| 土地利用方式对缙云山土壤团聚体稳定性及其有机碳的影响 |
| 摘要点击 3916 全文点击 1900 投稿时间：2014-04-22 修订日期：2014-07-07 |
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| 中文关键词 土地利用方式 土壤团聚体 稳定性 土壤有机碳 缙云山 |
| 英文关键词 land use type soil aggregates stability soil organic carbon Jinyun Mountain |
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| 中文摘要 |
| 土壤团聚体对土壤肥力、质量和土壤的可持续利用等有很大的影响，是水、肥保蓄与释供功能的物质基础. 通过湿筛法，将缙云山林地、撂荒地、果园和坡耕地这4种土地利用方式土壤进行粒径分组，得到大团聚体（>2 mm）、中间团聚体（0.25~2 mm）、微团聚体（53 μm~0.25 mm）以及粉+黏团聚体（<53 μm）的质量分数，测定各粒径团聚体中的有机碳含量，并计算0~60 cm土壤深度内各粒径土壤团聚体的有机碳储量. 结果表明，土地利用方式对土壤团聚体稳定性及其有机碳具有重要影响. 林地的开垦行为会导致大团聚体的破碎化，果园及坡耕地>0.25 mm的大团聚体含量分别为44.62%和32.28%，分别比林地降低38.58%（P<0.05）和91.52%（P<0.05），土壤结构趋于恶化；而坡耕地闲置为撂荒地后，则会促使粉+黏团聚体向粒径大的微团聚体及中间团聚体转化，使土壤结构趋于改善. 在0~60 cm土层内，果园及坡耕地土壤颗粒的MWD（平均质量直径）和GMD（几何平均直径）值均显著低于林地（P<0.05），而坡耕地撂荒后，MWD和GMD值均显著升高（P<0.05），表明林地开垦为果园和坡耕地导致土壤团聚体的稳定性降低，容易被水分散，而坡耕地弃耕撂荒会增强团聚体的稳定性，提高土壤抵抗外力破坏的能力. 4种土地利用方式下各粒径土壤团聚体有机碳含量均随土壤深度的增加而降低. 在0~60 cm的土壤深度内，不同土地利用方式下各粒径土壤团聚体有机碳储量表现为：大团聚体有机碳储量为林地（14.98 Mg·hm-2）>撂荒地（8.71 Mg·hm-2）>果园（5.82 Mg·hm-2）>坡耕地（2.13 Mg·hm-2），中间团聚体有机碳储量为撂荒地（35.61 Mg·hm-2）>林地（20.38 Mg·hm-2）>果园（13.83 Mg·hm-2）>坡耕地（6.77 Mg·hm-2），微团聚体有机碳储量为撂荒地（22.44 Mg·hm-2） >林地（10.20 Mg·hm-2） >果园（6.80 Mg·hm-2） >坡耕地（5.60 Mg·hm-2）；粉+黏团聚体有机碳储量为撂荒地（22.21 Mg·hm-2） >林地（17.01 Mg·hm-2） >果园（16.70 Mg·hm-2） >坡耕地（9.85 Mg·hm-2）. 各粒径土壤团聚体内有机碳储量均为林地和撂荒地高于果园和坡耕地，表明将林地开垦为果园和坡耕地后，将导致各团聚体组分内有机碳的损失，而坡耕地撂荒则有助于土壤有机碳的恢复和截存；林地和撂荒地土壤有机碳主要蓄积在中间团聚体内，而果园和坡耕地则主要蓄积在粉+黏团聚体内，表明在土地利用变化过程中，粒径较大的团聚体有机碳不稳定，更容易发生变化. |
| 英文摘要 |
| Soil aggregates have the important effect on soil fertility, soil quality and the sustainable utilization of soil, and they are the mass bases of water and fertilizer retention ability of soil and the supply or release of soil nutrients. In this paper, in order to study the impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain, we separated four land use types of soil, which are woodland, abandoned land, orchard and sloping farmland by wet sieving method, then we got the proportion of large macroaggregates (>2 mm), small macroaggregates (0.25-2 mm), microaggregates (53 μm-0.25 mm) and silt+clay (<53 μm) and measured the content of organic carbon in each aggregate fraction in soil depth of 0-60 cm and calculated the total content of organic carbon of all aggregates fraction in each soil. The results showed that reclamation of woodland will lead to fragmentation of macroaggregates and deterioration of soil structure, and the proportion of macroaggrgates (>0.25 mm) were 44.62% and 32.28% respectively in the soils of orchard and sloping farmland, which reduced 38.58% (P<0.05) and 91.52% (P<0.05) compared with woodland. While after changing the sloping farmland to abandoned land, which lead to the conversion of soil fraction from silt+clay to large macroaggregates and small macroaggregates, so it will improve the soil structure. MWD (mean weight diameter) and GMD (geometric mean diameter) are important indicators of evaluating the stability of soil aggregates. We found the MWD and GWD in soil depth of 0-60 cm in orchards and sloping farmland were significantly lower than those in woodland (P<0.05), while after changing the sloping farmland to abandoned land, the MWD and GWD increased significantly (P<0.05), which indicated that reclamation of woodland will lead to the decrease of stability of soil aggregates, and they will be separated more easily by water. However, after changing the sloping farmland to abandoned land will enhance the stability of soil aggregates, and improve the ability of soil to resist external damage. The organic carbon content in each soil aggregate of four land use types decreased with the increase of soil depth. In soil depth of 0-60 cm, the storage of organic carbon of large macroaggregates in each soil are in orders of woodland(14.98 Mg·hm-2) >abandoned land (8.71 Mg·hm-2) >orchard(5.82 Mg·hm-2) >sloping farmland (2.13 Mg·hm-2), and abandoned land(35.61 Mg·hm-2) >woodland(20.38 Mg·hm-2) >orchard(13.83 Mg·hm-2) >sloping farmland(6.77 Mg·hm-2) in small macroaggregates, and abandoned land(22.44 Mg·hm-2) >woodland(10.20 Mg·hm-2) >orchard(6.80 Mg·hm-2) >sloping farmland(5.60 Mg·hm-2) in microaggregates, and abandoned land(22.21 Mg·hm-2) >woodland(17.01 Mg·hm-2) >orchard (16.70 Mg·hm-2) >sloping farmland(9.85 Mg·hm-2) in silt and clay fraction. Storage of organic carbon in each aggregate in the soils of woodland and abandoned land were higher than those in the soils of orchard and sloping farmland, which indicated that reclamation of woodland will lead to a loss of organic carbon in each soil aggregate fraction, while after changing the sloping farmland to abandoned land will contribute to restore and sequestrate the soil organic carbon. In addition, it showed that most organic carbon accumulated in small macroaggregate in soils of woodland and abandoned land, while they are in silt and clay in soils of orchard and sloping farmland, indicating that organic carbon in larger aggregates is unstable and is easier to convert during the land use change. |
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