Temporal dynamics of steppe plant communities

Abstract

Global climate change affects the conditions of ecosystems. However, the nature of changes induced by climatic factors remains unknown due to the complex nature of climatic transformations. The global trend of temperature increase is associated with an increase in precipitation and changes in its rhythm. The dynamics of plant communities under the influence of climate occurs against the background of natural successional phenomena. The aim of the study is to develop methodological approaches in order to identify aspects of vegetation variability that are caused by global climate change and give them an ecological interpretation. Geobotanical descriptions of vegetation in steppe ecosystems were carried out over the last 20 years. Exactly in this period dramatic climatic changes were observed, which allows to compare climatic and vegetation trends. For ecological interpretation the results of ordination of plant communities were explained with the help of phytoindication scales. Plant communities exhibit dynamics that are driven by endogenous and exogenous causes. These aspects of community dynamics were differentiated using the ordination procedure as different ordination axes. The axes that reflect endogenous dynamics were described using temporal variables. The axes that reflect exogenous dynamics were described using phytoindication scales. The phytoindication scales made it possible to assess the ecological directions of plant community transformation under the influence of global climate change. The transformation of the plant community under the influence of global climate change is inconsistent with the concepts of desertification. The revealed temporal patterns of the plant community have a complex and multidirectional trajectory. The plant community studied over the twenty-year investigation period exhibited a dynamic that is a superposition of two processes that are driven by the temperature and precipitation. The temperature trend is directional and reflects the tendency of global warming. This trend is accompanied by an increase in species richness and projective cover of the plant community. At the same time, thermophilicity and continentality of the community increase against the decrease of soil trophic status, acidity increase and soil carbonation decrease. Obviously, along with the mineralization of organic matter, the soil decarbonization can also be the cause of increased carbon dioxide emission into the atmosphere as a result of global warming. The trend, which is regulated by precipitation, is oscillatory. This trend changes the regime of moisture, light and cryoclimate of the plant community.