| Leymus secalinus,a perennial rhizomatous clonal grass with high forage value,widely distributed in the desertified grasslands of the Songnen Plain and Kerqin Sandy Land,and often forms a single dominant species community.L.secalinus has a strong capacity for vegetative propagation,and it mainly relies on vegetative propagation to maintain population regeneration in natural grasslands.In this study,sampling and quantitative index determination were performed by tracking and digging a single rhizome section under natural expansion conditions in Songnen Plain of Northeast China,and completely tracking and digging whole clones created by transplanting a single tiller.From the two levels of clones and modules,we comparatively analyzed the quantitative characteristics of modules in L.secalinus clones,module composition,storage capacity of rhizomes,productivity of tillers,tiller characteristics of different leaf ages,regularity of module growth,quantitative characteristics and plasticity of reproductive growth,etc.The purpose was to reveal the potential of vegetative propagation and the regularity of module growth in L.secalinus clones under conditions with enough growth space and without interspecific competition.This study can not only provide scientific accumulation of basic research for further study of clonal plant ecology,but also provide theoretical basis for the sustainable use and scientific management of L.secalinus.The main findings and conclusions are as follows:1.In the modules of different growing years of rhizome sections in L.secalinus,the cumulative length of rhizomes,the biomass of rhizomes,the number of rhizome nodes,the length of internodes,the biomass of tillers,the number of dormant buds on rhizome,the number of buds on rhizome,the number of dormant buds on tillering-node,and the biomass of total modules in second-year rhizome sections were all significantly greater than those in the first-year rhizome sections(P < 0.05).The quantitative traits of modules in the second-year experimental clones in L.secalinus were also significantly greater than those in the first-year.Among the coefficients of variation(CVs)in the total quantitative characteristics of the four samples of L.secalinus,second-year rhizome sections had the minimum CV in the number of rhizome nodes,which was 29.2%;first-year rhizome sections,the first-year and the second-year experimental clones all had the minimum CV in the length of internodes,and their plasticity were relatively minimal.They all had the greatest CV in the biomass of juvenile tillers on tillering-node,and their plasticity were relatively the greatest.The plasticity of biomass in tillers and rhizomes were greater than those of their number.The quantitative characteristics of all modules have great ecological plasticitybetween and within growing years in L.secalinus clones.Regardless of the rhizome sections or experimental clones,the degree of variation is consistent overall.2.The tiller height of the two growing years of rhizome sections increased with the increase of leaf ages in the two growing years of rhizome sections,and the average tiller height of each leaf age in second-year rhizome sections was higher than that of the first-year rhizome sections.In the structure of the number of tillers,the number of buds,and the biomass of tillers,the fewer leaf number grades accounted for a larger proportion for the first-year rhizome sections,while the middle leaf ages accounted for a large proportion for the second-year rhizome sections.The tiller productivity of both the two growing years of rhizome sections increased with an increase in the leaf ages.There were no significant differences between the two growing years(P > 0.05)except for tillers with three leaves in which the second-year rhizome sections was significantly greater than that of the first-year rhizome sections.3.After two growing seasons,the tillers and rhizomes of L.secalinus experimental clones both consisted of two age-classes.The number of tillers,the biomass of tillers,the cumulative length of rhizomes and the biomass of rhizomes all showed an increasing age structure.The 1a-tillers had the greater productivity and contributed more to the clones.The1a-rhizomes had the greater material storage capacity,which were the main storage place for nutrients of L.secalinus.There were no significant differences in tiller productivity and material storage capacity of rhizomes among different age-classes(P > 0.05),and the ecological plasticity of tiller production and material storage of rhizome was larger in L.secalinus clones.4.In the rhizome bud bank of L.secalinus,the module composition ratio changed greatly between two growing years.Among rhizome sections of L.secalinus,the ratio of dormant buds on rhizome was 24% for the first-year rhizome sections and 31% for the second-year rhizome sections,and the ratio of active buds on rhizome was 35% for the first-year rhizome sections and 22% for the second-year rhizome sections.In the experimental clones of L.secalinus,the ratio of dormant buds on rhizome was 25% for the first-year clones and only 10% for the second-year clones,the ratio of tillers was 35% for the first-year clones and 42% for the second-year clones.The output of the tiller bud bank is relatively stable.Among the two growing years of rhizome sections and the first-year experimental clones,the dormant buds were the most,followed by the active buds and the juvenile tillers were the least in the output of bud bank.In the second-year experimental clones,the active buds were the most,followed by the dormant buds and the juvenile tillers were the least in the output of bud bank.During the continuous renewal and further expansion of L.secalinus clones,the potential of first-year rhizome sections was less than that of the second-year rhizome sections,while the potential of first-year experimentalclones was much greater than that of the second-year experimental clones.The output of tillers of experimental clones contributed more to the growth of the entire clone.5.The tiller productivity of the second-year rhizome sections of L.secalinus was significantly greater than that of the first-year rhizome sections(P < 0.05),and the vegetative fecundity of rhizomes of the first-year rhizome sections was significantly greater than that of the second-year rhizome sections,and the material storage capacity of rhizomes and the vegetative fecundity of tillers of the two growing years of rhizome sections were roughly the same(P > 0.05).In the experimental clones,the material storage capacity of rhizomes and the productivity of tillers in second-year clones were significantly greaterer than those of the first-year clones,and the vegetative fecundity of rhiozmes and tillers in first-year clones was significantly higher than those of the second-year clones(P < 0.05).6.The number and biomass of modules in L.secalinus clones followed certain rules.For example,with the increase of the cumulative length of rhizomes,the total number of buds and juvenile tillers of two growing years of rhizome sections increased significantly(P< 0.01)by a linear function,and the total biomass increased significantly(P < 0.01)by an exponential function.If taking the first-year and the second-year experimental clones as a whole sample to analyze,there was a significantly allometry growth process by a power function between the biomass of tillers and the number of tillers,and between the biomass of rhizomes and the cumulative length of rhizomes.With the increase of the cumulative length of rhizomes,the number of tillers,the biomass of tillers,and the total buds all increased significantly by a power function,and the number and biomass of total juvenile tillers both increased significantly by a linear function.7.Among the quantitative traits in the growth of the reproductive tillers of L.secalinus clones in two years,except for the height of the reproductive tillers,the length of inflorescence,the number of florets,the ratio of reproduction growth,and the ratio of stem biomass allocation,there was significant differences between the two years for the other quantitative traits(P < 0.05).Each quantitative characteristics had great plasticity.There was a significantly(P < 0.05)or extremely significantly(P < 0.01)positive correlation between the length of inflorescence,the biomass of inflorescence,the biomass of reproductive tillers and the height of reproductive tillers;between the length of inflorescence,the biomass of inflorescence and the biomass of reproductive tillers;between the biomass of each module and the height or biomass of reproductive tillers in L.secalinus clones over the two consecutive years,except for the relationship between leaf biomass and height of reproductive tillers in 2019.There was a significantly(P < 0.05)or extremely significantly(P < 0.01)negative correlation between the ratio of reproduction growth and the height of reproductive tillers,between the reproductive allocation and the biomass of reproductive tillers in 2018;however,these relationships were not at a significant level in 2019(P > 0.05). |
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