Response of Plant Climatic Productivity to the Warming and Drying Trend in Huanren in the Past 58 Years

[Objective]The research aimed to study the response of plant climatic productivity to warming and drying tendency in Huanren in the past 58 years.[Method]Based on the temperature and precipitation data in Huanren from 1953 to 2010,using trend analysis,Thornthwaite Memorial model and Mann-Kendall detection method,change characteristics of climate and plant climatic productivity in Huanren were analyzed,and the regression evaluation model between plant climatic productivity and temperature and precipitation was established.[Result]Annual average temperature in Huanren presented a significant upward trend,and its linear tendency rate was 0.29℃/10 a;annual precipitation presented a decreasing trend,and its linear tendency rate was-13.29 mm/10 a;dryness presented a declining trend.The warming and drying trend was obvious in Huanren.Plant climatic productivity presented a significant increasing trend,and its linear tendency rate was 8.39 g/（m2·10 a）.Plant climatic productivity was closely related to precipitation and temperature.[Conclusion]The research could provide basis and reference for the adjustment of agricultural structure and sufficiently playing the advantages of climate resources in Huanren.

Modeling the impacts of drying trend scenarios on land systems in northern China using an integrated SD and CA model

Climate-induced drought has exerted obvious impacts on land systems in northern China.Although recent reports by the Intergovernmental Panel on Climate Change(IPCC) have suggested a high possibility of climate-induced drought in northern China,the potential impacts of such drying trends on land systems are still unclear.Land use models are powerful tools for assessing the impacts of future climate change.In this study,we first developed a land use scenario dynamic model(iLUSD) by integrating system dynamics and cellular automata.Then,we designed three drying trend scenarios(reversed drying trend,gradual drying trend,and acceleration of drying trend) for the next 25 years based on the IPCC emission scenarios and considering regional climatic predictions in northern China.Finally,the impacts of drying trend scenarios on the land system were simulated and compared.An accuracy assessment with historic data covering 2000 to 2005 indicated that the developed model is competent and reliable for understanding complex changes in the land use system.The results showed that water resources varied from 441.64 to 330.71 billion m3 among different drying trend scenarios,suggesting that future drying trends will have a significant influence on water resource and socioeconomic development.Under the pressures of climate change,water scarcity,and socioeconomic development,the ecotone(i.e.,transition zone between cropping area and nomadic area) in northern China will become increasingly vulnerable and hotspots for land-use change.Urban land and grassland would have the most prominent response to the drying trends.Urban land will expand around major metropolitan areas and the conflict between urban and cultivated land will become more severe.The results also show that previous ecological control measures adopted by the government in these areas will play an important role in rehabilitating the environment.In order to achieve a sustainable development in northern China,issues need to be addressed such as how to arrange land use structure and patterns rationally,and how to adapt to the pressures of climate change and socioeconomic development together.

Spatial-temporal characteristics of drought detected from meteorological data with high resolution in Shaanxi Province, China

The spatial pattern of meteorological factors cannot be accurately simulated by using observations from meteorological stations(OMS) that are distributed sparsely in complex terrain. It is expected that the spatial-temporal characteristics of drought in regions with complex terrain can be better represented by meteorological data with the high spatial-temporal resolution and accuracy. In this study, Standard Precipitation Evapotranspiration Index(SPEI) calculated with meteorological factors extracted from ITPCAS(China Meteorological Forcing Dataset produced by the Institute of Tibetan Plateau Research, Chinese Academy of Sciences) was applied to identify the spatial-temporal characteristics of drought in Shaanxi Province of China, during the period of 1979–2016. Drought areas detected by SPEI calculated with data from ITPCAS(SPEI-ITPCAS) on the seasonal scale were validated by historical drought records from the Chinese Meteorological Disaster Canon-Shaanxi, and compared with drought areas detected by SPEI calculated with data from OMS(SPEI-OMS). Drought intensity, trend and temporal ranges for mutations of SPEI-ITPCAS were analyzed by using the cumulative drought intensity(CDI) index and the Mann-Kendall test. The results indicated that drought areas detected from SPEI-ITPCAS were closer to the historical drought records than those detected from SPEI-OMS. Severe and exceptional drought events with SPEI-ITPCAS lower than –1.0 occurred most frequently in summer, followed by spring. There was a general drying trend in spring and summer in Shaanxi Province and a significant wetting trend in autumn and winter in northern Shaanxi Province. On seasonal and annual scales, the regional and temporal ranges for mutations of SPEI-ITPCAS were different and most mutations occurred before the year 1990 in most regions of Shaanxi Province. The results reflect the response of different regions of Shaanxi Province to climate change, which will help to manage regional water resources.

1970-2018年全球整体干旱持续增加

Climate change is expected to introduce more water demand in the face of diminishing water supplies,intensifying the degree of aridity observed in terrestrial ecosystems in the 21st century.This study investigated spatiotemporal variability within global aridity index(AI)values from 1970-2018.The results revealed an overall drying trend(0.0016 yr-1,p<0.01),with humid and semi-humid regions experiencing more significant drying than other regions,including those classified as arid or semi-arid.In addition,the Qinghai-Tibet Plateau has gotten wetter,largely due to the increases in precipitation(PPT)observed in that region.Global drying is driven primarily by decreasing and increasing PPT and potential evapotranspiration(PET),respectively.Decreases in PPT alone or increases in PET also drive global aridification,though to a lesser extent.PPT and increasing potential evapotranspiration(PET),with increasing PET alone or decreasing PPT alone.Slightly less than half of the world’s land area has exhibited a wetting trend,largely owing to increases in regional PPT.In some parts of the world,the combined effects of increased PPT and decreased PET drives wetting,with decreases in PET alone explaining wetting in others.These results indicate that,without consideration of other factors(e.g.,CO_(2)fertilization),aridity may continue to intensify,especially in humid regions.

近五十年中国干旱半干旱区正在变湿吗?

Recently, whether drylands of Northwest China(NW) have become wetting has been attracting surging attentions. By comparing the Standard Precipitation Evapotranspiration Indices(SPEI) derived from two different potential evapotranspiration estimates, i.e., the Thornthwaite algorithm(SPEI_th) and the Penman-Monteith equation(SPEI_pm), we try to resolve the controversy. The analysis indicated that air temperature has been warming significantly at a rate of 0.4℃ decade^(-1) in the last five decades and the more arid areas are more prone to becoming warmer. Annual precipitation of the entire study area increased insignificantly by 3.6 mm decade^(-1) from 1970 to 2019 but NW presented significantly increasing trends. Further, the SPEI_th and SPEI_pm demonstrated similar wetting-drying-wetting trends(three phases) in China’s drylands during 1970–2019. The common periodical signals in the middle phase were identified both by SPEI_th and SPEI_pm wavelet analysis. Analysis with different temporal intervals can lead to divergent or even opposite results. The attribution analysis revealed that precipitation is the main climatic factor driving the drought trend transition. This study hints that the wetting trend’s direction and magnitude hinge on the targeted temporal periods and regions.