Deep Autotrophic Soil Respiration in Shrubland and Woodland Ecosystems in Central New Mexico

Quantifying the controls on soil respiration is important for understanding ecosystem physiology and for predicting the response of soil carbon reservoirs to climate change. The majority of soil respiration is typically considered to occur in the top 20–30 cm of soils. In desert soils, where organic matter concentrations tend to be low and plants are deeply rooted, deeper respiration might be expected. However, little is known about the depth distribution of respiration in dryland soils. Here we show that the average depth of soil respiration between pulse precipitation events is almost always greater than 20 cm and is frequently greater than 50 cm in two central New Mexico desert shrublands. The average depth of soil respiration in a pi?on-juniper woodland was shallower, between 5 and 40 cm. In the shrublands, 8‰ seasonal variations in the carbon isotope composition of soil-respired CO₂ (δ¹³C_r-soil) that correlate with vapor pressure deficit support root/rhizosphere respiration as the dominant source of soil CO₂. Such deep autotrophic respiration indicates that shrubs preferentially allocate photosynthate to deep roots when conditions near the surface are unfavorable. Therefore, respiration rates in these soils are not necessarily correlated with root biomass. The δ¹³C_r-soil values provide no evidence for CO₂ evolved from soil inorganic carbon. Our results also suggest that organic carbon cycling is rapid and efficient in these soils and that the δ¹³C value of CO₂ respired from soils in much of the southwestern US, and perhaps in other semiarid regions, varies seasonally by at least 4‰.     

Dependence of Soil Respiration on Soil Temperature and Soil Moisture in Successional Forests in Southern China

The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured In three successional subtropical forests at the Dlnghuahan Nature Reserve （DNR） In southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and Its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared In successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season （April-September） and with low rates In the cool dry season （October-March）. Soil respiration measured at these forests showed a clear Increasing trend with the progressive succession. Annual mean （± SD） soil respiration rate In the DNR forests was （9.0 ± 4.6） Mg CO2-C/hm^2 per year, ranging from （6.1 ± 3.2） Mg CO2-C/hm^2 per year in early successional forests to （10.7 ± 4.9） Mg CO2-C/hm^2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation In DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture Increased with progressive succession processes. This increase is caused, in part, by abundant respirators In advanced-successional forest, where more soil moisture is needed to maintain their activities.     

中国农田土壤呼吸速率及驱动因子

土壤呼吸在全球碳收支中具有重要地位.研究中国典型农业区土壤呼吸的时空格局及影响因素,有助于构建区域尺度土壤呼吸定量评价模型,能够为评估中国乃至全球农业生态系统碳/源汇特征提供依据.本研究整合了2000~2012年中国农田生态系统土壤呼吸的主要研究成果,分析了华南、西南、华北、西北和东北5个典型农业区土壤呼吸的季节变化和区域差异,以及影响土壤呼吸的主要驱动因子.结果表明,5个典型农业区的土壤呼吸均存在明显的季节变化特征;中国农田生态系统年均土壤呼吸速率为(682.8±18.3)g C m?2.5个典型农业区年均土壤呼吸速率大小表现为华南区西南区华北区东北区西北区.全国农业土壤的年呼吸通量为(0.90±0.02)Pg C;水作和旱作两种土地利用类型间土壤呼吸速率差异显著(P0.05),旱作土壤呼吸速率约为水作的1.3倍;不同作物类型间土壤呼吸速率差异显著(P0.05),其排序为棉花玉米大豆水稻小麦;农田土壤呼吸与年均气温、土壤温度、土壤含水量和净初级生产力等影响因素呈显著正相关(P0.01),而与年均降水量的相关性不显著.     

Temperature Increases Soil Respiration Across Ecosystem Types and Soil Development,But Soil Properties Determine the Magnitude of This Effect

Ecosystems - Soil carbon losses to the atmosphere, via soil heterotrophic respiration, are expected to increase in response to global warming, resulting in a positive carbon-climate feedback....     

Soil Respiration in Different Agricultural and Natural Ecosystems in an Arid Region

The variation of different ecosystems on the terrestrial carbon balance is predicted to be large. We investigated a typical arid region with widespread saline/alkaline soils, and evaluated soil respiration of different agricultural and natural ecosystems. Soil respiration for five ecosystems together with soil temperature, soil moisture, soil pH, soil electric conductivity and soil organic carbon content were investigated in the field. Comparing with the natural ecosystems, the mean seasonal soil respiration rates of the agricultural ecosystems were 96%–386% higher and agricultural ecosystems exhibited lower CO₂ absorption by the saline/alkaline soil. Soil temperature and moisture together explained 48%, 86%, 84%, 54% and 54% of the seasonal variations of soil respiration in the five ecosystems, respectively. There was a significant negative relationship between soil respiration and soil electrical conductivity, but a weak correlation between soil respiration and soil pH or soil organic carbon content. Our results showed that soil CO₂ emissions were significantly different among different agricultural and natural ecosystems, although we caution that this was an observational, not manipulative, study. Temperature at the soil surface and electric conductivity were the main driving factors of soil respiration across the five ecosystems. Care should be taken when converting native vegetation into cropland from the point of view of greenhouse gas emissions.     

森林土壤氮素可利用性的影响因素研究综述

近几十年来 ,人类对木材、纤维和其他森林资源需求的急剧增加 ,对森林的集约化经营管理成为必然趋势。由于大部分森林生态系统缺乏Ｎ素 ,因此施肥成为经济有效的途径。但是 ,由于森林中的Ｎ肥利用效率低于农业系统 ,且Ｎ肥生产成本较高 ,易造成环境中多余Ｎ素的污染 ,所以需要更有效的经营管理方法。要改进这类方法 ,则必须很好地理解全球各种森林生态系统的Ｎ素循环和Ｎ素可利用性[3 1] 。可利用性养分 (ａｖａｉｌａｂｌｅｎｕｔｒｉｅｎｔ)是指土壤中易被植物吸收同化的养分元素或化合物的数量[4 0 ] ,可以理解为植物利用土壤中易吸收和…     

Long-Term Nitrogen Storage and Soil Nitrogen Availability in Post-Fire Lodgepole Pine Ecosystems

Long-term, landscape patterns in inorganic nitrogen (N) availability and N stocks following infrequent, stand-replacing fire are unknown but are important for interpreting the effect of disturbances on ecosystem function. Here, we present results from a replicated chronosequence study in the Greater Yellowstone Ecosystem (Wyoming, USA) directed at measuring inorganic N availability (ion-exchange resin bags) and ecosystem N pools among 77 lodgepole pine stands that varied in age and density. Inorganic N availability ranged from 0.07 to 3.20 μN bag⁻¹ d⁻¹ and nitrate (NO₃⁻) was, on average, 65% of total resin-sorbed N. Total ecosystem N stocks (live + detrital + soil) averaged 109.9 ± 3.0 g N m⁻² (range = 63.7–185.8 g N m⁻²). Live N was 14%, detrital N was 29%, and soil N was 57% of total stocks. Soil NO₃⁻, total ecosystem N, live N, and detrital N generally increased with stand age, but soil N stocks decreased. Models (AIC_c) to predict soil N availability and N stocks included soil P, soil Ca, bulk density, and pH in addition to age (adj R ² ranged from 0.18 to 0.53) and density was included only for live N stocks. Patterns of N stocks and N availability with density were strongest for young stands (<20 years) regenerating from extensive fire in 1988; for example, litterfall N stocks increased with density (adj R ² = 0.86, P < 0.001) but inorganic N availability declined (adj R ² = 0.47, P < 0.003). Across the complex Yellowstone landscape, we conclude that N stocks and N availability are best predicted by a combination of local soil characteristics in addition to factors that vary at landscape scales (stand density and age). Overall, total ecosystem N stocks were recovered quickly following stand-replacing fire, suggesting that moderate increases in fire frequency will not affect long-term landscape N storage in Greater Yellowstone. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author contributions   EAHS, MGT, and MGR conceived the study; DMK performed field research; EAHS and DMK oversaw laboratory analyses and analyzed data; EAHS wrote the paper.     

The Antibiotic-Aided Distinguishing of Fungal and Bacterial Substrate-Induced Respiration in Various Soil Ecosystems

Fungal and bacterial substrate-induced respiration have been distinguished in gray forest and chestnut soils in various ecosystems (forest, grassland, arable soil, fallow land, and shelterbelt) using the antibiotics cycloheximide and streptomycin. The optimal inhibitory concentrations of the antibiotics, added separately and in combination; the preincubation time of the antibiotics with the soil before glucose addition; and the mass of added inert material (talc) have been determined. The inhibitor additivity ratio (IAR) has been calculated for the antibiotics. With the IAR differing from 1.0 by a value of more than 5%, the fungal and bacterial substrate-induced respiration cannot be distinguished reliably. Respiration measurements show that the microbial communities of natural ecosystems are dominated by fungi (81–95% on average). The smallest amount of fungi (54–59%) is found in the arable soil ecosystem.__________Translated from Mikrobiologiya, Vol. 74, No. 3, 2005, pp. 394–400.Original Russian Text Copyright © 2005 by Susyan, Ananyeva, Blagodatskaya.     

The Dependence of Crustacean Respiration Rate on Body Mass and Habitat Temperature

The respiratorion rates of Crustacea from temperate and tropical waters of the Atlantic Ocean were measured directly at habitat temperatures of 19, 25 and 29 °C. The results were analysed together with data obtained from similar investigations in previous years (Ivleva, 1977) on Crustacea from moderately cold and polar latitudes at 10, 6 and 0 °C. Variations of the values for A and k in generalized regressions (R = AWκ) for Crustacea within the temperature limits of the physiological range were shown to have quite a clear-cut and regular character. The coefficient k varied from 0.60 to 0.79 and revealed a tendency to increase as temperatures decreased. The value of A increased with rising temperature within all intervals from 0 to 30 °C. The quantitative relationship between respiration rate and temperature was evaluated by the Arrhenius equation. Statistical processing of resultant data indicated a rather close association between log A and the habitat temperature of the Crustacea but only slight deviations from the theory of empirically found values. The accelerating effect of temperature (μ) was 13 ± 0.13 keal/mol. This value was used to calculate Q₁₀, which was more convenient for practical purposes.     

Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply

Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R _s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R _s ( ), R _s at a reference soil temperature (10°C; ) and annual R _s (estimated for 13 sites) ranged from 1.9 to 15.9 μmol CO₂ m⁻² s⁻¹, 0.3 to 5.5 μmol CO₂ m⁻² s⁻¹ and 58 to 1988 g C m⁻² y⁻¹, respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites was closely related to . Assimilate supply affected R _s at timescales from daily (but not necessarily diurnal) to annual. Reductions of assimilate supply by removal of aboveground biomass through grazing and cutting resulted in a rapid and a significant decrease of R _s. Temperature-independent seasonal fluctuations of R _s of an intensively managed pasture were closely related to changes in leaf area index (LAI). Across sites increased with mean annual soil temperature (MAT), LAI and gross primary productivity (GPP), indicating that assimilate supply overrides potential acclimation to prevailing temperatures. Also annual R _s was closely related to LAI and GPP. Because the latter two parameters were coupled to MAT, temperature was a suitable surrogate for deriving estimates of annual R _s across the grasslands studied. These findings contribute to our understanding of regional patterns of soil C fluxes and highlight the importance of assimilate supply for soil CO₂ emissions at various timescales.     

羊草呼吸作用与湿度、光照和土壤水分的关系

本文报道了两种土壤水分条件下羊草明呼吸速率与光照和温度的关系,以及暗呼吸速率与温度的关系。结果表明,羊草的明呼吸速率与光强呈非线性函数关系。在低光强下,明呼吸速率随光强升高而有较快的增加;随着光强的增高,其增加速度减慢。在温度低于羊草光合的高温补偿点的条件下,明呼吸速率在一定温度范围内随温度升高而增大;当温度达到一定限度时,有一个下降阶段,而后又回升,羊草的暗呼吸速率随温度增加而升高,且在一定限度内,其升高速度随温度增高而加快。当土壤干旱时,明呼吸速率显著降低,而暗呼吸速率仅略有减小。     

Seasonal Patterns of Root Production with Water and Nitrogen Additions Across Three Dryland Ecosystems

Ecosystems - Root production is known to contribute at least 50% of total net primary production in dryland ecosystems, yet few studies have addressed seasonal dynamics of root production or the...     

Availability of Fenamiphos and its Metabolites to Soil Water

Field and greenhouse experiments were conducted to determine the extent to which fenamiphos and its degradation products, fenamiphos sulfoxide and fenamiphos sulfone, are available to contact nematodes in the soil. Water extraction provided a relative measure of each chemical''s availability to the soil water where the chemicals could contact nematodes, and methanol extraction provided a relative measure of the total amount of each chemical present in the soil. Only small amounts of fenamiphos and fenamiphos sulfone could be extracted by water, even when much larger amounts were present in the soil. In contrast, virtually all of the fenamiphos sulfoxide present in the soil was extractable by water several days after nematicide application. Three days after fenamiphos (3EC) was applied at 6.7 kg a.i./ha to field plots, 6.4% of the fenamiphos, 14.4% of the fenamiphos sulfone, and 100% of the fenamiphos sulfoxide present in the soil was extracted by water. In greenhouse experiments with soil from these field plots, a 15G formulation of fenamiphos containing 98.7% fenamiphos and 1.3% fenamiphos sulfoxide was added to the soil. After an initial period of 3-4 days, the sulfoxide which formed by oxidation of fenamiphos became completely available for water extraction, whereas fenamiphos remained relatively unextractable by water. Fenamiphos sulfoxide is much more available to soil water, thus available for contact with nematodes, than are fenamiphos or fenamiphos sulfone. Based on this availability in water, it seems likely that fenamiphos sulfoxide is the major component for controlling nematodes.     

Sensitivity of Soil Respiration to Variability in Soil Moisture and Temperature in a Humid Tropical Forest

Precipitation and temperature are important drivers of soil respiration. The role of moisture and temperature are generally explored at seasonal or inter-annual timescales; however, significant variability also occurs on hourly to daily time-scales. We used small (1.54 m²), throughfall exclusion shelters to evaluate the role soil moisture and temperature as temporal controls on soil CO₂ efflux from a humid tropical forest in Puerto Rico. We measured hourly soil CO₂ efflux, temperature and moisture in control and exclusion plots (n = 6) for 6-months. The variance of each time series was analyzed using orthonormal wavelet transformation and Haar-wavelet coherence. We found strong negative coherence between soil moisture and soil respiration in control plots corresponding to a two-day periodicity. Across all plots, there was a significant parabolic relationship between soil moisture and soil CO₂ efflux with peak soil respiration occurring at volumetric soil moisture of approximately 0.375 m³/m³. We additionally found a weak positive coherence between CO₂ and temperature at longer time-scales and a significant positive relationship between soil temperature and CO₂ efflux when the analysis was limited to the control plots. The coherence between CO₂ and both temperature and soil moisture were reduced in exclusion plots. The reduced CO₂ response to temperature in exclusion plots suggests that the positive effect of temperature on CO₂ is constrained by soil moisture availability.     

Confounding Effects of Soil Moisture on the Relationship Between Ecosystem Respiration and Soil Temperature in Switchgrass

Understanding the response of ecosystem respiration (ER) to major environmental drivers is critical for estimating carbon sequestration and large-scale modeling research. Temperature effect on ER is modified by other environmental factors, mainly soil moisture, and such information is lacking for switchgrass (Panicum virgatum L.) ecosystems. The objective of this study was to examine seasonal variation in ER and its relationship with soil temperature (T _s) and moisture in a switchgrass field. ER from the nighttime net ecosystem CO₂ exchange measurements by eddy covariance system during the 2011 and 2012 growing seasons was analyzed. Nighttime ER ranged from about 2 (early growing season) to as high as 13 μmol m^?2 s^?1 (peak growing period) and showed a clear seasonality, with low rates during warm (>30 °C) and dry periods (<0.20 m³ m^?3 of soil water content). No single temperature or moisture function described variability in ER on the seasonal scale. However, an exponential temperature–respiration function explained over 50 % of seasonal variation in ER at adequate soil moisture (>0.20 m³ m^?3), indicating that soil moisture <0.20 m³ m^?3 started to limit ER. Due to the limitation of soil–atmosphere gas exchange, ER rates declined markedly in wet soil conditions (>0.35 m³ m^?3) as well. Consequently, both dry and wet conditions lowered temperature sensitivity of respiration (Q ₁₀). Stronger ER–T _s relationships were observed at higher soil moisture levels. These results demonstrate that soil moisture greatly influences the dynamics of ER and its relationship with T _s in drought prone switchgrass ecosystems.     

Soil Respiration in the Cold Desert Environment of the Colorado Plateau (USA): Abiotic Regulators and Thresholds

Decomposition is central to understanding ecosystem carbon exchange and nutrient-release processes. Unlike mesic ecosystems, which have been extensively studied, xeric landscapes have received little attention; as a result, abiotic soil-respiration regulatory processes are poorly understood in xeric environments. To provide a more complete and quantitative understanding about how abiotic factors influence soil respiration in xeric ecosystems, we conducted soil- respiration and decomposition-cloth measurements in the cold desert of southeast Utah. Our study evaluated when and to what extent soil texture, moisture, temperature, organic carbon, and nitrogen influence soil respiration and examined whether the inverse-texture hypothesis applies to decomposition. Within our study site, the effect of texture on moisture, as described by the inverse texture hypothesis, was evident, but its effect on decomposition was not. Our results show temperature and moisture to be the dominant abiotic controls of soil respiration. Specifically, temporal offsets in temperature and moisture conditions appear to have a strong control on soil respiration, with the highest fluxes occurring in spring when temperature and moisture were favorable. These temporal offsets resulted in decomposition rates that were controlled by soil moisture and temperature thresholds. The highest fluxes of CO₂ occurred when soil temperature was between 10 and 16 °C and volumetric soil moisture was greater than 10%. Decomposition-cloth results, which integrate decomposition processes across several months, support the soil-respiration results and further illustrate the seasonal patterns of high respiration rates during spring and low rates during summer and fall. Results from this study suggest that the parameters used to predict soil respiration in mesic ecosystems likely do not apply in cold-desert environments.     

Broad-Scale Patterns of Soil Carbon (C) Pools and Fluxes Across Semiarid Ecosystems are Linked to Climate and Soil Texture

Ecosystems - Dryland (semiarid and arid) ecosystems are responsible for most of the interannual variation in atmospheric CO2 concentrations and contain a considerable fraction of the globe’s...     

Ecology of Soil Erosion in Ecosystems

Each year, about 75 billion tons of soil are eroded from the world's terrestrial ecosystems. Most agricultural land in the world is losing soil at rates ranging from 13 tons/ha/year to 40 tons/ha/year. Because soil is formed very slowly, this means that soil is being lost 13–40 times faster than the rate of renewal and sustainability. Rain and wind energy are the two prime causes of erosion from tilled or bare land. Erosion occurs when the soil lacks protective vegetative cover. Soil erosion reduces the productivity of the land by loss of water, soil organic matter, nutrients, biota, and depth of soil. The greatest threat to providing food for a rapidly growing human population is soil erosion. Abandoned, eroded agricultural land is replaced by clearing forested ecosystems. Received 17 February 1998; accepted 26 May 1998.