Evaluation of Rock Desertification Restoration Model in Jianshui County, Yunnan Province

XIAO Linying1,2,3, WU Xiuqin1,2,3,†

1. School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083; 2. Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing 100083; 3. Yunnan Jianshui Desert Ecosystem National Positioning Research Station, Jianshui 654399; † Corresponding author, E-mail: wuxq@bjfu.edu.cn

Abstract Based on Landsat TM data from 1992 to 2017, the second-class survey data of Jianshui County forest resources and the monitoring data of rocky desertification in Yunnan Province, with Mann-kendall mutation analysis and trend analysis, the temporal and spatial variation characteristics of vegetation and the restoration of vegetation in different rocky desertification restoration models in Jianshui County of Yunnan Province in the past 25 years were discussed. The study found that during the 25 years, the vegetation cover of Jianshui County showed an overall upward trend with an average growth rate of 0.065%/10a. Since 2008, the growth rate increased from 0.077%/10a to 0.475%/10a. The area of vegetation cover in Jianshui County showed an increasing trend, no significant change, and the proportion of reduction trend was 55.32%, 34.44% and 10.24% respectively. For different restoration models, within the restoration time range of ten years, there was not much difference in the effect of vegetation restoration under the pure ecological forest mode and the mixed ecological forest mode. Within the restoration time range of 25 years, the mixed ecological forest mode vegetation restoration rate was obviously better than pure ecological forest restoration mode, and the advantages were mainly displayed in the later stage of restoration. In terms of species selection of pure ecological forest model, broad-leaved forests and alders had better restoration effects in the short term; in the long run, Yunnan pine and Che sang-tzu were better restoration species. In the mixed ecological forest model, the coniferous mixed forest restoration rate was the best both in the range of

建水县隶属云南省红河哈尼族彝族自治州(图1 (a)), 地理坐标为102°33′18″—103°11′42″E, 23°12′42″ —24°10′32″N。全县南北长 107 km, 东西宽58 km,面积为3789 km2, 山区和半山区占89%。地势南高北低(图 1(b)), 境内河流分属南盘江水系和红河水系。建水县属南亚热带高原季风气候, 四季不明显,干湿季分明, 雨热同季, 夏天酷暑, 冬无严寒, 四季温暖, 少雨干旱。坝区年平均气温为18.5℃ , 最高达 19.3℃(1981 年), 最低为17.7℃(1971 年), ≥0℃的有效积温为3126.21℃。年平均降雨量约为 800 mm, 全年降雨的80%集中在5—10月, 冬春季较干旱。由于喀斯特地貌区土层薄, 降水下渗快, 水土保持能力差, 加上不合理的土地利用方式, 导致建水县石漠化情况严重。

2 数据来源与研究方法2.1 数据来源

本研究所用数据主要获取自美国地质调查局(United States Geological Survey, USGS)的1992— 2017 年每年 4 — 9 月 Landsat TM/ETM+系列数据(https://earthexplorer.usgs.gov/), 空间分辨率为30 m ×30 m, 共计26期, 进而获得基于像元的归一化植被指数(normalized difference vegetation index, NDVI),用于表征当年的植被覆盖状况。石漠化分布数据及治理模式数据来自建水县2006年森林资源二类调查数据及2005和 2011年云南省石漠化监测数据。

2.2 研究方法2.2.1 NDVI 回归分析

本文采用基于像元的一元回归方程, 利用1992

(6) (7)

UFK为标准正态分布, 是由时间序列{xi}计算得出的统计量序列。

按时间序列x的逆序序列xn, xn−1, …, x1重复上述过程, 同时令UBK = −UFK (k = n, n − 1, …, 1)。分别将UFK和 UBK曲线以及显著性水平线绘在同一个图上, 若 UFK 和 UBK值大于 0, 表明序列呈上升趋势, 小于0则呈下降趋势。当超过临界直线时, 表明上升或下降趋势显著, 超过临界线的范围确定为突变的时间区域。如果UFK和 UBK两条曲线出现交点, 且交点在临界线之间, 那么交点对应的时刻便是突变开始的时间。

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