Driving Factors of Recent Vegetation Changes in Hexi Region, Northwest China Based on a New Classification Framework

Abstract

Since other factors (soil properties, topography, etc.) under natural conditions are relatively invariant over one or two decades, climate variables (precipitation and temperature) and human activities are the two fundamental factors driving vegetation changes in global or large-scale areas. However, the combined effects of either single climatic factor and human activities on vegetation changes and the role of human activities itself in a specific region has not been fully discussed. In this study, the Hexi region, a typical dryland consisting of three inland river basins in northwest China was selected as a case area. A new classification framework combining Pearson correlation analysis and residual trend approach was proposed to assess their individual and conjoint contributions of climate variables and human activities in areas of significant vegetation changes. Our results indicated that most of vegetation covered areas in the Hexi region experienced significant changes during the period 2001−2017, and vegetation improvements were widespread except the interior of oases; significant changes in vegetation caused by human activities, precipitation, the interactions of precipitation and human activities, temperature, the interactions of temperature and human activities, the interactions of temperature and precipitation, and the interactions of the three factors accounted for 50.46%, 16.39%, 19.90%, 4.33%, 2.32%, 2.11%, and 4.49% of the total change areas, respectively. Generally, the influence of temperature was relatively weaker than that of precipitation, and the contributions of the interactions of climate variables and human activities on vegetation changes were greater than that of climate contributions alone. Moreover, the results of various investigations, according to the trends and the time of vegetation changes, indicate that decreasing trends of the normalized difference vegetation index (NDVI) in the Hexi region were chiefly attributed to the adjustments of agricultural planting structure while the comprehensive treatment programs implemented in river basins supported a large proportion of vegetation improvements.

Rice Paddy Soil Seedbanks Composition in a Mediterranean Wetland and the Influence of Winter Flooding

“…Cyperus difformis was the most frequent (100%) and abundant species and the one that contributed the most to the seedbank of the Valencian paddies. CYPDI appears in most seedbanks of other paddy areas around the world [4,36,38]. Seed production and its viability over time are factors of great importance in the composition of the seedbank [8], with species that produce small seeds generally being more abundant.…”

“…EBK is a geostatistical interpolation method that has been used in several studies on vegetation and soils because it adjusts and reduces the standard error more precisely than other kriging methods. In addition, it reduces the effect that irregular sampling can produce over outcomes [34][35][36][37][38].…”

46-Year (1973–2019) Permafrost Landscape Changes in the Hola Basin, Northeast China Using Machine Learning and Object-Oriented Classification

“…All these anthropic expansions are fragmenting the landscape and ecosystem and disturbing the wildlife by blocking their migration routes [52]. Likewise, human activities are contributing to 50.46% of vegetation changes in Northwest China, while the climate factors (e.g., precipitation and temperature), only 16.39% and 4.33%, respectively [27]. At the same time, on the northeastern QTP, climate warming is the main driver for permafrost degradation and the shrinking of thermokarst lakes and ponds [53].…”

“…Mapping and monitoring of LUCC in Northeast China are vital for regional sustainable development, land planning, and environmental management. Furthermore, the combined effects of climate change and human activities on landscape changes in a specific region are insufficiently assessed [27]. This study aims at detecting the landscape changes over the last 46 years (1973-2019) in the Hola Basin, Northeast China, as jointly induced by climate change and human activities.…”

Drivers and Environmental Impacts of Vegetation Greening in a Semi-Arid Region of Northwest China since 2000

“…Among these, the dynamics of vegetation in semi-arid regions are of particular interest [15][16][17], for several reasons. First, ecosystems of semi-arid regions are easily affected by climate change and human interference [18][19][20][21][22][23]. Second, because vegetation in semi-arid landscapes has large interannual variability compared to in other systems, it is especially important to understand these dynamics in order to clarify their roles in the global carbon cycle [24,25].…”