| Clonal plants are widely found in almost all types of ecosystems, and it is also an important component of wetland vegetation. Study on clonal plant population has become a frontier issue in population ecology. Clonal plants are always dominant in wetland vegetation.Therefore, comprehensive study on dominant plant population ecology is very important for understanding community succession. Using Situ observation and field sampling method combined with indoor experiment, we studied age structure, resource allocation, reproductive strategies and clonal architecture etc. biological and ecological characteristics of Carex lasiocarpa clonal populations in spatial ecological series of natural water gradient in Sanjiang Plain wetlands. The series included four communities without any anthropic disturbances:Carex lasiocapa+C. pseudocuraica community(P), C. lasiocapa community(C), C.lasiocapa+Glyceria spiculosa community(T), C. lasiocapa+Phragmites community(L), and C. lasiocapa community formed by being disturbanced of filling after 5 years(J). Results and conclusions were summarized as follows:(1) In different communities, C. lasiocarpa ramets consisted of 8 age classes of, and the rhizomes composed of 9 age classes. 3a, 4a, and 5a ramets were dominant and the age structures were stable. It showed that the C. lasiocarpa populations in different communities would maintain their advantage position in the communities within a certain time.(2) In different communities, the vegetative propagation rates of C. lasiocarpa ramets were relatively higher. 1a-7a ramets of C. lasiocarpa all had a capacity of vegetative propagation except for 8a ramets. And vegetative propagation rates of the ramets decreased with age increase.Interference to strengthen the tendency to vegetative propagation of C. lasiocarpa population; in the water gradient ecological series, the vegetative propagation tendency of C.lasiocarpa population would be to reduced with the rising of water. In addition, the interference of C. lasiocarpa population earlier entered to the vegetative reproduction.(3) The sexual reproduction rate of C. lasiocarpac lonal populations were lower generally in different communities, in the ecological series of water gradient, the water level effected on the sexual reproduction of C. lasiocarpa populations significantly, the sexual reproduction rates of ramets increased with the increasing of water; and the interference had no significant effect on the sexual reproductive rate of C. lasiocarpa population.The reproductive allocation including RAI and RAⅡof C. lasiocarpa clonal populationswere lower in each community. In spatial ecological series of natural water gradient, RAI increased with the increase of water and RAⅡ firstly decreased and then increased with the increase of water(it was the lowest in C. lasiocapa+G. spiculosa community). The reproductive allocation of C. lasiocarpa populations was not significantly different between filling disturbance and natural C. lasiocapa communities.1000-seed weight of C. lasiocarpa was significantly different among all communities and that of disturbed C. lasiocarpa community was significantly higher than that of natural monodominant community. In different communities of water gradient ecological series,1000-seed weight of C. lasiocarpa from the highest to the lowest was C. lasiocapa+G.spiculosa community, C. lasiocapa+C. pseudocuraica community, C. lasiocapa+ Phragmites community and C. lasiocapa community. Being soaked in acid and alkali solution increased germination rate of C. lasiocarpa. Being soaked in 10% Na OH solution for 60 min, the seed germination could be promote significantly and the average germination rate was about70.0%.(4) Resource allocation to vegetative reproduction was dominant in C. lasiocarpa populations and there was different among populations in all five communities. Effection of water gradients on aboveground biomass of C. lasiocarpa populations was significantly different. Furthermore, aboveground biomass gradually increased with the water increase and rhizome biomass decreased and then increased with the water increase.Potential of vegetative reproduction of C. lasiocarpa populations in disturbed community was significantly lower than that of its monodominant community. In communities of water gradient ecological series, the potential firstly decreased and then increased with the water increase. The biggest one was in C. lasiocapa+G. spiculosa community and the smallest one was in C. lasiocapa+Phragmites community.(5) The clonal architecture of C. lasiocarpa populations in different communities had“phalanx” strategy and “guerilla" trategy, and there were different in C. lasiocarpa populations.In water gradient ecological series, “phalanx” strategy of C. lasiocarpa populations enhanced with water increased, but "guerilla" of C. lasiocarpa populations weakened,furthermore, expansion distance of "guerilla" firstly decreased and then increased with water line.Branching angles were smaller and spaces were shorter in short rhizomes of C.lasiocarpa in disturbed communitiy. Ramets of C. lasiocarpa in distributed populations both in “phalanx” and "guerilla" were sparser.In conclusion, in different communities, vegetative reproduction was dominant in C.lasiocarpa populations. Compared with other populations, more resources of C. lasiocarpa were allocated to reproduction and low resources were allocated to growth. In water gradientecological series, proportion of vegetative reproduction of C. lasiocarpa populations reduced gradually and that of sexual reproduction increased gradually, but the seed proportion firstly reduced and then increased. “Phalanx” strategy of C. lasiocarpa populations enhanced with water increase, but "guerilla" of C. lasiocarpa populations weakened. Comparing with C.lasiocarpa population in the water gradient ecological series, C. lasiocarpa population in disturbed communities had higher proportion of vegetative reproduction, and it was in vegetative stage earlier, and the ramets grew sparsely. |
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