Treesearch

Clouds and cloud shadows are common features of visible and infrared remotelysensed images collected from many parts of the world, particularly in humid and tropical regions. We have developed a simple and semiautomated method to mask clouds and shadows in Landsat ETM+ imagery, and have developed a recent cloud-free composite of multitemporal images for Puerto Rico and its adjacent islands that can be used for a variety of landscape analyses. Our assumption is that if clouds and shadows can be identified in a reference image, they can be replaced with data from other dates. We created...

This report documents the type and source of geospatial data available for Haiti. It was compiled to serve as a resource for geographic information system (GIS)-based land management and planning. It will be useful for conservation planning, reforestation efforts, and agricultural extension projects. Our study indicates that there is a great deal of geospatial information available for Haiti, both digitally georeferenced and hardcopy. The sources of geospatial information range from historical maps to recent satellite imagery and thematic maps. The types of information are described and...

The processes that control the formation, intensity and track of hurricanes are poorly understood1. It has been proposed that an increase in sea surface temperatures caused by anthropogenic climate change has led to an increase in the frequency of intense tropical cyclones2,3, but this proposal has been challenged on the basis that the instrumental record is too short and unreliable to reveal trends in intense tropical cyclone activity4. Storm-induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and hurricane...

Tropical forests are suffering from increasing intensities and frequency of disturbances. As a result, non-native species accidentally introduced or intentionally planted for farming, plantations, and ornamental purposes may spread and potentially invade undisturbed native forest. It is not known if these introduced species will become invasive, as a result of recurrent natural disturbances such as hurricanes. Using data from three censuses (spanning 15 years) of a 16-ha subtropical wet forest plot, we investigated the impact of two hurricanes on populations of plant species that were...

Decaying wood is an important structural and functional component of forests: it contributes to generate habitat diversity, acts as either sink or source of nutrients, and plays a preponderant role in soil formation. Thus, decaying wood might likely have measurable effects on chemical properties of the underlying soil.We hypothesized that decaying wood would have a stronger effect on soil as decomposition advances and that such effect would vary according to wood quality. Twenty logs from two species with contrasting wood properties (Dacryodes excelsa Vahl. and Swietenia macrophylla King)...

This study quantifies the amount of water withdrawn from the Luqillo Experimental Forest (LEF) in 2004. Spatially averaged mean monthly water budgets were generated for watersheds draining the LEF by combining long-term data from various government agencies with estimated extraction data. Results suggest that, on a typical day, 70 percent of water generated within the forest is diverted before reaching the ocean. This is up from an estimated 54 percent in 1994. Analysis showed that up to 63 percent of average monthly stream runoff is diverted from individual watersheds during drier months....

The island of Puerto Rico has both a high population density and a long history of ineffective land use planning. This study integrates geospatial technology and population census data to understand how people use and develop the lands. We define three new regions for Puerto Rico: Urban (16%), Densely Populated Rural (36%), and Sparsely Populated Rural (48%). Eleven percent of the island is composed of urban/built-up surfaces. A large part of these developments occur in both low-density patterns of construction and sparsely populated neighborhoods. Half of the urban development occurs...

Necromass is an important stock of carbon in tropical forests. We estimated volume, density, and mass of fallen and standing necromass in undisturbed and selectively logged forests at Juruena, Mato Grosso, Brazil (10.488S, 58.478W). We also measured standing dead trees at the Tapajos National Forest, Para, Brazil (3.088S, 54.948W) complementing our earlier study there on fallen necromass.We compared forest that was selectively logged using reduced-impact logging methods and undisturbed forest.We estimated necromass density accounting for void volume for necromass greater than 10 cm...

Selective logging is an extensive land-use practice in South America. Governments in the region have enacted policies to promote the establishment and maintenance of economically productive and sustainable forest industries.However, both biological and policy constraints threaten to limit the viability of the industry over the long term.Biological constraints, such as slow tree growth rates, can be overcome somewhat by management practices. In order to improve the likelihood of success for sustainable management, it is important to accept that forests change over time and that managed...

The northern karst of Puerto Rico is a unique formation that contains one of the island’s largest remaining forested tracts. The region is under ever-increasing human pressure, but large portions of it are being considered for conservation. Forest classification of the region is at a coarse scale, such that it is considered one vegetation type. We asked whether there were distinct tree assemblages which would necessitate targeted conservation strategies to ensure their protection. We examined tree species and communities across the region at three different major topographic positions...