Institute for Culture and Ecology

Abstract Plants and mycorrhizal fungi form mutualistic relationships that affect how resources flow between organisms and within ecosystems. Common mycorrhizal networks (CMNs) could facilitate preferential transfer of carbon and limiting nutrients, but this remains difficult to predict. Do CMNs favour fungal resource acquisition at the expense of plant resource demands (a fungi‐centric view), or are they passive channels through which plants regulate resource fluxes (a plant‐centric view)? We used stable isotope tracers (13CO2 and 15NH3), plant traits, and mycorrhizal DNA to quantify above‐ and below‐ground carbon and nitrogen transfer between 18 plant species along a 520‐km latitudinal gradient in the Pacific Northwest, USA. Plant functional type and tissue stoichiometry were the most important predictors of interspecific resource transfer. Of ‘donor’ plants, 98% were 13C‐enriched, but we detected transfer in only 2% of ‘receiver’ plants. However, all donors were 15N‐enriched and we detected transfer in 81% of receivers. Nitrogen was preferentially transferred to annuals (0.26 ± 0.50 mg N per g leaf mass) compared with perennials (0.13 ± 0.30 mg N per g leaf mass). This corresponded with tissue stoichiometry differences. Synthesis Our findings suggest that plants and fungi that are located closer together in space and with stronger demand for resources over time are more likely to receive larger amounts of those limiting resources. Read the free Plain Language Summary for this article on the Journal blog.

The widely cited frequency code hypothesis attempts to explain a diverse range of communicative phenomena through the acoustic projection of body size. The set of phenomena includes size sound symbolism (using /i/ to signal smallness in words such as teeny), intonational phonology (using rising contours to signal questions) and the indexing of social relations via vocal modulation, such as lowering one's voice pitch to signal dominance. Among other things, the frequency code is commonly interpreted to suggest that polite speech should be universally signalled via high pitch owing to the association of high pitch with small size and submissiveness. We present a cross-cultural meta-analysis of polite speech of 101 speakers from seven different languages. While we find evidence for cross-cultural variation, voice pitch is on average lower when speakers speak politely, contrary to what the frequency code predicts. We interpret our findings in the light of the fact that pitch has a multiplicity of possible communicative meanings. Cultural and contextual variation determines which specific meanings become manifest in a specific interactional context. We use the evidence from our meta-analysis to propose an updated view of the frequency code hypothesis that is based on the existence of many-to-many mappings between speech acoustics and communicative interpretations.This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

The genetic diversity of germplasm used in reintroduction and restoration efforts can influence how resulting populations establish, reproduce, and evolve over time, particularly in disturbed and changing conditions. Regional admixture provenancing, mixing seeds derived from multiple populations within the same region as the target site, has been suggested to produce genetically diverse germplasm. Yet little empirical evidence shows how genetic diversity in germplasm resulting from this approach compares to source populations, or how it varies in restored populations. Here, we use neutral molecular markers to follow genetic diversity through production and use of germplasm when mixing multiple source populations in nursery production beds. Castilleja levisecta is a rare species experiencing inbreeding depression in remaining populations, with a federal recovery plan requiring the re‐establishment of populations in areas where it has been extirpated. Specifically, we track diversity from wild‐collected source populations through different production approaches and reintroductions using two propagule types. We show that measures of genetic diversity, inbreeding, and relatedness change during the production and use of material produced with a regional admixture provenancing approach, with the step at which source populations are mixed and germplasm type used influencing whether all source populations are equally represented. While genetic diversity increased throughout the process, inbreeding and relatedness increased in nursery production beds but decreased in reintroductions, with the lowest inbreeding and relatedness in populations restored using seeds rather than plugs. The results highlight the importance of taking an integrated approach informed by research when planning and implementing reintroductions with mixed‐source germplasm.

Effective conservation and restoration of estuarine wetlands require accurate maps of their historical and current extent, as well as estimated losses of these valued habitats. Existing coast-wide tidal wetland mapping does not explicitly map historical tidal wetlands that are now disconnected from the tides, which represent restoration opportunities; nor does it use water level models or high-resolution elevation data (e.g. lidar) to accurately identify current tidal wetlands. To better inform estuarine conservation and restoration, we generated new maps of current and historical tidal wetlands for the entire contiguous U.S. West Coast (Washington, Oregon, and California). The new maps are based on an Elevation-Based Estuary Extent Model (EBEEM) that combines lidar digital elevation models (DEMs) and water level models to establish the maximum historical extent of tidal wetlands, representing a major step forward in mapping accuracy for restoration planning and analysis of wetland loss. Building from this new base, we also developed an indirect method for mapping tidal wetland losses, and created maps of these losses for 55 estuaries on the West Coast (representing about 97% of historical West Coast vegetated tidal wetland area). Based on these new maps, we estimated that total historical estuary area for the West Coast is approximately 735,000 hectares (including vegetated and nonvegetated areas), and that about 85% of vegetated tidal wetlands have been lost from West Coast estuaries. Losses were highest for major river deltas. The new maps will help interested groups improve action plans for estuarine wetland habitat restoration and conservation, and will also provide a better baseline for understanding and predicting future changes with projected sea level rise.

Summary 1. Interactions among plants and their consumers, pollinators and dispersers are central to evolutionary theory, but interactions among plants themselves have received much less attention. Thus focusing more attention on the evolutionary role of plant–plant interactions may provide greater insight into the processes that organize communities. 2. Here, we integrate divergent themes in the literature in an effort to provide a synthesis of empirical evidence and ideas about how plant interactions may affect evolution and how evolution may affect plant interactions. 3. First, we discuss the idea of niche partitioning evolving through competitive interactions among plants, the idea of niche construction evolving through facilitative interactions, and the connections between these ideas and more recent research on diversity and ecosystem function and trait‐based community organization. 4. We then review how a history of coexistence within a region might affect competitive outcomes and explore the mechanisms by which plants exert selective forces on each other. Next, we consider recent research on invasions suggesting that plant interactions can reflect regional evolutionary trajectories. Finally, we place these lines of research into the context of extended phenotypes and the geographic mosaic of co‐evolution. 5. Synthesis. Our synthesis of separate lines of inquiry is a step towards understanding the evolutionary importance of interactions among plants, and suggests that the evolutionary consequences of interactions contribute to communities that are more than assemblages of independent populations.

Matrix projection models are among the most widely used tools in plant ecology. However, the way in which plant ecologists use and interpret these models differs from the way in which they are presented in the broader academic literature. In contrast to calls from earlier reviews, most studies of plant populations are based on < 5 matrices and present simple metrics such as deterministic population growth rates. However, plant ecologists also cautioned against literal interpretation of model predictions. Although academic studies have emphasized testing quantitative model predictions, such forecasts are not the way in which plant ecologists find matrix models to be most useful. Improving forecasting ability would necessitate increased model complexity and longer studies. Therefore, in addition to longer term studies with better links to environmental drivers, priorities for research include critically evaluating relative/comparative uses of matrix models and asking how we can use many short-term studies to understand long-term population dynamics.

The relationship between star formation and super-massive black hole growth is central to our understanding of galaxy formation and evolution. Hyper-Luminous Infrared Galaxies (HLIRGs) are unique laboratories to investigate the connection between starburst (SB) and Active Galactic Nuclei (AGN), since they exhibit extreme star formation rates, and most of them show evidence of harbouring powerful AGN. Our previous X-ray study of a sample of 14 HLIRGs shows that the X-ray emission of most HLIRGs is dominated by AGN activity. To improve our estimate of the relative contribution of the AGN and SB emission to its total bolometric output, we have built broad band spectral energy distributions (SEDs) for these HLIRGs, and we have fitted empirical AGN and SB templates to these SEDs. In broad terms, most sources are well fitted using this method, and we found AGN and SB contributions similar to those obtained by previous studies of HLIRGs. We have classified the HLIRGs SEDs in two groups, named class A and class B. Class A HLIRGs show a flat SED from the optical to the infrared energy range. Three out of seven class A sources can be modelled with a pure luminosity-dependent QSO template, while the rest of them require a type 1 AGN template and a SB template. The SB component is dominant in three out of four class A objects. Class B HLIRGs show SEDs with a prominent and broad IR bump. These sources can not trivially be modelled with a combination of pure AGN and pure SB, they require templates of composite objects, suggesting that >50% of their emission comes from stellar formation processes. We propose that our sample is actually composed by three different populations: very luminous QSO, young galaxies going through their maximal star formation period and the high luminosity tail of ULIRG population distribution.

Summary Management recommendations intended to reduce rangeland degradation and increase livestock productivity often assume equilibrium conditions wherein vegetation and herbivore dynamics are tightly coupled. Recent research in Africa, Asia and North America, however, suggests that the dynamics of some arid systems are driven more by precipitation, a non‐equilibrium factor. We examined the applicability of equilibrium and non‐equilibrium theory for key grazing resources within an Andean pastoral ecosystem. Residents of Cosapa, Bolivia, recently fenced off portions of critical communal grazing areas called bofedal (wet meadow) and gramadal (dry meadow) as part of a livestock development project. Fenced exclosures were used to implement seasonally deferred grazing practices. We evaluated the effects of deferred grazing on peak standing crop (SC), above‐ground net primary production (ANPP) and plant species composition and diversity over a 4‐month growing season across 10 locations. Effects of exclosure access on the productivity of alpaca Llama pacos, llama L. glama and sheep Ovis aries were assessed through interviews with 32 herd owners. One to three years of deferred grazing had no effect on SC or ANPP from bofedal or gramadal, but it did reduce plant species diversity for bofedal. Access to exclosures improved survival rates of young alpaca and birth rates for sheep. Llamas were typically denied access to exclosures, which negatively affected their productivity. Our results suggest that both non‐equilibrium and equilibrium forces operate on bofedal. Stable and low rates of ANPP are largely shaped by the cold climate, a non‐equilibrium factor. Changes in plant species composition and livestock productivity, however, support equilibrium theory. Synthesis and applications. Ecological models of rangeland dynamics often play a critical role in determining the direction of range management and pastoral development. On bofedal, we found that vegetation and herbivore dynamics are coupled to a large extent, consistent with predictions that equilibrium behaviour can occur for critical, mesic subsystems nested within arid landscapes. Seasonal grazing deferral on bofedal can thus yield benefits to livestock productivity. However, these benefits must be weighed against negative social consequences that can occur when communal resources are privatized.

This paper analyses and evaluates the bordering and othering impacts of environmental geopolitical discourse on land conservation in Southern Africa. Through a theoretical in-depth analysis of the use and contents of the term conservation, this paper examines how conservation is determined, instrumentalized and interpreted by the state, international governmental and non-governmental institutions, and specific interest groups including neo-liberal capitalists and local communities especially in the developing world context. In particular, we discuss the impact of current transboundary park-like conservation practices in Southern Africa and how these feed into the continuous attempts to colonise Southern Africa's nature.

Summary During the past decade, NTFPs have begun to appear on mainstream scientific research agendas in a variety of disciplines. Development of a strong NTFP research capacity will require the construction of links between on-going and emerging NTFP research programs focused on U.S. NTFP issues, establishment of strong ties to international NTFP research programs, and the use of interdisciplinary and collaborative research approaches. Understanding forests as biophysical systems that also include humans will enhance the effectiveness and relevance of U.S.-oriented NTFP research efforts.