The Plant-soil Feedback Effect And Its Impact On Interspecific Competition Of Herbaceous Peatland Plants

Plant-soil feedback(PSF)refers to the process in which plants change the biotic and abiotic attributes of the soil environment during the growth process,and the changed soil then affects the subsequent plant growth.In the past two decades,research on plant-soil feedback has gradually increased,and related research has been widely used to reveal ecological processes at different scales,such as competition,succession,biological invasion,and the impact of global changes on ecosystems.Plant-soil feedback effects influence plant traits and the competition or coexistence relationship between plant species,however,the general pattern and mechanism of these effects are unclear.In wetland ecosystems,the research on the plant-soil feedback relationship and its impact on the plant interspecific competition is still very limited.In this study,Carex angustior,a common species in herbaceous peatlands,and Lysimachia davurica,a forb growing in wet shrub that gradually spreads to peatlands,were used as plant materials to set up plant competition in three plant-soil feedback experiments.Combined with the modern species coexistence theory,we try to deeply understand the interspecific competition relationship between peatland plants from the perspective of plant-soil feedback,and reveal the influence of soil on plant interspecific relationships.Firstly,the interspecific competition experiment was conducted in two different feedback soils conditioning by C.angustior or L.davurica in a short term under indoor conditions.The direction and magnitude of the PSF under submerging conditions were explored,and the effects of PSF on plant traits and competitive intensity,and competitive response ability were also explored.Secondly,the native soil for C.angustior(peatland soil)and native soil for L.davurica(wet shrub soil)were collected from the field and used as long-term feedback soil.The difference in PSF effect between sterilized and non-sterilized soil was detected,as well as the effect of PSF on plant traits and interspecific competition.Results from the short-term and long-term PSF experiments were compared to explore the consistency of PSF effects and its impact on plant interspecific competition.After calculating the niche difference and fitness ratio between C.angustior and L.davurica,the role of soil organisms in PSF effect and interspecific competition was discussed combined with the modern coexistence theory.Finally,based on the second experiment,we explored how the PSF effect responds to lowing water level,and whether this response changed the competitive relationship between plants.Below are the key results:(1)In the short-term PSF experiment,although C.angustior showed an obvious PSF effect,it did not change the interspecific competition intensity,nor did it affect the competitive response ability of plants.This may be because the PSF effect does not affect interspecific competition under the conditions of this experiment,or because the conditioning effect of soil by plants is insufficient to alter the interspecific competition as the conditioning period for soils was too short.The root/shoot ratio of C.angustior and the nitrogen and phosphorus concentrations in the roots of the two plants were significantly different in the two conditioning soils,indicating that different adjusting soils have different effects on plant traits.(2)In the long-term PSF experiments,the PSF effects of plants were different,and the interspecific competition intensity and competitive response ability of plants were changed.Plant traits including height,specific root length and nitrogen and phosphorus content of plants were sensitive to PSF effect.Results for the sterilized soil showed that soil organisms regulated the PSF effect,which in turn led to significant changes in the interspecific competition intensity and competitive response ability of plants.Removing soil organisms would lead to the competitive exclusion of the two species.Results of the niche difference and fitness ratio from modern species theory showed that the soil organisms in peatland soil were the main regulators of plant coexistence,mainly by reducing the fitness ratio between plant species.By comparing the results from long-term and short-term PSF experiments,we proposed that there is uncertainty in indicating and predicting the PSF effect in natural communities and its impact on plant interspecific competition based on results from short-term PSF experiments.(3)In the lowing water level experiment,the PSF effect of plants was similar.PSF did not affect the plant interspecific competition intensity but changed the competition response ability of plants.The nitrogen and phosphorus contents of the roots of the two plants were sensitive to the PSF effect.Soil organisms still regulated the PSF effect after the water level dropped.Although the impact on the competition intensity and competitive response ability between plant species did not reach a significant level,removing soil organisms may destroy the coexistence relationship between the two species.Results of niche difference and fitness ratio from modern species theory showed that both soil organisms of peatland and shrubland soil improve plant coexistence more stable by expanding the niche differentiation between plant species.After comparing results from the two water level conditions,it is believed that the lowing water level affected the PSF in the wetland ecosystem,which in turn led to significant changes in the interspecific competition intensity and competitive response ability of plants.In summary,this study indicate that the PSF effect of plants in short-term conditioning soil has no significant effect on interspecific competition,but the PSF effect in long-term conditioning soil has a significant impact on interspecific competition.The presence or absence of soil organisms significantly affects the PSF effect of peatlands,and soil organisms are the main PSF effect regulators for the peatland plants coexistence.Water level not only affects the PSF effect but also changes the interspecific competition relationship of plants.Under submerging conditions,soil organisms promote plant coexistence by reducing the fitness ratio among plant species,while by expanding the niche differentiation among plant species when the water level drops.This study will help to understand the mechanism of plant interspecific competition and the community assembly from the perspective of plant-soil feedback,provide scientific basis and theoretical support for revealing the succession of wetland ecosystems,and will also expand the research perspective and approach for global ecological events such as biological dispersal and climate change.