LEF

Base saturation, nutrient cation, and organic matter increases during early pedogenesis on landslide scars in the Luquillo Experimental Forest, Puerto Rico

ZARIN, D. J. 1993. Nutrient accumulation during succession in subtropical lower montane wet forests, Puerto Rico.
Ph.D. dissertation. University of Pennsylvania, Philadelphia, Pennsylvania.
———, AND A. H. JOHNSON. 1995a. Nutrient accumulation during primary succession in a montane tropical forest,
Puerto Rico. Soil Sci. Soc. Am. J. 59: 1444–1452.
———, AND ———. 1995b. Base saturation, nutrient cation, and organic matter increases during early pedogenesis
on landslide scars in the Luquillo Experimental Forest, Puerto Rico. Geoderma 65: 317–330.

Abstract: 
We evaluate data from a chronosequence study of landslide scars, ranging in age from 1-55 + yr, in the Luquillo Experimental Forest (LEF) a subtropical lower montane wet forest (sensu Holdridge) in eastern Puerto Rico. Surface mineral soil (0-10 cm) base saturation index (BSI) values increase during primary succession in the LEF (R=0.85, P<0.001 ). Both BSI values and major nutrient cation concentrations are extremely low on new landslide scars. During the course of the 55 + yr chronosequence, major nutrient cation concentrations are positively correlated with soil organic matter (SOM) content (P = 0.079) and not with clay content (P = 0.794). When data collected from plots representing the two dominant late-succession vegetation associations are added to the analysis, nutrient cation concentrations correlate significantly with both SOM (P= 0.001) and clay content (P=0.033). Our data show that when initial conditions are oligotrophic, both nutrient cation pools and BSI values can increase in the surface mineral soil during early pedogenesis. We discuss exogenic litter input, substrate weathering, and precipitation as potential sources for nutrient cations in these soils. We further suggest that production and decomposition of SOM is the dominant process controlling capture, retention and intra-ecosystem cycling of nutrient cations in these forests.

Spatial dependence and the relationship of soil organic carbon and soil moisture in the luquillo experimental forest, puerto rico

Wang H, Hall CAS, Cornell JD, Hall MHP.
2002. Spatial dependence and the relationship
of soil organic carbon and soil moisture in Luquillo experimental forest. Landsc.
Ecol. 17:671–84

Abstract: 
We used geo-spatial statistical techniques to examine the spatial variation and relationship of soil organic carbon (SOC) and soil moisture (SM) in the Luquillo Experimental Forest (LEF), Puerto Rico, in order to test the hypothesis that mountainous terrain introduces spatial autocorrelation and crosscorrelation in ecosystem and soil properties. Soil samples (n = 100) were collected from the LEF in the summer of 1998 and analyzed for SOC, SM, and bulk density (BD). A global positioning system was used to georeference the location of each sampling site. At each site, elevation, slope and aspect were recorded. We calculated the isotropic and anisotropic semivariograms of soil and topographic properties, as well as the cross-variograms between SOC and SM, and between SOC and elevation. Then we used four models (random, linear, spherical and wave/hole) to test the semivariances of SOC, SM, BD, elevation, slope and aspect for spatial dependence. Our results indicate that all the studied properties except slope angle exhibit spatial dependence within the scale of sampling (200 – 1000 m sampling interval). The spatially structured variance (the variance due to the location of sampling sites) accounted for a large proportion of the sample variance for elevation (99%), BD (90%), SOC (68%), aspect (56%) and SM (44%). The ranges of spatial dependence (the distances within which parameters are spatially dependent) for aspect, SOC, elevation, SM, and BD were 9810 m, 3070 m, 1120 m, 930 m and 430 m, respectively. Cross correlograms indicate that SOC varies closely with elevation and SM depending on the distances between samples. The correlation can shift from positive to negative as the separation distance increases. Larger ranges of spatial dependence of SOC, aspect and elevation indicate that the distribution of SOC in the LEF is determined by a combination of biotic (e.g., litterfall) and abiotic factors (e.g., microclimate and topographic features) related to elevation and aspect. This demonstrates the importance of both elevation and topographic gradients in controlling climate, vegetation distribution and soil properties as well as the associated biogeochemical processes in the LEF.

Migration patterns, densities, and growth of Neritina snails in Rio Espiritu Santo and Rio Mameyes, northeastern Puerto Rico

PYRON, MARK; COVICH, ALAN P. 2003. Migration Patterns, Densities, and Growth of Neritina punctulata Snails in Rio Espiritu Santo and Rio Mameyes, Northeastern Puerto Rico.. Caribbean Journal of Science, Vol. 39, No. 3, 338-347, .

Abstract: 
Snail size-frequency distributions in Rios Espiritu Santo and Mameyes, which drain the Luquillo Experimental Forest, Puerto Rico, showed that Neritina punctulata with shell lengths greater than 30 mm were the most abundant size class at upstream sites. The highest densities for all size classes were at the downstream sites. Growth rates were 0.015 mm/day for a large cohort (¡«25 mm shell length) and 0.035 mm/day for a small (¡«15 mm shell length). Minimum longevity estimates range from 3 to 7 years. Size distribution data suggest that snails migrate upstream. An August mark-recapture study resulted in most snails remaining at the release site, and some moved downstream. The greatest upstream distance reached was 200 m in 12 weeks. In a May mark-recapture study, when snails were observed moving in aggregations, the greatest distance moved was 200 m in 27 days, suggesting seasonality in movements and reproduction. Movement rates of snails in aggregates in May were between 0.08 and 0.17 cm/s. All of the snails marked in May moved upstream, and none were observed downstream from, or at the release site. We suggest that upstream movements can be explained by snails avoiding increased predation in the downstream reaches of these rivers from fishes, crustaceans, and birds

Controls on major solutes within the drainage network of a rapidly 3 weathering tropical watershed

Bhatt, M. P., and W. H. McDowell (2007), Controls on major solutes within the drainage network of a rapidly weathering
27 tropical watershed, Water Resour. Res., 43, XXXXXX, doi:10.1029/2007WR005915.

Abstract: 
Surface water chemistry in the main stem and source points of the Rio Icacos basin 7 (Luquillo Experimental Forest, Puerto Rico) was studied to investigate the factors 8 regulating spatial variability in major solutes in a rapidly weathering landscape. We 9 sampled along the main stem as well as at small source points at high elevation where 10 fresh bedrock is frequently exposed, and at low elevation in the floodplain/colluvial 11 plain of the main stem. Concentrations of silicon, alkalinity, and the sum of base 12 cations were lower at the source points than in the main stem, and were lowest in low- 13 elevation source points. Calcium and sodium were the dominant cations at all sampling 14 points after sea-salt correction, reflecting the weathering of plagioclase feldspar 15 throughout the basin. The partial pressure of carbon dioxide (pCO2) tended to be higher, 16 and HCO3  concentrations were lower, in the low-elevation source points than at other 17 positions in the landscape. When coupled with the relatively low concentrations of Si and 18 base cations, this suggests that the availability of primary reactive minerals, rather than 19 carbonic acid concentrations, limits weathering in these low-elevation sources. 20 Mechanical denudation appears to enhance chemical weathering rates not only by 21 refreshing reactive mineral surfaces but also by contributing carbon dioxide from the 22 decomposition of organic-rich material in landslides, which occur frequently. The spatial 23 variability of major solutes appears to depend primarily on the availability of fresh primary 24 reactive minerals, carbon dioxide concentrations, and hydrolysis conditions.

Hurricane Effects on Soil Organic Matter Dynamics and Forest Production in the Luquillo Experimental Forest, Puerto Rico: Results of Simulation Modeling

Hurricane Effects on Soil Organic Matter Dynamics and Forest Production in the Luquillo Experimental Forest, Puerto Rico: Results of Simulation Modeling
Robert L. Sanford, Jr., William J. Parton, Dennis S. Ojima and D. Jean Lodge
Biotropica
Vol. 23, No. 4, Part A. Special Issue: Ecosystem, Plant, and Animal Responses to Hurricanes in the Caribbean (Dec., 1991), pp. 364-372

Abstract: 
The forests and soils at Luquillo Experimental Forest (LEF), Puerto Rico, are frequently disturbed by hurricanes occurring at various frequencies and intensities. We have derived a forest version of the Century soil organic matter model to examine the impact of hurricanes on soil nutrient availability and pool sizes, and forest productivity in the tabonuco forest at Luquillo. The model adequately predicted aboveground plant production, soil carbon, and soil nitrogen levels for forest conditions existing before Hurricane Hugo. Simulations of Hurricane Hugo and of an historical sequence of hurricanes indicated a complex pattern of recovery, especially for the first 10 yr after the hurricanes. After repeated hurricanes, forest biomass was reduced, while forest productivity was enhanced. Soil organic matter, and phosphorus and nitrogen mineralization stabilized at higher levels for the LEF than for hurricane-free tabonuco forest, and organic soil phosphorus was substantially increased by hurricanes. Results from these simulations should be regarded as hypotheses. At present there is insufficient data to validate the results of hurricane model simulations.

Soil Survey of Caribbean National Forest and Luquillo Experimental Forest, Commonwealth of Puerto Rico

Huffaker L (2002) Soil Survey of the Caribbean National Forest and Luquillo
Experimental Forest, Commonwealth of Puerto Rico (Interim Publication).
US Department of Agriculture, Natural Resource Conservation Service,
Washington, DC, US.

Abstract: 
This soil survey contains information that affects land use planning in this survey area. It contains predictions of soil behavior for selected land uses. The survey also highlights soil limitations, improvements needed to overcome the limitations, and the impact of selected land uses on the environment. This soil survey is designed for many different users. Foresters, land use planners, and researchers can use it to evaluate the potential of the soil and the management needed for maximum use and production. Planners, community officials, engineers, and builders can use the survey to plan land use, select sites for construction, and identify special practices needed to ensure proper performance. Conservationists, teachers, students, and specialists in recreation, wildlife management, waste disposal, and pollution control can use the survey to help them understand, protect, and enhance the environment. Various land use regulations of Federal, Commonwealth, and local governments may impose special restrictions on land use or land treatment. The information in this report is intended to identify soil properties that are used in making various land use or land treatment decisions. Statements made in this report are intended to help the land users identify and minimize the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are shallow to bedrock. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. These and many other soil properties that affect land use are described in this soil survey. Broad areas of soils are shown on the general soil map. The location of each soil is shown on the detailed soil maps. Each soil in the survey area is described. Information on specific uses is given for each soil. Help in using this publication and additional information are available at the local office of the Natural Resources Conservation Service, the Forest Service, or the Cooperative Extension Service.

predicting landslide vegetation in patches on landscape gradients in puerto rico

Myster, R.W., Thomlinson, J.R., and Larsen, M.C., 1997, Predicting landslide vegetation in patches on landscape gradients in Puerto Rico: Landscape Ecology, v. 12 p. 299-307.

Abstract: 
We explored the predictive value of common landscape characteristics for landslide vegetative stages in the LuquilloExperimental Forest of Puerto Rico using four different analyses. Maximum likelihood logistic regression showed that aspect, age, and substrate type could be used to predict vegetative structural stage. In addition it showed that the structural complexity of the vegetation was greater in landslides (1) facing the southeast (away from the dominant wind direction of recent hurricanes), (2) that were older, and (3) that had volcaniclastic rather than dioritic substrate. Multiple regression indicated that both elevation and age could be used to predict the current vegetation, and that vegetation complexity was greater both at lower elevation and in older landslides. Pearson product-moment correlation coefficients showed that (1) the presence of volcaniclastic substrate in landslides was negatively correlated with aspect, age, and elevation, (2) that road association and age were positively correlated and (3) that slope was negatively correlated with area. Finally, principal components analysis showed that landslides were differentiated on axes defined primarily by age, aspect class, and elevation in the positive direction, and by volcaniclastic substrate in the negative direction. Because several statistical techniques indicated that age, aspect, elevation, and substrate were important in determining vegetation complexity on landslides, we conclude that landslide succession is influenced by variation in these landscape traits. In particular, we would expect to find more successional development on landslides which are older, face away from hurricane winds, are at lower elevation, and are on volcaniclastic substrate. Finally, our results lead into a hierarchical conceptual model of succession on landscapes where the biota respond first to either gradients or disturbance depending on their relative severity, and then to more local biotic mechanisms such as dispersal, predation and competition.

Research plan for the investigation of water, energy, and biogeochemical budgets in the Luquillo mountains, Puerto Rico

Larsen, M.C., Collar, P.D., and Stallard, R.F., 1993, Research plan for the investigation of water, energy, and biogeochemical budgets in the Luquillo mountains, Puerto Rico: U.S. Geological Survey Open-file Report 92-150, 19 p.

Abstract: 
The Luquillo mountains of eastern Puerto Rico are the site of U. S. Geological Survey (USGS) research into biogeochemical and geomorphic processes that control the movement and transformation of water, energy, bedrock weathering products, and nutrients in the earth-surface environment. This study was begun in 1990 and is scheduled to last three years, with the possibility of being extended for further data collection. The study area for this research effort includes the 113 square kilometers Luquillo Experimental Forest (LEF) that is administered by the U. S. Forest Service. The LEF has been the site of ongoing research since 1988 as part of the National Science Foundation's Long Term Ecological Research program. In addition, comparative studies are being conducted in the Río Grande de Loíza basin (Loíza basin), an urban and agriculturally developed 600 square kilometers watershed located immediately to the west of the LEF. The principal elements of the study described in the report are as follows: Determination of biogeochemical budgets: water, energy, carbon, nutrient, ion, sediment, and gas budgets will be calculated in two LEF watersheds instrumented with meteorologic, soil, hydrologic, and ground-water monitoring equipment. A biweekly time series of samples is being collected. In addition, intensive sampling is undertaken during selected storms. Study of weathering, erosion, and mass-wasting processes in undeveloped watersheds of contrasting lithology: chemical-weathering, erosion, and mass-wasting processes in watersheds underlain by the two dominant rock types, volcaniclastic and quartz diorite, are being compared. The effects of mass wasting on biogeochemical cycling in each rock type will be evaluated through a compilation of physical, chemical, and mineralogic properties for a chronosequence of landslides. Water and sediment budgets will be used to develop a conceptual model of hillslope hydrology and landform evolution. Comparison of weathering and gas flux in developed and forested watersheds: paired basins were selected and gaged in the relatively undisturbed LEF and in the agriculturally developed Loíza basin. Budgets of all aqueous constituents will be compared and contrasted in the developed and forested basins of similar lithology. Gas-flux differences (carbon dioxide, nitrogen dioxide, methane) between developed and undeveloped areas will be evaluated using chamber techniques and the results related to land-use differences. Measurement of reservoir and agricultural pond gas fluxes: methane production is being measured in selected reservoirs and agricultural ponds in and near the Loíza basin and LEF. A regional methane budget will be calculated.

Denudation rates determined from the accumulation of in situ-produced 10Be in the luquillo experimental forest, Puerto Rico

Brown, E.T., Stallard, R.F., Larsen, M.C., Raisbeck, G.M., Yiou,
F., 1995b. Denudation rates determined from the accumulation of in
situ-produced Be in the Luquillo Experimental Forest, Puerto
Rico. Earthand Planetary Science Letters 129, 193}202.

Abstract: 
We present a simple method for estimation of long-term mean denudation rates using in situ-produced cosmogenic 10Be in fluvial sediments. Procedures are discussed to account for the effects of soil bioturbation, mass wasting and attenuation of cosmic rays by biomass and by local topography. Our analyses of 10Be in quartz from bedrock outcrops, soils, mass-wasting sites and riverine sediment from the Icacos River basin in the Luquillo Experimental Forest, Puerto Rico, are used to characterize denudation for major landform elements in that basin. The 10Be concentration of a discharge-weighted average of size classes of river sediment corresponds to a long-term average denudation of ≈ 43 m Ma−1, consistent with mass balance results.

Evaporation from a tropical rain forest, Luquillo Experimental Forest, eastern Puerto Rico

Schellekens, J., L. A. Bruijnzeel, F. N. Scatena, N. J. Bink, and F. Holwerda (2000), Evaporation from a tropical rain forest, Luquillo Experimental Forest, eastern Puerto Rico, Water Resour. Res., 36(8), 2183–2196, doi:10.1029/2000WR900074.

Abstract: 
Evaporation losses from a watertight 6.34 ha rain forest catchment under wet maritime tropical conditions in the Luquillo Experimental Forest, Puerto Rico, were determined using complementary hydrological and micrometeorological techniques during 1996 and 1997. At 6.6 mm d−1 for 1996 and 6.0 mm d−1 for 1997, the average evapotranspiration (ET) of the forest is exceptionally high. Rainfall interception (Ei), as evaluated from weekly throughfall measurements and an average stemflow fraction of 2.3%, accounted for much (62–74%) of the ET at 4.9 mm d−1 in 1996 and 3.7 mm d−1 in 1997. Average transpiration rates (Et) according to a combination of the temperature fluctuation method and the Penman-Monteith equation were modest at 2.2 mm d−1 and 2.4 mm d−1 in 1996 and 1997, respectively. Both estimates compared reasonably well with the water-budget-based estimates (ET − Ei) of 1.7 mm d−1 and 2.2 mm d−1. Inferred rates of wet canopy evaporation were roughly 4 to 5 times those predicted by the Penman-Monteith equation, with nighttime rates very similar to daytime rates, suggesting radiant energy is not the dominant controlling factor. A combination of advected energy from the nearby Atlantic Ocean, low aerodynamic resistance, plus frequent low-intensity rain is thought to be the most likely explanation of the observed discrepancy between measured and estimated Ei.
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