Effects Of Clonal Integration On Grazing Tolerance Of Leymus Chinensis In Heterogeneous Environments

Grazing time and intensity, and resource availability can affect plant tolerance toherbivory. Leymus chinensis which is a typical clonal plant with rhizome connection is thedominant species in Songnen Grassland. However, the ecological mechanism how clonalintegration affects grazing tolerance of this species remains unclear. In this study, the clonalramets of L. chinensis were selected as our study materials to determine the physiologicalinfluences of biological factors (grazing) and abiotic factors (water and nutrient heterogeneity)on clonal plants. It was further analyzed benefits and costs of clonal integration under thecombined effects of resource heterogeneity and simulated grazing (clipping). To achieve thesepurposes, the uniform clonal ramets were transplanted into plastic pots (50cm×25cm×20cm). Within different water or nutrient heterogeneous treatments, the objective ramets werefurther subject to clipping treatments. The main results and conclusions were as follows:(1) Both nutrient heterogeneity and clipping treatments would jointly affect the effects ofclonal integration on plants. Within the light and moderate clipping treatments, clonalintegration had a positive effect on plant growth, reproduction and tolerance to herbivory.Support from the connected clonal ramets improved the biomass of L. chinensis by resourcetransportation. The significant interactions of resource (nutrient, water) heterogeneity andlight clipping obviously affected the biomass distribution pattern of L.Chinensis in this study.(2) Within low-high (L-H) nutrient heterogeneity and moderate intensity of clippingtreatments, clonal integration within connected ramets improved plant defense to herbivory.However, the improving effects were not found under the interactions of water heterogeneityand clipping treatments.(3)Under the interactions of environment heterogeneity and clipping, nitrogentransportation mainly occurred among the stems and the leaves of L. chinensis. However, theobvious nitrogen transportation in root systems was not found in this experiment.(4) When resource heterogeneity and herbivory together occur in the natural ecosystems,there is the obvious tradeoff between benefits and costs of clonal integration. Clonalintegration had a positive effect on the growth and reproduction of L. Chinensis under thecombined effects of nutrient heterogeneity and moderate grazing, reflecting the net benefits ofclonal integration. Conversely, water heterogeneity and clipping jointly reduced the netbenefits of clonal integration.