Separating the effects on water chemistry of climate variation and experimental manipulation in the long-term acidification and recovery of lakesThis paper is part of the series “Forty Years of Aquatic Research at the Experimental Lakes Area”.

2009 ◽  
Vol 66 (11) ◽  
pp. 1864-1874 ◽  
Author(s):  
Raymond H. Hesslein ◽  
Michael A. Turner ◽  
Douglas Guss ◽  
Mark Lyng
Keyword(s):  
Organic Carbon ◽  
Water Chemistry ◽  
Experimental Manipulation ◽  
Low Ph ◽  
Chemical Mass Balance ◽  
Experimental Lakes Area ◽  
First Order ◽  
Mass Balance Models ◽  
Acidification And Recovery

Changes in climate, in particular significant changes in precipitation and evaporation and thus runoff, as well as changes in regional atmospheric deposition can affect the changes in chemical masses or concentrations in lakes. We have examined the changes in alkalinity, sulfate, and dissolved organic carbon (DOC) during a 20-year period when Lake 302S and Lake 302N at the Experimental Lakes Area (Ontario, Canada) were acidified with sulfuric, nitric, and hydrochloric acids and returned to natural pH. We used the corresponding 20-year history in Lake 239 to build chemical mass balance models for the experimental lakes. With these models, we assessed the production of alkalinity and the loss of sulfate and DOC in the context of atmospheric and watershed inputs and our experimental acid additions. Alkalinity production was greatest during the period of highest acid inputs and not detectable during pH recovery even in the early stages when pH was still low. Sulfate loss was also greatest while sulfate concentrations were increasing but counter to expectations not directly related to sulfate concentrations. Losses of the mass of DOC showed little change in response to acid additions over the 20 years, but first-order losses increased at low pH.

scholarly journals Comparing models of microbial–substrate interactions and their response to warming

2016 ◽  
Vol 13 (6) ◽  
pp. 1733-1752 ◽  
Author(s):  
Debjani Sihi ◽  
Stefan Gerber ◽  
Patrick W. Inglett ◽  
Kanika Sharma Inglett
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Positive Feedback ◽  
Enzyme Production ◽  
Microbial Growth ◽  
Quasi Equilibrium ◽  
Short Term ◽  
First Order

Abstract. Recent developments in modelling soil organic carbon decomposition include the explicit incorporation of enzyme and microbial dynamics. A characteristic of these models is a positive feedback between substrate and consumers, which is absent in traditional first-order decay models. With sufficiently large substrate, this feedback allows an unconstrained growth of microbial biomass. We explore mechanisms that curb unrestricted microbial growth by including finite potential sites where enzymes can bind and by allowing microbial scavenging for enzymes. We further developed a model where enzyme synthesis is not scaled to microbial biomass but associated with a respiratory cost and microbial population adjusts enzyme production in order to optimise their growth. We then tested short- and long-term responses of these models to a step increase in temperature and find that these models differ in the long-term when short-term responses are harmonised. We show that several mechanisms, including substrate limitation, variable production of microbial enzymes, and microbes feeding on extracellular enzymes eliminate oscillations arising from a positive feedback between microbial biomass and depolymerisation. The model where enzyme production is optimised to yield maximum microbial growth shows the strongest reduction in soil organic carbon in response to warming, and the trajectory of soil carbon largely follows that of a first-order decomposition model. Modifications to separate growth and maintenance respiration generally yield short-term differences, but results converge over time because microbial biomass approaches a quasi-equilibrium with the new conditions of carbon supply and temperature.

Temporal Patterns of Acidification of Rivers in Nova Scotia and Newfoundland and their Relationship to Sulphate Emissions

1988 ◽  
Vol 23 (4) ◽  
pp. 532-541
Author(s):  
G. D. Howell ◽  
P.E.J. Green ◽  
C.A. Field ◽  
B. Freedman
Keyword(s):  
Statistical Analysis ◽  
Nova Scotia ◽  
Water Chemistry ◽  
Sulphur Dioxide ◽  
Low Ph ◽  
Hydrogen Ion ◽  
Atlantic Canada ◽  
Atmospheric Loading ◽  
Mineral Acids ◽  
Sulphur Dioxide Emission

Abstract Twenty-eight rivers in Atlantic Canada are sampled monthly, and have periods of record dating back as far as 1965. Statistical analysis of water chemistry for rivers in areas of Nova Scotia and Newfoundland that are believed to be sensitive to acidification has revealed that pH was significantly lower during the late 1960’s and early 1970’s. Annual hydrogen ion export for selected rivers was also greater during this period. This period of relatively low pH and large hydrogen ion export corresponds to a peak of North American sulphur dioxide emission, suggesting that these rivers may be responding to atmospheric loading of anthropogenic mineral acids.

scholarly journals Effect of Long-Term Soil Management Practices on Tree Growth, Yield and Soil Biodiversity in a High-Density Olive Agro-Ecosystem

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1036
Author(s):  
Sauro Simoni ◽  
Giovanni Caruso ◽  
Nadia Vignozzi ◽  
Riccardo Gucci ◽  
Giuseppe Valboa ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Structure ◽  
Soil Management ◽  
Carbon Pools ◽  
Grass Cover ◽  
Soil Biodiversity ◽  
Canopy Effect ◽  
Soil Organic Carbon Pools

Edaphic arthropod communities provide valuable information about the prevailing status of soil quality to improve the functionality and long-term sustainability of soil management. The study aimed at evaluating the effect of plant and grass cover on the functional biodiversity and soil characteristics in a mature olive orchard (Olea europaea L.) managed for ten years by two conservation soil managements: natural grass cover (NC) and conservation tillage (CT). The trees under CT grew and yielded more than those under NC during the period of increasing yields (years 4–7) but not when they reached full production. Soil management did not affect the tree root density. Collecting samples underneath the canopy (UC) and in the inter-row space (IR), the edaphic environment was characterized by soil structure, hydrological properties, the concentration and storage of soil organic carbon pools and the distribution of microarthropod communities. The soil organic carbon pools (total and humified) were negatively affected by minimum tillage in IR, but not UC, without a loss in fruit and oil yield. The assemblages of microarthropods benefited, firstly, from the grass cover, secondly, from the canopy effect, and thirdly, from a soil structure ensuring a high air capacity and water storage. Feeding functional groups—hemiedaphic macrosaprophages, polyphages and predators—resulted in selecting the ecotonal microenvironment between the surface and edaphic habitat.

scholarly journals Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 734
Author(s):  
Xiankai Lu ◽  
Qinggong Mao ◽  
Zhuohang Wang ◽  
Taiki Mori ◽  
Jiangming Mo ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Soil Carbon ◽  
Tropical Forests ◽  
Carbon Mineralization ◽  
N Deposition ◽  
Soil Carbon Mineralization ◽  
N Additions

Anthropogenic elevated nitrogen (N) deposition has an accelerated terrestrial N cycle, shaping soil carbon dynamics and storage through altering soil organic carbon mineralization processes. However, it remains unclear how long-term high N deposition affects soil carbon mineralization in tropical forests. To address this question, we established a long-term N deposition experiment in an N-rich lowland tropical forest of Southern China with N additions such as NH4NO3 of 0 (Control), 50 (Low-N), 100 (Medium-N) and 150 (High-N) kg N ha−1 yr−1, and laboratory incubation experiment, used to explore the response of soil carbon mineralization to the N additions therein. The results showed that 15 years of N additions significantly decreased soil carbon mineralization rates. During the incubation period from the 14th day to 56th day, the average decreases in soil CO2 emission rates were 18%, 33% and 47% in the low-N, medium-N and high-N treatments, respectively, compared with the Control. These negative effects were primarily aroused by the reduced soil microbial biomass and modified microbial functions (e.g., a decrease in bacteria relative abundance), which could be attributed to N-addition-induced soil acidification and potential phosphorus limitation in this forest. We further found that N additions greatly increased soil-dissolved organic carbon (DOC), and there were significantly negative relationships between microbial biomass and soil DOC, indicating that microbial consumption on soil-soluble carbon pool may decrease. These results suggests that long-term N deposition can increase soil carbon stability and benefit carbon sequestration through decreased carbon mineralization in N-rich tropical forests. This study can help us understand how microbes control soil carbon cycling and carbon sink in the tropics under both elevated N deposition and carbon dioxide in the future.

scholarly journals Cariogenic Biofilm: Pathology-Related Phenotypes and Targeted Therapy

2021 ◽  
Vol 9 (6) ◽  
pp. 1311
Author(s):  
Xiuqin Chen ◽  
Eric Banan-Mwine Daliri ◽  
Akanksha Tyagi ◽  
Deog-Hwan Oh
Keyword(s):  
Treatment Strategies ◽  
High Specificity ◽  
Low Ph ◽  
Oral Microbiota ◽  
Extracellular Polymers ◽  
Dental Biofilm ◽  
Health And Disease ◽  
Promising Treatment ◽  
Cariogenic Biofilm

The initiation and development of cariogenic (that is, caries-related) biofilms are the result of the disruption of homeostasis in the oral microenvironment. There is a daily accumulation of dental biofilm on the surface of teeth and its matrix of extracellular polymers supports the host in its defense against invading microbes, thus helping to achieve oral microbial homeostasis. However, the homeostasis can be broken down under certain circumstances such as during long-term exposure to a low pH environment which results in the dominance of acidogenic and acid-tolerating species in the dental biofilm and, thus, triggers the shift of harmless biofilm to an acidic one. This work aims to explore microbial diversity and the quorum sensing of dental biofilm and their important contributions to oral health and disease. The complex and multispecies ecosystems of the cariogenic biofilm pose significant challenges for the modulation of the oral microenvironment. Promising treatment strategies are those that target cariogenic niches with high specificity without disrupting the balance of the surrounding oral microbiota. Here, we summarized the recent advances in modulating cariogenic biofilm and/or controlling its pathogenic traits.

scholarly journals Tracking Changes on Soil Structure and Organic Carbon Sequestration after 30 Years of Different Tillage and Management Practices

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 291
Author(s):  
Ramón Bienes ◽  
Maria Jose Marques ◽  
Blanca Sastre ◽  
Andrés García-Díaz ◽  
Iris Esparza ◽  
...  
Keyword(s):  
Triticum Aestivum ◽  
Organic Carbon ◽  
Management Practices ◽  
Management Strategies ◽  
Triticum Aestivum L ◽  
Field Trials ◽  
Conventional Tillage ◽  
Soil Parameters ◽  
Wilting Point

Long-term field trials are essential for monitoring the effects of sustainable land management strategies for adaptation and mitigation to climate change. The influence of more than thirty years of different management is analyzed on extensive crops under three tillage systems, conventional tillage (CT), minimum tillage (MT), and no-tillage (NT), and with two crop rotations, monoculture winter-wheat (Triticum aestivum L.) and wheat-vetch (Triticum aestivum L.-Vicia sativa L.), widely present in the center of Spain. The soil under NT experienced the largest change in organic carbon (SOC) sequestration, macroaggregate stability, and bulk density. In the MT and NT treatments, SOC content was still increasing after 32 years, being 26.5 and 32.2 Mg ha−1, respectively, compared to 20.8 Mg ha−1 in CT. The SOC stratification (ratio of SOC at the topsoil/SOC at the layer underneath), an indicator of soil conservation, increased with decreasing tillage intensity (2.32, 1.36, and 1.01 for NT, MT, and CT respectively). Tillage intensity affected the majority of soil parameters, except the water stable aggregates, infiltration, and porosity. The NT treatment increased available water, but only in monocropping. More water was retained at the permanent wilting point in NT treatments, which can be a disadvantage in dry periods of these edaphoclimatic conditions.

scholarly journals Effects of Management and Hillside Position on Soil Organic Carbon Stratification in Mediterranean Centenary Olive Grove

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 650
Author(s):  
Jesús Aguilera-Huertas ◽  
Beatriz Lozano-García ◽  
Manuel González-Rosado ◽  
Luis Parras-Alcántara
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Quality ◽  
Management Practices ◽  
Soil Management ◽  
Olive Grove ◽  
No Tillage ◽  
Short Term ◽  
Degradation Degree

The short- and medium—long-term effects of management and hillside position on soil organic carbon (SOC) changes were studied in a centenary Mediterranean rainfed olive grove. One way to measure these changes is to analyze the soil quality, as it assesses soil degradation degree and attempts to identify management practices for sustainable soil use. In this context, the SOC stratification index (SR-COS) is one of the best indicators of soil quality to assess the degradation degree from SOC content without analyzing other soil properties. The SR-SOC was calculated in soil profiles (horizon-by-horizon) to identify the best soil management practices for sustainable use. The following time periods and soil management combinations were tested: (i) in the medium‒long-term (17 years) from conventional tillage (CT) to no-tillage (NT), (ii) in the short-term (2 years) from CT to no-tillage with cover crops (NT-CC), and (iii) the effect in the short-term (from CT to NT-CC) of different topographic positions along a hillside. The results indicate that the SR-SOC increased with depth for all management practices. The SR-SOC ranged from 1.21 to 1.73 in CT0, from 1.48 to 3.01 in CT1, from 1.15 to 2.48 in CT2, from 1.22 to 2.39 in NT-CC and from 0.98 to 4.16 in NT; therefore, the soil quality from the SR-SOC index was not directly linked to the increase or loss of SOC along the soil profile. This demonstrates the time-variability of SR-SOC and that NT improves soil quality in the long-term.

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