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沿着莫哈韦沙漠东部的一条现代气候剖面,实验测定了土壤环境的稳定碳同位素组成与现代气候和植被的关系。即使所有海拔上的植物组合都具有类似的同位素组成,土壤CO_2和土壤碳酸盐的δ~(13)C值也要随着海拔的增高和植物密度的加大而降低。一些因素(包括成土方解石与石灰岩方解石之比率的差异、过去植被的差异)被认为可以解释这一趋势。然而,在植物稀少的莫哈韦沙漠,成土碳酸盐的δ~(13)C值受植物密度和生物活动的差异的控制。这一关系可能为评价过去的植物密度(只要这些植物的同位素组成是均一的)提供了一种方法。
Along a modern climate profile in the eastern Mojave Desert, the relationship between stable carbon isotope composition of the soil environment and modern climate and vegetation was experimentally determined. Even though all plant assemblages at the same altitude have similar isotopic compositions, the δ 13 C values of soil CO 2 and soil carbonates also decrease with increasing altitude and plant density. Some factors, including differences in the ratios of calcitic to calcitic limestones and differences in past vegetation, are believed to explain this trend. However, δ 13 C values of the carbonate in the Mojave desert with few plants are controlled by differences in plant density and biological activity. This relationship may provide a way to evaluate past plant density (as long as the isotopic composition of these plants is uniform).