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对贵州省关岭县石漠化地区不同土地利用方式下的土壤团聚体的稳定性、有机碳分布以及大团聚体有机碳矿化进行了研究,探讨了大团聚体对有机碳的保护作用,以期为选择合理的石漠化治理措施提供科学依据。选取了当地主要的4种土地利用方式,分别为水田(水旱轮作)、旱地、花椒林和火龙果林;其中花椒林和火龙果林位于石漠化治理区内。采用湿筛法分离出各级土壤团聚体并结合室内恒温培养法测定原状和破碎大团聚体中有机碳的矿化动态变化,其中大团聚体保护性碳含量为破碎与原状大团聚体有机碳在42 d内累积矿化量的差值。结果表明:土地利用方式对土壤团聚体稳定性具有显著影响。水田土壤团聚体稳定性要明显优于旱地、花椒林和火龙果林,且后3种土地利用方式间也存在显著差异。土壤有机碳也受到土地利用方式的影响,水田和旱地土壤有机碳含量要明显高于火龙果林和花椒林。各粒级团聚体有机碳含量在土地利用方式间具有较大差异,2-5 mm、0.25-2 mm和<0.25 mm团聚体中有机碳含量按水田、火龙果林、旱地和花椒林依次下降,5-8 mm团聚体中有机碳含量则以花椒林最高,其次是水田和火龙果林,旱地最低。但是就各粒径团聚体的有机碳库而言,<0.25 mm团聚体是土壤有机碳的主要载体。花椒林、旱地、火龙果和水田的大团聚体保护性碳含量分别为83.37、78.86、73.81、61.04 mg/kg,其差异表明花椒林土壤大团聚体对有机碳的保护作用最强,其次是旱地和火龙果林,水田最弱。因此,在该地区种植花椒林和火龙果林可以改善其土壤质量,其可能机理是通过增加土壤中大团聚体含量,同时增强大团聚体对有机碳的保护作用。
The stability of soil aggregates, organic carbon distribution and organic carbon mineralization under different land use patterns in rocky desertification area of Guanling County, Guizhou Province were studied, and the protective effect of large aggregates on organic carbon was discussed. With a view to provide a scientific basis for the selection of reasonable control measures for rocky desertification. Four main land use types were selected, which are paddy field (rotation and precipitation), dry land, Zanthoxylum bungeanum and Pterocarpus. Among them, Zanthoxylum bungeanum and Pterocarpus glauca forest are located in the rock desertification control area. The soil aggregates at various levels were separated by wet sieving and the mineralization dynamics of organic carbon in intact and crushed macroaggregates was determined by indoor incubation method. The protective carbon content of macroaggregates was the same as that of crushed and intact macroagglomerates. The cumulative mineralization difference within 42 days. The results showed that land use patterns had a significant effect on the stability of soil aggregates. Soil aggregate stability in paddy soils was significantly better than that in dry land, Zanthoxylum bungeanum and Pterocarya stenpylori forest, and there were significant differences among the latter three kinds of land use patterns. Soil organic carbon was also affected by land use patterns, and soil organic carbon content in paddy field and upland soil was significantly higher than that in pitaya forest and Zanthoxylum bungeanum forest. The organic carbon content of aggregates in different size fractions showed great difference in land use patterns. The contents of organic carbon in aggregates of 2-5 mm, 0.25-2 mm and <0.25 mm were decreased in paddy field, pitaya forest, dry land and Zanthoxylum schinifolium, The content of organic carbon in 5-8 mm aggregates was the highest in Zanthoxylum bungeanum, followed by paddy field and pitaya forest, the lowest in dry land. However, <0.25 mm aggregates are the major carriers of soil organic carbon for organic carbon pools of aggregates of various particle sizes. The protective carbon content of the macroaggregates in Zanthoxylum bungeanum, dryland, pitaya and paddy fields were 83.37, 78.86, 73.81 and 61.04 mg / kg, respectively. The differences indicated that the soil aggregates had the strongest protective effect on organic carbon, followed by Dry land and pitaya, the weakest paddy fields. Therefore, the planting of Zanthoxylum bungeanum and Pterocarya forest in this area can improve the soil quality. The possible mechanism is to increase the content of large aggregates in the soil and enhance the protection of organic carbon by macroaggregates.