Collaborative Research: The Sustainability of Riparian Forests in Expanding Amazonian Agricultural Landscapes

合作研究：河岸森林在扩大亚马逊农业景观中的可持续性

• 批准号: 1660034
• 负责人: Christopher Neill
• 金额: $ 65.47万
• 依托单位: Woodwell Climate Research Center, Inc.
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2019-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1660034&HistoricalAwards=false
• 关键词: Collaborative; Research; Sustainability; Riparian; Forests

The conversion of large areas of Amazon forest vegetation for intensive crop production is one of the major forces shaping the Earth. Riparian forest buffers along streams can reduce the potential negative effects of forest clearing on stream water quality and stream habitat by intercepting nutrients, providing shade to reduce temperature and protecting stream channels. This project investigates how deforestation, cropland expansion and intensification, and increased fertilizer use influence the structure and sustainability of riparian forests, and ultimately affect their capacity to keep nutrient runoff from reaching streams. Research will take place in the Amazon state of Mato Grosso, Brazil's global hotspot of deforestation where soybean cultivation has expanded rapidly in the last two decades. Producers in the region are now shifting from single-cropped soybeans to double-cropped soybeans and corn, which greatly increases fertilizer inputs. This project addresses the globally important issue of how to protect and sustain water quality and aquatic resources in tropical regions, where high deforestation and rapid cropland expansion are increasingly common. By improving understanding of the trajectories and causes of riparian forest change and predicting the movement of nitrogen through riparian zones, these results will provide a basis for managing the negative impacts of tropical agricultural intensification. The project team will convey findings to policymakers and farmers in Brazil and the US by conducting two workshops on the scientific basis for riparian forest management and conservation. This project will investigate whether riparian forest fragments in cropland maintain their vegetation structure over time and how that structure is influenced by alterations to watershed hydrology and microclimate that are typical of cropland areas. Investigators will determine whether riparian forests bordering streams in croplands intercept and remove nitrogen from watersheds and whether this nitrogen removal function is sufficient to prevent excess nitrogen from reaching streams in cropland watersheds with high fertilizer inputs. The project will quantify how changes to riparian forest structure in croplands alter stream temperature, metabolism, nutrient uptake and downstream nutrient export. This will be accomplished by comparing riparian forests in replicated watersheds within intact tropical forest, soybean-only cropland and soybean-corn cropland. The project focuses on the following three hypotheses: (1) Riparian forests in cropland watersheds have higher tree mortality, lower tree growth and a more open canopy than either upland forests or riparian forests in forested watersheds. (2) Cropland watersheds have lower evapotranspiration, greater runoff and nutrient export, higher water tables, and wetter stream side slopes than forest watersheds but denitrification in riparian zones is insufficient to prevent excess nitrogen from reaching streams in double-cropped watersheds. (3) More open canopies in cropland riparian forest will increase stream temperature and metabolism. This project will create a new conceptual framework for understanding how deforestation, cropland expansion, and agricultural intensification influence tropical riparian forests and streams.

大面积亚马逊森林植被转变为集约化作物生产是塑造地球的主要力量之一。溪流沿岸的河岸森林缓冲区可以通过截留养分、提供遮荫来降低温度和保护溪流通道，从而减少森林砍伐对溪流水质和溪流栖息地的潜在负面影响。该项目调查森林砍伐、农田扩张和集约化以及化肥使用增加如何影响河岸森林的结构和可持续性，并最终影响其阻止养分径流到达溪流的能力。研究将在亚马逊马托格罗索州进行，这里是巴西全球森林砍伐的热点地区，过去二十年里大豆种植面积迅速扩大。该地区的生产者现在正从单季大豆转向双季大豆和玉米，这大大增加了化肥投入。该项目解决了如何保护和维持热带地区的水质和水生资源这一全球重要问题，在这些地区，森林砍伐严重和农田快速扩张日益普遍。通过加深对河岸森林变化轨迹和原因的了解，并预测氮在河岸区的移动，这些结果将为管理热带农业集约化的负面影响提供基础。该项目团队将通过举办两次关于河岸森林管理和保护科学基础的研讨会，向巴西和美国的政策制定者和农民传达研究结果。该项目将调查农田中的河岸森林碎片是否随着时间的推移保持其植被结构，以及农田地区典型的流域水文和小气候的变化如何影响该结构。调查人员将确定农田中与溪流接壤的河岸森林是否拦截并去除流域中的氮，以及这种氮去除功能是否足以防止过量的氮到达高化肥投入的农田流域中的溪流。该项目将量化农田河岸森林结构的变化如何改变河流温度、新陈代谢、养分吸收和下游养分输出。这将通过比较完整热带森林、大豆农田和大豆玉米农田内复制流域的河岸森林来实现。该项目侧重于以下三个假设：（1）农田流域中的河岸森林比森林流域中的高地森林或河岸森林具有更高的树木死亡率、更低的树木生长和更开放的树冠。 (2) 与森林流域相比，农田流域的蒸散量较低，径流和养分输出较多，地下水位较高，溪流边坡更湿润，但河岸区的反硝化不足以防止过量的氮进入双季作物流域的溪流。 (3)农田河岸林中更开放的树冠将提高溪流温度和新陈代谢。该项目将创建一个新的概念框架，以了解森林砍伐、农田扩张和农业集约化如何影响热带河岸森林和溪流。