RESUMO
The northwestern Sichuan Plateau is a typical eco-climate sensitive area, where vegetation condition is closely related to climate change. We used the MODIS-NDVI and the meteorological data during 2001-2020 to investigate the change trend of normalized difference vegetation index (NDVI) and the mechanism underlying its responses to climate factors in the growing season of northwestern Sichuan Plateau by using the methods of maximum value composite, geodetector model, trend analysis, and correlation analysis. The results showed that vegetation coverage in northwestern Sichuan Plateau was overall good during the study period. 86.8% of the regional vegetation was stable, 12.6% of the regional NDVI was weakly and continuously increasing, and 0.6% of the regional NDVI was decreasing. The ecological environment of the whole region exhibited a steady and good development trend. The vegetation coverage in the study area exhibited apparent spatial variation with a general tendency of increase from southwest to northeast, as well as obvious variation with elevation. The NDVI rose with elevation below 1350 m, varied slightly from 1350 to 3650 m, dropped from 3650 to 5900 m, with a rapid drop between 4750 to 5900 m. There was almost no vegetation above 5900 m. The NDVI of northwestern Sichuan Plateau was affected by the interactions of natural factors. Thermal factors were the dominant climate factors, including monthly maximum value of daily maximum temperature, monthly minimum value of daily minimum temperature, growing season length, annual mean temperature, mean temperature over the growing season. All these factors were positively correlated with NDVI excepted for monthly maximum value of daily maximum temperature. The response of NDVI to temperature index was higher than that of precipitation index. Under the background of climate warming, extreme temperature warming index played a major role in promoting the growth and improvement of vegetation in northwestern Sichuan Plateau, especially in high-altitude areas.
Assuntos
Mudança Climática , Meteorologia , China , Ecossistema , Estações do Ano , TemperaturaRESUMO
Meteorological disaster is one of the main factors restricting agriculture development in China. It is important to clarify the risk of summer maize agrometeorological disaster for disaster prevention and mitigation. Based on the natural disaster risk theory, we collected meteorological data and maize yield data from 1981 to 2018 in a typical area in the northern mountainous area of Sichuan Basin (Wangcang County). The main disaster-causing factors affecting summer maize production were determined. A comprehensive agro-meteorological disaster risk assessment model for summer maize was constructed in combination with the sensitivity of pregnant environment and vulnerability of disaster bearing to evaluate the agrometeorological disasters risk of summer maize production in the northern mountainous area of Sichuan Basin. The results showed that during the study period, high temperature in mature period, rainstorm in flowering period, rainstorm in mature period, continuous rain in filling period and drought in booting stage were the main agrometeorological disasters affecting the growth and development of summer maize. The agrometeorological disaster risk of maize generally distributed in a southwest-northeast pattern, with the distribution areas of high-risk and higher-risk areas accounting for half of the total area of Wangcang County. The high-risk areas were mainly located in the southwest of the county, which was basically consistent with the high-value areas of hazard-pregnant environment sensitivity. The low-risk areas were mostly concentrated in the western part of county territory, which were also low-risk areas of high temperature in mature period, rainstorm in mature period, and rainstorm in flowering period disasters.
