喀斯特石漠化区林草恢复对土壤团聚体及其有机碳含量的影响

Effects of Forest and Grass Restoration on Soil Aggregates and Its Organic Carbon in Karst Rocky Desertification Areas

为研究喀斯特高原峡谷石漠化治理区林草植被恢复对土壤团聚体的粒径分布,土壤结构稳定性及各粒径团聚体有机碳的影响,以期为喀斯特石漠化治理区土壤结构改善,植被重建,土壤碳库的维持与提高提供理论依据。以贵州喀斯特高原峡谷石漠化治理示范区5种常见林草植被(金银花、火龙果、花椒、荒草地和原生灌木林地)为研究对象,通过湿筛法对土壤团聚体粒径进行分组,对比分析5种林草植被模式下0—40 cm土层垂直剖面各土层土壤中团聚体和有机碳含量的分布规律。结果表明:在0—40 cm土层垂直剖面中,5种林草植被的土壤团聚体在>5,2~5,0.25~2,<0.25 mm 4个粒级中的分布特征,金银花地分别为31.89%,32.85%,28.48%,6.78%;火龙果地为19.11%,32.68%,37.72%,8.49%;花椒地为10.42%,18.39%,57.90%,13.29%;草地为40.38%,20.68%,30.34%,8.61%;原生灌木林为47.04%,17.80%,30.25%,4.91%。水稳性大团聚体(>0.25 mm)含量表现为原生灌木林地(95.09%)>金银花地(93.22%)>火龙果地(91.51%)>荒草地(91.39%)>花椒地(86.71%)。5种林草植被均以大团聚体(>0.25 mm)为主;其中,原生灌木林地大团聚体(>0.25 mm)含量最高,花椒地最低。在整个土壤剖面中,土壤团聚体稳定性指标MWD和GMD均以原生灌木林地较高,说明二者土壤结构较好,稳定性较强。在0—40 cm土层剖面中,各粒级团聚体有机碳含量均随着土层深度的增加而降低,表现出表层富集现象;团聚体有机碳以<0.25 mm粒级含量最高,>5 mm粒级最低。总体而言,原生灌木林地土壤团聚体稳定性较好,原生灌木林地在各层土壤中各粒级团聚体有机碳含量最高。

To study the effects of forest and grass vegetation restoration on soil aggregate size distribution, soil structure stability, and aggregate soil organic carbon in rocky desertification control area of karst plateau, in order to provide theoretical basis for improving soil structure, revegetation, maintaining, and improving soil organic carbon pool, five common forest and grass vegetation (honeysuckle, pitaya, Zanthoxylum bungeanum, wild ground grass, and native shrubbery) in the demonstration area of rocky desertification control in the Karst Plateau of Guizhou were taken as the research object, soil aggregate grain diameter were grouped by wet sieving method, the distribute of aggregates and soil organic carbon content in each soil layer in the vertical profile of 0—40 cm soil layer under five forest and grass vegetation modes was comparatively analyzed. The results showed that in the vertical profile of 0—40 cm soil layer, the distribute characteristic of the soil aggregates in four grain sizes of >5, 2~5, 0.25~2, and <0.25 mm were shown as: honeysuckles 31.89%, 32.85%, 28.48%, 6.78%;pitaya 19.11%, 32.68%, 37.72%, 8.49%;Z. bungeanum 10.42%, 18.39%, 57.90%, 13.29%;wild ground grass 40.38%, 20.68 %, 30.34%, 8.61%;native shrubbery 47.04%, 17.80%, 30.25%, 4.91%. The water-stable macro aggregate content (>0.25 mm) showed as native shrubbery (95.09%)>honeysuckle (93.22%)>pitaya (91.51%)>wild ground grass (91.39%)>Z. bungeanum (86.71%). In general, aggregates in the five forest and grass vegetation were dominated by macro aggregates (>0.25 mm);among them, soil from the native shrubbery had the highest content and soil from the Z. bungeanumhad the lowest content. In the whole soil profile, the soil aggregate stability indicators MWD and GMD of the native shrubbery were higher, which indicated that the soil structure is better and the stability is stronger. In the 0—40 cm soil profile, the organic carbon of each aggregate level decreased with the increase of soil depth, and showed surface layer enrichment. The organic carbon of aggregate showed the highest content in <0.25 mm level, and the lowest content in >5 mm level. Generally speaking, the soil aggregates of native shrubbery land had a better stability, and had the highest content of organic carbon in each layer of each aggregate level.