Effects Of Interspecific Competition On The Strategies Of Spatial Expansion Of Leymus Chinensis And Hierochloe Glabra

The interspecific competition among plant species is identified as an important factor indetermining community structure, which can not only determine how many species and whichones coexistence but also affect population dynamics. Plants are known to respond toheterogeneous distribution of nutrients in the soil, and they also respond to the presence ofneighbouring roots. To discuss the effects of interspecific competition on the strategies ofspatial expansion of clonal plants, we designed a greenhouse experiment including twotreatment, single plant and mixture plant. Multi-patch heterogeneous environments weremanipulated by creating four patches filled with different nitrogen fertilizer (N) addition ratesof soil in a same pot. For the experiment, two clonal plants Leymus chinensis (Trin.) Tzvel.and Hierochloe glabra Trin. were used as our experimental materials. Both species weregrown in pots at four N levels and in two competition situations, namely "no competition"(single plant),"interspecific competition"(mixture plant). We applied no nitrogen, lownitrogen, medium nitrogen and high nitrogen patches with nitrate concentrations at0(N),5(N),15(N) and35(N) g/m~2in2011and2012. In the autumn harvest of2011, half of thespecies were lived through the winter, and they continued to be observed in2012. Weattempted to answer the three scientific questions:(1) Under heterogeneous habitat conditions,whether interspecific competition would change L. chinensis and H. glabra spatial expansiondirection?(2) Whether the interspecific competition could inhibit the response of L. chinensisor H. glabra to heterogeneous habitat?(3) How the interannual variability of competitionsituation about the clonal plants L. chinensis and H. glabra?The main conclusions and results were as follows:(1) In heterogeneous habitats of2011, L. chinensis was able to select favorable habitats(medium nitrogen patch), and the spatial expansion was determinate. However, when L.chinensis and H. glabra were mixed planted, interspecific competition changed the expansiondirection of L. chinensis. Different from L. chinensis, the spatial expansion of H. glabra wasnot determinate. Because of interspecies differences, as well as the different strategies to theenvironment between the two clonal plants, interspecific competition did not influence thespatial expansion of H. glabra.(2) Interspecific competition significantly inhibited the response of L. chinensis toheterogeneous habitat in2011. The rhizome bud numbers, internode length, total root lengthand the total biomass of L. chinensis in the favorable patches were all affected, whereas theresponse of H. glabra to heterogeneous habitats was not inhibited by interspecificcompetition. (3) The competitive situations of L. chinensis and H. glabra were different asinterannual variability. The inhibition of interspecific competition on L. chinensisdisappeared in2012, however, it inhibited the number of ramets, internode length, total rootlength and the total biomass of H. glabra.(4) Species traits and temporal scales may be important factors to affect the competitiveresults in the clonal plant species.