Quantifying mortality of tropical rain forest trees using high‐spatial‐resolution satellite data

Abstract

Assessment of forest responses to climate change is severely hampered by the limited information on tree death on short temporal and broad spatial scales, particularly in tropical forests. We used 1‐m resolution panchromatic IKONOS and 0.7‐m resolution QuickBird satellite data, acquired in 2000 and 2002, respectively, to evaluate tree death rates at the La Selva Biological Station in old‐growth Tropical Wet Forest in Costa Rica, Central America. Using a calibration factor derived from ground inspection of tree deaths predicted from the images, we calculated a landscape‐scale annual exponential death rate of 2.8%. This corresponds closely to data for all canopy‐level trees in 18 forest inventory plots, each of 0.5 ha, for a mostly‐overlapping 2‐year period (2.8% per year). This study shows that high‐spatial‐resolution satellite data can now be used to measure old‐growth tropical rain forest tree death rates, suggesting many new avenues for tropical forest ecology and global change research.

Object-Based Image Analysis of Downed Logs in Disturbed Forested Landscapes Using Lidar

“…Moderate spatial resolution (5-30 m) imagery from Landsat, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and Système Pour l'Observation de la Terre (SPOT) sensors have been used to map forest pattern and large-scale disturbance [14,15]. Fine spatial resolution imagery (<5 m) from digital aerial orthophotographs, IKONOS, QuickBird, and Worldview-2 sensors are commonly used to map vegetation abundance and productivity [16,17], monitor disturbances and change [18][19][20][21], and assist in forest management [22]. These passive image sources offer advantages over traditional field based approaches in their repeatability, lower acquisition cost, and greater spatial extent, but they are limited by their top-of-canopy perspective which reduces the ability to observe objects below the canopy [17,[23][24][25].…”

“…The importance in forest science of the ability to extract individual objects in the forest is increasingly noted. Precise mapping of individual trees or shrubs in a forest aids in understanding forest biometeorology [37], tree demography [20], community structure [54], carbon storage [23,55], pathogen spread [56,57], and habitat use [47,53]. The need for object-based precision in mapping can in some cases be facilitated by a field of image segmentation and classification procedures commonly called object-based image analysis (OBIA).…”

Qualitative distinction of congeneric and introgressive mangrove species in mixed patchy forest assemblages using high spatial resolution remotely sensed imagery (IKONOS)

“…In other words, a too detailed image results in tree canopies of a single species being represented by heterogeneous image pixels (upper side, lower side, sun-side, shade-side), and the delineation of an entire assemblage or the classification of an entire image may be easier for images that are more coarse (comparable to the original spatial resolution of the multispectral bands). Apart from image classification of large areas in the light of mapping or monitoring, the detailed features visible from panchromatic or pansharpened imagery also provide ecological information, such as mortality of individual trees (Clark et al, 2004) or the introgression reported above.…”

“…However, the information from very high spatial resolution remote sensing is not necessarily extracted using computer-aided interpretation. Even with IKONOS or QUICKBIRD imagery of submeter resolution, visual analysis is not outdated, and may prove most appropriate for specific ecological research and management purposes (Read et al, 2003;Clark et al, 2004). Although the combination between pixel-based (spectral) and object-based (texture) analysis indicates a high potential for future identification techniques, the ecological reality (physiognomy, distance to certain ecological resources or physico-chemical environmental conditions) assessed through visual interpretation, remains invaluable in the interpretation of remotely sensed imagery.…”

Replacing coal with wood: sustainable, eco-neutral, conservation harvest of natural tree-fall in old-growth forests

“…The most ecologically benign approach, uses satellite location of new canopy gaps (Clark et al 2003), and aerial transfer of logs to yards beside roads or rivers, using lighter-than-air ships (e.g., see Boeing SkyHook 2008) or helicopters. This permits removing the harvest by the use of only very widely-spaced logging-roads or, instead, rivers.…”