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41.
Evapotranspiration and water use efficiency in a Chesapeake Bay wetland under carbon dioxide enrichment 总被引:2,自引:0,他引:2
Wetlands evapotranspire more water than other ecosystems, including agricultural, forest and grassland ecosystems. However, the effects of elevated atmospheric carbon dioxide (CO2) concentration (Ca) on wetland evapotranspiration (ET) are largely unknown. Here, we present data on 12 years of measurements of ET, net ecosystem CO2 exchange (NEE), and ecosystem water use efficiency (EWUE, i.e. NEE/ET) at 13:00–15:00 hours in July and August for a Scirpus olneyi (C3 sedge) community and a Spartina patens (C4 grass) community exposed to ambient and elevated (ambient+340 μmol mol?1) Ca in a Chesapeake Bay wetland. Although a decrease in stomatal conductance at elevated Ca in the S. olneyi community was counteracted by an increase in leaf area index (LAI) to some extend, ET was still reduced by 19% on average over 12 years. In the S. patens community, LAI was not affected by elevated Ca and the reduction of ET was 34%, larger than in the S. olneyi community. For both communities, the relative reduction in ET by elevated Ca was directly proportional to precipitation due to a larger reduction in stomatal conductance in the control plants as precipitation decreased. NEE was stimulated about 36% at elevated Ca in the S. olneyi community but was not significantly affected by elevated Ca in S. patens community. A negative correlation between salinity and precipitation observed in the field indicated that precipitation affected ET through altered salinity and interacted with growth Ca. This proposed mechanism was supported by a greenhouse study that showed a greater Ca effect on ET in controlled low salinity conditions compared with high salinity. In spite of the differences between the two communities in their responses to elevated Ca, EWUE was increased about 83% by elevated Ca in both the S. olneyi and S. patens communities. These findings suggest that rising Ca could have significant impacts on the hydrologic cycles of coastal wetlands. 相似文献
42.
LYNNE E. STENZEL GARY W. PAGE JANE C. WARRINER JOHN S. WARRINER KRISTINA K. NEUMAN DOUGLAS E. GEORGE CARLETON R. EYSTER FRANCES C. BIDSTRUP 《Ibis》2011,153(2):312-322
Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males. 相似文献
43.
44.
GUILLAUME TCHERKEZ RUDI SCHÄUFELE SALVADOR NOGUÉS CLÉMENT PIEL ARNOUD BOOM GARY LANIGAN CÉCILE BARBAROUX CATARINA MATA SLIMAN ELHANI DEBBIE HEMMING CHRISTINA MAGUAS DAN YAKIR FRANZ W. BADECK HOWARD GRIFFITHS HANS SCHNYDER JALEH GHASHGHAIE 《Plant, cell & environment》2010,33(6):900-913
While there is currently intense effort to examine the 13C signal of CO2 evolved in the dark, less is known on the isotope composition of day‐respired CO2. This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure ci/ca effect) from respiratory effect (production of CO2 with a different δ13C value from that of net‐fixed CO2) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO2]. We show that whole mesocosm‐respired CO2 is slightly 13C depleted in the light at the mesocosm level (by 0.2–0.8‰), while it is slightly 13C enriched in darkness (by 1.5–3.2‰). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the 13C abundance in day‐ and night‐evolved CO2. We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO2 production may change, thereby explaining the different 12C/13C respiratory fractionations in the light and in the dark. 相似文献
45.
Colour change ability and its effect on prey capture success in female Misumenoides formosipes crab spiders 下载免费PDF全文
1. Changing between white and yellow body colour in certain crab spider species has been interpreted as an adaptation for matching the background colour where they hunt and thereby remaining cryptic to prey and/or their own predators. The potential costs and benefits of colour change in female Misumenoides formosipes Walckenaer were investigated via assessment of prey opportunities and capture success, in conjunction with the tendency for and rate of colour change on different backgrounds. 2. It was tested whether being matched or mismatched to their background affected foraging by moving females between white and yellow inflorescences. Female colour was quantified in digital photos using the Lab colour space component of Adobe photoshop , providing the first empirical assessment of the rate of colour change for a crab spider species. 3. Insect visits (potential prey) on inflorescences with and without spiders and prey capture success with females matched and mismatched to their background were quantified. 4. Yellow females abandoned white inflorescences, whereas white females remained on and underwent colour change on yellow inflorescences. This difference supported the notion that the costs of colour change differ depending on the starting colour. Female departures from white flowers were apparently not due to a lack of insect visitation, as white inflorescences had higher visitation rates than did yellow inflorescences, even in the presence of spiders. 5. An increase in the prey capture success of females who transitioned from white to yellow body colour on a yellow background supported the hypothesis that colour matching functions to deceive prey. 相似文献
46.
Cantaloupe (Cucumis melo L.) plants set groups of fruits whichgenerate large variations in the reproductive:vegetative dryweight balance. We studied the influence of fruit number onthe partitioning of dry matter and energy between the vegetativeand reproductive organs and among the seeds and the variousfruit tissues during the development of the first fruits. Over2 years and on two Charentais cantaloupe cultivars, fruit numberwas either limited to one or left unrestricted, which led tothe setting of two to six fruits. Because of the high lipidcontent in seeds, the distribution of assimilates was studiedin terms of energy equivalent as well as dry weight. Measureddry weights were converted into energy equivalents by calculatingthe construction cost of tissues from their elemental composition.Seeds differed from other tissues in showing an increase inconstruction cost, from 1.1 to 1.8 g CH2O g-1d. wt between 10and 30 d after pollination. For this reason, during the secondhalf of fruit development on plants with unrestricted fruitload, they made up to 31% of the fruit and 12% of the aerialpart of the whole plant in terms of dry weight, but 39 and 18%in terms of energy (glucose equivalents). The fraction of assimilatesallocated to the fruits showed a saturation-type response tothe number of fruits per plant. It did not increase in cultivarTalma above two fruits per plant, which could be due to a decreasingsink strength with fruit rank, whereas cultivar Galoubet maintaineda more homogeneous fruit size within plants. At a similar fruitload, the reproductive:vegetative dry weight balance differedbetween the 2 years of the experiment, probably because of variationin the fruit sink strength. Copyright 1999 Annals of BotanyCompany Charentais cantaloupe, Cucumis melo L., assimilate distribution, construction cost, development, dry matter partitioning, fruit load, seeds, sink strength. 相似文献
47.
JOHN R. ZAONARIVELO JULIE A. SOMMER GARY E. SHORE SUSIE M. MCGUIRE SHANNON E. ENGBERG RICK A. BRENNEMAN EDWARD E. LOUIS 《Molecular ecology resources》2007,7(1):25-28
Twenty novel polymorphic microsatellite loci were isolated and characterized from the Indri, Indri indri, genome. Along with sequence data, this marker suite will be used in future studies to establish population structure throughout its range and to verify the proposed subspecific nomenclature. Gene diversity (0.760 and 0.783) and allelic richness (5.8 and 6.43) were estimated in the Betampona and Andasibe populations, respectively. 相似文献
48.
Elevated atmospheric carbon dioxide (eCO2) has been shown to have a variety of ecosystem‐level effects in terrestrial systems, but few studies have examined how eCO2 might affect aquatic habitats. This limits broad generalizations about the effects of a changing climate across biomes. To broaden this generalization, we used free air CO2 enrichment to compare effects of eCO2 (i.e., double ambient ~720 ppm) relative to ambient CO2 (aCO2~360 ppm) on several ecosystem properties and functions in large, outdoor, experimental mesocosms that mimicked shallow sand‐bottom prairie streams. In general, we showed that eCO2 had strong bottom‐up effects on stream autotrophs, which moved through the food web and indirectly affected consumer trophic levels. These general effects were likely mediated by differential CO2 limitation between the eCO2 and aCO2 treatments. For example, we found that eCO2 decreased water‐column pH and increased dissolved CO2 in the mesocosms, reducing CO2‐limitation at times of intense primary production (PP). At these times, PP of benthic algae was about two times greater in the eCO2 treatment than aCO2 treatment. Elevated PP enhanced the rate of carbon assimilation relative to nutrient uptake, which reduced algae quality in the eCO2 treatment. We predicted that reduced algae quality would negatively affect benthic invertebrates. However, density, biomass and average individual size of benthic invertebrates increased in the eCO2 treatment relative to aCO2 treatment. This suggested that total PP was a more important regulator of secondary production than food quality in our experiment. This study broadens generalizations about ecosystem‐level effects of a changing climate by providing some of the first evidence that the global increase in atmospheric CO2 might affect autotrophs and consumers in small stream ecosystems throughout the southern Great Plains and Gulf Coastal slope of North America. 相似文献
49.
MARY C. FREEMAN DOLORS VIÑOLAS GARY D. GROSSMAN ADOLFO DE SOSTOA 《Freshwater Biology》1990,24(2):335-345
SUMMARY.
- 1 Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain, varied significantly among dates during a 19-month study. Most temporal variation, however, was attributable to changes in microhabitat availability.
- 2 B. fluviatilis demonstrated non-random use of available microhabitats during each sampling period, and generally occupied deeper microhabitats with higher average current velocities dominated by rubblegravel substrates.
- 3 B. fluviatilis also demonstrated non-random use of available nest sites; males generally nested under the largest available pieces of rubble, in areas with less gravel or sand. Water column depth influenced nest site use in two of four study areas.
- 4 We found few microhabitat differences between spawning and nonspawning periods, or between males and females. In addition, microhabitat use was similar among B. fluviatilis size-groups.
- 5 Although B. fluviatilis often were over-represented in deeper, erosional areas, blennies necessarily inhabited a wide range of microhabitats because average current velocities and water depths fluctuated greatly during the study. Tolerance of a broad range of environmental conditions may contribute to the species' persistence in habitats that exhibit extreme seasonal changes in discharge such as the Matarraña.
50.
MILLS EDWARD L.; ROSENBERG GARY; SPIDLE ADRIAN P.; LUDYANSKIY MICHAEL; PLIGIN YURI; MAY BERNIE 《Integrative and comparative biology》1996,36(3):271-286
SYNOPSIS. North America's Great Lakes have recently been invadedby two genetically and morphologically distinct species of Dreissena.The zebra mussel (Dreissena polymorpha) became established inLake St. Clair of the Laurentian Great Lakes in 1986 and spreadthroughout eastern North America. The second dreissenid, termedthe quagga mussel, has been identified as Dreissena bugensisAndrusov, 1897. The quagga occurs in the Dnieper River drainageof Ukraine and now in the lower Great Lakes of North America.In the Dnieper River, populations of D. polymorpha have beenlargely replaced by D. bugensis; anecdotal evidence indicatesthat similar trends may be occurring in the lower LaurentianGreat Lakes. Dreissena bugensis occurs as deep as 130 m in theGreat Lakes, but in Ukraine is known from only 028 m.Dreissena bugensis is more abundant than D. polymorpha in deeperwaters in Dneiper River reservoirs. The conclusion that NorthAmerican quagga mussels have a lower thermal maximum than zebramussels is not supported by observations made of populationsin Ukraine. In the Dnieper River drainage, quagga mussels areless tolerant of salinity than zebra mussels, yet both dreissenidshave acclimated to salinities higher than North American populations;eventual colonization into estuarine and coastal areas of NorthAmerica cannot be ignored. 相似文献