| Grasslands are the most widely distributed and largest natural ecosystem in terrestrial ecosystems,accounting for about one-third of the global land area.The productivity of grassland plant communities affects the process of material cycling and energy flow in grasslands,and is an important part of the function of grassland ecosystems.As different organs of organisms perform different functions,the energy allocation patterns of grassland plants affect many processes such as carbon cycling in grassland plant communities.The pattern of energy allocation is a direct reflection of the response of plants to changes in environmental factors.Due to environmental changes and human disturbances,soil salinization has increased in Songnun grassland.Therefore,a comprehensive understanding of the biomass allocation characteristics of soil salinity degradation on the individual and community levels of common forage grasses in Songnun grassland can help us understand the plant response to soil salinization.To investigate the changes of individual and community biomass allocation patterns of common forage grasses during soil salinization,this study was conducted by sampling common species and communities of different plant communities in Songneng grassland,combining interspecific anisotropic analysis,intra-population anisotropic analysis and community-weighted anisotropic analysis to investigate the individual and community biomass allocation patterns of common forage grasses in Songneng grassland.The results found that:(1)The cross-species level biomass patterns were consistent with the heteroscedastic allocation theory,where plant stem biomass significantly influenced plant leaf biomass and reproductive biomass,and plant fecundity was the result of plant reproduction and nutrition trade-offs and plant seed size and number trade-offs.Despite the presence of significant phylogenetic relationships,the phylogenetic correction still showed the same results.However,soil salinization did not affect the biomass allocation pattern at the individual level in common species,and there was no significant trend in individual plant size and biomass of each organ at the soil salinity degradation gradient,nor did the anisotropic index between stems and leaves show a significant trend with salinity gradient.This indicates that there was no significant effect of environmental factors on plant biomass allocation at the individual level.(2)At the population level,the average height of common species decreased with increasing soil salinity,and variability also decreased,with nutritional and reproductive plants showing the same trend,but the average height of reproductive plants did not show a significant trend with increasing soil salinity.The same trend was found in the legume hoodia,the aster family fineleaf bittercress,the perennial herb lambsquarters,and the annual grass dogwood communities,where the mean height of dogwood populations increased with decreasing soil salinity,indicating that annual plants are at a competitive disadvantage when soil nutrients are sufficient.Soil salinization affected the biomass allocation pattern at the population level of common species,with the anisotropic index between stem-leaves showing a significant decreasing trend as soil salinity decreased.The anisotropy index between leafpropagation showed a significant increasing trend,which indicated that the allocation of plant biomass at the population level was influenced by environmental factors.(3)At the community level,soil salinization did not significantly affect the productivity of plant communities and the total biomass of each organ;on the contrary,soil salinization had a significant effect on plant community structure,and plant community species richness,Shannon-Wiener index,evenness index,and phylogenetic diversity index all showed a significant increasing trend,and it was also found from the phylogenetic tree that as the degree of soil salinization increased,the species of plant communities are closer together on the phylogenetic tree,which means that the similarity of plant traits is higher in communities with more salinization.Therefore,soil salinization significantly influenced the biomass allocation characteristics at the community level,consistent with the trend of biomass allocation at the community level,and as soil salinization increased,plants preferred to allocate biomass to stems and reproduction to ensure plant growth and reproductive processes,which in turn improved their adaptability to the environment.In summary,this study investigated the effects of soil salinity on biomass allocation processes of common forage grasses in Pinelands at the individual and community levels and elucidated the differences between biomass allocation strategies at the individual and community levels.Although biomass allocation at the individual level was not affected by soil salinity,it had completely opposite results at the plant community scale,i.e.,soil salinity affected the biomass allocation pattern at the plant community level,and this change in allocation strategy may be due to changes in plant community structure.This study provides new insights into plant community adaptation to environmental gradients and provides ideas for accurate prediction of plant growth processes under environmental gradients and exploration of plant adaptation strategies. |
