Effects Of Above-ground And Below-ground Planting Configurations On Scirpus Mariqueter Colonization At Early Stage

Successful restoration of coastal wetlands hinges on recolonization of habitatforming species,In saltmarsh wetland,recolonization is limited by environment stress and negative effects between individuals.Traditional restoration paradigm is focus on minimizing negative effects(eg.competition)via dispersal configuration.The other paradigm is to maximize the positive interaction between individuals through the clumped configuration.Since the selection of optimal restorative configurations is context-dependent,little consideration is given to the effects of plant traits.In addition,the spatial configuration design only considered the above-ground configuration of plants,and the possible influence of the below-ground space configuration of plants was ignored.In order to figure out whether biotic attributes(such as differences in plant traits)and below-ground spatial configuration(rhizome connectance)of plants can affect rapid plant colonization in salt marsh wetlands,we designed transplant experiments and field investigations in Fengxian and Chongming Dongtan respectively,and the main results were as follows:(1)The restoration efficiency of different paradigms may depend on the species difference Two pioneer species,Scirpus mariqueter and Spartina alterniflora,were transplanted with different restoration paradigms in Fengxian tidal flat.By analyzing the density change rate and the final survivorship of transplanted plants,we found that scirpus mariqueter have a better performance in dispersed configuration,but Spartina alterniflora performs better in clumped configuration.We also found that there was a significant interaction between plant configuration and plant type on plant resistance.The results strongly suggest that differences in plant traits influence the relative importance of local facilitation feedback under variants spatial configurations.(2)The spatial design of below-ground configurations(rhizome connectance)affects the plant recolonization at early stage.Transplanting experiments of scirpus mariqueter were carried out in Dongtan,Chongming.The results showed that the early recolonization rate of Scirpus mariqueter perform better in dispersed configuration,and below-ground space configuration significantly affected the recolonization rate.The recolonization rate of high rhizome connectance was only half of that of low and no connections,and the area of vegetation expansion in low and no connections was twice that of high connectance.The growth rate of plant height had a better performance in low and no connectance treatment.These results indicate that high rhizome connectance may reduce the recolonization efficiency and moderate rhizome connectance may promote rapid transplanting of Scirpus mariqueter.(3)local positive effects affected the distribution of belowground rhizomes direction.Through the investigation of the growth direction of belowground rhizome of Scirpus mariqueter in different environmental stress and different positive feedback condition,we found that the growth direction of rhizome was sensitive to environmental stress.Scirpus mariqueter was more inclined to grow perpendicular to the tide in expose zone.In addition,it was also found that when the density of Scirpus mariqueter was low(the strength of local positive effects was weak),the rhizome of Scirpus mariqueter tended to grow perpendicular to the tidal direction,but with the strengthening local feedback(the local plant density increased),the rhizome of Scirpus mariqueter tended to grow in the tidal direction.The above result suggest that low rhizome connectance and dispersed configuration can amplified recolonization efficiency of Scirpus mariqueter at early stage.The result also emphasize the necessity of considerations on biotic attributes for restoration configuration designs by means of harnessing positive interactions,and advances the applications of facilitation theory in ecological restoration practices.