fine roots

STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS

Beard, Karen H., Kristiina A. Vogt, Daniel J. Vogt, Frederick N. Scatena, Alan P. Covich, Ragnhildur Sigurdardottir, Thomas G. Siccama, and Todd A. Crowl. 2005. STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS. Ecological Monographs 75:345–361. [doi:10.1890/04-1114]

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.

Decay rate and substrate quality of fine roots and foliage of two tropical tree species in the Luquillo Experimental Forest, Puerto Rico

Bloomfield, J., K. A. Vogt, and D. J. Vogt. 1993. Decay rate and substrate quality of fine roots and foliage of two tropical tree species in the Luquillo Experimental Forest, Puerto Rico. Plant and Soil 150:233-245.

Abstract: 
Decomposition rates, initial chemical composition, and the relationship between initial chemistry and mass loss of fine roots and foliage were determined for two woody tropical species, Prestoea montana and Dacryodes excelsa, over a gradient of sites in two watersheds in the Luquillo Experimental Forest, Puerto Rico. At all locations, fine roots decayed significantly more slowly than foliage during the initial 6 months. Substrate quality of the initial tissue showed marked differences between roots and foliage when using cell wall chemistry, secondary chemistry and total elemental analysis as indices. Quantity of acid detergent fiber (ADF) (non-digestible cell wall fiber) and lignin content were higher for roots than leaves: D. excelsa roots had 55.3% ADF and 28.7% lignin while leaves had 36.2% ADF and 11.8% lignin; P. montana roots had 68.0% ADF and 26.8% lignin while leaves had 48.5% ADF and 16.1% lignin. Aluminum concentrations were higher in fine roots (843 mg kg -x in D. excelsa, 1500 mg kg -x in P. montana) than leaves (244mg kg -x in D. excelsa, 422mgkg -1 in P. montana), while calcium concentrations were higher in foliage (5.5 mg g-1 in D. excelsa, 7.8 mg g-X in P. montana) than roots (3.4mgg -1 in D. excelsa, 3.1 mgg -x in P. montana). Nitrogen did not show any trend with tissue or species type. A linear model between mass remaining after 6 months and initial tissue chemistry could be developed only for calcium (r 2= 0.64).

STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS

Beard, Karen H., Kristiina A. Vogt, Daniel J. Vogt, Frederick N. Scatena, Alan P. Covich, Ragnhildur Sigurdardottir, Thomas G. Siccama, and Todd A. Crowl. 2005. STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS. Ecological Monographs 75:345–361. [doi:10.1890/04-1114]

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.
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