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"Calhoun, Aram J. K"
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Do geographically isolated wetlands influence landscape functions?
Geographically isolated wetlands (GIWs), those surrounded by uplands, exchange materials, energy, and organisms with other elements in hydrological and habitat networks, contributing to landscape functions, such as flow generation, nutrient and sediment retention, and biodiversity support. GIWs constitute most of the wetlands in many North American landscapes, provide a disproportionately large fraction of wetland edges where many functions are enhanced, and form complexes with other water bodies to create spatial and temporal heterogeneity in the timing, flow paths, and magnitude of network connectivity. These attributes signal a critical role for GIWs in sustaining a portfolio of landscape functions, but legal protections remain weak despite preferential loss from many landscapes. GIWs lack persistent surface water connections, but this condition does not imply the absence of hydrological, biogeochemical, and biological exchanges with nearby and downstream waters. Although hydrological and biogeochemical connectivity is often episodic or slow (e.g., via groundwater), hydrologic continuity and limited evaporative solute enrichment suggest both flow generation and solute and sediment retention. Similarly, whereas biological connectivity usually requires overland dispersal, numerous organisms, including many rare or threatened species, use both GIWs and downstream waters at different times or life stages, suggesting that GIWs are critical elements of landscape habitat mosaics. Indeed, weaker hydrologic connectivity with downstream waters and constrained biological connectivity with other landscape elements are precisely what enhances some GIW functions and enables others. Based on analysis of wetland geography and synthesis of wetland functions, we argue that sustaining landscape functions requires conserving the entire continuum of wetland connectivity, including GIWs.
Journal Article
Biogeochemical Hotspots in Forested Landscapes: The Role of Vernal Pools in Denitrification and Organic Matter Processing
Quantifying spatial and temporal heterogeneity in ecosystem processes presents a challenge for conserving ecosystem function across landscapes. In particular, many ecosystems contain small features that play larger roles in ecosystem processes than their size would indicate; thus, they may represent “hotspots” of activity relative to their surroundings. Biogeochemical hotspots are characterized as small features within a landscape that show comparatively high chemical reaction rates. In northeastern forests in North America, vernal pools are abundant, small features that typically fill in spring with snow melt and precipitation and dry by the end of summer. Ephemeral flooding alters soil moisture and the depth of the soil’s oxic/anoxic boundary, which may affect biogeochemical processes. We studied the effects of vernal pools on leaf-litter decomposition rates, soil enzyme activity, and denitrification in vernal pools to assess whether they function as biogeochemical hotspots. Our results indicate that seasonal inundation enhanced leaf-litter decomposition, denitrification, and enzyme activity in vernal pools relative to adjacent forest sites. Leaves in seasonally flooded areas decomposed faster than leaves in terra firme forest sites. Flooding also influenced the C, N, and P stoichiometry of decomposing leaf litter and explained the variance in microbial extracellular enzyme activity for phosphatase, β-D-glucosidase, and β-N-acetylglucosaminidase. Additionally, denitrification rates were enhanced by seasonal flooding across all of the study pools. Collectively, these data suggest that vernal pool ecosystems may function as hotspots of leaf-litter decomposition and denitrification and play a significant role in decomposition and nutrient dynamics relative to their size.
Journal Article
The Maine Vernal Pool Mapping and Assessment Program: Engaging Municipal Officials and Private Landowners in Community-Based Citizen Science
The Vernal Pool Mapping and Assessment Program (VPMAP) was initiated in 2007 to create a vernal pool database as a planning tool to foster local compliance with new state vernal pool regulations. In the northeastern United States, vernal pools are seasonal wetlands that provide critical breeding habitat for a number of amphibians and invertebrates and provide important resting and foraging habitat for some rare and endangered state-listed species. Using participant observation, interviews, and focus groups, we examined the engagement of municipal officials and private landowners in VPMAP. Important outcomes of municipal and landowner engagement included mobilization of town support for proactive planning, improved awareness and understanding of vernal pools, and increased interactions between program coordinators, municipal officials, and private landowners. Challenges to municipal and landowner engagement included an inconsistency in expectations between coordinators and municipal officials and a lack of time and sufficient information for follow-up with landowners participating in VPMAP. Our study highlights the importance of developing relationships among coordinators, municipal officials, and private landowners in facilitating positive outcomes for all stakeholders and for effective resource management. We suggest an expanded citizen science model that focuses on improving two-way communication among project coordinators, municipal officials, and local citizens and places communication with private landowners on par with volunteer citizen scientist recruitment and field training. Lessons learned from this research can inform the design and implementation of citizen science projects on private land.
Journal Article
Postbreeding Habitat Use of the Rare, Pure-Diploid Blue-spotted Salamander (Ambystoma laterale)
The pure-diploid Blue-spotted Salamander (Ambystoma laterale) is among the rarest amphibians in northeastern North America, and data on its ecology are sparse. We assessed the movement ecology and terrestrial habitat use of A. laterale using radio- and passive integrated transponder (PIT) tag- telemetry. We radio-tracked 22 A. laterale for a median of 54 days (range 6–126 days) in the spring and summer of 2009 and 2010. Using a modified PIT tag reader, we conducted 34 in situ surveys during the spring and summer of 2009 through 2011, resulting in 42 relocations. We detected salamanders at a median straight-line distance of 67 m (range 7–281 m) from their breeding wetland. The life zone (i.e., critical terrestrial habitat), encompassing 95% of observed salamander movements, extended 152 m from the edge of the breeding wetland. Eighteen radio-tracked salamanders migrated to upland forest, three to a wet meadow, and one to a red maple (Acer rubrum) swamp. Salamanders used upland forest and wet meadow more often than the availabilities of those habitats would predict. We recorded habitat data at 10-m and 1-m-diameter circular plots centered on animal locations. At the 10-m scale, salamander presence was correlated positively with percent cover of slash and correlated negatively with percent cover of grass, total basal area of trees, and relative humidity. At the 1-m scale, salamander locations had deeper leaf litter and moister soil than did random locations. Our results suggest existing, published recommendations for the conservation of vernal pool species are applicable to A. laterale.
Journal Article
Geographically Isolated Wetlands: Rethinking a Misnomer
We explore the category “geographically isolated wetlands” (GIWs; i.e., wetlands completely surrounded by uplands at the local scale) as used in the wetland sciences. As currently used, the GIW category (1) hampers scientific efforts by obscuring important hydrological and ecological differences among multiple wetland functional types, (2) aggregates wetlands in a manner not reflective of regulatory and management information needs, (3) implies wetlands so described are in some way “isolated,” an often incorrect implication, (4) is inconsistent with more broadly used and accepted concepts of “geographic isolation,” and (5) has injected unnecessary confusion into scientific investigations and discussions. Instead, we suggest other wetland classification systems offer more informative alternatives. For example, hydrogeomorphic (HGM) classes based on well-established scientific definitions account for wetland functional diversity thereby facilitating explorations into questions of connectivity without an a priori designation of “isolation.” Additionally, an HGM-type approach could be used in combination with terms reflective of current regulatory or policymaking needs. For those rare cases in which the condition of being surrounded by uplands is the relevant distinguishing characteristic, use of terminology that does not unnecessarily imply isolation (e.g., “upland embedded wetlands”) would help alleviate much confusion caused by the “geographically isolated wetlands” misnomer.
Journal Article
Efficiency and Detection Accuracy Using Print and Digital Stereo Aerial Photography for Remotely Mapping Vernal Pools in New England Landscapes
Aerial imagery has been used to identify potential vernal pools (PVPs) using stereo photographic prints. Stereoplotter photogrammetry now allows digital aerial images to be viewed in stereo (3-Dimensional) to enhance remote sensing capabilities. We used both print and digital imagery to map PVPs in 10 towns in Maine, USA. We used field verification of 771 PVPs to explore efficiency and accuracy of the two methodologies and to determine effects of pool size and land cover on accuracy. We compared known pool locations with National Wetland Inventory (NWI) data. The stereoplotter was more efficient and easier to use than prints. In the towns where print imagery was used, 77.4 % of surveyed PVPs were confirmed as compared to 60.8 % of PVPs surveyed in the towns with digital photography. The higher commission errors using the digital method were likely due to enhanced ability to detect smaller features. Omission errors were common using both print and digital methods. Only 43 % of confirmed vernal pools were located in areas mapped by NWI, suggesting that NWI information does not improve detection accuracy. Aerial photo interpretation continues to be effective for PVP identification in our region and is improved with the use of digital stereoplotters.
Journal Article
Citizen science and natural resource governance
Effective natural resource policy depends on knowing what is needed to sustain a resource and building the capacity to identify, develop, and implement flexible policies. This retrospective case study applies resilience concepts to a 16-year citizen science program and vernal pool regulatory development process in Maine, USA. We describe how citizen science improved adaptive capacities for innovative and effective policies to regulate vernal pools. We identified two core program elements that allowed people to act within narrow windows of opportunity for policy transformation, including (1) the simultaneous generation of useful, credible scientific knowledge and construction of networks among diverse institutions, and (2) the formation of diverse leadership that promoted individual and collective abilities to identify problems and propose policy solutions. If citizen science program leaders want to promote social-ecological systems resilience and natural resource policies as outcomes, we recommend they create a system for internal project evaluation, publish scientific studies using citizen science data, pursue resources for program sustainability, and plan for leadership diversity and informal networks to foster adaptive governance.
Journal Article
Localism “Reimagined”: Building a Robust Localist Paradigm for Overcoming Emerging Conservation Challenges
Governance gaps at both the federal and state level increasingly necessitate local action and remain a key driver of community-based solutions. A localist paradigm—encompassing models such as community-based management, citizen science, and cooperative research—offers a promising approach for bridging governance gaps by engaging citizens, co-producing knowledge, fostering trust, and developing innovative solutions to address complex conservation challenges. Yet, despite notable successes, significant barriers constrain widespread implementation of localist approaches. This is particularly evident in natural resource-dependent communities. Rural communities are increasingly faced with a range of conservation challenges related to rapid climate and land-use changes but often they lack the capacity to support locally based initiatives to better anticipate, plan for, and mitigate these changes. We examined four diverse conservation cases based on localist approaches in Maine, USA, to bring to the fore key factors that influence outcomes in different social-ecological contexts. We compared cases along three frequently discussed dimensions—governance systems, social adaptive capacities, and technology and data characteristics and found that localist outcomes vary widely depending on key metrics within each of these dimensions. There is no single way to advance localism, but we offer multiple ways to incorporate a community-based perspective into management. This synthesis of data from our collective participatory research projects provides guidance to maximize the potential of localist conservation approaches in complex social and biophysical arenas.
Journal Article
Effects of Timber Harvest on Amphibian Populations: Understanding Mechanisms from Forest Experiments
Harvesting timber is a common form of land use that has the potential to cause declines in amphibian populations. It is essential to understand the behavior and fate of individuals and the resulting consequences for vital rates (birth, death, immigration, emigration) under different forest management conditions. We report on experimental studies conducted in three regions of the United States to identify mechanisms of responses by pond-breeding amphibians to timber harvest treatments. Our studies demonstrate that life stages related to oviposition and larval performance in the aquatic stage are sometimes affected positively by clearcutting, whereas effects on juvenile and adult terrestrial stages are mostly negative. Partial harvest treatments produced both positive and weaker negative responses than clearcut treatments. Mitigating the detrimental effects of canopy removal, higher surface temperature, and loss of soil-litter moisture in terrestrial habitats surrounding breeding ponds is critical to maintaining viable amphibian populations in managed forested landscapes.
Journal Article