Indicator of climate variability:low treeline displacement in arid valleys of mountain areas,China

As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and changes significantly within 5–10years,provides a new way to study the response to regional climate variability.This study explored the distribution and vertical displacement patterns of the low treeline in the Upper Minjiang River of China,using SPOT remote sensing images in 1999 and 2013and long-term positional observations.Using the Geodetector model,the study investigated the dominant climatic factors influencing the low treeline displacement.The results showed that the low treeline was located at 1700–3200 m elevation on sunny slopes(southeast,south,southwest,and west slopes)with slopes over 25°.From 1999 to 2013,the low treeline moved downward by 6 m from 2561±264m to 2555±265 m,along with a warm–humid climate tendency.The downward displacement was greater on slopes over 25°and shady slopes(-20 m and-10 m,respectively)than on slopes≤25°and sunny slopes.Additionally,the downward was greater in the warm and humid Zagunao River Basin(-15 m)compared to the arid valley center(-7 m)and the cold Heishui River Basin(-3 m).Meanwhile,the low treeline displacement correlated negatively with precipitation and relative humidity variations at the significance level of 0.05,with correlation coefficients of-0.572and-0.551,respectively.Variations in relative humidity and temperature significantly affected the spatial differentiation of low treeline displacement with influencing power of 0.246(p=0.036<0.05)and 0.183(p=0.032<0.05),respectively.Thus,the low treeline is a moisture-limited line,and its formation and variation are closely related to regional water–heat balance.The study clarifies the indicative value of the low treeline for climate variability in mountain areas and can provide references for ecological restoration in arid valleys.

Variations and controlling factors of vegetation dynamics on the Qingzang Plateau of China over the recent 20 years

The impacts of climate change and human activities on vegetation dynamics have attracted wide attention,espe-cially in sensitive and vulnerable areas such as the Qingzang Plateau of China.In this region,a series of ecological restoration projects have been launched while the effectiveness of these projects requires evaluation and further improvements.Remote sensing with high temporal resolution and spatial coverage is an effective way for the vegetation dynamics research in this region.In this study,the spatial and temporal distribution of climate factors and vegetation coverage as well as the influencing factors such as air temperature,precipitation,land use,slope,slope direction,soil and altitude were analyzed.The geographical detector was used to analyze the influence of climate factors on vegetation coverage and the interaction among factors in different eco-geographical regions.The results showed that:1)the average values from the 20 years of normalized difference vegetation index(NDVI)decreased gradually from southeast(>0.61)to northwest(0.12).The overall average of NDVI increased 0.02 per year from 1998 to 2018 and the impact factors varied among different eco-geographical regions;2)some con-trolling factors showed nonlinear enhancement such as altitude and slope;3)land use was an important factor affecting the distribution of vegetation especially in humid,semi-arid and arid areas,but the impacts of elevation and temperature were stronger than land use types in semi-humid and humid areas.The design and construc-tion of ecological protection and restoration projects on the Qingzang Plateau required scientific and detailed demonstration as well as monitoring and evaluation.In addition,new tools and theories were also needed in the selection of ecosystem restoration strategies.Based on the findings,this study also provides suggestions for the sustainable ecological restoration on the Qingzang Plateau.

功能区视角下黄土高原碳公平性的时空分异与影响因素

In this paper, we firstly constructed a theoretical framework based on major function-oriented zones(MFOZs). Then taking the Loess Plateau(LP) as the study area, we revealed the spatio-temporal differences and influencing factors of carbon emission equity by using the carbon equity model, Theil index, and Geo-detector. The results showed that:(1) From 2000 to 2017, the carbon equity of the Loess Plateau showed a downward trend, but the ecological carbon equity remained above 2.3, which was significantly higher than the economic carbon equity.(2) The ecological carbon equity in the Loess Plateau increased from the core of urban agglomeration to the periphery. The spatial pattern of economic carbon equity changed from low in the northeast and high in the southwest to low in the north and high in the south. The ecological support coefficient and economic contribution coefficient of provincial capital cities and their surrounding districts remained low since 2000.(3) The equity of carbon emissions in each function-oriented zone in the Loess Plateau was compatible with its orientation. The ecological carbon equity of the key ecological functional zones(KEFZs) was significantly higher than that of the key development zones(KDZs) and the major agricultural production zones(MAPZs), while the economic carbon equity of the KDZs was significantly higher than that of the MAPZs and the KEFZs.(4) The formation and evolution of the spatial differentiation pattern of carbon equity in the Loess Plateau was the result of the long-term interaction effects of geographic location, social economy, science and technology level, and policy system. Among them, eco-environmental protection policy, government financial support, and geographical location are the key driving factors for the spatial pattern of ecological carbon equity. Geographical location, social economic level, and science and technology level are the key factors driving the spatial pattern of economic carbon equity. According to this study, to achieving carbon equity on the Loess Plateau region, what the key approaches are to fully implement the planning of MFOZs, design differentiated regional carbon compensation mechanisms, improve energy efficiency and ecological environment capacity, and build a collaborative regional carbon emission governance system. This research can not only provide an effective framework for analysing the carbon equity, but also offer policy implication for promoting carbon emission reduction and achieving high-quality development goals in the ecologically fragile areas.