高浓度CO2下长白松幼苗土壤和根系呼吸

The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil respiration during seedling growth of Pinus sylvestris vat. sylvestriformis. During the four growing seasons （May-October） from 1999 to 2003, the seedlings were exposed to elevated concentrations of CO2 in open-top chambers. The total soil respiration and contribution of root respiration were measured using an LI-6400-09 soil CO2 flux chamber on June 15 and October 8, 2003. To separate root respiration from total soil respiration, three PVC cylinders were inserted approximately 30 cm deep into the soil in each chamber. There were marked diurnal changes in air and soil temperatures on June 15. Both the total soil respiration and the soil respiration without roots showed a strong diurnal pattern, increasing from before sunrise to about 14：00 in the afternoon and then decreasing before the next sunrise. No increase in the mean total soil respiration and mean soil respiration with roots severed was observed under the elevated CO2 treatments on June 15, 2003, as compared to the open field and control chamber with ambient CO2. However, on October 8, 2003, the total soil respiration and soil respiration with roots severed in the open field were lower than those in the control and elevated CO2 chambers. The mean contribution of root respiration measured on June 15, 2003, ranged from 8.3% to 30.5% and on October 8, 2003, from 20.6% to 48.6%.     

Root-derived respiration and non-structural carbon of rice seedlings

Various methods have been suggested to separate root and microbial contributions to soil respiration. However, to date there is no ideal approach available to partition below-ground CO₂ fluxes in its components although the combination of traditional methods with approaches based on isotopes seems especially promising for the future improvement of estimates. Here we provide evidence for the applicability of a new approach based on the hypothesis that root-derived (rhizomicrobial) respiration, including root respiration and CO₂ derived from microbial activity in the immediate vicinity of the root, is proportional to non-structural carbon contents (sugars and organic acids) of plant tissues. We examined relationships between root-derived CO₂ and non-structural carbon of rice (Oryza sativa) seedlings using ¹⁴C pulse labelling techniques, which partitioned the ¹⁴C fixed by photosynthesis into root-derived ¹⁴CO₂, and ¹⁴C in sugars and organic acids of roots and shoots. After the ¹⁴C pulse ¹⁴C in both sugars and organic acids of plant tissues decreased steeply during the first 12 h, and then decreased at a lower rate during the remaining 60 h. Soil ¹⁴CO₂ efflux and soil CO₂ efflux strongly depended on ¹⁴C pools in non-structural carbon of the plant tissues. Based on the linear regression between root-derived respiration and total non-structural carbon (sugars and organic acids) of roots, non-rhizomicrobial respiration (SOM-derived) was estimated to be 0.25 mg C g⁻¹ root d.w. h⁻¹. Assuming the value was constant, root-derived respiration contributed 85–92% to bulk soil respiration.     

Sources of CO2 efflux from soil and review of partitioning methods

Five main biogenic sources of CO₂ efflux from soils have been distinguished and described according to their turnover rates and the mean residence time of carbon. They are root respiration, rhizomicrobial respiration, decomposition of plant residues, the priming effect induced by root exudation or by addition of plant residues, and basal respiration by microbial decomposition of soil organic matter (SOM). These sources can be grouped in several combinations to summarize CO₂ efflux from the soil including: root-derived CO₂, plant-derived CO₂, SOM-derived CO₂, rhizosphere respiration, heterotrophic microbial respiration (respiration by heterotrophs), and respiration by autotrophs. These distinctions are important because without separation of SOM-derived CO₂ from plant-derived CO₂, measurements of total soil respiration have very limited value for evaluation of the soil as a source or sink of atmospheric CO₂ and for interpreting the sources of CO₂ and the fate of carbon within soils and ecosystems. Additionally, the processes linked to the five sources of CO₂ efflux from soil have various responses to environmental variables and consequently to global warming. This review describes the basic principles and assumptions of the following methods which allow SOM-derived and root-derived CO₂ efflux to be separated under laboratory and field conditions: root exclusion techniques, shading and clipping, tree girdling, regression, component integration, excised roots and insitu root respiration; continuous and pulse labeling, ¹³C natural abundance and FACE, and radiocarbon dating and bomb-¹⁴C. A short sections cover the separation of the respiration of autotrophs and that of heterotrophs, i.e. the separation of actual root respiration from microbial respiration, as well as methods allowing the amount of CO₂ evolved by decomposition of plant residues and by priming effects to be estimated. All these methods have been evaluated according to their inherent disturbance of the ecosystem and C fluxes, and their versatility under various conditions. The shortfalls of existing approaches and the need for further development and standardization of methods are highlighted.     

Diurnal and seasonal carbon dioxide exchange and its components in temperate grasslands in the Netherlands — an outline of the methodology

A methodological outline is presented of a study into the diurnal and seasonal cycle of carbon fluxes within grassland ecosystems in the Netherlands in relation to their environment. At experimental sites Lelystad and Zegveld ?redominantlyLolium perenne L. at a clay and peat soil, respectively — measurements will be made on (1) net CO₂ assimilation of the grassland vegetation using infrared gas analysis; (2) carbon distribution within the plant using¹⁴C pulse labeling; and (3) carbon and CO₂ fluxes associated with root respiration and soil organic matter decomposition using¹⁴C pulse labeling. At both sites and at experimental site Cabauw additional measurements will be made on total CO₂ fluxes between the grassland vegetation and the lower part of the atmospheric boundary layer. For the analysis of the experimental results and generalisation of the relationships between carbon fluxes and environmental and plant factors use will be made of dynamic simulation models of grass growth and soil organic matter dynamics.     

Microbial activity and functional composition among northern peatland ecosystems

The extent to which complex interrelationships between plants and microorganisms influence organic matter dynamics is critical to our understanding of global C cycles in changing environments. We examined the hypothesis that patterns of soil microbial activity and functional composition differ among vegetation types in northern peatland ecosystems. Microbial characteristics were compared among peatlands differing in plant growth form (tree, shrub/moss, sedge) in two regions (New York State and West Virginia). Microbial activity (basal respiration) was greater in surface (0-15 cm) than subsurface (15-30 cm) peat and from sites dominated by shrubs and Sphagnum moss (3.9±0.65 μg C g⁻¹ h⁻¹) compared to forested (1.8±0.20 μg C g⁻¹ h⁻¹) or sedge-dominated sites (1.9±0.38 μg C g⁻¹ h⁻¹). Microbial activity was not related to decomposability of peat organic matter among vegetation types, and activity was unexpectedly higher in sites with lower peat pH and higher water table level. Substrate-induced respiration (SIR) did not show a clear pattern among vegetation types, but was greater in surface than subsurface peat. Microbial responsiveness to added glucose was very low. The ratio of basal respiration to SIR varied between 0.39 and 0.72 and, like activity, was highest in shrub/Sphagnum sites. Microbial substrate utilization patterns (assayed with BIOLOG^® GN plates) also differed between shrub/Sphagnum sites and forest or sedge sites, suggesting that C fluxes were mediated by different assemblages of microorganisms in shrub/Sphagnum peatlands. Principal component (PC) scores indicated more utilization of N-containing compounds and carboxylic acids, and less utilization of carbohydrates by microbial communities in shrub/Sphagnum sites. PC scores were much more variable both within and among vegetation types for sites in West Virginia than in New York State, and a greater diversity of C sources were utilized in WV (57±3) than NYS (47±2) peat. Our results suggest a link between microbial respiratory activity and microbial functional composition as they vary among these peatland vegetation types.     

CO2 fluxes and evaporation on a peatland in the Netherlands appear not affected by water table fluctuations

The effect of shallow water table fluctuations on the evaporation and CO₂ fluxes in a peatland is investigated. The fluxes of evaporation and net ecosystem exchange of carbon were measured from mid-spring to the end of summer in 2005 and 2006 and simulated independently with process models. The observed and modelled data were then compared along a gradient of water levels. Any variation along the gradient would imply an influence of the water table on the flux. It became evident that changes in the water table had no effect on the evaporation and CO₂ fluxes of the peatland. A probable cause could be the high water content of the soil, even for the low water tables, and the stable thermal conductivity of the soil. This study has implications for current land use management, which is aimed at reducing CO₂-emissions. Regulations are currently concerned with water table while this study shows that soil water content should be focused on as well.     

Seasonal pattern of total soil respiration in undisturbed and disturbed ecosystems of Central Himalaya

Summary The rates of CO₂ efflux were measured by an alkali absorption method (using 20 ml 0.5 N NaOH) from soils in four undisturbed sites [two evergreen oak forests, Quercus floribunda Lindl. (tilonj oak), Quercus leucotrichophora A Camus (banj oak), and two evergreen conifer forests, Cedrus deodara Loud. (deodar forest) and Pinus roxburghii Sarg. (chir pine forest)] and three disturbed sites. The sites were located between elevations of 1850 and 2360 m in the Central Himalaya. The seasonal pattern of soil respiration was similar in all the sites with a maximum during the rainy season, intermediate rates during the summer season and the lowest level of activity in winter. The rate of CO₂ efflux was higher in broadleaf than in conifer forests, and it was lowest in the disturbed sites. Among the edaphic conditions, soil moisture, N, organic C, pH, soil porosity, and root biomass positively affected total soil respiration. The proportion of root respiration to total soil respiration was higher in the disturbed sites than the undisturbed sites in winter. Conditions in the winter season were less favourable for microbial respiration than for root respiration.     

Decomposition of organic matter in peat soil in a minerotrophic mire

Decomposition of organic materials, oxygen consumption, and carbon dioxide emission were investigated in Masukata mire, a small minerotrophic mire in central Japan. We selected three dominant community types in the mire, a Sphagnum palustre community, a Phragmites australis community, and an Alnus japonica community, for the decomposition study sites. Decomposition rates were measured in the field by examining mass loss of peat and cellulose for 6 months. The oxygen consumption rate was measured in the field using a closed chamber equipped with an oxygen electrode. The carbon dioxide emission rate of the peat was measured by an infrared gas analyser in the laboratory under controlled conditions. Results of these measurements were tested by correlation analysis. The rate of mass loss of peat positively correlated with the CO₂ emission rate. The cellulose decomposition rate showed significant differences among community types, and it had significant positive correlation with the oxygen consumption rate. Although oxygen consumption measurement is not generally used to estimate peatland soil respiration, the oxygen consumption method can be used for predicting long-term decomposition rate according to different vegetation types within a short time.     

Plant-derived CO2 flux from cultivated peat soils

Abstract

Methods used to estimate the CO₂ emission from soil commonly measure the total CO₂ flux. To be able to quantify the net CO₂ emission from cultivated peat soils there is a need to distinguish between soil organic matter-derived CO₂ respiration and plant-derived respiration. In this investigation we used the root exclusion method to separate the plant-derived respiration from total CO₂ emission. The plant-derived contribution was estimated to be between 27 and 63% of total CO₂ emission depending on soil type and season. We also found a relationship between soil temperature, biomass growth and CO₂ efflux, which can be used to estimate plant-derived respiration. Due to the priming effect the root exclusion method is less reliable late in the season.     

Soil respiration rate and its sensitivity to temperature in pasture systems of dry-tropics

Abstract

Tree clearing is a topical issue the world over. In Queensland, the high rates of clearing in the past were mainly to increase pasture production. The present research evaluates the impact of clearing on some soil biological properties, i.e. total soil respiration, root respiration, microbial respiration, and microbial biomass (C and N), and the response of soil respiration to change in temperature.

In-field and laboratory (polyhouse) experiments were undertaken. For in-field studies, paired cleared and uncleared pasture plots were selected to represent three major tree communities of the region, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared sites were chosen to represent three different time-since-clearing durations (5, 11–13, and 33 years; n=18 for cleared and uncleared plots) to determine the temporal impact of clearing on soil biological properties. Experiments were conducted in the polyhouse to study in detail the response of soil respiration to changes in soil temperature and soil moisture, and to complement in-field studies for estimating root respiration.

The average rate of CO₂ emission was 964 g CO₂/m²/yr, with no significant difference (P<0.05) among cleared and uncleared sites. Microbial respiration and microbial biomass were greater at uncleared compared with those at cleared sites. The Q ₁₀-value of 1.42 (measured for different seasons in a year) for in-field measurements suggested a small response of soil respiration to soil temperature, possibly due to the limited availability of soil moisture and/or organic matter. However, results from the polyhouse experiment suggested greater sensitivity of root respiration to temperature change than for total soil respiration. Since root biomass (herbaceous roots) was greater at the cleared than at uncleared sites, and root respiration increased with an increase in temperature, we speculate that with rising ambient temperature and consequently soil temperature, total soil respiration in cleared pastures will increase at a faster rate than that in uncleared pastures.     

Collar insertion depth effects on soil respiration in afforested peatlands

Using collars for measuring soil respiration and its component fluxes in closed chamber systems relies on two main assumptions. Firstly, it is assumed that shallow collars prevent lateral soil gas leakage beneath the chamber’s walls and the underestimation of soil CO₂ fluxes, and secondly, the insertion of deeper collars excises all living roots and the autotrophic flux is eliminated. It was hypothesised that previous findings on collar insertion impacts on autotrophic and total soil respiration also apply to afforested peatlands. In these ecosystems, a large fraction of fine roots grow close to the soil surface. Therefore, the use of shallow collars may sever some fine roots and hyphae of mycorrhizal fungi, and therefore, it may lead to underestimation of total soil respiration. It was also hypothesised that this underestimation may be greater than a possible CO₂ leakage from lateral diffusion of soil gas as a result of not using collars. In this study, we measured soil CO₂ efflux in a Sitka spruce and a lodgepole pine plantation on blanket peat in southern Ireland. A surface collar (not inserted into the ground) and six insertion depths (5, 10, 15, 25, 35 and 45 cm) were established to assess the effect of the collar insertion depth on autotrophic and total soil respiration. The insertion depth of 5 cm reduced total soil respiration by 47 and 32% in the spruce and pine stands, respectively. Using nonlinear equations, it was estimated that a frequently used shallow insertion of 1.5 cm would have reduced this efflux by 35 and 20% in each stand, respectively. Moreover, it was demonstrated that this reduction was greater than a possible lateral soil gas leakage. These results suggest that the insertion of shallow collars should be avoided and surface collars permanently anchored in the soil should be used instead.     

Partitioning CO2 Respiration among Soil,Rhizosphere Microorganisms,and Roots of Wheat under Greenhouse Conditions

Abstract

The measurement of soil, root, and rhizomicrobial respiration has become very important in evaluating the role of soil on atmospheric carbon dioxide (CO₂) concentration. The objective of this study was to partition root, rhizosphere, and nonrhizosphere soil respiration during wheat growth. A secondary objective was to compare three techniques for measuring root respiration: without removing shoot of wheat, shading shoot of wheat, and removing shoot of wheat. Soil, root, and rhizomicrobial respiration were determined during wheat growth under greenhouse conditions in a Carwile loam soil (fine, mixed, superactive, thermic Typic Argiaquolls). Total below ground respiration from planted pots increased after planting through early boot stage and then decreased through physiological maturity. Root‐rhizomicrobial respiration was determined by taking the difference in CO₂ flux between planted and unplanted pots. Also, root and rhizomicrobial respirations were directly measured from roots by placing them inside a Mason jar. It was determined that root‐rhizomicrobial respiration accounted for 60% of total CO₂ flux, whereas 40% was from heterotrophic respiration in unplanted pots. Rhizomicrobial respiration accounted for 18 to 25% of total CO₂ flux. Shade and no‐shoot had similar effects on root respiration. The three techniques were not significantly different (p>0.05).     

Clear‐cutting and slash burning effects on soil CO2 efflux partitioning in Chinese fir and evergreen broadleaved forests in subtropical China

Clear‐cutting (CC) and slash burning (SB) are common silvicultural practices in subtropical China, yet the time‐course response of soil CO₂ efflux components to such disturbance is not well understood. This study examined the effects of CC and SB on soil CO₂ efflux components in a Cunninghamia lanceolata (Lamb.) Hook (Chinese fir, CF) plantation and a secondary evergreen broadleaved forest (BF) located in Fujian Province, southeastern China. Aboveground litter removal and root trenching were used to estimate CO₂ fluxes from soil organic matter decomposition (R_SOM), litter decomposition (R_L), and autotrophic respiration by roots and mycorrhizae (R_R). These components were measured 5–7 times per month from 18 October 2001 to 25 December 2003 using soda lime absorption. We found that R_R, R_L and R_SOM were initially higher in CC and SB plots than controls in both forests, but these three component fluxes in disturbed plots all fell below those of the control 5–20 months after the disturbance. Also, Q₁₀ values of these components decreased following disturbance. The annual flux of each respiration component was greater under BF than CF. The contribution of R_R to soil CO₂ efflux in the control plots averaged 35% in CF and 46% in BF. R_SOM was the dominant component of soil CO₂ efflux in CC and SB plots, accounting for over 50%. Our results highlight the importance of temporal trends of the component fluxes following disturbance and contribute to a broader understanding of forest management effects on the soil C cycle.     

Variation of soil respiration at three spatial scales: Components within measurements, intra-site variation and patterns on the landscape

Soil respiration is an important component of terrestrial carbon cycling and can be influenced by many factors that vary spatially. This research aims to determine the extent and causes of spatial variation of soil respiration, and to quantify the importance of scale on measuring and modeling soil respiration within and among common forests of Northern Wisconsin. The potential sources of variation were examined at three scales: [1] variation among the litter, root, and bulk soil respiration components within individual 0.1 m measurement collars, [2] variation between individual soil respiration measurements within a site (<1 m to 10 m), and [3] variation on the landscape caused by topographic influence (100 m to 1000 m). Soil respiration was measured over a two-year period at 12 plots that included four forest types. Root exclusion collars were installed at a subset of the sites, and periodic removal of the litter layer allowed litter and bulk soil contributions to be estimated by subtraction. Soil respiration was also measured at fixed locations in six northern hardwood sites and two aspen sites to examine the stability of variation between individual measurements. These study sites were added to an existing data set where soil respiration was measured in a random, rotating, systematic clustering which allowed the examination of spatial variability from scales of <1 m to 100+ m. The combined data set for this area was also used to examine the influence of topography on soil respiration at scales of over 1000 m by using a temperature and moisture driven soil respiration model and a 4 km² digital elevation model (DEM) to model soil moisture. Results indicate that, although variation of soil respiration and soil moisture is greatest at scales of 100 m or more, variation from locations 1 m or less can be large (standard deviation during summer period of 1.58 and 1.28 μmol CO₂ m⁻² s⁻¹, respectively). At the smallest of scales, the individual contributions of the bulk soil, the roots, and the litter mat changed greatly throughout the season and between forest types, although the data were highly variable within any given site. For scales of 1-10 m, variation between individual measurements could be explained by positive relationships between forest floor mass, root mass, carbon and nitrogen pools, or root nitrogen concentration. Lastly, topography strongly influenced soil moisture and soil properties, and created spatial patterns of soil respiration which changed greatly during a drought event. Integrating soil fluxes over a 4 km² region using an elevation dependent soil respiration model resulted in a drought induced reduction of peak summer flux rates by 37.5%, versus a 31.3% when only plot level data was used. The trends at these important scales may help explain some inter-annual and spatial variability of the net ecosystem exchange of carbon.     

Seasonal transfers of assimilated 14C in grassland: Plant production and turnover,soil and plant respiration

Six areas of native grassland were labelled with ¹⁴C during a growing season. Transfers from the foliage to the roots and root respiration were measured. Plant production and turnover rates were determined by sampling the labelled material at different periods following exposure to ¹⁴CO₂.Above to beneath ground plant production ratios ranged between 1.1 and 1.9 with maximal translocation to the roots occurring during the drier summer months. The distribution of the photosynthates in the roots at different depths changed with time and soil moisture content. The upper part of the soil (0–10 cm) contained 49–77% of the labelled C found beneath the soil surface. Measurement of transfers with time of the above ground labelled C from living to dead plant and litter categories gave an insight into foliage dynamics and made it possible to estimate the seasonal shoot production at 130g Cm^?2 (1300kg ha^?1). Root growth represented 100g Cm^?2 (1000 kg ha^?1).Calculations of root and soil respiration were based on the CO₂ profiles in the soil. The fluxes of labelled and unlabelled CO₂ at the soil surface were estimated using the diffusion equation method. Respiration by roots and closely associated soil organisms accounted for 12 per cent of the net assimilation of CO₂ by the plants. This proportion was constant throughout the season and represented 19 per cent of the total CO₂ evolved at the soil surface.     

Carbon emission flux and storage in the degraded peatlands of the Zoige alpine area in the Qinghai–Tibetan Plateau

The Zoige alpine peatlands cover approximately 4,605 km² of the Qinghai–Tibetan Plateau and are considered to constitute the largest plateau peatland on the Eurasian continent. However, the Zoige alpine peatlands are undergoing major degradation because of human activities and climate change, which would cause uncertainty in the budget of greenhouse gases (CH₄ and CO₂) and carbon (C) storage in global peatlands. This study simultaneously investigates the CH₄ and CO₂ emission fluxes and C storage at three typical sites with respect to the peatland degradation gradient: peatland, wet meadow and dry meadow. Results show that peatland degradation would increase the CO₂ emission and decrease the CH₄ emission. Moreover, the average C emission fluxes were 66.05, 165.78 and 326.56 mg C m^?2 hr^?1 for the peatland, wet meadow and dry meadow, respectively. The C storage of the vegetation does not considerably differ among the three sampling sites. However, when compared with the peatland (1,088.17 t C ha^?1), the soil organic C storage decreases by 420 and 570 t C ha^?1 in case of wet and dry meadows, respectively. Although the C storage in the degraded peatlands decreases considerably, it can still represent a large capacity of C sink. Therefore, the degraded peatlands in the Zoige alpine area must be protected and restored to mitigate regional climate change.     

Seasonal Dynamics of Soil CO<Subscript>2</Subscript> Concentration and CO<Subscript>2</Subscript> Fluxes from the Soil of the Former Lake Texcoco,Mexico

Seasonal changes of the soil CO₂ concentration and the rate of CO₂ fluxes emission from the soil formed on the sediments of the former Lake Texcoco, which occupied a significant part of the Mexico Valley until the mid-17th century, were studied. The soils (Fluvic Endogleyic Phaeozems) were characterized by a low CO₂ fluxes rate, which is related to their high alkalinity. The mean values of soil respiration were 6.0–14.1 mg C/(m² h) depending on vegetation type, which corresponds to 60–157 g C/(m² yr). The contribution of plants to the CO₂ fluxes insignificantly varied by seasons and depended on the species composition of vegetation. The soil CO₂ concentration and soil respiration in eucalypt (Eucalyptus globulus Labill.) plantation were two times higher than those in the grass–subshrub area, the ground cover of which consisted of Distichlis spicata (L.) Greene and Suaeda nigra (Raf.) J.F. Macbr. species. This can be related to the significant volumes of gas production during the respiration of eucalypt roots and associated rhizosphere community. The contribution of the root systems of grass cover to the soil CO₂ fluxes in eucalypt plantation slightly varied within the year and was equal to 24% on the average. In the grass–subshrub area, its value varied from 41% in the cold season to 60% in the warm season. The spatial variability of soil CO₂ concentration and its flux rate to the atmosphere was due to the differences in plant species composition and hydrothermal conditions, and their temporal trend was closely related to the seasonal accumulation of plant biomass and soil temperature.     

Influence of water depth and soil amelioration on greenhouse gas emissions from peat soil columns

Recently, large areas of tropical peatland have been converted into agricultural fields. To be used for agricultural activities, peat soils need to be drained, limed and fertilized due to excess water, low nutrient content and high acidity. Water depth and amelioration have significant effects on greenhouse gas (GHG) production. Twenty-seven soil samples were collected from Jabiren, Central Kalimantan, Indonesia, in 2014 to examine the effect of water depth and amelioration on GHG emissions. Soil columns were formed in the peatland using polyvinyl chloride (PVC) pipe with a diameter of 21 cm and a length of 100 cm. The PVC pipe was inserted vertically into the soil to a depth of 100 cm and carefully pulled up with the soil inside after sealing the bottom. The treatments consisting of three static water depths (15, 35 and 55 cm from the soil surface) and three ameliorants (without ameliorant/control, biochar+compost and steel slag+compost) were arranged using a randomized block design with two factors and three replications. Fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from the soil columns were measured weekly. There was a linear relationship between water depth and CO₂ emissions. No significant difference was observed in the CH₄ emissions in response to water depth and amelioration. The ameliorations influenced the CO₂ and N₂O emissions from the peat soil. The application of biochar+compost enhanced the CO₂ and N₂O emissions but reduced the CH₄ emission. Moreover, the application of steel slag+compost increased the emissions of all three gases. The highest CO₂ and N₂O emissions occurred in response to the biochar+compost treatment followed by the steel slag-compost treatment and without ameliorant. Soil pH, redox potential (Eh) and temperature influenced the CO₂, CH₄ and N₂O fluxes. Experiments for monitoring water depth and amelioration should be developed using peat soil as well as peat soil–crop systems.     

大通煤矸石充填复垦区不同植被类型土壤碳排放动态

2011年7月至2012年3月,利用LI-8100土壤CO2通量系统测定了淮南市大通煤矸石充填复垦区草地、灌丛、小乔木林、大乔木林土壤呼吸强度及其相关影响因子.结果显示,煤矸石充填复垦区4种植被类型下土壤呼吸强度的昼夜及季节变化均呈单峰曲线形式,最大值出现在夏季的12:00-16:00间,最小值出现在冬季的4:00左右;不同植被类型下土壤呼吸强度差异显著(p＜0.05),且土壤呼吸强度有强到弱的顺序呈现:草地＞灌丛＞小乔木林＞大乔木林.4种植被土壤CO2-C年释放通量分别为(999.74±62.26) g/(m2· a),(908.49±72.41) g/(m2· a),(869.22±56.23) g/(m2· a),(726.10±63.01) g/(m2· a),故考虑植被的碳减排效应,在煤矸石充填复垦区可以多种植乔木、灌木,而尽量少植人工草坪;复垦区土壤呼吸除受植被类型影响外,主要受10 cm土层土壤温度的影响,各植被类型土壤呼吸强度对土壤温度的指数模型均可以解释88％以上的土壤呼吸变异;草地、灌丛、小乔木林、大乔木林碳排放对温度的敏感性Q10值分别为:2.57,2.71,2.96和3.67.     

Nitrous oxide emission derived from soil organic matter decomposition from tropical agricultural peat soil in central Kalimantan,Indonesia

Our previous research showed large amounts of nitrous oxide (N₂O) emission (>200?kg?N?ha^?1?year^?1) from agricultural peat soil. In this study, we investigated the factors influencing relatively large N₂O fluxes and the source of nitrogen (N) substrate for N₂O in a tropical peatland in central Kalimantan, Indonesia. Using a static chamber method, N₂O and carbon dioxide (CO₂) fluxes were measured in three conventionally cultivated croplands (conventional), an unplanted and unfertilized bare treatment (bare) in each cropland, and unfertilized grassland over a three-year period. Based on the difference in N₂O emission from two treatments, contribution of the N source for N₂O was calculated. Nitrous oxide concentrations at five depths (5–80?cm) were also measured for calculating net N₂O production in soil. Annual N fertilizer application rates in the croplands ranged from 472 to 1607?kg?N?ha^?1?year^?1. There were no significant differences in between N₂O fluxes in the two treatments at each site. Annual N₂O emission in conventional and bare treatments varied from 10.9 to 698 and 6.55 to 858?kg?N?ha^?1?year^?1, respectively. However, there was also no significant difference between annual N₂O emissions in the two treatments at each site. This suggests most of the emitted N₂O was derived from the decomposition of peat. There were significant positive correlations between N₂O and CO₂ fluxes in bare treatment in two croplands where N₂O flux was higher than at another cropland. Nitrous oxide concentration distribution in soil measured in the conventional treatment showed that N₂O was mainly produced in the surface soil down to 15?cm in the soil. The logarithmic value of the ratio of N₂O flux and nitrate concentration was positively correlated with water filled pore space (WEPS). These results suggest that large N₂O emission in agricultural tropical peatland was caused by denitrification with high decomposition of peat. In addition, N₂O was mainly produced by denitrification at high range of WFPS in surface soil.