LUQ Data Sets by Contact

The purpose of this data set is to document recovery of vegetation in removal plots in landslides in the Luquillo Experimental Forest (LEF.)

Hongqing Wang, a Ph.D graduate student of SUNY-ESF, with the help of many others, took soil samples in 119 locations over the entire Luquillo Experimental Forest (LEF) during the summer of 1998 and 1999. Soil organic carbon, total nitrogen and acid-extractable phosphorus were measured in the laboratory of SUNY-ESF; soil moisture and bulk density were measured at the laboratory of the El Verde Station of UPR. The geodetic coordinates (Lat., Lon.) and elevation of each sampling location were determined using a Global Positioning System (GPS Pathfinder Basic Receivers, Trimble Navigation Ltd.) in the field. Meanwhile, slope angle, aspect and topographic features (Ridge, slope I (<35 deg.), slope II (>=35 deg.), valleys) were also measured and observed in the field.

(1) Exchangeable cation concentrations were measured using different soil extracting procedures (fresh soil and air-dried and ground soil) to establish a range of nutrient availability in the soil, and to determine the relationship between different, but commonly used laboratory protocols.

(2) Soils extracted using fresh soils generally yielded significantly lower exchangeable Ca , Mg, and K concentrations than soils which were dried and ground prior to extraction. Soil nutrients generally decreased with depth in the soil.

(3) Several soil properties varied predictably across the landscape and could be viewed in the context of a simple catena model. In the surface soils, exchangeable base cation concentrations and pH decreased along a gradient from ridge tops to riparian valleys, while soil organic matter, exchangeable Fe and acidity increased along this gradient. On the ridges, N,P, and K were positively correlated with soil organic matter; on slopes, N and P were positively correlated with organic matter, and Ca, Kg, and pH were negatively correlated with exchangeable Fe.

(4) Soil nutrient availability in the upper catena appears to be primarily controlled by biotic processes, particularly the accumulation of organic matter. Periodic flooding and impeded drainage in the lower catena resulted in a more heterogeneous environment. Drying and grinding the soil prior to extraction had a greater impact on exchangeable cations from the upper catena than in the valley positions, probably due to greater soil organic matter content. See Silver, W.L., F.N. Scatena, A.H. Johnson, T.G. Siccama, and M.J. Sanchez. 1994. Nutrient availability in a montane wet tropical forest in Puerto Rico: spatial patterns and methodological considerations. Plant and Soil 164:129-145.

Effects of biotic (shrimp) and abiotic (discharge) factors on the depositional environment were quantified in a montane stream in Puerto Rico. Electricity was used experimentally to exclude large (approximately >1cm in length) biota without artificially increasing sedimentation as in cage enclosure/exclosure experiments in stream systems. Shrimp (>1cm in length) were excluded from substrata by semicircular fence hooked up to battery-powered fence chargers which emitted continuous pulses of electricity. Unelectrified control substrata had natural high densities of atyid shrimp. Significantly greater masses of total sediment, fine and large organic particles, and algal biovolume occurred in shrimp exclusion treatments relative to controls. Shrimp exclusion treatments experienced slow and steady accumulation of sediments under base flow conditions and a large stepwise increase in sediment following a storm. No measurable sediment accrued in the presence of natural densities of shrimp under base flow conditions. Shrimp rapidly removed sediments that accrued during the storm (440-620 g*m2 dry mass-1), decreasing sediment mass in control treatments to near prestorm levels (5-13 g*m2 dry mass-1) within 30 h. Atyid shrimp can significantly affect the accumulation of organic and inorganic materials on rock substrata in stream pools between high-discharge events.

Here we test the hypothesis that differences in macrobiotic assemblages can lead to differences in the quantity and quality of organic matter in benthic depositional environments among streams in montane Puerto Rico. We experimentally manipulated biota over a 30-40d period in two streams with distinctly different macrobiotic assemblages: one characterized by high densities of omnivorous shrimps (Decapoda: Atyidae and Xiphocarididae) and no predaceous fishes. To incorporate the natural hydrologic regime and to avoid confounding artifacts associated with cage enclosure/exclosure (e.g., high sedimentation), we used electricity as a mechanism for experimental exclusion, in situ. In each stream, shrimps and/or fishes were excluded from specific areas of rock substrata in four pools using electric "fences" attached to solar-powered fence chargers. In the stream lacking predaceous fishes (Sonadora), the unelectrified control treatment was almost exclusively dominated by high densities of omnivorous shrimps that constantly ingested fine particulate material from rock surfaces. Consequently, the control had significantly lower levels of inorganic sediments, organic material, carbon and nitrogen than the exclusion treatment, as well as less variability in these parameters. Tenfold more organic material (as ash-free dry mass, AFDM) and fivefold more nitrogen accrued in shrimp exclosures (10.6 g AFDM/m2, 0.2 g N/m2) than in controls (1.1 g AFDM/m2, 0.04 g N/m2). By reducing th quantity of fine particulate organic material and associated nitrogen in benthic environments, omnivorous shrimps potentially affect the the supply of this important resource to other trophic levels. The small amount of fine particulate organic matter (FPOM) that remained in control treatments (composed of sparse algal cells0 was of higher quality than that in shrimp exclosures. This is evidenced by the significantly lower carbon-to-nitrogen (C/N) ratio (an indicator of food quality, with relatively low C/N indicating higher food quality) in the control relative to the shrimp exclosure treatment. In contrast, the stream with predaceous fishes (Bisley) was characterized by very low numbers of shrimps, and macrobiota had no significant effect on benthic sediments, organic matter, C, N, and C/N. All parameters were highly variable through time, with levels and ranges in variability similar to the shrimp exclusion treatment in the Sonadora. Our experimental results are consistent with findings of an independent survey of six streams in four different drainages. Four streams that had an abundance of omnivorous shrimps but lacked predaceous fishes, had extremely low levels of fine benthic organic and inorganic material. In contrast, two streams that had low densities of shrimps and contained predaceous fishes had significantly higher levels. Results show a strong linkage between species and ecosystem characteristics: interstream differences in the quantity and quality of fine benthic organic matter resources were determined by the nature of the macrobiotic assemblage. Furthermore, patterns in the distribution of shrimp assemblages reflected landscape patterns in the benthic depositional environment among streams.

Manilkara bidentata is attacked by a specialist leaf miner(Acrocercops sp.(microlepidoptera:gracillariidae).  More than one larvae can be found per mine within a leaf. The purposes of this study is to determine the effect of group feeding for this species since larval density within a leaf vary from 1-14 larvae per mine (Angulo-Sandoval personal observation). This variation allows to determine the effect of larval density on the amount of leaf damage, larval survivorship and larval growth. Leaves with mines varied in area from 10 to 224 cm² (mean = 85.7 cm²) and the number of larvae per leaf ranged from 1 to 14 (mean = 5.7 larvae/mine). There was no relation between the size of the leaf and the number of larvae found within the leaf.

There was a relationship between the number of larvae in a blotch mine and amount of damaged tissue. Herbivory increases from approximately 10% for one larva per leaf to 50% in leaves with eight larvae. In leaves with more than eight larvae, herbivory decreased . There was an effect of initial larval density on percent larval survivorship.Survivorship was high (70%) in leaves with one to three larvae. In intermediate density (4-8 larvae per mine) 50% of larvae survived and in high densities (9 - 14 larvae per mine), only 22% survived. Even though there was a decrease in larvae number in high densities, the final number of larvae remained higher, compared with low or intermediate densities. A linear relationship was found between number of larvae present in the leaf and the time it took the larvae to complete their larval stage. Larvae in high density (> 9 larvae per mine) tended to develop faster (3-8 days) than larvae in low densities (5 - 10 days). Larval size upon emergence ranged from 8 to 12 mm (mean= 9.27) but there was no effect of larval density on the final larval size. The total number of surviving larvae varied according to the initial larval number and was highest in mines with eight individuals of which on average 4.7 survived. The number of surviving larvae was less than three for all other clutch sizes. Even though eight larvae appears to be the optimum clutch size, most females produced smaller clutches (4- 6 larvae per leaf).All larvae that emerged built a cocoon and 90% emerged as butterflies.

Permanent plot data is expected to show (1) rapid increases in percent cover and tree stem density, and (2) rapid turnover from early to late successional plant species. Plant-plant competition indices should show quick increases in intensity with exotics as top competitors which may lead to exclusion of some trees common after landslide and pasture disturbance. Spatial patterns of invading trees should include edge effects due to dispersal limitation with clumping of bird-dispersed species before the first five years. Because of increased nitrogen levels due to plantings of Inga Sp. with coffee, trees should grow, as measured by biomass (productivity), height and basal diameter increases, significantly faster compared to landslide.

In this project we try to find out the relationship between the primary production and the soil organic carbon fractions.

Five tree species in 1991, six during 1992-1995, were selected to represent early and late successional forests at El Verde. These trees were sampled in both gap and non-gap plots resulting from Hurricane Hugo.