No abstract

As the primary component of urban green space, parks play an important role in improving local environments and quality of life for city inhabitants. To date, much research on urban park plant community characteristics has been conducted worldwide, but studies focusing on differences across altitudes have been rare. Here, we have investigated fractional vegetation cover (FVC), plant species diversity, plant species composition, and plant life-form types along altitude gradients within four urban parks (Jincheng, Renshoushan, Baitashan, and Lanshan) in Lanzhou city (China) by field sampling and remote sensing. Spatial variations in plant community characteristics at different elevations, as well as their ecological, social, and integrated service levels, were analyzed using combined methods of remote sensing interpretation, mathematical statistics, and service function assessment. The results showed that: (1) spatial variations in plant communities along elevation gradients exhibited a distinct regional differentiation between parks; (2) Lanshan Park had the lowest FVC (43.6%) and plant species diversity (59 species), and these two parameters exhibited the most dramatic spatial change as elevation increased; the opposite phenomenon occurred in Renshoushan Park (FVC of 56.6%; 81 species); (3) the differences in the natural service level of the plant community were smaller for the social and integrated service levels. The highest natural service level occurred in Renshoushan Park, while Jincheng Park had the highest social and integrated service levels; the smallest values occurred in Lanshan Park. We conclude that scientific park management is urgently required to ensure the safety and sustainable development of the local urban ecosystems and to improve the ecological and social service levels of the individual urban parks, especially Lanshan Park. These findings also provide key insights to improve urban park communities and service levels in similar mountainous, semi-arid zones.

The Kaxgar River Basin, a key section of the Tarim River Basin, is a typical ecologically fragile region that has undergone rapid changes to its spatial patterns over the preceding few decades. In particular, the expansion of salinized land has posed a severe threat to ecological restoration and economic development. This study monitored the rates and patterns of land use and land cover (LULC) changes in the plain area of Aketao County in the middle reaches of the Kaxgar River Basin. Five Landsat images (captured in 1990, 1998, 2002, 2013, and 2018) were divided into seven LULC types: built-up land, cultivated land, woodland and grassland, light-moderate salinized land, heavy salinized land, water areas, and bare land. Subsequently, their dynamic processes were analyzed. The results revealed that in 1990, the dominant LULCs were cultivated land, woodland and grassland, and bare land. Throughout the study period (from 1990 to 2018), the coverage of built-up land, cultivated land, bare land, water areas, and light-moderate salinized land increased; by contrast, that of the other LULC types decreased. The most marked LULC changes were the expansion of light-moderate salinized land (by 6.2% of the study area) and the shrinkage of woodland and grassland (by 9.4% of the study area). Almost all the analyzed LULC types underwent conversion to other types; such conversion occurred most frequently between 1998 and 2018. The conversions of woodland and grassland into cultivated land and light-moderate salinized land were the most notable phenomena. Another highly evident change was the conversion of heavy salinized land into bare land. These results revealed that the expansion of salinized land and the shrinkage of woodland and grassland in the study area were the most severe environmental changes. Therefore, ecological protection and salinization control are urgently required to enable local economic development while not exceeding the environmental carrying capacity and ensuring the safety of the “green corridor” in the lower reaches of the Kaxgar River Basin.