| Loess hilly region is one of the most serious soil erosion areas in China. Due toenvironmental constraints, the reconstruction of vegetation are facing some difficult problems.The natural recovery is slow, and artificial vegetation is not sustainable and cannot produceexpected effect in soil and water conservation. The restored vegetations can’t meetenvironmntal requirements of social and economic development. How to construst plantcommunities to adapt to the environment of loess hilly region is significant to the vegetationrestoration. For these reasons, we choose loess hilly region as study area, and investigated98zonal species along the rainfall and temperature gradient in32sample plots, and measuredplant functional traits of leaf area (LA), specific leaf area(SLA), root nitrogen concentration(RNC). We then analyzed the influence of climate gradient on plant functional traits in loesshilly-gully region, and explored the variation of plant functional traits along theenvironmental gradient. We studied the scale dependence of plant functional traits and itscomponents at community and species levels, and discussed the main effect of driving forceof vegetation community assembly in loess hilly region. The main results are as follows:(1) In the loess hilly region, along the environmental gradient (temperature rising andprecipitation increasing), the community mean LA increased gradually, SLA decreasedgradually, but RNC had no significant change. It showed that species with highphotosynthetic ability, long life span and strong leaf defense capability become morerepresentative along the environmental gradient. They used the strategy of improving nutrientuse efficiency and reducing the growth rate to adapt to the environment.(2) Plant functional traits (take SLA and RNC for example) are significant differentamong the communities in the study area. In loess hilly region, SLA and RNC increasedaccording to the order (arbor-shrub-herb), which indicated that different plant communities inthe study area has taken a various ecological strategy to adapt to the environment. Therelationship of community niche breadth calculated by community mean SLA and RNC areas follow: arbor <shrub <herb. It shows that herb community and shrub community hadwider distributions than arbor community in loess hilly region.(3)Plant functional traits(taking SLA and RNC for example) in loess hilly region had difference within community. Within community, the range of component was larger thancomponent among species. This result suggests that the variation in plant species’ SLA andRNC, with respect to symbiotic species, was higher compared with the change alongcommunity average traits gradient. In loess hilly region, biological role played larger effect inbuilding community than environment. The SLA change of trees,shrubs and herbs in SLAgradient was larger than that among species within community. At the same time, the RNC ofshrubs and herbs within community was larger than that among species, while the RNC oftrees had no significant changes.(4) Plant functional traits had different relationships on community and specie level.On community level, LA and SLA has no significant correlation; LA had strong negativecorrelation with RNC; The correlation between SLA and RNC was weak positive. Thedependent relationships between plant functional traits and its components are different. Thecorrelations among LA, SLA and RNC has differences between species level and communitylevel. On species level, the species mean LA had no correlations with SLA, LA had weakpositive correlations with RNC. While SLA had no correlations with RNC. The correlationsamong traits component was that component of three traits had no significant correlations.component of LA and SLA had strong negative correlation, component of LA and RNCalso had strong negative correlations. component of SLA and RNC had no significantcorrelations. |
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