ROA/RUI: Use of Stable Isotopes of Carbon in Vegetation and Soil Organic Matter to Assess Vegetation Change in North American Prairies

北美草原C3和C4牧草产生的有机质具有明显的同位素特征。这些标签显示了基于遗传和环境的变异，这种变异在理论上得到了很好的理解，但在生态学上没有得到很好的描述。这些标签以定量可预测的方式传递到更高的营养水平，并以一种较少被理解的方式传递到土壤有机质(SOM)。将对由C4和C3系统组成的草原进行研究，以建立组成、比例生产力、生物量三角洲13C、生化组成和土壤有机质三角洲13C之间的定量关系。对土壤颗粒级配和土壤团聚体的分析将表明土壤有机质和植被是处于稳定状态还是处于演替状态。许多大草原之间的比较可能表明，在最近的过去和过去的1000年里，成分存在着任何一致的方向变化。我们将对矮秆和高粱系统中的细粒和粗粒土进行比较，并确定是否可以使用植硅体来区分短草和高粱的成分。植物和隔间中自然产生的三角洲13C值的范围将被记录下来，并与生长形式和环境因素有关。对已知土地利用历史的草原和老田的研究将有助于估计颗粒级配和土壤团聚体的周转率。将对几个晚更新世和全新世古土壤进行分析。

Organic matter produced by C3 and C4 grasses in North American prairies possesses distinct isotopic signatures. These labels show genetically and environmentally based variation which is fairly well understood theoretically but not characterized well ecologically. The labels are transmitted in a quantitatively predictable manner to higher trophic levels and, in a less understood manner, to soil organic matter (SOM). Prairies comprising C4 and C3 systems will be studied to establish quantitative relationships among composition, proportional productivity, biomass delta 13C, biochemical composition, and SOM delta 13C. Analysis of particle size fractions and soil aggregates will indicate whether SOM and vegetation are in a steady state or successional. Comparisons among many prairies may show the presence of any consistent directional change in composition during the recent past and last 1,000 years. Fine and course grained soils in shortgrass and tallgrass systems will be compared and it will be determined whether or not phytoliths can be used to distinguish between shortgrass and tallgrass components. The range of naturally occurring delta 13C values in plants and compartments will be documented and related to growth forms and environmental factors. Studies of prairies and old fields with known land use histories will allow an estimation of rates of turnover of particle size fractions and soil aggregates. An analysis of several late Pleistocene and Holocene paleosols will be undertaken.