶反应的化学计量关系与土壤pH、总氮（TN）和有效磷（AP）相关。我们的结果表明，氮和磷输入引起的土壤特性变化影响土壤微生物的活性，并导致微生物资源获取策略的改变。本研究为在氮沉降增加的情景下制定提高杉木林生产力的管理策略提供了有用的见解。
