Study The Growth Costs And Benefits Of Clonal Integration Of Zoysia Japonica In Homogeneous And Heterogeneous Habitats Based On Soil N:P

Clonal integration is an important ecological strategy of clonal plant to adapt to the complex and variable habitats. In order to thoroughly understand the features and the growth costs and benefits of clonal integration under different habitat, the experimental study was conducted. The growth and biomass accumulation of clonal plant Zoysia japonica, which were grown under three homogeneous conditions based on three type of soil N:P ratios (N:P-7,14 and 21) undergoing four types of primary stolon severing treatments, i.e., connection, light severing, moderate severing and serious severing, were investigated, and the growth cost and benefits were analyzed. Moreover, the clonal plant Z. japonica were also grown under the heterogeneous habitats with three types of patch scales in term of soil nutrients based on soil N:P ratios, aiming to research the responses of Z. japonica to the different soil nutrient patch patterns, and the corresponding growth cost and benefits. The main results showed that:(1)The clonal growth characteristics of Z. japonica under the homogeneous habitats of soil nutrient:in any types of homogeneous habitats based on soil N:P ratios, when the stolons were kept connected, the growth of multiple nodes, A-ramet, the length and biomass of internode on the primary stolons showed strict regularities, fitting to the quadratic functions. In the process of the formation of ramet, root systems grew firstly, and then the above ground part grew. At the later developmental stage of ramet, the biomass allocation to the above ground part was far greater than that to the root biomass.(2)The growth costs and benefits of the clonal integration of Z. japonica under the homogeneous habitats of soil nutrient:compared with the treatment of primary stolons connection, the primary A-ramet number, multiple nodes number, the length, biomass and biomass allocation of primary stolon of Z. japonica were significantly decreased in the treatments of different severing levels of primary stolons, but the primary B-ramet number, secondary A-branches and B-branch number, mother ramet biomass, A-branch biomass allocation and B-branch biomass allocation were significantly increased. Z. japonica performed best in the homogeneous habitats with lowN:P (N:P≈7). The biomass allocation of Z. japonica plants to roots increased with the increase of soil N:P ratios. The total biomass of Z. japonica plants obtained maximal benefits at the habitats with low, moderate and high soil N:P ratios, and at the moderate severing, light severing and connection treatment on the primary stolon, respectively. Therefore, the clonal integration of Z. japonica was closely related to the soil N:P ratios in the habitats, and when the clonal integration period changed, the growth costs and benefits of Z. japonica clones also changed. The growth of primary A-ramet, primary multiple nodes and stolon got significantly benefits under long time integration, but primary B-ramet, secondary A and B-branch got a certain degree of costs.(3)The growth costs and benefits of Z. japonica under heterogeneous habitats of soil nutrient:compared with the control group C, the number of A-ramets, A-branch biomass, root biomass, stolon biomass, total ramet biomass and root length in the poor patches of the heterogeneous habitats of soil nutrient were significantly improved by the effects of clonal integration, however, the number of A and B-ramets, biomass, root length, root surface area and root volume growth indexes significantly reduced in the rich patches of the heterogeneous habitats of soil nutrient. The biomass allocation of Z. japonica in the poor and rich soil nutrient patches were significantly changed by the effects of clonal integration. Clonal integration significantly increased the number of A-ramets of the whole plant under the heterogeneous habitats of soil nutrient (Tl, T2 and T3), but significantly decreased the root morphological index (such as root length, root surface area, root volume and root average diameter), and the number and biomass of B-ramet, but did not improve the total primary stolon length and the total plant biomass.