Stream ecosystem responses to an extreme rainfall event across multiple catchments in southeast Alaska

Floods are a key component of the flow regime of many rivers and a major structuring force of stream communities. Climate change is predicted to increase the frequency of extreme rainfall (i.e. return intervals > 100 years) leading to extensive flooding, but the ecological effects of such events are not well understood. Comparative studies of flood impacts are scarce, despite the clear need to understand the potentially contingent responses of multiple independent stream systems to extreme weather occurring at meso- and synoptic spatial scales. We describe the effect of an extreme rainfall event affecting an area >100,000 km2 that caused extensive flooding in SE Alaska. Responses of channel morphology and three key biological groups (meiofauna, macroinvertebrates and fish) were assessed in four separate and recently deglaciated stream catchments of contrasting age (38-180 years) by comparing samples taken before and after the event. Ecological responses to the rainfall and subsequent flooding differed markedly across the four catchments in response to variations in rainfall intensity and to factors such as channel morphology, stream sediment composition and catchment vegetation type and cover, which were themselves related to stream age. Our study demonstrates the value of considering multiple response variables when assessing the effects of extreme events, and highlights the potential for contrasting biological responses to extreme events across catchments. We advocate more comparative studies to understand how extreme rainfall and flooding affects ecosystem responses across multiple catchments

Substrate age and tree islands influence carbon and nitrogen dynamics across a retrogressive semiarid chronosequence

The long-term dynamics of carbon (C) and nitrogen (N) in semiarid ecosystems remain poorly understood. We measured pools and fluxes of surface soil C and N, as well as other soil properties, under tree canopies and in intercanopy spaces at four sites that form a volcanic substrate age gradient in semiarid piñon-juniper woodlands of northern Arizona, United States. Clay content and soil water-holding capacity increased consistently with substrate age, but both soil organic C and N increased only up to the 750,000 year site and then declined at the oldest (3,000,000 year) site. Measures of soil C and N flux displayed a similar pattern to total C and N pools. Pools and fluxes of C and N among the three canopy types became more homogeneous with substrate age up to the 750,000 year site, but disparity between tree and intercanopy microsites widened again at the oldest site. The δ15N of both tree leaves and surface soils became progressively more enriched across the substrate age gradient, consistent with a N cycle increasingly dominated by isotope fractionating losses. Our results point to consistencies in patterns of ecosystem development between semiarid and more humid ecosystems and suggest that pedogenic development may be an important factor controlling the spatial distribution of soil resources in semiarid ecosystems. These data should help both unify and broaden current theory of terrestrial ecosystem development

The Second SIMBIOS Radiometric Intercomparison (SIMRIC-2), March-November 2002

The second SIMBIOS (Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies) Radiometric Intercomparison (SIMRIC-2) was carried out in 2002. The purpose of the SIMRIC's was to ensure a common radiometric scale among the calibration facilities that are engaged in calibrating in-situ radiometrics used for ocean color-related research and to document the calibration procedures and protocols. The SeaWIFS Transfer Radiometer (SXR-II) measured the calibration radiances at six wavelengths from 411nm to 777nm in the ten laboratories participating in the SIMRIC-2. The measured radiances were compared with the radiances expected by the laboratories. The agreement was within the combined uncertainties for all but two laboratories. Likely error sources were identified in these laboratories and corrective measures were implemented. NIST calibrations in December 2001 and January 2003 showed changes ranging from -0.6% to +0.7% for the six SXR-II channels. Two independent light sources were used to monitor changes in the SXR-II responsivity between the NIST calibrations. A 2% variation of the responsivity of channel 1 of the SXR-II was detected, and the SXR-II responsivity was corrected using the monitoring data. This report also compared directional reflectance calibrations of a Spectralon plaque by different calibration facilitie

Nutrient Enrichment Increases Mortality of Mangroves

Nutrient enrichment of the coastal zone places intense pressure on marine communities. Previous studies have shown that growth of intertidal mangrove forests is accelerated with enhanced nutrient availability. However, nutrient enrichment favours growth of shoots relative to roots, thus enhancing growth rates but increasing vulnerability to environmental stresses that adversely affect plant water relations. Two such stresses are high salinity and low humidity, both of which require greater investment in roots to meet the demands for water by the shoots. Here we present data from a global network of sites that documents enhanced mortality of mangroves with experimental nutrient enrichment at sites where high sediment salinity was coincident with low rainfall and low humidity. Thus the benefits of increased mangrove growth in response to coastal eutrophication is offset by the costs of decreased resilience due to mortality during drought, with mortality increasing with soil water salinity along climatic gradients

The disappearing cryosphere : impacts and ecosystem responses to rapid cryosphere loss

Author Posting. © American Institute of Biological Sciences, 2012. This article is posted here by permission of American Institute of Biological Sciences for personal use, not for redistribution. The definitive version was published in BioScience 62 (2012): 405-415, doi:10.1525/bio.2012.62.4.11.The cryosphere—the portion of the Earth's surface where water is in solid form for at least one month of the year—has been shrinking in response to climate warming. The extents of sea ice, snow, and glaciers, for example, have been decreasing. In response, the ecosystems within the cryosphere and those that depend on the cryosphere have been changing. We identify two principal aspects of ecosystem-level responses to cryosphere loss: (1) trophodynamic alterations resulting from the loss of habitat and species loss or replacement and (2) changes in the rates and mechanisms of biogeochemical storage and cycling of carbon and nutrients, caused by changes in physical forcings or ecological community functioning. These changes affect biota in positive or negative ways, depending on how they interact with the cryosphere. The important outcome, however, is the change and the response the human social system (infrastructure, food, water, recreation) will have to that change.The authors wish to thank the funding provided by the National Science Foundation’s (NSF) Long Term Ecological Research (LTER) Network for supporting our long-term studies, in which we track the ecosystem response to the disappearing cryosphere. NSF LTER Site Grants OPP 0823101, OPP 1115245, DEB 1114804, DEB-1026415, DEB-0620579, and DEB-1027341 supported the authors during the preparation of this article.2012-10-0

The role of fishing material culture in communities’ sense of place as an added-value in management of coastal areas

Fishing communities in many places around the world are facing significant challenges due to new policies and environmental developments. While it is imperative to ensure sustainability of natural resources, many policies may overlook the contribution of fisheries to the sociocultural well-being of coastal communities. Authors address the problem of valuing the sociocultural benefits of fishing by exploring the role of fishing landscapes and traditional working waterfronts in maintaining sense of place in fishing communities. The paper explores how sense of place contributes to understanding the relationship between fishing and cultural-ecosystem services, drawing on case studies from four U.S. fishing communities in Brunswick County, North Carolina. Through semi-structured and in-depth interviews with fishing communities members, resident photography and sites visits, this paper outlines how fishing contributes to sense of place in terms of placeattachment and cultural-social memory. By understanding the relationship between fishers’ sense of place, and the physical environment in fishing communities in Brunswick County, the authors identify the complexity and interrelated elements that shape the relationship between fishermen and their cultural landscape. The paper suggests that realizing the value of fishing cultural landscape can encourage policies that promote preservation of fishing cultural heritage for the sociocultural benefit of communitie

Darwin Core: An Evolving Community-Developed Biodiversity Data Standard

Biodiversity data derive from myriad sources stored in various formats on many distinct hardware and software platforms. An essential step towards understanding global patterns of biodiversity is to provide a standardized view of these heterogeneous data sources to improve interoperability. Fundamental to this advance are definitions of common terms. This paper describes the evolution and development of Darwin Core, a data standard for publishing and integrating biodiversity information. We focus on the categories of terms that define the standard, differences between simple and relational Darwin Core, how the standard has been implemented, and the community processes that are essential for maintenance and growth of the standard. We present case-study extensions of the Darwin Core into new research communities, including metagenomics and genetic resources. We close by showing how Darwin Core records are integrated to create new knowledge products documenting species distributions and changes due to environmental perturbations

Projected Loss of a Salamander Diversity Hotspot as a Consequence of Projected Global Climate Change

Background: Significant shifts in climate are considered a threat to plants and animals with significant physiological limitations and limited dispersal abilities. The southern Appalachian Mountains are a global hotspot for plethodontid salamander diversity. Plethodontids are lungless ectotherms, so their ecology is strongly governed by temperature and precipitation. Many plethodontid species in southern Appalachia exist in high elevation habitats that may be at or near their thermal maxima, and may also have limited dispersal abilities across warmer valley bottoms. Methodology/Principal Findings: We used a maximum-entropy approach (program Maxent) to model the suitable climatic habitat of 41 plethodontid salamander species inhabiting the Appalachian Highlands region (33 individual species and eight species included within two species complexes). We evaluated the relative change in suitable climatic habitat for these species in the Appalachian Highlands from the current climate to the years 2020, 2050, and 2080, using both the HADCM3 and the CGCM3 models, each under low and high CO 2 scenarios, and using two-model thresholds levels (relative suitability thresholds for determining suitable/unsuitable range), for a total of 8 scenarios per species. Conclusion/Significance: While models differed slightly, every scenario projected significant declines in suitable habitat within the Appalachian Highlands as early as 2020. Species with more southern ranges and with smaller ranges had larger projected habitat loss. Despite significant differences in projected precipitation changes to the region, projections did no

The JCMT Gould Belt Survey: constraints on prestellar core properties in Orion A North

We employ SCUBA-2 (Submillimetre Common-User Bolometer Array 2) observations of the Orion A North molecular cloud to derive column density and temperature maps. We apply a novel, Hessian-based structural identification algorithm for detection of prestellar cores to these data, allowing for automated generation of the prestellar mass function. The resulting mass function is observed to peak at $1.39^{+0.18}_{{-}0.19} M_{\odot}$, indicating a star-forming efficiency lower limit of ∼14 per cent when compared with the Orion nebula Cluster initial mass function (IMF) peak. Additionally, the prestellar mass function is observed to decay with a high-mass powerlaw exponent $\alpha = 2.53^{+0.16}_{{-}0.14}$, indicating approximate functional similarity with the Salpeter IMF ($\alpha = 2.35$). This result, when combined with the results of previous investigations suggests a regional dependence of the star-forming efficiency

Tamm Review: On the nature of the nitrogen limitation to plant growth in Fennoscandian boreal forests

The supply of nitrogen commonly limits plant production in boreal forests and also affects species composition and ecosystem functions other than plant growth. These interrelations vary across the landscapes, with the highest N availability, plant growth and plant species richness in ground-water discharge areas (GDAs), typically in toe-slope positions, which receive solutes leaching from the much larger groundwater recharge areas (GRAs) uphill. Plant N sources include not only inorganic N, but, as heightened more recently, also organic N species. In general, also the ratio inorganic N over organic N sources increase down hillslopes. Here, we review recent evidence about the nature of the N limitation and its variations in Fennoscandian boreal forests and discuss its implications for forest ecology and management. The rate of litter decomposition has traditionally been seen as the determinant of the rate of N supply. However, while N-rich litter decomposes faster than N-poor litter initially, N-rich litter then decomposes more slowly, which means that the relation between N % of litter and its decomposability is complex. Moreover, in the lower part of the mor-layer, where the most superficial mycorrhizal roots first appear, and N availability matters for plants, the ratio of microbial N over total soil N is remarkably constant over the wide range in litter and soil C/N ratios of between 15 and 40 for N-rich and N-poor sites, respectively. Nitrogen-rich and -poor sites thus differ in the sizes of the total N pool and the microbial N pool, but not in the ratio between them. A more important difference is that the soil microbial N pool turns over faster in N-rich systems because the microbes are more limited by C, while microbes in N-poor systems are a stronger sink for available N. Furthermore, litter decomposition in the most superficial soil horizon (as studied by the so-called litter-bag method) is associated with a dominance of saprotrophic fungi, and absence of mycorrhizal fungi. The focal zone in the context of plant N supply in N-limited forests is further down the soil profile, where ectomycorrhizal (ECM) roots become abundant. Molecular evidence and stable isotope data indicate that in the typical N-poor boreal forests, nitrogen is retained in saprotrophic fungi, likely until they run out of energy (available C-compounds). Then, as heightened by recent research, ECM fungi, which are supplied by photosynthate from the trees, become the superior competitors for N. In N-poor boreal soils strong N retention by microorganisms keeps levels of available N very low. This is exacerbated by an increase in tree C allocation to mycorrhizal fungi (TCAM) relative to net primary production (NPP) with decreasing soil N supply, which causes ECM fungi to retain much of the available soil N for their own growth and transfer little to their tree hosts. The transfer of N through the ECM fungi, and not the rate of litter decomposition, is likely limiting the rate of tree N supply under such conditions. All but a few stress-tolerant less N-demanding plant species, like the ECM trees themselves and ericaceous dwarf shrubs, are excluded. With increasing N supply, a weakening of ECM symbiosis caused by the relative decline in TCAM contributes to shifts in soil microbial community composition from fungal dominance to bacterial dominance. Thus, bacteria, which are less C-demanding, but more likely to release N than fungi, take over. This, and the relatively high pH in GDA, allow autotrophic nitrifying bacteria to compete successfully for the NH4+ released by C-limited organisms and causes the N cycle to open up with leaching of nitrate (NO3−) and gaseous N losses through denitrification. These N-rich conditions allow species-rich communities of N-demanding plant species. Meanwhile, ECM fungi have a smaller biomass, are supplied with N in excess of their demand and will export more N to their host trees. Hence, the gradient from low to high N supply is characterized by profound variations in plant and soil microbial physiologies, especially their relations to the C-to-N supply ratio. We propose how interactions among functional groups can be understood and modelled (the plant-microbe carbon-nitrogen model). With regard to forest management these perspectives explain why the creation of larger tree-free gaps favors the regeneration of tree seedlings under N-limited conditions through reduced belowground competition for N, and why such gaps are less important under high N supply (but when light might be limiting). We also discuss perspectives on the relations between N supply, biodiversity, and eutrophication of boreal forests from N deposition or forest fertilization