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Ecosystems 

Latest Results for Ecosystems
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Greenhouse Gas Balance of Sphagnum Farming on Highly Decomposed Peat at Former Peat Extraction Sites
21. Juli 2021
Abstract For two years, we quantified the exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at two different large-scale Sphagnum farming sites. At both, peat extraction left a shallow layer of highly decomposed peat and low hydraulic conductivities. One site was characterized by preceding multi-annual inundation and irrigated by ditches, while the other one was inoculated directly after peat extraction and irrigated by ditches and drip irrigation. Further, GHG emissions from an irrigation polder and the effect of harvesting Sphagnum donor material...
Topography and Tree Species Improve Estimates of Spatial Variation in Soil Greenhouse Gas Fluxes in a Subtropical Forest
19. Juli 2021
Abstract Subtropical and tropical forests account for over 50% of soil CO2 production, 47% of N2O fluxes of natural ecosystems, and act as both significant sources and sinks of atmospheric CH4. However, ecosystem-scale estimates of these fluxes typically do not account for uncertainty that arises from environmental heterogeneity over small spatial scales. To assess the effects of small-scale environmental heterogeneity on GHG fluxes in a tropical forest ecosystem, we measured fluxes of CO2, CH4, and N2O across a topographic gradient and at the base of different tree...
Fine Wood Decomposition Rates Decline with the Age of Tropical Successional Forests in Southern Mexico: Implications to Ecosystem Carbon Storage
19. Juli 2021
Abstract Wood decomposition in tropical forests is strongly linked to the terrestrial carbon cycle. Our understanding of the successional changes in wood decomposition in diverse tropical forests is still limited. In this study, we tested the hypothesis that fine wood decomposition rates decline with the increasing age of successional forests due to the interspecific variation in wood density and changes in species composition. We studied fine wood decomposition in a chronosequence of tropical forests representing four successional phases in southern Mexico. Wood segments...
Soil Denitrification, the Missing Piece in the Puzzle of Nitrogen Budget in Lowland Agricultural Basins
19. Juli 2021
Abstract Denitrification is a key process buffering the environmental impacts of agricultural nitrate loads but, at present, remains the least understood and poorly quantified sink in nitrogen budgets at the watershed scale. The present work deals with a comprehensive and detailed analysis of nitrogen sources and sinks in the Burana–Volano–Navigabile basin, the southernmost portion of the Po River valley (Northern Italy), an intensively cultivated (> 85% of basin surface) low-lying landscape. Agricultural census data, extensive monitoring of surface–groundwater...
Unexpected Negative Effect of Available Water Capacity Detected on Recent Conifer Forest Growth Trends Across Wide Environmental Gradients
13. Juli 2021
Abstract National Forest Inventories (NFIs) perform systematic forest surveys across space and time. They are hence powerful tools to understand climate controls on forest growth at wide geographical scales and account for the effects of local abiotic and biotic interactions. To investigate the effects of climate change upon growth dynamics of four major European conifer species along elevation and continentality gradients, we herein provide an original harmonization of the French and Austrian NFI datasets. The growth of Norway spruce, Scots pine, silver fir and European...
Very Low Stocks and Inputs of Necromass in Wind-affected Tropical Forests
13. Juli 2021
Abstract The relationships between climate and forest dynamics can help us to interpret patterns of ecosystem carbon and to predict how forests react to climatic changes. We report mass dynamics of deadwood (necromass) from tropical forest ecosystems subject to some of the highest frequency of tropical cyclones in the world and to regular, persistent seasonal monsoon winds. Plots that are influenced by typhoons but exposed to different degrees of monsoon winds were monitored. We expected that stocks and inputs of necromass would reflect the seasonal intensity of wind...
Agricultural Landscape Transformation Needed to Meet Water Quality Goals in the Yahara River Watershed of Southern Wisconsin
09. Juli 2021
Abstract Balancing agricultural production with other ecosystem services is a vexing challenge. The Yahara River watershed in southern Wisconsin is a place where tensions among farmers, policymakers, and citizens at-large run high because nutrient loss from the agricultural practices of a few drive the impairment of surface waters for many. Reducing manure and fertilizer application, as well as increasing perennial grass cover have been proposed as potential solutions. Using the Agro-IBIS agroecosystem model, we examined 48 scenarios of future land management and climate...
Sea-Level Rise and the Persistence of Tree Islands in Coastal Landscapes
09. Juli 2021
Abstract Naturally formed forest patches known as tree islands are found within lower-statured wetland matrices throughout the world, where they contrast sharply with the surrounding vegetation. In some coastal wetlands they are embedded in former freshwater marshes that are currently exposed to saltwater intrusion and mangrove encroachment associated with accelerating sea-level rise. In this study we resurveyed tree composition and determined environmental conditions in tree islands of the coastal Florida Everglades that had been examined two decades earlier. We asked...
The Predominance of Nongrowing Season Emissions to the Annual Methane Budget of a Semiarid Alpine Meadow on the Northeastern Qinghai-Tibetan Plateau
09. Juli 2021
Abstract The terrestrial methane budget varies between different vegetation types and soil conditions and is highly uncertain for alpine grasslands. This work used eddy covariance techniques to continuously measure CH4 flux (NEEm) over a semiarid alpine meadow on the northeastern Qinghai-Tibetan Plateau from January 2017 to August 2019. The diel NEEm averaged 0.14 ± 0.98 nmol CH4 m−2 s−1 (mean ± S.D.), with a rough pattern of daytime release and nocturnal uptake. The 8-day NEEm exhibited a similar sinusoid variation, with a peak of 6.8 mg CH4 m−2 d−1...
Low Redox Decreases Potential Phosphorus Limitation on Soil Biogeochemical Cycling Along a Tropical Rainfall Gradient
09. Juli 2021
Abstract Humid tropical forests on highly weathered soils are often characterized by low bioavailable phosphorus (P) concentrations. These ecosystems also often experience low and fluctuating redox conditions. Little is known about how soil redox conditions affect P availability and how this might feedback on biogeochemical cycling. Here we used soils from a wet tropical rainfall gradient in Puerto Rico to explore the effects of redox on P bioavailability and associated biogeochemical processes. Concentrations of soil carbon (C) and poorly crystalline iron (Fe) and...
Ecological Networks in the Scotia Sea: Structural Changes Across Latitude and Depth
09. Juli 2021
Abstract The Scotia Sea is a productive pelagic ecosystem in the Southern Ocean, which is rapidly changing as a consequence of global warming. Species range shifts are particularly evident, as sub-Antarctic species expand their range from North to South, potentially rearranging the structure of this ecosystem. Thus, studies are needed to determine the current extent of variation in food web structure between these two biogeographic regions of the Scotia Sea and to investigate whether the observed patterns are consistent among depth zones. We compiled a database of 10,888...
Snail Mucus Increases the CO2 Efflux of Biological Soil Crusts
08. Juli 2021
Abstract Biological soil crusts (hereafter, biocrusts) are communities of microorganisms that regulate key ecosystem processes such as water distribution, soil erosion, and nutrient cycling in drylands worldwide. The nature of biocrust function can be influenced by multiple environmental factors, including climatic conditions (for example, precipitation), interactions with plants, and anthropogenic disturbances. Animal regulation of biocrust function has received less research attention, focusing primarily on livestock trampling and to a much lesser extent on biocrust...
Turbidity Structures the Controls of Ecosystem Metabolism and Associated Metabolic Process Domains Along a 75-km Segment of a Semiarid Stream
08. Juli 2021
Abstract Stream ecosystem metabolism contributes to global carbon cycling, yet predicting metabolism across ecosystems remains elusive. Even within stream segments, spatial variation in metabolic rates and their controls can be substantial, exhibiting sudden rather than continuous changes. We measured metabolism at 6 sites along a 75-km mainstem segment of Marsh Creek, Idaho. This agricultural stream lacks major geomorphic transitions such as tributaries or changes in valley width, but possesses patchy patterns of turbidity. We asked: (1) How variable is metabolism along...
Algal Bloom, Succession, and Drawdown of Silicate in the Chukchi Sea in Summer 2010
08. Juli 2021
Abstract The Chukchi Sea is the inflow shelf between the Arctic and the Pacific. A comprehensive research on algal dynamics, physical–biological interactions, and impacts on nutrient drawdown was conducted in summer 2010. The study found a phytoplankton bloom with chlorophyll a (Chla) > 10 mg m−3 at ice edge in July. There were 36 shared algal species in both sea ice and open water, and those species dominated numerically both environments highlighting the seeding role of ice algae for the phytoplankton bloom. The succession pattern of diatom genera at three...
Effects of Soil Abiotic and Biotic Factors on Tree Seedling Regeneration Following a Boreal Forest Wildfire
06. Juli 2021
Abstract Wildfire disturbance is important for tree regeneration in boreal ecosystems. A considerable amount of literature has been published on how wildfires affect boreal forest regeneration. However, we lack understanding about how soil-mediated effects of fire disturbance on seedlings occur via soil abiotic properties versus soil biota. We collected soil from stands with three different severities of burning (high, low and unburned) and conducted two greenhouse experiments to explore how seedlings of tree species (Betula pendula, Pinus sylvestris and Picea abies...
Soil Stoichiometry Mediates Links Between Tree Functional Diversity and Soil Microbial Diversity in a Temperate Forest
25. Juni 2021
Abstract Interactions between plants and soil microbial communities underpin soil processes and forest ecosystem function, but the links between tree diversity and soil microbial diversity are poorly characterized. Differences in both the taxonomic and functional diversity of trees and microbes can shape soil nutrient status and carbon storage, but the stoichiometry of carbon and nutrients in the soil also influences resource availability to plant and microbial communities. Given the key role of resource availability in plant–soil interactions, we hypothesized that...
Is Zooplankton Body Size an Indicator of Water Quality in (Sub)tropical Reservoirs in China?
23. Juni 2021
Abstract Large zooplankton can efficiently graze on algae and thereby improve water quality. However, zooplankton body size is considered to decrease with decreasing latitude because of the high fish predation and warm temperatures at lower latitudes. To explore how fish stocking has destabilized the trophic cascade and influenced water quality along a latitudinal gradient of reservoirs, we compared zooplankton body size and trophic cascades to water quality indicators in the subtropical Lake Qiandaohu and in tropical Guangdong reservoirs. The results showed that the body...
Fire Severity and Post-fire Hydrology Drive Nutrient Cycling and Plant Community Recovery in Intermittent Wetlands
22. Juni 2021
Abstract Fire is a critical driver of plant and soil nutrient cycling in nutrient-limited ecosystems. Phosphorus (P)-limited and fire-adapted ecosystems can uptake fire-released P, but it is uncertain how post-fire hydrology interacts with fire severity to affect carbon (C) and P cycling in plants and soils. We examined the interactive effects of fire severity and post-fire hydroperiod (defined as the number of days of surface soil inundation in a year for which maximum water depth is a proxy) on soil and plant C and P cycling in intermittent wetlands in south-central...
Carbon and Nitrogen Stocks and Burial Rates in Intertidal Vegetated Habitats of a Mesotidal Coastal Lagoon
22. Juni 2021
Abstract Coastal vegetated ecosystems such as saltmarshes and seagrasses are important sinks of organic carbon (OC) and total nitrogen (TN), with large global and local variability, driven by the confluence of many physical and ecological factors. Here we show that sedimentary OC and TN stocks of intertidal saltmarsh (Sporobolus maritimus) and seagrass (Zostera noltei) habitats increased between two- and fourfold along a decreasing flow velocity gradient in Ria Formosa lagoon (south Portugal). A similar twofold increase was also observed for OC and TN burial rates of S...
Disentangling the Legacies of Climate and Management on Tree Growth
22. Juni 2021
Abstract Legacies of past climate conditions and historical management govern forest productivity and tree growth. Understanding how these processes interact and the timescales over which they influence tree growth is critical to assess forest vulnerability to climate change. Yet, few studies address this issue, likely because integrated long-term records of both growth and forest management are uncommon. We applied the stochastic antecedent modelling (SAM) framework to annual tree-ring widths from mixed forests to recover the ecological memory of tree growth. We...