人为干扰对典型草原土壤碳密度及生态系统碳贮量的影响

The Impacts of Human Disturbances on Soil Carbon Density and Ecosystem Storage of Carbon of Typical Steppes

为了了解不同人为干扰形式对典型草原碳贮量的影响，对采取了不同干扰形式（包括开垦、放牧、禁牧2年、禁牧7年和禁牧17年）的典型草原试验样地的土壤碳密度及总碳贮量进行了研究。研究结果表明，0—20cm深土层土壤碳密度在不同干扰之间表现出明显差异（F=78．702，P〈0．0001），其由大到小的排列顺序为禁牧17年〉禁牧7年〉禁牧2年〉放牧〉开垦，分别为4．47、4．23、4．01、3．7和2．27kg／m2；0～50cm土层土壤碳密度除开垦明显低于干扰形式以外，几种干扰间没有表现出明显差异；人为干扰对土壤碳密度的影响主要表现在土壤的表层（0—20cm），对深层土壤的影响不明显。不同干扰形式下碳贮量中都以土壤碳库占有最大的比重，一般在86％～93％之间；根系所占比重在6％～13％之间；植物地上部分所占比重与枯落物大致相当，一般低于1％（开垦除外）。基于0—20cm土壤碳密度计算的总碳贮量分别为5．74kg／m2（禁牧17年）、5．22kg/m2（禁牧7年）、4．83kg／m2（禁牧2年）、4．39kg／m2（放牧）、2．67kg／m2（开垦），不同干扰类型间达到了显著差异（F=8．711，P〈0．01）；基于0—50cm土壤碳密度计算的总碳贮量也表现出相同的变化趋势。本研究得出如下结论：人为干扰对典型草原土壤碳密度及总碳贮量具有明显影响，即开垦和放牧导致土壤碳密度和总碳贮量明显下降，而禁牧则可以提高土壤碳密度及碳贮量。因此，从提高碳贮量的角度来看，应该严格禁止典型草原的开垦行为，鼓励实行适当的禁牧制度。

In order to understand how different human disturbances influence the carbon storage of typical steppes, the soil carbon density and total carbon storage of typical steppes plots under different human disturbances （ including cultivation, grazing, banned-grazing for 2 years, 7 years and 17 years） were investigated. The result shows that for the soil Carbon density of soil layer of 0 -20 cm, there is significant difference among different human disturbances （F = 78. 702, P 〈 0. 000 1 ）, and they are ranked in a descending order as follows ： banned-grazing for 17 years （4. 47 kg/m2 ） 〉 banned-grazing for 7 years （4.23 kg/m2 ） 〉 banned-grazing for 2 years （4. 01 kg/m2） 〉grazing （3.7 kg/m2） 〉cultivation （2.27 kg/m2）. For that of soil layer of 0 - 50 cm, there is no significant difference among the other different disturbances, except cultivation with a lower figure than others. And, the influences of human disturbances on soil carbon storage mostly happen in the upper layer of soil （0 - 20 cm） rather than deep soil. There is a minus linear correlation between the soil carbon density and the depth of soil. For the total carbon storage of typical steppes under different human disturbances, the soil carbon bank is the greatest, accounting for 86% -93% of the total carbon storage, the root carbon bank accounting for 6% - 13%, and both litters and aboveground of plant, less than 1% （except for the situation of cultivation）. The total carbon storage based on the soil carbon density of 0 -20 cm is 5.74 kg/m2 for banned-grazing for 17 years, 5.22 kg/m2 for banned-grazing for 7 years, 4.83 kg/m2 for bannedgrazing for 2 years, 4. 39 kg/m2 for grazing, 2. 67 kg/m2 for cultivation, and there is significant difference among them （F = 8.711 ,P 〈0. 01 ）. And, there is a similar situation for the total carbon storage based on the soil carbon density of 0 - 50 cm. It is concluded that the soil carbon density and the total carbon storage of typical steppes are influenced by human disturbances distinctly, namely, cultivation and grazing cause decrease in the soil carbon density and the total carbon storage significantly, and banned-grazing causes increase in both of them. Hence, so far as the carbon storage improvement, cultivation should be prohibited strictly, and the reasonable regime of banned-grazing should be encouraged in the management of typical steppes.