| Today, climate change is of widespread concern in the international community as a major global issue, and seriously threatens natural ecosystems and socioeconomic systems. The impact on environmentally fragile areas is especially significant. In the Inner Mongolia medium temperate desert steppe, vegetation is low and sparse, community productivity low, the climate arid, and the natural environment complex. This makes the area extremely sensitive to climate change. Therefore under global climate change, the study of the response to climate change of the Inner Mongolia desert steppe ecosystem has important theoretical and practical significance.Given this steppe as the study area, we used data from11meteorological stations from1961to2010to investigate spatiotemporal distribution patterns and trends of temperature, precipitation and aridity index. We also used turning-green and withering period data from6ecological stations over2004-2012on the steppe, to analyze variations of plant phenology and the impact of climatic factors on that phenology. Using146-quadrat field data from2008and2009, we studied climate factor influences on the distribution of species diversity. NOAA/AVHRR NDVI data from1982to2009and a climate data-driven Eddy Covariance-Light Use Efficiency (EC-LUE) model were used to simulate Gross Primary Production (GPP) on the desert steppe, to analyze spatiotemporal variations and investigate the influence of climatic factors on GPP. Using Thornthwaite Memorial model simulations of climate productivity on the desert steppe, we examined future climate-change scenario productivity trends.Temperature on the Inner Mongolia desert steppe showed asymmetric variations. Annual average temperature and annual mean maximum and minimum temperatures all showed warming trends, of0.47,0.33and0.60℃/10a, respectively. The minimum temperature increased most significantly. Temperature in the four seasons had warming trends, with the greatest warming in winter.Annual precipitation showed a banded pattern, gradually declining from southeast to northwest on the steppe. In the last50years, precipitation fluctuated but with a slight downward trend, especially in the last decade. Spatially, annual precipitation significantly increased in an adjoining area of typical steppe and the west-central region, and significantly decreased in the northeast. Temporally, precipitation increased in spring and decreased in summer.The annual average aridity index showed a banded progressive increase from southeast to northwest. There was a tendency toward increased aridity on the desert steppe, with a higher aridity index and a clear increasing trend. The drought trend in the study area was most severe in the last decade. Warming was main factor causing the aridity index increase.Turning-green and withering periods of the steppe grassland vegetation were early, and the number of growing-season days were shortened. There was significant negative correlation between the turning-green period and average temperature in February, and April rainfall was important for turning green. Temperature rise and rainfall increase in spring resulted in an early turning green of vegetation.Species richness increased with longitude, consistent with the spatial distribution of precipitation. There was negative correlation between species richness and potential evapotranspiration. Precipitation had a strong influence on species richness distributions for biennial herbaceous, perennial forb, and perennial rhizomatous grass functional groups. With precipitation increase, biennial herbaceous species richness decreased, but that of perennial forbs and rhizomatous grasses increased.The GPP distribution was high in the south and low in the north, plus high in the east and low in the west. The distribution of aridity index had greater consistency than GPP. From a regional point of view, the GPP of the southeast decreased and increased in the northwest. From the time point of view, Since1982, GPP on the steppe has had a declining trend, especially in the last decade, consistent with the characteristics of climate change. GPP decreased in the southeast part of the region, and increased in the northwest. Annual, growing-season and summer precipitation all had significant positive correlations with GPP, indicating that precipitation was a key constraint on GPP.Climate change significantly affected climate potential production."Warm-wet" and "cold-wet" climates increased climate potential production, but this production was reduced by a "warm-dry" climate. This indicates that vegetation growth was less affected by temperature than by precipitation. Precipitation was a key limitation of vegetation growth.According to correlation analyses and forecasts, climate of the Inner Mongolia desert steppe will be warmer and drier in the future. Therefore, GPP will decrease.With climate change, plant phenology became earlier, the growing season shortened, and vegetation productivity declined. This significantly impacted the local economy and the production and living conditions of farmers and herdsmen. This should be urgently addressed by the government, which should formulate policies and measures to combat climate change as quickly as possible. |
