土壤磷有效性调控亚热带森林土壤酶活性和酶化学计量对凋落叶输入的响应

Soil phosphorus availability regulates the response of soil enzyme activity and enzymatic stoichiometry to litter addition in a subtropical forest

探究土壤胞外酶活性及其化学计量对了解土壤微生物的养分限制情况和土壤养分的循环过程具有重要意义。尽管亚热带森林土壤风化严重,土壤磷有效性低,但是亚热带森林生态系统具有较高水平的植被生产力。在气候变化(如变暖和CO_(2)浓度增加)背景下,预测植被生产力将会提高,这将增加凋落叶的输入。然而,未来不同质量凋落叶输入增加对土壤酶活性及其化学计量的影响是否受土壤磷有效性的调控仍不清楚。该研究以马尾松(Pinus massoniana)林土壤为研究对象,探究了3种不同质量(如叶碳氮比或碳磷比存在差异)的凋落叶(马尾松、醉香含笑(俗名:火力楠,Michelia macclurei)和枫香树(Liquidambar formosana))和磷添加对土壤理化性质、胞外酶活性的影响。同时,结合土壤酶化学计量、矢量长度(VL)和矢量角度(VA)分析,解析了土壤微生物的养分限制状况及其关键调控因素。结果表明:与对照相比,凋落叶添加增加了土壤β-N-乙酰氨基葡糖苷酶和酸性磷酸酶(ACP)活性。通过酶化学计量分析发现,凋落叶添加显著提高VL和VA,且影响强度表现为醉香含笑>枫香>马尾松,表明凋落叶添加会改变土壤微生物的养分限制状况,且影响程度与凋落叶的质量有关。与凋落叶单独添加相比,凋落叶与磷共同添加显著增加土壤有效磷含量,降低ACP活性和VA,表明磷添加有助于缓解凋落叶输入下土壤微生物的磷限制。冗余分析表明,土壤碳氮比、可溶性有机碳和有效磷含量是影响土壤酶活性和酶化学计量的主要因素。综上所述,该研究发现亚热带森林土壤微生物养分限制对凋落叶输入的响应不仅受凋落叶质量的影响,同时还受土壤磷有效性的调控。这一结果可以为未来气候变化下亚热带森林土壤微生物养分获取策略对不同凋落叶输入和磷添加的响应提供理论参考,同时也将有助于提高对亚热带低磷森林生态系统土壤生物地球化学循环过程的理解。

Aims It is of great significance to explore soil extracellular enzyme activity and its stoichiometry to understand soil nutrient availability and changes in the nutrient requirements of microorganisms.Subtropical forest ecosystems have high net primary productivity,but the availability of phosphorus(P)in soil is low due to severe soil weathering.Under climate change(i.e.,warming,elevated CO2 concentration),plant productivity is predicted to increase,which would increase the input of leaf litter.However,it is still unclear whether the effect of increasing litter input on soil enzyme activity and its stoichiometry is affected by soil P availability in the future.Methods This study investigated the effects of the addition of three kinds of litters(Pinus massoniana,Michelia macclurei and Liquidambar formosa)with different quality(characterized by different leaf C:N or C:P)and P on soil properties and enzyme activities in subtropical low-P soils.By analyzing the stoichiometric ratio of soil enzymes,vector length(VL),and vector angle(VA),the relative nutrient limitation to soil microorganisms and the key regulatory factors were explored.Important findings The results showed that litter addition increasedβ-N-acetyl-glucosaminidase and acid phosphatase(ACP)activities.The addition of litter significantly increased VL and VA in the order of M.macclurei>L.formosana>P.massoniana.Litter addition could change the status of nutrient limitation to soil microorganisms,with the degree of changes being related to the quality of litter.Compared with the addition of litter alone,the addition of both litter and P significantly increased the content of available P,and reduced ACP activity and VA,suggesting that P addition could help alleviate P limitation to soil microorganisms under the input of litter.Redundancy analysis results showed that the soil carbon/nitrogen ratio,dissolved organic carbon content,and available P content were the main factors affecting enzyme activities and their stoichiometry.In conclusion,our study found that the response of soil microbial nutrient limitation to litter input in subtropical forest was not only affected by litter quality,but also regulated by soil P availability.This study provides a theoretical reference for the response of microbial nutrient acquisition strategies to different litter inputs and P additions in subtropical forests under future climate change,and is conducive to improving our understanding of the soil biogeochemical cycling in subtropical low P forest ecosystems.