Three-River Source Research Articles

The dominant influencing factors of desertification changes in the source region of Yellow River: Climate change or human activity?

Due to the combined effects of global warming and human activities, the ecological environment of the Yellow River source area has undergone profound changes and desertification has become increasingly prominent. In this study, an optimal desertification monitoring index based on feature space was proposed for the Yellow River source area, and constructed using Landsat images. Then, the spatial and temporal variation of desertification in the Yellow River source area and its driving mechanism were studied using Geodetector. The main conclusions are as follows: (1) The newly proposed feature space-based desertification monitoring index has good applicability in the study area. The best inversion accuracy of the point-to-point Albedo-NDVI feature space model was 88.4%. (2) Desertification in the eastern and southern regions of the Yellow River source area has a tendency to increase, while the desertification situation in the central region is relatively stable. (3) From 1995 to 2015, there was a significant improvement in desertification in the study area, as evidenced by a decrease in desertification intensity. (4) As the intensity of human disturbance increases, the influence of natural factors on desertification gradually diminishes. The interaction of natural and anthropogenic factors has greater explanatory power for desertification than that of individual natural or anthropogenic factors. The research results can be used as a reference for decision-making on desertification control in the Three-River Source Region.

Comprehensive Assessment of Performances of Long Time-Series LAI, FVC and GPP Products over Mountainous Areas: A Case Study in the Three-River Source Region, China

Vegetation biophysical products offer unique opportunities to examine long-term vegetation dynamics and land surface phenology (LSP). It is important to understand the time-series performances of various global biophysical products for global change research. However, few endeavors have been dedicated to assessing the performances of long-term change characteristics or LSP extraction derived from different satellite products, especially in mountainous areas with highly fragmented and rugged surfaces. In this paper, we assessed the time-series characteristics and LSP detections of Global LAnd Surface Satellite (GLASS) leaf area index (LAI), fractional vegetation cover (FVC), and gross primary production (GPP) products across the Three-River Source Region (TRSR). The performances of products’ temporal agreements and their statistical relationship as a function of topographic indices and heterogeneous pixels, respectively, were investigated through intercomparison among three products during the period 2000 to 2018. The results show that the phenological differences between FVC and two other products are beyond 10 days over more than 35% of the pixels in TRSR. The long-term trend of FVC diverges significantly from GPP and LAI for 13.96% of the total pixels, and the percentages of mismatched pixels between FVC and two other products are 33.24% in the correlation comparison. Moreover, good agreements are observed between GPP and LAI, both in terms of LSP and interannual variations. Finally, the LSP and long-term dynamics of the three products exhibit poor performances on heterogeneous surfaces and complex topographic areas, which reflects the potential impacts of environmental factors and algorithmic imperfections on the quality and performances of different products. Our study highlights the spatiotemporal disparities in detections of surface vegetation activity in mountainous areas by using different biophysical products. Future global change studies may require multiple high-quality satellite products with long-term stability as data support.

Impact of Fully Coupled Hydrology-Atmosphere Processes on Atmosphere Conditions: Investigating the Performance of the WRF-Hydro Model in the Three River Source Region on the Tibetan Plateau, China

The newly developed WRF-Hydro model is a fully coupled atmospheric and hydrological processes model suitable for studying the intertwined atmospheric hydrological processes. This study utilizes the WRF-Hydro system on the Three-River source region. The Nash-Sutcliffe efficiency for the runoff simulation is 0.55 compared against the observed daily discharge amount of three stations. The coupled WRF-Hydro simulations are better than WRF in terms of six ground meteorological elements and turbulent heat flux, compared to the data from 14 meteorological stations located in the plateau residential area and two flux stations located around the lake. Although WRF-Hydro overestimates soil moisture, higher anomaly correlation coefficient scores (0.955 versus 0.941) were achieved. The time series of the basin average demonstrates that the hydrological module of WRF-hydro functions during the unfrozen period. The rainfall intensity and frequency simulated by WRF-Hydro are closer to global precipitation mission (GPM) data, attributed to higher convective available potential energy (CAPE) simulated by WRF-Hydro. The results emphasized the necessity of a fully coupled atmospheric-hydrological model when investigating land-atmosphere interactions on a complex topography and hydrology region.

Climate Change and Ecological Projects Jointly Promote Vegetation Restoration in Three-River Source Region of China

Climate Change and Ecological Projects Jointly Promote Vegetation Restoration in Three-River Source Region of China

Precipitation and evapotranspiration partitioning on the Three-River Source Region: A comparison between water balance and energy balance models

Study RegionThree-River Source Region, Qinghai-Tibetan Plateau, China. Study FocusEvapotranspiration (ET) is often the largest loss of water from grassland ecosystems and consists of two constituents: evaporation (E) and transpiration (T), but it is very difficult to separate E and T. In this study, we used an energy balance model (Shuttleworth-Wallace) and a water balance model (SOILWAT2) to estimate the water budget variables over a 10-year period (2007–2016) in a degraded alpine meadow in the Three-River Source Region on the Qinghai-Tibetan Plateau. New Hydrological Insights for the RegionThe models produced contrasting patterns of precipitation and ET partitioning at the study site. Precipitation partitioning by SW2 resulted in substantial fluxes of both ET and deep drainage, while ET estimated by SW consumed almost all precipitation. ET was partitioned by the models into different annual E and T fluxes as well as different monthly and annual T/ET. Our study site located in an important water source region suggests that its water balance would contribute to drainage which aligns better with SW2 results. The surprising discrepancies between the models in the partitioning of precipitation into T, E, and deep drainage, however, is limiting our understanding and management of the degraded site and will require future work to reconcile.

Evapotranspiration and Its Partitioning in Alpine Meadow of Three-River Source Region on the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau (QTP) is generally considered to be the water source region for its surrounding lowlands. However, there have only been a few studies that have focused on quantifying alpine meadow evapotranspiration (ET) and its partitioning, which are important components of water balance. This paper used the Shuttleworth–Wallace (S–W) model to quantify soil evaporation (E) and plant transpiration (T) in a degraded alpine meadow (34°24′ N, 100°24′ E, 3963 m a.s.l) located at the QTP from September 2006 to December 2008. The results showed that the annual ET estimated by the S–W model (ETSW) was 511.5 mm (2007) and 499.8 mm (2008), while E estimated by the model (ESW) was 306.0 mm and 281.7 mm for 2007 and 2008, respectively, which was 49% and 29% higher than plant transpiration (TSW). Model analysis showed that ET, E, and T were mainly dominated by net radiation (Rn), while leaf area index (LAI) and soil water content at a 5 cm depth (SWC5cm) were the most important factors influencing ET partitioning. The study results suggest that meadow degradation may increase water loss through increasing E, and reduce the water conservation capability of the alpine meadow ecosystem.

Construction of a human-wildlife spatial interaction index in the Three-River Source Region, China

In the context of today’s rapid economic development and increasingly strict ecological protection, interactions between humans and wildlife will intensify. Therefore, we need to identify the spatial distribution of such interactions and to take measures to mitigate possible negative interactions. Using the Three-Rivers Source Region as a case study, we combined species habitat suitability, species feeding habits, species conservation levels and human impact intensity to construct a “human-wildlife spatial interaction index” (HWSII) to evaluate the intensity of human-wildlife spatial interactions. The overall level of HWSII was relatively low in the Three-River Source Region. Higher potential human-wildlife interactions occurred in areas with roads and railways. Areas of relatively high interactions between carnivores and livestock were mainly located in the southern part of the study area, and those with relatively high interactions between herbivores and livestock appeared in the western and eastern parts. Managers in these areas should consider mitigation measures. Although developed for a specific region of China, the ‘human-wildlife spatial interaction index’ could have application in other areas of the world for setting a baseline reference to identify areas with the potential for high levels of human-wildlife interactions and pinpoint places where potential negative interactions can be mitigated.

Monitoring Vegetation Greenness in Response to Climate Variation along the Elevation Gradient in the Three-River Source Region of China

The Three-River Source Region (TRSR) is vital to the ecological security of China. However, the impact of global warming on the dynamics of vegetation along the elevation gradient in the TRSR remains unclear. Accordingly, we used multi-source remote sensing vegetation indices (VIs) (GIMMS (Global Inventory Modeling and Mapping Studies) LAI (Leaf Area Index), GIMMS NDVI (Normalized Difference Vegetation Index), GLOBMAP (Global Mapping) LAI, MODIS (Moderate Resolution Imaging Spectroradiometer) EVI (Enhanced Vegetation Index), MODIS NDVI, and MODIS NIRv (near-infrared reflectance of vegetation)) and digital elevation model data to study the changes of VGEG (Vegetation Greenness along the Elevation Gradient) in the TRSR from 2001 to 2016. Results showed that the areas with a positive correlation of vegetation greenness and elevation accounted for 36.34 ± 5.82% of the study areas. The interannual variations of VGEG showed that the significantly changed regions were mainly observed in the elevation gradient of 4–5 km. The VGEG was strongest in the elevation gradient of 4–5 km and weakest in the elevation gradient of >5 km. Correlation analysis showed that the mean annual temperature was positively correlated with VIs, and the effect of the mean annual precipitation on VIs was more obvious at low altitude than in high altitude. This study contributes to our understanding of the VGEG variation in the TRSR under global climate variation and also helps in the prediction of future carbon cycle patterns.

Measuring the Effectiveness of Four Restoration Technologies Applied in a Degraded Alpine Swamp Meadow in the Qinghai-Tibet Plateau, China

To assess the effectiveness of the four restoration techniques (one mono-technology, three combined technologies) on a degraded meadow swamp in Three-river Source Region, we developed a Biology-Environment-Service assessment framework that incorporates 12 indicators from plant, soil to ecosystem services. Two years (2018 and 2019) field monitoring and experimental data revealed that a good restoration effect achieved by the ecological restoration project. The average comprehensive restoration index (CRI)of four restoration sites are, respectively, 0.68, 0.89, 0.71 and 0.84, belonging to a level of GOOD or EXCELLENT. Restoration effect of ensemble restoration technologies is about 4.4%-30% better than that of single fencing. The vegetation restoration was about 2.8 times faster than that of soil and ecosystem services under the same restoration technology during research periods. Restoration effect presented significant difference in respond to various restoration techniques. A combination restoration measue (Fencing + water reservation + reseeding) is recommended as a potential effective restoration method for early stage of alpine wetland restoration.

Hyperspectral inversion of soil heavy metals in Three-River Source Region based on random forest model

Hyperspectral remote sensing technology has considerable research value in monitoring and evaluating soil heavy metal pollution. In this study, the Three-River Source Region was taken as the study area. The occurrence relationship of six heavy metals in soil, such as Mn, Cu, Zn, Pb, Cr, Ni, with soil organic matter, clay minerals, and iron-manganese oxides, was studied through the determination and analysis of soil samples and the collection of soil reflectance spectrum. Spectral transformation was carried out by first derivative, second derivative, inverse-log, continuum removal and multiple scattering correction of the spectrum. The correlation between soil heavy metal content and soil spectrum was analyzed to select the characteristic band, and partial least squares (PLS) method, support vector machine (SVM) method and random forest (RF) model were used to build inversion model based on characteristic band. Then the best combination of spectral transformation and inversion model were explored. The results showed that Pb contents were the twice of the background in Qinghai province. The combination spectrum processing method can improve the correlation between spectrum and heavy metals. The location and quantity of characteristic bands of six heavy metals are different. The accuracy of RF was significantly better than that of SVM and PLS for all six heavy metal (i.e. pb: R2RF = 0.83, R2SVM = 0.62, R2PLS = 0.18), and the model effective of soil properties in non-polluted sites were reliable (i.e. clay: R2RF = 0.93, R2SVM = 0.87, R2PLS = 0.74). This study can provide technical support for the larger-scale monitoring of soil heavy metal content and heavy metal pollution assessment.

Temporal and Spatial Variations in the Leaf Area Index and Its Response to Topography in the Three-River Source Region, China from 2000 to 2017

The Three-River Source Region (TRSR) is an important area for the ecological security of China. Vegetation growth has been affected by the climate change, topography, and human activities in this area. However, few studies have focused on analyzing time series tendencies of vegetation change in various terrain conditions. To address this issue in the TRSR, this study explored vegetation stability, tendency, and sustainability with multiple methods (e.g., coefficient of variation, Theil-Sen median trend analysis, Mann-Kendall test, and Hurst index) based on the 2000–2017 Global LAnd Surface Satellite Leaf Area Index (GLASS LAI) product. The differentiation patterns of LAI variations and multiyear mean LAI value under different topographic factors were also investigated in combination with digital elevation model (DEM). The results showed that (1) the mean LAI value in the study area increased, with a linear tendency of 0.013·10 a−1; (2) LAI values decreased from southeast to northwest in terms of spatial distribution and the CV indicated LAI variations were relatively stable; (3) the trend analysis revealed that the improved area of LAI accounted for 62.72% which was larger than the degraded area (37.28%), and hurst index revealed a weak anti-sustaining effect of the current tendencies; and (4) the increasing trend was found in multiyear mean LAI value as relief amplitude and slope increased, while LAI stability improved with increasing slope. They exhibited a clear regular pattern. Moreover, significant improvement in LAI generally occurred in low-altitude and flat areas. Finally, the overall improvement and sustainability of LAI improved when moving from sunny aspects to shady aspects, but the LAI stability decreased. Note that vegetation degradation was observed in some high slope areas and was further aggravated. This study is beneficial for revealing the spatial and temporal changes of LAI and their changing rules as a function of different topographic factors in the TRSR. Meanwhile, the results of this study provide theoretical support for sustainable development of this area.

青藏高原生态系统完整性远程评价与国家公园群建设时序研究

PDF HTML阅读 XML下载 导出引用 引用提醒 青藏高原生态系统完整性远程评价与国家公园群建设时序研究 DOI: 10.5846/stxb202005241318 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 第二次青藏高原综合科学考察研究（2019QZKK0401）；中国科学院战略性先导科技专项（A类）（XDA20020303） Remote assessment on ecosystem integrity of the Qinghai-Tibet Plateau and research on National Parks Group construction sequence 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:青藏高原是我国重要生态安全屏障，保有大量重要的受人类活动干扰较小的自然生态系统。但近年来受社会经济发展和气候变化的影响，高原生态系统面临退化风险。为了更好地守护地球第三极，第二次青藏科考提出建立青藏高原国家公园群的科学构想。为了全面掌握人类胁迫和气候变化背景下，青藏高原生态系统完整性维持情况，并识别生态系统完整性维持较好的区域，为青藏高原国家公园群的规划布局提供支撑，研究基于对生态系统完整性内涵的理解以及青藏高原生态系统特征，借鉴加拿大国家公园生态系统完整性评估框架，构建了"格局-质量-功能-问题-压力"生态系统完整性远程评估框架，对青藏高原生态系统完整性进行了综合评估并分析了其空间格局特征。结果显示：青藏高原整体维持了较好的生态系统完整性，分别有3.52%、7.51%和70.71%的区域生态系统完整性等级为优、良和中，但受人类胁迫影响，部分区域生态系统完整受到破坏，分别有18.17%和0.10%的区域生态系统完整性等级为较差和极差。从空间上看，青藏高原东部地区生态系统完整性整体高于西部地区。从生态系统完整性保护的角度看，青藏高原可用于建设国家公园的备选区数量多、分布广，且呈现大面积连片分布的格局。目前正在开展的三江源、祁连山、大熊猫、普达措等国家公园体制试点区均具有较高的生态系统完整性。为了加快推动生态系统完整性高的区域保护，根据青藏高原国家公园潜在建设区的生态系统完整性指数结果，建议优先启动雅鲁藏布大峡谷、色林错-普若岗日、独龙江三江并流、若尔盖、贡嘎山、稻城亚丁等国家公园建设，待条件成熟后，再逐步启动其他具有景观、文化价值的国家公园建设。 Abstract:As an important ecological security barrier in China, the Qinghai-Tibet Plateau maintains a large number of important natural ecosystems that are less disturbed by human activities. However, due to the impact of socio-economic development and climate change in recent years, the Qinghai-Tibet Plateau ecosystem is facing the risk of degradation. In order to better protect the Qinghai-Tibet Plateau-the third pole of the earth, the secondly comprehensive scientific investigation of the Qinghai-Tibet Plateau proposed the scientific concept of establishing the Qinghai-Tibet Plateau National Park Group. In order to fully understand the ecosystem integrity status of the Qinghai-Tibet Plateau under the background of human stress and climate change, basing on the understanding of the ecosystem integrity connotation and the ecosystem characteristic of Qinghai-Tibet Plateau, and referring to the ecosystem integrity assessment framework of the Canadian national park, this study builds an indicator system for remote assessment of ecosystem integrity based on the "pattern-quality-function-problem-pressure" framework, and makes a comprehensive assessment of ecosystem integrity of the Qinghai-Tibet Plateau, and then analyzes its characteristics of spatial pattern. The results show that the Qinghai-Tibet Plateau maintains a fair ecosystem integrity. Ecosystem integrity in 3.52% of the region is at excellent level, 7.51% of the region is at good level, 70.71% of the region is at fair level, 18.17% of the region is at poor level, and only 0.10% of the region is at terrible level. From a spatial pattern perspective, the overall ecosystem integrity of the eastern part of the Qinghai-Tibet Plateau is higher than that of the western part. From the perspective of ecosystem integrity protection, there are a large number and wide distribution of areas in the Qinghai-Tibet Plateau suitable for building national parks, and it appears in the pattern of large area and continuous distribution. The current pilot areas of national park system in the Qinghai-Tibet Plateau such as Three-River Source, Qilian Mountain, Giant Panda, and Pudacuo all have high ecosystem integrity. To accelerate the protection of areas with high ecosystem integrity,according to the ecosystem integrity index of the potential construction areas of the Qinghai-Tibet Plateau National Park Cluster, it is recommended to give priority to the construction of the Yarlung Zangbo Grand Canyon National Park, Selincu-Puruogangri National Park, Three Parallel Rivers National Park, Ruoergai National Park, Gongga Mountain National Park and Daocheng Yading National Park; and waiting for the condition is mature, then gradually starting up the construction of the other national parks with landscape and cultural value. 参考文献 相似文献 引证文献

土壤蒸发和植被蒸腾对三江源退化高寒草甸蒸散的影响

蒸散（ET）主要由土壤蒸发（E）和植被蒸腾（T）组成，然而难以把E与T从陆地生态系统ET中区分开。为阐明位于青海省境内的三江源区（89°24'—102°23'E，31°39'—36°16'N）高寒草甸E和T对生态系统ET的影响，利用小型蒸渗仪和微气象系统定量研究了三江源退化高寒草甸ET、E和T的变化，以及植被和环境因子对其的影响。结果表明：2017和2018年的ET分别为467.7 mm和479.2 mm，其中生长季（5—9月）约占72%，且E对生态系统ET的贡献（56%）大于T（44%），年降水量（P）的90%以上通过ET返回大气（ET/P > 90%）。根据生长季中不同植被覆盖度的蒸渗仪观测结果发现，ET随植被覆盖度的降低而增加。逐步回归分析表明，净辐射（R_n）是驱动生态系统ET、E、T最主要的因子；另外，E对饱和水汽压差（VPD）的响应更敏感，而T受空气温度（T_a）的影响更大；土壤含水量（SWC₅）对蒸散的影响相对较小，可能由于研究区降水相对较多的原因。结果说明，草甸退化将加剧土壤蒸发，进而导致生态系统散失更多的水分。;Evapotranspiration (ET) is mainly composed of evaporation (E) and transpiration (T), however it is often difficult to separate E and T from ET in a terrestrial ecosystem. To better understand the effects of E and T on ET of alpine meadow in the Three-River Source Region (TRSR) (89°24'—102°23'E, 31°39'—36°16'N) in Qinghai Province, lysimeter and micrometeorological measurements were used to quantitatively study the variations of ET, E and T, and effects of vegetation and environmental factors on evapotranspiration processes. The results showed that the ET in 2017 and 2018 was 467.7 mm and 479.2 mm, respectively, and ET during the growing season (May-September) accounted for about 72% of annual total ET, while the contribution of E to ET (56%) was greater than that of T (44%). Furthermore, more than 90% of annual precipitation was returned to the atmosphere through the ET processes (ET/P > 90%). Based on the results from lysimeters with different vegetation coverages during the growing season, it was found that ET increased with the decreasing of vegetation coverage. The results of stepwise regression analysis indicated that net radiation (R_n) was the most important factor driving ecosystem ET, E and T; in addition, the response of E to vapor pressure deficit (VPD) was more sensitive than T, while the air temperature (T_a) was more significantly associated with T in comparison to the E. The effect of soil water content (SWC₅) on ET was relatively small maybe due to the precipitation was relatively abundant in this alpine meadow. The results suggested that the degradation of alpine meadow would lead to the increase of E, as a result more water is lost from the ecosystem through evapotranspiration.

Interannual variations of monthly precipitation and associated mechanisms over the Three River Source region in China in winter months

AbstractThis study investigates the interannual variability of winter precipitation over the Three River Source (TRS) region in China based on precipitation observations collected at stations in the TRS region and reanalysis datasets for the period of 1980–2015. The results suggest that the TRS winter precipitation has distinct interannual variability with discordant trends in different months, that is, an increasing trend is found in November and February, a decreasing trend is found in other winter months, and interannual variations in precipitation are different in different months. The mechanisms for the interannual variation in monthly precipitation over the TRS region are significantly different in different winter months. The interannual variability of TRS precipitation in November is modulated by an anomalous westerly water vapour transport (WVT) branch. This anomalous WVT branch is related to a North Atlantic‐Europe‐Tibetan Plateau (NA‐E‐TP) wave‐train that originates in the North Atlantic due to the ocean–atmosphere interaction. In December, a circum‐global teleconnection (CGT) wave‐train can induce anomalous westerly WVT in the TRS region, resulting in increased precipitation there. This CGT wave‐train is triggered by warm SST anomalies in the central‐eastern tropical Pacific associated with the El Niño‐Southern Oscillation (ENSO). The interannual variability of TRS precipitation in January and February is affected by southwesterly WVT anomalies over the TRS region, which are associated with a southeastward propagating wave‐train over Eurasia caused by the North Atlantic Oscillation (NAO). In March, the interannual variability of TRS precipitation is modulated by the leading mode of the Eurasian circulation that resembles the Scandinavian (EU1) pattern, which can cause anomalous southwesterly WVT in the TRS region. In winter, the characteristics of sea surface temperature anomalies, weather systems, and atmospheric circulations associated with interannual variations of monthly precipitation in the TRS region are different for individual winter months.

Remote sensing inversion of grassland aboveground biomass based on high accuracy surface modeling

Accurate and effective accounting of grassland aboveground biomass (AGB) is essential for grassland carbon storage accounting and pastoral agriculture sustainability. In this study, we combined AGB field survey data and remote sensing data to build a suitable model to estimate the grassland AGB in the Three-River Source Region (TRSR) of China. Three machine learning models were used to simulate the grassland AGB from 2001 to 2019, including support vector machine (SVM), random forest (RF), and high accuracy surface modeling (HASM). The results show that (1) the HASM achieved better results than the RF and SVM models (R2 = 0.8459 > 0.72 > 0.5858; RMSE = 29 < 41 < 56), and the HASM results reproduce the spatial distribution characteristics of the biomass well. The subsequent spatiotemporal analysis of the AGB conducted in this study was based on the results of the HASM. (2) The highest AGB was located in the eastern and central-southern parts of the TRSR, and the lowest AGB was distributed in the western region. (3) The overall change in the AGB revealed that the percentage of the area that experienced a significant increase in AGB (21%) was larger than that of the area that experienced a significant decrease (13%), and the stable areas accounted for 66% of the total area. The grassland AGB increased by 1 g/m2/yr during 2001–2019. (4) The factors driving the changes in the AGB were analyzed. Overall, the warm and wet climate conditions promoted grass growth in most regions of the TRSR. (5) However, the biomass decreased in some regions with warm and wet conditions. For example, overgrazing and increased populations of grazing led to significant biomass decreases in the towns of Ziketang and Heka in Xinghai County. In this study, the grassland AGB was simulated based on the HASM model, with a high accuracy and a spatial resolution of 500 m. The results of this study provide a scientific basis for grassland resource protection and the highly effective implementation of grassland restoration projects in China.

Parameter Sensitivities of the Community Land Model at Two Alpine Sites in the Three-River Source Region

The three-river source region plays an important role on China’s ecological security and Asia’s water supply. Historically, the region has experienced severe ecological degradation due to climate change and human activities. Reasonable simulations of the energy and water cycles are essential to predict the responses of land surface processes to future climate change. Current land surface models involve empirical functions that are associated with many parameters. These parameter uncertainties will largely affect the simulation when applied to a new domain. The Community Land Model (CLM) is a widely used land surface model, and version 5.0 is the newest version. Compared to the prior version CLM4.5, CLM5.0 has largely updated plant hydraulic and stomatal conductance schemes. How these changes affect parameter sensitivities is unknown. In our work, we tested 17 key parameters in CLM4.5 and 19 parameters in CLM5.0 at two eddy flux sites in the three-river source region: the Maqu and Maduo sites. We adopted the simplest one-at-a-time changes on each parameter and quantified their sensitivities by the parameter effect (PE). We found that the Maqu site was more sensitive to vegetation parameters, while the Maduo site was more sensitive to the initial soil water content in both CLM4.5 and CLM5.0. This is because Maduo grid cell has wetland that does not respond to vegetation parameters in CLM, which may not reflect the reality. Further model development on wetland vegetation parameterization is important. Our validation on the default simulation showed CLM5.0 did not always improve the simulations. The largest difference between CLM5.0 and CLM4.5 was that soil moisture (SM) showed a much stronger decrease in response to a higher leaf area index (LAI) in CLM5.0 than in CLM4.5, suggesting that SM is more sensitive to vegetation changes in CLM5.0.

Variations of Vegetation Phenology Extracted from Remote Sensing Data over the Tibetan Plateau Hinterland during 2000–2014

How vegetation phenology responds to climate change is a key to the understanding of the mechanisms driving historic and future changes in regional terrestrial ecosystem productivity. Based on the 250-m and 8-day moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data for 2000–2014 in the Three-River Source Region (TRSR) of Qinghai Province, China, i.e., the hinterland of the Tibetan Plateau, we extracted relevant vegetation phenological information (e.g., start, end, and length of growing season) and analyzed the changes in the TRSR vegetation in response to climate change. The results reveal that, under the increasingly warm and humid climate, the start of vegetation growing season (SOS) advanced 1.03 day yr−1 while the end of vegetation growing season (EOS) exhibited no significant changes, which led to extended growing season length. It is found that the SOS was greatly affected by the preceding winter precipitation, with progressively enhanced precipitation facilitating an earlier SOS. Moreover, as the variations of SOS and its trend depended strongly on topography, we estimated the elevation break-points for SOS. The lower the elevations were, the earlier the SOS started. In the areas below 3095-m elevation, the SOS delay changed rapidly with increasing elevation; whereas above that, the SOS changes were relatively minor. The SOS trend had three elevation break-points at 2660, 3880, and 5240 m.

Improved evaluation method of the soil wind erosion intensity based on the cloud–AHP model under the stress of global climate change

Under the stress of global climate change, soil wind erosion has become a major environmental issue in the Three-River Source Region (TRSR) of China. However, few large-scale studies have been conducted on soil wind erosion owing to the lack of investigational data or complex parameters. Moreover, the uncertainty and randomness in the weight determination process cannot be avoided using the traditional method. Thus, a cloud–analytic hierarchy process (cloud–AHP) model was proposed to construct a wind erosion intensity index model for the TRSR based on seven typical land surface parameters. The following results were obtained. (1) The cloud–AHP model can better eliminate the randomness and uncertainty in the weight determination process. (2) The proposed evaluation method of wind erosion intensity has better applicability in the TRSR with overall accuracy of 93%. (3) The overall wind erosion intensity in this region is moderate. The wind erosion intensity was the largest in the Yangtze River (0.55, moderate erosion) and smallest in the source region of the Lancang River (0.50, mild erosion). (4) Significant differences are observed in the influences of various vegetation types on wind erosion intensity. Bare land exhibits the highest wind erosion intensity, whereas a coniferous forest exhibits the smallest. Moreover, grassland is a key control zone of soil and water conservation because it has the largest spatial heterogeneity of internal erosion intensity. These results can provide data and technical support for preventing and controlling soil erosion and protecting the environment in the region.

Overload type and optimization of meadow carrying capacity in Maqin County in the Three-River Source Region, China

Alpine meadows, comprising the main ecosystem of the Three-River Source Region, play an important role in the economic development of western pastoral areas. To determine whether the grazing level was too intense or the nutrient-carrying capacity of the meadows was overloaded, and to offer solutions in Maqin County, Qinghai Province, China, the meadows carrying capacity was determined by combining grass-yield and nutrients data for different seasons across different meadows. The results showed that the levels of crude protein (CP), ether extract (EE), ash, soluble sugars (SS), gas production, and energy value of forage in the summer–autumn grazing meadows were higher than those of the winter–spring meadows. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) of forage in the summer–autumn grazing meadows were lower than those of the winter–spring meadows. We found that no pastures were overloaded with metabolizable energy (ME) for the whole year but digestible crude protein (DCP) was overloaded in winter–spring. And there were differences in the amount carrying capacity (forage yield) of seasonal grazing meadows for the different herds, the overload types were annual overloading (herd A), overloaded in summer–autumn (herd B), overloaded in winter–spring (herd C), and not overloaded (herd D). Compared with the previous grazing mode, theoretical carrying capacity, DCP carrying capacity, and ME carrying capacity of herd A increased by 20, 19, and 27 sheep units, respectively, after optimization; herd B: 36, 31, and 45 sheep units, respectively; herd C: 28, 23, and 44 sheep units, respectively; and herd D: 43, 40, and 61 sheep units, respectively. In the Three-River Source Region and similar alpine pastoral areas, the grassland-livestock structure should be optimized to improve grassland vegetation status and increase the theoretical carrying capacity.

Identification of conflict between wildlife living spaces and human activity spaces and adjustments in/around protected areas under climate change：A case study in the Three-River Source Region

Overlap between wildlife living spaces and human activity spaces represents one of the main causes of human-wildlife conflict. It is therefore necessary to identify and adjust the spatial distribution of conflicts because climate change will modify the ranges and locations of species. The MaxEnt model was used to simulate the distribution of wildlife living spaces under current and future climatic conditions (RCP4.5 scenario) based on species distribution data and environmental data from the Three-River Source Region. Furthermore, the logistic-cellular automata model was used to simulate the changes in human activity spaces (construction land and arable land) by 2050. Areas of overlap between wildlife living spaces and human activity spaces were determined by overlay analysis. Then, the areas of construction and arable land that would conflict with wildlife were redistributed outside highly suitable wildlife living spaces. In addition, ecological corridors connecting current and future living spaces were planned for the migration of certain species in response to climate change based on the minimum cumulative resistance model. The results showed that the areas of highly suitable wildlife living spaces will decrease under the influence of climate change if global warming occurs. In the future, the area of overlap between highly suitable wildlife living spaces and construction land will be 125 km2, and that between highly suitable wildlife living spaces and arable land will be 340 km2. The redistribution of these areas will cause human activity spaces to become more concentrated. Moreover, 110 ecological corridors should be constructed across roads in the Three-River Source Region.