New space-based approaches to studying disturbance-recovery trends in wetlandscapes

以湿地为主的景观--或称“湿地景观”--以各种相互联系、高度动态的湿地网络为特征。它们提供与水资源、生物多样性和碳循环相关的重要生态系统服务。由于气候和人为(土地利用)变化，这些景观中的许多都面临着严重的威胁。湿地的复原力--它们在不断变化的制度下继续提供生态系统服务的能力--是一个关键问题，需要了解生态和水文动力学。然而，在湿地景观中，这些动态往往很难量化，因为它们具有高度的时间变异性和空间异质性。虽然卫星对地观测数据在湿地景观研究中发挥着越来越重要的作用，但大多数卫星传感器要么缺乏空间分辨率，要么缺乏时间观测频率，无法充分捕捉其时空动态。然而，开放卫星数据和高性能计算能力的趋势正在改变研究景观动态的方式。特别是，在土地覆盖监测领域出现了“虚拟星座”的概念，作为解决空间和时间分辨率问题的潜在办法。风险控制系统涉及整合来自多个卫星传感器的数据，以满足单一的监测目标。发展这一概念的一个特别挑战是融合来自不同传感器的数据。中分辨率光学和合成孔径雷达(SAR)传感器通常用于监测湿地水文和植被，但如何整合这两种传感器的信息，以生成对洪水、连通性或植被趋势等动态陆面参数的空间和时间上一致的估计，这是一个关键的研究空白。我的研究项目基于VCS和光学-SAR融合的概念，以解决湿地景观对气候和土地利用变化的适应能力问题。因此，该计划致力于解决三个研究目标：(1)通过开发新的光学-合成孔径雷达合成方法来量化湿地景观中流域尺度的淹没动态；(2)利用高分辨率图像时间序列和图论度量方法研究湿地连通性的时空趋势；以及(3)发展对泥炭为主的湿地景观中对火灾干扰的水文和生态响应的理解。研究地点将从代表气候和生态系统梯度的北极、北方、温带和亚热带湿地景观中选择。将来自Landsat和Sentinel-1等历史和当代光学传感器的数据与来自Sentinel-1任务和RADARSAT星座任务(RCM)的SAR数据相结合的新方法将是实现这三个目标的基础。预期的NASA-ISRO长波长SAR任务的数据也将在可用时纳入其中。

Wetland-dominated landscapes - or "wetlandscapes" - are characterized by networks of variably connected, highly dynamic wetlands. They provide vital ecosystem services related to water resources, biodiversity and carbon cycling. Many of these landscapes are facing serious threats due to climate-mediated and anthropogenic (land use) changes. Wetlandscape resilience - their ability to continue providing ecosystem services in the presence of shifting change regimes - is a critical question requiring an understanding of ecological and hydrological dynamics. However, these dynamics are often difficult to quantify in wetlandscapes because of their high temporal variability and spatial heterogeneity. While satellite Earth observation data have been playing an increasingly important role in the study of wetlandscapes, most satellite sensors lack either the spatial resolution or temporal observation frequency to adequately capture their spatio-temporal dynamics. However, trends in open satellite data and high-performance computing capabilities are transforming the way in which landscape dynamics are studied. In particular, the concept of "Virtual Constellations" (VCs) has emerged in the field of land cover monitoring as a potential solution to the problem of spatial and temporal resolution. VCs involve the integration of data from multiple satellite sensors to address a single monitoring objective. A particular challenge in the development this concept is the fusion of data from disparate sensors. Moderate resolution optical and Synthetic Aperture Radar (SAR) sensors are commonly used to monitor wetland hydrology and vegetation, but how to integrate information from both types of sensors to generate spatially and temporally consistent estimates of dynamic land surface parameters like inundation, connectivity or vegetation trends represents a key research gap. My research program develops upon the concept of VCs and optical-SAR fusion to address the problem of resilience of wetlandscapes to climate and land use changes. Accordingly, this program seeks to address three research objectives: (1) Quantify basin-scale inundation dynamics in wetlandscapes through the development of novel optical-SAR compositing approaches; (2) Study spatio-temporal trends of wetland connectivity with fine resolution image time series and graph theory metrics; and (3) Develop an understanding of the hydrological and ecological responses to fire disturbances in peat-dominated wetlandscapes. Study sites will be selected from Arctic, boreal, temperate and sub-tropical wetlandscapes, representing a climate and ecosystem gradient. New methods that integrate data from historical and contemporary optical sensors like Landsat and Sentinel-1 with SAR data from the Sentinel-1 mission and the RADARSAT Constellation Mission (RCM) will be foundational to all three objectives. Data from the anticipated long-wavelength NASA-ISRO SAR mission will also be incorporated as they become available.