Abstract:
Net primary productivity (NPP) of vegetation is one of the important indicators of a regional ecosystem showing whether it is healthy and degrading. The 2000-2010 data of NPP and land use were cited for analysis of, spatial pattern of vegetation degradation in the Beijing-Tianjin-Hebei region and its human factors, by means of trend analysis, superposition analysis and significance test. Results show that:(1) NPP of the study area varied in the range of 400-700 g·m
-2·a
-1 in the past years, with high values distributed mainly in the Yanshan Mountains, the Taihang Mountains and the east piedmont plain of the Taihang Mountains, and low value in the grassland region northwest of, the eastern coastal zone of the study area and saline-alkali land of the Jidong Plain. (2) During the 11 years, 59.214% of the Beijing-Tianjin-Hebei area has witnessed declining of the vegetation NPP, and the decline was particularly significant or ultra-significant in 10.050% of the area. In part of the study area, vegetation degradation tended to apparent. The area with vegetation degraded reached 21 545.07 km
2, of which 5 775.66 km
2 fell into the category of severe degradation, 8 168.18 km
2 into the category of moderate degradation and 7 601.23 km
2 into slight degradation. Vegetation degradation in the study area exhibits a feature of clustering in spatial distribution, of which there are two examples; One is a band of contiguous patches along the east piedmont of the Taihang Mountains and the other is the circle around the Beijing-Tianjin-Tangshan metropolitan area. (3) There are three main human factors driving variation of the vegetation degradation pattern in the Beijing-Tianjin-Hebei region. 1) Sprawling of cities (towns). The correlation coefficient of the area of newly built cities with the area of severe, moderate and mild vegetation degradation is 0.897 9, 0.783 5 and 0.686 9 (
P<0.05), respectively; 2) Density of regional road network. It affects the pattern and degree of vegetation degradation in the region. Vegetation degradation declines in degree from the important traffic line as the core to its flanks. And 3) Regional economic development strategies and industrial layout, which directly affects spatial pattern of the vegetation in the region.