River Headwaters Region Research Articles

Improved soil surface nitrogen balance method for assessing nutrient use efficiency and potential environmental impacts within an alpine meadow dominated region

The soil surface nitrogen balance (SSNB) method is commonly used to assess the nutrient use efficiency (NUE) of agricultural systems and any associated potential environmental impacts. However, the nitrogen flow of wide natural grasslands and other natural areas differ from that of artificial croplands and mown grasslands. In this study, we integrated root growth and the important nutrient resorption process into the SSNB model and used the improved model to clarify the nitrogen (N) flow and balance in the Three Rivers Headwater Region (TRHR)—an area dominated by alpine meadows—from 2012–2019. In the grassland system, the N surplus (ΔN) was 0.274 g m−2 year−1, and root return (BLD) dominated the N input, accounting for 67% of the total input (3.924 g m−2 year−1). N resorption was the main internal N flow in the grassland system (1.079 g m−2 year−1), and 30% of grassland uptake (NUP−grass). The ΔN of the agricultural system was 1.097 g m−2 year−1, which was four times that of the grassland, and chemical fertilizer was the largest input, accounting for 84% of the total input. The NUE in grassland was 93%, which suggests a risk of soil mining and degradation, while that of cropland was 76% and within an ideal range. The ΔN provides a robust measure of river N export, the TRHR was divided into three catchments, and the export coefficient was 16.14%–55.68%. The results of this study show that the improved SSNB model can be applied to a wide range of natural grasslands that have high root biomass and resorption characteristics.

Investigating hydroclimatic impacts of the 168–158 BCE volcanic quartet and their relevance to the Nile River basin and Egyptian history

Abstract. The Ptolemaic era (305–30 BCE) is an important period of Ancient Egyptian history known for its material and scientific advances, but also intermittent political and social unrest in the form of (sometimes widespread) revolts against the Ptolemaic elites. While the role of environmental pressures has long been overlooked in this period of Egyptian history, ice-core-based volcanic histories have identified the period as experiencing multiple notable eruptions, and a repeated temporal association between explosive volcanism and revolt has recently been noted. Here we analyze the global and regional (Nile River basin) hydroclimatic response to a unique historical sequence of four large and closely timed volcanic eruptions (first a tropical one, followed by three extratropical northern hemispheric events) between 168 and 158 BCE, a particularly troubled period in Ptolemaic history for which we now provide a more detailed hydroclimatic context. The NASA (National Aeronautics and Space Administration) GISS (Goddard Institute for Space Studies) ModelE2.1 Earth system model simulates a strong radiative response with a radiative forcing (top of atmosphere) of −7.5 W m−2 (following the first eruption) and −2.5 W m−2 (after each of the three remaining eruptions) at a global scale. Associated with this, we observe a global surface cooling of the order of 1.5 ∘C following the first (tropical) eruption, with the following three extratropical eruptions extending the cooling period for more than 15 years. Consequently, this series of eruptions is observed to constrain the northward migration of the inter-tropical convergence zone (ITCZ) during the Northern Hemisphere summer monsoon season, and major monsoon zones (African, South Asian, and East Asian) were seen to experience a suppression of rainfall of >1 mm d−1 during the monsoon (JJAS) season averaged for 2 years after each eruption. A substantial suppression of the Indian and North African summer monsoon (over the Nile River headwater region) was seen to strongly affect the modeled river flow in the catchment and discharge at river mouth. River mass flow over the basin was observed to decrease by 29 % and 38 % relative to an unperturbed (non-volcanic) annual mean flow in the first and second year, respectively, after the first (i.e., tropical) eruption. A moderate decrease ranging between 5 % and 18 % was observed after the third and fourth (extratropical) eruptions. These results indicate, in sum, that the first eruption likely produced a strong hydroclimate response, with the following extratropical eruptions prolonging this. These results also support the recently hypothesized association between ice-core-based signals of explosive volcanism and hydroclimatic variability during the Ptolemaic era, including the suppression of the agriculturally critical Nile summer flooding.

Long-Term Tibetan Alpine Vegetation Responses to Elevation-Dependent Changes in Temperature and Precipitation in an Altered Regional Climate: A Case Study for the Three Rivers Headwaters Region, China

Recent studies offer more evidence that the rate of warming is amplified with elevation, indicating thereby that high-elevation ecosystems tend to be exposed to more accelerated changes in temperature than ecosystems at lower elevations. The phenomenon of elevation-dependent warming (EDW), as one of the regional climate-change impacts, has been observed across the Tibetan Plateau. Studies have often found large-scale greening trends, but the drivers of vegetation dynamics are still not fully understood in this region, such that the local implications of vegetation change have been infrequently discussed. This study was designed to quantify and characterize the seasonal changes in vegetation across the Three Rivers Headwaters Region (TRHR), where the land cradles the headwaters of the Yangtze, the Yellow, and the Lancang (Mekong). By mapping the normalized difference vegetation index (NDVI) over the growing season from 1982 to 2015, we were able to evaluate seasonal changes in vegetation cover over time. The results show a slightly increased tendency in green vegetation cover, which could possibly be attributed to sustained warming in this region over the past three decades, whereas a decline in the green-up rate with elevation was found, indicating an inconsistent trend of vegetation greening with EDW. The cause of the green-up rate decline at high elevations could be linked to the reduced soil water availability induced by the fast increase in warming rates associated with EDW. The findings of this study have important implications for devising adaptation strategies for alpine ecosystems in a changing climate.

三江源国家公园草地地上生物量时空动态及其气候影响

PDF HTML阅读 XML下载 导出引用 引用提醒 三江源国家公园草地地上生物量时空动态及其气候影响 DOI: 10.5846/stxb202112163570 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技基础资源调查专项资助（2021FY100705）；国家自然科学基金项目（42030509）；国家重点研发计划项目（2019YFE0126503） Spatial-temporal dynamics of the grassland aboveground biomass and its association with climate changes in the Three River Source National Park Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:三江源区位于青藏高原腹地，作为长江、黄河、澜沧江三大河流的发源地，是我国重要的生态安全屏障。基于三江源区域草地AGB的野外调查数据，本研究采用多种机器学习算法集成分析的方式构建模型，实现了高精度的三江源国家公园草地AGB时空估算。基于AGB时空模拟结果，分析了近19年（2000-2018年）三江源国家公园区域草地AGB的时空动态变化。研究结果显示：①通过多种机器学习结合贝叶斯平均模型，草地AGB模拟值与实测值的 r为0.88，RMSE为71.60g/m2，表明多模型集成分析的方式对草地AGB估算获得了较好的模拟效果。②三江源国家公园区域草地AGB的空间分布具有明显的空间异质性，呈从东南向西北递减的趋势。③2000-2018年长江源国家公园、黄河源国家公园和澜沧江国家公园区域草地AGB多年平均值分别为82.96 g/m2、117.54g/m2和168.39 g/m2。④近19年间，在黄河和长江源园区受到温度上升的影响草地AGB呈现出非显著性上升趋势；澜沧江区域，由于2015和2016年的降水量偏低，年际动态统计结果表现为非显著性下降趋势。 Abstract:The Three River Head-water Region (TRHR) is located in the hinterland of the Tibetan Plateau, is the source of the Yangtze River, Yellow River and Lancang River. As an important water source and ecological function conservation area of China, accurate monitoring of the spatio-temporal variation in the grassland aboveground biomass (AGB) is important in the TRHR. In this study, based on field observation, remote sensing, meteorological and topographical data, we estimated the grassland AGB in the Three River Source National Park (TRSNP) and analyzed its spatiotemporal change and response to climatic factors. Four machine learning (ML) models (random forest (RF), cubist, artificial neural network (ANN) and support vector regression (SVR) models) were constructed and compared for AGB simulation. The AGB results estimated with the four ML models were then applied in the integrated analysis via Bayesian model averaging (BMA) to obtain more accurate and stable estimates (r=0.88; RMSE=71.60g/m2). The results showed that the spatial distribution of grassland AGB in the TRSNP had obviously spatial heterogeneity, showing a decreasing trend from southeast to northwest. The grassland AGB in the Yangtze River Source National Park, Yellow River Source National Park and Lancang River National Park were 82.96g/m2, 117.54g/m2, and 168.39g/m2, respectively. In the Yellow River and Yangtze River Source Parks, from 2000 to 2018 grassland AGB showed a non-significant increasing trend due to the influence of temperature increase; in the Lancang River region, the interannual dynamics statistics showed a non-significant downward trend due to the low annual precipitation in 2015 and 2016. 参考文献 相似文献 引证文献

Variation in the hydrological cycle in the Three-River Headwaters Region based on multi-source data

The hydrological processes in the Three-River Headwaters Region (TRHR), which is located in the Qinghai-Tibetan Plateau and includes the Yangtze River Headwater Region (YARHR), the Yellow River Headwater Region (YERHR), and the Lantsang River Headwater Region (LARHR), have changed under climate warming. Based on multi-source data, the spatial and temporal changes in precipitation, evapotranspiration, soil water storage, glacier melt, snowmelt and runoff in the Three-River Headwaters Region from 1982 to 2014 were comprehensively analysed. The annual precipitation data for the Three-River Headwaters Region from ERA5-Land, the Climatic Research Unit, the China Meteorological Forcing Dataset and the Global Land Data Assimilation System (GLDAS) all showed an increasing trend; the annual evapotranspiration data from ERA5-Land, Global Land Data Assimilation System, Global Land Evaporation Amsterdam Model (GLEAM) and Terrestrial Evapotranspiration Dataset across China (TEDC) all showed an increasing trend; and the annual soil water storage data from ERA5-Land, Global Land Data Assimilation System and Global Land Evaporation Amsterdam Model all showed an increasing trend. The annual snowmelt data from ERA5-Land, Global Land Data Assimilation System and SMT-Y datasets all showed a decreasing trend. The annual glacier melt increased in the Yangtze River Headwater Region and Yellow River Headwater Region and decreased in the Lantsang River Headwater Region. The increases in precipitation, evapotranspiration, soil water content and glacial melt, and the decreases in snowfall and snowmelt indicate an accelerated hydrological cycle in the Three-River Headwaters Region over the 1982 to 2014 period. The significant increase in precipitation is the main reason for the significant increase in runoff in the Yangtze River Headwater Region. The increase in precipitation in the Yellow River Headwater Region was less than the sum of the increase in evapotranspiration and soil water storage, resulting in a decreasing trend of runoff in the Yellow River Headwater Region. The increase in precipitation in the Lantsang River Headwater Region was slightly larger than the sum of that in evapotranspiration and soil water storage, and there was an insignificant increase in the runoff in the Lantsang River Headwater Region.

Vegetation Growth Trends of Grasslands and Impact Factors in the Three Rivers Headwater Region

Areas of grassland improvement and degradation were mapped and assessed to identify the driving forces of change in vegetation cover in the Three Rivers headwater region of Qinghai, China. Based on linear regression at the pixel level, we analyzed the vegetation dynamics of the grasslands of this region using MODIS NDVI data sets from 2000 to 2010. Correlation coefficients were computed to quantitatively characterize the long-term interrelationship between vegetation NDVI and precipitation/temperature variability during this period. The use of time series residuals of the NDVI/precipitation linear regression to normalize the effect of precipitation on vegetation productivity and to identify long-term degradation was extended to the local scale. Results showed that significant improvements occurred in 26.4% of the grassland area in the Three Rivers Headwater region between 2000 and 2010. The study area, which represents about 86.4% of the total grassland area of this headwater region, showed a general trend of improvement with no obvious trend of degradation.

Holocene paleohydrology from alpine lake sediment, Emerald Lake, Wasatch Plateau of central Utah, USA

AbstractHolocene sediments at Emerald Lake in central Utah (3090 m asl) document the paleohydroclimatic history of the western Upper Colorado River headwater region. Multi-proxy analyses of sediment composition, mineralogy, and stable isotopes of carbonate (δ18O and δ13C) show changes in effective moisture for the past ca. 10,000 years at millennial to decadal timescales. Emerald Lake originated as a shallow, closed-basin cirque pond during the Early Holocene. By ca. 7000 cal yr BP, higher lake levels and carbonate δ18O values indicate rising effective moisture and higher proportions of summer precipitation continued at least until ca. 5500 cal yr BP when a landslide entered the lake margin. Between ca. 4500 and 2400 cal yr BP dry conditions at Emerald Lake envelop the timing of the ‘Late Holocene Dry Period’ identified at lower elevations. For the past ca. 2500 years, Emerald Lake δ18O values were relatively low, indicating wetter conditions and higher snow input (compared to rain), except for dry periods at ca. 2000 cal yr BP and during the Medieval Climate Anomaly at ca. 1000 and ca. 500 cal yr BP. Results provide a long-term perspective on precipitation extremes that influence regional water supplies from a snow-dominated catchment typical of the predominant source region for the Upper Colorado River.

Temporal dynamics of satellite-derived vegetation pattern and growth in an arid inland river basin, Tibetan Plateau

Exploring alpine vegetation dynamics and its driving factors help to predict changes in hydrothermal circulations at high elevations in the future. Currently, there is a lack of systematic research on this topic in the permafrost regions at a basin scale. Spatiotemporal variations of vegetation pattern and growth estimated from satellite remote sensing images at a 30 m spatial resolution on the Google Earth Engine cloud platform were investigated in the Shule River headwater region from 2000 to 2021. The results showed shrinking trends in alpine grassland (AG) and wetland (AW) area, while an expanding trend in alpine desert (AD) area. AD moved to lower altitudes and occupied AG and AW area, possibly owing to mountain permafrost degradation and extreme precipitation. Vegetation patches became fragmented and complex, reflected by increases in patch number and shape index. Vegetation growth, as approximated by the normalized difference vegetation index (NDVI), increased significantly in 42 % of the vegetated area ( p < 0.05), particularly in river valleys. In addition, NDVI was negatively correlated with solar radiation over 30 % of the vegetated area ( p < 0.05). At the regional scale, vegetation NDVI was positively correlated with root-zone soil moisture and grazing intensity ( p < 0.05). The findings suggested that AG and AW at their upper limit of distribution were vulnerable to soil erosion, and the inter-annual variation of vegetation growth was affected by soil moisture and grazing. Moreover, future climate warming may cause alpine vegetation decline by increasing active layer thickness in the absence of adequate precipitation supply. • Alpine desert mainly invades downward into alpine wetland. • Vegetation patches tend to be fragmented. • NDVI increases significantly in alpine desert. • A negative correlation between NDVI and solar radiation is observed. • Regional vegetation NDVI positively correlates with grazing intensity.

Ecological impacts of N-deposition in a remote, high-elevation lake in the Three River Headwaters Region, Qinghai-Tibetan Plateau

This study provides a new record of nitrogen (N) deposition and ecological response at a remote, high-elevation lake within the ecologically fragile Three River Headwaters Region, northwest China, from the early 20thCentury to the past decade. A multi-proxy investigation of a lake sediment core including analyses of chironomids (non-biting midge), lake sediment geochemistry (δ15N, δ13C, TN, TOC, OC:TN), pollen, non-pollen palynomorphs and 210Pb-dating. Results were compared with regional pollution forcings, including fertiliser application, atmospheric nitrate and dust deposition, and a localised multiscale air quality modelling system for N-deposition. Our data reflect a mesotrophic lake for the majority of the 20th Century with minimal anthropogenic impact. A shift in the lake conditions is evident after 1985 with increased nutrient enrichment. Low δ15N, OC:TN and increasing TN values, together with an increase in chironomid taxa associated with eutrophic conditions and macrophytes are exhibited in the record, particularly since 2002. These changes are consistent with nutrient loading causing a change in trophic status. Redundancy analysis (RDA) and partial RDAs verified TN as an important driver behind the shift in chironomid community composition in recent decades, explaining 22.2% of the variance on its own and 16.9% with other environmental variables partialled out. While temperature change since 1960 was not a primary control on the chironomid community of Lake Bander, a step-change increase in summer temperatures since the 1990s coincided with the disappearance of cold stenotherms from the record and seems to have exacerbated the shift to more productive conditions. This study highlights the reach of airborne N from modern agricultural and industrial activity to remote locations, and demonstrates the utility of palaeolimnological techniques as part of modern ecosystem assessment for conservation.

Trends in total nitrogen concentrations in the Three Rivers Headwater Region

It is important to protect the quality of the water in the Three Rivers Headwater Region (TRHR), known as the water tower of China, to guarantee the water security in downstream areas. However, because of a lack of long-term studies that span wide geographical areas, it is difficult to understand how the water resource in the TRHR should be protected. In this paper, we report the findings from our analysis of total nitrogen (TN) concentration data from 39 river monitoring stations for the period from 2012 to 2018. The water quality status was evaluated by comparing the concentrations with the national standards and calculating exceedance ratios for surface water. Trends were calculated with ordinary linear least-squares regression and a weighted least-squares (WLS) meta-analysis method. The results showed that the annual average TN concentrations in the TRHR rivers from 2012 to 2018 ranged from 0.68 to 1.06 mg/L, and were lower than those in the downstream reaches but higher than the global average in natural river waters. For the period from 2012 to 2018, the TN concentrations showed a highly significant increase (0.03 mg/L/year) across the entire TRHR and were increasing and decreasing at 71.8 % and 28.2 % of the stations, respectively. From the trend results, we divided the study area into two zones, one with increasing TN concentrations and one with decreasing TN concentrations. It is found that environmental factors had little influence on TN concentrations in the increasing and decreasing areas, but artificial factors such as population and restoration project areas contributed to the increases in TN concentrations in the increasing area. The TRHR remains a source of clean water in China; however, the water quality should be monitored closely, and measures should be implemented to protect the resource and mitigate the disturbances caused by human activities.

Livelihood resilience in pastoral communities: Methodological and field insights from Qinghai-Tibetan Plateau

Livelihood resilience is crucial for both people and the environment, especially in remote and harsh ecosystems, such as the Qinghai Tibetan Plateau (QTP). This research aimed to fill the gap of assessing herders' livelihood resilience using more inclusive method. Using survey data from 758 pastoralists, complemented with focus group discussions and transect walks in the Three River Headwater Region (TRHR) on the QTP, we first developed a livelihood resilience evaluation index comprising dimensions of buffer capacity, self-organization and learning capacity. The method of entropy-TOPSIS was then applied to assess the livelihood resilience of local herders, and the spatial patterns were analyzed by spatial autocorrelation method. The results showed the overall level of pastoral livelihood resilience resulted weak, with an east to west spatial gradient toward lower livelihood resilience. Self-organization was the most important dimensions of livelihood resilience, with social cohesion being a dominant factor. Buffer capacity resulted the less important, but the natural capital was significantly higher than the other four livelihood capitals. Furthermore, the northeastern region was a hotspot, while the northwestern region was a cold spot of livelihood resilience. While pastoral populations in the TRHR had high self-organization abilities and potentially high learning capacities, the overall low buffer capacity and livelihood capital limited the improvement of their livelihood resilience. The key findings provide support for enabling policies and integrated strategies to enhance social-ecological resilience. Study may help as paradigm shift reference for the livelihood resilience of pastoral communities in high-altitude areas globally.

Late Woodland settlement ecology of the Appalachian Summit

ABSTRACT The Late Woodland (ca. AD 800–1500) was a time of socioeconomic and environmental change in the Appalachian Summit. Changing climatic conditions and the introduction of maize agriculture made permanent settlement in these high-elevation mountain landscapes possible for the first time. We adopt a settlement ecology approach to examine how Late Woodland communities situated themselves in the landscape. Drawing upon geospatial analyses of legacy datasets, we document how Late Woodland communities prioritized access to different socioeconomic resources in the New River Headwaters region of northwest North Carolina. The New River Headwaters was an important source of natural resources, including mica and copper, as well as an important corridor for the movement of people and resources throughout Eastern North America. Our analyses demonstrate that Late Woodland communities balanced access to arable land, copper sources, and long-distance trade routes when situating their settlements. Larger sites had access to more land suited for maize agriculture than smaller sites. The largest sites in the region were also well-positioned with nearby access to copper sources and trade routes along the New River. Regional approaches to Late Woodland occupation in the Appalachian Summit reveal the dynamic relationship between humans and the environment in mountain landscapes.

Multi-scenario simulations of carrying capacity of the Three River Headwaters Region based on animal husbandry production

Multi-scenario simulations of carrying capacity of the Three River Headwaters Region based on animal husbandry production

Projected shifts in K&amp;ouml;ppen climate zones over China and its national ecological security shelter zones

<p indent="0mm">Based on a set of five regional climate model 21st century climate change simulations, this study assesses future changes in Köppen-Trewartha climate types in China and its five national ecological security shelter zones. The regional climate model, the Abdus Salam International Centre for Theoretical Physics (ICTP) regional climate model RegCM4, is driven by five different global climate models, CSIRO-Mk3-6-0, EC-EARTH, HadGEM2-ES, MPI-ESM-MR and NorESM1-M, at a grid spacing of <sc>25 km</sc> under the representative concentration pathway RCP4.5. These global climate models were selected because of their high horizontal resolution and their good performance in reproducing temperature and precipitation over China. The model configuration used was customized for better performance over China. Bias correction was applied to the simulated temperature and precipitation before calculating the climate types. By the end of the 21st century (2069–2098), the annual mean temperature over China is projected to increase by 2.4°C relatives to the present day (1981–2010) annual mean temperature, with the greatest warming (&gt; <sc>2.8°C)</sc> occurring in the Three Rivers Headwaters region. The annual mean precipitation change shows a general increase in most parts of China, except for a slight decrease (&lt; 7%) in southwestern China. The increase is more pronounced over northwestern China. The distribution of climate types was well reproduced by the simulations. A subtropical humid (Cr) climate mainly covers the regions south of the Yangtze River over eastern China. Southwestern China is dominated by a subtropical winter dry (Cw) climate. The Tibetan Plateau is mostly described as tundra (FT) and arid (type B) climate. Dry arid (BW) and semiarid (BS) climates cover most of the northern regions of 35°N except over northeastern China, where temperate continental (Dc) and subarctic continental (Ec) climates exist. Compared to the present-day climates, a change of 22% in the climate types is projected to occur over the whole Chinese territory by the end of the 21st century. The changes are most significant over the Tibetan Plateau and along the climate transition zone of the Qinling Mountains-Huaihe River over China, with a dominant retreat of FT due to the profound warming and an expansion of BS and Cw being projected for the former, and a replacement of temperature oceanic (Do) by Cw being projected for the latter. Over northeastern China, the main projected change in the climate types is the replacement of Ec by Dc. Tropical wet-dry (Aw) climates will occur over all of Hainan Island. The analysis showed that most changes in climate types are driven by temperature rather than precipitation. For the national shelter zones, climate types will change by 24% over all the areas. Profound changes of ~40% will occur in the shelter zones of the Qinghai-Tibet Plateau and the Sichuan-Yunnan-Loess Plateau, followed by those in the northeastern forest. More specifically, over the Qinghai-Tibet Plateau, the replacement of FT by subarctic oceanic (Eo), BS, Ec, and Dc climates is projected to occur. While FT (62%) and BS (26%) dominate this region currently day, BS (38%) and FT (24%) will account for a greater proportion of the region by the end of the 21st century. The change in climate types on the Sichuan-Yunnan-Loess Plateau is characterized by the expansion of Cw and BS and a loss of FT. Replacement of Ec by Dc is projected in the northeastern forest shelter zone, indicating a major retreat of subarctic coniferous forest there. Greater ecological vulnerability and risks in the future under climate change are expected in the zones. Generally, the changes are in good agreement among the individual simulations, indicating a small uncertainty in the projections.

Evaluation of satellite-based precipitation products from GPM IMERG and GSMaP over the three-river headwaters region, China

AbstractThe three-river headwaters region (TRHR) is the birthplace of the Yangtze River, the Yellow River and the Lantsang River in China. Based on the grid surface precipitation data released by China Meteorological Administration (CMA), this paper evaluated the accuracy and error components of four near-real-time satellite precipitation products (GSMaP-NRT, GSMaP-MVK, IMERG-Early and IMERG-Late) in the era of a GPM (Global Precipitation Measurement) in TRHR. The conclusions are as follows: (1) The precipitation in TRHR is concentrated in the east and south, and the precipitation in the west is very low. IMERG (Early and Late) has a good spatial distribution of precipitation, while GSMaP has an obvious spatial smoothing of precipitation distribution, and does not better highlight the local precipitation characteristics. (2) The inversion accuracy of the satellite products is the best in the source region of the Lantsang River, followed by the source region of the Yellow River. The satellite products all show the lower correlation coefficient and serious underestimation of precipitation in the west of the TRHR. In addition, the closer to the west of the TRHR, the lower hit rate and the higher false alarm rate of the satellite products, especially the NRT and MVK products. In the eastern margin of the Yellow River headwater region and the Lantsang River headwater Region, RMSE and overestimated precipitation were higher in NRT and MVK, and FAR was higher in spite of higher POD and CSI. (3) The errors of GSMaP in the source region of the Yellow River and the Lantsang River are mainly caused by misreporting precipitation and overestimating the precipitation level, while the errors of GSMaP in the west of the TRHR are mainly caused by missing measurements of precipitation events. The underestimated precipitation of IMERG mainly comes from the missed measurement of precipitation and the underestimate of precipitation level, and there is no large false precipitation. (4) In addition, we found that the satellite products in the lake distribution area of the TRHR have serious missed precipitation errors, indicating that the GPM satellite products have the poor detection ability of precipitation near plateau lakes. On the whole, the precipitation inversion accuracy of IMERG (Early and Late) products is higher, which can better detect the occurrence of precipitation events, but the estimation of precipitation level is still not accurate. The precision of precipitation of satellite products near inland lakes on the plateau is poor, so the algorithm improvement of new products needs to be further solved in the future.

Monitoring grassland degradation and restoration using a novel climate use efficiency (NCUE) index in the Tibetan Plateau, China

Grassland degradation is one of the most pressing challenges in natural environment and anthropogenic society. However, there is yet no effective approach for monitoring the spatio-temporal pattern of large-scale grassland degradation. In particular, the research on grassland changes in the harsh natural environment such as the Qinghai-Tibet Plateau is still in its infancy due to complexity, and it is extremely difficult for humans to reach these remote areas. The annual changes in the grassland biomass might be the results of climate fluctuations or grassland degradation. To test the hypothesis, the impact of inter-annual climate fluctuations needs to be considered when monitoring the grassland degradation based on spatio-temporal change of grassland biomass. In this paper, we propose a Novel Climate Use Efficiency index (NCUE) by considering rainfall, temperature, sunlight time, wind speed, surface temperature, accumulated temperature, time lag effect, light, temperature and water suitability and their coordination climatic factors that mainly affect vegetation growth comprehensively, to monitor grassland change suitable for cold and dry climate characteristics of the Qinghai-Tibet Plateau, and to reduce the effect of inter-annual variability of grassland productivity caused by climate fluctuation. As a consequence, grassland degradation monitoring could be more accurate and objective than existing ecological indicators. Our experiments show that the slope of NCUE over 31 years from 1982 to 2012 is 0.0028, showing a recovery trend in grassland. Degradation and restoration of grassland exist at the same time, and their proportions are 20.49% and 23.89%, respectively. By comparing with in-situ measurements in 2013 and 2009, 68% consistency was achieved with our prediction, and the 70% consistency is achieved by comparing with the positive and negative change trend of accumulated NDVI during the growing season. Moreover, the comparative analysis of land use/cover changes (LUCC) from 1990 to 2010 shows 69% of consistency. The ratio of the area of grassland significantly degradation and recovered predicted by NCUE change trend is 1.41% and 1.43%, respectively. It occupies a very small area of the study area. Yet, that predicted by NDVI change trend is 42.17% and 31.90%, respectively, and about 70% of the area is detected as drastic changes. It shows that NDVI is sensitive to climate fluctuations, while NCUE reduces the impact of climate fluctuations, reflecting change of grassland being affected by human activities and long-term climate change. The novel NCUE has great potential and utility to minify the impact of climate fluctuation and reflect grassland changes over space and time quantitatively. Such ecological index provides a new understanding of spatial and temporal patterns of grassland degradation in the Three River Headwaters Region (TRHR) at the same time.

Spatiotemporal variations of land surface albedo and associated influencing factors on the Tibetan Plateau

Land surface albedo plays a crucial role in the land surface energy budget and climate. This paper identified the spatiotemporal variations of surface albedo on the Tibetan Plateau (TP) from 1982 to 2015, and quantified the relationships between the spatial and temporal patterns of the albedo and associated influencing factors (snow cover, vegetation, and soil moisture) on the seasonal and interannual basis using satellite products and reanalysis data. It was determined that the albedo presented a distinct spatial variability, with high values in mountainous areas and low values on the southeastern TP. Spatially, average albedo exhibited a positive correlation with snow cover and negative correlations with vegetation and soil moisture. Average albedo over the whole TP had a clear seasonal cycle with a peak in winter and a minimum value in summer, which is dictated by seasonal changes in snow and vegetation covers. Annual average albedo exhibited a weakly downward trend, which was mainly contributed by a significant decrease in summer, pointing to the important role in vegetation dynamics for temporal change of the albedo. On the regional basis, interannual variation of albedo was more responsive to snow cover over the snow- and vegetation-coexisting area than the snow-covered area, and to changes in Normalized Difference Vegetation Index (NDVI) over the vegetation-covered area than the snow- and vegetation-coexisting area; albedo had a weakly negative correlation with soil moisture over bare soil. Furthermore, our results indicated that snow cover was the dominant factor for albedo change on mountainous areas, and vegetation change predominated the variation of albedo on the eastern, southern, and northwestern TP. Specifically, variations in snow cover contributed more than those of vegetation to the interannual albedo variation over the Three Rivers Headwater Region. These results would be beneficial for better understanding the climate and eco-environment changes over the TP.

Distribution Characteristics of Soil Moisture in the Three Rivers Headwaters Region, China

The change of soil moisture has significant influence on the surface energy distribution and evapotranspiration process and causes the climatic environment changes. It is thus urgent to detect soil moisture facing climate change problems. Based on apparent thermal inertia method, the GLDAS soil moisture of the layer in 0 ~ 10 cm, 10 ~ 40 cm, 40 ~ 100 cm, 100 ~ 200 cm under the ground surface are proceeded for downscaling and the monthly soil moisture are obtained by combination of MODIS data. Statistics of precipitation and temperature of 13 meteorological stations in the Three River Headwater Region (TRHR) are collected to analyze the correlation between soil moisture change and temperature and precipitation. The correlation between soil moisture and evapotranspiration (ET) are analyzed by using the surface energy balance system model to calculate the average evapotranspiration in the study area. The result indicated that (1) Apparent thermal inertia (ATI) is positively correlated with soil depths in the four layers below the surface and has the best correlation with 0 ~ 10 cm soil moisture. Soil moisture increases with soil depth. Soil moisture is lowest under 0 ~ 10 cm depth while highest under 10 ~ 40 cm on average. (2) In terms of spatial distribution of TRHR, soil moisture is higher in the northwest and southeast, but lower in the southwest and northeast than average. The temporal variation of the soil moisture in one year was high in summer and low in winter, and the average annual soil moisture increased with time. (3) Soil moisture is negatively correlated with temperature and positively corre-lated with precipitation. There is a positive correlation between soil moisture and evapotranspiration. The linear regression coefficient of determination R2 is 0.8489.

Multiple perspectives on eco-compensation of ecological migrants in the Three Rivers Headwaters Region, China

The purpose of the study is to determine the reasonable compensation standards for ecological immigrants in the Three Rivers Headwaters region, four calculation methods were proposed according to different conditions. Results show that the minimum compensation standard for herdsmen was recommended from the current 10,000 yuan/year to 25,000 yuan/year. The highest compensation standard is proposed to, with the consideration of the quality and area of grassland, be increased by 2.5-5.0 times compared to the current compensation standard. It is expected that the current study may provide a novel perspective and reference for the compensation standards for ecological immigrants for nature reserves.

Spatiotemporal Variation and Climate Influence Factors of Vegetation Ecological Quality in the Sanjiangyuan National Park

The Sanjiangyuan National Park is the first Chinese national park system, and the ecological environment is inherently fragile and sensitive. Therefore, for environmental protection, it is imperative to understand the spatiotemporal variation characteristics of the ecological quality of vegetation and its climate influence factors. We used the MODIS normalized difference vegetation index (NDVI) dataset, meteorological dataset, and Carnegie–Ames–Stanford Approach (CASA) model to investigate the spatiotemporal patterns and change trends of the NDVI and the net primary productivity (NPP) of the vegetation in the Sanjiangyuan National Park from 2000 to 2016. A linear regression model was used to explore the influence of the ecological quality of vegetation and climatic factors. The results showed that (1) the NDVI and NPP were high in the southeast area and low in the northwest area. The Yangtze River headwater region had the lowest NDVI (0–0.3) and NPP (0–100 gC/m2). The Lancang River had the highest NDVI (0.4–0.8) and NPP (100–250 gC/m2). (2) From 2000–2016, approximately 23.46% of the area showed a significant positive trend of the NDVI that was mainly distributed in the prairie areas in the midlands and the north of the Yangtze River headwater region, and was scattered in the midlands and the north of Yellow River headwater region. Furthermore, 24.32% of the NPP was determined to have increased significantly, which was mainly distributed in the midlands and the north of the Yangtze River headwater region, as well as the midlands and the east of the Yellow River headwater region. (3) The vegetation growth in the Sanjiangyuan National Park was regulated by both water and heat conditions. The NDVI was significantly affected by precipitation during the growing season and by the annual precipitation. In addition, the NPP was significantly affected by temperature during the growing season and by the annual average temperature of the study area.