Beard K.H.

Indigenous Knowledge Informing Management of Tropical Forests: The Link between Rhythms in Plant Secondary Chemistry and Lunar Cycles

Vogt, Kristiina A.; Beard, Karen H.; Hammann, Shira; O’Hara Palmiotto, Jennifer; Vogt,Daniel J.; Scatena, Frederick N.; Hecht, Brooke P. 2002. Indigenous Knowledge Informing Management of Tropical Forests: The Link between Rhythms in Plant Secondary Chemistry and Lunar Cycles.. Ambio Vol. 31 No. 6, Sept. 2002

Abstract: 
This research used knowledge of the indigenous practice of timing nontimber forest product harvest with the full moon to demonstrate that chemicals controlling the decomposition rate of foliage fluctuate with the lunar cycle and may have developed as a result of plant-herbivore interactions. Indigenous knowledge suggests that leaves harvested during the full moon are more durable. Palm leaves harvested during the full moon had higher total C, hemicellulose, complex C and lower Ca concentrations. These chemical changes should make palm leaves less susceptible to herbivory and more durable when harvested during the full moon. This study proposes a mechanism by which plants in the tropics minimize foliage herbivory and influence the decomposition rates of senesced leaves and their durability, especially during the full moon. This research supports the need to use natural life cycles in managing forests and provides a scientific basis for an indigenous community's harvesting practice.

Quantitative Assessment of Habitat Preferences for the Puerto Rican Terrestrial Frog, Eleutherodactylus coqui

Beard, Karen H.; Mccullough, Sarah; Eschtruth, Anne K. 2003. Quantitative Assessment of Habitat Preferences for the Puerto Rican Terrestrial Frog, Eleutherodactylus coqui. Journal of Herpetology, Vol. 37, No. 1, :10-17,.

Abstract: 
We conducted a quantitative analysis of adult and juvenile Eleutherodactylus coqui (coquí) habitat preferences in Puerto Rico. The analysis consisted of two surveys: one to quantify potential habitat and another to quantify habitat use. Coquís were found to use most habitats available to them; however, adults and juveniles preferred different plant species, habitat structural components, and heights from the forest floor. Adult and juvenile coquís had opposite associations with many important plant species in the forest (e.g., Prestoea montana and Heliconia carabea) and habitat structural components. Adults had a negative association with leaves and a positive association with leaf litter. Juveniles showed the opposite trend. Adults were more evenly distributed with respect to height than were juveniles, with adults preferring heights around 1.1 m and juveniles preferring heights closer to the forest floor. The quantitative survey technique for determining habitat preferences used in this study generally confirmed coquí habitat preferences known from qualitative assessments.

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.

Top-down effects of a terrestrial frog on forest nutrient dynamics

Beard,Karen H.; Vogt, Kristiina A.; Kulmatiski,Andrew 2002. Top-down effects of a terrestrial frog on forest nutrient dynamics.. Oecologia 133 :583 593.

Abstract: 
Many studies have found top-down effects of predators on prey, but few studies have linked top-down effects of vertebrate predators to nutrient cycling rates in terrestrial systems. In this study, large and significant effects of a terrestrial frog, Eleutherodactylus coqui (coqu), were recorded on nutrient concentrations and fluxes in a subtropical wet forest. In a manipulative experiment, coqus at natural densities were contained in or excluded from 1 m3 enclosures for 4 months. Chemistry of leaf wash (throughfall), foliage, and decomposed leaf litter in the enclosures were measured as indicators of coqu effects on nutrient cycling. Coqu exclusion decreased elemental concentrations in leaf washes by 83% for dissolved organic C, 71% for NH4 +, 33% for NO3 –, 60% for dissolved organic N, and between 60 and 100% for Ca, Fe, Mg, Mn, P, K, and Zn. Coqu exclusion had no effect on foliar chemistry of plants transplanted into the enclosures. However, coqu exclusion decreased nutrient availability in decomposing mixed leaf litter by 12% and 14% for K and P, respectively, and increased C:N ratios by 13%. Changes in nutrient concentrations that occurred with coqu exclusion appear to be due to concentrations of nutrients in coqu waste products and population turnover. The results supported our hypothesis that coqus have an observable effect on nutrient dynamics in this forest. We suggest that the primary mechanism through which they have this effect is through the

Quantitative Assessment of Habitat Preferences for the Puerto Rican Terrestrial Frog, Eleutherodactylus coqui

Quantitative Assessment of Habitat Preferences for the Puerto Rican Terrestrial Frog, Eleutherodactylus coqui
Karen H. Beard, Sarah McCullough and Anne K. Eschtruth
Journal of Herpetology
Vol. 37, No. 1 (Mar., 2003), pp. 10-17

Abstract: 
We conducted a quantitative analysis of adult and juvenile Eleutherodactylus coqui (coquí) habitat preferences in Puerto Rico. The analysis consisted of two surveys: one to quantify potential habitat and another to quantify habitat use. Coquís were found to use most habitats available to them; however, adults and juveniles preferred different plant species, habitat structural components, and heights from the forest floor. Adult and juvenile conquís had opposite associations with many important plant species in the forest (e.g., Prestoea montana and Heliconia carabea) and habitat structural components. Adults had a negative association with leaves and a positive association with leaf litter. Juveniles showed the opposite trend. Adults were more evenly distributed with respect to height than were juveniles, with adults preferring heights around 1.1 m and juveniles preferring heights closer to the forest floor. The quantitative survey technique for determining habitat preferences used in this study generally confirmed coquí habitat preferences known from qualitative assessments.

The effects of the frog Eleutherodactylus coqui on invertebrates and ecosystem processes at two scales in the Luquillo Experimental Forest, Puerto Rico

The Effects of the Frog Eleutherodactylus coqui on Invertebrates and Ecosystem Processes at Two Scales in the Luquillo Experimental Forest, Puerto Rico
Karen H. Beard, Anne K. Eschtruth, Kristiina A. Vogt, Daniel J. Vogt and Frederick N. Scatena
Journal of Tropical Ecology
Vol. 19, No. 6 (Nov., 2003), pp. 607-617

Abstract: 
Determining the ubiquity of top-down control effects of predators on their prey and ecosystem processes is important for understanding community and ecosystem-level consequences that may result from predator loss. We conducted experiments at two spatial scales to investigate the effects of terrestrial frogs (Eleutherodactylus coqui) on aerial and litter invertebrates, plant growth and herbivory, and litter decomposition. At both scales, frogs reduced aerial invertebrates and leaf herbivory, but had no effect on litter invertebrates. At the smaller scale, frogs increased foliage production rates, measured as the number of new leaves and new leaf area produced, by 80% and decomposition rates by 20%. The influence of E. coqui on increasing primary productivity and decomposition rates at the smaller scale appeared to be a result of elimination and excretion rather than of controlling prey. While the results provide evidence for frogs controlling herbivorous prey at both scales, species effects on ecosystem processes were only detectable at the smaller scale. The results highlight the difficulties in conducting experiments at large spatial scales. The findings from this study imply that the loss of amphibians and other species of higher trophic levels may affect nutrient cycling rates in tropical forests.

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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