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首页> 外文学位 >Soil accumulation in a Chesapeake Bay salt marsh: Modeling 500 years of global change, vegetation change, and rising atmospheric carbon dioxide.
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Soil accumulation in a Chesapeake Bay salt marsh: Modeling 500 years of global change, vegetation change, and rising atmospheric carbon dioxide.

机译：切萨皮克湾盐沼中的土壤蓄积：模拟500年的全球变化，植被变化和大气中二氧化碳的增加。

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Wetlands store over 20% of terrestrial carbon; therefore, changes in carbon cycling in wetlands may represent an important potential feedback on rising CO2 and resulting greenhouse warming. The goal of my dissertation is to understand how global changes and vegetation changes alter the accumulation of soil organic matter (SOM) in a Chesapeake Bay salt marsh. I quantified several key linkages between global changes (i.e., CO2, temperature, sea-level, and salinity), species composition, plant production, and decomposition of SOM to develop five ecosystem models which simulate soil profiles and elevation change on a century time scale. I tested these models with data collected within and adjacent to an ongoing CO2 enrichment study in a Chesapeake Bay salt marsh.; The most complex of the five models (Full model) assumed that C 3 and C4 species differ with respect to plant production, litter chemistry, and belowground structure. The simplest model (Null model) assumed these characteristics were the same for the two species. The Null model reproduces the general data set more accurately than the other models, whereas the F-S model, in which rooting profiles are assumed identical for both species, performs best at reproducing profiles of specific organic chemistry fractions. Although none of the models accurately reproduce the observed values of elevation change, the models which include species-specific root profiles (i.e., the Full and F-C models) correlate the strongest with observed values (r2 = 0.78 and 0.72) compared to the other models (r 2 0.19). The Full and F-C model may be useful for examining potential feedbacks between C4 abundance and elevation change, mediated by species differences in root profiles.; When I incorporated observed effects of CO2 on key ecosystem functions in the Full and F-S models, I found that CO2-mediated changes in microbial activity best predict CO2 effects on soil profiles. Predictions of the Full model also correlate with the observed effect of CO2 on elevation change more strongly (r2 = 0.78) than the other models (r2 0.03). In general, models predict that the effects of CO2 on SOM and elevation change are likely to be subtle, depending on initial soil chemistry and vegetation type.
机译：湿地储存了超过20％的陆地碳；因此，湿地碳循环的变化可能代表着CO 2 升高和温室效应的重要潜在反馈。本文的目的是了解切萨皮克湾盐沼的全球变化和植被变化如何改变土壤有机质（SOM）的积累。我量化了全球变化（例如，CO 2 ，温度，海平面和盐度），物种组成，植物生产以及SOM分解之间的几个关键联系，以开发出五种模拟土壤剖面的生态系统模型和海拔高度在一个世纪的时间尺度上变化。我用切萨皮克湾盐沼中正在进行的CO 2 浓缩研究的内部和附近的数据对这些模型进行了测试。这五个模型中最复杂的一个（完整模型）假设C 3 和C 4 物种在植物生产，凋落物化学和地下结构方面存在差异。最简单的模型（空模型）假设两个物种的这些特征相同。 Null模型比其他模型能更准确地复制一般数据集，而F-S模型（假设两个物种的生根曲线均相同）在复制特定有机化学组分的曲线方面表现最佳。尽管没有一个模型能够准确地再现观测到的海拔变化值，但是包括物种特定根部轮廓的模型（即Full模型和FC模型）将最强值与观测值相关（r 2 = 0.78）和0.72）相比其他模型（r 2 <0.19）。 Full和F-C模型可能对于检查C 4 丰度与海拔变化之间的潜在反馈（由根谱中的物种差异介导）可能有用。当我在Full模型和FS模型中纳入观察到的CO 2 对关键生态系统功能的影响时，我发现CO 2 介导的微生物活性变化最能预测CO 2 对土壤剖面的影响。 Full模型的预测还与观察到的CO 2 对海拔变化的影响相关（r 2 = 0.78），比其他模型（r 2 < / super> <0.03）。通常，模型预测，CO 2 对SOM和海拔变化的影响可能很小，这取决于初始土壤化学性质和植被类型。

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