Soil moisture (SM), an important variable in water conversion between the atmosphere and terrestrial ecosystems, plays a crucial role in ecological processes and the evolution of terrestrial ecosystems. Analyzing and exploring SM’s processes and influencing factors in different permafrost regions of the Qinghai-Tibet Plateau (QTP) can better serve the regional ecological security, disaster warning, water management, etc. However, the changes and future trends of SM on the QTP in recent decades are uncertain, and the main factors affecting SM are not fully understood. The study used SM observations, the Global Land Evapotranspiration Amsterdam Model (GLEAM) SM products, meteorological and vegetation data, Mann–Kendall test, Theil–Sen estimation, Ensemble Empirical Mode Decomposition (EEMD), and correlation methods to analyze and explore the characteristics and influencing factors of SM change in different permafrost regions of the QTP. The results show that: (1) At the pixel scale, GLEAM SM products can better reflect SM changes in the QTP in the warm season. The seasonal permafrost region is closer to the real SM than the permanent region, with a median correlation coefficient (R) of 0.738, median bias of 0.043 m3 m−3, and median unbiased root mean square errors (ubRMSE) of 0.031 m3 m−3. (2) The average SM in the QTP warm season increased at a rate of 0.573 × 10−3 m3 m−3 yr−1 over the recent 40 years, and the trend accelerated from 2005–2020. In 64.31% of the region, the soil was significantly wetted, mainly distributed in the permafrost region, which showed that the wetting rate in the dry region was faster than in the wet region. However, the wetting trend does not have a long-term continuity and has a pattern of “wetting–drying-wetting” on interannual and decadal levels, especially in the seasonal permafrost region. (3) More than 65% of the SM wetting trend on the QTP is caused by temperature, precipitation, and vegetation. However, there is apparent spatial heterogeneity in the different permafrost regions and vegetation cover conditions, and the three factors have a more substantial explanatory power for SM changes in the seasonal permafrost region. With the global climate change, the synergistic SM–Climate–Vegetation effect on the QTP tends to be more evident in the seasonal permafrost region.

植被对水热条件的响应因生态系统的空间异质性而具有显著的差异.基于GIMMS NDVI3g和MODIS NDVI逐旬数据集,通过数据融合构建的青藏高原1982-2020年的植被时间序列,利用Mann-Kendall趋势法分析近40年植被动态变化及其对温度、降水和辐射等水热条件的响应,并划定了植被动态的主要水热驱动因子分区.结果表明:(1)近40年青藏高原植被生长季平均NDVI呈现显著上升趋势,增速为0.006/10a,植被NDVI显著增加和减少的区域分别占青藏高原总面积的73.97％和18.38％;(2)青藏高原植被对水热条件的响应在静态上表现为高原腹地较高原边缘更加明显;在动态上表现为不同植被类型区对水热因子的响应关系、方向、程度均有所不同;整体上除森林和灌丛外,所有高寒植被类型与降水的响应程度要优于温度和辐射;(3)青藏高原植被生长受水热因子驱动的区域占高原总面积的55.95％,其中42.72％以上的区域气温、降水和太阳辐射的驱动作用是互补的,13.23％的区域由多个水热因子联合驱动;44.05％的区域为非气候驱动区.

基于问卷调查数据,以青海省都兰县为例分析西部山区县域贫困人口的收入特征及影响因素.结果表明:(1)西部山区贫困人口的收入差距明显,呈偏态分布,贫困人口的收入虽然已达到脱贫的标准,但是多数贫困人口的收入处在平均值以下.(2)西部山区贫困人口的收入结构性差异明显,转移性收入和工资性收入过高,而经营性与财产性收入过低.降低转移性收入的占比,减少不稳定的政策性"输血式"的扶贫资金,增加"造血式"扶贫方式的投入,从根本上使贫困人口获得稳定的收入,是贫困人口完全脱离贫困的途径之一.(3)是否具有劳动能力是影响西部山区贫困人口收入的主要因素,诸多贫困人口因不良的身体状况以及因丧失劳动力而致贫.对于因病因残丧失劳动能力的贫困人口,开展健康帮扶,加大民政救助兜底保障的力度,优先安排慈善救助,以帮助其尽快脱离贫困.

ABSTRACT Pan evaporation ( E pan ) is reported to have exhibited a decreasing trend in many regions of the world over the past several decades. However, recently, the latest studies have discovered the inconsistent phenomenon that the E pan of some regions showed an increasing trend with climate change. E pan is regarded as a critical indicator that plays a significant role in atmospheric evaporative demand, and its trend has an important significant indication to climate change and ecological environment changes. In this article, we adopted the PenPan model and the method of the total short‐wave irradiance of the pan to reparameterize the PenPan‐20 model for the Qinghai–Tibet Plateau (QTP). In addition, we employed sensitivity and a contribution model to analyse the attribution of changes in E pan under climate change over the QTP in 1970–2011. The results showed that the PenPan model can be applied to QTP. Furthermore, the results showed significant decreasing trends of E pan in 1970–2001 and insignificant increasing trends of E pan in 2002–2011. Therefore, we compartmentalized the two periods to analyse the cause of changing E pan by sensitivity and contribution rate. Trend analysis determined that the combined effects of decreasing net radiation and wind speed contributed to the decreasing of E pan in 1970–2001, and the increasing vapour pressure deficit contributed to the increasing of E pan in the study area in 2002–2011. Meanwhile, sensitivity analysis revealed that net radiation was the most sensitive factor. In addition, the results of analysis of the contribution rate were consistent with trend analysis. The dominant factor of changing E pan varied in different periods via qualitative and quantitative analysis.

基于AVHRR/NDVI和MODIS/NDVI遥感数据,通过拟合两种数据源延长NDVI时间序列来反演了三江并流河源区1982-2012年植被覆盖度空间格局的变化规律,并结合气温和降水量数据,从不同时空尺度上分析了植被覆盖变化趋势及其对气候变化的响应.结果表明:1.研究区植被覆盖度整体上随着热量梯度呈南高北低、东高西低的态势分布,且海拔在4000m以下的区域植被覆盖度较高,平均值在0.68～ 0.75;2.研究期间,植被覆盖度以0.02/(10 a)的变化率呈增加趋势,海拔在4600m左右和低覆盖度的区域植被增加趋势显著,显著增加区域面积占研究区总面积的36.4％,主要分布于沱沱河流域、怒江流域(除源头外)和研究区东南部等地区,这些区域植被覆盖度平均值仅为0.36;3.相对于降水量,研究区的植被覆盖度与气温要素相关性更为显著,特别是高原面上的植被覆盖度整体上与气温呈显著正相关关系,显示了强烈的热量限制性生态类型的特点.

Reference evapotranspiration (ET0), as an estimate of the evaporative demand of the atmosphere, has been receiving extensive attention in researches on hydrological cycle. Sensitivity of ET0 to major climatic variables has significant applications in climatology, hydrology, and agrometeorology and is also important to improve our understanding of the connections between climatic conditions and ET0 variability. In this study, we used the Penman-Monteith equation to calculate ET0 and adopted a nondimensional sensitivity coefficient formula to analyze sensitivities of ET0 to four climatic variables based on daily meteorological data from eight meteorological sites in the Huangshui River basin and surrounding areas during 1961–2010. The results indicated that (1) strong correlations with R 2 up to 0.76 exist between observed E pan and calculated annual ET0; (2) ET0 had a decreasing trend in the Huangshui River basin (HRB) during 1961–2010; (3) Spatially, distribution of ET0 was largely correlated with altitude, for instance, the average annual ET0 was larger in low-altitude areas than in high-altitude areas; (4) ET0 was more sensitive to actual vapor pressure in high-altitude areas while it was more sensitive to temperature in low-altitude areas; and (5) ET0 showed a decreasing trend and was consistent with the decreases in net radiation and wind speed at seasonal and annual time scales in HRB during 1961–2010. Sensitivity analysis of ET0 to major climatic variables revealed that temperature was primarily responsible for changes in ET0 in the growing season while actual vapor pressure was the dominating factor causing changes in ET0 in the nongrowing season. However, annual averaged ET0 was more sensitive to actual vapor pressure (R 2 = 0.63), indicating that actual vapor pressure was possibly the primary climatic variable that causes changes in annual ET0.

Crop reference evapotranspiration(ET0) is often used to determine crop water requirement.In this study,the ET0 values were calculated using the Penman-Monteith model based on the 41-year measured meteorological data of daily net radiation,actual vapor pressure,mean air temperature,mean wind speed,and precipitation at 11 meteorological stations in the Qaidam basin during the period of 1970-2010.The sensitivity of ET0 to the variation of climate variables was estimated and the effects of climate variables on ET0 were analyzed.The results showed that:(1) Over the past 41 years,the climate in the Qaidam basin has a trend toward warm-humid conditions,and the ET0 has a decreasing rate of-17.8 mm/10a.From the perspective of qualitative trend analysis,the decreasing of ET0 is likely to be associated with the decreasing of wind speed and net radiation.(2) In terms of the sensitivity of ET0 to climate variables,the sensitivity of ET0 to actual vapor pressure decreases every year,but the sensitivities of ET0 to net radiation,air temperature,and wind speed increase every year.ET0 is most sensitive to net radiation while least sensitive to temperature.Also,the sensitivity of ET0 to temperature is the most unstable.(3) Over the past 41 years,the relative changes in wind speed reached 49.9%,which contribute the most to ET0 in the Qaidam Basin.Although the relative changes in temperature were up to 64.4%,but their contribution to ET0 was less than that of wind speed.Meanwhile,the contributions of net radiation and vapor pressure to ET0 were not obvious.The spatial contribution of temperature to ET0 was positive,while the spatial contributions of wind speed,net radiation,and actual vapor pressure to ET0 were negative.Wind speed was the dominant factor affecting the variations of ET0 in the Qaidam Basin.