若尔盖高原湿地不同微地貌区甲烷排放通量特征

若尔盖高原是我国泥炭沼泽湿地的主要分布区、青藏高原的主要甲烷(CH₄)排放中心。为了研究湿地微地貌环境对高原湿地CH₄排放通量的影响, 2014年5-10月, 采用静态箱和快速温室气体分析仪原位测量若尔盖高原湖滨湿地3种泥炭沼泽5种微地貌环境下的CH₄排放通量特征。结果表明: (1)常年性淹水泥炭湿地洼地(P-hollow)和草丘(P-hummock)生长季平均CH₄排放通量为68.48和40.32 mg·m^-2·h^-1, 季节性淹水的泥炭湿地洼地(S-hollow)和草丘(S-hummock)平均CH₄排放通量为2.38和0.63 mg·m^-2·h^-1, 而无淹水平坦地(Lawn)平均CH₄排放通量为3.68 mg·m^-2·h^-1; (2)湿地5种微地貌区CH₄排放通量为(23.10 ± 30.28) mg·m^-2·h^-1 (平均值±标准偏差)), 变异系数为131%。分析显示这5种微地貌区CH₄排放通量的平均值与其水位深度平均值存在显著的线性正相关关系(R² = 0.919, p < 0.01), 表明水位深度是控制湿地微地貌区CH₄排放通量空间变化的主要因子; (3) P-hummock、P-hollow和S-hummock的CH₄排放通量存在显著的季节变化, Lawn和S-hollow无明显的季节性变化, 但5种微地貌区在夏季或秋季均观测到CH₄排放通量峰值, 其影响因子可能与水位深度、土壤温度和凋落物输入密切相关; (4) P-hollow可能时常发生冒泡式CH₄排放, 这可能导致过去低估了若尔盖高原湿地的CH₄排放量。     

Effluxes of nitrous oxide,methane and carbon dioxide and their responses to increasing nitrogen deposition in the Gurbantünggüt Desert of Xinjiang,China

Aims Desert soils play an important role in the exchange of major greenhouse gas (GHG) between atmosphere and soil. However, many uncertainties existed in understanding of desert soil role, especially in efflux evaluation under a changing environment. Methods We conducted plot-based field study in center of the Gurbantünggüt Desert, Xinjiang, and applied six rates of simulated nitrogen (N) deposition on the plots, i.e. 0 (N0), 0.5 (N0.5), 1.0 (N1), 3.0 (N3), 6.0 (N6) and 24.0 (N24) g·m^-2·a^-1. The exchange rates of N₂O, CH₄ and CO₂ during two growing seasons were measured for two years after N applications. Important findings The average efflux of two growing seasons from control plots (N0) were 4.8 μg·m^-2·h^-1, -30.5 μg·m^-2·h^-1 and 46.7 mg·m^-2·h^-1 for N₂O, CH₄ and CO_2, respectively. The effluxes varied significantly among seasons. N0, N0.5 and N1 showed similar exchange of N₂O in spring and summer, which was relatively higher than in autumn, while the rates of N₂O in N6 and N24 were controled by time points of N applications. The uptake of CH₄ was relatively higher in both spring and summer, and lower in autumn. Emission of CO₂ changed minor from spring to summer, and greatly decreased in autumn in the first measured year. In the second year, the emission patterns were changed by rates of N added. N additions generally stimulated the emission of N₂O, while the effects varied in different seasons and years. In addition, no obvious trends were found in the emission factor of N₂O. The uptake of CH₄ was not significantly affected by N additions. N additions did not change CO₂ emissions in the first year, while high N significantly reduced the CO₂ emissions in spring and summer of the second year, without affected in autumn. Structure equation model analysis on the factors suggested that N₂O, CH₄ and CO₂ were dominantly affected by the N application rates, soil temperature or moisture and plant density, respectively. Over the growing seasons, both the net efflux and the global warming potential caused by N additions were small.     

放牧对若尔盖高原湿地CH4排放的影响

湿地是大气甲烷(CH_4)的主要排放源,而有关放牧对湿地CH_4排放的影响特征仍未得到足够的报道。因此,通过静态箱法,研究了放牧对四川省若尔盖高原湿地CH_4排放的影响,CH_4气体通过快速温室气体分析仪测量。结果表明:放牧样地和围栏内样地生长季CH_4排放量为(31.32±19.57)g/m~2和(30.31±23.46)g/m~2,它们之间无差异显著;但是集中放牧期间(7—9月),放牧样地(21.01±12.35)g/m~2较围栏内样地显著增加了CH_4排放量为54.3%。2014年生长季期间通过刈割植物模拟放牧表明两种刈割强度CH_4排放量为(5.01±5.37)g/m~2和(4.69±5.99)g/m~2,较未刈割样地(1.15±1.89)g/m~2增加了335.9%和308.0%,其原因可能是放牧或者刈割减少地表植物生物量,降低植物高度,缩短了CH_4排放的路径距离。该结果可为我国高原湿地保护与管理决策提供基础数据支撑。     

Responses of soil respiration to reduced water table and nitrogen addition in an alpine wetland on the Qinghai-Xizang Plateau

近20年来, 青藏高原高寒湿地经历了明显的气候变化, 从而导致多数湿地水位下降和氮沉降的增加。对于湿地生态系统来说, 水位下降意味着土壤通气性能的改善, 可能会导致土壤呼吸的增加; 而氮沉降的增加可能会降低土壤微生物生物量和pH值, 从而可能抑制土壤呼吸。为此, 在青海海北高寒草地生态系统国家野外科学观测研究站利用中宇宙(Mesocosm)实验方法, 探讨了青藏高原高寒泥炭型湿地土壤呼吸对水位降低和氮添加的响应。结果表明: (1)水位降低显著增强了土壤呼吸, 而氮添加对土壤呼吸的影响依赖于水位的变化: 对照水位下, 氮添加显著抑制土壤呼吸; 而水位降低时, 氮添加对土壤呼吸速率无显著影响。(2)土壤呼吸速率与地上生物量、枯落物累积量之间呈显著正相关关系, 而与根系生物量无显著相关关系。(3)水位降低显著提高了土壤呼吸的温度敏感性, 而氮添加对其无显著的影响。因此预测: 随着氮沉降的升高, 高寒泥炭湿地土壤CO₂的排放量将会减少; 然而随着暖干化背景下水位的降低, 青藏高原高寒湿地会排放更多的CO₂。     

辽河口滨海湿地CH4排放特征及其影响因素

采用静态箱-气相色谱法,于2016年6—11月连续观测辽河口芦苇湿地、翅碱蓬湿地和裸滩湿地的CH_4排放速率,同时测定温度、氧化还原电位(Eh)、pH值和电导率(EC)等相关环境因子的动态变化。结果表明,3种类型湿地的CH_4排放具有明显的季节变化特征,均呈先上升后下降趋势。芦苇湿地、翅碱蓬湿地(涨潮前)和裸滩湿地(涨潮前)CH_4排放通量变化范围分别为0.447—10.40、0.045—0.509 mg m~(-2) h~(-1)和0.016—0.593 mg m~(-2) h~(-1),观测期内排放通量均值相应为(3.699±3.679)、(0.165±0.156) mg m~(-2) h~(-1)和(0.198±0.191) mg m~(-2) h~(-1),不同类型湿地之间差异显著(P0.01),芦苇湿地裸滩湿地(涨潮前)翅碱蓬湿地(涨潮前)。涨潮过程中,翅碱蓬湿地和裸滩湿地的排放速率分别变化在0.009—0.353 mg m~(-2) h~(-1)和0.018—0.335 mg m~(-2) h~(-1),观测期间其排放速率均值分别为(0.119±0.132) mg m~(-2) h~(-1)和(0.131±0.103) mg m~(-2) h~(-1),明显低于涨潮前(P0.01)。不同湿地类型间CH_4排放通量与电导率(EC)呈显著负相关(P0.01)。研究结果表明,潮汐和电导率均为影响辽河口不同类型湿地中CH_4排放的关键因子。     

湿地稻-鸭复合系统的CH_4排放规律

采用小区试验。大田试验研究湿地稻—鸭复合生态系统甲烷排放规律。稻鸭复合生态系统中甲烷排放随季节变化。在早稻—晚稻耕作制度条件下,6月上旬和7月底分别有2个高峰。早稻与晚稻的排放规律也各异。早稻甲烷排放峰值出现在水稻幼穗分化期。最高值为13．693mg／(m^2．h)．晚稻峰值出现在分蘖盛期。可达23．145—105．595mg／(m^2．h)。养鸭处理与常规栽培甲烷排放差异达极显著水平。稻田养鸭的早稻生育期间甲烷排放总量为5．517g／m^2。传统栽培为9．89g/m^2。稻田养鸭的晚稻生育期间排放总量为10．113g／m^2。传统栽培为17．054g／m^2。稻田养鸭与传统栽培比较．土壤氧化还原电位增加15．3mV．还原物质总量、活性还原物质总量、活性有机还原物质总量分别降低0．365cmo1／kg、0．242cmo1／kg和0．180cmo1／kg。土壤氧化还原特性影响甲烷排放通量．土壤还原物质总量、活性还原物质及活性有机还原物质数量与甲烷排放通量的相关系数分别为0．805、0．791、0．769。湿地稻鸭复合生态系统土壤氧化还原状况改善是甲烷排放减少原因之一。     

青藏高原高寒湿地生态系统CO2通量

依据涡度相关系统连续观测的2005年CO2通量数据,对青藏高原东北隅的高寒湿地生态系统源/汇功能及其部分环境影响因素进行了分析.结果表明,高寒湿地生态系统为明显的碳源,在植物生长季(5～9月份)吸收230.16 gCO2·m-2,非生长季(1～4月份及10～12月份)释放546.18 gCO2·m-2,其中净排放最高在5月份,为181.49 gCO2·m-2,净吸收最高在8月份,为189.69 gCO2·m-2,年释放量为316.02 gCO2·m-2.在平均日变化中,最大吸收值出现在7月份12:00,为(0.45±0.0012) mgCO2·m-2·s-1,最大排放速率出现在8月份0:00,为(0.22±0.0090) mgCO2·m-2·s-1.生长季中6～9月份表现为明显的单峰型日变化,非生长季的变化幅度较小.净生态系统交换量(NEE)和生态系统总初级生产力(GPP)与气温、空气水气饱和亏和地表反射率等环境因素呈现相似的相关性,与地上生物量和群落叶面积指数则为线性负相关,生态系统呼吸(Res)则与上述因子的相关性呈现相反的趋势.     

Characteristics of nutrients in two dominant plant species and rhizospheric soils in alpine desert of the Qinghai-Xizang Plateau under contrasting climates

为了探究青藏高原寒冷沙地上优势植物及其根际土壤的养分对不同气候的响应过程, 选取半干旱和半湿润沙地上的优势植物中国沙棘(Hippophae rhamnoides subsp. sinensis)和沙蒿(Artemisia desertorum)为对象, 调查自然条件下青藏高原半干旱和半湿润沙地上两种植物枝叶和根的碳、氮、磷含量, 及其根际0-10 cm和10-20 cm土壤的有机碳、全氮、全磷、铵态氮、硝态氮、有效磷含量, 并探讨两种优势植物和根际土壤的养分含量的关系及其影响因子。结果表明, 半干旱和半湿润条件下中国沙棘和沙蒿及其根际土壤的养分差异明显。半干旱和半湿润气候条件下两种植物碳、氮、磷的积累差异显著。半湿润条件下, 沙蒿根际土壤中的有机碳、全氮、铵态氮、硝态氮、有效磷的含量高于半干旱条件, 而中国沙棘根际土壤养分的结果却相反。不同气候条件下, 沙蒿和沙棘的养分和根际土壤的养分显著相关, 两种植物的养分比差异显著, 沙蒿氮磷比与其根际土壤的氮磷比以及中国沙棘的碳氮比与其根际土壤的碳氮比显著负相关。     

若尔盖退化泥炭地土壤原核微生物群落结构对水位恢复的短期响应

退化泥炭地的恢复是目前受关注的重要环境问题。若尔盖退化泥炭地原核微生物群落结构对水位恢复的早期响应可以为其生态恢复提供理论依据。为探究原核微生物群落结构对水位恢复的短期响应, 该研究以若尔盖退化泥炭地为研究对象, 设置水位恢复(10和30 cm)和对照组(-10 cm), 进行了1年野外原位水位恢复试验。采集0-15 cm土壤样品, 测定土壤有机碳(SOC)、总氮(TN)、总磷(TP)含量和pH等化学性质, 采用16S rRNA基因高通量测序技术分析微生物群落结构。结果表明: 水位恢复一定程度上能提高SOC、TN、TP含量及其化学计量比, 但与对照组差异不显著。主要优势微生物在门水平为酸杆菌(Acidobacteria)、变形菌(Proteobacteria)和疣微菌(Verrucomicrobia)。短期水位恢复(10和30 cm)对土壤原核微生物的α多样性没有显著影响, 而只是显著降低疣微菌和Spartobacteria的相对丰度, 增加了产甲烷菌种类。疣微菌和Spartobacteria相对丰度与水位和土壤pH呈显著负相关关系。退化泥炭地水位恢复过程中原核微生物群落结构对C:P、N:P和SOC含量响应较为敏感。综上, 短期水位恢复没有改变原核微生物α多样性, 而主要降低了疣微菌和Spartobacteria的相对丰度, 增加了产甲烷菌种类, 这将可能导致甲烷产生途径发生变化。土壤C:P、N:P和SOC含量控制了退化泥炭地随短期水位恢复过程中原核微生物群落结构变异。该研究在一定程度上丰富了原核微生物群落结构对短期水位响应的认识。     

青藏高原高寒湿地生态系统CO2通量

依据涡度相关系统连续观测的2005年CO₂通量数据,对青藏高原东北隅的高寒湿地生态系统源/汇功能及其部分环境影响因素进行了分析。结果表明,高寒湿地生态系统为明显的碳源,在植物生长季（5~9月份）吸收230.16 gCO₂•m^-2,非生长季（1~4月份及10~12月份）释放546.18 gCO₂•m^-2,其中净排放最高在5月份,为181.49 gCO₂•m^-2,净吸收最高在8月份,为189.69 gCO₂•m^-2,年释放量为316.02 gCO₂•m^-2。在平均日变化中,最大吸收值出现在7月份12:00,为（0.45±0.0012） mgCO2•m^-2•s^-1,最大排放速率出现在8月份0:00,为（0.22±0.0090） mgCO₂•m^-2•s^-1。生长季中6~9月份表现为明显的单峰型日变化,非生长季的变化幅度较小。净生态系统交换量（NEE）和生态系统总初级生产力（GPP）与气温、空气水气饱和亏和地表反射率等环境因素呈现相似的相关性,与地上生物量和群落叶面积指数则为线性负相关,生态系统呼吸（Res）则与上述因子的相关性呈现相反的趋势。     

CO2 flux in alpine wetland ecosystem on the Qinghai-Tibetan Plateau, China

Using the CO₂ flux data measured by the eddy covariance method in the northeast of Qinghai-Tibetan Plateau in 2005, we analyzed the carbon flux dynamics in relation to meteorological and biotic factors. The results showed that the alpine wetland ecosystem was the carbon source, and it emitted 316.02 gCO₂ · m⁻² to atmosphere in 2005 with 230.16 gCO₂ · m⁻² absorbed in the growing season from May to September and 546.18 gCO₂ · m⁻² released in the non-growing season from January to April and from October to December. The maximum of the averaged daily CO₂ uptake rates and release rates was (0.45 ± 0.0012) mgCO₂ · m⁻² · s⁻¹ (Mean ± SE) in July and (0.22 ± 0.0090) mgCO₂ · m⁻² · s⁻¹ in August, respectively. The averaged diurnal variation showed a single-peaked pattern in the growing season, but exhibited very small fluctuation in the non-growing season. Net ecosystem exchange (NEE) and gross primary production (GPP) were all correlated with some meteorological factors, and they showed a negatively linear correlation with aboveground biomass, while a positive correlation existed between the ecosystem respiration (R_es) and those factors.     

黄土高原农牧交错带稀疏自然植被生态系统的地表能量特征

基于2011-2012年黄土高原农牧交错带稀疏自然植被生态系统的地表能量通量以及气象数据,对该地区能量平衡各分量(净辐射、感热、潜热和土壤热通量)以及波文比进行日、季节动态的特征分析,研究了潜热通量和感热通量对不同强度降雨事件响应程度的差异,并分析了潜热通量和感热通量的主控因子.结果表明:该地区净辐射、感热、潜热和土壤热通量的日、季节动态曲线均为单峰型曲线,净辐射、感热通量、潜热通量和土壤热通量的年平均值分别为78.19、33.32、24.91和2.65 W·m-2.在全年能量收支平衡中,感热通量占净辐射的43％,潜热通量占32％,土壤热通量占3％,表明对于黄土高原农牧交错带自然稀疏灌木生态系统,全年能量主要以感热的形式交换.生长季感热和潜热占净辐射的比例相同(36％);而在非生长季,感热占主导,占净辐射的比例高达54％.潜热通量在强、弱降雨事件发生后明显升高,感热通量则明显下降.潜热通量与净辐射、水汽压差及植被参数均显著相关,感热通量与净辐射及空气温度梯度显著相关.     

基于过程模型的青藏高原湿地甲烷排放格局评估

甲烷(CH₄)是大气中最丰富的碳氢化合物,是仅次于二氧化碳(CO₂)的温室气体。湿地是甲烷的重要来源,在全球碳循环中发挥着重要作用,其排放的甲烷占所有天然甲烷排放源的70%,占全球甲烷排放总量的24.8%。青藏高原平均海拔4000 m以上,占有中国约三分之一的湿地。近几十年来,由于全球气候变暖和降水增加,该地区甲烷排放率和湿地面积都发生着巨大变化,因此,青藏高原湿地CH₄排放的长期变化在很大程度上仍存在较大的不确定性。利用TRIPLEX-GHG模型模拟了青藏高原湿地1978—2008年CH₄排放的动态特征,研究结果表明:(1)1978—2008年青藏高原湿地CH₄排放速率呈逐渐增加趋势。(2)青藏高原大多数湿地区域CH₄排放速率为0—6.13 g CH₄ m^-2 a^-1;东北部分湿地区域CH₄排放速率为6.14—20.19 g CH₄ m^...     

Impacts of the removal of vascular plants on physiological and biochemical characteristics of Syntrichia caninervis during winter season in a temperate desert

Aims Patchily distributed biological soil crusts and shrubs is one of the main vegetation cover types in Gurbantünggüt desert. The existence of shrubs in desert areas serves not only as a shelter for small animals, but also a good living condition for cryptogams and some herbs. Syntrichia caninervis, a dominant moss species in Gurbantünggüt desert, is patchily distributed under shrub canopy and open spaces between vascular plants. To our knowledge, the impacts of the removal of shrub canopy on physiological and biochemical characteristics of S. caninervis during the winter is still unknown.
Methods We simulated grazing of animals on Ephedra distachya at various rates (shrubs left intact, 50% shrubs removed, and shrubs removed completely) by cutting different percent of above-ground shoots of E. distachya. The shoot water content, chlorophyll fluorescence, proline content, soluble sugar content, soluble protein content, malonyldialdehyde (MDA) content, peroxidase (POD) and superoxide dismutase (SOD) activity were compared.
Important findings The results show that, as for proline and soluble sugar contents of tested S. caninervis, there were no significant differences among three treatments of shrub canopy. However, the MDA content, and the activities of POD, SOD, CAT were significantly higher than nature shrubs in snow cover periods. During snow-melting periods, soil moisture and temperature did not served as limiting factors on the growth of S. caninervis. The soluble sugar content, and the activities of POD, CAT with shrub removal were significantly higher than shrubs left intact. This may indicate that the decline of the function of maintaining constant soil temperature due to shrub canopy increased the damage of temperature on moss plants. In addition, as for physiological and biochemical characteristics, there were no significant differences between two treatments of 50% shrub canopy and shrub canopy left intact. In snow covered periods and snow melting periods, the MDA content, the activities of POD, SOD and CAT of S. caninervis under shrub canopy removed completely were significantly higher than that of 50% shrub canopy and shrub canopy left intact, except for soluble protein content. The duration of chlorophyll fluorescence activity of S. caninervis growing in habitats with shrubs removed completely was significantly shorter than that of S. caninervis growing in habitats of 50% shrub canopy and shrub canopy left intact. This result indicated that the removal of shrubs may increase the UV-B radiation and weaken the “moisture island effects” developed by the existence of shrub canopy.     

黄河三角洲芦苇湿地生态系统碳、水热通量特征

利用涡度相关法对黄河三角洲芦苇湿地生态系统进行了连续两年的通量观测,对2009—2010年生长季芦苇湿地的净生态系统碳交换量(NEE),感热通量(Hs)和潜热通量(LE)数据进行了分析。结果表明,在日尺度上,芦苇湿地NEE日变化特征表现为两个CO2吸收高峰,分别出现在11:00和16:00左右,其特点是在午间出现了碳交换通量的降低。CO2吸收的日最大值在两个生长季出现的时间有所不同,分别出现在2009年7月(-0.30 mg CO2m-2s-1)和2010年6月(-0.37 mg CO2m-2s-1)。CO2排放的日最大值两个生长季均出现在9月,分别为0.19和0.25 mg CO2m-2s-1。Hs和LE的日动态均为单峰型,极值都出现在中午前后,生长季生态系统的能量消耗主要以潜热为主,且在日尺度上,热通量和NEE有显著的负相关关系。在季节尺度上,芦苇湿地生长季具有明显的碳汇功能,2009年生长季生态系统白天固定354.63 g CO2/m2,同时期夜间释放159.24 g CO2/m2,净CO2吸收量为-195.39 g CO2/m2。2009年整个生长季生态系统总初级生产力(GPP)为-651.13 g CO2/m2,生态系统呼吸(Re)为455.74 g CO2/m2,系统表现为碳汇。路径分析表明:光合有效辐射(PAR)显著影响NEE的日动态(R2=0.46—0.84),而NEE的季节动态主要受土壤温度的影响,降水和PAR的影响次之。     

青藏高原高寒湿地GPP变化特征及对生长季积温的响应

基于涡度相关系统,利用2004—2016年的涡度相关系统观测资料,做了青藏高原高寒湿地生长季总初级生产力(GPP)在不同时间尺度上对生长季有效积温(GDD)响应的研究。结果表明:高寒湿地生态系统在生长季的日GPP、GDD与月际GPP、GDD都表现为先增大后减小的单峰变化趋势,都在7月或8月达到峰值,在5月达到最小值。在整个生长季尺度上,GPP与GDD变异性较大,没有明显的变化趋势。2004—2016年整个生长季GPP与GDD的均值分别为(458.82±25.78) gC m^-2季^-1和(1060.89±84.07)℃。在日尺度、月尺度、生长季尺度上,GPP与GDD都呈极显著正相关关系(P<0.01)。但是,通过比较生长季分别每个月GPP与GDD的关系发现,5、9月的GPP与GDD没有显著相关性(P>0.05),而在7月相关性最为显著(P<0.01)。整体上看,高寒湿地生态系统植被的总初级生产力与热量条件表现为正相关关系,由此说明在全球气候变暖的背景下,将会提高青藏高原高寒湿地生态系统植被的光合生产能力。     

Linking seed germination and plant height: a case study of a wetland community on the eastern Tibet Plateau

• Seed germination is the earliest trait expressed in a plant's life history, and it can directly affect the expression of post‐germination traits. Plant height is central to plant ecological strategies, because it is a major determinant of the ability of a species to compete for light. Thus, linking seed germination and plant height at the community level is very important to understanding plant fitness and community structure.
• Here, we tested storage condition and temperature requirements for germination of 31 species from a wetland plant community on the eastern Tibet Plateau and analysed correlation of germination traits with plant height in relation to storage condition.
• Germination percentage was positively related to plant height, and this relationship disappeared when seeds were incubated at a low temperature (i.e. 5 °C) or after they were stored under wet‐cold conditions. The response of seeds to dry+wet–cold storage was negatively related to plant height. Based on the scores of each species on the first two principal components derived from PCA, species were classified into two categories by hierarchical clustering, and there was a significant difference between germination and plant height of species in these two categories.
• These results suggest that the requirements for seed germination together with seasonal change in environmental conditions determine the window for germination and, in turn, plant growth season and resource utilisation and ultimately plant height.

     

青藏高原海北高寒湿地土壤呼吸对水位降低和氮添加的响应

近20年来, 青藏高原高寒湿地经历了明显的气候变化, 从而导致多数湿地水位下降和氮沉降的增加。对于湿地生态系统来说, 水位下降意味着土壤通气性能的改善, 可能会导致土壤呼吸的增加; 而氮沉降的增加可能会降低土壤微生物生物量和pH值, 从而可能抑制土壤呼吸。为此, 在青海海北高寒草地生态系统国家野外科学观测研究站利用中宇宙(Mesocosm)实验方法, 探讨了青藏高原高寒泥炭型湿地土壤呼吸对水位降低和氮添加的响应。结果表明: (1)水位降低显著增强了土壤呼吸, 而氮添加对土壤呼吸的影响依赖于水位的变化: 对照水位下, 氮添加显著抑制土壤呼吸; 而水位降低时, 氮添加对土壤呼吸速率无显著影响。(2)土壤呼吸速率与地上生物量、枯落物累积量之间呈显著正相关关系, 而与根系生物量无显著相关关系。(3)水位降低显著提高了土壤呼吸的温度敏感性, 而氮添加对其无显著的影响。因此预测: 随着氮沉降的升高, 高寒泥炭湿地土壤CO₂的排放量将会减少; 然而随着暖干化背景下水位的降低, 青藏高原高寒湿地会排放更多的CO₂。     

Considerable methane uptake by alpine grasslands despite the cold climate: in situ measurements on the central Tibetan Plateau, 2008–2013

The uptake of CH₄ by aerate soil plays a secondary role in the removal of tropospheric CH₄, but it is still highly uncertain in terms of its magnitude, spatial, and temporal variation. In an attempt to quantify the sink of the vast alpine grasslands (1 400 000 km²) of the Tibetan Plateau, we conducted in situ measurements in an alpine steppe (4730 m) and alpine meadow (4900 m) using the static chamber and gas chromatograph method. For the alpine steppe, measurements (2008–2013) suggested that there is large interannual variability in CH₄ uptake, ranging from ?48.8 to ?95.8 μg CH₄ m^?2 h^?1 (averaged of ?71.5 ± 2.5 μg CH₄ m^?2 h^?1), due to the variability in precipitation seasonality. The seasonal pattern of CH₄ uptakes in the form of stronger uptake in the early growing season and weaker uptake in the rainy season closely matched the precipitation seasonality and subsequent soil moisture variation. The relationships between alpine steppe CH₄ uptake and soil moisture/temperature are best depicted by a quadratic function and an exponential function (Q₁₀ = 1.67) respectively. Our measurements also showed that the alpine meadow soil (average of ?59.2 ± 3.7 μg CH₄ m^?2 h^?1) uptake less CH₄ than the alpine steppe and produces a similar seasonal pattern, which is negatively regulated by soil moisture. Our measurements quantified – at values far higher than those estimated by process‐based models – that both the alpine steppe and alpine meadow are considerable CH₄ sinks, despite the cold weather of this high‐altitude area. The consecutive measurements gathered in this study also highlight that precipitation seasonality tends to drive the interannual variation in CH₄ uptake, indicating that future study should be done to better characterize how CH₄ cycling might feedback to the more extreme climate.     

黄土丘陵沟壑区典型人工林土壤CO2释放规律及其影响因子

为了解黄土丘陵沟壑区人工林土壤有机碳排放特征,于2007年8月、2007年10月和2008年5月对黄土丘陵沟壑区杏树、沙棘和刺槐3种人工林下土壤CO2释放速率及相关环境因子进行研究,探讨了半干旱地区侵蚀环境下不同植被土壤CO2释放速率的变化规律及影响因子.杏树、沙棘和刺槐3种人工林土壤CO2释放存在差异,日平均释放速率分别为0.83～2 61μmol·m-2·s-1、0.83～3.32μmol·m-2·s-1和0.80～3.45μmol·m-2·s-1,刺槐和沙棘人工林土壤CO2释放速率高于杏树林,3种人工林的土壤CO2释放速率日变化及季节性变化表现一致,春季和夏季的土壤CO2释放高于秋季.相关分析表明,土壤温度是影响土壤CO2释放的主要因子,但在干旱的春季和夏季,土壤水分是土壤CO2释放的主要限制因子,同时,土壤理化性质和微生物生物量也对土壤CO2释放有显著影响.