Model of stomatal ammonia compensation point (STAMP) in relation to the plant nitrogen and carbon metabolisms and environmental conditions

Agricultural crops can be either a source or a sink of ammonia (NH₃). Most NH₃ exchange models developed so far do not account for the plants nitrogen (N) metabolism and use prescribed compensation points. We present here a leaf-scale simplified NH₃ stomatal compensation point model related to the plants N and carbon (C) metabolisms, for C₃ plants. Five compartments are considered: xylem, cytoplasm, apoplasm, vacuole and sub-stomatal cavity. The main processes accounted for are the transport of ammonium (NH₄⁺), NH₃ and nitrate (NO₃⁻) between the different compartments, NH₄⁺ production through photorespiration and NO₃⁻ reduction, NH₄⁺ assimilation, chemical and thermodynamic equilibriums in all the compartments, and stomatal transfer of NH₃.The simulated compensation point is sensitive to paramaters related to the apoplastic compartment: pH, volume and active transport rate. Determining factors are leaf temperature, stomatal conductance and NH₄⁺ flux to the leaf. Atmospheric NH₃ concentration seem to have very little effect on the compensation point in conditions of high N fertilization. Comparison of model outputs to experimental results show that the model underestimates the NH₃ compensation point for high N fertilization and that a better parametrisation of sensitive parameters especially active trasport rate of NH₄⁺ may be required.     

Lack of interspecific parasitism between the dwarf honeybees Apis andreniformis and Apis florea

The dwarf honeybees Apis florea and Apis andreniformis are sympatric in Southeast Asia. We examined undisturbed nests of both species finding that heterospecific workers are present in some nests at low frequency. This suggested that workers may enter heterospecific nests as a prelude to reproductive parasitism. To test this hypothesis, we created mixed-species colonies and determined the reproductive response of workers within them based on molecular markers. In queenless colonies, workers of both species activated their ovaries at equal frequency. However, the majority species, A. florea, had complete reproductive dominance over A. andreniformis, most likely because the A. florea workers recognised and removed heterospecific larvae. In queenright mixed-species colonies, workers responded to heterospecific signals of the presence of the queen and did not activate their ovaries. Thus, despite predictions from kin selection theory that workers would benefit from parasitising heterospecific nests, we find no evidence that selection has established a parasitic strategy in these sibling species.     

HOW CLIMATE UNCERTAINTY SHOULD BE INCLUDED IN GREAT LAKES MANAGEMENT: MODELING WORKSHOP RESULTS1

ABSTRACT: In two workshops, we evaluated decision analysis methods for comparing Lake Erie levels management alternatives under climate change uncertainty. In particular, we wanted to see how acceptable and effective those methods could be in a public planning setting. The methods evaluated included simulation modeling, scenario analysis, decision trees and structured group discussions. We evaluated the methods by interviewing the workshop participants before and after the workshops. The participants, who were experienced Great Lakes water resources managers, concluded that simulation modeling is user-friendly enough to enable scenario analysis even in workshop settings for large public planning studies. They felt that simulation modeling can improve not only understanding of the system, but also of the options for managing it. Scenario analysis revealed that the decision for the case study, Lake Erie water level regulation, could be altered by the likelihood of climate change. The participants also recommended that structured group discussions be used in public planning settings to elicit ideas and opinions. On the other hand, the participants were less optimistic about decision trees because they felt that the public might view subjective probabilities as difficult to understand and subject to manipulation.     

PRECIPITATION DIFFERENCES AMONGST GCMs USED FOR THE U.S. NATIONAL ASSESSMENT1

ABSTRACT: Two general circulation models (GCMs) used in the U.S. national assessment of the potential consequences of climate variability and change (CGCM1 and HadCM2) show a large increase in precipitation in the future over the southwestern U.S., particularly during winter. This precipitation increase is an extension of a larger region of increased precipitation in the Pacific Ocean off the west coast of North America that is associated with a deepened and southward-shifted Aleutian Low, a weaker subtropical high, and warmer sea surface temperatures (SSTs). The models differ in their simulation of precipitation anomalies over the southeastern U.S., with CGCM1 showing drier conditions and HadCM2 showing wetter conditions in the future. While both models show decreased frequency of Atlantic storms, consistent with decreased meridional and land/sea temperature gradients, the more coastal position of the storm track in CGCM1 results in less precipitation than modern along the eastern seaboard of the U.S. During summer, differences in land surface models within the two GCMs sometimes lead to differences in soil moisture that feed back to the precipitation over land due to available moisture.     

Use of carrion fly iDNA metabarcoding to monitor invasive and native mammals

Severely fragmented habitats increase the risk of extirpation of native mammal populations through isolation, increased edge effects, and predation. Therefore, monitoring the movement of mammal populations through anthropogenically altered landscapes can inform conservation. We used metabarcoding of invertebrate-derived DNA (iDNA) from carrion flies (Calliphoridae and Sarcophagidae) to track mammal populations in the wheat belt of southwestern Australia, where widespread clearing for agriculture has removed most of the native perennial vegetation and replaced it with an agricultural system. We investigated whether the localization of the iDNA signal reflected the predicted distribution of 4 native species—echidna (Tachyglossus aculeatus), numbat (Myrmecobius fasciatus), woylie (Bettongia penicillata), and chuditch (Dasyurus geoffroii)—and 2 non-native, invasive mammal species—fox (Vulpes vulpes) and feral cat (Felis catus). We collected bulk iDNA samples (n = 150 samples from 3428 carrion flies) at 3 time points from 3 conservation reserves and 35 road edges between them. We detected 14 of the 40 mammal species known from the region, including our target species. Most detections of target taxa were in conservation reserves. There were a few detections from road edges. We detected foxes and feral cats throughout the study area, including all conservation reserves. There was a significant difference between the diversity (F_3, 98 = 5.91, p < 0.001) and composition (F_3, 43 = 1.72, p < 0.01) of taxa detections on road edges and conservation reserves. Conservation reserves hosted more native biodiversity than road edges. Our results suggest that the signals from iDNA reflect the known distribution of target mammals in this region. The development of iDNA methods shows promise for future noninvasive monitoring of mammals. With further development, iDNA metabarcoding could inform decision-making related to conservation of endangered taxa, invasive species management, and impacts of habitat fragmentation.     

Application of agroforestry business models to tropical peatland restoration

Indonesia is home to around 45% of the world’s tropical peatlands which continue to be degraded on a large scale by deforestation, drainage and fire, contributing massively to global GHG emissions. Approaches to restoring the peat–water balance and reducing emissions in peat hydrological units, through managing them based either on full protection or large-scale commercial production, have generally failed to address environmental and local community needs. We present published and unpublished findings pointing to the need for an integrated peatland protection and restoration strategy based first on raising water levels in degraded (drained) peatlands and maintaining them in forested peatlands, thus, reducing GHG emissions. Second, the strategy incorporates ecologically sound agroforestry business models that strengthen livelihoods of smallholders and so sustain their interest in sustainably managing the peatlands. In this paper, we focus on the second element of this strategy in Indonesia. Eight agroforestry business models are proposed based on their merits to attract both smallholders and commercial investors as well as their compatibility with hydrological rehabilitation of the peatlands. While financial returns on investment will vary across sites and countries, our analysis indicates that some models can be profitable over both short and longer time periods with relatively low levels of investment risk.     

How contamination sources and soil properties can influence the Cd and Pb bioavailability to snails

To better understand the fate of metals in the environment, numerous parameters must be studied, such as the soil properties and the different sources of contamination for the organisms. Among bioindicators of soil quality, the garden snail (Cantareus aspersus) integrates multiple sources (e.g. soil, plant) and routes (e.g. digestive, cutaneous) of contamination. However, the contribution of each source on metal bioavailability and how soil properties influence these contributions have never been studied when considering the dynamic process of bioavailability. Using accumulation kinetics, this study showed that the main assimilation source of Cd was lettuce (68 %), whereas the main source of Pb was the soil (90 %). The plant contribution increased in response to a 2-unit soil pH decrease. Unexpectedly, an increase in the soil contribution to metal assimilation accompanied an increase in the organic matter (OM) content of the soil. For both metals, no significant excretion and influence of source on excretion have been modelled either during exposure or depuration. This study highlights how the contribution of different sources to metal bioavailability changes based on changes in soil parameters, such as pH and OM, and the complexity of the processes that modulate metal bioavailability.     

Intra-annual dynamics of water stress in the central Indian Highlands from 2002 to 2012

India’s continued development depends on the availability of adequate water. This paper applies a data-driven approach to estimate the intra-annual dynamics of water stress across the central Indian Highlands over the period 2002–2012. We investigate the spatial distribution of water demanding sectors including industry, domestic, irrigation, livestock and thermal power generation. We also examine the vulnerability of urban centers within the study area to water stress. We find that 74 % of the area of the central Indian Highlands experienced water stress (defined as demand exceeding supply) for 4 or more months out of the year. The rabi (winter) season irrigation drives the intra-annual water stress across the landscape. The Godavari basin experiences the most surface water stress while the Ganga and Narmada basins experience water stress due to groundwater deficits as a result of rabi irrigation. All urban centers experience water stress at some time during a year. Urban centers in the Godavari basin are considerably water stressed, for example, Achalpur, Nagpur and Chandrapur experience water stress 8 months out of the year. Irrigation dominates water use accounting for 95 % of the total water demand, with substantial increases in irrigated land over the last decade. Managing land use to promote hydrologic functions will become increasingly important as water stress increases.     

Conservatism vs. conservationism: differential influences of social identities on beliefs about fracking

ABSTRACT

Although recent expansions in hydraulic fracking operations across the United States have led to greater news coverage and attention from the public, overall understanding remains fairly low. For some, relevant social identities, including environmental or political, may provide a short cut to becoming informed about fracking, or to determining what they believe about it and how that influences their positions on fracking policies. Social identity influence frameworks provide an approach to understanding the relationships between belief and identity, which this study investigates through its affiliational and attitudinal components. National survey data are used to model pathways from environmental and political identities to beliefs about risks associated with fracking. Environmental attitudes significantly predicted belief that fracking has health risks, and mediated a relationship from environmental group affiliation, but environmental information was not significant. Ideology had direct and indirect effects, through partisan media use, while partisanship had direct effects on beliefs about environmental risks.     

Sustainability assessment of water governance alternatives: the case of Guanacaste Costa Rica

Many new forms of water governance are emerging in response to economic and social needs and wants, as well as water-related problems such as scarcity, injustice, and conflict. However, there is little evidence on how sustainable these governance regimes are, which would be critical for making progress toward sustainable and just water governance. In this article, we present the results of a transdisciplinary multi-criteria sustainability assessment of alternative governance regimes for Guanacaste Province, Costa Rica. The assessment specifies differences between sustainable and unsustainable governance regimes, while also pinpointing how the current water governance regime performs in comparison to those alternatives. The findings indicate that those governance regimes with just and deliberative stakeholder involvement, secure groundwater reserves, and healthy dry tropical ecosystems were considered sustainable and just. In contrast, the current state of water governance was found to be at high risk of digressing toward unsustainable systems where rural communities lack rights and influence, where economies favor agro-industry and high impact tourism at the expense of rural livelihoods, and where water scarcity overwhelms weak governance. This assessment study clarifies water sustainability goals, asserts the need for transformational change, and offers a pragmatic foundation for actions toward sustainable water governance.