defoliation

Invertebrate communities in a tropical rain forest canopy in Puerto Rico following Hurricane Hugo

Schowalter, T. W., and L. M. Ganio. 1999. Invertebrate communities
in a tropical rain forest canopy in Puerto Rico
following Hurricane Hugo. Ecological Entomology 24:
191–201.

Abstract: 
1. Canopy invertebrate responses to Hurricane Hugo, tree species, and recovery time were examined at the Luquillo Experimental Forest in Puerto Rico during 1991–92 and 1994–95. Six tree species representing early and late successional stages were examined in paired plots representing severe hurricane disturbance (most trees toppled) and light hurricane disturbance (all trees standing and most branches intact). 2. Hurricane disturbance affected invertebrate abundances significantly. Sap-suckers and molluscs were more abundant, and defoliators, detritivores, and emergent aquatic insects were less abundant in recovering tree-fall gaps than in intact forest during this 5-year period. These changes in functional organisation are consistent with comparable studies of arthropod responses to canopy removal during harvest in temperate forests. 3. Tree species also affected invertebrate abundances significantly, but invertebrate communities did not differ significantly between the three early successional and three later successional tree species. 4. Most taxa showed significant annual variation in abundances, but only two Homoptera species showed a significant linear decline in abundance through time, perhaps reflecting long-term trends during recovery. 5. Leaf area missing, an indicator of herbivore effect on canopy processes, showed significant seasonal and annual trends, as well as differences among tree species and hurricane treatments. Generally, leaf area missing peaked during the wet season each year, but reached its highest levels during an extended drought in 1994. Leaf area missing also tended to be higher on the more abundant tree species in each disturbance treatment. 6. Herbivore abundances and leaf area missing were not related to concentrations of nitrogen, phosphorous, potassium, or calcium in the foliage. 7. This study demonstrated that invertebrate community structure and herbivory are dynamic processes that reflect the influences of host species and variable environmental conditions.

Growth Rings, Phenology, Hurricane Disturbance and Climate in Cyrilla racemiflora L., a Rain Forest Tree of the Luquillo Mountains, Puerto Rico

Growth Rings, Phenology, Hurricane Disturbance and Climate in Cyrilla racemiflora L., a Rain Forest Tree of the Luquillo Mountains, Puerto Rico
Allan P. Drew
Biotropica
Vol. 30, No. 1 (Mar., 1998), pp. 35-49

Abstract: 
The growth phenology of Cyrilla racemiflora L., the dominant tree species of the montane rain forest, (subtropical lower montane rain forest, sensu Holdridge) of the Luquillo Mountains of Puerto Rico was studied intensively during 1989, and then semiannually through mid-1993 to determine the periodicity of changes in xylem structure. Four trees at 770 m were monitored for flowering, branch elongation, leaf litterfall, and xylem cell growth and differentiation in the lower stem, and these events were related to local seasonal patterns of rainfall and temperature. Hurricane Hugo defoliated study trees in September, 1989. Bud-break and branch elongation in March, 1989 were followed by earlywood xylem cell production in the lower stem in April and the onset of flowering in May. Leaf litterfall was greatest between April and June, coinciding with peak branch growth and new leaf formation. Latewood xylem was produced in December. The general phenological pattern was synchronized between trees and over study years. Vessel diameter and density were monitored along with thickness of earlywood and latewood and the former converted to vessel lumen area, a measure of xylem conductance capacity. Annual growth rings were formed with periods of earlywood and latewood production coinciding with traditional summer (rainy) and winter (dry) seasons, respectively, in the Luquillo Mountains. Hurricane defoliation was followed by heavy flowering in 1990, a year of reduced branch elongation and annual xylem ring width, and was associated with maximum vessel lumen area, as was flowering in 1989, prior to the hurricane. Hurricane Hugo provided a perturbation that, through its elicited stress response, allowed for the demonstration of the interplay between flowering, branching, structural growth of xylem, and xylem function.

Soil Studies in the El Verde Rain Forest

Abstract: 
Some Physical and Chemical properties of tropical rain forest soils at El Verde, Puerto Rico, were investigated before and after treatments with gamma radiation from a 137Cs source and after mechanical defoliation of the vegetation. Flushes of soil ions were observed in soils after treatment; subsequently, ioic concentrations were lower than they were at the start. The profiles of cations indicated heterogeneous patterns with both poscolization and laterication active. Infiltration rates for the relatively undisturbed soils studied were unusually high (30 and 60 cm/hr) whenu associated with low bulk density. Lower infiltration rates and higher bulk-density values were associated with level areas rather than with slopes.
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