The Study Of Response Mechanism Of Leymus Chinensis Clonal Integration Strategy To Cutting Under Saline-alkaline Environment

Clonal species as one of the unique group are widely distributed in various ecosystems and play an important role in the ecological system. Clonal integration refers to the nutrient transfer between the ramets. It is an important ecological adaptation strategy for clonal plant. Clonal integration is influenced by different biological factors, such as soil, light, temperature, grazing and so on. With the aggravation of the environmental heterogeneity, clonal plants adaptive strategy to environmental heterogeneity has become a hot research topic in the ecological field.Songnen plain is one of the main Saline-alkaline soil distribution area in China. In recent years, saline-alkaline and artificial grazing lead to Songnen grassland patches. Leymus chinensis is the dominant species of Songnen grassland. Leymus chinensis is an important rhizome clonal plant. It is considered as having strong resistance to saline-alkaline and grazing. However, there remains largely unknown about how L. chinensis responds to saline-alkaline under grazing condition and especially there is no information about how salt and cutting affect nutrient transfer direction and intensity by clonal integration.In the study, we conducted a double pot experiment, selected connected rhizome ramets of L. chinensis and used 15 N isotope tracer to study how saline-alkaline affects the direction and intensity of nutrient transfer between mother and daughter ramets under the cutting condition. Results showed that: at the morphological(tiller, terminal bud, internode bud) level, when single ramet were growing in saline-alkaline environment, cutting significantly reduced the tiller number of rhizome connected and untreated ramet, when both two ramets were growing in saline-alkaline conditions, cutting had no significant impact on tiller number of the two ramets. When daughter ramets were growing in saline-alkaline environment, cutting significantly depressed its growth of rhizome terminal bud and internode bud, while cutting significantly promoted the terminal bud growth of rhizome connected and untreated mother ramets;when mother or both two ramets were growing in saline-alkaline environment, cutting significantly reduced the terminal and internode bud growth of both two ramets. In regard of nutrient transfer, whichever ramets were growing in heterogeneous environment, the one that in homogeneous environment transfered nutrient to another ramet. When both two ramets were growing in saline-alkaline heterogeneous environment, nutrient transfer existed, but the degree differed with regards to different levels of ramets. Further analysis of 15 N isotope showed that: when the marked daughter or mother ramets were growing in saline-alkaline environment(saline-alkaline & cutting), cutting promoted the transfer of 15 N from daughter to mother ramets. Under saline-alkaline heterogeneous environment with cutting disturbance, 15 N transfer rate(42%) were significantly higher than the control treatment(22%); when marked mother ramets and both two ramets were growing in saline-alkaline environment, 15 N transfer rate of mother ramets was less than the control treatment.We conclude that nutrient transfer between ramets is two-direction, that is, nutrient transfer can occur between daughter ramet and mother ramet through connected rhizome; intensity of nutrient transfer among different ramets is selective. This selective performance shows that: when mother ramet is growing in the heterogeneous environment, daughter ramet will preferentially transfer nutrient to mother ramet and promote its growth(selfless-type); while when daughter or both ramets are growing in the heterogeneous environment, mother ramet only transfer a small amount of nutrient to daughter ramet and hold massive nutrient for its own growth to keep the population balance(“cost-benefit” type). The results provide a theoretical basis for the resistance to saline-alkaline and grazing mechanism of L. chinensis, and also provide sufficient data to support the ecological restoration of L. chinensis grassland.