Treesearch

Various complementary techniques were used to investigate the stormflow generating processes in a small headwater catchment in northeastern Puerto Rico. Over 100 samples were taken of soil matrix water, macropore flow, streamflow and precipitation, mainly during two storms of contrasting magnitude, for the analysis of calcium, magnesium, silicon, potassium, sodium and chloride. These were combined with hydrometric information on streamflow, return flow, precipitation, throughfall and soil moisture to distinguish water following different flow paths. Geo-electric sounding was used to survey...

Egg color, size, and shape vary considerably within and among female Pearly-eyed Thrashers (Margarops fuscatus). Results of a 25-yr study (1979-2004) are presented to provide comparative data. In a sample of 4,128 eggs, typical shape was prolate spheroid; but several variations were observed, depending on the age, stature, and physiological condition of the female, as well as environmental influences such as the availability of essential nutrients. From a subset of 3,867 eggs measured between 1979 and 2000, a speciesspecific egg shape, or elongation index of 1.44 was derived (mean = 1.44;...

To evaluate the current status of instream flow practices in streams that drain into the Caribbean Basin, a voluntary survey of practising water resource managers was conducted. Responses were received from 70% of the potential continental countries, 100% of the islands in the Greater Antilles, and 56% of all the Caribbean island nations. Respondents identified ‘effluent discharges’, ‘downstream water quality’ and ‘existing extraction permits’ to be the most common sources of instream flow conflicts. In 75% of the countries, some type of ‘formal procedures’ exist for reviewing permit...

Hurricanes are important disturbance events in many forested ecosystems. They can have strong effects on both forest structure and animal populations, and yet few studies have considered the impacts on plant–animal interactions. Reduction of canopy cover by severe winds increases light availability to understory plants, providing an opportunity for increased growth. An increase in light availability should cause an increase in annual production of leaves and a more even production throughout the year (i.e., less seasonality in production). This change will affect the availability of food...

Invasive alien tree species in Puerto Rico often form monospecific stands on deforested lands that were previously used for agriculture and then abandoned. Most native pioneer species are incapable of colonizing these sites, and thus introduced species have little competition from native trees. Alien trees may dominate sites for 30 to 40 years, but by that time native species begin to appear in the understory. By 60 to 80 years, unique communities comprising both alien and native species are found on these sites. This phenomenon is a response to a change in the disturbance regime of Puerto...

How does the forest operate, develop its patterns, retain information in its memory sites, and transmit the great message to the future? (Odum, 1970a, p. x) The rain forest achieves complexity, high metabolism, and stability over geological time periods without surges and waste. Can we find in this example the clues for designing our own equally effective systems of man and nature? (Odum, 1970b, p. A5)werp

Restoring species-rich tropical forests is an important activity because it helps mitigate land deforestation and degradation. However, scientific understanding of the ecological processes responsible for forest restoration is poor. We review the literature to synthesize the current state of understanding of tropical forest restoration from a biogeochemical point of view. Aboveground biomass and soil carbon accumulation of restored tropical forests are a function of age, climate, and past land use. Restored forests in wet life zones accumulate more biomass than those in moist or dry life...

Coarse woody debris (CWD) is an important component of the carbon cycle in tropical forests. We measured the volume and density of fallen CWD at two sites, Cauaxi and Tapajós in the Eastern Amazon. At both sites we studied undisturbed forests (UFs) and logged forests 1 year after harvest. Conventional logging (CL) and reduced impact logging (RIL) were used for management on areas where the geometric volumes of logs harvested was about 25–30m3 ha-1. Density for five classes of fallen CWD for large material (410 cm diameter) ranged from 0.71 to 0.28Mg m-3 depending upon the degree of...

In the Caribbean island of Puerto Rico, rapid land-use changes over the past century have included recent landcover conversion to urban/built-up lands. Observations of this land development adjacent to reserves or replacing dense forest call into question how the changes relate to forests or reserved lands. Using existing maps, this study first summarizes island-wide land-cover change between 1977-78 and 1991-92. Then, using binomial logit modeling, it seeks evidence that simple forest cover attributes, reserve locations, or existing land cover influence land development locations....

Aim Describe the spatial and temporal properties of transitions in the Arctic and develop a conceptual understanding of the nature of these spatial transitions in the face of directional environmental change. Location Arctic tundra ecosystems of the North Slope of Alaska and the tundraforest region of the Seward Peninsula, Alaska. Methods We synthesize information from numerous studies on tundra and treeline ecosystems in an effort to document the spatial changes that occur across four arctic transitions. These transitions are: (i) the transition between High-Arctic and Low-Arctic systems,...