Garcia-Montiel D.C.

Plant responses to simulated hurricane impacts in a subtropical wet forest, Puerto Rico

Shiels, Aaron B.; Zimmerman, Jess K.; García-Montiel, Diana C.; Jonckheere, Inge; Holm, Jennifer; Horton, David; Brokaw, Nicholas. 2010. Plant responses to simulated hurricane impacts in a subtropical wet forest, Puerto Rico. Journal of Ecology. doi: 10.1111/j.1365-2745.2010.01646.x.

1. We simulated two key components of severe hurricane disturbance, canopy openness and detritus deposition, to determine the independent and interactive effects of these components on woody plant recruitment and forest structure. 2. We increased canopy openness by trimming branches and added or subtracted canopy detritus in a factorial design. Plant responses were measured during the 4-year study, which followed at least 1 year of pre-manipulation monitoring. 3. The physical conditions of canopy openness and detritus deposition in our experiment resembled the responses to Hurricane Hugo, a severe category 4 hurricane that struck this forest in 1989. 4. Canopy detritus deposition killed existing woody seedlings and provided a mechanical barrier that suppressed seedling recruitment. The increase in understorey light caused by canopy trimming stimulated germination from the seed bank and increased seedling recruitment and density of pioneer species several hundred-fold when hurricane debris was absent. Many significant interactions between trimming and detritus deposition were evident from the manner in which seedling density, recruitment and mortality changed over time, and subsequently influenced the composition of woody stems (individuals ‡ 1 cmd.b.h.). 5. When the canopy was trimmed, stem densities increased> 2-fold and rates of recruitment into the stem size class increased> 25-fold. Trimming had no significant effect on stem mortality. The two dominant species that flourished following canopy trimming were the pioneer species Cecropia schreberiana and Psychotria berteriana. Deposition of canopy detritus had little effect on stems, although basal area increased slightly when detritus was added. There were no evident effects of the interactions between canopy trimming and detritus deposition on stems. 6. Synthesis. The separate and interactive effects of canopy openness and detritus deposition result in variable short-term trajectories of forest recovery. However, the short interval of increased canopy openness due to hurricane impacts and its influence on the recruitment of pioneer trees is the dominant factor that drives short-termrecovery and may alter long-term structure and composition of the forest.

The effect of human activity on the structure and composition of a tropical forest in Puerto Rico

Garcia-Montiel, D.C.; Scatena, F.N. 1994. The effect of human activity on the structure and composition of a tropical forest in Puerto Rico. Forest Ecology and Management, 63 :57-78.

From European settlement to the 1940s, the Bisley watersheds of the Luquilio Experimental Forest, Puerto Rico, were used for agroforestry, selective logging, charcoal production, and timber management. Each of these activities affected different parts of the landscape in different ways and at different times. After nearly 50 years of unhindered regeneration, six impacts remain apparent: ( 1 ) shifts in the dominance and age structure of canopy species; (2) immigration of subcanopy crop species and the establishment of banana as a riparian dominant; (3) increases in the importance of canopy species used for coffee shade; (4) the impoverishment of certain commercial timber species; (5) an increase in the density of palms around abandoned charcoal kilns; (6) a reduction in the regeneration of canopy species around abandoned charcoal kilns. Changes in the above-ground nutrient pool may also have occurred. Human disturbances in the study site were progressive rather than discrete events, had adverse impacts on forest regeneration, and increased the spatial heterogeneity of the forest.
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