Doctoral Dissertation Research: Linking Land-Use and Land-Cover Change and Aquatic Ecosystem Function in the Temash River Watershed, Belize, Central America

轮作耕作是中美洲低地玛雅森林的主要土地利用策略。这种做法包括刀耕火种，然后种植玉米。接下来，允许田地休耕，然后重新清理和种植。轮作耕作已被确定为热带森林砍伐的一个原因，另一方面，它也是一种很好地适应热带景观的可持续农业战略。本项目结合自然地理学、水生生态学和稳定同位素生物地球化学等方法，评估了伯利兹南部Temash河流域轮作耕作对生态系统结构和功能的影响。土地利用/土地覆盖变化的遥感分析将评估流域土地利用的空间分布以及轮作耕作对土地覆盖的影响。对森林地区、活跃玉米地和休耕地的土壤调查将检验与土壤有机质（SOM）来源和周转有关的假设，以及森林覆盖变化对SOM库内碳动态的影响。河流颗粒有机物质将被用于跟踪森林到米尔帕转化的影响，关于有机物质跨越陆地-水生边界的转移。最后，全年将测量该流域未受干扰和已清除的河岸区域的溪流中的营养物质（氮和磷）浓度。这种比较将提供对这些流动水域的季节性营养动态的见解，以及人类是否通过土地利用变化改变了水生营养动态。这项研究将探讨农业转移如何影响热带水生生态系统。它还将研究土地利用变化如何影响热带低地溪流和河流中的碳、氮和磷动态。特玛什河位于萨斯顿-特玛什国家公园，目前由流域内的居民共同管理。本研究将为国家公园水生生态系统管理规划的制定提供基础性文件。它还将向居民通报他们的土地利用做法对Temash河流域水生生态系统结构和功能的影响。

Shifting cultivation is the principle land use strategy in the Maya Forest of lowland Central America. This practice includes slash-and-burn forest clearance, followed by corn (milpa) cultivation. Next, fields are allowed to fallow before they are re-cleared and planted again. Shifting cultivation has been identified as a cause of tropical deforestation and, alternatively, as a sustainable agricultural strategy that is well adapted to tropical landscapes. This project combines methods from physical geography, aquatic ecology, and stable isotope biogeochemistry to evaluate the impact of shifting cultivation on ecosystem structure and function in the Temash River watershed, southern Belize. Remote sensing analysis of land use/land cover change will assess the spatial distribution of land uses in the watershed and the impact of shifting cultivation on land cover. A soil survey of forested areas, active cornfields, and fallow fields will examine hypotheses related to soil organic matter (SOM) sources and turnover, and the impact of changing forest cover on carbon dynamics within the SOM pool. Riverine particulate organic matter will be used to track the effect of forest-to-milpa conversion, with respect to organic matter transfer across the terrestrial-aquatic boundary. Finally, nutrient (nitrogen and phosphorus) concentrations will be measured in streams of undisturbed and cleared riparian regions of the watershed throughout the year. This comparison will provide insights into seasonal nutrient dynamics in these running waters, and whether humans alter aquatic nutrient dynamics through land use change. This research will address how shifting agriculture impacts tropical aquatic ecosystems. It will also examine how land use changes affect carbon, nitrogen, and phosphorus dynamics in streams and rivers of the lowland tropics. The Temash River is located in the Sarstoon-Temash National Park, which is currently co-managed by inhabitants within the watershed. This research will provide a founding document for development of an aquatic ecosystem management plan for the national park. It will also inform residents about the impact of their land use practices on aquatic ecosystem structure and function with the Temash River watershed.