Publication Year
2005
Source
Ecological Monographs
DOI
Abstract
Little is known about ecosystem-level responses to multiple, climatic disturbance
events. In the subtropical forests of Puerto Rico, the major natural disturbances
are hurricanes and droughts. We tested the ecosystem-level effects of these disturbances
in sites with different land use histories. From 1989 to 1992, data were collected to determine
the effects of Hurricane Hugo and two droughts on litterfall inputs, fine-root biomass, and
decomposition rates in three topographic locations (stream, riparian, upslope) within two
watersheds. From 1994 to 1998, we added a third watershed and an experiment in which
coarse-wood levels were manipulated to simulate hurricane inputs. Data were collected on
tree and palm growth rates, litterfall inputs, fine-root biomass, and decomposition rates.
From 1994 to 1998, four hurricanes and three droughts were recorded.
Measured parameters had unique responses and recovery rates to hurricanes and
droughts. Litterfall inputs returned to long-term mean rates within one month following
droughts and small-to-moderate hurricanes but required five years to recover after an intense
hurricane. In contrast, fine-root biomass recovered seven months after an intense hurricane
but failed to recover after five years following a severe drought. Despite the dramatic effects
of these weather events on some ecosystem parameters, we found that aboveground measures
of tree and palm growth were more affected by preexisting site conditions (e.g.,
nitrogen availability due to past land use activities) than hurricanes or droughts. The addition
of coarse woody debris increased tree and palm growth, fine-root biomass, and litter production;
however, in the case of tree and palm growth, this effect was least measurable in
the sites with the highest productivity. We found that decomposition rates were more
controlled by litter quality than weather conditions. In conclusion, we found that certain
ecosystem structures (e.g., canopy structure and fine-root biomass) generally recovered
more slowly from disturbance events than certain ecosystem processes (e.g., plant growth
rates, decomposition rates). We also found that past land use activities and disturbance
legacies were important in determining the responses and recovery rates of the ecosystem
to disturbance.
events. In the subtropical forests of Puerto Rico, the major natural disturbances
are hurricanes and droughts. We tested the ecosystem-level effects of these disturbances
in sites with different land use histories. From 1989 to 1992, data were collected to determine
the effects of Hurricane Hugo and two droughts on litterfall inputs, fine-root biomass, and
decomposition rates in three topographic locations (stream, riparian, upslope) within two
watersheds. From 1994 to 1998, we added a third watershed and an experiment in which
coarse-wood levels were manipulated to simulate hurricane inputs. Data were collected on
tree and palm growth rates, litterfall inputs, fine-root biomass, and decomposition rates.
From 1994 to 1998, four hurricanes and three droughts were recorded.
Measured parameters had unique responses and recovery rates to hurricanes and
droughts. Litterfall inputs returned to long-term mean rates within one month following
droughts and small-to-moderate hurricanes but required five years to recover after an intense
hurricane. In contrast, fine-root biomass recovered seven months after an intense hurricane
but failed to recover after five years following a severe drought. Despite the dramatic effects
of these weather events on some ecosystem parameters, we found that aboveground measures
of tree and palm growth were more affected by preexisting site conditions (e.g.,
nitrogen availability due to past land use activities) than hurricanes or droughts. The addition
of coarse woody debris increased tree and palm growth, fine-root biomass, and litter production;
however, in the case of tree and palm growth, this effect was least measurable in
the sites with the highest productivity. We found that decomposition rates were more
controlled by litter quality than weather conditions. In conclusion, we found that certain
ecosystem structures (e.g., canopy structure and fine-root biomass) generally recovered
more slowly from disturbance events than certain ecosystem processes (e.g., plant growth
rates, decomposition rates). We also found that past land use activities and disturbance
legacies were important in determining the responses and recovery rates of the ecosystem
to disturbance.
Research Track Category