Nutrient availability and herbivory can regulate primary production in ecosystems, but little is known about how, or whether, they may interact with one another. Here, we investigate how nitrogen availability and insect herbivory interact to alter aboveground and belowground plant community biomass in an old-field ecosystem. In 2004, we established 36 experimental plots in which we manipulated soil nitrogen (N) availability and insect abundance in a completely randomized plot design. In 2009, after 6 years of treatments, we measured aboveground biomass and assessed root production at peak growth. Overall, we found a significant effect of reduced soil N availability on aboveground biomass and belowground plant biomass production. Specifically, responses of aboveground and belowground community biomass to nutrients were driven by reductions in soil N, but not additions, indicating that soil N may not be limiting primary production in this ecosystem. Insects reduced the aboveground biomass of subdominant plant species and decreased coarse root production. We found no statistical interactions between N availability and insect herbivory for any response variable. Overall, the results of 6 years of nutrient manipulations and insect removals suggest strong bottom-up influences on total plant community productivity but more subtle effects of insect herbivores on aspects of aboveground and belowground production.
Background: Abiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are also influenced by regional factors such as immigration and colonization. We used three years of monthly treehole census data to evaluate the relative influence of local and regional factors on our study system.
The effects of predation on water-filled treehole communities in North Carolina were examined using mesocosm experiments and observations in natural treeholes. The presence of the predator Toxorhynchites rutilus and leaf litter abundance were manipulated in mesocosms to examine interactions between resources and predation. Long-term examination of interactions in unmanipulated treeholes provided data on natural variation in water volume and predator density. Toxorhynchites rutilus preys upon two common treehole insects, Aedes triseriatus and Culicoides guttipennis. We predicted that T. rutilus would act as a keystone predator and reduce the density of these dominant species. This would allow other species to coexist and lead to an increase in diversity. We also predicted that effects of predation would be reduced in habitats with high levels of resources, due to either increased refugia or decreased competition. The results did not entirely support the predictions. In both mesocosms and treeholes T. rutilus depressed densities of the most abundant prey type, A. triseriatus. In treeholes, the presence of T. rutilus depressed densities of the midge C. guttipennis, and predator densities were positively associated with insect diversity in treeholes. Strikingly, higher diversity was also associated with high densities of the dominant prey in treeholes. In addition, mesocosms showed no relationship between T. rutilus presence and species diversity. The relationship between the predator and diversity in treeholes appears to be unrelated to predation on the dominant competitors and is instead caused by some other habitat characteristic. While there were effects of resources on densities and diversity in both mesocosms and treeholes, neither of the resources analyzed, leaf litter or water, appear to be the sole characteristic that mutually allows for large populations of T. rutilus and high species diversity. We conclude that though T. rutilus is an aggressive predator, it does not cause an increase in prey species diversity as a keystone predator would. Further research is needed to determine the conditions that favor the presence of predator and high prey diversity.
There is no doubt we live in an era of change. The real question is how we as individuals will shape our future. Moreover, how will educational institutions go on to influence the development of these ideas? Some individuals and institutions have formed a united front of environmental consciousness and sustainability, but other well-established institutions resist deviation from the direction that once brought them success. This summary explains how students of the ecological community intend to interact with the science and society of this ubiquitous change. Students from across the nation convened at the Sevilletta Long-Term Ecological Research station for the 4th Annual Strategies for Ecology, Education, Development and Sustainability (SEEDS) leadership meeting with three objectives:
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.