RESPONSES OF δ~(13) C VALUE AND WATER USE EFFIEICENCY OF PLANT SPECIES TO ENVIRONMENTAL GRADIENTS ALONG THE GRASSLAND ZONE OF NORTHEAST CHINA TRANSECT
SU Bo HAN Xing Guo LI Ling Hao HUANG Jian Hui BAI Yong Fei and QU Chun Mei (Laboratory of Quantitative Vegetation Ecology, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093)
Leaf δ 13 C values were measured in fifteen plant species along the grassland zone of the Northeast China Transect (NECT). The responses of δ 13 C values and long term water use efficiency (WUE) as indicated by δ 13 C value of these species to environmental factors (annual average precipitation, annual average air temperature and altitude) were investigated. The δ 13 C value and WUE of many plant species decreased with increasing annual average precipitation and air temperature. Examples of such species include: Leymus chinensis (Trin.) Tzvel., Ulmus pumila L., Caragana microphylla Lam., Astragalus adsurgens Pall., Sanguisorba officinalis L. and Potentila tanacetifolia Willd. ex Schlecht. Other species show an increase in δ 13 C and WUE with increasing altitude ( Melissitus ruthenicus (L.) Peschkova, Leymus chinensis (Trin.) Tzvel., Ulmus pumila L., Caragana microphylla Lam., Astragalus adsurgens Pall. and Sanguisorba officinalis L., for instance).By contrast, a few plant species (Lespedeza davurica (Laxm.) Schindl. and Serratula centauroides L.) showed an opposite trend. Finally several species showed no change in δ 13 C value or WUE with these environmental factors (e.g. Astragalus dahuricus (Pall.) DC., Caragana intermedia Kuang et H. C. Fu, Caragana stenophylla Pojark., Artemisia frigida Willd., Astragalus scaberrimus Bunge, Glycyrrhiza uralensis Fisch.). These results demonstrate strong differences in the responses of water use status to environmental gradients among different plant species and that each species has its own adaptive strategy to environmental change. When considering restoration of degraded grasslands it is important to consider variation between plant species in their potential to adapt to dry habitats.