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Low and High Nitrogen Deposition Rates in Northern Coniferous Forests Have Different Impacts on Aboveground Litter Production, Soil Respiration, and Soil Carbon Stocks
23. Januar 2020
Abstract Nitrogen (N) deposition can change the carbon (C) sink of northern coniferous forests by changing the balance between net primary production and soil respiration. We used a field experiment in an N poor Pinus sylvestris forest where five levels of N (0, 3, 6, 12, and 50 kg N ha−1 yr−1, n = 6) had been added annually for 12–13 years to investigate how litter C inputs and soil respiration, divided into its autotrophic and heterotrophic sources, respond to different rates of N input, and its subsequent effect on soil C storage. The highest N addition...
How do Biotic and Abiotic Factors Regulate Soil Enzyme Activities at Plot and Microplot Scales Under Afforestation?
21. Januar 2020
Abstract Afforestation can greatly affect soil enzymes which are tightly associated with soil nutrient cycling. However, the spatial variations in enzyme activity (EA) in plantation forests and the underlying mechanisms are not well understood. The main goal of this study was to determine how the drivers including the biotic (for example, plant traits and microbial properties) and abiotic factors (for example, soil properties) best regulate spatial variations in EA (β-glucosidase, leucine aminopeptidase and acid phosphatase) in three selected sites [woodland, shrubland...
Recent Growth and Expansion of Birch Shrubs Across a Low Arctic Landscape in Continental Canada: Are These Responses More a Consequence of the Severely Declining Caribou Herd than of Climate Warming?
09. Januar 2020
Abstract The recent widespread expansion of deciduous shrubs across much of the Arctic has been largely attributed to climate warming. This study investigated decadal growth rates of dwarf birch (Betula glandulosa) across a low Arctic landscape in the continental interior of Canada. Detailed birch cover (100 m2 replicate plots) and individual shrub stature measurement datasets for five representative habitat-types were compared between 2006 and 2016, and evaluated in relation to environmental characteristics. Furthermore, dendrochronologically-based annual growth rates...
Unequal Appropriation of Urban Vegetation in Argentine Cities
03. Januar 2020
Abstract Seventy-five percent of the human population will live in urban areas by 2050, and urban vegetation will be the main source of ecosystem services. Unequal access to urban vegetation might exacerbate existing socioeconomic differences. Studies performed in cities of developed countries show that the population with higher socioeconomic status has more access to ecosystem services provided by vegetation. In urban areas, with small internal climatic variation, plant productivity measured through satellite imagery is a good indicator of vegetation availability that...
Early Goose Arrival Increases Soil Nitrogen Availability More Than an Advancing Spring in Coastal Western Alaska
02. Januar 2020
Abstract An understudied aspect of climate change-induced phenological mismatch is its effect on ecosystem functioning, such as nitrogen (N) cycling. Migratory herbivore arrival time may alter N inputs and plant–herbivore feedbacks, whereas earlier springs are predicted to increase N cycling rates through warmer temperatures. However, the relative importance of these shifts in timing and how they interact to affect N cycling are largely unknown. We conducted a 3-year factorial experiment in coastal western Alaska that simulated different timings of Pacific black brant...
El Niño–Southern Oscillations and Pacific Decadal Oscillation as Drivers of the Decadal Dynamics of Benthic Macrofauna in Two Subtropical Estuaries (Southern Brazil)
02. Januar 2020
Abstract The El Niño–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) are large-scale climatic phenomena affecting atmospheric and oceanic teleconnections, and thus triggering weather events at different temporal and spatial scales, both in tropical and extratropical areas. During 11 years (2007–2017), the influence of ENSO events (El Niño, La Niña and neutral), ENSO types (canonical and Modoki) and PDO phases (cold and warm) on meteorological conditions and macrobenthic invertebrates were analyzed in two distinct (tide-dominated and...
Risks of Neglecting Phenology When Assessing Climatic Controls of Primary Production
01. Januar 2020
Abstract We evaluated the effect that integrating annual aboveground net primary production (ANPP) along different 12-month periods has on temporal models of productivity (ANPP as a linear function of annual precipitation). We studied Argentinean Patagonia, which encompasses a variety of climates and biomes. Using MODIS normalized difference vegetation index (NDVI) to estimate green biomass, we assessed the date of maximum annual NDVI for 2000–2016. One quarter of Patagonia (West/South region) exhibited a well-defined seasonality, with maximum NDVI during...
NDVI Spatio-temporal Patterns and Climatic Controls Over Northern Patagonia
01. Januar 2020
Abstract In this study, we identify the main modes of variability of the Normalized Difference Vegetation Index (NDVI) and their relationships with precipitation and temperature variations across northern Patagonia (36°–45° S). In this approach, we combined a recently developed high-resolution gridded dataset (20 × 20 km) for temperature and precipitation with a re-scaled NDVI grid to spatially match the climate database. Climate–vegetation relationships were analyzed taking into account a wide range of temporal variations (intra- to inter-annual) of both...
Addition of Nitrogen Increases Variability of Vegetation Cover in an Arid System with Unpredictable Rainfall
01. Januar 2020
Abstract Addition of nitrogen (N) to rangeland that has been degraded through overgrazing or drought can hasten vegetation recovery. Additional N may influence temporal stability of vegetation cover, however, and change species composition. Potassium (K), by contrast, may help plants survive dry periods, increasing stability. Plant longevity also influences cover stability, but few studies have investigated effects of additional N or K on relative representation of species’ longevities within plant communities. In a semi-arid shrubland, we manipulated N and K in a...
Broadleaf Litter Controls Feather Moss Growth in Black Spruce and Birch Forests of Interior Alaska
01. Januar 2020
Abstract Plant–soil feedbacks can maintain or reinforce alternative states within ecological systems. In Alaskan boreal forests, changes in fire characteristics have stimulated the replacement of needle-leaf black spruce (Picea mariana) by broadleaf deciduous trees. Feather mosses have strong associations with forest type: They dominate black spruce forest understories and are uncommon in broadleaf stands, with consequences for nutrient cycling and carbon storage. Here we test a long-standing hypothesis that broadleaf litter directly excludes mosses with a field...
Loss of Potential Aquatic-Terrestrial Subsidies Along the Missouri River Floodplain
01. Januar 2020
Abstract The floodplains of large rivers have been heavily modified due to riparian development and channel modifications, both of which can eliminate shallow off-channel habitats. The importance of these habitats for aquatic organisms like fishes is well studied. However, loss of off-channel habitat also eliminates habitats for the production of emerging aquatic insects, which subsidize riparian consumers in terrestrial food webs. We used field collections of insect emergence, historical mapping, and statistical modeling to estimate the loss of insect emergence due to...
Applying Climate Change Risk Management Tools to Integrate Streamflow Projections and Social Vulnerability
01. Januar 2020
Abstract Shifts in streamflow, due to future climate and land use change, may pose risks to nearby human communities. Projecting the spatial distribution and impacts of these risks requires consideration of biophysical and socioeconomic factors. Models like the Soil and Water Assessment Tool (SWAT) can project spatial distributions of hydrologic risk due to shifting biophysical factors like climate and land use, but cannot account for socioeconomic factors influencing a community’s capacity to adapt to future streamflow changes. To address this limitation, we used a...
Moth Outbreaks Reduce Decomposition in Subarctic Forest Soils
01. Januar 2020
Abstract Tree mortality from insect infestations can significantly reduce carbon storage in forest soils. In subarctic birch forests (Betula pubescens), ecosystem C cycling is largely affected by recurrent outbreaks of defoliating geometrid moths (Epirrita autumnata, Operophtera brumata). Here, we show that soil C stocks in birch forests across Fennoscandia did not change up to 8 years after moth outbreaks. We found that a decrease in woody fine roots was accompanied by a lower soil CO2 efflux rate and a higher soil N availability following moth outbreaks. We suggest...
Projecting Forest Dynamics Across Europe: Potentials and Pitfalls of Empirical Mortality Algorithms
01. Januar 2020
Abstract Mortality is a key process of forest ecosystem dynamics and functioning strongly altering biomass stocks and carbon residence times. Dynamic vegetation models (DVMs) used to predict forest dynamics are typically based on simple, largely data-free (‘theoretical’) mortality algorithms (MAs). To improve DVM projections, the use of empirically based MAs has been suggested, but little is known about their impact on DVM behavior. A systematic comparison of eight MAs (seven inventory-based, one ‘theoretical’) for the pan-European tree species Pinus sylvestris...
The Potential of Agricultural Conversion to Shape Forest Fire Regimes in Mediterranean Landscapes
01. Januar 2020
Abstract In densely populated fire-prone regions, interactions between global change drivers, such as land-cover changes and climate change, may increase the frequency and severity of wildfires impacting forest ecosystems, thus diminishing their capability of provisioning key ecosystem goods and services for these societies. Yet, landscape mosaics play a crucial role in fire dynamics and behaviour. Here, we argue that promoting heterogeneous agro-forest mosaics could reduce the area affected by future fires. Specifically, we evaluated 24 landscape-scale management...
Opposing Effects of Plant-Community Assembly Maintain Constant Litter Decomposition over Grasslands Aged from 1 to 25 Years
01. Januar 2020
Abstract Litter decomposition is central to ecosystem functioning and depends, under constant abiotic conditions, on litter quality and decomposer activity. During the assembly of a plant community following disturbance, litter quality is expected to decrease, due to an increasing proportion of resource-conservative species, whereas decomposer activity is expected to increase, due to the establishment of decomposer populations and their response to local vegetation (“home-field advantage”, HFA). To date, the combined effect of these processes remains poorly...
Medium, Vector, and Connector: Fog and the Maintenance of Ecosystems
01. Januar 2020
Abstract Fog and low-lying cloud (fog) play a significant role in the maintenance of ecosystems, from desert to alpine and from coastal to inland systems. Our central thesis is that fog provides ecosystems with critical water and nutrient subsidies, and also delivers pollutants, that often control ecosystem function. Fog is a medium, vector, and connector. In this mini-review, we synthesize recent research advances that reveal the diverse ways that fog shapes ecosystem processes. Crown wetting, elemental deposition, and light scattering and absorption are fundamental...
Plant and Soil Nitrogen in an Ombrotrophic Peatland, Southern Canada
01. Januar 2020
Abstract We examined the concentration of nitrogen (N) and δ15N in vegetation and peat in the Mer Bleue bog, Ontario, Canada. Compared with other ecosystems, N concentration in bog plant foliage is low (generally < 1.2%), with more N stored belowground than in foliar tissues. The natural abundance of 15N varies by plant functional type, indicating different strategies for nutrient acquisition. δ15N values of evergreen shrubs and trees are lower (~− 5 to ~− 9‰) than sedges and herbs (~+ 1 to ~− 1‰), likely the result of ericoid mycorrhizal fungi...
The Value of US Urban Tree Cover for Reducing Heat-Related Health Impacts and Electricity Consumption
01. Januar 2020
Abstract High air temperatures are a public health threat, causing 1300 deaths annually in the United States (US) along with heat-related morbidity and increased electricity consumption for air-conditioning (AC). Increasing tree canopy cover has been proposed as one way to reduce urban air temperatures. Here, we assemble tree cover and developed land-cover information for 97 US cities, housing 59 million people, and use regression relationships to analyze how much current urban tree cover reduces summer (JJA) air temperatures and associated heat-related mortality...
Seasonal Disconnect Between Streamflow and Retention Shapes Riverine Nitrogen Export in the Willamette River Basin, Oregon
01. Januar 2020
Abstract Watershed nutrient balance studies traditionally focus on annual fluxes. In areas with strongly seasonal, Mediterranean-type climate regimes, riverine nutrient export may be greater during wet seasons when hydrologic forcing overwhelms or bypasses retention mechanisms. By combining data on riverine export with spatially detailed nutrient inputs, we examine how nitrogen (N) supply, retention, and streamflow shape annual and seasonal riverine N export in Oregon’s Willamette River Basin (WRB). The WRB has pronounced dry summers and wet winters, and the...