| Leaves are vital oegans of plants for getting resources and sensitive to environmental change. Its nutrient composition can not only reflect plant ecological stategies, but also a characterization of plants to adapt habitat conditions. Leaf traits can not only explain the distribution and the mechanism of plants to adapt the environment under different environmental gradients, but also predict the important response of ecosystems to environmental change. Nutrent resortion is known to be one of the most important strategies employed by plants to conserve nutrients prior to senescence. It is not only an adaptation evolutionary strategy for plants in nutrient-poor environment, but also important countermeasures of plants for preserving nutrient, enhancing competitiveness and improving nutrient use efficiency and productivity. Due to structural characteristics and nutrient content composition of leaves will vary with climate, soil and environmental factors, therefore it is better to elucidate the mechanism of leaf physiological and ecological resonse to environmental change on studying leaf traits and nutrient resorption in different habitats.In this study, we selected limestone karst ecosystems and sandstone evergreen broad-leaved forest ecosystem woody plants as the main object of study. Plants were divided into two life forms of evergreen and deciduous species which were compared to study. Leaf dry matter content (LDMC), specific leaf area (SLA), leaf thickness (LT), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), leaf potassium concentration (LKC) and leaf nitrogen phosphorus ratio (N:P) were measured respectively. Firstly, we compared leaf traits and nutrient resorption of evergreen and deciduous species for each ecosystem respectively. Lastly, we compared leaf traits and nutrient resorption of the two ecosystems. The main results showed that:1. Compared of evergreen and deciduous species in limestone karst ecosystem: as to leaf traits in both mature and senesced leaves, LDMC and LT of evergreen species were both significantly bigger than deciduous species, while SLA was smaller than deciduous species, LNC, LPC, LKC and N: P were no significantly difference. Compared of mature and senesced leaves in the same life form plants, SLA, LT and N: P were no significantly difference between mature and senesced leaves of evergreen species, but LDMC, LNC, LPC and LKC in mature leaves were significantly lower than senesced leaves. LDMC, SLA, LT and N: P were no significantly difference between mature and senesced leaves of deciduous plants, but LNC. LPC and LKC of mature leaves were significantly lower than senesced leaves. As to nutrient resorption efficiency, nitrogen and phosphorus resorption efficiency of evergreen species were higher than those of deciduous species, while potassium resorption efficiency of the evergreen species was lower than that of deciduous species. Nitrogen, phosphorus and potassium resorption efficiency of evergreen plants were39.42%、43.13、and32.48%.Nitrogen, phosphorus and potassium resorption efficiency of deciduous plants were25.79%、35.47%and34.82%. As to nutrient resorption proficiency, nutrient congtents in senesced leaves of evergreen species were lower than that of deciduous species, this indicated evergreen plants had higher nutrient resorption proficiency. Nitrogen, phosphorus and potassium contents in senesced leaves of evergreen plants were11.1mg/g,0.51mg/g and5.98mg/g. Nitrogen, phosphorus and potassium contents in senesced leaves of deciduoue plants were14.88mg/g,0.67mg/g and8.33mg/g.2. Compared of evergreen and deciduous plants in evergreen broad-leaved forest ecosystem in sandstone ecosystem: as to leaf traits between the mature and senesced leaves, LDMC of evergreen plants was significantly bigger than that of deciduous plants, but SLA, LNC and LPC of evergreen plants were significantly lower that of deciduous plants; LT and LKC were no significantly difference between evergreen and deciduous plants. Compared of mature and senesced leaves in the same type plants, LDMC, SLA, LT and N: P in matur and senesced leaves of evergreen species were no significangtly difference; but LNC, LPC and LKC were significantly lower than that in senesced leaves. Compared evergreen species, deciduous showed the same trend. As to nutrient resorption efficiency, nitrogen and potassium efficiency of evergreen plants were lower those of deciduous species, while phosphorus nutrient efficiency was no significantly difference between evergreen and deciduous plants. N, P and K resorption efficiency of evergreen species were31.49%,45.26%and31.66%. N, P and K resorption efficiency of deciduous species were44.45%,45.87%and45.31%. As to nutrient resorption proficiency, nitrogen and phosphorus in senesced leaves of evergreen species were lower that those of deciduous species, while potassium content was higher than that of deciduous species, this indicated evergreen plants had higher N and P resorption prociency. N, P and K content in senesced leaves of evergreen plants were12.19mg/g,0.35mg/g and8.35mg/g. N, P and K content in senesced leaves of deciduous plants were16.71mg/g,0.78 mg/g and7.60mg/g.3. Compared of leaf functional traits between two ecosystems: LDMC and LPC in mature and senesced leaves of evergreen plants in limestone habitat were significantly higher than those in sandstone habitat, SLA and N: P were significantly lower than those in sandstone habitat, LKC was no significantly difference between two habitats. LDMC of deciduous plants in limestone habitat was significangtly higher than that in sandstone habitat, SLA was significantly lower than that in sandstone habitat, LT, LNC, LPC and LKC were no significantly difference between two habitats. All plants in limestone habitat showed higher LDMC and lower SLA and N:P than sandstone habitat. While LNC, LKC, LT and LPC were no significant difference between two habitats.4. Correlation relationships of leaf traits between two ecosystems: There was a significant negative correlation in mature leaves of all plants between LDMC with SLA and SLA、SLA with LT、LPC with N:P. There was a significant potive correlation in mature leaves of all plants between SLA with LKC、LNC with LPC. There was a significant negative correlation in senesced leaves of all plants between LDMC with SLA、LPC with N:P. There was a significant positive correlation in senesced leaves of all plants between LNC with LPC.5. Compared of nutrient resorption between evergreen and deciduous plants in two ecosystems: as to nutrient resorption efficiency, N and K resorption efficiency of evergreen species in limestone habitat were higher than that in sandstone habitat, P resorption efficiency was lower than that in sandstone habitat. For deciduous species and all plants, N, P and K resorption efficiency in limestone habitat were all lower that in sandstone habitat. As to nutrient resorption proficiency, N and K contents in senesced leaves of evergreen species in limestone habitat were both lower than that in sandstone habitat, P contents was higher than that in sandstone habitat. This indicated plants in limestone habitat had higher N and K resorption proficiency and lower P resorption proficiency than sandstone habitat. N, P and K resorption proficiency of deciduous species and all plants in limestone habitat were all lower than that in sandstone habitat. This indicated plants in limestone habitat had higher nutrient resorption proficiency overall. |
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