树种差异对东北地区土壤碳截获质、量影响及其形成机制

As the largest afforestration country, the forest C density in China is only half of the world average. Systematic study on species influences on soil C sequestration will benefit the cultivation of high C sink plantation and C sink capacity evaluation of existent forests. In this proposal, plantation forests in the same soil type afforested by typical trees(larch, poplar, ash, Korean pine, scots pine and spruce, etc) in local region of NE China were used as material, and 4 forest farms differing in soil (chernozem,black soil, Baijiang soil and typical dark-brown forest soil) will used as replicates. By using dual control of paired farmland soil and soil in deep layer, the species-induced C sequestration and its vertical distribution were quantified at first. Thereafter, physics-chemically classifying variable soil components(5 parameters,SOC(POM particulate organic matter, S+A sand and stable aggregates, DOC dissolved organic carbon,s+c silt and rSOC resistant soil organic carbon)with different turnover time, NMR-aided measurement of chemical composition of soil C(4 parameters,Alkyl-C,O-akyl C,Aromatic C, Carbonyl C), and determination of fungus-microbial-related C and C mineralization rate(4 parameters,EE-GRSP easily extractable glomalin-related soil protein,and T-GRSP total extractable glomalin-related soil protein, microbial C and C minerlization rate)and N,P fetility parameters were used to quantify the quality difference from tree species. Finally, the driving mechanism for this tree species-induced soil C sequestration were mathematically identified by measuring quality of returning debris from litter and roots(total amount, lignin, N,P, polyphenol content), biomass accumulation rate and allocation pattern to variable organs, and variable soil properties (pH, EC, bulk density, specific gravity, porosity ratio, texture, relative crystallinity of soil minerals as well as functional group differences on soil colloids). Anticipated results will support the tree selection for C sink afforestation and C sink evaluation of existent forests in NE China.

作为造林第一大国，我国森林碳密度仅为世界平均一半，对树种差异影响土壤碳截获的系统研究有助于高碳汇林的培育及现有林碳截获能力评价。本项目以东北地区典型树种(落叶松、杨树、水曲柳、红松、樟子松、云杉等)在相同立地下的人工林为对象，设置重复于4个林场（黑土、黑钙土、白浆化暗棕壤、典型森林暗棕壤），以附近农田和深层土壤为对照，确定不同树种土壤碳截获"量"的差异及垂直分布；通过物理化学分级分离不同周转期的土壤组分5个、核磁共振法化学组成区分(烷基碳；烷氧碳；芳香碳；羧基碳)、测定微生物碳4指标和N、P肥力指标，确定不同林分土壤碳截获"质"的差异；最后通过测定从返还土壤有机物质量(枯枝落叶和根系回归量与木素、N、P、多酚含量)、生物量累积速率与器官间分配以及土壤特性(pH值、电导率、容重、比重、颗粒组成、矿物结晶度和有机物粘附等)多角度阐明上述质、量差异的形成机制，为碳汇林建设及碳截获估计提供支撑。

作为造林第一大国，我国森林碳密度仅为世界平均一半，对树种差异影响土壤碳截获的系统研究有助于高碳汇林的培育及现有林碳截获能力评价。本项目研究结果显示东北地区典型树种对土壤碳截获的影响显著，且在0-60cm土壤的种间差异基本一致，水曲柳、榆树的土壤碳截获能力较强。通过土壤组分分级发现杨桦林沙和团聚体以及难分解组分中具有高出红松林13.1%-40.5%的O-H & N-H 伸缩振动带、O-H弯曲振动带、C=O, COO-和C-H伸缩振动带官能团，也具有更低的石英晶粒尺寸和矿物衍射峰个数，这两个组分是土壤的主体，超过土壤质量的85%，这些组分变化与杨桦林具有更高的土壤碳截获（1.17-1.53倍）有关。阔叶林比针叶林的碳、氮截获分别高出了45%和37%，而更加稳定的微团聚体对这种升高分别贡献了55%和50%。另外，土壤真菌GRSP的化学特征在不同林型及农田存在着一定的差异。对土壤肥力维持而言，鱼鳞云杉和榆树的得分最高，黑皮油松、蒙古栎及杨树的得分最低。追溯土壤碳截获的主要来源（枯枝落叶及根系），我们发现：针叶人工林枯枝落叶及根系的有机碳含量均高于阔叶人工林，但阔叶人工林的枯枝落叶及根系却更加易于分解从而向土壤提供更多的有机物质，表现在：较高的土壤SOC，伴随着低的根系纤维素、根系灰分以及枯枝落叶灰分。