Abstract

The water availability in dry steppes during various active growing seasons is analyzed for the first time. Climatic fluctuations are examined, and their specific features are determined. Contrary to the popular opinion that the maximum precipitation in the steppe zone occurs during the summer period and that this is a distinctive feature of the steppe zone that is applicable to all its subzones, analysis of dry steppes in the Lower Volga Region over a period of 64 years shows that the maximum precipitation is attributed to summer only in 39% of the studied years, to spring in 27% of the years, and to fall in the remaining 34% of the years. Analysis of the water availability time series produced for various seasons covering more than a semicentennial period shows a general trend: the summer precipitation is decreasing, while the precipitation in spring and fall is increasing. The application of the exponential smoothing method to the time series and regression analysis indicate a growth dynamics of water availability in the spring period after the watershed years of 1989 and 1990 (the data validity is confirmed by the Student’s t-test; the probability value is 0.0005) amid a decrease in the fall precipitation (the probability value is 0.01). These trends characterize the demutation processes ongoing in the secondary fallow phytocoenoses, which are manifested by the predomination of loose- and firm-bunch grasses: water availability in late spring (May) and early summer (June) plays a critical role in the generative process of these plants. In total, 28 species belonging to the Poaceae family have been identified in the studied phytocoenoses; their share in the total species richness is 24.5%. The water availability patterns indicate aridization of the climate in dry steppes. The presence of ephemeral and ephemeroid plants in the communities additionally confirms this: the spring precipitation is their key life support factor. The ephemeral and ephemeroid species constitute 8% of the total species richness.

中文翻译：

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干草原的气候波动及其在mut变过程中的作用

摘要

首次分析了各个活跃生长季节干草原中的水分供应。检查气候波动，并确定其特定特征。与普遍认为草原区的最大降水发生在夏季期间相反，这是草原区的一个显着特征，适用于所有分区，对下伏尔加河地区的干草原进行了分析。 64年表明，最大降水量仅归因于研究年份的39％的夏季，27％的春季和其余34％的秋季。对一个半世纪以上的各个季节产生的可用水时间序列进行分析表明，总体趋势是：夏季降水在减少，而春季和秋季的降水在增加。指数平滑法在时间序列上的应用和回归分析表明，在1989年和1990年的分水岭之后的春季，可用水量的增长动态（数据有效性已由Student'sŤ-测试; 在秋季降水减少（概率值为0.01）的情况下，概率值为0.0005。这些趋势表征了次生休克植物基因组正在进行的mut变过程，其表现为松散的和坚硬的草丛的优势：春季后期（5月）和夏季初（6月）的水供应在生成过程中起关键作用。这些植物。在所研究的植物表皮酶中，总共鉴定出28种属于禾本科的物种。它们在总物种丰富度中的份额为24.5％。可用水量模式表明干旱草原气候干旱。社区中的短暂和类星体植物的存在进一步证实了这一点：春季降水是它们关键的生命支持因素。