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• 1. [Article] Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine

  Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity ...

  Citation × Citation Citation Abstract Copy Title: Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine Author: Lucash, Melissa S., Joslin, J. Devereux, Yanai, Ruth D. Year: 2005 Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity of K, NH+ 4, NO 3 −, Mg and Ca across a range of solution concentrations by roots of mature loblolly pine at Calhoun Experimental Forest in October 2001, July 2001, and April 2002. Uptake capacity was generally lowest in July; rates in October were similar to those in April. Across a range of concentrations, antecedent nutrient solution concentrations affected the temporal patterns in uptake in July but not in October or April. In July, uptake of NH+ 4, Mg and Ca was positively correlated with concentration when roots were exposed to successively lower concentrations, but negatively correlated with concentration when exposed to successively higher concentrations. In contrast, uptake in October was constant across the range of concentrations, while uptake increased with concentration in April. As in studies of other species, we found greater uptake of NH+ 4 than NO 3 −. Temporal patterns of uptake capacity are difficult to predict, and our results indicate that experimental conditions, such as experiment duration, antecedent root conditions and nutrient solution concentration, affect measured rates of nutrient uptake. Title: Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine Author: Lucash, Melissa S., Joslin, J. Devereux, Yanai, Ruth D. Year: 2005 Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity of K, NH+ 4, NO 3 −, Mg and Ca across a range of solution concentrations by roots of mature loblolly pine at Calhoun Experimental Forest in October 2001, July 2001, and April 2002. Uptake capacity was generally lowest in July; rates in October were similar to those in April. Across a range of concentrations, antecedent nutrient solution concentrations affected the temporal patterns in uptake in July but not in October or April. In July, uptake of NH+ 4, Mg and Ca was positively correlated with concentration when roots were exposed to successively lower concentrations, but negatively correlated with concentration when exposed to successively higher concentrations. In contrast, uptake in October was constant across the range of concentrations, while uptake increased with concentration in April. As in studies of other species, we found greater uptake of NH+ 4 than NO 3 −. Temporal patterns of uptake capacity are difficult to predict, and our results indicate that experimental conditions, such as experiment duration, antecedent root conditions and nutrient solution concentration, affect measured rates of nutrient uptake. Close

• 2. [Article] Social-Ecological Dynamics of Coral Reef Resource Use and Management

  This dissertation investigates social and ecological factors that facilitate effective management of coral reefs as social-ecological systems. Meta-analytical and field-based methods were employed to examine ...

  Citation × Citation Citation Abstract Copy Title: Social-Ecological Dynamics of Coral Reef Resource Use and Management Author: Freed, Sarah J. Year: 2013 This dissertation investigates social and ecological factors that facilitate effective management of coral reefs as social-ecological systems. Meta-analytical and field-based methods were employed to examine current management challenges and identify strategies that improve management effectiveness and coral reef health. A meta-analysis was used to evaluate biological indicators of reef health in relation to the types of fishing regulations in place (no-take areas, gear restriction areas, and periodic closures) and the actor groups (community-based, co-management, state, private) involved in management efforts for coral reef fisheries throughout the world. Other than enhancement of fish biomass within no-take areas that was significantly greater than in gear restriction areas, most biological indicators benefitted similarly from management techniques of no-take areas and gear restriction areas. Community-based and co-management were the best performing management arrangements for some biological outcomes but require further case studies to verify findings. Investigation of management effects by region indicated that previously degraded reefs received fewer benefits from management implementation than did relatively healthier reefs. For field investigations, the Comoros islands in the Western Indian Ocean served as a model for tropical coral reefs with challenging socioeconomic contexts, high biodiversity, and high vulnerability to coral reef degradation. Empirical study at 21 sites was used to identify the relative effects of natural and anthropogenic threats to coral reefs of the Comoros. Most previous studies of reef health focus on primarily natural factors or a single anthropogenic threat. This study examined suites of natural factors and human activities to identify the relative importance of each on reef health. Human activities including fishing, sand extraction, and beachfront housing and development were the best predictors of reef health status. Most notably, human population and fishing predicted fish richness, abundance, and biomass with seasonal variation in the effects, while site orientation strongly predicted benthic cover. Field studies in the Comoros were also used to investigate the roles of community and state actors in co-management and compare effectiveness of comanagement across sites with varying levels of actor participation. Effective management was found to occur with community or `meta-community' (in this case, a Marine Protected Area in which the efforts of several communities were organized) participation in governance and support of state or external agents, while resilient management that overcame considerable challenges was found to occur only with strong community participation and leadership in governance. External agents were found to contribute to development of meta-community governance structure and initiation of community participation through education and capacity building. The findings from these studies reveal that coral reef management can be improved through context appropriate regulations that address detrimental human activities and through wide acceptance and participation in governance with cooperation among states, communities, and external agents. Title: Social-Ecological Dynamics of Coral Reef Resource Use and Management Author: Freed, Sarah J. Year: 2013 This dissertation investigates social and ecological factors that facilitate effective management of coral reefs as social-ecological systems. Meta-analytical and field-based methods were employed to examine current management challenges and identify strategies that improve management effectiveness and coral reef health. A meta-analysis was used to evaluate biological indicators of reef health in relation to the types of fishing regulations in place (no-take areas, gear restriction areas, and periodic closures) and the actor groups (community-based, co-management, state, private) involved in management efforts for coral reef fisheries throughout the world. Other than enhancement of fish biomass within no-take areas that was significantly greater than in gear restriction areas, most biological indicators benefitted similarly from management techniques of no-take areas and gear restriction areas. Community-based and co-management were the best performing management arrangements for some biological outcomes but require further case studies to verify findings. Investigation of management effects by region indicated that previously degraded reefs received fewer benefits from management implementation than did relatively healthier reefs. For field investigations, the Comoros islands in the Western Indian Ocean served as a model for tropical coral reefs with challenging socioeconomic contexts, high biodiversity, and high vulnerability to coral reef degradation. Empirical study at 21 sites was used to identify the relative effects of natural and anthropogenic threats to coral reefs of the Comoros. Most previous studies of reef health focus on primarily natural factors or a single anthropogenic threat. This study examined suites of natural factors and human activities to identify the relative importance of each on reef health. Human activities including fishing, sand extraction, and beachfront housing and development were the best predictors of reef health status. Most notably, human population and fishing predicted fish richness, abundance, and biomass with seasonal variation in the effects, while site orientation strongly predicted benthic cover. Field studies in the Comoros were also used to investigate the roles of community and state actors in co-management and compare effectiveness of comanagement across sites with varying levels of actor participation. Effective management was found to occur with community or `meta-community' (in this case, a Marine Protected Area in which the efforts of several communities were organized) participation in governance and support of state or external agents, while resilient management that overcame considerable challenges was found to occur only with strong community participation and leadership in governance. External agents were found to contribute to development of meta-community governance structure and initiation of community participation through education and capacity building. The findings from these studies reveal that coral reef management can be improved through context appropriate regulations that address detrimental human activities and through wide acceptance and participation in governance with cooperation among states, communities, and external agents. Close