分类： 生物学 >> 生态学 提交时间： 2019-06-20 合作期刊: 《干旱区科学》
摘要： Environmental heterogeneity significantly affects the structure of ecological communities. Exploring vegetation distribution and its relationship with environmental factors is essential to understanding the abiotic mechanism(s) driving vegetation succession, especially in the ecologically fragile areas. In this study, based on the quantitative analysis of plant community and environmental factors in 68 plots at 10 different transects in the Minqin oasis-desert ecotone (ODE) of northwestern China, we investigated desert vegetation distribution and species-environment relationships using multivariate analysis. Two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA) methods were used. A total of 28 species, belonging to 27 genera in 8 families, were identified. Chenopodiaceae, Zygophyllaceae, Gramineae, and Leguminosae were the largest families. Annual and perennial herbs accounted for 28.60% of the total number of plants, while shrubs (42.90%) were the most dominant. Nitraria tangutorum was the constructive species of the desert plant community. We divided the 68 plots surveyed in this study into 7 community types, according to the results of TWINSPAN. The distribution of these 7 communities in the DCA ordination graph showed that species with a similar ecotype were clustered together. Results of CCA indicated that groundwater was the dominant factor influencing vegetation distribution, while distance between plot and oasis (Dis) and soil electrical conductivity (EC) were the local second-order factors. Our study suggests that optimizing the utilization of groundwater in oases is key to controlling the degradation of desert vegetation. The favorable topographic conditions of sand dunes should be fully utilized for vegetal dune stabilization, and the influence of soil salinity on the selection of afforestation tree species should be considered.
分类： 地球科学 >> 地理学 提交时间： 2023-07-17 合作期刊: 《干旱区科学》
摘要：Haloxylon ammodendron, with its tolerance of drought, high temperature, and salt alkali conditions, is one of the main sand-fixing plant species in the oasis-desert transition zone in China. This study used the TDP30 (where TDP is the thermal dissipation probe) to measure hourly and daily variations in the stem sap flow velocity of H. ammodendron at three age-classes (10, 15, and 20 years old, which were denoted as H10, H15, and H20, respectively) in the Minqin oasis-desert transition zone, China, from May through October 2020. By simultaneously monitoring temperature, relative humidity, photosynthetically active radiation, wind speed, net radiation, rainfall, and soil moisture in this region, we comprehensively investigated the stem sap flow velocity of different-aged H. ammodendron plants (H10, H15, and H20) and revealed its response to physical factors. The results showed that, on sunny days, the hourly variation curves of the stem sap flow velocity of H. ammodendron plants at the three age-classes were mainly unimodal. In addition, the stem sap flow velocity of H. ammodendron plants decreased significantly from September to October, which also delayed its peak time of hourly variation. On rainy days, the stem sap flow velocity of H. ammodendron plants was multimodal and significantly lower than that on sunny days. Average daily water consumption of H. ammodendron plants at H10, H15, and H20 was 1.98, 2.82, and 1.91 kg/d, respectively. Temperature was the key factor affecting the stem sap flow velocity of H. ammodendron at all age-classes. Net radiation was the critical factor influencing the stem sap flow velocity of H. ammodendron at H10 and H15; however, for that at H20, it was vapor pressure deficit. The stem sap flow velocity of H. ammodendron was highly significantly correlated with soil moisture at the soil depths of 50 and 100 cm, and the correlation was strengthened with increasing stand age. Altogether, our results revealed the dynamic changes of the stem sap flow velocity in different-aged H. ammodendron forest stands and its response mechanism to local physical factors, which provided a theoretical basis for the construction of new protective forests as well as the restoration and protection of existing ones in this region and other similar arid regions in the world.
分类： 农、林、牧、渔 >> 土壤学 提交时间： 2024-05-15 合作期刊: 《干旱区科学》
摘要： The clay–sand barriers in Minqin desert area, China, represent a pioneering windbreak and sand fixation project with a venerable history of 60 a. However, studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion, particularly from the perspective of surface sediment grain size, are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities. This study focused on the surface sediments (topsoil of 0–3 cm depth) of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size. In March 2023, six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations (1, 5, 10, 20, 40, and 60 a) were selected as experimental plots, and one control sampling plot was set in an adjacent mobile sandy area without sand barriers. Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed. Results indicated a predominance of fine and medium sands in the surface sediments of the study area. The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments, increasing the average contents of very fine sand, silt, and clay by 30.82%, 417.38%, and 381.52%, respectively. This trend became markedly pronounced a decade after the deployment of clay–sand barriers. The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity, the interception of sand flow, and the promotion of fine surface sediment particles. Coarser particles such as medium, coarse, and very coarse sands predominantly accumulated on the external side of the barriers, while finer particles such as fine and very fine sands concentrated in the upwind (northwest) region of the barriers. By contrast, the contents of finest particles such as silt and clay were higher in the downwind (southeast) region of the sampling plots. For the study area, the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control, with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification. The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.
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