Several Trade-Offs In The Adaptive Strategies Of Three Rhizomatous Clonal Plants To Sandy Environment In Arid Sand Dunes

Desertification has become a global ecological and environmental problem,and the restoration and reconstruction of vegetation in arid sand dunes have attracted extensive attention from many scholars.The coexistence of wind and sand disturbance and environmental stress in arid sand dunes is a serious threat to plant survival and reproduction.Clonal plants,by virtue of their physiological integration,risk-sharing,high offspring survival rate and competitiveness,occupy a dominant position in arid sand areas,and their population expansion plays an important role in the restoration and reconstruction of sand areas.Rhizomatous clones have large and extensive belowground rhizome systems,strong adaptability to harsh habitats,and strong lateral spread and vegetative reproduction ability,which make them dominant in different types of sand dunes and are often selected as target species for sand consolidation and vegetation restoration.Therefore,it is important to carry out research on the adaptation strategies of rhizomatous clones to sandy environments for vegetation restoration and desertification control in arid sand dunes.In view of this,this thesis takes three rhizomatous clones of Phragmites australis,Psammochloa villosa and Inula salsoloides in Ulanbuh desert of Inner Mongolia as research objects.The characteristics of reproductive and vegetative growth,sexual and vegetative propagation,vertical and horizontal growth of three rhizomatous clones under different sand burial depths and soil moisture conditions were investigated,as well as the existence of potential trade-off relationships.In order to elucidate several trade-offs for the adaptation of rhizomatous clones to sandy environments,predict the population and community structure and dynamics of rhizomatous clones,and provide an important theoretical basis for vegetation restoration and reconstruction in arid sand dunes.The main findings are as follows:1.Rhizomatous clones can adapt to sandy environments by trade-off between reproductive and vegetative growth.With the increase of sand burial depth,plants weakened reproductive growth and enhanced vegetative growth,and the number ratio of reproductive ramets significantly decreased and the number ratio of vegetative ramets significantly increased(p<0.05).No trade-off existed between reproductive and vegetative growth of rhizomatous grasses under soil moisture changes,while a clear trade-off existed between the two in I.salsoloides and was consistent with the trade-off response to adaptation to sand burial.Both drought and sand burial stresses tended to reproductive growth,and as the degree of stress decreased,I.salsoloides tended to vegetative growth,the number ratio and biomass ratio of reproductive branches significantly decreased,and the number ratio and biomass ratio of vegetative branches significantly increased(p<0.05).2.Rhizomatous clones can adapt to sandy environment by trade-off between sexual and vegetative propagation.The number ratio and biomass ratio of panicle of rhizomatous grasses significantly decreased and the number ratio and biomass ratio of buds significantly increased with increasing sand burial depth(p<0.05).Under mild sand-buried conditions rhizomatous grasses tend to input more resources into inflorescence-based sexual reproduction,while under severe sand-buried conditions they tend to rely on bud-based vegetative propagation,in contrast to the I.salsoloides trade-off.Similarly,rhizomatous clones can trade-off resource inputs between sexual and vegetative propagation to deal with changes in soil moisture.The number ratio and biomass ratio of panicle were negatively related with soil moisture,while the number ratio and biomass ratio of bud were positively related with soil moisture(p<0.05).With increased soil moisture,sexual propagation potential gradually decreases,while vegetative propagation potential gradually increases.3.Rhizomatous clones can adapt to the sandy environment by trade-off between vertical growth and horizontal expansion.The number ratio and biomass ratio of rhizome buds significantly decreased and the number ratio and biomass ratio of tiller buds significantly increased with increasing sand burial depth(p<0.05).Under mild sand burial conditions,plants tend to rely on rhizome buds for horizontal expansion and population expansion,while under severe sand burial conditions,they rely more on tiller buds for vertical growth to resist sand burial disturbance.Similarly,rhizomatous clones can trade-off resource inputs between vertical growth and horizontal expansion to deal with changes in soil moisture.The number ratio and biomass ratio of rhizome buds were negatively related with soil moisture,while the number ratio and biomass ratio of tiller bud were positively related with soil moisture(p<0.05).With increased soil moisture,the horizontal expansion potential gradually decreases and the vertical growth potential gradually increases.In conclusion,there were differences in the trade-off responses between reproductive and vegetative growth of the three rhizomatous clones during their adaptation to changes in sand burial depth or soil moisture,while their trade-off responses between sexual and vegetative propagation and vertical growth and horizontal expansion were all consistent.i.e.,rhizomatous grasses tend to be reproductive growth under mild sand burial conditions and vegetative growth under severe sand burial conditions,in contrast to the trade-off response between reproductive and vegetative growth of I.salsoloides in adapting to changes in sand burial depth;No trade-off response between reproductive and vegetative growth exists for rhizomatous grasses under soil moisture changes,while I.salsoloides tends to reproductive growth under drought and vegetative growth under suitable conditions;The vegetative propagation and vertical growth of the three rhizomatous clones were enhanced with increasing sand burial depth or soil moisture,and their sexual propagation and horizontal expansion were limited.These trade-off strategy reflect the optimal resource allocation of rhizomatous clones in sandy environments,essential for enriching the theory of clonal plant adaptation to sandy heterogeneous environments and spatial expansion,promoting research on functional and restoration ecology of clonal plants,and guiding vegetation restoration and reconstruction in arid sandy areas.