生态营林对桉树人工林土壤有机碳组分及酶活性的影响

Effects of Eco-silviculture on Soil Organic Carbon Fractions and Enzyme Activities in Eucalyptus Plantations

关键词:  土壤有机碳组分  颗粒态有机碳  矿物结合态有机碳  生态营林  桉树人工林

Key words:  Soil organic carbon fractions  particulate organic carbon  mineral-associated organic carbon  ecol-silviculture  Eucalyptus plantation

摘要:

探究生态营林对桉树人工林表层土壤有机碳组分和酶活性的影响,以期为桉树人工林固碳增汇和可持续经营提供科技支撑。以生态营林方式桉树纯林、桉树×降香黄檀混交林、桉树×红锥混交林、桉树×望天树混交林为研究对象,以传统营林方式桉树纯林为对照,比较分析不同林分表层土壤有机碳活性组分(易氧化有机碳EOC)、缓效性组分(颗粒态有机碳POC)和稳定性组分(难氧化有机碳NOC、矿物结合态有机碳MAOC)及其占土壤有机碳(SOC)比例的差异,并解析其与土壤理化性质、酶活性及化学计量特征间的关联。结果表明,与传统营林方式桉树纯林相比,生态营林林分均能显著提高SOC、POC、MAOC和NOC含量,也提高了POC和MAOC占SOC比例(P＜0.05),但不同混交林林分间差异不显著。此外,生态营林林分显著提高土壤全氮(TN)含量,以桉树×降香黄檀混交林增幅最大；生态营林林分土壤N-乙酰-β-D-氨基葡萄糖苷酶(NAG)和酸性磷酸酶(ACP)活性增强,亮氨酸氨基肽酶(LAP)活性减弱。冗余分析表明TN、ACP和LAP是土壤有机碳组分及其占SOC比例的主要影响因子。生态营林方式通过提高POC、MAOC含量促进土壤有机碳的稳定性积累,并增强NAG和ACP活性；因具有明显的促进土壤氮素养分积累作用,本研究推荐生态营林方式下桉树与豆科珍贵树种混交林为桉树人工林绿色可持续发展的首选模式。

Abstract:

This study aims to explore the effects of eco-silviculture on the soil organic carbon (SOC) fractions and enzyme activities in the surface soil of Eucalyptus plantations, providing scientific support for carbon sequestration, sink enhancement, and sustainable management of Eucalyptus plantations. The research focuses on pure Eucalyptus plantation, mixed Eucalyptus × Dalbergia odorifera plantation, Eucalyptus × Castanopsis hystrix plantation, and Eucalyptus × Parashorea chinensis plantation under eco-silviculture regime, with pure Eucalyptus plantation under traditional forest management regime as the control. Comparative analyses were conducted on the differences in the active fraction of SOC (easily oxidizable organic carbon, EOC), the slow-acting fraction (particulate organic carbon, POC), and the stable fractions (non-oxidizable organic carbon, NOC, and mineral-associated organic carbon, MAOC) in the surface soil among different stands, as well as their proportions within SOC. The associations between these fractions and soil physicochemical properties, enzyme activities, and stoichiometric characteristics were also examined. The results indicated that compared to pure Eucalyptus plantation under traditional forest management regime, stands under eco-silviculture regime significantly increased the contents of SOC, POC, MAOC, and NOC, as well as the proportions of POC and MAOC within SOC (P < 0.05), although there were no significant differences among the different mixed stand types. Furthermore, eco-silviculture significantly increased soil total nitrogen (TN) content, with the largest increase observed in Eucalyptus × Dalbergia odorifera mixed plantation. Enzyme activities, such as N-acetyl-β-D-glucosaminidase (NAG) and acid phosphatase (ACP), increased in eco-silvicultural stands, while leucine aminopeptidase (LAP) activity decreased. Redundancy analysis revealed that TN, ACP, and LAP were the primary influencing factors of SOC fractions and their proportions within SOC. Eco-silviculture promoted the stable accumulation of SOC by increasing POC and MAOC contents and enhancing NAG and ACP activity. Given its significant role in promoting soil nitrogen accumulation, our study recommends Eucalyptus mixed with valuable leguminous species under ecol-silviculture regimes the preferred model for the green and sustainable development of Eucalyptus plantations.