Assessing the impacts of biogeochemical drivers and land cover changes on vegetation in the Guanzhong Plain urban agglomeration, China

Abstract

Abstract Vegetation is affected by the complex urban environment. Exploring vegetation change trends from an urban-rural gradient perspective can help understand the response of vegetation to urbanization and provide scientific basis for predicting future vegetation change. Based on Landsat data processed in the Google Earth Engine (GEE) environment, Enhanced Vegetation Index (EVI) change in the Guanzhong Plain urban agglomeration from 2000 to 2020 was calculated, and EVI change was analyzed from the perspective of the urban-rural gradient and different city sizes. Then, the impacts of biogeochemical driving factors and land cover changes to the EVI trend were investigated. The results showed that: (1) The EVI trends of the Guanzhong Plain urban agglomeration had a "V"-shaped characteristic along with the urban-rural gradient. The EVI trends for the urban cores (UC), urban new towns (UNT), urban fringes (UF), rural fringes (RF), and rural backgrounds (RB) were 0.0459 ± 0.0080/10a, 0.0347 ± 0.0093/10a, -0.0090 ± 0.0121/10a, 0.0738 ± 0.0075/10a and 0.0817 ± 0.0082/10a, respectively. (2) From the perspective of different city sizes, EVI in the UC, UNT, and UF increased as city size increased. EVI in the UC, UNT, and UF respectively increased from 0.0333 ± 0.0058/10a, 0.0281 ± 0.0077/10a, and − 0.0189 ± 0.0082/10a in small towns to 0.0520 ± 0.0091/10a, 0.0402 ± 0.0120/10a, and − 0.0114 ± 0.0042/10a in megacities. (3) EVI change in the UC was mainly affected by urban biogeochemical driving factors (UBD), and its contribution rate was 51.9%. EVI change in UNT was mainly affected by UBD, background biogeochemical drivers (BBD) and urban expansion or densification (UED), which had contribution rates of 37.2%, 30.7%, and − 29.6%, respectively. EVI change in the UF was mainly affected by UED, and its contribution rate was − 51.9%. EVI change in RF and RB were mainly affected by BBD, with contribution rates of 70.2% and 94.0%, respectively. (4) The contribution rates of UBD in the UC, UNT, and UF generally in-creased as city size increased. The above results indicate that biogeochemical drivers and land cover changes jointly regulate EVI change trends in the urban-rural gradient of the Guanzhong Plain urban agglomeration, which can help assess the impact of complex environmental changes on vegetation changes in urban regions.