species diversity

Land Use History, Environment, and Tree Composition in a Tropical Forest

Thompson, Jill; Brokaw, Nicholas; Zimmerman, Jess K.; Waide, Robert B.; Everham, Edwin M. III; Lodge, D. Jean; Taylor, Charlotte M.; Garcia-Montiel, Diana; Fluet, Marcheterre 2002. Land use history, environment, and tree composition in a tropical forest. Ecological applications. Vol. 12, no. 5 (2002): pages 1344-1363.

Abstract: 
The effects of historical land use on tropical forest must be examined to understand present forest characteristics and to plan conservation strategies. We compared the effects of past land use, topography, soil type, and other environmental variables on tree species composition in a subtropical wet forest in the Luquillo Mountains, Puerto Rico. The study involved stems > 10 cm diameter measured at 130 cm above the ground, within the 16-ha Luquillo Forest Dynamics Plot (LFDP), and represents the forest at the time Hurricane Hugo struck in 1989. Topography in the plot is rugged, and soils are variable. Historical documents and local residents described past land uses such as clear-felling and selective logging followed by farming, fruit and coffee production, and timber stand improvement in the forest area that now includes the LFDP. These uses ceased 40-60 yr before the study, but their impacts could be differentiated by percent canopy cover seen in aerial photographs from 1936. Using these photographs, we defined four historic cover classes within the LFDP. These ranged from cover class 1, the least tree-covered area in 1936, to cover class 4, with the least intensive historic land use (selective logging and timber stand improvement). In 1989, cover class 1 had the lowest stem density and proportion of large stems, whereas cover class 4 had the highest basal area, species richness, and number of rare and endemic species. Ordination of tree species composition (89 species, 13 167 stems) produced arrays that primarily corresponded to the four cover classes (i.e., historic land uses). The ordination arrays corresponded secondarily to soil characteristics and topography. Natural disturbances (hurricanes, landslides, and local treefalls) affected tree composition, but these effects did not correlate with the major patterns of species distributions on the plot. Thus, it appears that forest development and natural disturbance have not masked the effects of historical land use in this tropical forest, and that past land use was the major influence on the patterns of tree composition in the plot in 1989. The least disturbed stand harbors more rare and endemic species, and such stands should be protected.

Separating the effects of forest type and elevation on the diversity of litter invertebrate communities in a humid tropical forest in Puerto Rico

RICHARDSON, BARBARA A.; RICHARDSON, MICHAEL J.; SOTO-ADAMES, FELIPE N. 2005. Separating the effects of forest type and elevation on the diversity of litter invertebrate communities in a humid tropical forest in Puerto Rico.. Journal of Animal Ecology 74, :926-936.

Abstract: 
1. The primary effects of climatic conditions on invertebrate litter communities, and the secondary effects of different forest types, were distinguished by using the sierra palm as a control in a natural experiment along an elevational gradient in the Luquillo Mountains. These mountains have three well-defined forest types along the gradient, with the palm occurring as stands within each forest. 2. Palm litter samples were richer in nutrients, particularly phosphorus, than nonpalm litter, significantly so at higher elevations where leaching would have been expected. In nonpalm litter, mineral concentrations were significantly lower at higher elevations. 3. Animal abundance mirrored the pattern of mineral amounts and declined significantly in mid- and high-altitude forests, but did not decline with increasing elevation in palm stands. A pulse of post-hurricane litterfall was reflected in the high abundance of Coleoptera and Isoptera the following year. 4. The species richness of communities (Margalef’s index) declined with increasing elevation in nonpalm forest litter, but was remarkably similar in palm litter at all elevations. 5. Palm litter communities were more similar to each other (Sørensen’s index) than nonpalm communities, which became less similar with increasing elevation. 6. The differences observed from the lower slopes to the summits, in animal abundance, species richness and the uniformity of communities, are better explained by the contribution of forest composition to the chemical and physical nature of litter and forest heterogeneity, rather than to direct effects of temperature and rainfall differences.

phytogeographical trends, centers of high species richness and endemism and the question of extinction in the native flora of puerto rico

Figueroa Colón, J. C. 1996. Phytogeographical trends, centers of high species richness and endemism, and the question of extinctions in the native flora of Puerto Rico. . The scientific survey of Puerto Rico and the Virgin Islands: an eighty year assessment of the island's natural history. Annals of the New York Academy of Sciences. New York: The Academy; pp. 89-102.

Relationship between aboveground biomass and multiple measures of biodiversity in subtropical forest of Puerto Rico

Vance-Chalcraft, Heather D.; Willig, Michael R.; Cox, Stephen B.; Lugo, Ariel E.; Scatena, Frederick N. 2010. Relationship between aboveground biomass and multiple measures of biodiversity in subtropical forest of Puerto Rico. Biotropica. 42(3):290-299.

Abstract: 
Anthropogenic activities have accelerated the rate of global loss of biodiversity, making it more important than ever to understand the structure of biodiversity hotspots. One current focus is the relationship between species richness and aboveground biomass (AGB) in a variety of ecosystems. Nonetheless, species diversity, evenness, rarity, or dominance represent other critical attributes of biodiversity and may have associations with AGB that are markedly different than that of species richness. Using data from large trees in four environmentally similar sites in the Luquillo Experimental Forest of Puerto Rico, we determined the shape and strength of relationships between each of five measures of biodiversity (i.e., species richness, Simpson’s diversity, Simpson’s evenness, rarity, and dominance) and AGB. We quantified these measures of biodiversity using either proportional biomass or proportional abundance as weighting factors. Three of the four sites had a unimodal relationship between species richness and AGB, with only the most mature site evincing a positive, linear relationship. The differences between the mature site and the other sites, as well as the differences between our richness–AGB relationships and those found at other forest sites, highlight the crucial role that prior land use and severe storms have on this forest community. Although the shape and strength of relationships differed greatly among measures of biodiversity and among sites, the strongest relationships within each site were always those involving richness or evenness.

Relationship Between Aboveground Biomass and Multiple Measures of Biodiversity in Subtropical Forest of Puerto Rico

Vance-Chalcraft, Heather D.; Willig, Michael R.; Cox, Stephen B.; Lugo, Ariel E.; Scatena, Frederick N. 2010. Relationship between aboveground biomass and multiple measures of biodiversity in subtropical forest of Puerto Rico. Biotropica. 42(3):290-299.

Abstract: 
Anthropogenic activities have accelerated the rate of global loss of biodiversity, making it more important than ever to understand the structure of biodiversity hotspots. One current focus is the relationship between species richness and aboveground biomass (AGB) in a variety of ecosystems. Nonetheless, species diversity, evenness, rarity, or dominance represent other critical attributes of biodiversity and may have associations with AGB that are markedly different than that of species richness. Using data from large trees in four environmentally similar sites in the Luquillo Experimental Forest of Puerto Rico, we determined the shape and strength of relationships between each of five measures of biodiversity (i.e., species richness, Simpson’s diversity, Simpson’s evenness, rarity, and dominance) and AGB. We quantified these measures of biodiversity using either proportional biomass or proportional abundance as weighting factors. Three of the four sites had a unimodal relationship between species richness and AGB, with only the most mature site evincing a positive, linear relationship. The differences between the mature site and the other sites, as well as the differences between our richness–AGB relationships and those found at other forest sites, highlight the crucial role that prior land use and severe storms have on this forest community. Although the shape and strength of relationships differed greatly among measures of biodiversity and among sites, the strongest relationships within each site were always those involving richness or evenness.

Effects of nutrient availability and other elevational changes on bromeliad populations and their invertebrate communities in a humid tropical forest in Puerto Rico

RICHARDSON, BARBARA A.; RICHARDSON,M. J.; SCATENA, F. N.; MCDOWELL, W. H. 2000. Effects of nutrient availability and other elevational changes on romeliad populations and their invertebrate communities in a humid tropical forest in Puerto Rico. Journal of Tropical Ecology 16:167±188.

Abstract: 
Nutrient inputs into tank bromeliads were studied in relation to growth and productivity, and the abundance, diversity and biomass of their animal inhabitants, in three forest types along an elevational gradient. Concentrations of phosphorus, potassium and calcium in canopy-derived debris, and nitrogen and phosphorus in phytotelm water, declined with increasing elevation. Dwarf forest bromeliads contained the smallest amounts of debris/plant and lowest concentrations of nutrients in plant tissue. Their leaf turnover rate and productivity were highest and, because of high plant density, they comprised 12.8% of forest net primary productivity (0.47 t ha-1 y-1), and contained 3.3 t ha-1 of water. Annual nutrient budgets indicated that these microcosms were nutrient-abundant and accumulated < 5% of most nutrients passing through them. Exceptions were K and P in the dwarf forest, where accumulation was c. 25% of inputs. Animal and bromeliad biomass/plant peaked in the intermediate elevation forest, and were positively correlated with the debris content/bromeliad across all forest types. Animal species richness showed a signi®cant mid-elevational peak, whereas abundance was independent of species richness and debris quantities, and declined with elevation as forest net primary productivity declined. The unimodal pattern of species richness was not correlated with nutrient concentrations, and relationships among faunal abundance, species richness, nutrient inputs and environment are too complex to warrant simple generalizations about nutrient resources and diversity, even in apparently simple microhabitats.
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