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Multiscale remote sensing analysis to monitor riparian and upland semiarid vegetation.

机译：多尺度遥感分析，以监测河岸和高地半干旱植被。

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摘要

The health of natural vegetation communities is of concern due to observed changes in the climatic-hydrological regime and land cover changes particularly in arid and semiarid regions. Monitoring vegetation at multi temporal and spatial scales can be the most informative approach for detecting change and inferring causal agents of change and remediation strategies. Riparian communities are tightly linked to annual stream hydrology, ground water elevations and sediment transport. These processes are subject to varying magnitudes of disturbance overtime and are candidates for multi-scale monitoring.;My first research objective focused on the response of vegetation in the Upper San Pedro River, Arizona, to reduced base flows and climate change. I addressed the correlation between riparian vegetation and hydro-climate variables during the last three decades in one of the remaining undammed rivers in the southwestern U.S. Its riparian forest is threatened by the diminishing base flows, attributed by different studies either to increases in evapotranspiration (ET) due to conversion of grasslands to mesquite shrublands in the adjacent uplands, or to increased regional groundwater pumping to serve growing populations in surrounding urban areas and or to some interactions of those causes. Landsat 5 imagery was acquired for pre- monsoon period, when riparian trees had leafed out but before the arrival of summer monsoon rains in July. The result has showed Normalized Difference Vegetation Index (NDVI) values from both Landsat and Moderate Resolution Imaging Spectrometer (MODIS) had significant decreases which positively correlated to river flows, which decreased over the study period, and negatively correlated with air temperatures, which have increased by about 1.4°C from 1904 to the present. The predictions from other studies that decreased river flows could negatively impact the riparian forest were supported by this study. The pre-monsoon Normalized Different Vegetation Index (NDVI) average values in the adjacent uplands also decreased over thirty years and were correlated with the previous year's annual precipitation. Hence an increase in ET in the uplands did not appear to be responsible for the decrease in river flows in this study, leaving increased regional groundwater pumping as a feasible alternative explanation for decreased flows and deterioration of the riparian forest.;The second research objective was to develop a new method of classification using very high-resolution aerial photo to map riparian vegetation at the species level in the Colorado River Ecosystem, Grand Canyon area, Arizona. Ground surveys have showed an obvious trend in which non-native saltcedar (Tamarix spp.) has replaced native vegetation over time. Our goal was to develop a quantitative mapping procedure to detect changes in vegetation as the ecosystem continues to respond to hydrological and climate changes. Vegetation mapping for the Colorado River Ecosystem needed an updated database map of the area covered by riparian vegetation and an indicator of species composition in the river corridor. The objective of this research was to generate a new riparian vegetation map at species level using a supervised image classification technique for the purpose of patch and landscape change detection. A new classification approach using multispectral images allowed us to successfully identify and map riparian species coverage the over whole Colorado River Ecosystem, Grand Canyon area. The new map was an improvement over the initial 2002 map since it reduced fragmentation from mixed riparian vegetation areas. The most dominant tree species in the study areas is saltcedar (Tamarix spp.). The overall accuracy is 93.48% and the kappa coefficient is 0.88. The reference initial inventory map was created using 2002 images to compare and detect changes through 2009.;The third objective of my research focused on using multiplatform of remote sensing and ground calibration to estimate the effects of vegetation, land use patterns and water cycles. Climate change, hydrological and human uses are also leading to riparian, upland, grassland and crop vegetation changes at a variety of temporal and spatial scales, particularly in the arid and semi arid ecosystems, which are more sensitive to changes in water availability than humid ecosystems. The objectives of these studies from the last three articles were to evaluate the effect of water balance on vegetation indices in different plant communities based on relevant spatial and temporal scales. The new methodology of estimating water requirements using remote sensing data and ground calibration with flux tower data has been successfully tested at a variety sites, a sparse desert shrub environment as well as mixed riparian and cropland systems and upland vegetation in the arid and semi-arid regions. The main finding form these studies is that vegetation-index methods have to be calibrated with ground data for each new ecosystem but once calibrated they can accurately scale ET over wide areas and long time spans.
机译：由于观察到的气候水文状况和土地覆盖的变化，特别是在干旱和半干旱地区，自然植被群落的健康令人担忧。在多个时空尺度上监测植被可能是检测变化并推断变化和补救策略的因果关系的最有用的方法。河岸社区与年度河流水文学，地下水高程和沉积物运输紧密相关。这些过程会随着时间的推移受到不同程度的扰动，并且可能成为多尺度监测的候选者。我的第一个研究目标集中在亚利桑那州上圣佩德罗河上的植被对减少基流和气候变化的响应。我讨论了过去三十年中美国西南部其余未受污染的河流之一的河岸植被和水文气候变量之间的相关性。河岸森林受到基础流量不断减少的威胁，不同研究将其归因于蒸散量（ET）的增加）是由于将草地转变为邻近高地的豆科灌木丛土地，或者是由于增加了区域地下水抽水服务于周围城市地区不断增长的人口，以及这些原因的相互作用。在季风前期采集了Landsat 5影像，当时河岸树木已经落叶，但在7月夏季季风降雨来临之前。结果表明，Landsat和中分辨率成像光谱仪（MODIS）的归一化植被指数（NDVI）值均显着下降，与河流流量呈正相关，在研究期间呈下降趋势，而与气温呈负相关，呈上升趋势从1904年到现在大约1.4°C其他研究的预测表明，河流流量减少可能对河岸带森林产生负面影响。邻近山地的季风前标准化不同植被指数（NDVI）平均值在30年中也有所下降，并且与上一年的年降水量相关。因此，在本研究中，高地ET的增加似乎与河流流量的减少无关，因此增加了区域地下水泵送作为河岸森林流量减少和退化的可行替代解释。；第二个研究目标是开发一种新的分类方法，该方法使用超高分辨率的航空照片在亚利桑那州大峡谷地区科罗拉多河生态系统中的物种水平上绘制河岸植被的地图。地面调查显示了一个明显的趋势，即随着时间的推移，非本地盐杉（Tamarix spp。）取代了本地植被。我们的目标是开发一种定量测绘程序，以检测生态系统继续响应水文和气候变化时植被的变化。科罗拉多河生态系统的植被测绘需要更新的河岸植被覆盖的数据库地图以及河流走廊中物种组成的指标。这项研究的目的是使用监督图像分类技术在斑块和景观变化检测的目的下，在物种水平上生成新的河岸植被图。一种使用多光谱图像的新分类方法，使我们能够成功识别并绘制大峡谷地区整个科罗拉多河生态系统中的河岸物种覆盖率。新地图比2002年的原始地图有所改进，因为它减少了来自混合河岸植被区域的碎片。在研究区域中，最主要的树种是Saltcedar（Tamarix spp。）。总体精度为93.48％，卡伯系数为0.88。参考初始清单图是使用2002年的图像创建的，以比较和检测2009年之前的变化。我的研究的第三个目标是使用遥感和地面校准的多平台来估算植被，土地利用方式和水循环的影响。气候变化，水文和人类利用还导致河床，高地，草地和农作物植被在各种时空尺度上变化，特别是在干旱和半干旱生态系统中，与湿润生态系统相比，干旱和半干旱生态系统对水利用量的变化更为敏感。 。最近三篇文章的这些研究的目的是基于相关的时空尺度，评估水平衡对不同植物群落中植被指数的影响。使用遥感数据和通量塔数据进行地面校准来估算需水量的新方法已在各种地点成功进行了测试干旱和半干旱地区稀疏的灌木丛环境以及河岸和农田混合系统以及高地植被。这些研究的主要发现是，必须针对每个新生态系统的地面数据对植被指数方法进行校准，但是一旦进行校准，它们就可以在大面积和长时间范围内准确地扩展ET。

著录项

  • 作者

    Nguyen, Uyen.;

  • 作者单位

    The University of Arizona.;

  • 授予单位 The University of Arizona.;
  • 学科 Environmental science.;Ecology.;Remote sensing.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 296 p.
  • 总页数 296
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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