Yaxue Luo

Population is the main driver of land-system and environmental change. However, population is usually treated as a variable that only considers the population number, and multi-dimensional population structure is largely ignored. There has been a systematic transition of population structure in the past several decades, including changes in household structure, increasing aging populations, increasing divorce rates, and increasing human migration. All of these changes have direct or indirect impacts on land use and environmental issues. Here, taking China as an example and using statistical analysis, namely the Mann–Kendall trend test and a land-use-transition matrix, we examine the relationship between household dynamics and land-use change in China by examining changes in household structure and land-use changes in China between 1980 and 2020. The results show the following three groups of findings. (1) The number of households increased by 130.95% from 1980 to 2020, while the population only increased by 42.83%; the size of households decreased from 4.41 to 2.62 in China from 1982 to 2020; and the household dynamics varied from province to province, which is affected by urbanization rate and economic development. (2) Birth rates, divorce rates, population aging, and migration all affect household structure, which directly or indirectly affect changes in land-use systems. (3) The changes in China’s land use are interlinked and interact with changes in household structure, which is evident in the increase in Residential land use and the abandonment of arable land. The rising household number increased the area of urban and rural settlement, leading to the fragmentation of cultivated land and the reduction of ecological land. To regulate land-use change for sustainable development, future land-use planning should take into account the effect of household dynamics and should reduce the negative effects of household dynamics on land systems and environmental change.

Population is the main driver of land systems and environmental change. However, the population is usually treated as a variable that only considers the population number, and the multidimensional population structure is largely ignored. There has been a systematic transition of population structure in the past several decades, such as the changing household structure, the increasing aging population and divorce rate, and human migration. All these have direct or indirect impacts on land use and environmental issues. Here, we will take China as an example to examine the relationship between household dynamics and land use change in China by exam-ining changes in household structure and land use change in China between 1980 and 2020. The results show:1) the number of households increased by 130.95% from 1980 to 2020, while the population only increased by 42.83%. The size of households decreased from 4.41 to 2.92 in China from 1982 to 2020. The household dynamics vary from province to province, which is affected by urbanization rate and economic development. 2) Birth rates, divorce rates, population aging, and migration all affect household structure, which directly or indirectly affects changes in land use systems. 3) The changes in China's land use are interlinked and interact with changes in household structure, evident in the increase in residential land use and the abandonment of arable land. The rising household number increased the area of urban and rural settlement, leading to the fragmentation of cultivated land and the reduction of ecological land. To regulate land use change for sustainable development, future land use planning should take into effect of household dynamics, and reduce the negative effects of household dynamics on land systems and environmental change.

For different vegetation types, soil moisture content shows varying characteristics in different seasons and under different precipitation conditions. However, these characteristics have not been extensively analyzed in karst regions of southwest China. In this study, the soil moisture content of four plots of bare land, grassland, shrubland, and forestland was monitored, and the soil moisture content and corresponding meteorological data for each plot were analyzed. The results indicate that the average soil moisture content in grassland was the highest with weak temporal variation and that in bare, shrub, and forest lands soil moisture content was low with moderate temporal variation. The average soil moisture content in bare, grass, and forest lands was higher in the rainy season than in the dry season, whereas in shrubland, the soil moisture content was higher in the dry season than in the rainy season. Increase in soil moisture content during each precipitation event correlated with the rainfall amount. With increasing rainfall amount, soil moisture content in forest and shrub lands increased more than in bare and grass lands. The peak soil moisture time in each vegetation type plot varied and the peak soil moisture time was related to soil moisture content before a rainfall event. Temperature showed a strong negative correlation with soil moisture content for all vegetation cover types in both the dry and rainy season. Wind speed also showed a strong negative correlation with soil moisture content for all vegetation types during the dry season. Relative humidity had a strong positive correlation with soil moisture content in bare, shrub, and forest lands during the dry season as well as in the four vegetation types during the rainy season. These results demonstrate the variations in soil water characteristics across different vegetation types in karst regions of southwest China.