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禾本科植物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，这些变异在理论上被很好地理解，但在生态学上却没有很好地表征。这些标签以定量可预测的方式传递到更高的营养水平，并以一种鲜为人知的方式传递到土壤有机质（SOM）。研究由C4和C3系统组成的草原，建立组成、比例生产力、生物量δ 13C、生化组成和SOM δ 13C之间的定量关系。粒度组分和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演替状态。许多草原之间的比较可能表明，在最近的过去和过去的1000年里，在组成上存在任何一致的方向性变化。将比较短草和高草系统中的细粒和粗粒土壤，并确定植物岩是否可以用来区分短草和高草成分。将记录植物和隔间中自然发生的δ 13C值的范围，并将其与生长形式和环境因素联系起来。对已知土地利用历史的草原和旧田的研究将使我们能够估计颗粒大小、组分和土壤团聚体的周转率。本文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.