湘东丘陵4种林地深层土壤颗粒有机碳及其组分的分配特征

选取湘东丘陵区4种典型母质发育的林地土壤(花岗岩红壤、板岩红壤、第四纪红土红壤、酸性紫色土),分层次采集土壤剖面样品,采用物理分组方法,研究深层土壤颗粒有机碳(POC)及其组分(粗颗粒有机碳CPOC、细颗粒有机碳FPOC)的数量分布和分配比例,探讨POC及其组分与土壤有机碳、质地的关系。结果表明,4种土壤剖面POC储量介于2.63-11.59 t/hm2,以花岗岩红壤最高,其次为板岩红壤,第四纪红土红壤和酸性紫色土相对最低。4种土壤POC占SOC的比例(POC/SOC)介于1.5%-13.9%,花岗岩红壤POC/SOC随剖面加深而升高,板岩红壤和第四纪红土红壤则降低,紫色土POC/SOC在40-60 cm土层达到最大值后迅速降低。在40 cm以下的深层土壤中,花岗岩红壤和紫色土保存有数量可观、比例更高的POC。第四纪红土红壤POC储量相对较少、POC/SOC也在表土层较高。花岗岩红壤POC中以CPOC为主,而紫色土以FPOC为主,板岩红壤和第四纪红土红壤中CPOC和FPOC比例接近。所选4种土壤POC组分中,FPOC数量更能代表SOC数量的变化。SOC储量和质地是影响不同母质土壤POC及其组分分配差异的重要因素,在林地开发利用中也应重视深层土壤(40 cm)中储藏的活性碳组分。

The characteristics of particulate organic carbon and its components in deep soil of

Four types of forest soils derived from various parent materials (red soils derived from granite, slate and quaternary red clay, purple soil) were sampled in eastern hilly region of Hunan Province. The purpose was to study the distributions of particulate organic carbon (POC) and its components of coarse particulate organic carbon (CPOC) and fine particulate organic carbon (FPOC) in different horizons of soil profile, and to analysis the relationships of POC and its components with soil organic carbon (SOC) and soil texture. The results showed that the POC storage ranged from 2.63 t/hm2 to 11.59 t/hm2 in the soil profile, and was higher for red soils derived from granite and slate and lower for red soil derived from quaternary red clay and for purple soil. The proportion of POC to SOC (POC/SOC) varied from 1.5% to 13.9%, and was increased with increasing soil depth for red soils derived from granite whereas decreased with increasing soil depth for red soils derived from slate and quaternary red clay. For purple soil, POC/SOC peaked at 40-60 cm depth and then decreased rapidly. For red soils derived from granite and purple, considerable amounts and high proportions of POC were preserved in deep soil layers beneath 40 cm depth. However, POC storage was small and its proportion was relatively high in the surface soil for red soil derived from quaternary red clay. The component distribution of POC also varied for different soils. Generally, POC was dominated by CPOC for red soil derived from granite and by FPOC for purple soil, but the distributions of CPOC and FPOC were similar for red soils derived from quaternary red clay and slate. The content of FPOC could represent the changes of SOC content. The soil texture and SOC storage were considered to be major controls for the variation of POC and its components across different soil types. The labile SOC fractions stored in deep soil horizons (>40 cm) should also be considered during the soil utilization.