Assessing Vegetation Cover Dynamics Induced by Policy-Driven Ecological Restoration and Implication to Soil Erosion in Southern China

<div><p>In the aftermath of the severe droughts and floods at the end of the 20th century, the Chinese government launched several ecological restoration projects, including the Natural Forest Protection Program in 1998 and the Grain-for-Green Program in 1999, to promote afforestation and reforestation to reduce surface runoff and consequent soil erosion nationwide. However, it is still unclear how vegetation has changed in southern China since the launch of these programs. In this study, we used the MODIS Enhanced Vegetation Index (EVI) to analyze the vegetation cover dynamics in southern China from 2000 to 2009 and evaluate the resulting effects of controlling soil erosion. Our observations indicate that 5.3% of the study area significantly increased and 0.98% significantly decreased in EVI value (<i>p</i> < 0.05). The spring EVI had largest increase in space. The conversions of croplands on steep slopes to forests resulting from national policies led to significant increases in EVI. The increase in EVI was not driven by annual average temperature and annual precipitation. By referencing ecological restoration statistical data and field observations, we showed that ecological restoration programs significantly improved vegetation cover in southern China. Increase in the area of farmland-converted forestlands has reduced soil erosion based upon monitoring sediment yields at hydrologic stations in the Yangtze River. This study displays the spatial patterns of trend in vegetation growth since the beginning of the 21st century in southern China and highlights the important role of China’s afforestation program.</p></div

The land use and land cover in the area with significantly increased EVI in 2000 (a) and 2009 (b).

<p>The land use and land cover in the area with significantly increased EVI in 2000 (a) and 2009 (b).</p

The land use change of the typical area with the significant EVI increase in 2002 (a) and 2010 (b).

<p>It locates the boundary area among Sichuan, Yunnan and Guizhou.</p

Change in land use area (10⁴ km²) in the area with significantly increased EVI and as a percentage of total area changed (numbers in parentheses), between 2000 and 2009.

<p>Change in land use area (10⁴ km²) in the area with significantly increased EVI and as a percentage of total area changed (numbers in parentheses), between 2000 and 2009.</p

Trends of annual average temperature change (a) and annual precipitation change (b) for the period of 2000–2009 (<i>p</i><0.05).

<p>Trends of annual average temperature change (a) and annual precipitation change (b) for the period of 2000–2009 (<i>p</i><0.05).</p

The elevation map, locations of meteorology and hydrological stations (above) and slope distribution in southern China (below).

<p>The elevation map, locations of meteorology and hydrological stations (above) and slope distribution in southern China (below).</p

Time series of runoff volume (a) and sediment yield (b) measured at seven hydrological stations along the main stream of Yangtze River.

<p>Time series of runoff volume (a) and sediment yield (b) measured at seven hydrological stations along the main stream of Yangtze River.</p

The area of slope cropland and the statistical area of Grain-for-Green Program for the major provinces in southern China.

<p>The area of slope cropland and the statistical area of Grain-for-Green Program for the major provinces in southern China.</p

Time series of averaged EVI in southern China.

<p>Black is for the entire study area, green is for the regions with significantly increased EVI, and red is for regions with significantly decreased EVI.</p

The land use for the area with significantly increased EVI on slopes of 0–15° in 2000 (a) and 2009 (b) and on slopes >15° in 2000 (c) and 2009 (d).

<p>The land use for the area with significantly increased EVI on slopes of 0–15° in 2000 (a) and 2009 (b) and on slopes >15° in 2000 (c) and 2009 (d).</p