Soil CO2 Efflux Research Articles

Tracing Magma Migration at Mt. Etna Volcano during 2006–2020, Coupling Remote Sensing of Crater Gas Emissions and Ground Measurement of Soil Gases

The geochemical monitoring of volcanic activity today relies largely on remote sensing, but the combination of this approach together with soil gas monitoring, using the appropriate parameters, is still not widely used. The main purpose of this study was to correlate data from crater gas emissions with flank emissions of soil gases at Mt. Etna volcano from June 2006 to December 2020. Crater SO2 fluxes were measured from fixed stations around the volcano using the DOAS technique and applying a modeled clear-sky spectrum. The SO2/HCl ratio in the crater plume was measured with the OP-FTIR technique from a transportable instrument, using the sun as an IR source. Soil CO2 efflux coupled with the 220Rn/222Rn activity ratio in soil gases (named SGDI) were measured at a fixed monitoring site on the east flank of Etna. All signals acquired were subject both to spectral analysis and to filtering of the periodic signals discovered. All filtered signals revealed changes that were nicely correlated both with other geophysical signals and with volcanic eruptions during the study period. Time lags between parameters were explained in terms of different modes of magma migration and storage inside the volcano before eruptions. A comprehensive dynamic degassing model is presented that allows for a better understanding of magma dynamics in an open-conduit volcano.

Soil CO2 fluxes measured in the Acoculco Geothermal System, Mexico: Baseline emissions from a long-term prospection programme

The Acoculco Caldera Complex is considered a promissory hidden high-temperature geothermal system in Mexico. To support the geothermal prospection of this anomalous area, a comprehensive programme of soil CO2 flux measurements was performed. A long-term measurement programme was conducted to determine the baseline of natural soil CO2 effluxes. Significant efforts were devoted both to measuring the CO2 fluxes between 2015 and 2022 and interpreting their origin. Eighteen soil gas surveys of CO2 were carried out by using the accumulation chamber method. >1200 diffuse CO2 fluxes were measured in six different areas of the Acoculco Caldera. Two areas (Los Azufres and Alcaparrosa) exhibited cold degassing sites, acid-sulphate springs, and gas bubbling in surface water bodies. The soil CO2 fluxes ranged from 1 to 26,000 g m−2 d−1, whereas lower fluxes <29 g m−2 d−1 were determined as the degassing baseline. A total CO2 output of 492 t d−1 km−1 was estimated using an integrated SGS-GSA approach, where the highest total soil CO2 fluxes were obtained for Alcaparrosa (299 t d−1 km−2) compared with Los Azufres (164 t d−1 km−2), and Surroundings (29 t d−1 km−2). Such results agree well with those values measured in other worldwide volcanic and active geothermal ecosystems. The range of CO2 isotopic composition values from −28.83 ‰ to −3.11 ‰, together with their statistical distribution, suggests multiple CO2 production sources feeding soil degassing. The combined interpretation of flux and isotopic data allowed us to identify two distinct gas sources: endogenous and biogenic. The present study highlights the importance of using soil CO2 monitoring to determine baseline emissions at the early exploration stage of geothermal systems.

Carbon stocks and effluxes in mangroves converted into aquaculture: a case study from Banten province, Indonesia

Aquaculture is one of the main drivers of mangrove loss across Southeast Asian countries. The conversion of mangroves to aquaculture generates substantial loss of carbon stocks and reduces carbon storage capacity. Here, we present total ecosystem carbon stocks (TECS), carbon dioxide (CO2) and methane (CH4) effluxes obtained from mangrove forests (fringe and interior mangroves), silvofishery aquaculture ponds (dense and sparse mangroves), and non-silvofishery aquaculture ponds in Sawah Luhur, Banten, Indonesia. We found no significant difference in TECS across five land uses, ranging from 261 ± 14 Mg C ha-1 in non-silvofishery ponds to 574 ± 119 Mg C ha-1 in fringe mangroves. Most of these stocks were found in the soil carbon pool (87%) in fringe and interior mangroves. However, the conversion of mangroves to aquaculture ponds resulted in soil carbon loss from -6% to 60%. The highest soil CO2 effluxes during dry and wet seasons were observed in interior mangroves (151 ± 12 mg CO2 m-2 h-1). The highest soil CH4 effluxes were found in fringe mangroves with 0.13 ± 0.04 mg CH4 m-2 h-1. The highest aquatic CO2 and CH4 effluxes were found in dense silvofishery ponds, at 118 ± 7 mg CO2 m-2 h-1 and 0.38 ± 0.04 mg CH4 m-2 h-1, respectively. Our findings suggest that land use that includes mangroves (i.e., mangrove forest and/or silvofishery ponds) tends to have higher carbon stocks, soil, and aquatic CO2 and CH4 effluxes, compared to aquaculture ponds without mangroves. It is therefore crucial to maintain mangroves for natural carbon capture and storage through carbon stock enhancement.

Fire Impacts on the Soil Metabolome and Organic Matter Biodegradability.

Global wildfire activity has increased since the 1970s and is projected to intensify throughout the 21st century. Wildfires change the composition and biodegradability of soil organic matter (SOM) which contains nutrients that fuel microbial metabolism. Though persistent forms of SOM often increase postfire, the response of more biodegradable SOM remains unclear. Here we simulated severe wildfires through a controlled "pyrocosm" approach to identify biodegradable sources of SOM and characterize the soil metabolome immediately postfire. Using microbial amplicon (16S/ITS) sequencing and gas chromatography-mass spectrometry, heterotrophic microbes (Actinobacteria, Firmicutes, and Protobacteria) and specific metabolites (glycine, protocatechuate, citric cycle intermediates) were enriched in burned soils, indicating that burned soils contain a variety of substrates that support microbial metabolism. Molecular formulas assigned by 21 T Fourier transform ion cyclotron resonance mass spectrometry showed that SOM in burned soil was lower in molecular weight and featured 20 to 43% more nitrogen-containing molecular formulas than unburned soil. We also measured higher water extractable organic carbon concentrations and higher CO2 efflux in burned soils. The observed enrichment of biodegradable SOM and microbial heterotrophs demonstrates the resilience of these soils to severe burning, providing important implications for postfire soil microbial and plant recolonization and ecosystem recovery.

Soil CO2 emission and stable isotopes (δ13C, δ18O) of CO2 and calcites reveal the fluid origin and thermal energy in the supercritical geothermal system of Krafla, Iceland

The Krafla geothermal system is located within a volcanic center that periodically erupts basaltic lavas, and has recently attracted an economic interest due to supercritical fluids forming near a shallow magma intrusion (∼ 2 km depth). Here, we discuss new soil CO2 flux and stable isotope data of the CO2 efflux (δ13C) and hydrothermal calcites (δ13C, δ18O) of drill cuttings to estimate both the current magmatic outgassing from soils and the thermal flows in the geothermal system. Soil CO2 emission is controlled by tectonics, following the NNE-SSW fissure swarm direction and a WSW-ENE trend, and accounts for ∼62.5 t d−1. While the δ18O of the H2O in equilibrium with deep calcites is predominantly meteoric, both the δ13C of the soil CO2 efflux and of the fluids from which calcite precipitated have a clear magmatic origin, overlapping the δ13C estimated for the Icelandic mantle (−2.5 ± 1.1 ‰). Estimates based on the soil CO2 emission from the southern part of the system show that these fluxes might be sustained by the ascent and depressurization of supercritical fluids with a thermal energy of ∼800 MW. Such significant amount of energy might reach 1.5 GW if supercritical conditions extended below the whole investigated area. Finally, we report an increase in the soil CO2 emission of about 3 times with respect to 14 years ago, likely due to recent changes in the fluid extracted for power production or magmatic activity. Pairing the soil CO2 emission with stable isotopes of the efflux and calcite samples has important implications for both volcano monitoring and geothermal exploration, as it can help us to track magmatic fluid upflows and the associated thermal energy.

Heterogeneity of soil CO2 efflux from local parks across an urban landscape

ContextThe soil-atmosphere carbon exchange is an important component of the carbon cycle; however, dynamics of CO2 fluxes from urban landscapes are particular complicated and poorly understood due their heterogeneity.ObjectivesThe objectives of this study were to examine the total and temporal variation in CO2 flux from wooded and turfgrass areas of local parks in different part of town and identify the biophysical characteristics and landscape level factors that contribute to CO2 flux spatiotemporal variance in urban greenspaces.MethodsWe characterized the soil CO2 fluxes, temporal variation, and response to soil temperature from five parks under uniform management of a medium-sized town in southwestern Virginia, USA. We measured site scale characteristics (soil properties, tree cover) as well as the urbanicity of the surrounding land (land cover composition, population).ResultsSoil total nitrogen, soil temperature, and bulk density explained approximately 70% variation in the annual CO2 flux across the five parks. Diurnal, weekly, and seasonal CO2 fluxes were primarily related to changing soil temperature and differed between the turfgrass and wooded areas. Contrary to predictions that increased urbanicity around parks would increase soil temperature and CO2 fluxes, both CO2 and soil temperature of turfgrass were higher at parks located on town edges compared to parks in the center.ConclusionsIn sum, this study indicates that soil nitrogen and compaction, urbanicity, and the resulting site-scale structure of vegetation have a strong influence on temperature dependent biogeochemical processes like CO2 efflux.

Long-Term Patterns in Forest Soil CO2 Flux in a Pacific Northwest Temperate Rainforest

Soil CO2 efflux (Fs) plays an important role in forest carbon cycling yet estimates of Fs can remain unconstrained in many systems due to the difficulty in measuring Fs over long time scales in natural systems. It is important to quantify seasonal patterns in Fs through long-term datasets because individual years may show patterns that are not reflective of long-term averages. Additionally, determining predictability of net patterns in soil carbon flux based on environmental factors, such as moisture and temperature, is critical for appropriately modeling forest carbon flux. Ecosystems in moderate climates may have strong CO2 efflux even during winter, and so continuous quantification of annual variability is especially important. Here, we used a 2008–2023 dataset in a lowland temperate forest ecosystem to address two main questions: (1) What are the seasonal patterns in Fs in a highly productive temperate rainforest? (2) How is average Fs across our study area predicted by average coincident temperature, soil moisture and precipitation totals? Data showed clear seasonality where Fs values are higher in summer. We also find Fs across our measurement network was predicted by variation in abiotic factors, but the interaction between precipitation/moisture and temperature resulted in greater complexity. Specifically, in spring a relatively strong relationship between air temperature and Fs was present, while in summer the relationship between temperature and Fs was flat. Winter and autumn seasons showed weak positive relationships. Meanwhile, a negative relationship between precipitation and Fs was present in only some seasons because most precipitation falls outside the normal growing season in our study system. Our data help constrain estimates of soil CO2 fluxes in a temperate rainforest ecosystem at ~14–20 kg C ha−1 day−1 in summer and autumn, and 6.5–10.5 kg C ha−1 day−1 in winter and spring seasons. Together, estimates suggest this highly productive temperate rainforest has annual soil-to-atmosphere fluxes of CO2 that amount to greater than 4.5 Mg C ha−1 year−1. Sensitivity of such fluxes to regional climate change will depend on the balance of Fs determined by autotrophic phenological responses versus heterotrophic temperature and moisture sensitivity. Relatively strong seasonal variation coupled with comparatively weak responses to abiotic variables suggest Fs may be driven largely by seasonal trends in autotrophic respiration. Accordingly, plant and tree responses to climate may have a stronger effect on Fs in the context of climate change than temperature or moisture changes alone.

Total Soil CO2 Efflux from Drained Terric Histosols.

Histosols cover about 8-10% of Lithuania's territory and most of this area is covered with nutrient-rich organic soils (Terric Histosols). Greenhouse gas (GHG) emissions from drained Histosols contribute more than 25% of emissions from the Land Use, Land Use Change and Forestry (LULUCF) sector. In this study, as the first step of examining the carbon dioxide (CO2) fluxes in these soils, total soil CO2 efflux and several environmental parameters (temperature of air and topsoil, soil chemical composition, soil moisture, and water table level) were measured in drained Terric Histosols under three native forest stands and perennial grasslands in the growing seasons of 2020 and 2021. The drained nutrient-rich organic soils differed in terms of concentrations of soil organic carbon and total nitrogen, as well as soil organic carbon and total nitrogen ratio. The highest rate of total soil CO2 efflux was found in the summer months. Overall, the rate was statistically significant and strongly correlated only with soil and air temperature. A trend emerged that total soil CO2 efflux was 30% higher in perennial grassland than in forested land. Additional work is still needed to estimate the net CO2 balance of these soils.

Beyond a deterministic representation of the temperature dependence of soil respiration

Soil CO2 efflux represents a complex interplay of biological and physical processes that result in the production and transfer of CO2 from soils to the atmosphere. Temperature has been widely recognized as a critical factor regulating soil CO2 efflux and is commonly utilized in deterministic empirical models to predict this important flux for the carbon cycle. This study introduces the Bernstein copula-based cosimulation (BCC) as a data-driven probabilistic approach to model the temperature-soil CO2 efflux relationship. The BCC accounts for the joint probability distribution and temporal dependence of soil CO2 efflux, which are often overlooked in deterministic models. The BCC was implemented as a proof of concept using two years of data on soil CO2 efflux conditioned by soil temperature in a temperate forest. The BBC accurately reproduced the original probability distribution, temporal dependency, and temperature-soil CO2 efflux relationship. Our findings show that a deterministic method, such as the commonly employed exponential relationship between soil CO2 efflux and temperature, is limited for comprehensively capturing the intricate nature of the temperature-soil CO2 efflux relationship. This is due to the confounding and interacting effects of environmental drivers beyond temperature, which are not fully accounted for in such a deterministic approach. Furthermore, the BCC revealed that the probability density between the joint cumulative probability of temperature and soil CO2 efflux is not constant, which raises the concern that deterministic approaches introduce incorrect assumptions for estimating temperature-soil CO2 relationship. In conclusion, we propose that probabilistic approaches hold promise for effectively depicting dependency relationships for soil CO2 efflux modeling, and for improving predictions of the effects of weather variability and climate change.

Estimation of annual soil CO2 efflux under the erosion and deposition conditions by measuring and modeling its respiration rate in southern China

Soil respiration (Rs) is a crucial ecological process of carbon (C) cycling in the terrestrial ecosystems, and soil erosion has a significant impact on its C budget and balance. However, the variations of Rs rate and their CO2 efflux induced by erosion are currently poorly understood. To this end, four landscape positions (top, up, middle and toe) with different erosional and depositional characteristics were selected on a typical eroded slope in southern China to conduct field experiments, aiming to explore the effects of erosion and deposition on Rs among various sites. From March 2021 to February 2022, the in-situ Rs were measured using an automated soil respiration system, together with soil temperature at 5 cm depth (Ts5) and water content at 10 cm depth (SWC10). We initially constructed various Rs models across a one-year period, based on its relationships with Ts5 and SWC10. Subsequently, the seasonal changes of Rs at different erosional sites were simulated by the optimum models, and their annual CO2 fluxes were further estimated. The results showed that Rs rates at all sites displayed a bimodal seasonal pattern, with the highest values in May and August. And the measured Rs of the eroding and depositional sites were 0.05–7.71 and 1.47–13.03 μmol m−2 s−1, respectively. Also, remarkably higher Ts5 and SWC10 were observed in depositional sites versus the eroding sites (P < 0.05). Additionally, Rs rates at all sites were positively correlated with SOC and Ts5, but negatively correlated with SWC10. Herein, Rs models to single- and double-variable were established at different positions, and we found that the fitted R2 and AIC differed on various sites, primarily in erosional and depositional sites. Furthermore, through the best-fitting models (higher R2 and lowest AIC) we screened, the average Rs values of 3.03 and 4.46 μmol m−2 s−1 were quantitatively estimated for the eroding and depositional sites, respectively. Finally, it could be further assessed that the mean annual soil CO2–C efflux of eroded site (1104.14 g m−2) was significantly lower than that of depositional site (1629.46 g m−2). These findings highlighted the effect of erosion and deposition on Rs, which will facilitate a better understanding of C cycling in terrestrial ecosystems.

Climate warming suppresses abundant soil fungal taxa and reduces soil carbon efflux in a semi-arid grassland.

Soil microorganisms critically affect the ecosystem carbon (C) balance and C-climate feedback by directly controlling organic C decomposition and indirectly regulating nutrient availability for plant C fixation. However, the effects of climate change drivers such as warming, precipitation change on soil microbial communities, and C dynamics remain poorly understood. Using a long-term field warming and precipitation manipulation in a semi-arid grassland on the Loess Plateau and a complementary incubation experiment, here we show that warming and rainfall reduction differentially affect the abundance and composition of bacteria and fungi, and soil C efflux. Warming significantly reduced the abundance of fungi but not bacteria, increasing the relative dominance of bacteria in the soil microbial community. In particular, warming shifted the community composition of abundant fungi in favor of oligotrophic Capnodiales and Hypocreales over potential saprotroph Archaeorhizomycetales. Also, precipitation reduction increased soil total microbial biomass but did not significantly affect the abundance or diversity of bacteria. Furthermore, the community composition of abundant, but not rare, soil fungi was significantly correlated with soil CO2 efflux. Our findings suggest that alterations in the fungal community composition, in response to changes in soil C and moisture, dominate the microbial responses to climate change and thus control soil C dynamics in semi-arid grasslands.

Management impacts on whole soil warming responses of CO2 production and efflux in temperate climate

Although global warming has the potential to increase soil CO2 efflux, the magnitude of these changes are uncertain, as CO2 production rates in deep soil are poorly constrained. In particular, management effects on the warming responses at depth are unknown. Here, we conducted an in-situ soil warming experiment down to 2.0-m depth in an agricultural Cambisol to study the warming responses of (1) CO2 production across different depths and (2) CO2 efflux from topsoil in different seasons under two management practices. To this end, we measured whole-soil profile water content, CO2 production and CO2 efflux under continuous grassland and cropland in response to elevated temperature (+4°C).Warming decreased soil water content for both management practices. We found contrasting warming effects on surface CO2 efflux, depending on season and land management practices. Subsoil CO2 production was more sensitive to warming than topsoil CO2 production with grassland subsoil showing a greater warming response than cropland subsoil. Topsoil CO2 production decreased in response to warming in the cropland but not the grassland. We concluded that warming responses of CO2 production and efflux are affected by soil management practices. Their effect on biological processes (roots and microbial activity) and factors affecting gas diffusivity, such as soil water availability and soil physical organization need to be assessed to model warming effects on carbon exchange between soil and the atmosphere in agricultural systems.

Effects of crop residue incorporation on soil‐biodegradable mulch film degradation in a broccoli‐sorghum rotation system

AbstractSoil‐biodegradable mulch films are designed to be incorporated into the soil at the end of the crop cycle, to be degraded by soil microorganisms. Despite growing scientific interest, open‐field studies about the fate of these mulch films in soils are rare, with most research conducted in laboratories. We performed an open‐field trial to evaluate the effects of soil incorporation of both a combining a commercial soil‐biodegradable mulch film and broccoli and sorghum crop residues over two cropping seasons. The mulch film was sampled after broccoli harvesting and placed inside mesh bags that were buried horizontally or vertically at different depths. Film biodegradation was assessed by direct (CO2 emissions) and indirect indicators (film mass and area loss). Three experiments were conducted to evaluate (a) how incorporating crop residues affect mulch film degradation; (b) temporal changes of soil microbial activity after the incorporation of crop residues and mulch films; and (c) possible bias in the measurement of soil CO2 emissions due to horizontal vs. vertical mesh bag orientation. Incorporation of crop residues enhanced mulch film degradation and increased the soil esterase activity. However, abundance of soil fungi and bacteria in bulk soil was not increased by mulch film presence. Mesh bag orientation did not alter the soil CO2 efflux or affect the degradation degree of mulch films. Film in mesh bags buried at 10–15 cm depth showed greater degradation than those buried at 0–5 cm. Further in‐field studies are necessary to evaluate the effects of soil incorporation of residue from different crops and impacts of other associated management practices such as various soil tillage regimes.

Soil carbon mineralization, enzyme activities, and crop residue decomposition under varying soil moisture regimes

AbstractIn the Lower Mississippi River Basin, farmlands are flooded in late fall and winter by impeding drainage to provide a habitat for migratory birds stopover. A laboratory incubation study was conducted to study the influence of temporary wetting of these soils on carbon (C) and nitrogen (N) mineralization from residue decomposition. Surface soils (0–15 cm) were collected from fields with clay and silty clay loam soils. Both soils were incubated with five crop residues—corn (Zea mays), soybean (Glycine max), cotton (Gossypium hirsutum), sorghum (Sorghum bicolor), and sweet potato (Ipomea batatus)—at 50% and 100% water holding capacity (WHC). Soil carbon dioxide (CO2) efflux was measured during 74 days of incubation. Soil moisture had the largest effect on soil CO2 efflux and most of the enzyme activities followed by residue and soil type. Cumulative soil CO2 efflux was reduced by 46% at 100% WHC compared to 50% WHC. Clay soil had higher cumulative CO2 efflux, aryl sulfatase, aryl phosphatase, and β‐N‐acetyl glucose aminidase activities than silty clay loam soil. Residue type had the largest effect on post‐incubation soil inorganic‐N, remaining biomass, and residue C and residue N. Sweet potato residue had the lowest remaining biomass, significantly lower than cotton, corn, and sorghum, but statistically similar to soybean. After incubation, residue N concentration had a positive association with cumulative CO2 efflux and a negative association with remaining residue biomass percentage. Winter flooding might limit the loss of soil C as CO2 depending on the crops grown and soil type.

Carbon dynamics as a function of soil moisture following repeated wet-dry cycles in irrigated soils

Drying-rewetting cycles are ubiquitous across natural and managed ecosystems. These cycles are known to mobilize carbon (C) in soils producing dramatic pulses in microbial respiration. While many factors contribute to these pulses, the drying-rewetting history of soils affecting carbon emissions remains unclear, especially in irrigated soils where soil moisture fluctuations are more repetitive and/or frequent than natural, seasonally influenced soils. To understand the controls of repeated wet-up and dry down effects on agricultural soils, we used a systems approach to examine the cross section of a furrow irrigated orchard to delineate soil C dynamics. Specifically, we compared two contrasting water regimes, (1) soils temporarily but repeatedly inundated during water delivery (i.e., furrows) and (2) soils at the base of trees (i.e., berms) that only receive water during precipitation events in a semi-arid Mediterranean climate. Overall, our findings show that the heterogeneous landscape of a furrow irrigated field results in two separate systems within the field scale in gaseous release of C as CO2, microbial selectivity of substrates, and mechanisms for C stabilization. By monitoring soil moisture as a function of depth for over two years, our results reveal that furrow soils undergo dramatic wet-dry cycles, while moisture within the berm is relatively constant. We were able to capture the distinct heterogeneity of soil moisture changes within the furrow and berm soils by continuously monitoring CO2 flux throughout water input events in both the wet and dry season. Soil CO2 efflux is suppressed upon irrigation within furrows, while carbon oxidation in berm soils exhibits pore-connectivity limitations that result in lower fluxes when dry. Solid phase soil C speciation determined by C 1s NEXAFS demonstrated C of higher aromaticity remained in furrow soil compared to berm soils. Microbial community analysis shows significantly different communities reside within berm and furrow soils, where furrow soils support more anaerobic metabolisms and spore-formers while berm soils have relatively higher abundance of aerobic microbes capable of degrading larger, more complex C compounds. Our findings show that water regime (periodic inundation vs episodic rainfall) controlling rewetting history can greatly differentiate C respiration within managed soils.

Short-term warming-induced increase in non-microbial carbon emissions from semiarid abandoned farmland soils

Soil warming is expected to accelerate microbial carbon (C) degradation, increasing carbon dioxide (CO2) emissions. This process greatly contributes to global warming. To validate this positive feedback loop in semiarid restored ecosystems, we examined the effects of 2 years of open-top chamber warming on soil CO2 efflux (soil respiration) and microbial metabolic characteristics in abandoned farmland on the Chinese Loess Plateau. Soil warming of 1.3 °C above ambient at 10 cm depth significantly stimulated CO2 emissions by 40.5 %. Despite short-term warming alleviating the C (energy) limitation on microbial activity, no substantial differences in microbial C use efficiency or biomass turnover rate were noted compared to those in the control. Importantly, we found little evidence that warming altered the expression levels of carbohydrate metabolism genes annotated using the eggNOG, KEGG, and CAZy databases. All expressed genes targeting the degradation of diverse carbonaceous components were assigned to bacterial taxa unaffected by warming. Therefore, short-term warming stimulated soil CO2 emissions from non-microbial sources but did not drive the abandoned farmland in the reverse direction to a C source. Our findings highlight the importance of conducting long-term comparisons of microbial metabolic profiles and soil respiration components to elucidate the mechanisms underlying changes in C-cycling in ecosystems that have undergone restoration and experienced warming.

Monitoring of Seasonal Under-Vine CO2 Effluxes in a Vineyard under Different Fertilization Practices

Soil CO2 efflux is a pivotal component of agro-ecosystem C budgets. It is considered a proxy indicator of biological activity and a descriptor of soil quality that is strongly linked to agricultural soil management. We investigated the effects of soil fertilization practices (organo-mineral (OMN) versus chemical (C)) on soil under-vine CO2 efflux (TSR) in an Italian rainfed vineyard (cv Chardonnay). The TSR was measured using the chamber technique as follows: a close multi-chamber system (prototype) was placed under a vine. Data (CO2, temperature, and moisture) were acquired hourly during two consecutive years (2021 and 2022) from flowering to berry ripening. Physical–hydrological soil parameters were determined, and the seasonal trends of the TSR, soil temperature, and soil moisture were assessed. The TSR measurements fluctuated for the 2021 season, ranging from 1.03 to 1.97 µmol CO2∙m−2∙s−1 for the C treatment, while for the OMN treatment, the TSR measurements ranged from 1.24 to 1.71 µmol CO2∙m−2∙s−1. Extreme weather conditions (2022) highlighted the differences between the two agronomical practices, and a decoupling was found between the TSR and the soil water content, with the TSR being controlled primarily by the soil temperature. At the daily scale, the findings showed that the TSR reached its minimum in the early morning hours (5:00–8:00). The results promote organic–mineral nutrition as an improved practice for soil carbon storage (restoration of the organic fraction) by reducing the TSR, permitting the preservation of soil quality and stabilizing the hydrological traits by preserving the biotic activities.

Temporal patterns of fine‐root dynamics have little influence on seasonal soil CO2 efflux in a mixed, mesic forest

AbstractAmong the contributors to soil CO2 efflux, there remains uncertainty about the contribution of root activity to the overall soil efflux. Soil water and temperature frequently have been used to predict a large portion of the variation in soil CO2 efflux. We hypothesized that fine‐root dynamics explain most of the remaining variability in soil CO2 efflux that cannot be explained by soil temperature and water content. We anticipated that seasonal increases in root production, mortality via decomposition, and standing crop would result in corresponding increases in soil CO2 efflux. We tested our hypotheses by collecting and analyzing two years of minirhizotron and soil chamber CO2 flux data from plots distributed throughout the Shale Hills Catchment of the Susquehanna‐Shale Hills Critical Zone Observatory in Central Pennsylvania, USA. Here we showed that: (1) seasonal fluctuations in fine‐root dynamics yielded only a very small increase in the predictability of soil CO2 efflux; (2) fine‐root mortality effects on soil CO2 efflux were strongly tied to soil temperature; (3) fluctuations in fine‐root presence or standing mass independent of temperature and moisture had little effect on soil CO2 efflux; and (4) new fine‐root length and root length mortality had limited impacts on soil CO2 efflux rates. We conclude that, at least in temperate forests on rocky soils, characterizing fine‐root dynamics may provide only limited improvement in the estimation of soil CO2 efflux.

Evaluation of soil CO2 efflux and its influence factors in a revegetated area in Tengger Desert, NW China

Evaluation of soil CO2 efflux and its influence factors in a revegetated area in Tengger Desert, NW China

Recycled Waste Leaf Litter Pots Exhibit Excellent Biodegradability: An Experimental Analysis

The growth of the gardening kit market could result in the increased wasting of nursery pots, which are usually made of plastic. Replacing these pots with biodegradable pots made from green waste could have benefits for climate mitigation, the circular economy, and the greenness of gardening. To address this, we introduce a prototype recycled waste leaf litter (RWLL) nursery pot. Via an incubation experiment over 90 d, we examined their biodegradability and effects on microbial enzyme activity and inorganic nitrogen concentration, comparing them with commercially available biodegradable pots, namely peat–paper mixture pots (also known as Jiffypots®) and coco-coir pots. The effects of pot thickness were tested. Based on mass loss during incubation and on soil CO2 efflux, the RWLL pots exhibited excellent biodegradability, regardless of their thickness, with decomposition rates and soil CO2 efflux 1.5–6 times greater than other biodegradable pots. Biodegradability, extracellular enzyme activity, and soil inorganic nitrogen content were not affected by RWLL pot thickness or by the presence or absence of a plant in the soil. Unlike in natural ecosystems, leaf litter is treated as waste in urban green spaces, and its decomposition into soil organic matter is prevented. Creating plant pots from leaf litter enhances soil quality, reduces atmospheric carbon emissions, and satisfies the desire of gardeners for greenness.