Differentiation Patterns Of Leaf Traits Of Main Trees Along Altitudinal And Micro-topographical Gradients On Tianmushan Mountain

Leaves are the main organs for plants to perform photosynthesis. The properties and characteristics of leaves have close relationships with the growth strategy and the capacity of utilizing resources in plants, which will reflect different adaptive strategies of plants to varying environments. For mountainous plants, different altitudes and micro-topographiy will exert influence on leaf traits through light, temperature, soil moisture and nutrient. Therefore the causes of leaf traits'differentiation patterns were studied in this study after comparison of the pattern under different altitudes and micro-topography in Tianmushan Mountain, which will reveal the response mechanism of plants to the environments. The main conclusions are as follows:(1) Photosynthetically active radiation (PAR) increased as the lifting of altitude. Therefore it is a popular choice for broad-leaved species to reduce SLA in order to raise their LDMC and lower LPC and LNC as a conservative growth strategy to adapt hard light and hypothermal environment, especially in deciduous trees and shrubs.(2) The five micro-topographical gradients can be divided into two groups:one as humid river bed and river valley (valley floor and lower side slopes), the other as poor dry crest slop, side slope and head hollow (upper side slope). SLA, LNC and LPC were higher in the former group whereas relatively lower in the latter group. It may be conjectured that the limiting factor for the growth of plants can be the poor nutrients (especially the loss of phosphorus) of upper side slopes, which therefore caused the application of conservative growth strategy; however, the richer soil nutrients in valley floor and lower side slopes together with the complication environment increased the randomness of survival and growth of plants, producing more competence between species, hence the more utilization of resources.(3) The distributions of species of each life-form were affected by altitude and micro-topographical gradients. Hypothermy went against the growth of evergreen species; the distribution of evergreen and deciduous species has a preference of side slope while the quantity of evergreen species in valley floor was little and deciduous species in valley floor was much. The evergreen species were probably have a stronger tolerant of barren than deciduous species. The conifer species survived in hypothermal and barren habitat.(4) There were significant variations of specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen concentration (LNC) and leaf phosphorus concentration (LPC) in plants of different life-forms. SLA, LNC and LPC in deciduous broad-leaved species were significantly higher than evergreen broad-leaved species; no significant variations of leaf traits existed between trees and shrubs whereas LDMC of deciduous broad-leaved shrubs was significantly lower than species of other life-forms; SLA in coniferous trees was far lower than broad-leaved species but no obvious variations in other leaf traits indices; N/P in species of different life-forms had no significant differences with all values above 16, which meant the limitation of leaf phosphorus.(5) Leaf trait indices were significant correlated with each other. SLA was negatively correlated with LDMC and N/P but positively with LNC and LPC; LDMC was negatively correlated with LNC and LPC; LNC was positively correlated with LPC; N/P was positively correlated with LPC but had no significant correlation with LNC. In evergreen broad-leaved trees, N/P was significantly correlated with LNC and LPC.