Browsing by Subject "Ecological restoration"

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    Age-related water use characteristics of Robinia pseudoacacia on the Loess Plateau
    (Elsevier, 2021-05) Wang, Jian; Fu, Bojie; Jiao, Lei; Lu, Nan; Li, Jianye; Chen, Weiliang; Wang, Lixin; Earth Sciences, School of Science
    Understanding water use characteristics of revegetation species is crucial for evaluating plant adaptability and guiding the sustainability of vegetation restoration in semiarid regions. Ecological restoration projects have been implemented for decades in degraded ecosystems, achieving significant changes in vegetation cover. However, water use characteristics of the main tree species at different ages remain poorly understood in such systems. We investigated water use characteristics of Robinia pseudoacacia in plantations of different stand-age (18 and 30 years). The species is the most widely planted tree in revegetation efforts on the Loess Plateau. The δ2H and δ18O of xylem and soil water within 500 cm of the soil surface and the δ13C values of plant leaves were measured during two consecutive hydrological years. The results showed that that water uptake proportions from across the soil columns changed in 18-yr R. pseudoacacia between a drier (2016) and wetter year (2017). In contrast, shallow soil water was largely comparable in a stand of 30-yr R. pseudoacacia in 2016 and 2017, and similarly the pattern of water uptake by roots from the middle and deep soil column was comparable. However, leaf-level water use efficiency (WUEi) of trees in the older plantation was higher during the wetter year, thereby partly alleviating a low infiltration to precipitation ratio. These findings suggest that different stand-age plantation trees have distinct water use characteristics and display different responses to variations in precipitation. Older plantation trees respond to increased water availability by increasing WUEi instead of switching water sources. This means that stand-age is an essential factor to be considered in ecological restoration management, which can enhance the effectiveness of vegetation restoration strategies. The study indicates useful input from research to management throughout the continuity of restoration effort.
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    Variations and controlling factors of vegetation dynamics on the Qingzang Plateau of China over the recent 20 years
    (Elsevier, 2021) Zhang, Xiao; Wang, Jun; Gao, Yan; Wang, Lixin; Earth Sciences, School of Science
    The impacts of climate change and human activities on vegetation dynamics have attracted wide attention, especially 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 controlling 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 construction 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.