摘要:土壤酶化学计量比是揭示微生物生长代谢过程及评价土壤养分资源限制状况的重要指标。油茶是中国南方主要的木本油料作物，近年来愈来愈受关注，但鲜有从生态化学计量学的角度深入理解人工经济林的土壤微生物养分限制状况。本文以亚热带地区不同林龄油茶人工林土壤为研究对象，采用时空互代法在区域尺度上随机选取32个不同林龄油茶人工林并将其分为四个林龄组（ < 9年幼龄林；9-20年近熟林；21-60年成熟林； > 60年过熟林），通过测定土壤碳（C）、氮（N）、磷（P）转化酶活性（β-葡糖苷酶（BG）、α-纤维素酶（CBH）、β-乙酰葡糖胺糖苷酶（NAG）、亮氨酸氨基肽酶（LAP）、酸性磷酸酶（AP））及土壤理化因子，探讨不同林龄油茶人工林土壤C、N、P转化酶化学计量特征及其与土壤理化因子的关系。结果表明：五种C、N、P转化酶活性均有随林龄增大而增加的趋势，且AP活性显著高于其它四种酶活性。相关分析结果表明，五种土壤C、N、P转化酶活性均与土壤有机碳和总氮显著相关，与土壤总磷和速效磷含量不相关。土壤酶化学计量比ln（CBH+BG）：ln（NAG+LAP）、ln（CBH+BG）：ln（AP）和ln（NAG+LAP）：ln（AP）均随林龄增大而一定程度增加。亚热带区油茶人工林土壤酶C：N：P化学计量比为1：1：1.5，这与全球生态系统土壤酶C：N：P化学计量比1：1：1相偏离，表明亚热带地区油茶人工林土壤微生物生长受磷素限制。冗余分析（RDA）进一步揭示土壤有机碳含量是影响土壤酶活性和酶化学计量比的主要因子。因此，在油茶人工林经营管理中应考虑磷和外源碳的投入，提高土壤微生物酶活性，缓解油茶人工林生态系统的磷限制。研究结果可为亚热带区油茶人工林土壤养分管理和可持续利用提供基础理论支撑。



Abstract:The stoichiometry of soil enzymatic activity is a key indicator to predict microbial growth and metabolism and can be used to evaluate soil nutrient limitation. Camellia oleifera, the main economically important woody oil-producing plant in southern China, has received much attention recently; however, little is known about the soil ecoenzymatic stoichiometry and microbial resource limitation in C. oleifera plantations. In this study, to understand soil nutrient limitations in C. oleifera plantations in the subtropical region of China, we collected 96 soil samples from 32 sample site plantations with varying levels of C. oleifera stand development and analyzed the soils' enzymatic activities. Plantation with four different C. oleifera stand ages were chosen: < 9 years, 9-20 years, 21-60 years, and > 60 years. We examined the activities of 1,4-β-glucosidase (BG), α-cellulases (CBH), leucine aminopeptidase (LAP), 1,4-β-N-acetylglucosaminidase (NAG), and alkaline phosphatases (AP), as well as soil physicochemical parameters. We analyzed the stoichiometric characteristics of the enzymes and the relationships between the soils' physicochemical properties and ecoenzymatic stoichiometry. The results indicate that all soil enzyme activities increased with increasing stand age in the early stage, and then the activity of those enzymes stabilized. In addition, AP activity was greater than those of BG, CBH, NAG, and LAP. According to a correlation analysis, all soil enzyme activities were positively correlated with soil organic carbon (SOC) and total nitrogen (TN) content but were not correlated to total phosphorus (TP) or Olsen phosphorous (P) content. The ratios of ln(CBH+BG):ln(NAG+LAP), ln(CBH+BG):ln(AP), and ln(NAG+LAP):ln(AP) showed a similar pattern of increase with stand age. The soil ecoenzymatic C:N:P stoichiometry in our C. oleifera plantations was 1:1:1.5, which was inconsistent with the 1:1:1 global pattern of C:N:P stoichiometry. This result suggests that C. oleifera plantations in the subtropical region of China were limited by phosphorus. A canonical redundancy analysis (RDA) indicated that SOC was the dominant factor affecting soil enzymatic activity and ecoenzymatic stoichiometry. Additionally, TP and pH were selected by the RDA model as the significant environmental factors influencing soil ecoenzymatic stoichiometry. Our results suggest that carbon and phosphorus adjustments could be an important strategy to improve soil enzymatic activities and alleviate the phosphorus limitation of C. oleifera plantations. Our study provides solid data to support nutrient management and the sustainable management of C. oleifera plantations in the subtropical region of China.





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