Quantitative Assessment of Soil Genesis Using a Controlled Decade-Scale Experiment

小行星9316378 由于缺乏对成土速率和趋势作为各种环境因素的函数的精确知识，限制了利用土壤进行详细的地貌和环境解释。 这项研究将通过分析一个独特的正在进行的实验开始=50年前在南加州的圣迪马斯实验森林量化十年尺度的土壤发生过程。 大（5.3米× 5.3米× 2.1米深）土墙坑填充均质化土壤材料和种植单种植物，构成一个强加的生物序列的四个本地植物物种（Chamise，ceanothus，灌木橡树，库尔特松）。 土壤形成的初始阶段的时序记录提供了存档的原始填充材料和土壤样品在1958年，1975年和1987年在每种植被下的增量深度每7.5厘米层的样品。 本研究的目的是量化的生物，大气和成壤的影响，作为时间的函数，每个土壤植被系统的初始均匀填充材料。 一个质量平衡的方法将被用来量化收益，损失，并在12年后，29年和41年的四种不同的植物物种下开发的土壤中的成分的再分布。 要分析的成分包括主要的成岩元素、粘土、粉砂、成土氧化铁、可交换阳离子、C、N和重金属。 计算将基于存档的原始母质样品，这些样品对应于随后几年开发和取样的土层。 将测量生物量和组成，并将其纳入质量平衡。 该地点存在大气湿降和干降的长期测量，也将包括在内。 放射性同位素将用于区分各种土壤成分的来源和分布。 土壤和树木年轮中独特的Sr、Nd和Pb同位素比值可作为指示元素大气和矿物风化来源的示踪剂。 质量平衡和放射性同位素示踪方法相结合，将产生一个详细的会计过程负责增加，损失，转移和转化的土壤植被系统。 精确的量化和解释是必要的，因为圣迪马斯土壤植被地块可能是最密切的限制和有据可查的土壤发生实验存在。 它们填补了多年实验研究与传统土壤时序研究之间的关键空白，传统土壤时序研究的时间尺度为102至106年。 这项研究的结果将产生一个更精确的了解土壤演变的初始阶段比目前存在的。 这方面的知识可以用来改善解释断层运动的历史，从土壤和预测源和汇的元素，包括重金属污染物和植物养分，在一个时间尺度上与人类引起的影响大气化学。

9316378 Graham The use of soils for detailed geomorphic and environmental interpretations is limited by lack of precise knowledge of pedogenic rates and trends as a function of various environmental factors. This research will quantify decade-scale soil genesis processes by analyzing a unique on-going experiment started =50 years ago at the San Dimas Experimental Forest in Southern California. Large (5.3m x 5.3m x 2.1m deep) earthen-walled pits were filled with homogenized soil material and planted with monocultures constituting an imposed biosequence of four native plant species (chamise, ceanothus, scrub oak, and Coulter pine). A chronosequential record of the initial stages of soil formation is provided by archived samples from each 7.5 cm layer of original fill material and soil samples taken at incremental depths in 1958, 1975, and 1987 under each type of vegetation. The objective of this research is to quantify the biotic, atmospheric, and pedogenic influences on the initial homogeneous fill material as a function of time for each of the soil-vegetation systems. A mass balance approach will be used to quantify gains, losses, and redistributions of constituents in the soils developed after 12, 29, and 41 years under the four different plant species. Constituents to be analyzed include major rock-forming elements, clay, silt, pedogenic Fe oxides, exchangeable cations, C, N, and heavy metals. Calculations will be based on the archived original parent material samples corresponding to soil horizons that developed and were sampled in subsequent years. Biomass quantity and composition will be measured and included in the mass balance. Long-term measurements of atmospheric wet- and dry-fall exist for the site and will also be included. Radiogenic isotopes will be used to distinguish the origin and disposition of various soil constituents. Distinctive Sr, Nd, and Pb isotopic rations in soils and tree rings will serve as tracers to indicate atmospheri c and mineral weathering sources of elements. The combination of mass balance and radiogenic isotope tracer methods will yield a detailed accounting of processes responsible for additions, losses, transfers, and transformations in the soil-vegetation systems. Precise quantification and interpretation is warranted because the San Dimas soil-vegetation plots are likely the most closely constrained and well documented soil genesis experiments in existence. They fill a critical gap between experimental studies that operate over several years and traditional soil chronosequence studies that address time scales of 102 to 106 years. Results of this research will yield a much more precise understanding of the initial stages of soil evolution than currently exists. This knowledge can be used to improve interpretations of fault movement histories from soils and to predict sources and sinks of elements, including heavy metal contaminants and plant nutrients, on a time scale commensurate with human-induced effects on atmospheric chemistry.