The Research On Leaf δ¹³C And Leaf Traits Of Dominant Species At Different Altitude Gradients In Castanopsis Carlessi Forests In Lingshshan National Forest Park

Castanopsis carlessi forests are important constructive species for the evergreen broad leaves forests. The characteristics and adaptation to environment of leaf have been one of the key and hot points of Ecology. For the first time, foliar stable carbon isotope ratio(δ¹³C) SLA, LDMC and nutrient content of different age leaves were investigated along the altitudinal distribution gradient of dominant species in Castanopsis carlessi forests in Lingshi shan National Forest Park. The variation ofδ¹³C and the leaf traits such as concentration of mineral nutrients, specific leaf area(SLA), leaf dry matter content(LDMC) between dominant species, leaf age and the different altitude gradient were analyzed. The relationship between foliarδ¹³C and leaf traits was studied by regression analysis and principal component. Also the influence of environmental factors on the value of foliarδ¹³C was analyzed. Meanwhile the correlation between leaf traits and its relation to environmental factors such as soil nutrient status, elevation and slope was studied. The main content of this paper were concluded as follows:The range of foliarδ¹³C value was between -34.52‰and -28.377‰, with an average of -30.885‰for Castanopsis carlessi forest in Lingshishan National Forest Park. The variance analysis showed that there was significant difference between dominant species at each altitude gradient except for A7 and A8. And there no significant difference for different age leaves. The frequency distribution of foliarδ¹³C become single along altitude gradient. Regression analysis showed the value of foliarδ¹³C was more positive with the increasing altitude, with an average change of 3.2‰? km-1.Closely related to photosynthesis, chloroplast pigments are vital factors to measure the intensity of photosynthesis. Quantification of chloroplast pigment content could supply the important information about the correlation between plants and environment. The variation of chloroplast pigments between different age leaves and the change patterns of different age leaf chloroplast pigments along elevation gradients were analyzed. The results showed that there were significant or very significant differences of chlorophyll a, chlorophyll b, and chlorophyll(a+b) between different age leaves. Generally, the content of chlorophyll a, chlorophyll b, and chlorophyll (a+b) in two–year-old leaves was higher than in one-year-old leaves and the variations are more substantial at middle and high elevation gradients than at low elevation gradients. Yet the variation of chlorophyll a/b and carotenoid between different age leaves was complicated, and it indicated the adaptation of plants to environment. There were significant variations of the chlorophyll a, chlorophyll b, and chlorophyll (a+b) between different elevation gradients and some certain change patterns were presented. With the increase of elevation gradients, the chlorophyll a, chlorophyll b, and chlorophyll (a+b) content of seven dominant species among the dominant populations become higher, reaching a maximum at the elevation of A5 or A6 and then become lower. And the change patterns of chlorophyll a/b were more diversified with the increase of elevation gradients. As a type of functional pigment, the function of carotenoid was complicated, the response patterns to elevation were diversified too. The results of this research indicated that as an important environment factors elevation had vital and significant impacts on plants and that the dominant species had different adaptation strategies.The data analysis of leaf nutrient concentration showed generally wide concentration ranges for most mineral nutrients except P and Na. And most tree species were clustered at the lower or middle end of the concentration ranges indicating they have low nutrient status. Among the macronutrients, P and Na had the lowest and narrowest foliar concentration, with the range of 0.259～2.026 g·kg-1 for P, 0.150～1.804 g·kg-1 for Na. Concentration of Ca had widest range. The nutrient concentration of different age leaves was different. The concentration of N, P, K for one-year-old leaves was higher than two-year-old leaves and the concentration of Na, Ca, Fe, Mn, Zn was opposite. A few tree species were observed to accumulate (called''accumulator species'') some mineral nutrients like N, P, K, Na.The variation of leaf traits along altitude gradient showed that leaf traits of SLA,C, K, Mg content were lower with the increasing altitude and LDMC was higher. It indicated the adaptation strategies to habitat of the dominant species. The variation of SLA and LDMC demonstrated the adaptation to nutrient inadequate.The results of regression analysis showed that leaf traits except for leaf organic carbon content had significant linear relationship with the value of foliarδ¹³C. Theδ¹³C value of different age leaves was positively correlated with LDMC and the concentration of P, Ca, and negatively correlated with the concentration of N, K, Na, Mg, Ash and chlorophyll. The correlation ofδ¹³C value and the concentration of Fe, Mn, Zn were multiform at different altitude gradients. For the data all the altitude gradients, theδ¹³C value wasn't correlated with the concentration of Fe and Zn and positively correlated with the concentration of Mn of one-year-old leaves, negatively correlated with the concentration of Mn of two-year-old leaves. The results indicated that species, leaf age and environmental factors could influence the relationship ofδ¹³C and leaf traits.Results of PCA(Principal Component Analysis) for 13 leaf trait factors effecting foliarδ¹³C showed that the first five principal components composited 80 percent leaf traits and the eigenvalue of each primary component was greater than 1. Principal component regression analysis showed that the correlation ofδ¹³C and leaf traits was different for different age leaves. The strength sequence of relevance ofδ¹³C with leaf traits factors for one-year-old leaves was LDMC, Na, P, Ca, Mn, SLA, Fe, Ash, chlorophyll, Zn, K, Mg and N declining. And the strength sequence for two-year-old leaves was Ca, SLA, N, P, chlorophyll, LDMC, K, Mg, Mn, Zn, Fe, Ash.This showed that the role of factors playing on plant growth was in dynamic change. SLA, LDMC, concentration of P and Ca played important roles on plant growth. Compared with two-year-old leaves, concentration of Fe, Mn and Ash played more important roles on two-year-old leaves. And concentration of chlorophyll was vital forδ¹³C value of two-year-old leaves.The Pearson correlation was analyzed between foliarδ¹³C and environmental factors such as soil nutrient status at different depth, elevation and slope was studied. Soil nutrient status at each depth could influence value of foliarδ¹³C.The correlation between foliarδ¹³C and soil nutrient content was mainly on positive. We could conclude that soil nutrients can reduce the isotope discrimination of plant leaves and improve water use efficiency of plants. Topographical factors could influence value of foliarδ¹³C too.Portable chlorophyll meter SPAD-502 was used to measure the greenness (SPAD) of different age leaves of dominant species at different altitude gradients. There was different variation of SPAD value between the different age leaves, different dominant species and different altitude gradients. And the correlation between SPAD value and chlorophyll and foliar N concentration showed that significant correlations between SPAD value and concentration of chlorophyll and foliar N were observed,indicating that SPAD value could not only well reflect the chlorophyll concentration measured by spectrophotometry method, but also a useful tool for nondestructively assessing foliar N status. In the case of comparison in a relative value instead of real magnitude, SPAD value could be indicators for foliar chlorophyll and nitrogen, which may have efficient application for forest assessments in decision-making and operational nutrient management programs.Variance analysis showed that there was significant variation between dominant species for leaf traits such as SLA, LDMC, the concentration of C, N, P, K, Ca, Mg, Fe, Mn, Zn and the ratio of C/N, C/P, N/P. And there was significant variation between different age leaves for SLA,LDMC the concentration of P, K, Ca, Fe, Zn and C/P. The correlation between SLA, LDMC and leaf nutrient content were analyzed. SLA was positively correlated with concentration of N, P, K, Na, Mg, Zn, Ash for different age leaves and positively correlated with concentration of Ca, Fe, Mn and ratio of N/P for two-year-age leaves. And it was negatively correlated with LDMC, Ca, C/N and C/P. There was significant regression relation between leaf nutrient concentrations and nutrient structures too. We can conclude that the leaf traits were the representation of adaptation to environment long-term. Redundancy analysis (RDA) of environmental variables and foliar nutrient concentration showed that foliar mineral nutrient concentration of the trees was generally correlated with the environmental factors. However, the effects were interrelated and difficult to isolate from each other. The influence of environmental factors on different dominant species and was different. The strategy of resources use was different for dominant species, which was benefit to coexistence of species long-term.