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Ecosystems 

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Losses of Soil Organic Carbon with Deforestation in Mangroves of Madagascar
06. April 2020
Abstract Global mangrove deforestation has resulted in substantial CO2 emissions to the atmosphere, but the extent of emissions from soil organic carbon (C) loss remains difficult to assess. Here, we sampled five intact and five deforested mangrove plots from Tsimipaika Bay, Madagascar, to examine the loss of soil C in the 10 years since deforestation. We estimated tree biomass and analyzed grain size, 210Pb activities, organic C and total nitrogen (N) and their stable isotopes in soils as well as dissolved organic C in surface waters. Deforested soils revealed evidence...
Biocrusts Modulate Responses of Nitrous Oxide and Methane Soil Fluxes to Simulated Climate Change in a Mediterranean Dryland
Abstract Little is known about the role of biocrusts in regulating the responses of N2O and CH4 fluxes to climate change in drylands. Here, we aim to help filling this knowledge gap by using an 8-year field experiment in central Spain where temperature and rainfall are being manipulated (~ 1.9°C warming, 33% rainfall reduction and their combination) in areas with and without well-developed biocrust communities. Areas with initial high cover of well-developed biocrusts showed lower N2O emissions, enhanced CH4 uptake and higher abundances of functional genes linked to...
Transpiration of Dominant Tree Species Varies in Response to Projected Changes in Climate: Implications for Composition and Water Balance of Temperate Forest Ecosystems
Abstract The climate is changing in many temperate forests with winter snowpack shrinking and an increasing frequency of growing season air temperatures exceeding long-term means. We examined the effects of these changes on growing season rates of transpiration (sap flow) in two snow removal experiments in New Hampshire and Massachusetts, USA. Snow was removed during early winter, resulting in greater depth and duration of soil freezing compared to untreated plots. We examined the dominant tree species at each site, Acer saccharum at Hubbard Brook, NH and Acer rubrum and...
A Small Nimble In Situ Fine-Scale Flux Method for Measuring Tree Stem Greenhouse Gas Emissions and Processes (S.N.I.F.F)
Abstract Tree stem methane emissions are gaining increasing attention as an overlooked atmospheric source pathway. Existing methods for measuring tree stem greenhouse gas fluxes and isotopes may provide robust integrated emission estimates, but due to their coarse resolution, the capacity to derive insights into fine-scale dynamics of tree stem emissions is limited. We demonstrate and field test an alternative method that is Small, Nimble, In situ and allows for Fine-scale Flux (‘SNIFF’) measurements, on complex and contrasting stem surfaces. It is lightweight and...
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Water and Carbon Fluxes Along an Elevational Gradient in a Sagebrush Ecosystem
Abstract Differences in water and carbon fluxes along a climate/elevation gradient within a sagebrush ecosystem are quantified, and inferences are made about climate warming using a network of eddy covariance systems. Sites are located within the Reynolds Creek Critical Zone Observatory in southwestern Idaho, USA, with elevations ranging from 1425 to 2111 m, annual precipitation ranging from 290 to 795 mm and annual temperature ranging from 9.1 to 5.4 °C. Annual gross ecosystem production (GEP) for the sites averaged (± uncertainty) 385 ± 6, 549 ± 19...
Involving Stakeholders’ Knowledge in Co-designing Social Valuations of Biodiversity and Ecosystem Services: Implications for Decision-Making
ABSTRACT We contribute to addressing two gaps that reduce the utility of ecosystem sciences for decision-making: lack of standard methods for using stakeholders’ knowledge to co-design ecosystem services science research, and absence of commensurable social valuation metrics that allow effective value comparisons. In two phases, we used co-designed instruments to conduct social valuation of biodiversity, and provisioning, cultural and regulating services. First, we conducted eight participatory fora, where experts and non-experts identified ecosystem aspects to which...
Thirty-Year Repeat Measures of Mangrove Above- and Below-Ground Biomass Reveals Unexpectedly High Carbon Sequestration
Abstract Mangrove ecosystems store large quantities of organic carbon for long periods of time. This study explores organic carbon stock change through the first comparative study of radiometric analysis and repeat field measures over a multi-decadal period in a mangrove system. Examining one tall gallery forest of Avicennia marina, and an adjacent interior scrub mangrove of mixed Avicennia marina and Aegiceras corniculatum, radiometric analysis estimated a soil organic carbon accumulation rate of 4.3 ± 0.6 Mg C ha−1 y−1 in the tall gallery forest and...
Tracking the Dynamic Ecological History of a Tropical Urban Estuary as it Responds to Human Pressures
Abstract Coastal cities in tropical areas are often low-lying and vulnerable to the effects of flooding and storms. San Juan, Puerto Rico, is a good example of this. It is built around a lagoon-channel complex called the San Juan Bay Estuary (SJBE). A critical channel in the estuary, the Caño Martín Peña, has filled in and now frequently floods the surrounding communities with sewage-enriched waters, causing a series of human health and ecological problems. Sediment core analyses indicate that portions of the SJBE now function as settling basins. High urban and...
Grazing Offsets Nitrogen Enrichment Effects on Species Richness by Promoting the Random Colonization of Local Species in an Alpine Grassland
Abstract Nitrogen (N)-induced declines in species richness can be offset by grazing via the suppression of dominant species to increase ground-level light. However, it is not known whether grazing-mediated locally colonized species correspond to N-induced locally extinct species with regard to taxonomy or traits. Data from 11 years of N addition and winter grazing experiments were analyzed to assess species richness dynamics at community and functional group levels. Regarding N treatments, enclosure and N addition were performed during the first 7 years and were then...
Leaf Nutrients and Macroinvertebrates Control Litter Mixing Effects on Decomposition in Temperate Streams
Abstract Plant litter decomposition is an essential ecosystem function in temperate streams. Both riparian vegetation and decomposer communities are major determinants of the decomposition efficiency and the interactions occurring within litter mixtures. However, the extent to which such litter mixture interactions are affected by combined shifts in litter traits and decomposer community is not well understood. We used leaf litter from 10 European tree species in order to study litter decomposition and litter mixture effects occurring in two-species litter mixtures in a...
Soil Homogenization Modifies Productivity, Nitrogen Retention and Decomposition in Restored Grassland
Abstract At the local (within site) scale, soil heterogeneity can influence ecosystem function. However, in former agricultural systems, soil heterogeneity can be low as a legacy of tillage (that is, via the process of soil homogenization). We investigated the relationship between soil homogenization and three ecosystem functional response variables—aboveground productivity, nitrogen retention (assessed via 15N tracer addition) and plant litter decomposition (assessed using litter bags)—during the first 2 years following a tallgrass prairie restoration in a former...
Bridging the Gap Between Salmon Spawner Abundance and Marine Nutrient Assimilation by Juvenile Salmon: Seasonal Cycles and Landscape Effects at the Watershed Scale
Abstract Anadromous Pacific salmon are semelparous, and resource subsidies from spawning adults (marine-derived nutrients, or MDN) benefit juvenile salmonids rearing in freshwater. However, it remains unclear how MDN assimilation relates to spawner abundance within a watershed. To address this, we examined seasonal, watershed-scale patterns of MDN assimilation in rearing coho (Oncorhynchus kisutch) and Chinook (O. tshawytscha) salmon and compared it with spawner biomass and landscape features in a western Alaska watershed with contrasting structural complexity in two...
Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic
Abstract Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (δ13C, Δ14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil...
Asian Cities are Greening While Some North American Cities are Browning: Long-Term Greenspace Patterns in 16 Cities of the Pan-Pacific Region
Abstract Pan-Pacific cities are home to nearly 55% of the world’s urban residents. As the fastest growing urban centers in the world, their growth comes with increasing demand for urban amenities such as greenspace. Yet, our understanding of greenspace trends within and among pan-Pacific cities is limited due to a lack of consistent long-term land cover data necessary for transnational comparisons. We tracked and compared greenspace patterns in 16 major pan-Pacific cities over 28 years. We asked: (1) How do long-term trends in greenspace heterogeneity differ among...
Eco-hydrological Functions in Forested Catchments of Southern Chile
Abstract Ecosystem functions in forests can vary significantly after disturbance, depending on changes in vegetation structure during succession and soil biophysical characteristics. We examined streamflow regulation, water storage and soil protection functions in small catchments covered by evergreen temperate rain forests, developed over volcanic ash soils, in southern South America. Our aims were to understand the differences in ecosystem functioning among catchments representing different forest stages following human disturbance, from scrubland to old-growth forest...
Tipping Points in the Mangrove March: Characterization of Biogeochemical Cycling Along the Mangrove–Salt Marsh Ecotone
Abstract Coastal wetland vegetation communities can respond to sea level rise via the encroachment of more salt- and inundation-tolerant species into existing vegetation communities. Black mangroves (Avicennia germinans L.) are encroaching on saltgrass (Distichlis spicata L.) within the Merritt Island National Wildlife Refuge in east central Florida (USA). Nine soil cores collected along three transects captured the transitions of both perceived abiotic drivers (salinity and inundation) and vegetation communities during both high- and low-water seasons to investigate...
The Shifting Role of mRUE for Regulating Ecosystem Production
Abstract To create a comprehensive view of ecosystem resource use, we integrated parallel resource use efficiency observations into a multiple-resource use efficiency (mRUE) framework using a dynamic factor analysis model. Results from 56 site-years of eddy covariance data and mRUE factors for a site in the US Midwest show temporal dynamics and coherence (using Pearson’s R) among resources are associated with interannual variation in precipitation. Loading factors are derived from mRUE observations and quantify how strongly data are connected to the underlying...
Carbon and Nitrogen Sequestration of Melaleuca Floodplain Wetlands in Tropical Australia
Abstract Wetlands of Melaleuca spp. in Australia form large forests that are highly threatened by deforestation and degradation. In America, Melaleuca has invaded large areas of native wetlands causing extensive damage. Despite their status as an endangered native ecosystem and as a highly invasive one, little is known about their C and N dynamics. In this study, we sampled five Melaleuca wetlands and measured their C and N ecosystem stocks (aboveground biomass and soil), tree accumulation rates, sedimentation rates, and soil stability. Melaleuca wetlands were highly...
Ecological Consequences of Animal Migration: Prey Partial Migration Affects Predator Ecology and Prey Communities
Abstract Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby...