土地利用方式对土壤团聚体稳定性及其结合有机碳的影响

Effect of Land Use Patterns on Soil Aggregate Stability and Aggregate-associated Organic Carbon

弄清退耕还林工程实施后土壤团聚体粒径分布及其有机碳的变化,可为协调区域土地利用和土壤碳库管理提供科学依据.选取成都市退耕还林工程实施中主要造林树种巨桉和水杉人工林,以及马尾松天然次生林和临近坡耕地为研究对象,探讨了土地利用变化对0-20 cm、20-40 cm和40-60 cm不同土壤层次团聚体稳定性及其结合有机碳分配与储量的影响.结果显示:不同土地利用方式下土壤团聚体均以大团聚体(>0.25 mm)的含量在土壤团粒结构中占主导地位,且土壤团聚体中有机碳含量随团聚体粒径的增大而减小.农地转变为林地后,>0.25 mm粒径土壤团聚体含量、团聚体平均重量直径,以及各粒径团聚体有机碳含量均有所增加.其中,团聚体有机碳尤以在0-40cm土层>2mm粒径中的含量增加倍数为大.相比农耕地,马尾松天然次生林、巨桉和水杉人工林各土层土壤>2 mm团聚体有机碳储量占总有机碳储量比例增加了5.96%-47.57%,而<0.053 mm团聚体有机碳储量占总有机碳储量比例减少了0.95%-33.28%.0-60 cm土层土壤团聚体总有机碳储量以马尾松天然次生林最高,而农耕地为最低.研究结果表明该区退耕还巨桉和水杉林增加了土壤团聚体稳定性和有机碳储量,但与天然林次生林相比仍有一定差距.

To provide scientific evidence for coordinating regional land use and soil carbon pool management, it is essential to reveal the distribution of different sizes of soil aggregates and the aggregate-associated organic carbon after the Grain to Green Program. Eucalyptus grandis and Metasequoia glyptostroboides were the main afforestation species in the Grain to Green Program in Chengdu. Four typical land use patterns, namely, E. grandis, M. glyptostroboides plantations, the natural secondary forest of Pinus massoniana and the adjacent slope farmland, were selected as sampling plots to study the effects of land use change on aggregate stability and the aggregate-associated organic carbon in different soil layers （0-20 cm, 20-40 cm and 40- 60 cm）. The results showed that the macro-aggregates （〉 0.25 mm） dominated in the soil aggregate structure. The content of organic carbon in soil aggregates decreased with the increase of aggregate size. The proportion of the 〉 0.25 mm fraction of soil aggregates, the mean weight diameter （MWD） of soil aggregates and the content of organic carbon in soil aggregate size increased after the Grain to Green Program. And the increase of content of organic carbon was largest in the 〉 2 mm fraction of soil aggregates in the top 40-cm soil layer. Compared with those in the slope farmland, the proportion of organic carbon storage in the size of 〉 2 mm soil aggregates increased by 5.96%-47.57% in other land use patterns, but decreased by 0.95%- 33.28% in the size of 〈 0.053 mm soil aggregates. The natural secondary forest of P. massoniana had the highest total organic carbon storage of soil aggregates, while the farmland had the lowest total organic carbon storage among all land use patterns. The results indicated that E. grandis and M. glyptostroboides plantations have higher soil aggregate Stability and organiccarbon storage than the slope farmland, though still lower than the natural forest. Fig 1, Tab 5, Ref33