Subjects: Geosciences >> Geography submitted time 2024-04-29 Cooperative journals: 《干旱区研究》
Abstract： Desert vegetation is an important ecological protection barrier for oasis ecosystems in the Hexi Corridor. Studying the composition of desert vegetation and the spatial distribution of soil nutrients is important to the construction and management of desert-oasis transition zone vegetation. This study is based on several field surveys. Traditional statistical and geostatistical methods were used to investigate the composition of desert vegetation and soil nutrient characteristics in the middle section of the Hexi Corridor and the southern fringe of the Badain Jaran Desert, and their correlation with environmental factors were analyzed. Results indicated that the plant composition in the desert areas of the middle section of the Hexi Corridor and the southwestern fringe of the Badain Jaran Desert was single and had low diversity, with plant species concentrated in a few families. Typical desert plants such as Reaumuria songarica and Nitraria tangutorum were frequently found in the study area. The distribution of herbaceous plants was strongly correlated with the average annual precipitation. In Shandan County, which is located in the southern part of the study area, the biomass of herbaceous plants reached 108.01 g·m−2. Within a certain range of annual precipitation, the biomass of shrubs increased with the increase of precipitation, with the highest value occurring in Suzhou County, near the northern slope of the Qilian Mountains, at 134.03 g·m−2. Increasing precipitation significantly promoted the growth of herbaceous plants. The surface soil had the highest organic carbon, total nitrogen, and total phosphorus contents in the study area, with average values of 2.12, 0.25, and 0.41 g·kg−1, respectively, and higher levels of variability than those in the soil subsurface. In the horizontal direction, the three types of soil nutrients had high variability and weak spatial autocorrelation, with maximum values of 11.22, 1.30, and 0.73 g·kg−1 near Zhangye Oasis. Principal component analysis showed that soil properties and precipitation were the primary factors causing habitat differences in the study area. However, different environmental factors interacted with one another to jointly drive desert vegetation composition and distribution.
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Basic Disciplines of Agriculture submitted time 2017-10-20 Cooperative journals: 《中国生态农业学报》
Abstract：为了探明弱光条件下小麦光合速率降低的原因, 为黄淮海麦区小麦生产中合理施氮和高产高效栽培提供理论依据, 通过田间试验研究了拔节期至成熟期弱光胁迫(透光率为50%的黑色遮阳网遮阴)和氮素水平 [N0, 0 kg(N)hm2; N1, 120 kg(N)hm2; N2, 240 kg(N)hm2]对冬小麦旗叶光合特性及产量的影响。结果表明:冬小麦拔节期至成熟期长期遮阴, 导致旗叶叶绿素含量、PSⅡ荧光光化学猝灭系数(qP)和实际光化学量子产量(ΦPSII)在3 个施氮水平下均显著增加, 其中以N2 施氮水平下增幅最大, 同时显著降低了叶绿素a/b 和荧光非光化学猝灭系数(qN), 进而提高了旗叶光化学效率, 降低了热能耗散, 提高光能利用率。在开花期至灌浆中期,由于光能不足造成小麦旗叶净光合速率Pn 降低, 而在灌浆后期, 遮阴处理较正常光照能维持较高的叶绿素含量和光能转化效率, 从而Pn 高于正常光照。在相同光照条件下, 随施氮量增加, 小麦旗叶净光合速率Pn、叶绿素含量、PSⅡ荧光光化学猝灭系数(qP)和实际光化学量子产量(ΦPSⅡ)显著提高, 这有利于植株充分利用光能,增强光合作用。弱光导致穗数、穗粒数及千粒重显著降低(P<0.05), 穗粒数降低幅度最大(13%~46.8%), 千粒重降低幅度最小(3.4%~8.5%), 穗数的降低幅度为8.6%~22.5%, 严重影响氮肥的增产效应。遮阴和施氮水平间交互显著影响了叶绿素含量、穗粒数和产量, 但对其他指标影响并不显著。综合而言, 增施氮肥缓解了弱光胁迫对光合作用的不利影响, 遮阴条件下施氮处理(N1、N2)净光合速率Pn 较对照(N0)增幅为11.5%~27.4%, 其中以N2[240 kg(N)hm2]水平增幅最大。在不同施氮水平下, 遮阴处理均提高了光能转化效率, 但遮阴显著降低了植株光合速率及产量构成因素, 导致产量显著降低(P<0.05)。
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