温度和氮素输入对青藏高原三种高寒草地土壤碳矿化的影响

选取了海北高寒草甸、那曲高寒草原和当雄高寒湿地3种典型高寒草地生态系统类型为研究对象,采集了表层0~10 cm土壤,在实验室内进行可控温度下的碳矿化培养实验。结果表明,青藏高原土壤碳矿化在不同高寒草地类型间存在显著差异（P≤0.05）。在较低的温度下,高寒湿地土壤的碳矿化速率显著低于高寒草甸土壤,而温度在15℃左右时,高寒湿地土的碳矿化速率略高于高寒草甸土壤,当温度处于较高的水平时（〉20℃）,高寒湿地土壤碳矿化速率远高于高寒草甸土壤,高寒湿地土壤碳矿化的Q10显著大于高寒草甸。无论是低温还是较高的温度,高寒草原土壤碳矿化速率最低,数值范围也最窄。高寒草甸和高寒湿地土壤碳矿化均受温度的显著影响（P≤0.05）,其速率均跟温度呈现一级指数函数方程关系,而高寒草原土壤碳矿化速率与温度间未呈现明显的函数关系,但不同温度间的土壤碳矿化速率存在显著差异。氮素输入对高寒草甸和高寒湿地土壤碳矿化的影响不明显,但显著促进了高寒草原土壤碳矿化作用。     

黄河源区退化高寒草地土壤种子库:种子萌发的数量和动态

对青藏高原黄河源区不同退化程度高寒草地的土壤种子库土样用土壤分析筛进行浓缩,并以萌发法分析土壤种子库萌发种子数量和动态.结果表明,孔径0.25~2 mm的土壤分析筛分离土样中萌发种子可达萌发种子总量的85%~97%,而小于0.25 mm的土样中未发现种子.因此,用0.25 mm孔径大小的土壤筛对高寒草地土壤种子库土样进行大规模浓缩是一种方便、可靠的方法.4种不同退化程度高寒草地(A:未退化草甸;B:轻度退化草甸;C:中度退化草甸;D:重度退化草甸)的土壤种子库在实验室条件下萌发的种子数量分别为:A 1 194~3 744粒/m2,平均2 421.3粒/m2;B 5 376~1 0912粒/m2,平均7 786.7粒/m2;C 2 304~1 3216粒/m2,平均8 695.5粒/m2;D 4 768~12 352粒/m2,平均8 125.9粒/m2.除样地A外,其它3个样地的可萌发种子数量差异不大.单子叶植物种子在培养到d 10左右开始萌发,双子叶植物在5~7 d内开始萌发,前者3 wk后基本不再萌发,后者5 wk左右停止萌发.4个样地土壤种子库种子萌发主要集中在第2~3周,并表现出近似单峰型格局.图1表3参39     

青藏高原东缘不同林龄云杉林冬季土壤呼吸特征

采用动态密闭气室红外CO_2 分析法(IRGA),连续定位测定青藏高原东部4种不同恢复阶段的人工云杉林和原始云杉林在冬季(2007.11.01～2008.03.31)的土壤呼吸.用挖壕沟法同步区分土壤自养呼吸和异养呼吸,并同步测定土壤5 cm温度和水分结果表明,土壤5 cm温度与冬季土壤呼吸速率具有显著的正指数相关关系,土壤含水量与冬季土壤呼吸的相关性不明显.亚高山针叶林冬季土壤呼吸温度系数Q_(10) 值为3.180 3～6.546 9,不同年龄阶段针叶林的Q_(10)值大小依次为:35 a人工云杉林>47 a人工云杉林>65 a人工云杉林>22 a人工云杉林>原始云杉林.22 a、35 a、47 a、65 aA工云杉林和原始云杉林冬季土壤总呼吸碳释放通量别为200.16、196.23、166.71、228.47、261.75 g(C)m~2,随着森林恢复更新,冬季土壤呼吸通量呈现出先下降后升高的趋势,这种变化趋势的拐点出现在47 a人工林附近.温度是影响土壤自养呼吸贡献率和异养呼吸贡献率的主要因子,温度与异养呼吸贡献率成负相关.22 a、35 a、47 a、65a人工云杉林和原始云杉林冬季土壤的自养呼吸和异养呼吸碳释放通量平均值分别为133.44、134.04、115.97、166.05、199.07 g(C)m~(-2)和66.71、62.20、50.73、62.43、62.68 g(C)m~(-2).图7表3参34     

季节性雪被对青藏高原东缘高寒草甸土壤氮矿化的影响

依据自然雪被分布的差异,在青藏高原东缘高寒草甸中设置3条样带(即深雪、中等厚度雪被和浅雪),于2008年的秋冬过渡期,连续监测各样带中的雪被厚度和土壤温度,并采用原位培养法测定每月的土壤氮素氨化、硝化和矿化速率,以研究不同厚度雪被对高寒草甸土壤氮矿化的影响.结果表明,月均土温、每月日最高土温均值分别与雪被厚度极显著相关,二次函数关系拟合较好(R2=0.576,0.685),且根据每月日最高土温均值与雪被厚度的二次函数关系方程可知,25 cm厚的雪被可以起到较好的隔绝效果;土壤含水量受雪被厚度和土壤温差两个因素的显著影响.在秋冬过渡期末,浅雪梯度下土壤硝态氮含量显著降低,且雪被下的净氮矿化速率与月均土温、每月日最高土温均值、每月日最低土温均值都分别呈极显著相关,二次函数关系拟合较好(R2=0.589,0.541,0.601).研究表明,不同厚度的雪被对土壤温度和含水量影响显著,从而显著地影响着土壤氮的矿化,深雪更有利于氨化、硝化和氮矿化.图7表2参36     

青藏高原高寒草甸土壤真菌多样性与植物群落功能性状和土壤理化特性的关系

为探究高寒草甸土壤真菌多样性与植物群落功能性状(community-weighted mean,CWM;functional diversity,FD)及土壤理化特性的关系,选取3个试验点,每个试验点选择4种生境(沟底平地、阴坡、阳坡和山顶),采用高通量测序技术分析各生境土壤真菌多样性特点;利用广义线性混合模型,比较土...     

不同海拔高寒放牧草甸的生态系统呼吸与环境因子的关系

在全球变化的背景下,为了研究藏北高寒放牧草甸的生态系统呼吸和土壤呼吸特征,沿着3个海拔高度（4 300、4 500和4 700 m）观测了2010年7-9月白天的呼吸通量。同时,观测了同期的土壤温度、土壤水分含量、空气温度和相对湿度,在定性分析土壤水分含量和呼吸通量关系的基础上,将其分成低、中和高3个水平,在此基础上,分析生态系统呼吸、土壤呼吸与土壤温度、土壤水分含量、空气温度以及相对湿度的关系。结果表明,空气温度是决定生态系统呼吸和土壤呼吸变异的主导因子;生态系统呼吸、土壤呼吸以及裸地的土壤呼吸的Q10值分别为1.83～3.07、1.54～4.13和1.29～2.89;总体而言,生态系统呼吸和土壤呼吸Q10值随着海拔的升高和土壤水分含量的增加而增大。     

青海高寒草甸草地退化的遥感技术调查分析

应用遥感技术探讨了巴颜喀拉山北坡,青海省达日县段退化高寒草甸草地的成因、分布、面积和遥感判译标志,将研究区内高寒草地划分为５个类,２个亚类和３个退化草地型．重点分析了高山草甸草地退化的主要原因和遥感影像特征     

风蚀条件下人类活动对高寒草地水分保持功能影响的定量模拟

青藏高原是我国重要的生态屏障,具有重要的水源涵养功能。高寒草地生态系统退化将严重地影响高原的水源涵养功能。为了定量研究人类活动对青藏高原高寒草地水分保持功能的影响,采用大型风洞实验,模拟人类不同的干扰方式和干扰程度对高寒草地土壤水分保持功能的影响。实验样品采自青藏高原三个草地类型:高寒草甸、草原化草甸和高寒草原。干扰方式包括破坏草地地上部分和根系,干扰程度包括轻干扰、中度干扰、重度干扰和全部破坏。实验结果表明,地上部分破坏后,土壤含水率均有下降,降幅分别为:QZ1为6.9%～9.2%、QZ2为6.8%～10.1%、QZ3为9%～10%;当根系遭到破坏后土壤含水率的降幅则分别为:QZ1为16%～30%,QZ2为17.25～32.1%,QZ3为22%～50%,显然,根系破坏后土壤含水率降幅远大于地表植被破坏后的情形。因此,植被根系是高寒草地水分保持功能的关键。随着干扰程度的加剧,土壤含水率在迅速下降。从试验模拟结果看,三个草地类型中土壤水分保持功能分别是高寒草甸>草原化草甸>高寒草原。     

青藏高原东部高寒草甸植物δ13C年间变化及其环境分析

植物有机体稳定碳同位素组成受植物生长期间气候环境因子的影响,包含了大量的环境信息。要真正理解植物体同位素组成所包含的环境信息首先要研究植物体同位素组成与环境之间的关系。文章通过分析2002年和2003年青藏高原东部青海省门源县境内隶属于19科41属51种植物叶片的δ13C值,研究高寒草甸植物稳定碳同位素组成的年间变化及其与环境因子的关系,分析影响δ13C值变化的关键因子。结果表明,所测植物的δ13C值分布在一个很小的范围-29.2‰～-24.9‰之间,平均值为-26.9‰,说明所测植物的光合作用均通过C3途径实现,这可能与该研究区较低温度有关。研究发现一年生植物δ13C值明显低于多年生植物,而且一年生和多年生植物δ13C值之间的差异在2002年(t=-3.031,P<0.01)和2003年(t=-3.567,P<0.001)均能达到显著性水平,表明多年生植物水分利用效率显著高于一年生植物,能更好的适应该地区寒冷干燥的低温环境。两年间植物δ13C值有明显不同,2003年显著低于2002年(t=6.786,P<0.001)。通过分析两年间环境因子的变化认为植物叶片δ13C值的年间变化主要是由于降水的变化引起的,随降雨量的增加而降低。不同植物种δ13C值年间变化差别很大,反应了植物对环境变化的不同响应。在植被恢复中应选用植物δ13C值随环境变化存在较大差异的物种,因为此类物种能够采取不同的对策适应该地区环境的变化。     

Effect of nitrification inhibitor on plant biomass and N2O emission rates in alpine meadows on the Tibetan Plateau

ABSTRACT

Treatment with nitrification inhibitors, such as dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP) have been strongly indicated to increase grassland biomass and mitigate soil N₂O emission rates. However, the responses of both alpine meadow aboveground biomass and N₂O emission rates to nitrification inhibitors remains unclear. We separately applied three doses of DCD and DMPP to alpine grassland soils with three duplicates. The biomass and N₂O emission rates were subsequently measured by a clear-cut method and in-situ static chamber gas chromatography during the growing season. Our findings indicated that aboveground biomass increased significantly, and N₂O emission rate decreased significantly at 6.8?kg?ha^?1 DCD and DMPP. Furthermore, the biomass increase effect was more significant than the N₂O emission rate mitigation effect (p?<?0.05). The highest ratios of DCD treatments on meadow production increase and N₂O emission rate decrease were 27.2% and 36.3%, respectively. Our findings provide insight into the enhanced grassland primary production and decreased N₂O flux by nitrification inhibitor treatment in alpine meadows, which may be beneficial to help mitigate global warming.     

测定方法和植物生长对土壤呼吸的影响

2.中国科学院研究生院,北京100039摘要:植物根系活动和测定方法是研究陆地生态系统土壤呼吸的重要影响因素。文章通过动态气室-IRGA法和静态气室-GC法研究了田间受根系影响和不受根系影响土壤的呼吸速率,分析了根系活动对土壤呼吸速率的影响程度,并比较了两种测定方法间的差异。研究表明,受根系影响处理的土壤呼吸速率显著高于不受根系影响的处理;受根系活动影响处理的土壤呼吸速率为静态气室-GC法>动态气室-IRGA法;而不受根系活动影响处理的土壤呼吸速率则恰好相反,为动态气室-IRGA法>静态气室-GC法;两种方法在测土壤呼吸时存在显著差异;但两种方法所测土壤呼吸速率间呈极显著的线性相关;两种方法间所获数据可以互相转换参比。     

Self-organized spatial patterns of vegetation in alpine grasslands

There is increased interest in vegetation spatial pattern as an indicator of transition shifts following catastrophes. Much, however, remains unknown about the mechanisms that underlie spatial pattern formations. In this study, we examined how the spatial heterogeneity of species distributions in the grasslands of the Central Pyrenees and Middle Atlas Mountains is associated with plant species diversity and the importance of self-organizing processes in the control of pattern formations. In the grasslands of the Central Pyrenees and Middle Atlas, the spatial heterogeneity of species distributions increased along a habitat degradation gradient defined by an increase in bare soil. In Central Pyrenees grasslands, however, the increase in heterogeneity was associated with self-organizing bare soil formations, rather than the self-organizing distribution of plant species. In Middle Atlas grasslands, the increased heterogeneity of species spatial distributions was a consequence of the self-organizing capacity of the composing species; the increase in bare soil was randomly distributed. In the more heavily grazed grasslands (Middle Atlas), but not in the more lightly grazed and better preserved ecosystem (Central Pyrenees), plant species richness and diversity declined significantly with an increase in grazing pressure because fewer species were able to colonize empty space. On the contrary, the colonization of bare soil by new species increased the diversity and spatial organization of new colonizing species in Central Pyrenees grassland.     

Effects of temperature on photosynthesis and respiration in hermatypic corals

Photosynthesis and respiration rates of the reef corals Pocillopora damicornis (Linn.), Montipora verrucosa (Lamarck), Porites compressa Dana and Fungia scutaria Lamarck were measured under controlled temperatures. Results indicate that coral metabolism is closely adapted to ambient temperature conditions. Tropical corals measured at Enewetak, Marshall Islands, showed greater primary production compared to maintenance requirements at elevated temperatures than did subtropical varieties of the same species in Hawaii. Photosynthesis: respiration (P:R) ratios were significantly and negatively related with temperature between 18° and 31°C for all Hawaiian corals, whereas at Enewetak this ratio generally showed a curvilinear relationship for this temperature range. Extrapolations of P:R regressions on temperatures to a value of 2.0 (estimated as a minimum required for long-term functional autotrophy) coincide for Hawaiian specimens with published upper lethal temperatures. Extrapolation of P:R regressions for Enewetak specimens at temperatures above 25°C suggests lethal temperatures for these corals to be 2 to 5 C° higher than for Hawaiian corals, in good agreement with recent experimental findings. Interspecific differences in P:R temperature regressions for Hawaiian corals correlating with upper lethal temperature tolerances are described.Contribution No. 505 of the Hawaii Institute of Marine Biology.     

外来入侵植物化感作用与土壤相互关系研究进展

文章以全球普遍关注的外来植物入侵为背景,综述了外来入侵植物化感物质与土壤化学性质(土壤pH,土壤有机碳和有机质,土壤中的化学元素等)、土壤生物群落(土壤微生物、土壤动物)的关系。并探讨了未来研究需要加强的几个方面,包括将化感作用与野外实际情况相结合研究,更真实的反映田间状况;进一步探讨微生物在化感物质生物变化过程中的作用及其机理;化感物质作为信号物质如何影响微生物代谢,从而影响地上植物;深入研究化感作用与土壤之间的相互关系,为入侵植物生物防治的安全性提供理论指导等方面。     

Symbiont photosynthesis increases both respiration and photosynthesis in the symbiotic sea anemone Anemonia viridis

Dark respiration of the symbiotic sea anemone Anemonia viridis (Forskäl) was observed to increase by 34% when anemones were exposed to hyperoxic sea water (150% oxygen saturation) overnight, and by 39% after exposure to 6 h in the light at a saturating irradiance of 300 E m^-2 s^-1 at normoxia (100% oxygen saturation). No increase due to light stimulation was observed in aposymbiotic control anemones. In darkness, the oxygen concentration of the coelenteric fluid was hypoxic. However, within 10 min of anemones being illuminated, coelenteric fluid was hyperoxic, and it remained elevated throughout a 12 h light period. When measured over a 24 h period (12 h light: 12 h dark), the dark respiration rate increased gradually over the first 6 h of the light period until it was 35% above the dark night-time resting rate. It remained elevated throughout the remaining light period and for 2 h into the following dark period, after which it fell back to the resting rate. Gross photosynthesis (P ^gross) increased significantly when anemones were exposed to either hyperoxia (150% oxygen saturation) or 300 E m^-2 s^-1 at normoxia. This increase was not observed when symbiotic anemones were illuminated at a low-light intensity of 100 E m^-2 s^-1. The results of this study suggest that respiration in the dark is limited by oxygen diffusion and that normal respiration is restored in the daytime by utilisation of the oxygen released by photosynthesis. Furthermore, it appears that the increased respiration following exposure to high-light intensities provides a CO₂-rich intracellular environment which further enhances the photosynthetic rate of the zooxanthellae.     

黄土高原植被破坏与重建过程中土壤侵蚀强度变化

运用137Cs示踪方法,通过采集不同利用方式的坡面土壤,研究了黄土高原典型丘陵区流域植被破坏与重建过程中土壤侵蚀强度的变化情况.研究结果表明:植被破坏耕垦后使137Cs遭受了大量流失,坡耕地耕垦时间越长,土壤侵蚀愈严重;植被恢复重建有效地减轻了侵蚀强度;通过比较刺槐林、果园及封禁自然恢复的撂荒地三种植被建造方式的土壤侵蚀模数,发现以封禁自然恢复的撂荒地土壤保持效果最好,其次是刺槐林,最差的是果园,其原因与果园的管理方式有关.立地条件不同的同种植被建造方式.土壤侵蚀强度差异较大,表现为峁坡阳坡此槐林地侵蚀模数远远大于谷坡阴坡刺槐林地.根据退耕时间不同的坡地土壤侵蚀强度的变化及流域土地利用类型的变化等方面对燕沟流域土壤侵蚀变化趋势作了进一步预测.