Innovative technologies for terrestrial remote sensing

[In lieu of abstract, extract from first page] Characterizing and monitoring terrestrial, or land, surface features, such as forests, deserts, and cities, are fundamental and continuing goals of Earth Observation (EO). EO imagery and related technologies are essential for increasing our scientific understanding of environmental processes, such as carbon capture and albedo change, and to manage and safeguard environmental resources, such as tropical forests, particularly over large areas or the entire globe. This measurement or observation of some property of the land surface is central to a wide range of scientific investigations and industrial operations, involving individuals and organizations from many different backgrounds and disciplines. However, the process of observing the land provides a unifying theme for these investigations, and in practice there is much consistency in the instruments used for observation and the techniques used to map and model the environmental phenomena of interest. There is therefore great potential benefit in exchanging technological knowledge and experience among the many and diverse members of the terrestrial EO community

Relationship between leaf physiologic traits and canopy color indices during the leaf expansion period in an oak forest

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecosphere 6, no. 12 (2015): 1-9, doi:10.1890/ES14-00452.1.Plant phenology has a significant impact on the forest ecosystem carbon balance. Detecting plant phenology by capturing the time-series canopy images through digital camera has become popular in recent years. However, the relationship between color indices derived from camera images and plant physiological characters are elusive during the growing season in temperate ecosystems. We collected continuous images of forest canopy, leaf size, leaf area index (LAI) and leaf chlorophyll measured by a soil plant analysis development (SPAD) analyzer in a northern subtropical oak forest in China. Our results show that (1) the spring peak of color indices, Gcc (Green Chromatic Coordinates) and ExG (Excess Green), was 18 days earlier than the 90% maximum SPAD value; (2) the 90% maximum SPAD value coincided with the change point of Gcc and ExG immediately after their spring peak; and (3) the spring curves of Gcc and ExG before their peaks were highly synchronous with the expansion of leaf size and the development of LAI value. We suggest it needs to be adjusted if camera-derived Gcc or ExG is used as a proxy of chlorophyll or gross primary productivity, and images observation should be complemented with field phenological and physiological information to interpret the physiological meaning of leaf seasonality.This research was funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions in the Discipline of Environmental Science and Engineering at Nanjing Forest University, Changjiang River Delta Urban Forest Ecosystem Research of CFERN (to H. Hu) and Brown University Seed Funds for International Research Projects on the Environment (to J. Tang)

Using phenocams to monitor our changing earth: Toward a global phenocam network

Rapid changes to the biosphere are altering ecological processes worldwide. Developing informed policies for mitigating the impacts of environmental change requires an exponential increase in the quantity, diversity, and resolution of field-collected data, which, in turn, necessitates greater reliance on innovative technologies to monitor ecological processes across local to global scales. Automated digital time-lapse cameras – “phenocams” – can monitor vegetation status and environmental changes over long periods of time. Phenocams are ideal for documenting changes in phenology, snow cover, fire frequency, and other disturbance events. However, effective monitoring of global environmental change with phenocams requires adoption of data standards. New continental-scale ecological research networks, such as the US National Ecological Observatory Network (NEON) and the European Union's Integrated Carbon Observation System (ICOS), can serve as templates for developing rigorous data standards and extending the utility of phenocam data through standardized ground-truthing. Open-source tools for analysis, visualization, and collaboration will make phenocam data more widely usable

DEVELOPMENT OF METHODOLOGY FOR PLANT PHENOLOGY MONITORING BY GROUND-BASED OBSERVATION USING DIGITAL CAMERA

When monitoring phenology at ground level, it would be more important to continue observations in long terms and to detect the timing of various phenological events such as leafing, flowering and autumn senescence. In this study, to develop the methodology for plant phenology monitoring by using digital camera, we examined how multiple image indices, which are derived from multi-temporal visible images, respond to the changes of colors of leaves and flowers for several target species of plants, and tried to detect various phenology events by tracing time series changes of the coordinate in the feature spaces of two indices. As a result, we found out that it was possible to understand the characteristics of the phenological events for different species from each image index. Also, it was identified that the utility of combination with two indices would be effective to detect the timing of phenology events in the feature space of two indices. In the actual phenology monitoring, it would be effective to use a single index for understanding the seasonal characteristics and to use the combination of two indices for detection of the timing of phenology events by tracing the time series changes in the feature space

A System for Acquisition, Processing and Visualization of Image Time Series from Multiple Camera Networks

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Seasonal patterns of forest canopy and their relevance for the global carbon cycle

In the terrestrial biosphere forests have a significant role as a carbon sink. Under recent climate change, it is increasingly important to detect seasonal change or ‘phenology’ that can influence the global carbon cycle. Monitoring canopies using camera systems has offered an inexpensive means to quantify the phenological changes. However, the reliability is not well known. In order to examine the usefulness of cameras to observe forest phenology, we analysed canopy images taken in two deciduous forests in Japan and England and investigate which colour index is best for tracking forest phenology and predict carbon uptake by trees. A camera test using model leaves under controlled conditions has also carried out to examine sensitivity of colour indices for discriminating leaf colours. The main findings of the present study are: 1) Time courses of colour indices derived from images taken in deciduous forests showed typical patterns throughout the growing season. Although cameras are not calibrated instrument, analysis of images allowed detecting the timings of phenological events such as leaf onset and leaf fall; 2) The strength of the green channel (or chromatic coordinate of green) was useful to observe leaf expansion as well as damage by spring late frost. However, the results of the camera test using model leaves suggested that this index was not sufficiently sensitive to detect leaf senescence. Amongst colour indices, Hue was the most robust metric for different cameras, different atmospheric conditions and different distances. The test also revealed Hue was useful to track nitrogen status of leaves; 3) Modelling results using a light use efficiency model for GPP showed a strong relationship between GPP and Hue, which was stronger than the relationships using alternative traditional indices

Anoles & Drones: revealing controls on anole abundance and mapping sub-canopy thermal habitat using remote sensing, on the island of Utila, Honduras

In these times of rapid environmental change and species extinction, understanding the drivers and mechanisms governing species’ abundance is more important than ever. The goal of this thesis was to further our understanding of what drives variation in species’ abundance and microhabitat use through space, particularly in the context of rapid land cover and climate change, using the little explored anole fauna of the Honduran island of Utila. The work uncovered that when considering structural habitat, prey availability and the thermal environment, for the endemic Anolis bicaorum, thermal habitat quality and prey biomass both had positive direct effects on anole abundance. However, thermal habitat quality also influenced prey biomass, leading to a strong indirect effect on abundance. Consequently, the later part of this thesis focuses on the thermal environment and the use of unoccupied aerial vehicles (UAVs) and satellite remote sensing platforms for mapping thermal habitat quality and availability at scales relevant to the species. Thermal habitat quality for A. bicaorum was primarily a function of canopy density, measured as leaf area index (LAI), therefore this work combined indices of canopy cover and heterogeneity derived from UAV and WorldView-2 satellite imagery to map sub canopy operative temperature (Te). Results indicate that such methods as using remote sensing imagery, when coupled with air temperature measures, are a reasonable way of mapping Te continuously across space, allowing us to quantify the availability and spatial structure of the thermal environment, at spatial scales experienced by the organism. Lastly, I used WorldView-2 imagery and the proposed methods for mapping Te to quantify available thermal habitat for A. bicaorum on Utila across land cover and climate scenarios. This work indicates the need to determine controls and niche interactions on animal abundance and the importance quantifying these niche factors at relevant spatial scales to estimate species responses to land cover and climatic change

Anoles & Drones: revealing controls on anole abundance and mapping sub-canopy thermal habitat using remote sensing, on the island of Utila, Honduras

In these times of rapid environmental change and species extinction, understanding the drivers and mechanisms governing species’ abundance is more important than ever. The goal of this thesis was to further our understanding of what drives variation in species’ abundance and microhabitat use through space, particularly in the context of rapid land cover and climate change, using the little explored anole fauna of the Honduran island of Utila. The work uncovered that when considering structural habitat, prey availability and the thermal environment, for the endemic Anolis bicaorum, thermal habitat quality and prey biomass both had positive direct effects on anole abundance. However, thermal habitat quality also influenced prey biomass, leading to a strong indirect effect on abundance. Consequently, the later part of this thesis focuses on the thermal environment and the use of unoccupied aerial vehicles (UAVs) and satellite remote sensing platforms for mapping thermal habitat quality and availability at scales relevant to the species. Thermal habitat quality for A. bicaorum was primarily a function of canopy density, measured as leaf area index (LAI), therefore this work combined indices of canopy cover and heterogeneity derived from UAV and WorldView-2 satellite imagery to map sub canopy operative temperature (Te). Results indicate that such methods as using remote sensing imagery, when coupled with air temperature measures, are a reasonable way of mapping Te continuously across space, allowing us to quantify the availability and spatial structure of the thermal environment, at spatial scales experienced by the organism. Lastly, I used WorldView-2 imagery and the proposed methods for mapping Te to quantify available thermal habitat for A. bicaorum on Utila across land cover and climate scenarios. This work indicates the need to determine controls and niche interactions on animal abundance and the importance quantifying these niche factors at relevant spatial scales to estimate species responses to land cover and climatic change