Heterotrophic Respiration Rates Research Articles

Dynamics of carbon budget and meteorological factors of a typical maize ecosystem in Songnen Plain, China

Aim of study: Understanding the carbon budget and meteorological factor impacts of farmland ecosystems is helpful for scientific assessment of carbon budget and low-carbon agricultural production practices. Area of study: The Songnen Plain, NE China, in 2019. Material and methods: Based on eddy-related flux and soil heterotrophic respiration observations from a typical maize farmland ecosystem, using mathematical statistics and carbon balance equation methods, were analyzed. Main results: Soil respiration rate (Rs) and composition were influenced and controlled by the synergistic effect of surface soil temperature (Ts) and water content (Wcs). Ts played a leading role, while Wcs played an important role. Ts and Wcs had the greatest influence on the heterotrophic respiration rate (Rh), followed by Rs and autotrophic respiration rate (Ra). Daily variations of net ecosystem productivity were correlated with daily mean air temperature, latent heat flux, and sensible heat flux. Annual carbon revenue was 1139.67 g C m-2, annual carbon expenditure was 456.14 g C m-2, and annual carbon budget was -683.53 g C m-2 in 2019. While considering that maize grain yield (-353.44 g C m-2) was moved out of the field at harvest, the net ecosystem carbon balance was -330.09 g C m-2; then it was carbon sink in 2019. By fully utilizing climate resources and improving agricultural managements, carbon sink is increased in farmland ecosystems. Research highlights: Soil respiration rate and composition were influenced and controlled by the synergistic effect of soil temperature and water content; the maize farmland ecosystem is carbon sink.

Impacts of large-scale Saharan solar farms on the global terrestrial carbon cycle

Amassing the available solar energy over the Sahara desert, through the installation of a large-scale solar farm, would satisfy the world’s current electricity needs. However, such land use changes may affect the global carbon cycle, possibly offsetting mitigation efforts. Here a fully coupled Earth System model EC-Earth was used to investigate the impact of a Saharan solar farm on the terrestrial carbon cycle, simulated with prescribed reduced surface albedo approximating the albedo effect of photovoltaic solar panels over the Sahara desert. The resulting changes to the carbon cycle were an enhancement of the carbon sink across Northern Africa, particularly around the Sahel but a simultaneous weakening of the carbon sink in the Amazon basin. This is observed through spatial pattern changes to the values of net biome production (NBP), more evident during Northern Hemisphere summer season. NBP changes are contributed by competing responses in the net primary production and heterotrophic respiration rates. These changes to carbon exchange correspond to a wetter and warmer climate occurring in Northern Africa and a drier and warmer climate in the Amazon, with stronger driving effects of precipitation. Due to these coupled responses and complex teleconnections, thorough investigation of remote impacts of solar farms are needed to avoid unintended consequences on the terrestrial carbon cycle.

Dissolved organic carbon bioreactivity and DOC:DIN stoichiometry control ammonium uptake in an intermittent Mediterranean stream

Abstract Heterotrophic organisms in streams use dissolved organic carbon (DOC) and dissolved inorganic nitrogen (DIN) from the water column to meet their growth and energy requirements. However, the role of DOC availability in driving DIN uptake in headwater streams is still poorly understood. In this study, we focus on how DOC:DIN stoichiometry and DOC bioreactivity control ammonium (NH4+) uptake and heterotrophic aerobic respiration, and how this influence varies among seasons in a forested Mediterranean headwater stream. We estimated in‐stream NH4+ uptake rates seasonally by conducting whole‐reach constant‐rate additions of NH4+ with and without amendments of either lignin (recalcitrant DOC) or acetate (labile DOC). During each addition, we characterised microbial community composition by molecular analyses, stream metabolism with the single‐station method, and heterotrophic aerobic respiration by adding a metabolic tracer (resazurin). The stream was heterotrophic (net ecosystem production <0) regardless of the season, with a microbial community mostly composed of heterotrophic bacteria. In‐stream NH4+ uptake rates were not related to either background NH4+ or DOC concentrations. Instead, these rates increased with increasing the molar ratio of NH4+ to nitrate (NO3−) (NH4+:NO3−) and DOC to DIN (DOC:DIN).Whole‐reach heterotrophic aerobic respiration rates showed the same relationship against stoichiometric ratios as NH4+ uptake rates. Furthermore, in‐stream NH4+ uptake rates were from 5% to >800% higher during the co‐additions of acetate than when adding NH4+ either alone or with lignin. Our results indicate that in‐stream NH4+ uptake was largely controlled by heterotrophic bacteria, and that the stoichiometric balance between organic resources and nutrients was key to explaining the variability of in‐stream NH4+ uptake and heterotrophic aerobic respiration. Moreover, the observed increase in NH4+ uptake during acetate additions suggests that heterotrophic activity was limited by labile DOC availability. Our study highlights that both DOC:DIN stoichiometry and DOC bioreactivity are relevant factors driving the seasonal pattern of in‐stream N processing in this forested Mediterranean headwater stream.

Aerobic granulation in an oxidation ditch using the residual sludge after extracting slime-extracellular polymer substances

Sludge granulation in continuous flow reactors (CFRs) is still of great challenge with the hardly obtained hydraulic selection pressure. A novel method was investigated for cultivating granular sludge in an oxidation ditch by recycling the residual sludge after extracting slime-extracellular polymer substances (slime-EPS). Compared to the raw sludge, bioactivities of the residual sludge slightly decreased based on endogenous, autotrophic, and heterotrophic respiration rates (SOURe, SOURA, and SOURH). When the slime-EPS extracted sludge was returned to the main reactor, the SOURe reduced and maintained stable later. For the first and second recycling, SOURA increased from 0.80 to 1.69 mgO2/gSS/h, and 0.16 to 1.21 mgO2/gSS/h, respectively, while SOURH exhibited initial decrease, subsequent increase and later stable trends. Moreover, total nitrogen in effluent decreased from 8.09 to 7.22 mg/L, and the protein-to-polysaccharide concentration ratio increased from 0.49 to 1.55. In addition, the mixed sludge of raw and residual sludge exhibited higher coaggregation capacity with decreased supernatant turbidity, triggering the granulation process. After 94-day operations, granules larger than 200 μm accounted for 32 % in the oxidation ditch, where neither hydraulic selection pressures nor feast-famine phases were provided. Therefore, returning the slime-EPS extracted sludge to the CFRs is a promising approach for aerobic granulation.

Microbial communities in terrestrial surface soils are not widely limited by carbon.

Microbial communities in soils are generally considered to be limited by carbon (C), which could be a crucial control for basic soil functions and responses of microbial heterotrophic metabolism to climate change. However, global soil microbial C limitation (MCL) has rarely been estimated and is poorly understood. Here, we predicted MCL, defined as limited availability of substrate C relative to nitrogen and/or phosphorus to meet microbial metabolic requirements, based on the thresholds of extracellular enzyme activity across 847 sites (2476 observations) representing global natural ecosystems. Results showed that only about 22% of global sites in terrestrial surface soils show relative C limitation in microbial community. This finding challenges the conventional hypothesis of ubiquitous C limitation for soil microbial metabolism. The limited geographic extent of C limitation in our study was mainly attributed to plant litter, rather than soil organic matter that has been processed by microbes, serving as the dominant C source for microbial acquisition. We also identified a significant latitudinal pattern of predicted MCL with larger C limitation at mid- to high latitudes, whereas this limitation was generally absent in the tropics. Moreover, MCL significantly constrained the rates of soil heterotrophic respiration, suggesting a potentially larger relative increase in respiration at mid- to high latitudes than low latitudes, if climate change increases primary productivity that alleviates MCL at higher latitudes. Our study provides the first global estimates of MCL, advancing our understanding of terrestrial C cycling and microbial metabolic feedback under global climate change.

Quantitative study of biofilm yield and biomass distribution of a multi-stage moving-bed biofilm system

Abstract A multi-stage anoxic/oxic (A/O) moving-bed biofilm reactor (MBBR) system with multiple chambers was established for municipal wastewater treatment. The active biomass quantity, bioactivity, and biomass yield of a pilot-scale multi-stage MBBR were investigated in this study. The microbial activity and heterotrophic yield coefficients (YH) were measured using respirometric techniques in each chamber at different temperature conditions. Meanwhile, the growth, nitrification, and denitrification rates of functional biomass were also quantified as specific respiration rate (SOUR). The total active biomass in the multi-stage A/O-MBBR system was 0.71–1.68 g COD/m2 for the aerobic reactor and 0.39–1.44 g COD/m2 for the anoxic reactor at 10–19 °C. The YH values for the anoxic reactors were 0.61–0.69, which were comparable to the recommended value of the activated sludge model (ASM1). The correlation coefficient between Nitrospira and the autotrophic specific respiration rate (SOURA) was 0.82. Meanwhile, denitrifying genera showed a significant correlation with the heterotrophic specific respiration rate (SOURH) and the active heterotrophic biomass (XH). This study provided insights into biomass distribution and the corresponding kinetic parameters for the multi-stage MBBR systems, which may serve as a reference for process design and trouble shooting.

Effects of liming on soil respiration and its sensitivity to temperature in Cunninghamia lanceolata plantations.

The primary distribution area of acid deposition coincides with areas of Chinese fir (Cunninghamia lanceolata) plantations. Liming is an effective method of restoring acidified soil. To understand the effects of liming on soil respiration and temperature sensitivity within the context of acid deposition, we measured soil respiration and its components in Chinese fir plantations for one year beginning in June 2020, with 0, 1 and 5 t·hm-2 calcium oxide being added in 2018. The results showed that liming considerably increased soil pH and exchangeable Ca2+ concentration, and that there was no significant difference among different levels of lime application. Soil respiration rate and components in the Chinese fir plantations exhibited seasonal variations, with the highest values during the summer and the lowest values during the winter. Although liming did not alter seasonal dynamics, it strongly inhibited heterotrophic respiration rate and increased autotrophic respiration rate of soil, with minor effect on total soil respiration. The monthly dynamics of soil respiration and temperature were largely consistent. There was a clear exponential relationship between soil respiration and soil temperature. Liming increased temperature sensitivity Q10 of soil respiration and autotrophic respiration but reduced that of soil heterotrophic respiration. In conclusion, liming promoted soil autotrophic respiration and strongly inhibited soil heterotrophic respiration in Chinese fir plantations, which would facilitate soil carbon sequestration.

Effects of Short-Term Nitrogen and Phosphorus Addition on Soil Respiration Components in a Subalpine Grassland of Qilian Mountains

In order to investigate the effects of short-term nitrogen and phosphorus addition on soil respiration and its components in a subalpine grassland located on the Qilian Mountains, a random block design of nitrogen[10 g·(m2·a)-1, N], phosphorus[5 g·(m2·a)-1, P], nitrogen and phosphorus addition[10 g·(m2·a)-1N and 5 g·(m2·a)-1P, NP], the control (CK), and complete control (CK') was conducted from June to August 2019, and total soil respiration and its component respiration rates were measured. The results showed that nitrogen addition reduced soil total respiration and heterotrophic respiration rates at a lower rate than P addition[-16.71% vs. -19.20%; -4.41% vs. -13.05%], but the rate of decrease in autotrophic respiration was higher than that of P addition (-25.03% vs. -23.36%); N and P mixed application had no significant effect on soil total respiration rate. The total soil respiration rate and its components were significantly exponentially correlated with soil temperature, and the temperature sensitivity of soil respiration rate was decreased by nitrogen addition (Q10:-5.64%-0.00%). P increased Q10 (3.38%-6.98%), and N and P reduced autotrophic respiration rate but increased heterotrophic respiration rate Q10 (16.86%) and decreased total soil respiration rate Q10 (-2.63%- -2.02%). Soil pH, soil total nitrogen, and root phosphorus content were significantly correlated with autotrophic respiration rate (P<0.05) but not with heterotrophic respiration rate, and root nitrogen content was significantly negatively correlated with heterotrophic respiration rate (P<0.05). In general, autotrophic respiration rate was more sensitive to N addition, whereas heterotrophic respiration rate was more sensitive to P addition. Both N and P addition significantly reduced soil total respiration rate, whereas N and P mixture did not significantly affect soil total respiration rate. These results can provide a scientific basis for the accurate assessment of soil carbon emission in subalpine grassland.

Responses of soil heterotrophic respiration and microbial biomass to organic and conventional production systems

The effects of organic and conventional production systems on crop productivity have been greatly explored, but their effects on soil microbial processes were often neglected. A comparative field study of organic and conventional production systems was conducted at the Tennessee State University research farm to determine soil heterotrophic respiration and microbial biomass carbon. Leafy green vegetables were grown in a conventional production system in an open field, and they were grown in an organic production system, using three different row covers (agribon cloth, insect net, and plastic), and in an open field. Soil samples (0-15cm) were collected from the two production systems. Soil heterotrophic respiration rate (RH), microbial biomass carbon (MBC), and biomass-specific heterotrophic respiration rate (the inverse is used as a proxy for microbial carbon use efficiency) were quantified. The results showed that the conventional production system significantly increased RH relative to the organic system. Organic production system, however, significantly enhanced MBC and reduced biomass-specific respiration rate indicating an increase in carbon use efficiency. Although MBC remained unchanged among the row covers, insect net increased RH and biomass-specific heterotrophic respiration rate. Our results suggest that the organic production system not only promoted soil microbial abundance but also limited soil heterotrophic respiration to the atmosphere governed by the elevated carbon use efficiency.

Biogeochemical and ecosystem properties in three adjacent semi‐arid grasslands are resistant to nitrogen deposition but sensitive to edaphic variability

AbstractDrylands have low nitrogen stocks and are predicted to be sensitive to modest increases in reactive nitrogen availability, but direct evidence that atmospheric nitrogen deposition will have sustained effects on dryland ecosystems is sparse and conflicting.We used three long‐running in situ nitrogen deposition simulation experiments and a complementary laboratory incubation experiment to address fundamental questions about how nitrogen inputs affect drylands: (1) What are the long‐ and short‐term consequences of nitrogen inputs for biogeochemical and ecosystem properties?; (2) Do these consequences depend on soil moisture availability?; and (3) Does soil texture modify the effects of nitrogen inputs and/or soil moisture availability?In 2011, we established three study sites along a soil texture gradient in Arches National Park with plots receiving 0, 2, 5 or 8 kg N ha−1annually (n = 5 per treatment per site). We assessed a suite of biogeochemical metrics over the long term and short term. To assess longer term effects, we sampled annually (2013–2019), just prior to spring nitrogen fertilization. To assess short‐term effects, we sampled immediately before and after spring nitrogen fertilization in 2013. Additionally, we compared foliar chemistry, soil extracellular enzyme activities, heterotrophic respiration rates, and nitrogen trace gas fluxes at select intervals during the study period (2011–2019). Finally, we conducted a laboratory incubation to measure the individual and interacting effects of soil moisture and nitrogen additions on soil microbial activity.We identified some short‐term effects in situ, but no lasting consequences of added nitrogen for any of the metrics measured. In the incubation, soil moisture treatments independently increased heterotrophic respiration rates but did not modify the effects of added nitrogen. In contrast to nitrogen treatments, soil texture was associated with large differences in biogeochemical cycling.Our results oppose the common prediction that coupled dryland biogeochemical cycles are sensitive to nitrogen inputs and suggest that fine‐scale edaphic heterogeneity is a key driver of dryland ecosystem properties.Synthesis. This study synthesizes a rare, long‐term dataset, which provides robust evidence that carbon and nutrient cycling and availability are resistant to realistic levels of atmospheric nitrogen deposition in remote dryland ecosystems.

Compositional stability of peat in ecosystem-scale warming mesocosms.

Peatlands historically have acted as a C sink because C-fixation rates exceeded the rate of heterotrophic decomposition. Under future warmer conditions predicted for higher latitudes, however, that balance may shift towards higher rates of heterotrophic respiration leading to the release of previously stored C as CO2 and CH4. The Spruce and Peatlands Response Under Changing Environments (SPRUCE) experiment is designed to test the response of peatlands to climate forcing using a series of warmed enclosures in combination with peat below-ground heating from 0 to +9°C above ambient conditions. This experimental design allowed a test of chemical changes occurring within peatland soils following five years of warming. We analyzed samples in the uppermost 2m of peat using Fourier Transform Infrared Spectroscopy (FT-IR) to quantify the relative abundance of carbohydrate and aromatic compounds in the peat. The peat soils were subjected to deep peat heating (DPH) beginning in June of 2014 followed by whole ecosystem warming (WEW) in August of 2015. We found that the relative amounts of labile and recalcitrant chemical compound groups across the full peat depth interval did not significantly change after five years of exposure to warming. This appears the case even though previous studies have shown that net C losses and loss of bulk peat mass to be instability over that time period. Results suggest that the current store of carbon in peatlands are largely compositionally stable leading to no changes the in the ratio of chemical moieties on the initial four-year timescale of this experiment.

Identification of varied soil hydraulic properties in a seasonal tropical rainforest

In forest areas, seasonal ecosystem changes may affect soil hydraulic properties and ultimately alter the pattern of soil moisture dynamics. A National Ecological Station in a tropical rainforest of Xishuangbanna located in southern China collected in-situ measurements of meteorological forcing, soil moisture content, litterfall, leaf area index (LAI), and water and carbon flux from 2003 to 2008, which provided an ideal dataset for a detailed investigation on how the soil hydraulic properties would vary in response to seasonal ecosystem changes. Methodologically, the Marquardt Levenberg optimization algorithm was integrated in an unsaturated flow model to inversely estimate the soil hydraulic parameters based on unvaried, seasonally varied, and monthly varied parameterization strategies, respectively. The results indicated that the simulated soil moisture using seasonally varied and monthly varied parameters were more accurate than that with unvaried parameters. Moreover, the statistical analysis of monthly varied soil hydraulic parameters suggested that the temporal variations in soil hydraulic properties were tightly related to the seasonal ecosystem changes in terms of LAI, litterfall, and heterotrophic respiration. In deciduous periods, a significant reduction of LAI was accompanied with abundant litterfall that replenished organic matter to the topsoil. In contrast, during the hot rainy periods, the high heterotrophic respiration rate indicated that the soil organic matter underwent intensive decomposition under the condition of high air temperature and wet soil moisture– leading to strong seasonal cycles in soil hydraulic properties. The seasonal ecosystem change led to a significant increase in saturated hydraulic conductivity Ks from less than 100 cm/day in hot rainy season to over 150 cm/day in cool dry season. Moreover, the inversely estimated soil hydraulic parameters of saturated water content θs and field capacity θf at the topsoil layer were also featured with clear seasonal cycles (ranging from 0.32 to 0.42 and 0.23 to 0.27 respectively). In comparison with unvaried soil hydraulic parameter, inclusion of varied soil hydraulic properties provided more accurate simulations of soil moisture dynamics, which in turn, benefited the hydro-ecological modeling in vegetated areas.

川中丘陵区冬水田种植模式转旱作土壤呼吸组分特征及碳平衡

PDF HTML阅读 XML下载 导出引用 引用提醒 川中丘陵区冬水田种植模式转旱作土壤呼吸组分特征及碳平衡 DOI: 10.5846/stxb202105281410 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: “十三五”国家重点研发计划"粮食丰产科技创新"专项项目(2017YFD0301702) Carbon balance and characteristics of soil respiration components during the transition from paddy field to upland in the hilly region of central Sichuan Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:冬水田-水稻是川中丘陵区传统的稻田种植模式,冬水田种植模式转变是实现多熟种植及机械化的重要途径。为探究冬水田-水稻种植模式转旱作过程中作物季及休闲期土壤呼吸速率及其组分构成,试验设置冬水田-水稻转旱作(FTD)、冬水田-水稻(FR)和冬闲田-玉米(FM)3种不同种植模式,采用根排除法和静态明箱-气相色谱法原位取样测定作物季及季后休闲期土壤呼吸及其组分,并通过测算净生态系统生产力(NEP)进而判断冬水田-水稻转旱作过程的农田系统碳汇强度。结果表明:(1)FTD显著提高了土壤总呼吸速率及其自养和异养呼吸速率,从而提高了其累积排放量(P<0.05)。与FR相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了13.14倍、11.32倍和15.56倍(P<0.05);与FM相比,FTD的土壤总呼吸及其自养和异养呼吸的累积排放量分别提高了70.56%、40.83%和115.47%(P<0.05)。(2)与FR和FM相比,FTD均降低了土壤呼吸及其组分的温度敏感性(Q10),且土壤总呼吸的温度敏感性介于异养呼吸和自养呼吸之间。(3)FR,FM和FTD的净生态系统生产力(NEP)均为正值,其数值分别为7911.66 kg/hm2,5667.89 kg/hm2和1583.46 kg/hm2,均表现为大气CO2的碳汇,但与FR与FM相比,FTD显著降低了其净生态系统生产力,呈现出较弱的碳汇。 Abstract:Winter paddy field-rice is a traditional rice planting pattern in the hilly areas of central Sichuan Province. The transformation of winter paddy field-rice planting pattern is an important measure to promote multi-cropping and mechanized cropping production. To investigate the soil respiration rate and its composition during crop season and fallow period during the transition from winter paddy field-rice to upland cropping (FTD), three different cropping patterns were set up in this experiment, including paddy field-rice to upland cropping (FTD), paddy field-rice (FR), and fallow field-corn (FM). Root removal method and static chamber gas chromatography were used to determine soil respiration and its components in crop season and fallow period after crop was harvested. The intensity of farmland carbon sink of FTD was evaluated by calculating net ecosystem productivity (NEP). The results showed that: (1) the total soil respiration rate, autotrophic respiration rate and heterotrophic respiration rate significantly increased in FTD than FR and FM (P<0.05). Compared with FR, the cumulative emissions amount of total soil respiration, autotrophic and heterotrophic respiration increased by 13.14 times, 11.32 times, and 15.56 times, respectively (P<0.05); Compared with FM, the cumulative emissions amount of the total soil respiration, autotrophic and heterotrophic respiration increased by 70.56%, 40.83% and 115.47%, respectively (P<0.05). (2) The respiration temperature sensitivity (Q10) value of total soil respiration, autotrophic respiration and heterotrophic respiration decreased in FTD than FR and FM. Meanwhile Q10 value of total soil respiration was between heterotrophic respiration Q10 value and autotrophic respiration Q10 value. (3) The NEP of FR, FM and FTD were positive, and their values were 7911.66 kg/hm2, 5667.89 kg/hm2 and 1583.46 kg/hm2, respectively. The three plant patterns were all the carbon sink of atmospheric CO2. Whereas, because the NEP in FTD was significantly lower than FR and FM, it only showed a weak carbon sink in FTD than that in FR and FM. 参考文献 相似文献 引证文献

Litter and microclimate controls on soil heterotrophic respiration after converting seasonal rainforests to rubber plantations in tropical China

Land-use changes can alter carbon cycling. Soil carbon loss resulting from the conversion of natural forests to rubber plantations (RP) may occur due to changes in litter inputs or in biotic and abiotic environmental conditions. In this study, we conducted a reciprocal soil and litter translocation mesocosm experiment for 15 months in a seasonal rainforest (SR) and RP to elucidate the effect of litter, soil and site conditions on heterotrophic respiration and its temperature sensitivity after land-use conversion. We found that rate of soil heterotrophic respiration (Rh) was higher at RP site than at SR site or for SR litter than RP litter with significant interactions between forest site and litter type, and did not differ between SR and RP soils. The Q10 values of Rh did not differ between forest sites, soils, or litter types but were substantially lower when litter was absent and substantially higher when RP soil was incubated in SR site and vice versa. Removal of surface litters led to a reduction of Rh by 27-45%. Soil labile organic C pool and microbial biomass were not influenced by litter type or forest site, but were influenced by soil origin, with higher values for SR soil than RP soil. Soil temperature and moisture were not influenced by litter type and soil but differed between forest sites with higher moisture at RP site than SR site. Our results suggested that changes in physical environmental conditions, rather than changes in litter input or soil biochemical properties, attributed to the elevated soil heterotrophic respiration in RP, resulting in soil carbon loss following the tropical land-use changes.

Effects of stand density on soil respiration and labile organic carbon in different aged Larix principis-rupprechtii plantations

BackgroundThe carbon pools of forest soils play a vital role in global carbon sequestration and emissions. Forest management can regulate the sequestration and output of forest soil carbon pools to a certain extent; however, the kinetics of the effects of forest density on soil carbon pools require further investigation.MethodsWe established sample plots with stand density gradients in three different aged Larix principis-rupprechtii plantations and quantified the soil respiration, soil organic carbon (SOC), soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), light fraction organic carbon (LFOC), and readily oxidized carbon (ROC).Results and conclusionsDuring the growth and development of plantations, stand density is an essential factor that impacts soil respiration and its associated elements. Moderate density was observed to promote both the soil and heterotrophic respiration rates and the sequestration of MBC and LFOC, whereas it inhibited the sequestration of ROC. The soil, heterotrophic, and autotrophic respiration rates of older forest stands were relatively rapid, whereas the contents of SOC, MBC, LFOC, DOC, and ROC were higher and more sensitive to changes in stand density. The MBC, LFOC, and ROC in soil labile organic carbon were closely related to both the soil and heterotrophic respiration, but not the SOC. Among them, the LFOC and MBC played the roles of “warehouse” and “tool” and were significantly correlated with soil and heterotrophic respiration. The ROC, as a “raw material”, exhibited a significantly negative correlation with the soil and heterotrophic respiration. When the soil and heterotrophic respiration rates were rapid, the ROC content in the soil maintained the low level of a “dynamically stabilized” state. The stand density regulated heterotrophic respiration by affecting the soil labile organic carbon, which provided an essential path for the stand density to regulate soil respiration.

Water availability regulates tree mixture effects on total and heterotrophic soil respiration: A three‐year field experiment

Soil respiration is of critical importance to the energy balance and element cycling of terrestrial ecosystems. Biodiversity loss and changes in rainfall regimes are predicted to increase, and in so doing have the potential to affect soil C cycling. However, uncertainties remain concerning the effects of tree diversity on soil respiration, and how these effects might be modified by altered water availability. Here, we measured the total soil respiration (RS) and heterotrophic respiration (RH) rates during the 2017 to 2019 growing seasons in stands dominated by Populus tremuloides, Pinus banksiana, and their relatively even mixtures under reduced (−25% throughfall), ambient, and added (+25% throughfall) precipitation in a boreal forest of Central Canada. We found that the RS and RH were 28% and 26% greater, respectively, in the mixtures than expected from those of monocultures that received ambient water availability, while the RH/RS were unaffected by tree mixtures. On average, the addition of water increased Rs and RH by 19%, and 10%, respectively, with more pronounced increases of Rs in tree mixtures, which resulted in 55% higher Rs in mixtures relative to monocultures. In contrast, water reduction did not affect the Rs but decreased RH in mixtures. Additionally, the effects of mixtures on RH increased over the three-year duration of the experiments. Both the Rs and RH decreased, while the RH/Rs increased with higher soil fungal to bacterial ratios. Our results revealed that plant species mixtures and water availability interactively influenced soil respiration under natural conditions. We provided novel experimental insights, which indicated that the establishment of diverse forests can increase soil C cycling over time, particularly under increased water availability.

Changes in the non-growing season soil heterotrophic respiration rate are driven by environmental factors after fire in a cold temperate forest ecosystem

Key messageDuring the non-growing season, environmental factors changed after fire, leading to significantly increased non-growing season soil heterotrophic respiration (Rh) and potentially decreasing the amount of net C stored in cold temperate forest ecosystems of China.ContextIntensifying forest fire regimes are likely to influence future C budgets of forest ecosystems. However, the mechanism of fire disturbance on the components of non-growing season soil respiration rate (Rs) and its environmental factors are not fully understood, creating uncertainties for future C sink estimates under climate change scenarios.AimsThis study examined the effects of recent fire on non-growing season (November 2017 to April 2018) Rs, its heterotrophic (Rh) and autotrophic (Ra) components, and Q10 in a cold temperate forest in northeast China.MethodsSoil CO2 effluxes (including Rh and Ra) were measured using an Li-8100 portable automatic measuring system for soil C flux (Li-Cor, Inc.; Lincoln, NE, USA). Soil temperature and moisture were measured using a temperature probe (Licor p/n8100–201) and soil volumetric water content probe (ECH20 167 EC-5; p/n 8,100,202), respectively, at a depth of 5 cm; snowpack depth was measured with a ruler.ResultsDuring the non-growing season, fire significantly increased the Rh by approximately 47% in burned stands. The Q10 of Rh significantly increased from 2.39 in the unburned stands to 3.12 in the burned stands. An interaction between soil temperature and snowpack depth was the driving environmental factor controlling the non-growing season soil respiration and its components after fire disturbance.ConclusionFire is a potent factor on the components of the soil respiration and should not be ignored in forest ecosystem C cycling, especially during the non-growing season as it is vulnerable to micro-environmental variation. Long-term studies involving diverse ecosystems are required to better elucidate mechanisms that have been found during the non-growing season Rs under an increasing trend of fire occurrence.

Respiration characteristics and its responses to hydrothermal seasonal changes in reconstructed soils

Seasonal changes in respiration and the components of four reconstructed soils (gravel + meteorite + lou; gravel + shale + lou; gravel + sand + lou; and gravel + soft rock + lou) in barren gravel land were monitored using the soil carbon flux measurement system. The results showed that (1) the monthly average respiration rate and the rates of the components in the four reconstructed soils were the highest in summer and lowest in winter. In winter, the monthly average respiration rates of the four reconstructed soils were not different (p > 0.05). In summer, the monthly average respiration rate of the sand or meteorite reconstructed soil was different from that of the other three (p < 0.05). (2) The heterotrophic and autotrophic respiration rates were different between the four reconstructed soils (p < 0.05). The contribution of heterotrophic respiration to total respiration in the four reconstructed soils was greater than that of autotrophic respiration throughout the year. In winter, autotrophic respiration accounts for the smallest proportion of total respiration. As the temperature rises, the proportion of autotrophic respiration to total respiration gradually increases and peaks in summer. In summer, the proportion of heterotrophic respiration in the total respiration is the smallest. With the decrease in temperature, the proportion of heterotrophic respiration in total respiration gradually increases and peaks in winter. (3) The maximum and minimum values of the monthly average respiration rate of the four reconstructed soils coincided with the months of maximum and minimum soil temperature. The soil volumetric water content changed with the amount of precipitation. The correlation between soil respiration and temperature was greater than that between soil respiration and volumetric water content. (4) The correlation in seasonal variation between respiration of the four remodelled soils and hydrothermal factors in the study area can be characterised by an exponential function and power-exponential function.

帽儿山3种森林生态系统土壤动物与土壤呼吸及其相互关系研究

PDF HTML阅读 XML下载 导出引用 引用提醒 帽儿山3种森林生态系统土壤动物与土壤呼吸及其相互关系研究 DOI: 10.5846/stxb201911252555 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31670619，41101048）；黑龙江省留学归国人员科学基金（LC2018011）；哈尔滨师范大学硕士研究生创新项目（HSDSSCX2019-01） Analysis on soil animals, soil respiration and the correlation in three forest ecosystems in Maoershan Author: Affiliation: Fund Project: Project of National Natural Science Foundation of China (31670619,41101048); Science Foundation of returned students of Heilongjiang Province (LC2018011); Innovation Project of postgraduates of Harbin normal University (HSDSSCX2019-01) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤呼吸是森林生态系统碳循环的关键过程，土壤动物可通过自身代谢及影响微生物活动调控土壤呼吸，因此研究土壤动物与土壤呼吸的相互关系对进一步揭示生态系统碳循环的规律和机理具有重要意义。通过野外定点，以帽儿山3种森林生态系统的土壤呼吸及土壤动物为研究对象，探讨不同森林生态系统的土壤呼吸、土壤动物个体密度和生物量的时间变化规律及二者相互关系。结果表明：（1）3种森林生态系统土壤总呼吸速率与土壤异养呼吸速率均呈现先增强后减弱的时间动态变化（P<0.05），且不同森林生态系统土壤异养呼吸速率差异显著（P<0.05），表现为硬阔叶林最高，红松人工林最低；（2）3种森林生态系统土壤动物生物量也具有显著的时间动态变化（P<0.05），均在9月份达到最大，且不同森林生态系统土壤动物个体密度显著不同（P<0.05），蒙古栎林土壤动物个体密度显著小于红松人工林与硬阔叶林；（3）通过回归分析可得，土壤动物数量及生物量的增加抑制了土壤呼吸速率，尤其在生长季初期、末期。研究表明土壤动物可通过抑制微生物生命活动和降低根系呼吸从而对土壤总呼吸及异养呼吸产生负反馈作用，三者是不可分割的整体，与土壤温度、水分等环境因子共同调控着土壤呼吸。 Abstract:Forest ecosystem is the largest organic carbon pool in terrestrial ecosystem, and its slight changes may cause significant variations in global climate. Soil respiration is the key ecological process of carbon cycle in forest ecosystem, which has a great influence on global climate change. Soil animals, as the important consumers of material cycle in the ecosystem, can regulate soil respiration the help of their own metabolism and affecting microbial activities. Therefore, study of the correlation of soil animals and soil respiration is of great significance to further reveal the law and mechanism of carbon cycle in ecosystem. Based on field experiment and indoor analysis, we chose soil respiration and soil animals in three forest ecosystems of Korean pine plantation forest (HS), Mongolian oak forest (MGL), and Hard-wood forest (YK) in Maoershan as the research object, and discuss the temporal variation and correlation between soil respiration as well as individual density or biomass of soil animals in different forest ecosystems. The results showed that: (1) the total soil respiration rate of the three forest ecosystems increased at first and then decreased (P<0.05), with the lowest value appearing in October. The soil heterotrophic respiration rate also showed significantly temporal dynamic change (P<0.05). The difference of soil heterotrophic respiration rate among different forest ecosystems was significant (P<0.05), which was the highest in Hard-wood forest and the lowest in Korean pine plantation forest. (2) The soil animal biomass and individual density of the three forest ecosystems also had notable temporal dynamic changes (P<0.05). The change trends of soil animal biomass and individual density were different, but they all had the maximum values in September. The individual density of soil animals in Mongolian oak forest was much lower than that in Korean pine plantation forest and Hard-wood forest. (3) Through regression analysis, the increase of the number and biomass of soil animals inhibited the soil respiration rate, especially at the beginning and end of the growing season. And the correlation between soil respiration and soil animals in Korean pine plantation forest was different from that in Mongolian oak forest and Hard-wood forest. It could be concluded that soil animals could produce negative feedback on total soil respiration and heterotrophic respiration by inhibiting microbial life activities and reducing root respiration. Soil animals, soil microorganisms and plant roots are an inseparable whole, which together with soil temperature, water and other environmental factors regulate soil respiration. 参考文献 相似文献 引证文献

Carbon Budget of an Agroforestry System after Being Converted from a Poplar Short Rotation Coppice

Poplar (Populus L. spp.) Short Rotation Coppice systems (SRCs) for bioenergy production are being converted back to arable land. Transitioning to Alley Cropping Systems (ACSs) could be a suitable strategy for integrating former tree rows and arable crops. A field trial (Pisa, Central Italy) was set up with the aim of assessing the C storage of an ACS system based on hybrid poplar and sorghum (Sorghum bicolor L. Moench) and comparing it with that of an SRC cultivation system. The carbon budget at the agroecosystem scale was assessed in the first year of the transition using the net biome production (NBP) approach with a simplified method. The overall NBP for the SRC was positive (96 ± 40 g C m−2 year−1), highlighting that the system was a net carbon sink (i.e., NBP &gt; 0). However, the ACS registered a net C loss (i.e., NBP &lt; 0), since the NBP was −93 ± 56 g C m−2 year−1. In the first year of the transition, converting the SRC into an ACS counteracted the potential beneficial effect of C storage in tree belowground biomass due to the high heterotrophic respiration rate recorded in the ACS, which was fostered by the incorporation of residues and tillage disturbance in the alley. Additional years of heterotrophic respiration measurements could allow for an estimate of the speed and extent of C losses.