Temperature Response Of Soil Respiration Research Articles

Temperature response of soil respiration decreases with latitude and elevation in abandoned croplands

Soil respiration (Rs), a critical component of the global carbon cycle, is highly sensitive to warming. Agricultural soils, including abandoned croplands, are large sources of carbon dioxide to the atmosphere. However, the responses of Rs and its components to warming from abandoned croplands with no further management activities remain elusive at the national scale. Here, we report the warming responses of Rs, heterotrophic respiration (Rh), and autotrophic respiration (Ra) from China’s abandoned croplands spanning a large range in latitude (22.33–46.58°N) and elevation (2–3734 m) from three-year in situ warming experiments. We found that warming treatment (+1.6 °C) significantly stimulated Rs, Rh, and Ra by 30.4%, 37.2%, and 37.3%, respectively. The response of Rs to warming was higher in abandoned croplands (19.1% °C−1) than in other terrestrial ecosystems (5.4%–9.2% °C−1), attributing to greater increases in plant biomass and soil organic carbon induced by warming. Rs was more responsive to warming in low latitude or elevation regions with high plant biomass. Under the warming conditions, the apparent temperature sensitivity (Q10) of Rs increased in low latitude and elevation regions due to a decrease in soil carbon availability but decreased in high latitude and elevation regions due to an increase in carbon availability induced by warming. Despite the positive warming response of Rs, the net ecosystem productivity in abandoned croplands slightly increased by 18.7% attributing to increased plant productivity under warming. These findings demonstrate that Rs in abandoned croplands was more sensitive to warming in warmer regions than in colder regions, underscoring the importance of latitude- or elevation-induced variations in soil carbon availability in determining the response of Rs to warming and projecting cropland carbon-climate feedback.

An overlooked mechanism underlying the attenuated temperature response of soil heterotrophic respiration.

Biogeochemical reactions occurring in soil pore space underpin gaseous emissions measured at macroscopic scales but are difficult to quantify due to their complexity and heterogeneity. We develop a volumetric-average method to calculate aerobic respiration rates analytically from soil with microscopic soil structure represented explicitly. Soil water content in the model is the result of the volumetric-average of the microscopic processes, and it is nonlinearly coupled with temperature and other factors. Since many biogeochemical reactions are driven by oxygen (O2) which must overcome various resistances before reaching reactive microsites from the atmosphere, the volumetric-average results in negative feedback between temperature and soil respiration, with the magnitude of the feedback increasing with soil water content and substrate quality. Comparisons with various experiments show the model reproduces the variation of carbon dioxide emission from soils under different water content and temperature gradients, indicating that it captures the key microscopic processes underpinning soil respiration. We show that alongside thermal microbial adaptation, substrate heterogeneity and microbial turnover and carbon use efficiency, O2 dissolution and diffusion in water associated with soil pore space is another key explanation for the attenuated temperature response of soil respiration and should be considered in developing soil organic carbon models.

Separating the temperature response of soil respiration derived from soil organic matter and added labile carbon compounds

Broadly, soil organic C can be characterised as either labile (highly available and soluble) or stable (physiochemically protected) carbon. Previous studies have attributed differences in the temperature response of these C pools to overall availability or chemical complexity. Here, we estimated the decomposition of the labile pool as the difference of CO2 from soils with added highly available C substrates (arginine, glucose, glutamine, lysine, and maltose) and yeast extract, and CO2 from soil without added C. We also measured the temperature response of the decomposition of soil organic matter (SOM), which encompasses both labile and stable C (no added C). Soil was incubated for five hours using a temperature gradient block consisting of 18 discrete temperatures (~8–52 °C). We also tested to see if temperature responses differed between three contrasting soils (allophanic, gley, and organic/degraded peat). We applied macromolecular rate theory (MMRT) to the RS data to calculate the temperature optimum (Topt) and the inflection temperature (Tinf).The decomposition of SOM had an exponential, Arrhenius-like behaviour. In contrast, respiration of the five labile C compounds had a clear and similar Topt of around 37 °C and Tinf of 22 °C. The temperature response of the more labile C and of the SOM pools did not significantly vary between the three very different soils, suggesting that these responses might be independent of soil properties.Our findings provide support for the hypothesis that the overall temperature dependence of soil respiration is reliant on sorption/desorption and diffusion to microbes – a process that exhibits Arrhenius behaviour, and the biological decomposition of C by these soil microbes that exhibits MMRT behaviour. The overall response to temperature is governed by substrate availability as biological processes dominate when substrate is non-limiting, and physiochemical processes dominate when substrate availability is limiting.

Shifts in temperature response of soil respiration between adjacent irrigated and non-irrigated grazed pastures

Land management practices that increase food production are needed to match demand from a growing global population. Adoption of these practices needs to be balanced by potential adverse consequences such as nutrient losses and production of greenhouse gases. We previously demonstrated that pasture soils irrigated during summer-dry conditions had significantly less soil carbon than adjacent unirrigated pastures, despite increased plant production. Precise reasons for lower carbon under irrigation were not clear but both inputs (photosynthesis) and losses (respiration) of carbon are regulated by soil moisture and temperature. Our objective was to determine whether the temperature and moisture response of soil respiration differed between 13 adjacent irrigated and unirrigated soils (0-0.1 m). Soil respiration rates were measured in the laboratory using a temperature block where rates of respiration were measured within 5 h at ˜3 °C increments between 6 and 60 °C (20 temperatures) and at 5 different moisture contents. Temperature response, sensitivity and key temperature parameters (temperature optimum (Topt) and inflection point temperature (Tinf)) were calculated using macromolecular rate theory (MMRT). Respiration rates increased with increasing moisture content similarly for both irrigated and unirrigated soils. However, soil respiration at the same temperature was significantly (P < 0.05) lower and Q10 higher in irrigated soils. Tinf and Topt were greater in irrigated soils. We attribute the lower respiration in irrigated soils to a disproportionate loss of available carbon, total soil carbon loss was ˜14% while the differences in respiration were between 58% at 10 °C and 41% at 20 °C. The lower carbon availability in irrigated soils was likely responsible for the increased Q10, Tinf and Topt as substrate decomposability and availability became more limiting so that ongoing decomposition became increasingly dependent on solubilisation and diffusion of remaining carbon substrates to micro-organisms. We postulate that as respiration becomes increasingly limited by substrate supply through physical chemistry processes (diffusion, and sorption/desorption) rather than substrate biodegradability, the temperature response curve will shift from a MMRT dominated response (with a temperature optimum) to an Arrhenius dominated response (exponential). Our data suggest that commencement of irrigation removed moisture limitation during normally dry summers and led to a loss of soil carbon due to an initially increased microbial activity that has now decreased as carbon availability declined.

Precipitation events reduce soil respiration in a coastal wetland based on four-year continuous field measurements

Coastal wetlands are considered as a significant sink for global carbon because their organic-rich soils. Given exposed to shallow water tables, water from groundwater is transported upward to the root zone through capillary rise, thus soil moisture in coastal wetlands is relatively high even when there is no precipitation. We expected that as precipitation occurred, the soils in coastal wetlands might become quickly saturated and lead to the development of anoxic conditions. We further hypothesized that such anoxic conditions might decrease soil respiration by limiting oxygen availability and biological activities of roots and microorganisms. Based on continuous automated soil respiration data collected in a coastal wetland in the Yellow River Delta over 4 years (2012–2015), the results showed that on the annual scale, cumulative soil respiration was 317, 321, 231, and 274 g C m−2 yr-1 for 2012, 2013, 2014, and 2015, respectively, with an average of 286 g C m−2 yr-1. The rate of soil respiration increased exponentially with soil temperature during each year and its two seasons (growing season and non-growing season). In addition, soil respiration was significantly related to soil moisture during the growing season, but was not affected by soil moisture during the non-growing season. After each precipitation event, soil respiration was significantly negatively correlated with soil moisture under different initial soil water contents. There was a significant positive correlation between changes in soil respiration and changes in soil moisture following precipitation events. Moreover, the increase of soil moisture following precipitation events changed the temperature response of soil respiration. Our study indicated that precipitation events could decrease soil respiration by increasing soil moisture and inducing anoxic conditions in the coastal wetland. Therefore, we speculate that the continuation of decreasing precipitation and increasing temperature trends in the Yellow River Delta may increase soil carbon losses in the coastal wetland due to the increase in soil respiration.

Temperature response of soil respiration largely unaltered with experimental warming

The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic warming.

Soil respiration response in different vegetation types at Mount Taihang, China

Temperature response of soil respiration depends on the sensitivity and adaptability of soil respiration (SR) for the variation of soil temperature, which will directly influence the terrestrial carbon cycling and extent prediction of global warming. The diurnal and seasonal variations in the temperature response of SR were assessed through continuous measurement during the June 2012–May 2013 with an automated chamber system under three vegetation types (Robinia pseudoacacia, RP; Vitex negundo var. Heterophylla, VN; Artemisia sacrorum, AS) in the hilly region of Mount Taihang, China. Our results indicated that SR exhibited significant seasonal variations in the RP, VN and AS sites (0.15–5.14, 0.14–4.51 and 0.22–5.28μmolm−2s−1). Due to the adaptability for the variation of soil temperature, SR peaked in Aug 2012 and bottomed in Apr 2013, and the adaptability will weaken the relationship between SR and temperature. Because of the differences of plant physiology and environment conditions, temperature sensitivity of soil respiration (Q10) varied among vegetation types. Meanwhile, because of exempted from seasonal complicated factors, average daily Q10 values of the RP, VN and AS sites (1.86, 1.35 and 1.53) were all smaller than the values of annual Q10 (2.12, 3.32 and 2.61), and might better reflect the biological sensitivity of respiration to temperature. Q10 exhibited a strong seasonal variation pattern, and decreased with increasing soil temperature. This result indicates that low temperature may be more important to carbon cycling than higher temperature based on soil respiration results. The study area had low soil respiration rates, enhancing the long term C accumulation in the context of global warming. The seasonal variation of Q10 was primarily driven by soil temperature while soil moisture had little influence on the dynamic for each site based on annual scales. However, due to the complicated relation between soil properties and SR, Q10 value derived from diurnal and seasonal patterns of SR should be used with extreme caution when estimating carbon balance of terrestrial ecosystem.

Temperature response of soil respiration in a Chinese pine plantation: hysteresis and seasonal vs. diel Q10.

Although the temperature response of soil respiration (Rs) has been studied extensively, several issues remain unresolved, including hysteresis in the Rs–temperature relationship and differences in the long- vs. short-term Rs sensitivity to temperature. Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling. We monitored soil CO2 efflux with an automated chamber system in a Pinus tabulaeformis plantation near Beijing throughout 2011. Soil temperature at 10-cm depth (Ts) exerted a strong control over Rs, with the annual temperature sensitivity (Q 10) and basal rate at 10°C (Rs 10) being 2.76 and 1.40 µmol m−2 s−1, respectively. Both Rs and short-term (i.e., daily) estimates of Rs 10 showed pronounced seasonal hysteresis with respect to Ts, with the efflux in the second half of the year being larger than that early in the season for a given temperature. The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input. As a result, all of the applied regression models failed to yield unbiased estimates of Rs over the entire annual cycle. Lags between Rs and Ts were observed at the diel scale in the early and late growing season, but not in summer. The seasonality in these lags may be due to the use of a single Ts measurement depth, which failed to represent seasonal changes in the depth of CO2 production. Daily estimates of Q 10 averaged 2.04, smaller than the value obtained from the seasonal relationship. In addition, daily Q 10 decreased with increasing Ts, which may contribute feedback to the climate system under global warming scenarios. The use of a fixed, universal Q 10 is considered adequate when modeling annual carbon budgets across large spatial extents. In contrast, a seasonally-varying, environmentally-controlled Q 10 should be used when short-term accuracy is required.

Roots affect the response of heterotrophic soil respiration to temperature in tussock grass microcosms

While the temperature response of soil respiration (R(S)) has been well studied, the partitioning of heterotrophic respiration (R(H)) by soil microbes from autotrophic respiration (R(A)) by roots, known to have distinct temperature sensitivities, has been problematic. Further complexity stems from the presence of roots affecting R(H), the rhizosphere priming effect. In this study the short-term temperature responses of R(A) and R(H) in relation to rhizosphere priming are investigated. Temperature responses of R(A), R(H) and rhizosphere priming were assessed in microcosms of Poa cita using a natural abundance δ(13)C discrimination approach. The temperature response of R(S) was found to be regulated primarily by R(A), which accounted for 70 % of total soil respiration. Heterotrophic respiration was less sensitive to temperature in the presence of plant roots, resulting in negative priming effects with increasing temperature. The results emphasize the importance of roots in regulating the temperature response of R(S), and a framework is presented for further investigation into temperature effects on heterotrophic respiration and rhizosphere priming, which could be applied to other soil and vegetation types to improve models of soil carbon turnover.

Thresholds and interactive effects of soil moisture on the temperature response of soil respiration

Ecosystem carbon exchange is poorly understood in low-productivity, semiarid habitats. Here we studied the controls of soil temperature and moisture on soil respiration in climate change field experiment in a sandy forest-steppe. Soil CO 2 efflux was measured monthly from April to November in 2003–2008 on plots receiving either rain exclusion or nocturnal warming, or serving as ambient control. Based on this dataset, we developed and compared empirical models of temperature and moisture effects on soil respiration. Results suggest that in this semiarid ecosystem the main controlling factor for soil CO 2 efflux is soil temperature, while soil moisture has less, although significant effect on soil respiration. Clear thresholds for moisture effects on temperature sensitivity were identified at 0.6, 4.0 and 7.0 vol% by almost each model, which relate well to other known limits for biological activity in this sandy soil. The relationship between soil respiration and temperature was better described by the Lloyd–Taylor or the Gaussian functions compared to exponential function. Involving additive and interactive soil moisture effects further improved model fitting. Similarly to other low productivity semiarid ecosystems, annual soil carbon efflux values estimated by the different models were rather low (between 123.1 and 139.8 g C m −2 yr −1 as multi-year averages).

The temperature responses of soil respiration in deserts: a seven desert synthesis

The temperature response of soil respiration in deserts is not well quantified. We evaluated the response of respiration to temperatures spanning 67°C from seven deserts across North America and Greenland. Deserts have similar respiration rates in dry soil at 20°C, and as expected, respiration rates are greater under wet conditions, rivaling rates observed for more mesic systems. However, deserts differ in their respiration rates under wet soil at 20°C and in the strength of the effect of current and antecedent soil moisture on the sensitivity and magnitude of respiration. Respiration increases with temperature below 30°C but declines for temperatures exceeding 35°C. Hot deserts have lower temperature sensitivity than cold deserts, and insensitive or negative temperature sensitivities were predicted under certain moisture conditions that differed among deserts. These results have implications for large-scale modeling efforts because we highlight the unique behavior of desert soil respiration relative to other systems. These behaviors include variable temperature responses and the importance of antecedent moisture conditions for soil respiration.

Temperature response of soil respiration is dependent on concentration of readily decomposable C

Abstract. Temperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux associated with the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half-saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of data obtained in incubation experiments with forest and arable soils. Our data support the hypothesis and suggest that concentration of readily decomposable C substrate (as glucose equivalents) and temperature dependent substrate release are the important factors controlling temperature sensitivity of soil respiration. The highest temperature sensitivity of soil respiration was observed when substrate release was temperature dependent and C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant by glucose addition resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, attributing this phenomenon to changes in concentration of readily decomposable C substrate.

Grazing intensity alters soil respiration in an alpine meadow on the Tibetan plateau

Grazing intensity may alter the soil respiration rate in grassland ecosystems. The objectives of our study were to (1) determine the influence of grazing intensity on temporal variations in soil respiration of an alpine meadow on the northeastern Tibetan Plateau; and (2) characterise the temperature response of soil respiration under different grazing intensities. Diurnal and seasonal soil respiration rates were measured for two alpine meadow sites with different grazing intensities. The light grazing (LG) meadow site had a grazing intensity of 2.55 sheep ha −1, while the grazing intensity of the heavy grazing (HG) meadow site, 5.35 sheep ha −1, was approximately twice that of the LG site. Soil respiration measurements showed that CO 2 efflux was almost twice as great at the LG site as at the HG site during the growing season, but the diurnal and seasonal patterns of soil respiration rate were similar for the two sites. Both exhibited the highest annual soil respiration rate in mid-August and the lowest in January. Soil respiration rate was highly dependent on soil temperature. The Q 10 value for annual soil respiration was lower for the HG site (2.75) than for the LG site (3.22). Estimates of net ecosystem CO 2 exchange from monthly measurements of biomass and soil respiration revealed that during the period from May 1998 to April 1999, the LG site released 2040 g CO 2 m −2 y −1 to the atmosphere, which was about one third more than the 1530 g CO 2 m −2 y −1 released at the HG site. The results suggest that (1) grazing intensity alters not only soil respiration rate, but also the temperature dependence of soil CO 2 efflux; and (2) soil temperature is the major environmental factor controlling the temporal variation of soil respiration rate in the alpine meadow ecosystem.

Climatic and resource quality controls on soil respiration across a forest–tundra ecotone in Swedish Lapland

We studied resource quality and climatic constraints on soil respiration over a mountain birch forest–tundra ecotone in northern Swedish Lapland during 1999–2001 by means of both a field-based soil transplant experiment and a laboratory incubation experiment. Average carbon dioxide fluxes over the 2000 thaw season were 0.62 and 0.48 g CO 2 m −2 h −1, at forest and tundra control plots, respectively. We attribute the higher respiration rate at the forest site mainly to more favourable microclimate but also to higher resource quality. Temperature–respiration relationships described using Arrhenius equations explained 37% of the variation in the tundra soil respiration and 42% for the forest soils on a season-wide basis in 2000. Q 10 values (exponential temperature-response) were generally high (except in August in the field experiment) compared to the global average (2.4) and varied over time, with increased temperature-dependency at low soil temperatures. In the laboratory, higher activation energy was found in soils incubated at higher temperatures (12 and 17 °C; in the range 133–109 kJ mol −1) compared with lower temperatures (2 and 7 °C; in the range 98–92 kJ mol −1) suggesting an adaptation of the decomposer community toward more psychrophilic organisms or metabolism in low-temperature environments. Soil moisture, however, could also play an important role in modifying any temperature response of soil respiration in this sub-arctic ecotone area. These mesic soils have a relatively rapid turnover time of carbon and should be compared to boreal forest and temperate woodland in carbon dynamics. We conclude that a shift from tundra to birch forest would give an initial pulse of carbon released from soil to the atmosphere as labile carbon stored in tundra soils is metabolised by decomposer organisms.