Interactions among some dominant estuarine nekton species

Interactions between pairs of numerically dominant species collected at inlet and creek shorezone and channel habitats within a high salinity estuary in northeastern South Carolina were examined using two-way contingency tables and binomial tests. Of the significant species interactions, over 71% were positive and these primarily occurred within shorezone habitats. The strongest positive interactions were between young-of-the-year spot (Leiostomus xanthurus) and blue crab (Callinectes sapidus) juveniles in both shorezone habitats, and between striped killifish (Fundulus majalis), white mullet (Mugil curema), and striped anchovies (Anchoa hepsetus) in the inlet shorezone habitat. One of the most positive species associations in channel habitats was between the bay anchovy (Anchoa mitchilli) and the Atlantic brief squid (Lolliguncula brevis). These positive relationships between species may be explained by one species enhancing the habitat for another, both species responding to similar environmental conditions, cooperative social interactions such as mixed schooling, or the attraction of predators to prey. Negative interactions were found between schools of Atlantic silversides (Menidia menidia) and striped killifish in the inlet shorezone and between schools of Atlantic silversides and bay anchovies in the creek shorezone. Schools of Atlantic silversides may either displace or compete with other common shorezone species. Positive and negative interactions suggest that relationships between some species pairs did not occur randomly within certain habitats and may have contributed to the organization of the estuarine nekton community. Differences in the strengths and direction of interactions of certain species pairs among habitats and seasons were probably related to the differences in the physical characteristics of those habitats and/or changes in the relative abundance of dominant species and life stages over time.     

Assessing impacts of climate change on forests: The state of biological modeling

Models that address the impacts of climate change on forests are reviewed at four levels of biological organization: global, regional or landscape, community, and tree. The models are compared for their ability to assess changes in fluxes of biogenic greenhouse gases, land use, patterns of forest type or species composition, forest resource productivity, forest health, biodiversity, and wildlife habitat. No one model can address all of these impacts, but landscape transition models and regional vegetation and land-use models have been used to consider more impacts than the other models. The development of landscape vegetation dynamics models of functional groups is suggested as a means to integrate the theory of both landscape ecology and individual tree responses to climate change. Risk assessment methodologies can be adapted to deal with the impacts of climate change at various spatial and temporal scales. Four areas of research needing additional effort are identified: (1) linking socioeconomic and ecologic models; (2) interfacing forest models at different scales; (3) obtaining data on susceptibility of trees and forest to changes in climate and disturbance regimes; and (4) relating information from different scales.The U.S. Government right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.Managed by Martin Marietta Energy Systems, Inc., for the U.S. Department of Energy under contract DE-AC05-84OR21400.     

How the capacity of bedrock to collect dust and produce soil affects phosphorus bioavailability in the northern Appalachian Mountains of Pennsylvania

More above-ground biomass (kg m⁻²) grows in the northern Appalachian Mountains (USA) in forests on shale than on sandstone at all landscape positions other than ridgetops. This has been tentatively attributed to physical (rather than chemical) attributes of the substrates, such as elevation, particle size, and water capacity. However, shales have generally similar phosphorus (P) concentrations to sandstones and, in the Valley and Ridge province, they erode more quickly. This led us to hypothesize that faster replenishment of the lithogenic nutrient P in shale soils through erosion + soil production could instead control the differences in biomass. To test this, soils and foliage from 10 sites on shales and sandstones in the northern Appalachians from roughly the same elevation and aspect were analysed. We discovered that, when controlling for location, concentrations of bioavailable P in soils and P in foliage were higher and P resorbed from senescing red oak leaves was lower on slower-eroding sandstone than on faster-eroding shale. Lower resorption generally can be attributed to lower P limitation for trees. Further investigation of weathering and erosion on one of the sandstone–shale pairs within a larger, paired watershed study revealed that the differences in P concentrations in biomass and foliage between lithologies likely developed because sandstones act as ‘collectors’ that trap nutrients from residual and exogenous sources, while shales erode quickly and thus promote production of soil from bedrock that releases P to ecosystems. We concluded that the combined effects of differential rates of dust collection and erosion results in roughly equal biomass growing on sandstone and shale ridgetops. This work emphasizes the balance between a landscape's capacity to collect dust versus produce soil in controlling bioavailability of nutrients.     

Perspectives on being a field-based geomorphologist during pregnancy and early motherhood

Many geomorphologists who are mothers find it challenging to balance field research alongside pregnancy and caring for young children. We offer perspectives on the challenges to conducting fieldwork as mothers and possible solutions, as a means of promoting conversations and highlighting issues that are less commonly considered in field-based geomorphic research. Although every mother's experience and needs are different, we discuss strategies for conducting fieldwork, addressing childcare issues, and dealing with financial considerations. We call for our community to support geomorphologists who are pregnant or caring for young children in carrying out fieldwork to help enhance the diversity of voices and perspectives within our discipline.     

Estimation of tree water stress from stem and soil water monitoring with time‐domain reflectometry in two small forested basins in Spain

Soil‐tree water relationships were studied using time domain reflectometry (TDR) in two small forested basins in Spain. The stem water content of two Mediterranean Quercus species (Quercus pyrenaica and Quercus rotundifolia) was measured using previously constructed species‐specific equations. To monitor soil moisture, a TDR station network was used in both cases. Sixteen Q. pyrenaica and six Q. rotundifolia individuals were selected to install two TDR probes in their trunks (at 20 and 120 cm above the ground) to monitor stem water content. Stem and soil water contents were measured fortnightly. The stem water content of both species showed a similar temporal trend for the period studied. A spring maximum (0·654 cm³ cm^?3 for Q. pyrenaica and 0·568 cm³ cm^?3 for Q. rotundifolia) was found to be associated with high transpiration and no soil moisture deficit, and a late‐summer minimum (0·520 cm³ cm^?3 for Q. pyrenaica and 0·426 cm³ cm^?3 for Q. rotundifolia) was associated with the end of the dry season. This drop in stem water content occurs when the available water in the soil decreases. This seasonal difference presumably reflects water withdrawn from stem storage to support the transpirational demands of the tree. Since plant water stress results in reduced stem water content and since this drop can be measured by TDR, it may be concluded that this technology offers a suitable tool for detecting plant water stress. Copyright © 2007 John Wiley & Sons, Ltd.     

Light absorption by phytoplankton,non-algal particles and dissolved organic matter at the Patagonia shelf-break in spring and summer

Satellite image studies and recent in situ sampling have identified conspicuous phytoplankton blooms during spring and summer along the Patagonia shelf-break front. The magnitudes and spectral characteristics of light absorption by total particulate matter (phytoplankton and detritus) and colored dissolved organic matter (CDOM) have been determined by spectrophotometry in that region for spring 2006 and late summer 2007 seasons. In spring, phytoplankton absorption was the dominant optical component of light absorption (60–85%), and CDOM showed variable and important contributions in summer (10–90%). However, there was a lack of correlation between phytoplankton biomass (chlorophyll-a concentration or [chl a]) and the non-algal compartment in both periods. A statistically significant difference was found between the two periods with respect to the CDOM spectral shape parameter (S_cdom), with means of 0.015 (spring) and 0.012 nm^?1 (summer). Nonetheless, the mean S_cdm values, which describe the slope of detritus plus CDOM spectra, did not differ between the periods (average of 0.013 nm^?1). Phytoplankton absorption values in this work showed deviations from mean parameterizations in previous studies, with respect to [chl a], as well as between the two study periods. In spring, despite the microplankton dominance, high specific absorption values and large dispersion were found (a*_ph(440)=0.04±0.03 m² mg [chl a]^?1), which could be attributed to an important influence of photo-protector accessory pigments. In summer, deviations from general trends, with values of a*_ph(440) even higher (0.09±0.02 m² mg [chl a]^?1), were due to the dominance of small cell sizes and also to accessory pigments. These results highlight the difficulty in deriving robust relationships between chlorophyll concentration and phytoplankton absorption coefficients regardless of the season period. The validity of a size parameter (S_f) derived from the absorption spectra has been demonstrated and was shown to describe the size structure of phytoplankton populations, independently of pigment concentration, with mean values of 0.41 in spring and 0.72 in summer. Our results emphasize the need for specific parameterization for the study region and seasonal sampling approach in order to model the inherent optical properties from water reflectance signatures.     

Amazon Fan biomarker evidence against the Pleistocene rainforest refuge hypothesis?

Ocean Drilling Program Leg 155 Site 942 on the Amazon Fan is an ideal location for monitoring palaeoclimatic changes within a significant proportion of the Amazon Basin. We present n‐alkane δ¹³C and taraxerol and laevoglucosan concentration records from this site covering the last 38 ka. The entire n‐alkane δ¹³C record is constrained between ?31‰ and ?34‰, which is well within the isotopic range occupied by C₃ vegetation. The concentration and relative abundance of taraxerol, a mangrove indicator, varies by over an order of magnitude, but seems to have had no effect on the n‐alkane δ¹³C record. The laevoglucosan concentrations are extremely low during the last glacial period, suggesting a relatively low occurrence of forest fires. Laevoglucosan concentrations are highest between 13.5 and 12.5 ka, suggesting an increased incidence of Amazon forest fires at the very end of the Younger Dryas. These records, combined with previously published pollen records from Site 932, reveal no evidence for massive incursions of grasslands into Amazonia during the last glacial period, despite evidence of reduced outflow of the Amazon River indicating more arid conditions. We therefore suggest that savannah encroachment, as proposed by the Pleistocene refuge hypothesis, can be refuted as an explanation for high species endemism within the Amazon Basin, and alternative explanations are required. Copyright © 2012 John Wiley & Sons, Ltd.     

Gap analysis on open data interconnectivity for disaster risk research

Open data strategies are being adopted in disaster-related data particularly because of the need to provide information on global targets and indicators for implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030. In all phases of disaster risk management including forecasting, emergency response and post-disaster reconstruction, the need for interconnected multidisciplinary open data for collaborative reporting as well as study and analysis are apparent, in order to determine disaster impact data in timely and reportable manner. The extraordinary progress in computing and information technology in the past decade, such as broad local and wide-area network connectivity (e.g. Internet), high-performance computing, service and cloud computing, big data methods and mobile devices, provides the technical foundation for connecting open data to support disaster risk research. A new generation of disaster data infrastructure based on interconnected open data is evolving rapidly. There are two levels in the conceptual model of Linked Open Data for Global Disaster Risk Research (LODGD) Working Group of the Committee on Data for Science and Technology (CODATA), which is the Committee on Data of the International Council for Science (ICSU): data characterization and data connection. In data characterization, the knowledge about disaster taxonomy and data dependency on disaster events requires specific scientific study as it aims to understand and present the correlation between specific disaster events and scientific data through the integration of literature analysis and semantic knowledge discovery. Data connection concepts deal with technical methods to connect distributed data resources identified by data characterization of disaster type. In the science community, interconnected open data for disaster risk impact assessment are beginning to influence how disaster data are shared, and this will need to extend data coverage and provide better ways of utilizing data across domains where innovation and integration are now necessarily needed.