Adaptive mechanisms of seven psammophytes in an arid desert margin in Shapotou area,China

Studies on plant adaptation strategy in extreme habitats from arid desert areas help to reveal the mechanism of plant community succession,predict ecosystem stability and succession orientation,as well as provide theoretical grounds for sand-binding engineering and revegetation.In this paper,we investigated the adaptation strategies of seven dominant plant species in different communities in a transitional zone of shifting-fixed dunes. The pioneer annual,Agriophyllum squarrosum,was found to possess a high transpiration rate( Tr),high peak of water use efficiency( WUE),with WUE peak occurring at relatively low soil moisture,while the intrusive species,Eragrostis poaeoides,behaved in conservative water use characteristics( low Tr,low WUE peak,with WUE peak occurring at relatively high soil moisture). For the seven species,we defined three types of water use characteristics: lavish water use( including Agriophyllum squarrosum,Hedysarum scoparium, Artemisia ordosica, Salsola ruthenica), moderate water use( Corispermum mongolicum),and conservative water use( Bassia dasyphylla,E. poaeoides).Species coverage of all the dominant species including shrubs and herbs was significantly negatively correlated with their diurnal transpiration under the conditions of rhizosphere moisture( R2= 0.94,P0.01). The results indicate that both the water use characteristics of different species and the distribution of soil moisture are the two major factors mediating the dominance of plant species in the community,soil water balance and succession processes in arid desert-oasis ecosystems. Soil physicochemical properties play an important role in the fixed and semi-fixed dunes,while soil moisture effects are more important in shifting and semi-shifting dunes.