喀斯特生态环境治理下土壤保持功能对石漠化的响应机制

喀斯特地区土壤保持功能是衡量石漠化生态治理成效的重要手段之一,基于InVEST模型,利用"3S"技术对2005、2010、2015年的关岭-贞丰花江示范区的石漠化进行解译,研究石漠化与土壤保持量两者的响应机制。结果表明:(1)2005～2015年石漠化程度总体减缓,面积由3 773.56 hm~2减少至3 474.23 hm~2,土壤保持总量相继上升,从29.29万t提高至37.29万t,2005～2010年单位面积土壤保持增量集中在6～30 t·hm~(-2)·a~(-1),后五年增量在0～6 t·hm~(-2)·a~(-1)。(2)由于土地利用方式、坡度、土层厚度等差异,土壤保持功能并未呈现简单式下降,而是表现为强度中度、轻度潜在、非喀斯特无石漠化。其中轻度与潜在差值最大,可达5.53 t·hm~(-2)·a~(-1),说明了潜在石漠化是今后治理的重点。(3)2005～2010年石漠化恢复型土壤保持增量为10.27 t·hm~(-2)·a~(-1),由于土地利用方式的转变以及治理时效性在2010～2015年降低为3.01 t·hm~(-2)·a~(-1)。稳定型石漠化变化土壤保持变化最为平稳,强度石漠化减缓区土壤保持功能上升快,轻度最为平缓,表明了治理期长且需循序渐进。因而,在治理过程中需考虑不同等级石漠化具有的土壤保持功能特性及其恢复的时效性。

Response Mechanism of Soil Conservation Function to Rocky Desertification Under Eco-Environmental Harness of Karst Areas

Soil conservation function is one of the important means of measuring the effectieness of ecological rehabilitation of rocky desertification in karst areas. Based on InVEST model, “3S” technology was used for interpreting rocky desertification in Guanling-Zhenfeng Huajiang Demonstration Area in 2005, 2010 and 2015, and the response mechanism between rocky desertification and soil conservation was studied. The results showed that, from 2005 to 2015, (1) Degree of rocky desertification in the Huajiang demonstration area presented an overall downward trend, and areas of rocky desertification was reducing from 3 773.56 to 3 474.23 hm². Moreover, the overall soil conservation quantities presented an upward trend, rising from 279 900 to 348 100 t. the increasing quantities of soil conservation per unit area, from 2005 to 2010, was concentrated in 6-30 t·hm^-2·a^-1, and in the last five years it slowed within 0-6 t·hm^-2·a^-1. (2) although differences in land-use type, slopes, and soil thickness, soil conservation functions did not show a simple decline at all, but rather: intensity > moderate, mild > potential, non-karst > no rock desertification. Among them, the difference between light and potential is biggest difference up to 5.53 t·hm^-2·a^-1, which indicated that potential rocky desertification is the harness priority in the future. (3) In 2005-2010, the increasing quantities of restoring-type soil conservation of rocky desertification was 10.27 t·hm^-2·a^-1, which was reduced to 3.01 t·hm^-2·a^-1 in 2010-2015 due to the change of land-use type and harness effectiveness. The change of the increasing quantities of stable type soil conservation of rocky desertification maintain the most stable; soil conservation function rises rapidly in intensity-rocky desertification slowdown areas, while mild-rocky desertification area is smoothest, which indicated that the harness period is long and needs to be gradual. Therefore, in the process of harness, it is necessary to consider the soil conservation function of different degree of rocky desertification and the effectiveness of its restoration.