Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： Water is the most important limiting factor for plant survival, and the study of plant water utilization in desert has become the key to ecological protection and vegetation restoration program. In the sandy land at east shore of the Qinghai Lake, we focuses on three typical sand-fixing plants (Pinus syivestris var.mongolica, Populus simonii and Hippophae rhamnoides) as the research object. The potential water source (different levels of soil water) and the main water sources of plants under the influence of micro-topography were analyzed by hydrogen and oxygen stable isotope technology (δ18O and δD) and IsoSource isotope mixing model. The results show that: (1)the soil water content has micro-topography differences, manifested in the lower soil water content on the windward slope being higher than that on the top of the sand dunes and the middle of the windward slope, and the soil water content is at its highest value in September. (2)the δ18O value of xylem water is different in tree species under different micro-topographic conditions. The δ18O values of P. syivestris in the lowland of windward slope are the lowest, while those of H. rhamnoides and P. simonii are the lowest in the middle of windward slope. (3)there are significant seasonal differences in the main sources of water for different plants. In June, both P. syivestris and H. rhamnoides used deep soil water as the main source of water under different micro-topographic conditions, while P. simonii mainly used deep soil water at the top of sand dunes. Middle-layer soil water is more utilized in the middle and lowland of windward slope, but with the increase of precipitation, various tree species turned to mainly use shallow and middle soil water in September. In summary, the water use patterns of sand-fixing plants in alpine sandy land are influenced by micro-topographic conditions, and different species showed different degrees of response to precipitation.
Subjects: Geosciences >> Geography submitted time 2023-03-13 Cooperative journals: 《干旱区研究》
Abstract： This study aimed to study the shelter efficiency of Haloxylon ammodendron windbreak with different density and plant point distribution to provide scientific basis for optimizing the structure of windbreak in arid areas. With the field Haloxylon ammodendron as the prototype, windbreaks with three stand densities and four plant point distributions were designed, and their flow field and shelter efficiency were measured and analyzed by wind tunnel experiments. The corresponding label and“plant spacing × row spacing”of the windbreaks were as follows: A: 17 cm × 17 cm, B1: 34 cm × 17 cm, B2: 17 cm × 34 cm, and C: 34 cm × 34 cm. Results showed that (1) the area of wind speed deceleration region (U/U0 < 1) accounted for 78.06%, 70.41%, 74.36%, and 82.80% of the whole flow field of A, B1, B2, and C windbreaks, respectively; the area of weak wind speed region (U/U0 < 0.4) accounted for 22.46%, 0.73%, 5.91%, and 0%. (2) The higher the stand density, the lower the average wind speed under the canopy, but the faster the wind speed recovered at the leeside of windbreaks. The minimum wind speed was located at 11H, 15H, 15H, and 20H behind the A, B1, B2, and C windbreaks, respectively (H was the tree height). (3) The order of shelter efficiencies of the four windbreaks from large to small was A > B2 > B1 > C. The relationship between shelter efficiency and stand density was nonlinear. The ratio of wind reduction at the near surface was A:B:C≈6:3:2 behind the windbreaks. The density of afforestation should be determined based on the soil water carrying capacity in the practice of forestation. On this basis, the plant point distribution mode of“small plant spacing, large row spacing”should be preferred.
Subjects: Geosciences >> Geography submitted time 2020-06-02 Cooperative journals: 《干旱区地理》
Abstract： 针对陕西省关中区域1978-2017年的农业生产数据，在分析关中40 a农业粮食生产的趋势变化后，运用主成分分析法，对影响关中农业生产中的地理环境和生产投入等主要因素进行了评价研究。结果表明:(1)关中农业粮食生产的趋势变化呈现周期为3 }7 a的循环增长方式，平均每周期峰值增长率为4.5% o (2)主成分分析研究后得出，第一主成分全是地理因素指标，方差贡献率达到0.554，对关中地区农业粮食生产起着非常显著的决定影响作用，包括受灾农田面积(不含病虫害)、主要粮食作物播种面积、成灾农田面积(不含病虫害),有效灌溉耕地面积、耕地面积;第二主成分方差贡献率为0. 25，是影响粮食生产的重要因素和农业生产的生命补给。包括农业用电量、化肥、农用机械等生产资料投入和主要粮食作物稳产面积、劳动力投入因素指标;第三主成分为农药应用量，方差贡献率为0. 068，影响较小。主成分累计方差贡献为0. 872。通过对关中地区农业粮食生产变化的影响因素分析，可以为政府部门提出数据支撑和相关性的建议。
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