A Study On The Micro-structural Eco-plasticity Of Stem And Leaf Of Leymus Chinensis And The Plant Functional Groups Diversity Of Communities Along Northeast China Transect (NECT)

The terrestrial transect researches is an effective platform for global change study sponsored by the International Geosphere-Biosphere Programmer (IGBP). At present, there are 15 terrestrial transects in the world, and many experiments were conducted along the transects. Most of these studies have focused on environmental gradient analysis, effects of climate on primary productions, and relations between vegetation and climate changes and land use. Studies on physiological adaptation of some key stone species to climate change were more, but studies on their micro-structural adaptation were less. Studies on plant stomatal density were more, but studies on else micro-structure of stem and leaf were less.Northeast China Transect (NECT) is one of the terrestrial transects in the world and has become an important study platform of ecology and geography in China. Many experiments were conducted based on Northeast China Transect for many years. Here we aimed at an key stone species, Leymus chinensis distributing widely along the west part of Northeast China Transect, and studied micro-structural eco-plasticity of stem and leaf of Leymus chinensis and relations with water use efficiency, and then analysed the mechanism of Leymus chinensis adapting different habitats and especially water change of habitats, and then offered some theoretical basis for explaining the developmental trends of Leymus chinensis and its dominated populantions, communities and ecosystems.On the basis of the third field survey of Northeast China Transect in July-August, 2001, using high precise Olympus microscope and C isotopes technology, we analysed relations between micro-structure of stems and leaves, water-use efficiency of Leymus chinensis and environmental factors including soil water, altitude, mean annual precipitation and mean annual temperature during 10 years of every sampling plots. And then we analysed relations between environmental factors and the biomass, species diversity and plant functional types of communities.These results showed: the surface and inside micro-structures of Leymus chinensis leaves at the different sampling plots have obvious difference to some extent, of which relations between the stomatal density and annual precipitation, and between stomatal size and soil water were linear function; and the cutin layer thickness change has closer correlation with sampling plot altitude, this micro-structural changes may be propitious to decreasing the harm from ultraviolet radiation; changes of ridio of motorcell zone to leaf area were affected by temperature, and the adjustments of motorcell zone and stomatal density formed a cooperated mechanism adapting relative arid and high temperature; the surface down changes of leaves were evidently different between sampling plots, but relations between these changes and 4 environmental factors was not obvious, only leaf down density and length were evidently increased in the environment with high soil water. In conclusion,in the micro-structural eco-plasticity of Leymus chinensis leaves, the adjustments of stomatal density and its open extent were most obvious, this structural adjustment was beneficial to the adaptation of Leymus chinensis to arid environment.In comparison with the changes of leaf micro-structure, changes of stem micro-structure of Leymus chinensis have not evident regularity, but the differences between sampling plots were obvious. The micro-structural adjustments of Leymus chinensis stems, for instance, stem diameter change, ground tissue thickness change and pith antrum diameter change, may have close correlation with soil nutrient or else environmental factors, but our studies cannot involve these contents.The relations between the water use efficiency of Leymus chinensis and annual precipitation, soil water were obvious negative linear function, that is, in the increasing of annual precipitation and soil water of sampling plots, the water use efficiency of Leymus chinensis was evidently decreasing, and water wasted by transpiration was increased. This physiolog...