scholarly journals Shifting mineral and redox controls on carbon cycling in seasonally flooded mineral soils

2019 ◽  
Vol 16 (13) ◽  
pp. 2573-2589 ◽  
Author(s):  
Rachelle E. LaCroix ◽  
Malak M. Tfaily ◽  
Menli McCreight ◽  
Morris E. Jones ◽  
Lesley Spokas ◽  
...  
Keyword(s):  
Climate Change ◽  
Redox Potential ◽  
Organic Compounds ◽  
Root Biomass ◽  
Wetland Soils ◽  
Co2 Efflux ◽  
Seasonal Flooding ◽  
Upland Soils ◽  
Mineral Soils ◽  
Seasonally Flooded

Abstract. Although wetland soils represent a relatively small portion of the terrestrial landscape, they account for an estimated 20 %–30 % of the global soil carbon (C) reservoir. C stored in wetland soils that experience seasonal flooding is likely the most vulnerable to increased severity and duration of droughts in response to climate change. Redox conditions, plant root dynamics, and the abundance of protective mineral phases are well-established controls on soil C persistence, but their relative influence in seasonally flooded mineral soils is largely unknown. To address this knowledge gap, we assessed the relative importance of environmental (temperature, soil moisture, and redox potential) and biogeochemical (mineral composition and root biomass) factors in controlling CO2 efflux, C quantity, and organic matter composition along replicated upland–lowland transitions in seasonally flooded mineral soils. Specifically, we contrasted mineral soils under temperature deciduous forests in lowland positions that undergo seasonal flooding with adjacent upland soils that do not, considering both surface (A) and subsurface (B and C) horizons. We found the lowland soils had lower total annual CO2 efflux than the upland soils, with monthly CO2 efflux in lowlands most strongly correlated with redox potential (Eh). Lower CO2 efflux as compared to the uplands corresponded to greater C content and abundance of lignin-rich, higher-molecular-weight, chemically reduced organic compounds in the lowland surface soils (A horizons). In contrast, subsurface soils in the lowland position (Cg horizons) showed lower C content than the upland positions (C horizons), coinciding with lower abundance of root biomass and oxalate-extractable Fe (Feo, a proxy for protective Fe phases). Our linear mixed-effects model showed that Feo served as the strongest measured predictor of C content in upland soils, yet Feo had no predictive power in lowland soils. Instead, our model showed that Eh and oxalate-extractable Al (Alo, a proxy of protective Al phases) became significantly stronger predictors in the lowland soils. Combined, our results suggest that low redox potentials are the primary cause for C accumulation in seasonally flooded surface soils, likely due to selective preservation of organic compounds under anaerobic conditions. In seasonally flooded subsurface soils, however, C accumulation is limited due to lower C inputs through root biomass and the removal of reactive Fe phases under reducing conditions. Our findings demonstrate that C accrual in seasonally flooded mineral soil is primarily due to low redox potential in the surface soil and that the lack of protective metal phases leaves these C stocks highly vulnerable to climate change.

scholarly journals Shifting Mineral and Redox Controls on Carbon Cycling in Seasonally Flooded Soils

2018 ◽  
Author(s):  
Rachelle LaCroix ◽  
Malak Tfaily ◽  
Menli McCreight ◽  
Morris E. Jones ◽  
Lesley Spokas ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Compounds ◽  
Root Biomass ◽  
Co2 Efflux ◽  
Anaerobic Conditions ◽  
Flooded Soils ◽  
Soil C ◽  
Seasonal Flooding ◽  
C Stocks ◽  
Seasonally Flooded

Abstract. Soils contain three times the amount of carbon (C) than the atmosphere, with C turnover times ranging from centuries to millennia. Although wetland soils represent a relatively small portion of the terrestrial landscape, they account for an estimated 20–30 % of the global C reservoir. Among wetlands, seasonally flooded soils are likely the most vulnerable to increased severity and duration of droughts in response to climate change. Yet, the relative influence of associated changes in oxygen limitations, root dynamics, and mineral protection on C cycling in seasonally flooded mineral soils is largely unknown. To address this knowledge gap, we combined seasonal monitoring of soil moisture, redox potential, and CO2 efflux with a characterization of root biomass, mineralogy, C quantity and organic matter composition along upland-to-lowland transects of both top- and subsoils in temperate forested wetlands. We found that lower CO2 effluxes in lowland than upland topsoils coincided with greater total C concentrations as well as a greater abundance of high molecular weight and chemically reduced organic compounds, indicating that selective preservation of organic compounds during anaerobic periods caused C accumulation in seasonally flooded surface soils. In subsoils, however, seasonal flooding and associated anaerobic conditions did not result in soil C accumulation. Instead, total C concentrations were significantly lower in lowland than in upland subsoils. Lower soil C accumulation in seasonally flooded subsoils coincided with lower abundance of root biomass and reducible Fe phases, and relied primarily on non-reducible Al phases rather than anaerobic conditions. Combined, our results demonstrate that seasonal flooding and associated anaerobic conditions accumulate C in topsoils, but limit C accumulation in subsoils by restricting root C inputs and removing of protective Fe phases through reductive dissolution. Our findings indicate that C accrual in seasonally flooded soil is due primarily to oxygen limitations in the surface soil, and that the overall lack of mineral protection leaves these C stocks highly vulnerable to climate change.

scholarly journals Temperate Fruit Trees under Climate Change: Challenges for Dormancy and Chilling Requirements in Warm Winter Regions

Horticulturae ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 86
Author(s):  
Abdel-Moety Salama ◽  
Ahmed Ezzat ◽  
Hassan El-Ramady ◽  
Shamel M. Alam-Eldein ◽  
Sameh Okba ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Compounds ◽  
Fruit Trees ◽  
Fruit Tree ◽  
Limiting Factor ◽  
Dormancy Breaking ◽  
Warm Winter ◽  
Winter Chill ◽  
Chilling Requirements ◽  
The Tropics

Adequate chill is of great importance for successful production of deciduous fruit trees. However, temperate fruit trees grown under tropical and subtropical regions may face insufficient winter chill, which has a crucial role in dormancy and productivity. The objective of this review is to discuss the challenges for dormancy and chilling requirements of temperate fruit trees, especially in warm winter regions, under climate change conditions. After defining climate change and dormancy, the effects of climate change on various parameters of temperate fruit trees are described. Then, dormancy breaking chemicals and organic compounds, as well as some aspects of the mechanism of dormancy breaking, are demonstrated. After this, the relationships between dormancy and chilling requirements are delineated and challenging aspects of chilling requirements in climate change conditions and in warm winter environments are demonstrated. Experts have sought to develop models for estimating chilling requirements and dormancy breaking in order to improve the adaption of temperate fruit trees under tropical and subtropical environments. Some of these models and their uses are described in the final section of this review. In conclusion, global warming has led to chill deficit during winter, which may become a limiting factor in the near future for the growth of temperate fruit trees in the tropics and subtropics. With the increasing rate of climate change, improvements in some managing tools (e.g., discovering new, more effective dormancy breaking organic compounds; breeding new, climate-smart cultivars in order to solve problems associated with dormancy and chilling requirements; and improving dormancy and chilling forecasting models) have the potential to solve the challenges of dormancy and chilling requirements for temperate fruit tree production in warm winter fruit tree growing regions.

Pre and post flooding malaria parasitemia in gravid women, South East, Nigeria

2021 ◽  
Vol 2 (5) ◽  
Author(s):  
Ekwebene OC ◽  
◽  
Obidile VC ◽  
Nnamani CP ◽  
Eleje GU ◽  
...  
Keyword(s):  
Climate Change ◽  
Pregnant Women ◽  
Health Care Professionals ◽  
Malaria Parasite ◽  
P Value ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Seasonal Flooding ◽  
Vector Borne ◽  
The Relationship

The effect of global change on the incidence of vector borne diseases including malaria is of great importance. Malaria has been regarded as one of the most sensitive disease that responds fast to climate change. Pregnant women tend to have reduced immunity are more vulnerable to vector borne diseases such as malaria especially with climate change like flooding where these vectors borne diseases are endemic. To measure malaria parasitaemia in gravid women pre and post flooding and also to determine the relationship between malaria and seasonal flooding in South east Nigeria. This was a hospital-based cross-sectional study involving pregnant women aged 15- 45 years attending the antenatal clinics of two maternity centres in a rural community South east Nigeria. Malaria was determined using the thick and thick blood films. Plasmodium falciparum species was examined in this study. Chi-square was used to assess the relationship between malaria and seasonal flooding. One Hundred and fifty pregnant women were recruited for the study. The prevalence of malaria in the gravid women pre and post flooding were 60.00% and 65.30% respectively. Malaria parasite was highest in the gravid women aged 28-31 years and the primigravids. There was no statistical difference between malaria and parity. The mean parasite density in the gravid women was significantly higher post flooding than pre flooding with p-value of 0.001. There was no significant relationship between malaria parasite in gravid women and the periods of investigation. The prevalence of malaria parasite among gravid women in the study area is high regardless of the seasonal flooding. Hence, the need for adherence to malaria prophylaxis protocol by the health care professionals and increase on community health education on malaria preventive strategies.

scholarly journals Patterns of longer-term climate change effects on CO<sub>2</sub> efflux from biocrusted soils differ from those observed in the short term

2018 ◽  
Vol 15 (14) ◽  
pp. 4561-4573 ◽  
Author(s):  
Anthony Darrouzet-Nardi ◽  
Sasha C. Reed ◽  
Edmund E. Grote ◽  
Jayne Belnap
Keyword(s):  
Climate Change ◽  
Monsoon Season ◽  
Vascular Plant ◽  
Precipitation Amount ◽  
Co2 Flux ◽  
Co2 Exchange ◽  
Plant Responses ◽  
Co2 Efflux ◽  
Climate Change Effects ◽  
Altered Precipitation

Abstract. Biological soil crusts (biocrusts) are predicted to be sensitive to the increased temperature and altered precipitation associated with climate change. We assessed the effects of these factors on soil carbon dioxide (CO2) balance in biocrusted soils using a sequence of manipulations over a 9-year period. We warmed biocrusted soils by 2 and, later, by 4 ∘C to better capture updated forecasts of future temperature at a site on the Colorado Plateau, USA. We also watered soils to alter monsoon-season precipitation amount and frequency and had plots that received both warming and altered precipitation treatments. Within treatment plots, we used 20 automated flux chambers to monitor net soil exchange (NSE) of CO2 hourly, first in 2006–2007 and then again in 2013–2014, for a total of 39 months. Net CO2 efflux from biocrusted soils in the warming treatment increased a year after the experiment began (2006–2007). However, after 9 years and even greater warming (4 ∘C), results were more mixed, with a reversal of the increase in 2013 (i.e., controls showed higher net CO2 efflux than treatment plots) and with similarly high rates in all treatments during 2014, a wet year. Over the longer term, we saw evidence of reduced photosynthetic capacity of the biocrusts in response to both the temperature and altered precipitation treatments. Patterns in biocrusted soil CO2 exchange under experimentally altered climate suggest that (1) warming stimulation of CO2 efflux was diminished later in the experiment, even in the face of greater warming; and (2) treatment effects on CO2 flux patterns were likely driven by changes in biocrust species composition and by changes in root respiration due to vascular plant responses.

scholarly journals Patterns of longer-term climate change effects on CO<sub>2</sub> efflux from biocrusted soils differ from those observed in the short-term

2018 ◽  
Author(s):  
Anthony Darrouzet-Nardi ◽  
Sasha C. Reed ◽  
Edmund E. Grote ◽  
Jayne Belnap
Keyword(s):  
Climate Change ◽  
Monsoon Season ◽  
Vascular Plant ◽  
Co2 Exchange ◽  
Plant Responses ◽  
Co2 Efflux ◽  
Climate Change Effects ◽  
Altered Precipitation ◽  
The Face ◽  
Carbon Dioxide Co2

Abstract. Biological soil crusts (biocrusts) are predicted to be sensitive to the increased temperature and altered precipitation associated with climate change. We assessed the effects of these factors on soil carbon dioxide (CO2) balance in biocrusted soils using a sequence of manipulations over a nine-year period. We warmed biocrusted soils by 2 and, later, by 4 °C to better capture updated forecasts of future temperature, as well as altered monsoon-season precipitation at a site on the Colorado Plateau, USA. Within treatment plots, we used 20 automated flux chambers to monitor net soil exchange (NSE) of CO2 hourly, first in 2006–2007 and then again in 2013–2014, for a total of 39 months. Net CO2 efflux from biocrusted soils in the warming treatment increased a year after the experiment began (2006–2007). However, after 9 years and even greater warming (4 °C), results were more mixed, with a reversal of the increase in 2013 (i.e., controls showed higher net CO2 efflux than treatment plots) and with similarly high rates in all treatments during 2014, a wet year. Over the longer-term, we saw evidence of reduced photosynthetic capacity of the biocrusts in response to both the temperature and altered precipitation treatments. Patterns in biocrusted soil CO2 exchange under experimentally altered climate suggest that (1) warming effects were diminished later in the experiment, even in the face of larger warming and (2) likely drivers of the treatment effects were changes in biocrust species composition and changes in root respiration due to vascular plant responses.

scholarly journals Significance of soil respiration from biological activity in the degradation processes of different types of organic matter

2020 ◽  
Vol 1 (2) ◽  
pp. 171-179
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Moisture ◽  
Soil Respiration ◽  
Soil Temperature ◽  
Temperature Sensitivity ◽  
Soil Co2 Efflux ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Total Soil

Soil respiration is a major component of global carbon cycle. Therefore, it is crucial to understand the environmental controls on soil respiration for evaluating potential response of ecosystems to climate change. In a temperate deciduous forest (located in Northern-Hungary) we added or removed aboveground and belowground litter to determine total soil respiration. We investigated the relationship between total soil CO2 efflux, soil moisture, and soil temperature. Soil CO2 efflux was measured at each plot using soda-lime method. Temperature sensitivity of soil respiration (Q10) was monitored via measuring soil temperature on an hourly basis, while soil moisture was determined monthly. Soil respiration increased in control plots from the second year after implementing the treatment, but results showed fluctuations from one year to another. The effect of doubled litter was less significant than the effect of removal. Removed litter and root inputs caused substantial decrease in soil respiration. We found that temperature was more influential in the control of soil respiration than soil moisture. In plots with no litter Q10 varied in the largest interval. For treatment with doubled litter layer, temperature sensitivity of CO2 efflux did not change considerably. The effect of increasing soil temperature is more conspicuous to soil respiration in litter removal treatments since lack of litter causes greater irradiation. When exclusively leaf litter was considered, the effect of temperature on soil respiration was lower in treatments with added litter than with removed litter. Our results reveal that soil life is impacted by the absence of organic matter, rather than by an excess of organic matter. Results of CO2 emission from soils with different organic matter content can contribute to sustainable land use, considering the changed climatic factors caused by global climate change.

Monitoring the influence of toxic compounds on microbial denitrifying biofilm processes

2003 ◽  
Vol 47 (5) ◽  
pp. 211-216 ◽  
Author(s):  
J. Li ◽  
P.L. Bishop
Keyword(s):  
Organic Compound ◽  
Redox Potential ◽  
Organic Compounds ◽  
Acid Orange 7 ◽  
Toxic Compounds ◽  
Acid Orange ◽  
Anoxic Layer ◽  
Anaerobic Zone ◽  
Microelectrode Measurements

Microelectrode measurements were conducted to obtain nitrate, pH and redox potential profiles within anoxic denitrifying biofilms. The influence of a toxic organic compound (acid orange 7) on biofilm microprofiles was also monitored using microelectrodes. The data provide evidence that the denitrifying biofilms were stratified into an anoxic layer and an anaerobic layer. The anaerobic zone might provide a niche for the biodegradation of recalcitrant organic compounds in biofilms. It was found that acid orange 7 and its biodegradation byproducts had only a slight impact on biofilm nitrate, pH and redox potential profiles.

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