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1.
Abstract. Seedlings of Pinus radiata D. Don were grown in growth chambers for 22 weeks with two levels of phosphorus, under either well-watered or water-stressed conditions at CO2 concentrations of either 330 or 660mm3 dm?3. Plant growth, water use efficiency and conductance were measured and the relationship between these and needle photosynthetic capacity, water use efficiency and conductance was determined by gas exchange at week 22. Phosphorus deficiency decreased growth and foliar surface area at both CO2concentrations; however, it only reduced the maximum photosynthetic rates of the needles at 660 mm3 CO2 dm?3 (plants grown and measured at the same CO2 concentration). Water stress reduced growth and foliar surface area at both CO2 concentrations. Increases in needle photosynthetic rates appeared to be partly responsible for the increased growth at high CO2 where phosphorus was adequate. This effect was amplified by accompanying increases in needle production. Phosphorus deficiency inhibited these responses because it severely impaired needle photosynthetic function. The relative increase in growth in response to high CO2 was higher in the periodically water-stressed plants. This was not due to the maintenance of cell volume during drought. Plant water use efficiency was increased by CO2 enrichment due to an increase in dry weight rather than a decrease in shoot conductance and, therefore, transpirational water loss. Changes in needle conductance and water use efficiency in response to high CO2 were generally in the same direction as those at the whole plant level. If the atmospheric CO2 level reaches the predicted concentration of 660 mm3 dm?3 by the end of next Century, then the growth of P. radiata will only be increased in areas where phosphorus nutrition is adequate. Growth will be increased in drought-affected regions but total water use is unlikely to be reduced.  相似文献   
2.
Abstract Advanced selections (families 20010 and 20062) of P. radiata D. Don were exposed to either 340 or 660 μmol CO2 mol 1 for 2 years to establish if growth responses to high CO2 would persist during the development of woody tissues. The experiment was carried out in glasshouses and some of the trees at each CO2 concentration were subjected to phosphorus deficiency and to periodic drought. CO2 enrichment increased whole-plant dry matter production irrespective of water availability, but only when phosphorus supply was adequate. The greatest increase occurred during the exponential period of growth and appeared to be tied to increased rates of photosynthesis, which caused accelerated production of leaf area. The increase in whole-plant dry matter production was similar for both families; however, family 20010 partitioned larger amounts of dry weight to the trunks than family 20062. which favoured the roots and branches. Wood density was generally increased by elevated CO2 and for family 20010 this increase was due to thickening of the tracheid walls. Tracheid length was similar at both CO2 levels but differed between families. These results suggest that, as the atmospheric CO2 concentration rises, field-grown P. radiata should produce more dry weight at sites where phosphorus is not acutely deficient, even where drought limits growth; however, increases in wood production are likely only for genotypes which continue to partition at least the same proportion of dry weight to wood in the trunk.  相似文献   
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1. Recent increases in phytoplankton biomass and the recurrence of cyanobacterial blooms in western Lake Erie, concomitant with a shift from a community dominated by zebra mussels (Dreissena polymorpha) to one dominated by quagga mussels (D. bugensis), led us to test for differences in ammonia‐nitrogen and phosphate‐phosphorus excretion rates of these two species of invasive molluscs. 2. We found significant differences in excretion rate both between size classes within a taxon and between taxa, with zebra mussels generally having greater nutrient excretion rates than quagga mussels. Combining measured excretion rates with measurements of mussel soft‐tissue dry weight and shell length, we developed nutrient excretion equations allowing estimation of nutrient excretion by dreissenids. 3. Comparing dreissenid ammonia and phosphate excretion with that of the crustacean zooplankton, we demonstrated that the mussels add to nitrogen and phosphorus remineralisation, shortening nitrogen and phosphorus turnover times, and, importantly, modify the nitrogen and phosphorus cycles in Lake Erie. The increased nutrient flux from dreissenids may facilitate phytoplankton growth and cyanobacterial blooms in well‐mixed and/or shallow areas of western Lake Erie.  相似文献   
5.
Zones of contact between divergent biological forms within or between species are critical to the study of speciation. How characters flow across contact zones can be informative of the speciation process. To better understand this phenomenon in a mammal, we investigated cranial shape change in a contact zone between northern and southern phylogeographical groups of California voles (Microtus californicus). We took 12 linear measurements of skulls, one measurement of the mandible, and coded the presence and absence of two skull foramina for 427 specimens. In multivariate analyses, skulls within parental regions were correctly assigned more than 90% of the time. In the contact zone, 49% were classified as northern and 51% as southern, with a bimodal distribution of posterior probability values. Foraminal patterns in the contact zone were intermediate between northern and southern regions. A cline analysis for coastal populations suggested a similar centre for mitochondrial and nuclear markers, although a centre for the morphological data was offset. Cranial morphology indicates an intermediate area with overlap between the two regions, as suggested by the molecular data, with a pattern distinct from mitochondrial DNA or nuclear DNA markers. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 264–283.  相似文献   
6.
Abstract: We developed models for simultaneous inference on movement and harvest rates, and of factors influencing harvest rates, using band-recovery data and Markov chain Monte Carlo (MCMC) modeling. We modeled variation in harvest rates for American black ducks (Anas rubripes) during 1971–1994 using recoveries of ducks banded in 3 breeding regions and recovered in 6 harvest regions in Canada and the United States. Models based on season length or bag limit together with season length, and incorporating a random year- and area-specific effect, were superior to other models as gauged by information criteria, fit statistics, and cross-validation. We used these models to generate posterior predictive distributions for harvest rates as a function of harvest regulations, for application to adaptive harvest management.  相似文献   
7.
The response of Eucalyptus grandis seedlings to elevated atmospheric CO2 concentrations was examined by growing seedlings at either 340 or 660 n mol CO2 mol-1 for 6 weeks. Graded increments of phosphorus and nitrogen fertilizers were added to a soil deficient in these nutrients to establish if the growth response to increasing nutrient availability was affected by CO2 concentration. At 660 μmol CO2 mol-1, seedling dry weight was up to five times greater than at 340 μmol CO2 mol-1. The absolute response was largest when both nitrogen and phosphorus availability was high but the relative increase in dry weight was greatest at low phosphorus availability. At 340 μmol CO2 mol-1 and high nitrogen availability, growth was stimulated by addition of phosphorus up to 76 mg kg 1 soil. Further additions of phosphorus had little effect. However, at 660 μmol CO2 mol-1, growth only began to plateau at a phosphorus addition rate of 920mg kg-1 soil. At 340 μmol CO2 mol-1 and high phosphorus availability, increasing nitrogen from 40 to 160mg kg-1 soil had little effect on plant growth. At high CO2, growth reached a maximum at between 80 and 160mg nitrogen kg-1 soil. Total uptake of phosphorus was greater at high CO2 concentration at all fertilizer addition rates, but nitrogen uptake was either lower or unchanged at high CO2 concentration except at the highest nitrogen fertilizer rate. The shoot to root ratio was increased by CO2 enrichment, primarily because the specific leaf weight was greater. The nitrogen and phosphorus concentration in the foliage was lower at elevated CO2 concentration partly because of the higher specific leaf weight. These results indicate that critical foliar concentrations currently used to define nutritional status and fertilizer management may need to be reassessed as the atmospheric CO2 concentration rises.  相似文献   
8.
To investigate if Eucalyptus species have responded to industrial-age climate change, and how they may respond to a future climate, we measured growth and physiology of fast- ( E. saligna ) and slow-growing ( E. sideroxylon ) seedlings exposed to preindustrial (290), current (400) or projected (650 μL L−1) CO2 concentration ([CO2]) and to current or projected (current +4 °C) temperature. To evaluate maximum potential treatment responses, plants were grown with nonlimiting soil moisture. We found that: (1) E. sideroxylon responded more strongly to elevated [CO2] than to elevated temperature, while E. saligna responded similarly to elevated [CO2] and elevated temperature; (2) the transition from preindustrial to current [CO2] did not enhance eucalypt plant growth under ambient temperature, despite enhancing photosynthesis; (3) the transition from current to future [CO2] stimulated both photosynthesis and growth of eucalypts, independent of temperature; and (4) warming enhanced eucalypt growth, independent of future [CO2], despite not affecting photosynthesis. These results suggest large potential carbon sequestration by eucalypts in a future world, and highlight the need to evaluate how future water availability may affect such responses.  相似文献   
9.
The so-called 'mimic octopuses' of tropical Indonesia are reputed to mimic up to 13 species of other local marine organisms. We tested for mimicry by allowing individuals of two species of octopus to habituate to divers, then observing and filming two species continuously as they foraged daily in the same open, featureless volcanic sand habitat. Mimicry of a local, abundant flounder occurred commonly during 5 days of natural foraging: nearly 500 episodes were analysed. Both octopus species mimicked the shape, swimming actions, speed, duration, and sometimes the coloration of swimming flounders. During flounder mimicry, octopuses were actively moving and conspicuous, whereas immediately before and after flounder mimicry, they were camouflaged and motionless (sitting or very slowly crawling). Furthermore, when motionless, octopuses assumed body patterns and postures that resembled small sponges, tube-worm tubes, or colonial tunicates, which were among the few objects in the open sand habitat. The key finding was that octopuses used flounder mimicry only when their movement would give away camouflage in this open habitat. In all cases, octopuses used mimicry as a primary defense. Several interactions with fishes and stomatopods were filmed and typical secondary defense behaviours, not mimicry, were used by the octopuses. Foraging occurred twice per day and two tactile feeding tactics were used. Dens and food were not limiting; thus, we observed a highly unusual circumstance of a guild of small, long-armed octopus species that shared the same habitat, den sources, food, activity period, and some behaviours.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 23–38.  相似文献   
10.
The unabated rise in atmospheric [CO2] is associated with increased air temperature. Yet, few CO2‐enrichment studies have considered pre‐industrial [CO2] or warming. Consequently, we quantified the interactive effects of growth [CO2] and temperature on photosynthesis of faster‐growing Eucalyptus saligna and slower‐growing E. sideroxylon. Well‐watered and ‐fertilized tree seedlings were grown in a glasshouse at three atmospheric [CO2] (290, 400, and 650 µL L?1), and ambient (26/18 °C, day/night) and high (ambient + 4 °C) air temperature. Despite differences in growth rate, both eucalypts responded similarly to [CO2] and temperature treatments with few interactive effects. Light‐saturated photosynthesis (Asat) and light‐ and [CO2]‐saturated photosynthesis (Amax) increased by ~50% and ~10%, respectively, with each step‐increase in growth [CO2], underpinned by a corresponding 6–11% up‐regulation of maximal electron transport rate (Jmax). Maximal carboxylation rate (Vcmax) was not affected by growth [CO2]. Thermal photosynthetic acclimation occurred such that Asat and Amax were similar in ambient‐ and high‐temperature‐grown plants. At high temperature, the thermal optimum of Asat increased by 2–7 °C across [CO2] treatments. These results are the first to suggest that photosynthesis of well‐watered and ‐fertilized eucalypt seedlings will remain strongly responsive to increasing atmospheric [CO2] in a future, warmer climate.  相似文献   
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