Sensitivity Of Soil Respiration Research Articles

Data underlying publication: Ambient precipitation determines the sensitivity of soil respiration to precipitation treatments in a marsh

Data underlying publication: Ambient precipitation determines the sensitivity of soil respiration to precipitation treatments in a marsh

Legacy effect of constant and diurnally oscillating temperatures on soil respiration and microbial community structure

AbstractLaboratory incubation studies evaluating the temperature sensitivity of soil respiration often use measurements of respiration taken at a constant incubation temperature from soil that has been pre‐incubated at the same constant temperature. However, such constant temperature incubations do not represent the field situation where soils undergo diurnal temperature oscillations. We investigated the legacy effects of constant and diurnally oscillating temperatures on soil respiration and soil microbial community composition. A grassland soil from the United Kingdom was either incubated at a constant temperature of 5°C, 10°C, or 15°C, or diurnally oscillated between 5°C and 15°C. Soil CO2 flux was measured by temporarily moving incubated soils from each of the above‐mentioned treatments to 5°C, 10°C or 15°C, such that soils incubated under every temperature regime had CO2 flux measured at each temperature. We hypothesised that, irrespective of measurement temperature, CO2 emitted from the 5°C to 15°C oscillating incubation would be most like the soil incubated at 10°C. The results showed that both incubation and measurement temperatures separately influence soil respiration. Oscillations between 5°C and 15°C resulted in significantly greater CO2 flux than constant incubations at 10°C or 5°C but were not significantly different from the 15°C incubation. The greater CO2 flux from soils previously incubated at 15°C, or oscillating between 5°C and 15°C, coincided with a depletion of dissolved organic carbon and a shift in the phospholipid fatty acid profile of the soil microbial community, consistent with stress associated with substrate depletion and microbial starvation when incubated at higher temperatures. Our results suggest that daily maximum temperatures are more important than daily minimum or daily average temperatures when considering the response of soil respiration to the diurnally asymmetric warming that is expected to occur as a result of climate change.

Carbon inputs regulate the temperature sensitivity of soil respiration in temperate forests

Carbon inputs regulate the temperature sensitivity of soil respiration in temperate forests

Temperature Sensitivity of Soil Respiration in Two Temperate Forest Ecosystems: The Synthesis of a 24-Year Continuous Observation

Soil respiration (SR) is one of the largest fluxes in the global carbon cycle. The temperature sensitivity of SR (often termed as Q10) is a principal parameter for evaluating the feedback intensity between soil carbon efflux and global warming. The present study aimed to estimate the seasonal and interannual dynamics of the temperature sensitivity of SR based on a long-term 24-year series of measurements in two temperate forest ecosystems in European Russia. The study was conducted in a mature mixed forest with sandy Entic Podzol and in a secondary deciduous forest with loamy Haplic Luvisol. The SR rate was measured continuously from December 1997 to November 2021 at 7–10-day intervals using the closed chamber method. Sandy Entic Podzol demonstrated a higher temperature sensitivity of SR in comparison with loamy Entic Luvisol. The Q10 values for both soils in dry years were 1.3–1.4 times lower than they were in the years with normal levels of humidity. For both types of soil, we observed a significant positive correlation between the Q10 values and wetness indexes. The interannual variability of Q10 values for SR in forest soils was 18%–40% depending on the calculation approach and levels of aridity/humidity over the growing season. The heterogeneous Q10 values should be integrated into SR and C balance models for better predictions.

Importance of Diurnal Temperature Range (DTR) for predicting the temperature sensitivity of soil respiration

OPINION article Front. Soil Sci., 24 August 2022Sec. Soil Organic Matter Dynamics and Carbon Sequestration https://doi.org/10.3389/fsoil.2022.969077

Decreased temperature sensitivity of soil respiration induced by warming slowed topsoil carbon turnover in a semi-arid grassland

The carbon feedback between soil and climate is partly determined by topsoil organic carbon turnover time (τ). However, the τ under future warmer climate still remains unclear. Herein, a manipulative experiment was conducted in a semi-arid grassland on the Loess Plateau of China to investigate the underlying mechanisms of the response of topsoil τ to warming. The results showed that warming significantly increased topsoil τ, which was directly regulated by the decreased temperature sensitivity of soil microbial respiration and indirectly due to the decreased pH and the increased aboveground biomass, soil inorganic nitrogen and soil carbon substrate quality. These results implied that short-term warming could potentially promote soil carbon sequestration in the semi-arid grassland.

Response of soil respiration to thinning is altered by thinning residue treatment in Cunninghamia lanceolata plantations

Forest thinning is a widely used practice in traditional and multiple function forest management. However, the effects of thinning residue treatment on soil respiration in forest are not fully understood. Here, a two-year field experiment quantified the effects of thinning intensity (medium and heavy thinning, 45% and 70% of volume removed, respectively) and the resulting residue treatment (retention and removal) on soil respiration in a subtropical Cunninghamia lanceolata plantation on a thin soil. Both thinning intensity and residue treatment significantly impacted on soil respiration. The control had a relative low mean soil respiration rate of 158 mg CO2 m−2 h−1 or 13.9 t ha−1 yr−1. Compared with the control, medium thinning with residue retained (MTR1) increased annual cumulative soil respiration by 13% only in the first year, while medium thinning with residue removal (MTR0) did not affect it in the two years. Heavy thinning with residue retention (HTR1) and removal (HTR0) elevated the mean annual cumulative respiration by 32% and 20%, respectively. Besides, there was no difference between MTR1 and HTR0. Soil respiration rate was correlated positively with soil temperature, moisture, and the concentrations of permanganate-oxidizable C and microbial biomass C, and inversely with the concentration of water-soluble organic C. Furthermore, heavy thinning with residue retention decreased the temperature sensitivity of soil respiration. Our findings highlight that the response of soil respiration to forest thinning was associated with thinning residue treatment.

Responses of Q10 to anthropogenic soil redistribution: Synthetic effects of SOM composition and r/K-shifts of microbial community

The temperature sensitivity of soil respiration (Q10) is a pivotal parameter for forecasting the fate of soil carbon (C) under global warming. Although a plethora of studies have elucidated the changes in Q10 in farmland or natural ecosystems, the response of Q10 to soil redistribution remains unclear. A simulated anthropogenic soil redistribution experiment by examining subsoil exposure (E20) and topsoil addition (A20) was performed to explore the influences of soil organic matter (SOM) composition and r/K-shifts of microbial community on Q10. Compared with the undisturbed soil, the average annual Q10 in the E20 plot was significantly increased, whereas the mean annual Q10 in the A20 plot decreased. The ratios of CC to COO and CC to CO, which indicate the stability of SOM, were significantly increased by 14.8%− 44.2% and 33.9%− 45.4% in the E20 plot but decreased by 18.6%− 28.1% and 3.8%− 11.2% in the A20 plot, respectively. The ratios of oligotrophs to copiotrophs in both the bacterial and fungal communities were significantly increased in the E20 plot (K-shift) but decreased in the A20 plot (r-shift). The β-D-xylosidase and cellobiohydrolase activities in the E20 plot were significantly decreased but prominently increased in the A20 plot, whereas the activity of polyphenol oxidase showed the opposite trend. The high aromaticity of recalcitrant SOM in the E20 plot determined the prevalence of K-shift in the bacterial and fungal communities, which might be attributed to the production of enzymes that decompose recalcitrant SOM, which then further enhanced Q10 and vice versa. Overall, our findings indicated that the feedback of ecological strategy of microbial community on the changes in SOM functional groups should be considered when evaluating the response of regional C cycling to anthropogenic soil redistribution.

Linkages between the temperature sensitivity of soil respiration and microbial life strategy are dependent on sampling season

The temperature sensitivity (Q10) of soil respiration (Rs) is crucial to assess the carbon (C) budget of terrestrial ecosystems under global warming. The Q10 changes along a climatic gradient as well as its seasonal dynamics remain unclear, and the underlying microbial mechanisms are not well known. Here, the seasonal Q10 of Rs at the northern, middle, and southern sites of a natural temperate mixed forest was examined. The mean annual temperature (MAT) of the sampling sites spanned from 0.5 to 4.9 °C. The Q10 pattern over the climatic zones was highly dependent on season, with Q10 increasing toward the southern region in spring and autumn, but having a similar level across the sampling sites in summer. In spring, Q10 was independent of microbial community composition and functions. Instead, spring Q10 increased with decreasing C availability from north to south, consistent with the Carbon-Quality-Temperature theory. In summer, Q10 was closely associated with the dominance of microbial r-strategy features, characterized by high copiotroph/oligotroph and labile/recalcitrant C degradation gene ratios. In autumn, however, Q10 was driven by the K-selected microbial communities, which might have been ascribed to the priming effects mediated by fresh plant litter. The seasonality of Q10 was site-dependent. The southern and middle sites had the lowest Q10 in summer, consistent with the Seasonal Plasticity Hypothesis, which predicts lower temperature sensitivity in warmer seasons. In contrast, the Q10 at the northern site remained stable during the growing season due to minor seasonal fluctuations in plant litter inputs and microbial community composition and functions. This work deepens our understanding on the complex relationships between Q10, carbon availability and microorganisms over spatial and temporal scales by translating microbial phylogenetic data into life strategies.

Contrasting effects of biological soil crusts on soil respiration in a typical steppe

Biological soil crusts (biocrusts), specialized communities of cyanobacteria, lichens, mosses, fungi and bacteria occurring on the ground surface, are key drivers of soil carbon (C) cycles in drylands, yet our understanding of how biocrusts directly and indirectly (through soil temperature or moisture) affect soil respiration and the contributions of biocrusts to soil C efflux is very limited. Using continuous field measurements in bare and biocrusted soils, we assessed the influence of biocrusts on soil respiration and the biocrust contribution to soil respiration over a one-year period and explained the mechanisms by which biocrusts directly and indirectly regulate soil respiration. Although the overall effect of biocrusts on soil respiration was positive, contrasting effects of biocrusts on soil respiration were also found. Unfortunately, the indirect effect of biocrusts on soil respiration through soil temperature or moisture was nonsignificant. The driving factor of total soil respiration was soil temperature, but soil moisture, photosynthetically active radiation and precipitation were driving factors for soil respiration in the biocrust layer. We proposed conceptual frameworks to explain the contrasting mechanisms by which biocrusts modulate soil respiration. In addition, biocrusts decreased the temperature sensitivity of soil respiration. Our findings indicate that biocrusts may alter the driving factors, forming contrasting mechanisms to regulate soil respiration in the biocrust layer, and emphasize the important roles of biocrusts as modulators of C cycles in dryland soils. Incorporating biocrusts into terrestrial C process models may improve predictions of climate change impacts on dryland ecosystems.

Diverging patterns at the forest edge: Soil respiration dynamics of fragmented forests in urban and rural areas.

As urbanization and forest fragmentation increase around the globe, it is critical to understand how rates of respiration and carbon losses from soil carbon pools are affected by these processes. This study characterizes soils in fragmented forests along an urban to rural gradient, evaluating the sensitivity of soil respiration to changes in soil temperature and moisture near the forest edge. While previous studies found elevated rates of soil respiration at temperate forest edges in rural areas compared to the forest interior, we find that soil respiration is suppressed at the forest edge in urban areas. At urban sites, respiration rates are 25% lower at the forest edge relative to the interior, likely due to high temperature and aridity conditions near urban edges. While rural soils continue to respire with increasing temperatures, urban soil respiration rates asymptote as temperatures climb and soils dry. Soil temperature- and moisture-sensitivity modeling shows that respiration rates in urban soils are less sensitive to rising temperatures than those in rural soils. Scaling these results to Massachusetts (MA), which encompasses 0.25Mha of the urban forest, we find that failure to account for decreases in soil respiration rates near urban forest edges leads to an overestimate of growing-season soil carbon fluxes of >350,000Mg C. This difference is almost 2.5 times that for rural soils in the analogous comparison (underestimate of <143,000Mg C), even though rural forest area is more than four times greater than urban forest area in MA. While a changing climate may stimulate carbon losses from rural forest edge soils, urban forests may experience enhanced soil carbon sequestration near the forest edge. These findings highlight the need to capture the effects of forest fragmentation and land use context when making projections about soil behavior and carbon cycling in a warming and increasingly urbanized world.

Microbial assemblies associated with temperature sensitivity of soil respiration along an altitudinal gradient

Identifying the drivers of the response of soil microbial respiration to warming is integral to accurately forecasting the carbon-climate feedbacks in terrestrial ecosystems. Microorganisms are the fundamental drivers of soil microbial respiration and its response to warming; however, the specific microbial communities and properties involved in the process remain largely undetermined. Here, we identified the associations between microbial community and temperature sensitivity (Q10) of soil microbial respiration in alpine forests along an altitudinal gradient (from 2974 to 3558 m) from the climate-sensitive Tibetan Plateau. Our results showed that changes in microbial community composition accounted for more variations of Q10 values than a wide range of other factors, including soil pH, moisture, substrate quantity and quality, microbial biomass, diversity and enzyme activities. Specifically, co-occurring microbial assemblies (i.e., ecological clusters or modules) targeting labile carbon consumption were negatively correlated with Q10 of soil microbial respiration, whereas microbial assemblies associated with recalcitrant carbon decomposition were positively correlated with Q10 of soil microbial respiration. Furthermore, there were progressive shifts of microbial assemblies from labile to recalcitrant carbon consumption along the altitudinal gradient, supporting relatively high Q10 values in high-altitude regions. Our results provide new insights into the link between changes in major microbial assemblies with different trophic strategies and Q10 of soil microbial respiration along an altitudinal gradient, highlighting that warming could have stronger effects on microbially-mediated soil organic matter decomposition in high-altitude regions than previously thought.

Relationship between basal soil respiration and the temperature sensitivity of soil respiration and their key controlling factors across terrestrial ecosystems

Relationship between basal soil respiration and the temperature sensitivity of soil respiration and their key controlling factors across terrestrial ecosystems

Past climate conditions predict the influence of nitrogen enrichment on the temperature sensitivity of soil respiration

The response of soil carbon release to global warming is largely determined by the temperature sensitivity of soil respiration, yet how this relationship will be affected by increasing atmospheric nitrogen deposition is unclear. Here, we present a global synthesis of 686 observations from 168 field studies to investigate the relationship between nitrogen enrichment and the temperature sensitivity of soil respiration. We find that the temperature sensitivity of total and heterotrophic soil respiration increased with latitude. In addition, for total and autotrophic respiration, the temperature sensitivity responded more strongly to nitrogen enrichment with increasing latitude. Temperature and precipitation during the Last Glacial Maximum were better predictors of how the temperature sensitivity of soil respiration responds to nitrogen enrichment than contemporary climate variables. The tentative legacy effects of paleoclimate variables regulate the response through shaping soil organic carbon and nitrogen content. We suggest that careful consideration of past climate conditions is necessary when projecting soil carbon dynamics under future global change.

Characteristics of Soil Respiration and Its Components of a Mixed Dipterocarp Forest in China

Background: Although numerous studies have been carried out in recent decades, soil respiration remains one of the less understood elements in global carbon budget research. Tropical forests store a considerable amount of carbon, and a well-established knowledge of the patterns, components, and controls of soil respiration in these forests will be crucial in global change research. Methods: Soil respiration was separated into two components using the trenching method. Each component was measured at multiple temporal scales and in different microhabitats. A commercial soil efflux system (Li8100/8150) was used to accomplish soil respiration monitoring. Four commonly used models were compared that described the temperature dependence of soil heterotrophic respiration using nonlinear statistics. Results and Conclusions: Trenching has a limited effect on soil temperature but considerably affects soil water content due to the exclusion of water loss via tree transpiration. Soil respiration decreased gradually from 8 to 4 μmol·m−2·s−1 6 days after trenching. Soil autotrophic (Ra) and heterotrophic respiration (Rh) have contrasting diel patterns and different responses to temperature. Rh was negatively correlated with temperature but positively correlated with relative humidity. Both Ra and Rh varied dramatically among microhabitats. The Q10 value of Rh derived using the Q10 model was 2.54. The Kirschbaum–O’Connell model, which implied a strong decrease of Q10 with temperature, worked best in describing temperature dependence of Rh. Heterotrophic respiration accounted for nearly half of the total soil efflux. We found an unexpected diurnal pattern in soil heterotrophic respiration which might be related to diurnal moisture dynamics. Temperature, but not soil moisture, was the major controller of seasonal variation of soil respiration in both autotrophic and heterotrophic components. From a statistical perspective, the best model to describe the temperature sensitivity of soil respiration was the Kirschbaum–O’Connell model. Soil respiration varied strongly among the microhabitats and played a crucial role in stand-level ecosystem carbon balance assessment.

Plant community composition alters moisture and temperature sensitivity of soil respiration in semi-arid shrubland.

Soil respiration (Rs) is the second largest carbon (C) flux to the atmosphere and our understanding of how Rs and its components shift with plant-community composition remains an important question. We used high-frequency soil respiration measurements and root exclusion to evaluate how Rs, autotrophic respiration (Ra) and heterotrophic respiration (Rh) vary between a semi-arid perennial shrub community and annual invasive community. Over two growing seasons, total Rs was 40% higher under annual vegetation compared to shrubs. Partitioning revealed consistently higher Ra under annual vegetation which accounted for most of the difference in Rs. Under annual vegetation, Ra increased soon after the first rain events and remained high despite cooling temperatures while shrub Ra increased only when soil temperature began to warm up. The Rh rates were similar between vegetation types when daily soil temperatures were lower than 20°C. As soil temperatures increased and soil moisture dropped below 10%, Rh was consistently higher under annual vegetation than shrubs. Seasonal dynamics of Rs and Rh were best modeled with an interaction term between soil moisture and temperature with significantly different model parameters for each vegetation type. Differences in the timing and magnitude of Rs and Ra between vegetation types are consistent with phenological differences between shrubs and annuals. Under annuals, larger Rh at high temperatures suggests that expansion of annual vegetation and future hotter and drier conditions could lead to greater C losses from this semi-arid shrub system.

Global patterns of geo-ecological controls on the response of soil respiration to warming

While soil respiration is known to be controlled by a range of biotic and abiotic factors, its temperature sensitivity in global models is largely related to climate parameters. Here, we show that temperature sensitivity of soil respiration is primarily controlled by interacting soil properties and only secondarily by vegetation traits and plant growth conditions. Temperature was not identified as a primary driver for the response of soil respiration to warming. In contrast, the nonlinearity and large spatial variability of identified controls stress the importance of the interplay among soil, vegetation and climate parameters in controlling warming responses. Global models might predict current soil respiration but not future rates because they neglect the controls exerted by soil development. To accurately predict the response of soil respiration to warming at the global scale, more observational studies across pedogenetically diverse soils are needed rather than focusing on the isolated effect of warming alone. Understanding the temperature sensitivity of soil respiration is critical to determining soil carbon dynamics under climate change. Spatial heterogeneity in controls highlights the importance of interactions between vegetation, soil and climate in driving the response of respiration to warming.

Seasonal variations in temperature sensitivity of soil respiration in a larch forest in the Northern Daxing’an Mountains in Northeast China

Temperature sensitivity of respiration of forest soils is important for its responses to climate warming and for the accurate assessment of soil carbon budget. The sensitivity of temperature (Ti) to soil respiration rate (Rs), and Q10 defined by e10(lnRs−lna)/Ti has been used extensively for indicating the sensitivity of soil respiration. The soil respiration under a larch (Larix gmelinii) forest in the northern Daxing’an Mountains, Northeast China was observed in situ from April to September, 2019 using the dynamic chamber method. Air temperatures (Tair), soil surface temperatures (T0cm), soil temperatures at depths of 5 and 10 cm (T5cm and T10cm, respectively), and soil-surface water vapor concentrations were monitored at the same time. The results show a significant monthly variability in soil respiration rate in the growing season (April–September). The Q10 at the surface and at depths of 5 and 10 cm was estimated at 5.6, 6.3, and 7.2, respectively. The Q10@10 cm over the period of surface soil thawing (Q10@10 cm, thaw = 36.89) were significantly higher than that of the growing season (Q10@10 cm, growth = 3.82). Furthermore, the Rs in the early stage of near-surface soil thawing and in the middle of the growing season is more sensitive to changes in soil temperatures. Soil temperature is thus the dominant factor for season variations in soil respiration, but rainfall is the main controller for short-term fluctuations in respiration. Thus, the higher sensitivity of soil respiration to temperature (Q10) is found in the middle part of the growing season. The monthly and seasonal Q10 values better reflect the responsiveness of soil respiration to changes in hydrometeorology and ground freeze-thaw processes. This study may help assess the stability of the soil carbon pool and strength of carbon fluxes in the larch forested permafrost regions in the northern Daxing’an Mountains.

Applying biochar under topsoil facilitates soil carbon sequestration: A case study in a dryland agricultural system on the Loess Plateau

The remarkable soil carbon sequestration and greenhouse gas mitigation effects of biochar have spurred great interest in exploring ways to maximize its benefits. However, it remains unclear how biochar application depth impacts soil carbon dioxide (CO2) emissions and methane (CH4) uptake in upland soil. Therefore, we carried out a 16-month field experiment in a dryland agricultural system to answer the above questions. Woody biochar (20 t ha−1) was mixed into three soil layers: 0–10 cm (BC0-10cm), 10–20 cm (BC10-20cm), and 0–20 cm (BC0-20cm). Soil without biochar addition was used as the control (CK). We monitored soil CO2 and CH4 fluxes continuously and determined the metabolic quotient (qCO2) and the sensitivity of soil respiration to temperature (Q10). The results indicated that CO2 emissions, CH4 uptake, qCO2 and Q10 were significantly affected by biochar application depth. Overall, compared with CK, BC0-10cm increased total CO2 emissions by 10.13%, while BC10-20cm and BC0-20cm showed no significant effect. BC0-10cm and BC0-20cm exhibited greater soil CH4 uptake enhancement than BC10-20cm, but the enhanced CH4 uptake resulted in limited net greenhouse gas mitigation. BC10-20cm and BC0-20cm had a lower qCO2 than the other treatments, which likely increased the carbon use efficiency and decreased the stress on soil microbes, but BC0-10cm showed the opposite effect. In addition, BC0-10cm significantly reduced Q10 mainly due to the enhanced lability of the native carbon and microbial activities. Changes in environmental factors in the 0–10 cm soil largely explained the variations in CO2 emissions, CH4 uptake and Q10 (>88%). Nevertheless, the enhanced microbial biomass in the 10–20 cm soil helped lower qCO2 in the whole 0–20 cm layer. In summary, adding biochar to surface soil (0–10 cm) likely accelerates carbon loss, due to the strong shift in the environment of the surface soil caused by complex interactions among hydrothermal conditions, nutrient levels (i.e., N, NH4+, NO3− and available P) and labile carbon. However, adding biochar to subsurface soil (10–20 cm) can effectively avoid severe disturbance of the surface soil environment and thus benefit soil carbon sequestration in the long term.

To till or not to till in a temperate ecosystem? Implications for climate change mitigation

The management of agricultural soils affect the composition and scale of their greenhouse gas (GHG) emissions. There is conflicting evidence on the effect of zero-tillage on carbon storage and GHG emissions. Here we assess the effects of zero-tillage over a range of time frames (1–15 years) on carbon storage and GHG release and their controls in the UK Net global warming potential was 30% lower under zero-tillage systems, due to lower carbon dioxide fluxes, with the greatest impacts after longer periods of zero-tillage management. Simultaneously, in zero-tillage systems, soil carbon stocks and the proportion of sequestered recalcitrant carbon increased while the temperature sensitivity of soil respiration decreased with time, compared to conventionally soils. We conclude that zero-tillage could play a crucial role in both reducing GHG emissions and at the same time increase soil carbon sequestration, therefore contributing to mitigate against climate change. Our findings are particularly important in the context of designing new policies (for example the Environmental Land Management Schemes in the UK) that ensure the sustainability of agricultural production in a changing climate.