本文選題：有機碳同位素 + 表土　； 參考：《中國地質大學(北京)》2017年博士論文

【摘要】：土壤有機碳同位素與地表植被組成密切相關,受控于環(huán)境要素。通過研究表土有機碳同位素組成和現(xiàn)代植被群落、氣候之間的關系可以為古氣候研究提供理論基礎,同時為定量重建古氣候和估算高原隆升幅度提供參考資料。本項目在青藏高原東緣海拔588-4846m采集表土測試有機碳同位素,并將其與青藏高原東緣現(xiàn)代植被群落組成、氣象要素資料進行綜合研究,以探討不同海拔高度表土有機碳同位素變化規(guī)律并分析其控制性因素。通過研究發(fā)現(xiàn),青藏高原東緣表土有機碳同位素組成總體隨著海拔的上升呈先下降而后上升的變化趨勢:碳同位素值在2000m以下不穩(wěn)定并隨海拔上升而下降,在2000m以上隨海拔升高逐漸穩(wěn)定上升,在3000-3500m再次不穩(wěn)定并隨海拔的上升呈下降趨勢,3500m以上隨海拔升高而穩(wěn)定上升。表土有機碳同位素組成在不同植被地帶內有差異,按照常綠落葉闊葉混交林(平均-27.28‰)—常綠闊葉林(平均-27.25‰)—亞高山灌叢草甸(平均-25.85‰)—亞高山針葉林(平均-25.81‰)—高山灌叢草甸(平均-25.16‰)—干旱河谷植被(平均-24.07‰)的順序,表土有機碳同位素變重。常綠落葉闊葉混交林、高山灌叢草甸地帶內的表土有機碳同位素值隨海拔上升而上升,常綠闊葉林、亞高山針葉林、亞高山灌叢草甸地帶內的表土有機碳同位素值隨海拔上升呈先下降而后上升的趨勢,干旱河谷灌叢地帶內表土有機碳同位素組成與海拔高度沒有相關關系,但在同一河谷區(qū)內隨海拔升高呈下降趨勢。不同海拔高度、不同植被地帶下土壤有機碳同位素變化的差異主要是由C3、C4、CAM植物比例變化和C3植物生理調整引起的。C4、CAM植物比例的下降是導致碳同位素下降的主要原因。當C3、C4、CAM植物比例穩(wěn)定時,C3植物生理調整的控制作用才能顯現(xiàn)出來,導致碳同位素的上升。氣溫、降水對C4、CAM植物的分布具有決定性的作用,此外,光照也發(fā)揮了重要作用,但其作用海拔范圍有限。氣溫對C3植物生理調整的控制作用是明確的,而降水和氣壓的控制作用相對較小。在缺乏適宜的氣溫、降水環(huán)境下,僅靠氣壓變化無法導致土壤有機碳同位素的強烈變化。本文通過與前人研究成果結合建立了青藏高原周緣地區(qū)表土有機碳同位素與海拔之間的回歸方程,以期為后人在青藏高原地區(qū)開展古氣候古環(huán)境研究提供參考。
[Abstract]:Soil organic carbon isotopes are closely related to the composition of surface vegetation and are controlled by environmental factors. By studying the organic carbon isotopic composition of topsoil and modern vegetation communities, the relationship between climate can provide a theoretical basis for paleoclimate research, and provide reference for quantitative reconstruction of paleoclimate and estimation of uplift range of plateau. Organic carbon isotopes were collected and tested at 588-4846m above sea level in the eastern margin of Qinghai-Xizang Plateau, and combined with modern vegetation community composition and meteorological data of the eastern margin of Qinghai-Xizang Plateau. The variation of organic carbon isotopes in topsoil at different elevations was discussed and its controlling factors were analyzed. It is found that the total organic carbon isotopic composition of the surface soil in the eastern margin of the Qinghai-Xizang Plateau decreases first and then increases with the increase of altitude: the carbon isotope value is unstable below 2000m and decreases with the rise of altitude. When the altitude is above 2000m, it will rise steadily with the increase of altitude, and will be unstable again at 3000-3500m and will decrease with the rise of altitude, and will rise steadily with the increase of altitude. The organic carbon isotopic compositions of topsoil are different in different vegetation zones. According to the evergreen deciduous broad-leaved mixed forest (mean -27.28 鈥，

本文編號：1783886