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The Study On The Response Of Foliar δ13 C Of Different Life Form Plants To Altitude In Subalpine Area Of Western Sichuan, China

Posted on:2012-04-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q H FengFull Text:PDF
GTID:1110330338473559Subject:Ecology
Abstract/Summary:PDF Full Text Request
Ever since 1960s, 13C from plant tissues has been found to be lower than that from atmosphere. So far, leaf discrimination to carbon isotope has become a common understanding. The researches over the last 20 years find that most of foliarδ13C from C3 plant increase with increasing altitude. However, most of researches were on single species, but were not systematic researches on different life forms. Understanding the altitudinal response of foliarδ13C from different life forms not only could explain the foliarδ13C changes along altitudinal gradients but also elucidate the underlying mechanisms of the response and adaptation of plant eco-physiological processes to a changing environment, and the divergence of above all among different life forms. This study will help to improve understanding and assessing of global climate change implication on terrestrial ecosystem in terms of ecosystem response, feedback and adaption to climate change.Plant discrimination to 13C is influenced by environmental and biological factors, but leaf discrimination to 13C mainly depends on its photosynthetic eco-physiological processes. Responses of foliarδ13C to altitudinal gradients for different life form plants in a same area were analyzed and compared in this paper. Their possible underlying mechanisms from eco-physiological point of view were also explored. Five plant species, including tree species Quercus aquifolioides and Quercus spinosa, shrub species Salix dissa and Salix atopantha, and forb species Rumex dentatus were chosen in Wolong reserve at different altitudes, i.e., Quercus species at the three altitude levels of 2600m, 3050m and 3500m, and Salix species and Rumex dentatus at the four altitude levels of 2350m, 2700m, 3150m and 3530m, respectively. The foliarδ13C and other leaf traits including photosynthesis, diffusion, nutrient and morphology were measured in growing seasons in 2009 and 2010. All the trait data were analyzed by the methods of One-way ANOVA, Pearson correlation analysis and Standardised Major Axis analysis.Regardless of life form, plant foliarδ13C increased with increasing altitude. The order them. However, there were significant differences in foliarδ13C values among different life form plants, with the order sequence of tree>shrub>forb. There were some different responses of leaf traits including photosynthesis, diffusion, nutrient content and morphology to altitude change among different life form plants. Photosynthetic traits and diffusional conductance (stomatal conductance (gs) and mesophyll conductance (gm)) of tree species decreased with increasing altitude, but on the contrary, that of shrub and forb species increased. Leaf nitrogen content per area (Narea) increased with increasing altitude more steadily than that of leaf nitrogen content per mass (Nmass). Photosynthetic nitrogen use efficiency (PNUE) and specific leaf area (SLA) decreased with altitude for all species except S. atopantha, but decrease in SLA of tree species with altitude was not statistically significant. Dark respiration rate (Rd) of all species increased with altitude.There were some differences in relationships between different foliar eco-physiological traits among different life form plants, and even among different species. There were no significant differences in promotion effect of diffusional conductance on net photosynthetic rate (A) among different life forms, but the effect of diffusional conductance on foliarδ13C varied with different life form plants. Foliarδ13C of tree species decreased but that of shrub and forb species except S. dissa increased with increasing diffusional conductance. SLA affected foliarδ13C by gm indirectly, but this is not the only way for SLA to affect foliarδ13C by gm. Narea is a main factor influencing the maximum rate of photosynthesis (Amax) for shrub and forb species, while PNUE, instead, for tree species. Although the similar effects of Narea and PNUE on foliarδ13C among different plant life form except S. atopantha, their specific underlying mechanisms are different. Generally, diffusional conductance and capacity of carboxylation are the two major biological factors influencing the response ofδ13C to changing altitude. However, for evergreen tree species, the diffusional conductance had larger effect onδ13C than the capacity of carboxylation, and for shrub and herbs, the capacity of carboxylation had larger effect onδ13C than the diffusional conductance.With inceasing altitude the Narea and foliar thickness (decreased SLA, except S. atopantha) for all species tend to increase, but there are differences in foliar nitrogen allocation between photosynthetic system and non-photosynthetic system. Evergreen Quercus tree species tend to allocate more nitrogen into structural protein for non-photosynthetic system, such as cell wall, in order to maintain physiological resistance to severe environment. For plant species with longer leaf life-span, maintaining leaf integrity for ensuring long term photosynthetic production is more important than increasing photosynthetic capacity. However, deciduous shrub and forb species tend to allocate more nitrogen to photosynthetic system for higher photosynthetic capacity in order to accumulate more photosynthate for maintaining their metabolism in shorter leaf lifespan. Therefore, the balance between leaf life-span and photosynthetic capacity, or the balance of foliar nitrogen allocation between photosynthetic system and non-photosynthetic system is the main reason accounting for adaptation differences of different life form species to altitudinal gradient. In addition, a long-term water use efficiency (WUE) increases with increasing altitude, which is beneficial to facilitating adaptatibility of plant species to environments stressed with low water availability.
Keywords/Search Tags:foliar carbon isotope discrimination, altitudinal gradient, photosynthesis, life form, sub-alpine plant, western Sichuan
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