异龄复层混交对马尾松人工林土壤团聚体碳组分和转化的影响

Effects of multi-layer and mixed-age forestmanagement of Pinus massoniana plantations on carbon components and transformation of soil aggregates

关键词:  马尾松人工林, 土壤团聚体, 有机碳组分, 土壤酶活性, 近自然化经营

Key words:  masson pine(Pinus massoniana)plantations, soil aggregates, organic carbon components, soil enzyme activities, close-to-nature forest management

摘要:

复层混交种植的近自然化经营是我国亚热带地区最常用的营林模式之一,但目前其对土壤有机碳(SOC)的积累及其稳定性的影响仍不明确。为探讨该营林模式对土壤碳组分及其转化的影响,该文选取南亚热带复层混交经营的马尾松近自然林(CP)作为研究对象,并以相邻未改造的马尾松纯林(PP)作为对照(CK),重点探究异龄复层混交后原土和不同粒径土壤团聚体的稳定性、有机碳组分、微生物生物量和酶活性等的变化规律及其之间的关系。结果表明:(1)复层混交后表征土壤团聚体稳定性的平均重量直径(MWD)显著提高; 与PP相比,CP原土和不同粒径土壤团聚体的SOC、高度不稳定有机碳(LOC)、中度不稳定有机碳(IOC)、惰性有机碳(ROC)、土壤碳氮比(C/N)、微生物生物量碳和氮(MBC和MBN)、微生物呼吸(MR)、β-葡萄糖苷酶(BG)、纤维二糖水解酶(CB)、N-乙酰-葡萄糖苷酶(NAG)和酚氧化酶(PO)均显著提高,而其MBC/MBN和微生物代谢熵(qCO₂)却显著降低。(2)几乎所有原土和土壤团聚体的SOC、总活性有机碳(LOC+IOC)、ROC和ROC数(RCI)均与MWD呈显著或极显著正相关。(3)SOC及其组分的变化主要来自于土壤理化性质、微生物性质和植物性质三者之间的交互作用,而复层混交后导致的凋落物碳氮比(C/N_LF)和土壤全氮(TN)的显著变化是驱动SOC及其组分发生改变的最关键因子。研究认为,复层混交是一种有效促进马尾松人工林SOC及其稳定性组分形成的近自然经营模式,该研究结果为提高马尾松人工林的土壤质量和稳定性提供了科学依据。

Abstract:

Close-to-nature forest management of multi-layer mixing is one of the most common forest conversion patterns in subtropical regions of China, but its effects on soil organic carbon(SOC)accumulation and stability are still unclear. In this study, the close-to-nature plantations of masson pine(Pinus massoniana)(CP)by multi-layer mixed management in the southern subtropical region were selected as the research object, and the adjacent pure plantations of masson pine(PP)without modification were taken as the control(CK). And then we investigated the stability, organic carbon component, microbial biomass and enzyme activity of soil aggregates with different particle sizes and their relationships. The results were as follows:(1)Mean weight diameter(MWD), which was used to characterize the stability of soil aggregates, increased significantly after near-natural modification. Compared to PP, SOC, labile organic carbon(LOC), intermediate organic carbon(IOC), recalcitrant organic carbon(ROC), soil C/N, microbial biomass carbon and nitrogen(MBC and MBN), microbial respiration(MR), β-glucosidase(BG), cellobiohydrolase(CB), N-acetyl-glucosaminidase(NAG)and phenol oxidase(PO)were significantly increased, but the MBC/MBN and microbial metabolic quotient(qCO₂)were significantly decreased.(2)The SOC, total organic carbon(LOC+IOC), ROC and ROC index(RCI)of in soils or most soil aggregates were significantly positively correlated with MWD.(3)The change of SOC content and its components mainly resulted from the interaction among soil physical and chemical, microbial and plant properties. Furthermore, the significant changes of litter carbon to nitrogen ratio(C/N_LF)and soil total nitrogen(TN)caused by masson pine with multi-layer mixed forest management were the primary drivers of differences in SOC content and its components. Our findings indicate that that the close-to-natural forest management model of multi-layer mixing is an effective management measure to improve SOC and its stability components, and so as to promote masson pine plantations to sequester more and more stabilized SOC in the subtropical region of China.