The absolute requirement for carbon dioxide for aerobic methane oxidation by a methanotrophic-heterotrophic soil community of bacteria

An aerobic methanotrophic-heterotrophic soil community has been characterised when growing with different partial pressures of CO₂. The methanotrophic population using methane as carbon source reached 3 × 10⁷ cfu ml^–1 with one of the major methanotrophs being of type II which uses the serine pathway for C assimilation. Optimal methanotrophic activity required the addition of CO₂, and in the absence of CO₂ no methane oxidisers grew. Partial pressures of CO₂ from 1.6 to 11.6 kPa gave optimal cell growth and production of soluble organic compounds. Biomass yield, soluble organics and CO₂ production were 0.36, 0.15, and 0.48 mg mg^–1 methane uptake, respectively, with CO₂ at 11.6 kPa. The results presented here may have important implications for the use of methane-oxidising bacteria in bioremedial applications.     

松嫩盐碱草地植物种群的土壤营养位季节动态

针对松嫩盐碱草地的特点,综合评价了18项土壤因子,以植物的相对地上生物量为土壤营养位效能,分析了松嫩盐碱草地植物种群的土壤营养位季节动态。伴随季节的更替,碱蓬等强耐盐碱植物的土壤营养位中心点逐渐向土壤盐碱程度严重的一侧移动,土壤营养位体积也逐月增加,土壤营养位宽度的扩大是土壤营养位体积增加的主要原因。虎尾草(Chloris virgata)和羊草(Aneurolepidium chinense)的土壤营养位中心点数值和土壤营养位体积7月份时最大。7月份时虎尾草的土壤营养位效能峰值明显高于其它月份的,使得虎尾草此月份的土壤营养位体积在整个生长季内最大,而羊草7月份的土壤营养位宽度和土壤营养位效能峰值都较大,共同决定了该月份羊草的土壤营养位体积最大。除上述植物外,其他轻度耐盐碱植物的土壤营养位中心点随季节更替的变化趋势与碱蓬等强耐盐碱植物的刚好相反,是向土壤盐碱程度越轻的方向。其他轻度耐盐碱植物的土壤营养位宽度8月份时最小,但因为此时土壤营养位效能峰值明显高于其它月份的,它们8月份的土壤营养位体积仍是整个生长季内最大的。松嫩盐碱草地植物种群土壤营养位重叠也存在着明显的季节变化。     

新疆阜康绿洲不同生境土壤动物群落多样性及其季节动态

为了查明阜康绿洲不同生境土壤动物群落多样性特征及其变化动态,2010年4、7、9及11月中旬分别以该绿洲的用材林、防护林、苗圃、耕地、盐碱地、灌木林及荒草地生境为研究对象,采用手捡法、改良干漏斗法和湿漏斗法分离0～20 cm土层中的土壤动物,并分析了不同生境土壤动物的群落结构、分布特征及季节动态.共获得土壤动物1 1098只,共35类,其中线虫类、轮虫类和弹尾类为优势类群.在7种不同生境土壤动物类群、个体数和多样性以及不同季节之间均存在显著差异(P＜0.05),其中Shannon多样性指数依次为用材林＞防护林＞灌木林＞耕地＞盐碱地＞苗圃＞荒草地;时空分布调查发现,不同生境土壤动物群落分布具有明显的表聚性特征,并在不同土层及季节间均有显著性差异(P＜0.05),季节动态变化依次为秋季最多、其次春季和冬季,夏季最少;不同生境土壤动物群落间的Jaccard相似性指数属于中等不相似(处于0.25～0.50).不同生境组间聚类和排序结果表明,将7种不同生境分为人工林生境型、人为干扰生境型、灌木生境型及荒漠生境型4大类型.结果表明,阜康绿洲不同生境土壤动物群落组成和多样性具有明显的生境和季节差异特征.     

天台山七子花群落下土壤微生物生物量的季节动态

研究天台山七子花群落下土壤微生物生物量的季节变化规律及生态特性。根据实测数据分别对根际、根围微生物生物量碳、氮与土壤环境因子之间进行相关性分析,并建立了土壤微生物指标与环境因素之间的回归方程,以此为基础对天台山七子花群落下土壤微生物生物量的季节变化进行预测。回归分析表明：土壤温度、水分对微生物生物量的影响大于土壤pH值对微生物生物量的影响,而且土壤温度、水分对微生物生物量氮的影响大于对微生物生物量碳的影响。土壤温度对微生物生物量碳、氮的影响最大。     

Phytoplankton of Lake Peipsi-Pihkva: species composition, biomass and seasonal dynamics

With 33 years of phytoplankton quantitative studies carried out, a series of qualitative data with a length of over 80 years is at our disposal. About 500 algal species have been found in plankton by different researchers. In different seasons and years 35 main species (dominants and subdominants) form 68–96 % of biomass in L. Pihkva (southern, more eutrophic part) and 60–97 % in L. Peipsi (northern, less eutrophic part). L. Lämmijärv, connecting the two parts is similar to L. Pihkva in respect to phytoplankton and the trophic state. Diatoms and blue-green algae prevail in biomass, diatoms and green algae, in the species number. The oligo-mesotrophic Aulacoseira islandica (O. Müller) Sim. is characteristic of the cool period; A. granulata (Ehr.) Sim. and Stephanodiscus binderanus (Kütz.) Krieger prevail in summer and autumn, the latter being most abundant in the southern part. Gloeotrichia echinulata (J.S. Smith) P Richter and Aphanizomenon flos-aquae (L.) Ralfs dominate in summer causing water-bloom. Phytoplankton has mostly three maxima in seasonal dynamics in L. Peipsi and two in L. Pihkva. Its average biomass in spring in different years has fluctuated in the range 5.6–16 and 6–12.7 g m^–3, in summer 3.1–14.8 and 5.6–125 (10–20 in most cases); and in autumn 7–16.3 and 5.2–26 in the northern and southern parts, respectively.The dominant complex has not changed considerably since 1909; however, the distribution of dominant species in lake parts has become more even in the last decades. Periods of high biomass occurred in the first half of the 1960s and 1970s and in 1988–1994, of low biomass in 1981–1987. The first coincided, in general, with periods of low water level and high water temperature.     

Species composition,distribution and seasonal dynamics of Rotifera in a Rift Valley lake in Ethiopia (Lake Awasa)

The species composition of rotifers in Lake Awasa was studied and 40 species recorded. Seven species appeared in large numbers in the plankton seasonally. Brachionus and Keratella species made up more than 50% of the rotifer community by numbers during the observation period (1983–1987). The standing stock numbers of rotifer species are low with a maximum of 50 individuals L^–1, and some possible reasons for this observation are discussed. Most rotifer species are distributed randomly in the lake and show 3-fold fluctuations between consecutive days.The seasonal dynamics of most rotifer species are correlated with mixing periods in the lake, and the amplitude of seasonal fluctuation may be as high as 50-fold. Clear-cut seasonal succession of rotifer species was observed during the study period, but no consistent seasonal pattern for individual species was obvious. Also, observations indicate that rotifer biomass is partly sustained by availability of carbon through the bacterial pathway and that competitive exclusion for food by nauplii and ciliates probably keeps rotifer abundance low.     

腾格里沙漠东南缘不同生物土壤结皮细菌多样性及其季节动态特征

微生物多样性对于生物土壤结皮在沙漠生态系统中改善局部环境以及提升生态功能具有重要作用。本研究对腾格里沙漠东南缘沙坡头地区藻结皮、藓结皮及其下层的四季样品进行了16S rDNA高通量测序, 以期阐明细菌多样性及其在生物土壤结皮演替过程中的季节变化规律。结果表明4种类型样品的细菌丰富度在夏季显著低于其他3个季节。4种类型样品中主要的细菌类群为变形菌门、放线菌门、绿弯菌门、酸杆菌门、蓝细菌门等, 其中变形菌门和放线菌门为优势类群, 夏季时变形菌门的相对多度显著高于春季、秋季、冬季, 且在结皮层中相对多度显著高于结皮下层。放线菌门的相对多度在春季、夏季显著高于秋季、冬季, 且结皮下层相对多度高于结皮层。生物土壤结皮演替过程中细菌多样性及其相对多度季节动态变化表明其对沙漠土壤局部环境的变化作出了响应, 这为深入理解生物土壤结皮在沙漠生态系统中的生态功能提供了微生物多样性数据。     

Changing land use reduces soil CH4 uptake by altering biomass and activity but not composition of high-affinity methanotrophs

Forest ecosystems assimilate more CO₂ from the atmosphere and store more carbon in woody biomass than most nonforest ecosystems, indicating strong potential for afforestation to serve as a carbon management tool. However, converting grasslands to forests could affect ecosystem–atmosphere exchanges of other greenhouse gases, such as nitrous oxide and methane (CH₄), effects that are rarely considered. Here, we show that afforestation on a well-aerated grassland in Siberia reduces soil CH₄ uptake by a factor of 3 after 35 years of tree growth. The decline in CH₄ oxidation was observed both in the field and in laboratory incubation studies under controlled environmental conditions, suggesting that not only physical but also biological factors are responsible for the observed effect. Using incubation experiments with ¹³CH₄ and tracking ¹³C incorporation into bacterial phospholipid fatty acid (PLFA), we found that, at low CH₄ concentrations, most of the ¹³C was incorporated into only two PLFAs, 18 : 1ω7 and 16 : 0. High CH₄ concentration increased total ¹³C incorporation and the number of PLFA peaks that became labeled, suggesting that the microbial assemblage oxidizing CH₄ shifts with ambient CH₄ concentration. Forests and grasslands exhibited similar labeling profiles for the high-affinity methanotrophs, suggesting that largely the same general groups of methanotrophs were active in both ecosystems. Both PLFA concentration and labeling patterns indicate a threefold decline in the biomass of active methanotrophs due to afforestation, but little change in the methanotroph community. Because the grassland consumed CH₄ at a rate five times higher than forest soils under laboratory conditions, we concluded that not only biomass but also cell-specific activity was higher in grassland than in afforested plots. While the decline in biomass of active methanotrophs can be explained by site preparation (plowing), inorganic N (especially NH₄⁺) could be responsible for the change in cell-specific activity. Overall, the negative effect of afforestation of upland grassland on soil CH₄ uptake can be largely explained by the reduction in biomass and to a lesser extent by reduced cell-specific activity of CH₄-oxidizing bacteria.     

Links between methanotroph community composition and CH4 oxidation in a pine forest soil

The main gap in our knowledge about what determines the rate of CH₄ oxidation in forest soils is the biology of the microorganisms involved, the identity of which remains unclear. In this study, we used stable-isotope probing (SIP) following ¹³CH₄ incorporation into phospholipid fatty acids (PLFAs) and DNA/RNA, and sequencing of methane mono-oxygenase ( pmoA ) genes, to identify the influence of variation in community composition on CH₄ oxidation rates. The rates of ¹³C incorporation into PLFAs differed between horizons, with low ¹³C incorporation in the organic soil and relatively high ¹³C incorporation into the two mineral horizons. The microbial community composition of the methanotrophs incorporating the ¹³C label also differed between horizons, and statistical analyses suggested that the methanotroph community composition was a major cause of variation in CH₄ oxidation rates. Both PLFA and pmoA -based data indicated that CH₄ oxidizers in this soil belong to the uncultivated 'upland soil cluster α'. CH₄ oxidation potential exhibited the opposite pattern to ¹³C incorporation, suggesting that CH₄ oxidation potential assays may correlate poorly with in situ oxidation rates. The DNA/RNA-SIP assay was not successful, most likely due to insufficient ¹³C-incorporation into DNA/RNA. The limitations of the technique are briefly discussed.     

川西亚高山草甸土壤呼吸的昼夜变化及其季节动态

采用LI-8100A土壤碳通量自动测量系统,于2011年4—11月对川西亚高山草甸的土壤呼吸进行了测定,分析了水热因子对草甸昼、夜间土壤呼吸特征及其季节动态变化的影响。结果表明:1)川西亚高山草甸昼、夜间土壤呼吸的变化格局不同,昼间呈双峰型,夜间呈抛物线型;整个观测期(4—11月)内,夜间土壤呼吸占总土壤呼吸的46.79%,其中草盛期(6—9月)的昼、夜土壤呼吸占有较大比例。2)8次夜间土壤呼吸测定的变化趋势基本相同,最低值均在06:30—07:00左右;昼、夜间土壤呼吸季节变化的主要影响因素为土壤5 cm温度,Van’t Hoff指数模型和Lloyd和Taylor方程均适合预测整个的土壤呼吸通量。3)返青期(4—5月)和枯黄期(10—11月)的昼、夜间土壤呼吸差异不显著,均低于草盛期;整个观测期,草甸昼、夜间土壤呼吸与土壤温度均有显著的指数相关,而与土壤水分含量存在显著线性相关则表现在草返青期夜间及枯黄期昼、夜间。4)整个观测期昼、夜间的Q10值分别为3.90和3.74;对Q10值的分析表明,返青期昼土壤呼吸的Q10值最大(4.14),草盛期夜间的Q10值最小(1.40)。研究结果说明,采用昼、夜间土壤呼吸的瞬时值来推算土壤呼吸的季节通量和年通量时,不仅需要加大观测期间夜间土壤呼吸的测定,还需要考虑昼、夜间土壤温度和土壤含水量及其它生物因子的影响。     

Biphasic kinetics of a methanotrophic community is a combination of growth and increased activity per cell

Because methane-oxidizing bacteria (MOB) are the only biological sink for the greenhouse gas methane, knowledge of the functioning of these bacteria in various ecosystems is needed to understand the dynamics observed in global methane emission. The activity of MOB is commonly assessed by methane oxidation assays. The resulting methane depletion curves often follow a biphasic pattern of initial and induced methane oxidation activity, often interpreted as representing the in situ active and total MOB community, respectively. The application of quantitative-PCR on soil incubations, which were stopped before, at and after the transition point in the methane-depletion curve, demonstrated that both pmoA -mRNA was produced as well as substantial cell growth took place already in the initial phase. In addition, type Ia and II MOB displayed markedly different behaviour, which can be interpreted as ecologically different strategies. For the correct interpretation of methane oxidation assays, the use of small time windows is recommended to calculate methane oxidation activities to avoid substantial cell growth.     

青藏高原东缘高山森林-苔原交错带土壤微生物生物量碳、氮和可培养微生物数量的季节动态

为了了解青藏高原东缘高山森林-苔原交错带土壤微生物的特征和季节变化, 研究了米亚罗鹧鸪山原始针叶林、林线、树线、密灌丛、疏灌丛和高山草甸土壤微生物生物量碳(MBC)、氮(MBN)和可培养微生物数量的季节动态。结果表明, 植被类型和季节动态对MBC、MBN和微生物数量都有显著影响。不同时期的微生物在各植被类型间分布有差异, 植物生长季初期和生长季中期, 树线以上群落的MBC高于树线下的群落, 而到生长季末期恰恰相反, 暗针叶林、林线和树线的MBC显著升高, 各植被之间MBC的差异减小; 微生物数量基本上也是以树线为界, 树线以下群落土壤微生物数量显著低于树线以上群落, 其中密灌丛的细菌数量最高; 可培养微生物数量为生长季末期>生长季初期>生长季中期。生长季末期真菌数量显著增加, 且MBC/MBN最高。统计分析表明, MBN与细菌、真菌、放线菌数量存在显著的相关关系, 而MBC仅与真菌数量存在显著相关关系( p < 0.05)。植物生长季末期大量的凋落物输入和雪被覆盖可能是微生物季节变异的外在因素, 而土壤微生物和高山植物对有效氮的竞争可能是微生物季节变异的内在因素。植物生长季初期对氮的吸收和土壤微生物在植物生长季末期对氮的固定加强了高山生态系统对氮的利用。气候变暖可能会延长高山植物的生长季, 增加高山土壤微生物生物量, 加速土壤有机质的分解, 进而改变高山土壤碳的固存速率。     

Biochemical and molecular characterization of methanotrophs in soil from a pristine New Zealand beech forest

Methane (CH4) oxidation and the methanotrophic community structure of a pristine New Zealand beech forest were investigated using biochemical and molecular methods. Phospholipid-fatty acid-stable-isotope probing (PLFA-SIP) was used to identify the active population of methanotrophs in soil beneath the forest floor, while terminal-restriction fragment length polymorphism (T-RFLP) and cloning and sequencing of the pmoA gene were used to characterize the methanotrophic community. PLFA-SIP suggested that type II methanotrophs were the predominant active group. T-RFLP and cloning and sequencing of the pmoA genes revealed that the methanotrophic community was diverse, and a slightly higher number of type II methanotrophs were detected in the clone library. Most of the clones from type II methanotrophs were related to uncultured pmoA genes obtained directly from environmental samples, while clones from type I were distantly related to Methylococcus capsulatus. A combined data analysis suggested that the type II methanotrophs may be mainly responsible for atmospheric CH4 consumption. Further sequence analysis suggested that most of the methanotrophs detected shared their phylogeny with methanotrophs reported from soils in the Northern Hemisphere. However, some of the pmoA sequences obtained from this forest had comparatively low similarity (<97%) to known sequences available in public databases, suggesting that they may belong to novel groups of methanotrophic bacteria. Different methods of methanotrophic community analysis were also compared, and it is suggested that a combination of molecular methods with PLFA-SIP can address several shortcomings of stable isotope probing.     

Species composition and seasonal dynamics of water mites (Hydracarina) in a mountain stream (Steina,Black Forest,southern Germany)

The species composition and seasonal dynamics of water mites were studied in a small softwater stream in southern Germany from October 1986 to November 1988. On average water mites contributed 5.5% by abundance and 1.8% by biomass to the total invertebrate community. Annual densities and biomasses averaged 623–1057 (mean 905) individuals M^–2 and 45.9–75.6 mg (mean 64.0) dry mass m^–2, respectively. 41 species were identified, Torrenticola elliptica (Torrenticolidae) being the most abundant. Nearly every taxon showed a distinct and consistent seasonality, with maximum abundance and biomass in summer and minimum values in winter. Both abundance and biomass of water mites were significantly correlated with water temperature (p < 0.001).     

若尔盖退化高寒湿地土壤理化性质、酶活性及微生物群落的季节动态

以若尔盖退化高寒湿地为研究对象,连续3年(2015—2017年)于植被返青期(4—5月)、草盛期(7—8月)和枯黄期(10—11月)监测高原鼢鼠鼠丘密度、3个土层(0—10、10—20、20—30 cm)土壤理化性质、酶活性及微生物数量的季节动态,并分析土壤生物学特征与土壤环境间的季节相关性。结果表明:(1)各植被物候期,土壤pH值、容重指标均随土层加深而显著升高(P<0.05),土壤含水量、有机质、全氮、碱解氮、有效磷、速效钾、酶活性及微生物数量指标均随土层加深而显著降低(P<0.05);(2)植被物候期对高寒鼠荒地非土丘土壤养分在不同土层的垂直分配有显著影响,对0—10 cm土层土壤生物学特征含量的影响程度显著大于10—20 cm和20—30 cm土层。(3)冗余分析(RDA)表明3个植被物候期,土壤生物学特征指标与土壤理化性质指标间显著相关(P<0.05),主成分分析(PCA)表明各指标在不同土层均呈现明显的季节性分布,数量特征表现为:枯黄期>返青期>草盛期。揭示了高寒鼠荒地高原鼢鼠季节性活动对土壤理化性质、酶活性及微生物数量的影响,为今后青藏高原鼠...     

施肥对落叶松和水曲柳人工林土壤微生物生物量碳和氮季节变化的影响

2007-2008年,采用氯仿熏蒸浸提法测定了落叶松和水曲柳人工林土壤微生物生物量,研究施N肥对土壤微生物生物量碳、氮,以及细菌、真菌和放线菌数量季节变化的影响.结果表明：落叶松林地土壤微生物生物量碳、氮两年平均值分别比水曲柳林地低13.8%和18.3%,但两种林分土壤微生物生物量碳、氮具有相同的季节变化规律：5月最低,9月最高;表层（0～10 cm）土壤微生物生物量碳、氮及微生物数量均高于亚表层（10～20 cm）土壤.但细菌、真菌和放线菌数量的季节变化格局与生物量不同.施肥降低了两种林分的微生物生物量碳、氮,以及细菌、真菌和放线菌数量,其中,落叶松林地微生物生物量碳和氮分别降低了24%和63%,水曲柳分别降低了51%和68%.说明施N肥限制了土壤微生物生物量,改变了土壤微生物的群落结构.     

不同龄级速生杨人工林土壤微生物数量与养分动态变化

通过稀释平板法和常规化学分析法, 对伊犁河谷地区3种龄级(5年、10年、15年)的速生杨欧美黑杨(Populus × euramericana)人工林的土壤微生物数量、组成和土壤养分变化进行了研究。结果表明, 3种不同林龄林地土壤微生物集中分布在10-40 cm土层, 数量和种类组成随季节变化有明显差异。随着林龄的增长, 土壤微生物总数、细菌数量减少, 真菌和放线菌数量在10年生人工林最高, 这一规律随季节变化。三大类土壤微生物的组成比例相对稳定, 不随季节变化而变化。土壤有机碳、氮含量主要集中在0-20 cm土层, 随土壤深度的增加逐渐减少, 其含量及分布受季节和土壤深度不同程度的影响。土壤有机碳含量随林龄的增长而逐渐增高, 有机氮则先减后增。相关分析表明, 土壤微生物总数与土壤有机碳呈负相关, 真菌数量与土壤有机氮呈正相关。3种林地土壤有机C/N比与土壤细菌数量/真菌数量比例一致, 说明速生杨人工林在一定生长年龄内能提高土壤的固碳能力, 改善土壤肥力。     

Effects of soil moisture content and temperature on methane uptake by grasslands on sandy soils

Aerobic grasslands may consume significant amounts of atmospheric methane (CH4). We aimed (i) to assess the spatial and temporal variability of net CH4 fluxes from grasslands on aerobic sandy soils, and (ii) to explain the variability in net CH4 fluxes by differences in soil moisture content and temperature. Net CH4 fluxes were measured with vented closed flux chambers at two sites with low N input on sandy soils in the Netherlands: (i) Wolfheze, a heather grassland, and (ii) Bovenbuurtse Weilanden, a grassland which is mown twice a year. Spatial variability of net CH4 fluxes was analysed using geostatistics. In incubation experiments, the effects of soil moisture content and temperature on CH4 uptake capacity were assessed. Temporal variability of net CH4 fluxes at Wolfheze was related to differences in soil temperature (r2 of 0.57) and soil moisture content (r2 of 0.73). Atmospheric CH4 uptake was highest at high soil temperatures and intermediate soil moisture contents. Spatial variability of net CH4 fluxes was high, both at Wolfheze and at Bovenbuurtse Weilanden. Incubation experiments showed that, at soil moisture contents lower than 5% (w/w), CH4 uptake was completely inhibited, probably due to physiological water stress of methanotrophs. At soil moisture contents higher than 50% (w/w), CH4 uptake was greatly reduced, probably due to the slow down of diffusive CH4 and O2 transport in the soil, which may have resulted in reduced CH4 oxidation and possibly some CH4 production. Optimum soil moisture contents for CH4 uptake were in the range of 20 – 35% (w/w), as prevailing in the field. The sensitivity of CH4 uptake to soil moisture content may result in short-term variability of net atmospheric CH4 uptake in response to precipitation and evapotranspiration, as well as in long-term variability due to changing precipitation patterns as a result of climate change.     

Influence of atmospheric CO2 enrichment on methane consumption in a temperate forest soil

Rates of atmospheric CH₄ consumption of soils in temperate forest were compared in plots continuously enriched with CO₂ at 200 µL L^?1 above ambient and in control plots exposed to the ambient atmosphere of 360 µL CO₂ L^?1. The purpose was to determine if ecosystem atmospheric CO₂ enrichment would alter soil microbial CH₄ consumption at the forest floor and if the effect of CO₂ would change with time or with environmental conditions. Reduced CH₄ consumption was observed in CO₂‐enriched plots relative to control plots on 46 out of 48 sampling dates, such that CO₂‐enriched plots showed annual reductions in CH₄ consumption of 16% in 1998 and 30% in 1999. No significant differences were observed in soil moisture, temperature, pH, inorganic‐N or rates of N‐mineralization between CO₂‐enriched and control plots, indicating that differences in CH₄ consumption between treatments were likely the result of changes in the composition or size of the CH₄‐oxidizing microbial community. A repeated measures analysis of variance that included soil moisture, soil temperature (from 0 to 30 cm), and time as covariates indicated that the reduction of CH₄ consumption under elevated CO₂ was enhanced at higher soil temperatures. Additionally, the effect of elevated CO₂ on CH₄ consumption increased with time during the two‐year study. Overall, these data suggest that rising atmospheric CO₂ will reduce atmospheric CH₄ consumption in temperate forests and that the effect will be greater in warmer climates. A 30% reduction in atmospheric CH₄ consumption by temperate forest soils in response to rising atmospheric CO₂ will result in a 10% reduction in the sink strength of temperate forest soils in the atmospheric CH₄ budget and a positive feedback to the greenhouse effect.