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981.
运用LI-6400便携式光合作用系统测定了不同光强(2000、1500、1000和500 μmol·m-2·s-1)和两种O2浓度(21%和2%的O2)下冬小麦(Triticum aestivum)灌浆期旗叶的CO2响应曲线, 比较了现有CO2响应模型(生化模型、直角双曲线模型和直角双曲线修正模型)拟合给出光下(暗)呼吸与测量值之间的差异。结果显示, 直角双曲线修正模型所给出的光下呼吸速率拟合值与测量值最为接近。植物光合作用对大气CO2响应(A/Ca)的拟合结果优于光合作用对胞间CO2浓度(A/Ci)的拟合。然而, 所有模型基于A/Ca拟合的光下(暗)呼吸在整体上与测量值存在显著差异(p < 0.05), 推测与现有模型没有考虑CO2浓度对光呼吸和光下暗呼吸速率的影响有关。对小麦的试验结果表明, CO2浓度对光呼吸和光下暗呼吸均有显著影响: 随着CO2浓度的增加(0-1400 μmol·mol-1), 不同光强下的表观光呼吸变化范围分别为5.035-11.670、4.222-11.650、4.330-10.999和3.263-9.094 μmol CO2·m-2·s-1; 光下暗呼吸的变化范围分别为0.491-2.987、0.457-2.955、0.545-3.139和0.448-3.139 μmol CO2·m-2·s-1。回归分析发现, 表观光呼吸和光下暗呼吸与CO2浓度之间均存在较好的相关性。然而, 将该回归关系整合到现有模型中, 是否会优化模型, 从而提高模型对相关光合参数估算的准确性尚有待于进一步研究。 相似文献
982.
Ecophysiology of six selected shrub species in different plant communities at the periphery of the Atlantic Forest of SE-Brazil 总被引:2,自引:1,他引:1
Heitor Monteiro Duarte Arthur Geßler Fabio Rubio Scarano Augusto Csar Franco Eduardo Arcoverde de Mattos M. Nahm Heinz Rennenberg Pablo Jos Francisco Pena Rodrigues Henrique Leo Teixeira Zaluar Ulrich Lüttge 《Flora》2005,200(5):456-476
The Atlantic rain forest of Brazil is one of the 25 biodiversity hotspots of the world. It is surrounded by distinct marginal plant communities which are floristically related to the rain forest. We performed an in situ ecophysiological study of six shrub and tree species which are abundant in one or more of these marginal ecosystems. They formed three pairs of taxonomically related species, which, however, differed in geographic distribution and/or habitat preference. We aimed to answer the following questions: (1) Do habitat generalists and specialists differ in ecophysiological behaviour? (2) Are there general trends responsive to site characteristics, irrespective of taxonomic affiliation? (3) In which variables between-site intraspecific variation is more often detected? Plants chosen were the Clusiaceae Calophyllum brasiliense Cambess (swamp forest specialist) and Rheedia brasiliensis (Mart.) Planch &; Triana (a generalist plant, occurring in swamp forests and dry, sandy coastal vegetation); the Myrsinaceae Myrsine parvifolia A.DC. (widespread in sandy plains) and Myrsine gardneriana A.DC. (widespread in high-altitude habitats); and the Euphorbiaceae Styllingia dichotoma Muell. Arg. (a coastal inselberg specialist) and Croton compressus Lam. (a generalist found in coastal inselbergs and dry forests). We compared measurements of photosynthesis (chlorophyll fluorescence parameters), stable isotope (δ13C, δ15N) and metabolic carbon and nitrogen compounds. Generalists and specialists did not always differ in ecophysiological behaviour: for instance, while widespread generalists such as M. parvifolia and C. compressus were ecophysiologically versatile, R. brasiliense appeared to perform below optimum in all sampled habitats. Light and water were abiotic factors which apparently explained most of the variation found. Overall, ecophysiological responses were often more clearly related to individual species rather than to taxonomic affinities in higher hierarchies (family, genus) or habitat. These results are discussed as a further indication of high biodiversity even in habitats marginal to the rain forest hotspot. 相似文献
983.
乳白蚁Coptotermes在湖北宜昌地区每年11月~次年3月收集到的巢群,每年品级比例基本平衡。品级头比的数据一律来自1月份的巢群;品级重比是11月~次年3月的巢群。品级的比例分别为:工蚁占81.70%、干重比69.45%;兵蚁占7.50%、干重比7.69%;生殖蚁占10.80%、干重比26.76%。 相似文献
984.
Biodiversity of benthic invertebrates and organic matter processing in shallow marine sediments: an experimental study 总被引:2,自引:0,他引:2
Florian Mermillod-Blondin Frédérique François-Carcaillet Rutger Rosenberg 《Journal of experimental marine biology and ecology》2005,315(2):187-209
The main objective of this study was to measure the impact of benthic invertebrate diversity on processes occurring at the water-sediment interface. We analyzed the effects of interactions between three shallow water species (Cerastoderma edule, Corophium volutator, and Nereis diversicolor). The impacts of different species richness treatments were measured on sediment reworking, bacterial characteristics, and biogeochemical processes (bromide fluxes, O2 uptake, nutrient fluxes, and porewater chemistry) in sediment cores. The results showed that the three species exhibited different bioturbation activities in the experimental system: C. edule acted as a biodiffusor, mixing particles in the top 2 cm of the sediments; C. volutator produced and irrigated U-shaped tubes in the top 2 cm of the sediments; and N. diversicolor produced and irrigated burrow galleries in the whole sediment cores. C. edule had minor effects on biogeochemical processes, whereas the other species, through their irrigation of the burrows, increased the solute exchange between the water column and the sediment two-fold. These impacts on sediment structure and solute transport increased the O2 consumption and the release of nutrients from sediments. As N. diversicolor burrowed deeper in the sediment than C. volutator, it irrigated a greater volume of sediments, with great impact on the sediment cores.Most treatments with a mixture of species indicated that observed values were often lower than predicted values from the addition of the individual effects of each species, demonstrating a negative interaction among species. This type of negative interaction measured between species on ecosystem processes certainly resulted from an overlap of bioturbation activities among the three species which lived and foraged in the same habitat (water-sediment interface). All treatments with N. diversicolor (in isolation and in mixture) produced similar effect on sediment reworking, water fluxes, nutrient releases, porewater chemistry, and bacterial characteristics. Whichever species associated with N. diversicolor, the bioturbation activities of the worm hid the effect of the other species. The results suggest that, in the presence of several species that use and modify the same sediment space, impact of invertebrates on ecosystem processes was essentially due to the most efficient bioturbator of the community (N. diversicolor). In consequence, the functional traits (mode of bioturbation, depth of burrowing, feeding behaviour) of an individual species in a community could be more important than species richness for some ecosystem processes. 相似文献
985.
David Devreker Laurent Seuront 《Journal of experimental marine biology and ecology》2005,318(2):145-162
The influence of temperature and chlorophyll concentration on egg production, hatching success, female survival and body size of the copepod Temora longicornis was investigated in situ in the coastal waters of the Eastern English Channel. Twenty samples were collected between February and July 2003 three to four times per month. The maximum daily level of egg production of 75.5 eggs female−1 was observed in March, with minima of 10 eggs female−1 in February and July. Between February and March egg production increased with chlorophyll concentration. At the end of March a decrease in egg production corresponded to a strong increase in chlorophyll concentration that indicated a Phaeocystis-dominated bloom. After this period egg production closely followed the temporal variation in chlorophyll concentration with a maximum of 55.3 eggs female−1 in April during a second peak of chlorophyll concentration. Hatching success varied between 60% and 80% and was not influenced by chlorophyll concentration, in situ temperature or any other biological parameter considered in this study. Increases in temperature from February to July paralleled a decrease in body length and an increase in the percentage of spawning females. Mean female survival followed the variation of both temperature and chlorophyll concentration only between April and July. Temperature and chlorophyll concentration affected the reproductive parameters of T. longicornis differently. Female survival and body size were negatively correlated with temperature, while the highest chlorophyll concentrations were not always favourable for egg production. Therefore the quality of food should not be associated with chlorophyll quantity. Furthermore, the maximum values of egg production in this study are the highest recorded for T. longicornis. This study, conducted for the first time in the Eastern English Channel, showed high levels of productivity of T. longicornis despite a decrease of egg production during a Phaeocystis sp. dominated bloom in April. 相似文献
986.
Geeta Shrestha Vaidya Keshab Shrestha Buddi R. Khadge Nancy C. Johnson Håkan Wallander 《Restoration Ecology》2008,16(1):79-87
Erosion resulting from landslides is a serious problem in mountainous countries such as Nepal. To restore such sites it is essential to establish plant cover that protects the soil and reduces surface erosion. Mycorrhizal fungi growing in symbiosis with plants are essential in this respect because they improve both plant nutrient uptake and soil structure. We investigated the influence of organic matter and P amendment on recently produced biomass of bacteria and arbuscular mycorrhizal (AM) fungi in eroded slopes in Nepal. Eroded soil mixed with different types of organic matter or P was placed in mesh bags, which were buried around trees of Bauhinia purpurea and Leucaena diversifolia between June 2003 and December 2003 (the wet season) or between December 2003 and June 2004 (the dry season). Signature fatty acids were used to determine bacterial and AM fungal biomass after the 6‐month intervals. The amount and composition of AM fungal spores were analyzed in the mesh bags from the dry season. More microbial biomass was produced during the wet season than during the dry season. Furthermore, organic matter addition enhanced the production of AM fungal and bacterial biomass during both periods. The positive influence of organic matter addition on AM fungi could be an important contribution to plant survival in plantations on eroded slopes. Different AM spore communities and bacterial profiles were obtained with different organic amendments and this suggests a possible way of selecting for specific microbial communities in the management of eroded sites. 相似文献
987.
Increased night temperature reduces the stimulatory effect of elevated carbon dioxide concentration on methane emission from rice paddy soil 总被引:1,自引:0,他引:1
WEIGUO CHENG HIDEMITSU SAKAI ANNE HARTLEY† KAZUYUKI YAGI TOSHIHIRO HASEGAWA 《Global Change Biology》2008,14(3):644-656
To determine how elevated night temperature interacts with carbon dioxide concentration ([CO2]) to affect methane (CH4) emission from rice paddy soil, we conducted a pot experiment using four controlled‐environment chambers and imposed a combination of two [CO2] levels (ambient: 380 ppm; elevated: 680 ppm) and two night temperatures (22 and 32 °C). The day temperature was maintained at 32 °C. Rice (cv. IR72) plants were grown outside until the early‐reproductive growth stage and then transferred to the chambers. After onset of the treatment, day and night CH4 fluxes were measured every week. The CH4 fluxes changed significantly with the growth stage, with the largest fluxes occurring around the heading stage in all treatments. The total CH4 emission during the treatment period was significantly increased by both elevated [CO2] (P=0.03) and elevated night temperature (P<0.01). Elevated [CO2] increased CH4 emission by 3.5% and 32.2% under high and low night temperature conditions, respectively. Elevated [CO2] increased the net dry weight of rice plants by 12.7% and 38.4% under high and low night temperature conditions, respectively. These results imply that increasing night temperature reduces the stimulatory effect of elevated [CO2] on both CH4 emission and rice growth. The CH4 emission during the day was larger than at night even under the high‐night‐temperature treatment (i.e. a constant temperature all day). This difference became larger after the heading stage. We observed significant correlations between the night respiration and daily CH4 flux (P<0.01). These results suggest that net plant photosynthesis contributes greatly to CH4 emission and that increasing night temperature reduces the stimulatory effect of elevated [CO2] on CH4 emission from rice paddy soil. 相似文献
988.
989.
Aims: To investigate the impact of aquatic humic matter on the inactivation of Escherichia coli and Bacillus subtilis by ultraviolet (UV) light.
Methods and Results: A bench-scale study investigated the potential for Aldrich® humic acid (AHA) and Suwannee River natural organic matter (SR-NOM) to coat the surface of E. coli and B. subtilis and offer protection from low-pressure UV light. UV doses of 5 and 14 mJ cm−2 were applied using a collimated beam at four concentrations of humic matter (0, 10, 50 and 120 mg l−1 ) in reagent grade water. Both AHA and SR-NOM were found to offer statistically significant protection of both E. coli and B. subtilis at concentrations of 50 and 120 mg l−1 for a UV dose of 14 mJ cm−2 .
Conclusions: Both E. coli and B. subtilis are susceptible to coating by humic matter which can reduce the sensitivity of the cells to UV light.
Significance and impact of the study: Micro-organisms in the environment may acquire characteristics through interaction with humic matter that render them more resistant to UV disinfection than would be predicted based on laboratory inactivation studies using clean cells. 相似文献
Methods and Results: A bench-scale study investigated the potential for Aldrich
Conclusions: Both E. coli and B. subtilis are susceptible to coating by humic matter which can reduce the sensitivity of the cells to UV light.
Significance and impact of the study: Micro-organisms in the environment may acquire characteristics through interaction with humic matter that render them more resistant to UV disinfection than would be predicted based on laboratory inactivation studies using clean cells. 相似文献
990.
Spawning salmon deliver nutrients (salmon-derived nutrients, SDN) to natal watersheds that can be incorporated into terrestrial
and aquatic food webs, potentially increasing ecosystem productivity. Peterson Creek, a coastal watershed in southeast Alaska
that supports several species of anadromous fish, was sampled over the course of a storm during September 2006 to test the
hypothesis that stormflows re-introduce stored SDN into the stream. We used stable isotopes and PARAFAC modeling of fluorescence
excitation–emission spectroscopy to detect flushing of DOM from salmon carcasses in the riparian zone back into a spawning
stream. During the early storm hydrograph, streamwater concentrations of NH4–N and total dissolved phosphorus (TDP), the fluorescent protein tyrosine and the δ15N content of DOM peaked, followed by a rapid decrease during maximum stormflow. Although δ15N has previously been used to track SDN in riparian zones, the use of fluorescence spectroscopy provides an independent indicator
that SDN are being returned from the riparian zone to the stream after a period of intermediate storage outside the stream
channel. Our findings further demonstrate the utility of using both δ15N of streamwater DOM and fluorescence spectroscopy with PARAFAC modeling to monitor how the pool of streamwater DOM changes
in spawning salmon streams. 相似文献