海南岛自然保护区对土壤保持服务功能的保护效果

自然保护区建设是保护生态系统服务的重要手段,在防治土壤侵蚀和维持生态安全方面具有不可替代的作用。以1988年、1998年和2008年3期遥感影像为基础,分析海南保护区对土壤保持功能的长期保护效果,探讨引起保护区土壤保持功能变化的影响因素。结果表明:(1)海南岛保护区内部平均单位面积土壤保持量是1951.59 t hm-2a-1,分别是区外0—5、5—10km和海南岛全省平均水平的2.4、3.2、2.9倍,保护区在土壤保持功能的保育方面发挥着重要作用;(2)在时间尺度上,1988—2008年保护区内外土壤保持功能呈现不同程度的退化趋势,其中保护区外围退化程度显著高于保护区内部(P0.05),后10年的退化程度显著高于前10年(P0.05);(3)从驱动因素上看,1988—2008年经济发展、人口增加和耕地扩张是影响保护区土壤保持功能退化的主要因素,其中在前10年,土壤保持功能与单位面积地区生产总值、单位面积第一产业生产总值、人口密度和耕地比例呈显著负相关(P0.05),而在后10年,土壤保持功能与单位面积地区生产总值、人口密度和耕地比例呈显著负相关(P0.05),由此,应权衡土壤保持功能保护与人为活动的关系,实现生态环境保护与社会经济的协调发展。

Evaluating the effectiveness of nature reserves in soil conservation on Hainan Island

Soil conservation is one of the most important regulating functions of ecosystems. However, it has been negatively affected by climate change and human activities. Hainan Island harbors the most extensive primary tropical rainforest in China. Vast areas of these natural forests have been converted into commercial plantations in the last few decades. Increasingly, it is becoming apparent that nature reserves (NRs) play a key role in ecosystem services and are vital for prevention of soil erosion and upkeep of ecological balance. However, little is known about their effectiveness due to the lack of systematic planning and spatial data on their extent and boundaries. Evaluating the effectiveness of existing NRs in the preservation of soil conservation function is an urgent task. Here, using satellite images from 1988, 1998, and 2008, we evaluated the effectiveness of NRs in maintaining soil conservation function on the Hainan Island. Additionally, we analyzed the main driving forces involved in soil conservation that have changed during the last two decades. Our results showed that:(1) The average soil conversation capacity per unit area in NRs was 1951.59 t hm^-2 a^-1, which was 2.4 and 3.2 times larger than the average capacity registered 0-5 km and 5-10 km, respectively, away from the NRs and 2.9 times larger than the average capacity for the entire Island. Thus, NRs are critical for the maintenance of soil conservation function. (2) In the last two decades (1988-2008), soil conservation function showed a degradation trend inside and outside the NRs. Moreover, the degree of degradation outside NRs was significantly higher than inside NRs (P < 0.05), and it was significantly higher in the last 10 years of the studied period than in the first 10 years of the same period (P < 0.05). (3) From 1988 to 2008, economic development, population explosion, and expansion of cultivated land might have impaired soil conservation properties of the vegetation. Indicators such as gross regional product per area, population density, and area ratio of cultivated land were negatively correlated with soil conservation capacity (P < 0.05). Furthermore, in the first 10 years of the studied period, in addition to these factors, gross domestic product of the primary industry per area was also negatively correlated with soil conservation capacity (P < 0.05). Thus, tradeoffs should be made between protection of soil conservation function and human activities in order to attain coordinative development between eco-environmental protection and social economy.