不同土壤类型桉树人工林植物与土壤水土保持功能协同演变机制

Eucalyptus, as a fast growing tree species, has been widely cultivated in south China. It generates a significant implication to ecosystem services. And soil and water conservation is a key role of forest ecosystem. The influence of soil types and the growth and development of Eucalyptus plantation in soil and water conservation should never be neglected in the previous researches. Four main soil types (lateritic red soil, red soil, yellow soil, and limestone soil) and five age classes (i.e., young, middle-aged, near-mature, mature, and over-mature forest) are chosen to build 60 Eucalyptus plantation plots in Guangxi Province, which is the key distribution area of Eucalyptus plantation in China. Based on the comprehensive investigation, the research intends to analyze the differences of community structure, diversity, productivity, soil water retention property, soil penetrability, soil erosion resistance, soil physical-chemical properties, and soil microorganism character along the growth and development of Eucalyptus plantation. Principal component analysis (PCA) and canonical corresponding analysis (CCA) are applied to find out the major factors of influencing soil and water conservation functions of Eucalyptus plantation, and to show interaction relationships between groups of vegetation, soil and water conservation functions, soil physical-chemical properties, soil microbe, and litter. Detrended canonical correspondence analysis (DCCA) is used to demonstrate soil and water conservation functions along the growth and development of Eucalyptus plantation. Variation partitioning quantifies the contribution rates of each group to soil and water conservation functions. The research finally aims to reveal the synergistic and evolutive mechanism between vegetation, soil quality and soil and water conservation functions of Eucalyptus plantation. This would provide guide for ecosystem service assessment and sustainable management of Eucalyptus plantation.

桉树林作为我国南方重要的森林，其速生和广泛种植的特点对生态系统服务功能产生了重要的影响，水土保持是森林生态系统的关键作用，土壤类型差异和林分生长发育对水土保持功能的影响不容忽视。本项目在广西区选择4种主要土壤类型下桉树人工幼龄林、中龄林、近熟林、成熟林、过熟林5个林龄阶段，建立60块标准地。基于全面系统调查，分析不同林龄阶段桉树人工林群落结构、多样性、生产力、土壤持水性、渗透性、抗蚀性和土壤理化性状、微生物性状的差异，用主成分分析、典范相关分析等方法找出影响桉树人工林水土保持功能的主要因子，揭示植被、土壤水土保持功能、土壤理化性状、土壤微生物性状、凋落物各集团因子之间的相互关系，用除趋势典范对应分析表征水土保持功能随桉树生长的变化，用因子分离分析量化各集团因子的贡献率，揭示桉树人工林植物、土壤质量与水土保持功能的协同演变机制，为桉树人工林生态系统服务功能评价和持续管理经营提供科学依据。

桉树林作为我国南方重要的人工用材林，其速生和广泛种植的特点对生态系统服务功能产生了重要影响。本项目通过开展不同林龄桉树人工林植被群落、土壤理化性状、土壤微生物性状、生物量及水土保持功能等相关问题的研究。获得如下结论： .（1）桉树林林下灌木幼林龄丰富度指数最高，在林龄间差异不显著，均匀度和香农-威纳指数先增大后减小。林下草本近熟林的丰富度指数和香农威-纳指数最高，随林龄呈先增后减变化。林下Jaccard 相似系数随林龄增大逐渐减小趋势，中林龄和近熟林共有种数最多。.（2）桉树林土壤容重、TC、TK、TN、AN随林龄增大呈先增后减的趋势，TP随着林龄的增大先增后减又增，AP和AK呈减少的趋势。土壤矿质成分中SiO2含量占绝对优势，其次是Al2O3和Fe2O3。桉树林土壤水分含量无论在什么时间都具有较弱的时间稳定性，土壤含水率的空间模式在观测时间上的相似性较弱。.（3）根据化学计量比关系得到，P是桉树过熟林生长的限制元素，N是幼林龄、中林龄、近熟林和成熟林生长过程限制元素。N重吸收率随林龄增加先减后增趋势，P重吸收率随林龄增加而增加，且N重吸收率稍大于P重吸收率。.（4）广西不同林龄桉树林土壤微生物数量表现为：近熟林>过熟林>幼林龄>中林龄>成熟林。不同林龄土壤微生物碳源利用能力表现为：过熟林>成熟林>近熟林>中林龄>幼林龄。主要利用的碳源是碳水化合物类，酚酸类和胺类碳源利用最少。.（5）主成分分析得到Al2O3、真菌、TP、TN、TC、TK、MBC、放线菌等因子是影响桉树生长的主控因子。耦合度和耦合协调度模型分析表明不同林龄均属于土壤损益型或滞后型，应加强桉树林土壤管理，合理施肥。.（6）树干是桉树人工林乔木层碳、氮、磷的主要储存库，土壤层是桉树人工林生态系统的主要碳、氮、磷储存库，集中了生态系统60 % 以上的碳储量和90 % 以上的氮、磷储量。