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1.
Common gardens were established along a ~900 km latitudinal transect to examine factors limiting geographical distributions of boreal and temperate tree species in eastern North America. Boreal representatives were trembling aspen ( Populus tremuloides Michx.) and paper birch ( Betula papyrifera Marsh.), while temperate species were eastern cottonwood ( Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum ( Liquidambar styraciflua L.). The species were compared with respect to adjustments of leaf photosynthetic metabolism along the transect, with emphasis on temperature sensitivities of the maximum rate of ribulose bisphosphate (RuBP) carboxylation ( EV) and regeneration ( EJ). During leaf development, the average air temperature ( Tgrowth) differed between the coolest and warmest gardens by 12 °C. Evidence of photosynthetic thermal acclimation (metabolic shifts compensating for differences in Tgrowth) was generally lacking in all species. Namely, neither EV nor EJ was positively related to Tgrowth. Correspondingly, the optimum temperature ( Topt) of ambient photosynthesis ( Asat) did not vary significantly with Tgrowth. Modest variation in Topt was explained by the combination of EV plus the slope and curvature of the parabolic temperature response of mesophyll conductance ( gm). All in all, species differed little in photosynthetic responses to climate. Furthermore, the adaptive importance of photosynthetic thermal acclimation was overshadowed by gm's influence on Asat's temperature response. 相似文献
2.
Climate is an important factor limiting tree distributions and adaptation to different thermal environments may influence how tree populations respond to climate warming. Given the current rate of warming, it has been hypothesized that tree populations in warmer, more thermally stable climates may have limited capacity to respond physiologically to warming compared to populations from cooler, more seasonal climates. We determined in a controlled environment how several provenances of widely distributed Eucalyptus tereticornis and E. grandis adjusted their photosynthetic capacity to +3.5°C warming along their native distribution range (~16–38°S) and whether climate of seed origin of the provenances influenced their response to different growth temperatures. We also tested how temperature optima ( Topt) of photosynthesis and Jmax responded to higher growth temperatures. Our results showed increased photosynthesis rates at a standardized temperature with warming in temperate provenances, while rates in tropical provenances were reduced by about 40% compared to their temperate counterparts. Temperature optima of photosynthesis increased as provenances were exposed to warmer growth temperatures. Both species had ~30% reduced photosynthetic capacity in tropical and subtropical provenances related to reduced leaf nitrogen and leaf Rubisco content compared to temperate provenances. Tropical provenances operated closer to their thermal optimum and came within 3% of the Topt of Jmax during the daily temperature maxima. Hence, further warming may negatively affect C uptake and tree growth in warmer climates, whereas eucalypts in cooler climates may benefit from moderate warming. 相似文献
3.
Rising temperatures caused by climate change could negatively alter plant ecosystems if temperatures exceed optimal temperatures for carbon gain. Such changes may threaten temperature‐sensitive species, causing local extinctions and range migrations. This study examined the optimal temperature of net photosynthesis ( Topt) of two boreal and four temperate deciduous tree species grown in the field in northern Minnesota, United States under two contrasting temperature regimes. We hypothesized that Topt would be higher in temperate than co‐occurring boreal species, with temperate species exhibiting greater plasticity in Topt, resulting in better acclimation to elevated temperatures. The chamberless experiment, located at two sites in both open and understory conditions, continuously warmed plants and soils during three growing seasons. Results show a modest, but significant shift in Topt of 1.1 ± 0.21 °C on average for plants subjected to a mean 2.9 ± 0.01 °C warming during midday hours in summer, and shifts with warming were unrelated to species native ranges. The 1.1 °C shift in Topt with 2.9 °C warming might be interpreted as suggesting limited capacity to shift temperature response functions to better match changes in temperature. However, Topt of warmed plants was as well‐matched with prior midday temperatures as Topt of plants in the ambient treatment, and Topt in both treatments was at a level where realized photosynthesis was within 90–95% of maximum. These results suggest that seedlings of all species were close to optimizing photosynthetic temperature responses, and equally so in both temperature treatments. Our study suggests that temperate and boreal species have considerable capacity to match their photosynthetic temperature response functions to prevailing growing season temperatures that occur today and to those that will likely occur in the coming decades under climate change. 相似文献
4.
While interest in photosynthetic thermal acclimation has been stimulated by climate warming, comparing results across studies requires consistent terminology. We identify five types of photosynthetic adjustments in warming experiments: photosynthesis as measured at the high growth temperature, the growth temperature, and the thermal optimum; the photosynthetic thermal optimum; and leaf-level photosynthetic capacity. Adjustments of any one of these variables need not mean a concurrent adjustment in others, which may resolve apparently contradictory results in papers using different indicators of photosynthetic acclimation. We argue that photosynthetic thermal acclimation (i.e., that benefits a plant in its new growth environment) should include adjustments of both the photosynthetic thermal optimum ( T opt) and photosynthetic rates at the growth temperature ( A growth), a combination termed constructive adjustment. However, many species show reduced photosynthesis when grown at elevated temperatures, despite adjustment of some photosynthetic variables, a phenomenon we term detractive adjustment. An analysis of 70 studies on 103 species shows that adjustment of T opt and A growth are more common than adjustment of other photosynthetic variables, but only half of the data demonstrate constructive adjustment. No systematic differences in these patterns were found between different plant functional groups. We also discuss the importance of thermal acclimation of respiration for net photosynthesis measurements, as respiratory temperature acclimation can generate apparent acclimation of photosynthetic processes, even if photosynthesis is unaltered. We show that while dark respiration is often used to estimate light respiration, the ratio of light to dark respiration shifts in a non-predictable manner with a change in leaf temperature. 相似文献
5.
Despite its economic importance as a bioenergy crop and key role in riparian ecosystems, little is known about genetic diversity and adaptation of the eastern cottonwood ( Populus deltoides). Here, we report the first population genomics study for this species, conducted on a sample of 425 unrelated individuals collected in 13 states of the southeastern United States. The trees were genotyped by targeted resequencing of 18,153 genes and 23,835 intergenic regions, followed by the identification of single nucleotide polymorphisms (SNPs). This natural P. deltoides population showed low levels of subpopulation differentiation ( FST = 0.022–0.106), high genetic diversity (θ W = 0.00100, π = 0.00170), a large effective population size ( Ne ≈ 32,900), and low to moderate levels of linkage disequilibrium. Additionally, genomewide scans for selection (Tajima's D), subpopulation differentiation ( XTX), and environmental association analyses with eleven climate variables carried out with two different methods (LFMM and BAYENV2) identified genes putatively involved in local adaptation. Interestingly, many of these genes were also identified as adaptation candidates in another poplar species, Populus trichocarpa, indicating possible convergent evolution. This study constitutes the first assessment of genetic diversity and local adaptation in P. deltoides throughout the southern part of its range, information we expect to be of use to guide management and breeding strategies for this species in future, especially in the face of climate change. 相似文献
6.
Extreme climatic events, such as heat waves, cold snaps and drought spells, related to global climate change, have become more frequent and intense in recent years. Acclimation of plant physiological processes to changes in environmental conditions is a key component of plant adaptation to climate change. We assessed the temperature response of leaf photosynthetic parameters in wheat grown under contrasting water regimes and growth temperatures ( Tgrowth). Two independent experiments were conducted under controlled conditions. In Experiment 1, two wheat genotypes were subjected to well-watered or drought-stressed treatments; in Experiment 2, the two water regimes combined with high, medium and low Tgrowth were imposed on one genotype. Parameters of a biochemical C 3-photosynthesis model were estimated at six leaf temperatures for each factor combination. Photosynthesis acclimated more to drought than to Tgrowth. Drought affected photosynthesis by lowering its optimum temperature ( Topt) and the values at Topt of light-saturated net photosynthesis, stomatal conductance, mesophyll conductance, the maximum rate of electron transport ( Jmax) and the maximum rate of carboxylation by Rubisco ( Vcmax). Topt for Vcmax was up to 40°C under well-watered conditions but 24–34°C under drought. The decrease in photosynthesis under drought varied among Tgrowth but was similar between genotypes. The temperature response of photosynthetic quantum yield under drought was partly attributed to photorespiration but more to alternative electron transport. All these changes in biochemical parameters could not be fully explained by the changed leaf nitrogen content. Further model analysis showed that both diffusional and biochemical parameters of photosynthesis and their thermal sensitivity acclimate little to Tgrowth, but acclimate considerably to drought and the combination of drought and Tgrowth. The commonly used modelling approaches, which typically consider the response of diffusional parameters, but ignore acclimation responses of biochemical parameters to drought and Tgrowth, strongly overestimate leaf photosynthesis under variable temperature and drought. 相似文献
7.
Impacts of climate warming depend on the degree to which plants are constrained by adaptation to their climate‐of‐origin or exhibit broad climatic suitability. We grew cool‐origin, central and warm‐origin provenances of Eucalyptus tereticornis in an array of common temperature environments from 18 to 35.5°C to determine if this widely distributed tree species consists of geographically contrasting provenances with differentiated and narrow thermal niches, or if provenances share a common thermal niche. The temperature responses of photosynthesis, respiration, and growth were equivalent across the three provenances, reflecting a common thermal niche despite a 2,200 km geographic distance and 13°C difference in mean annual temperature at seed origin. The temperature dependence of growth was primarily mediated by changes in leaf area per unit plant mass, photosynthesis, and whole‐plant respiration. Thermal acclimation of leaf, stem, and root respiration moderated the increase in respiration with temperature, but acclimation was constrained at high temperatures. We conclude that this species consists of provenances that are not differentiated in their thermal responses, thus rejecting our hypothesis of adaptation to climate‐of‐origin and suggesting a shared thermal niche. In addition, growth declines with warming above the temperature optima were driven by reductions in whole‐plant leaf area and increased respiratory carbon losses. The impacts of climate warming will nonetheless vary across the geographic range of this and other such species, depending primarily on each provenance's climate position on the temperature response curves for photosynthesis, respiration, and growth. 相似文献
8.
Responses of foliar light-saturated net assimilation rate ( Amax), capacity for photosynthetic electron transport ( Jmax) and mitochondrial respiration rate ( Rd) to long-term canopy light and temperature environment were investigated in a temperate deciduous canopy composed of Populus tremula L. in the upper (17–28 m) and of Tilia cordata Mill. in the lower canopy layer (4–17 m). Climatic measurements indicated that seasonal average daily maximum air temperature ( Tmax) was 5·5 °C (range 0·7–10·5 °C) higher in the top than in the bottom of the canopy, and strong positive correlations were observed between Tmax and seasonal average integrated quantum flux density ( Qint), as well as between seasonal average daily mean temperature and Qint. Because of changes in leaf dry mass and nitrogen per unit area, Amax, Jmax, and Rd scaled positively with Qint in both species at a common leaf temperature ( T). According to Jmax versus T response curves and dark chlorophyll fluorescence transients, photosynthetic electron transport was less heat resistant in P. tremula with optimum temperature of Jmax, Topt, of 33·5 ± 0·6 °C than in T. cordata with Topt of 40·7 ± 0·6 °C. This difference was suggested to manifest evolutionary adaptation of photosynthetic electron transport to cooler environments in P. tremula, the range of which extends farther north than that in T. cordata. Possibly because of acclimation to long-term canopy temperature environment, Topt was positively related to Qint in P. tremula, foliage of which was also exposed to higher irradiances and temperatures, but not in T. cordata, in the canopy of which quantum flux densities and temperatures were lower, and gradients in the environmental factors less pronounced. Parallel to changes in Topt, the activation energy for photosynthetic electron transport decreased with increasing Qint in P. tremula, indicating that Jmax of leaves acclimated to colder environment was more responsive to T in lower temperatures than that of high T acclimated leaves. Similar alterations in the activation energy for mitochondrial respiration rate were also observed, indicating that acclimation to temperature of mitochondrial and chloroplastic electron transport proceeds in a co-ordinated manner, and possibly involves long-term changes in membrane fluidity properties. We conclude that, because of correlations between temperature and light, the shapes of Jmax versus T, and Rd versus T response curves vary within tree canopies, and this needs to be taken account in modelling whole canopy photosynthesis. 相似文献
9.
Ambient temperatures are major factors regulating the growth rates, yields, and geographical distribution of crop species. The cultivation of sesame (Sesamum indicum L.) is expanding with the rising demand in regions where it is not traditionally grown, and sub-optimal yields due to extremely low or high temperatures could occur. Currently literature lacks information on the temperature responses of sesame growth. An experiment was conducted to quantify the effects of different temperatures on vegetative growth and reproductive development of sesame, and to estimate its cardinal temperature limits (Topt; Tmin; Tmax). Plants were subjected to six different day/night temperature treatments of 40/32, 36/28, 32/24, 28/20, and 20/12 °C using walk-in growth chambers. Vegetative growth of sesame was sensitive to low temperatures (<?15 °C), but tolerant of high temperatures. The cardinal temperature limits of 15.7 °C (Tmin), 27.3 °C (Topt), and 44.6 °C (Tmax) were observed for rate of biomass accumulation. Sesame reached the flowering stage under moderate to high temperature conditions; however, reproductive yields progressively declined above 25 °C, and no seed yields were obtained beyond 33 °C. The estimated temperature limits could be employed to develop crop models for simulating management and adaptation strategies of sesame under current and future climate scenarios, and adaptation to regions where the crop is not currently grown. Future research should focus on understanding factors controlling the temperature tolerance of reproductive development in sesame, to provide a broader geographical adaptation. 相似文献
10.
Most plants show considerable capacity to adjust their photosynthetic characteristics to their growth temperatures (temperature acclimation). The most typical case is a shift in the optimum temperature for photosynthesis, which can maximize the photosynthetic rate at the growth temperature. These plastic adjustments can allow plants to photosynthesize more efficiently at their new growth temperatures. In this review article, we summarize the basic differences in photosynthetic reactions in C 3, C 4, and CAM plants. We review the current understanding of the temperature responses of C 3, C 4, and CAM photosynthesis, and then discuss the underlying physiological and biochemical mechanisms for temperature acclimation of photosynthesis in each photosynthetic type. Finally, we use the published data to evaluate the extent of photosynthetic temperature acclimation in higher plants, and analyze which plant groups (i.e., photosynthetic types and functional types) have a greater inherent ability for photosynthetic acclimation to temperature than others, since there have been reported interspecific variations in this ability. We found that the inherent ability for temperature acclimation of photosynthesis was different: (1) among C 3, C 4, and CAM species; and (2) among functional types within C 3 plants. C 3 plants generally had a greater ability for temperature acclimation of photosynthesis across a broad temperature range, CAM plants acclimated day and night photosynthetic process differentially to temperature, and C 4 plants was adapted to warm environments. Moreover, within C 3 species, evergreen woody plants and perennial herbaceous plants showed greater temperature homeostasis of photosynthesis (i.e., the photosynthetic rate at high-growth temperature divided by that at low-growth temperature was close to 1.0) than deciduous woody plants and annual herbaceous plants, indicating that photosynthetic acclimation would be particularly important in perennial, long-lived species that would experience a rise in growing season temperatures over their lifespan. Interestingly, across growth temperatures, the extent of temperature homeostasis of photosynthesis was maintained irrespective of the extent of the change in the optimum temperature for photosynthesis ( T opt), indicating that some plants achieve greater photosynthesis at the growth temperature by shifting T opt, whereas others can also achieve greater photosynthesis at the growth temperature by changing the shape of the photosynthesis–temperature curve without shifting T opt. It is considered that these differences in the inherent stability of temperature acclimation of photosynthesis would be reflected by differences in the limiting steps of photosynthetic rate. 相似文献
11.
Ectotherm thermal physiology is frequently used to predict species responses to changing climates, but for amphibians, water loss may be of equal or greater importance. Using physical models, we estimated the frequency of exceeding the thermal optimum ( Topt) or critical evaporative water loss (EWL crit) limits, with and without shade‐ or water‐seeking behaviours. Under current climatic conditions (2002–2012), we predict that harmful thermal (> Topt) and hydric (>EWL crit) conditions limit the activity of amphibians during ~70% of snow‐free days in sunny habitats. By the 2080s, we estimate that sunny and dry habitats will exceed one or both of these physiological limits during 95% of snow‐free days. Counterintuitively, we find that while wet environments eliminate the risk of critical EWL, they do not reduce the risk of exceeding Topt (+2% higher). Similarly, while shaded dry environments lower the risk of exceeding Topt, critical EWL limits are still exceeded during 63% of snow‐free days. Thus, no single environment that we evaluated can simultaneously reduce both physiological risks. When we forecast both temperature and EWL into the 2080s, both physiological thresholds are exceeded in all habitats during 48% of snow‐free days, suggesting that there may be limited opportunity for behaviour to ameliorate climate change. We conclude that temperature and water loss act synergistically, compounding the ecophysiological risk posed by climate change, as the combined effects are more severe than those predicted individually. Our results suggest that predictions of physiological risk posed by climate change that do not account for water loss in amphibians may be severely underestimated and that there may be limited scope for facultative behaviours to mediate rapidly changing environments. 相似文献
12.
Future climate change is expected to increase temperature ( T) and atmospheric vapour pressure deficit (VPD) in many regions, but the effect of persistent warming on plant stomatal behaviour is highly uncertain. We investigated the effect of experimental warming of 1.9–5.1 °C and increased VPD of 0.5–1.3 kPa on transpiration and stomatal conductance ( gs) of tree seedlings in the temperate forest understory (Duke Forest, North Carolina, USA). We observed peaked responses of transpiration to VPD in all seedlings, and the optimum VPD for transpiration ( Dopt) shifted proportionally with increasing chamber VPD. Warming increased mean water use of Carya by 140% and Quercus by 150%, but had no significant effect on water use of Acer. Increased water use of ring‐porous species was attributed to (1) higher air T and (2) stomatal acclimation to VPD resulting in higher gs and more sensitive stomata, and thereby less efficient water use. Stomatal acclimation maintained homeostasis of leaf T and carbon gain despite increased VPD, revealing that short‐term stomatal responses to VPD may not be representative of long‐term exposure. Acclimation responses differ from expectations of decreasing gs with increasing VPD and may necessitate revision of current models based on this assumption. 相似文献
13.
Identifying how close species live to their physiological thermal maxima is essential to understand historical warm‐edge elevational limits of montane faunas and forecast upslope shifts caused by future climate change. We used laboratory experiments to quantify the thermal tolerance and acclimation potential of four fishes ( Notropis leuciodus, N. rubricroceus, Etheostoma rufilineatum, E. chlorobranchium) that are endemic to the southern Appalachian Mountains (USA), exhibit different historical elevational limits, and represent the two most species‐rich families in the region. All‐subsets selection of linear regression models using AIC c indicated that species, acclimation temperature, collection location and month, and the interaction between species and acclimation temperature were important predictors of thermal maxima (T max), which ranged from 28.5 to 37.2°C. Next, we implemented water temperature models and stochastic weather generation to characterize the magnitude and frequency of extreme heat events (T extreme) under historical and future climate scenarios across 25 379 stream reaches in the upper Tennessee River system. Lastly, we used environmental niche models to compare warming tolerances (acclimation‐corrected T max minus T extreme) between historically occupied versus unoccupied reaches. Historical warming tolerances, ranging from +2.2 to +10.9°C, increased from low to high elevation and were positive for all species, suggesting that T max does not drive warm‐edge (low elevation) range limits. Future warming tolerances were lower (?1.2 to +9.3°C) but remained positive for all species under the direst warming scenario except for a small proportion of reaches historically occupied by E. rufilineatum, indicating that T max and acclimation potentials of southern Appalachian minnows and darters are adequate to survive future heat waves. We caution concluding that these species are invulnerable to 21st century warming because sublethal thermal physiology remains poorly understood. Integrating physiological sensitivity and warming exposure demonstrates a general and fine‐grained approach to assess climate change vulnerability for freshwater organisms across physiographically diverse riverscapes. 相似文献
14.
Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12‐week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima ( Topt) and apparent activation energy ( Ea), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59 °C. With a few exceptions, Topt and Ea of denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, Ea was somewhat lower for anammox compared to denitrification across all treatments. However, Topt did not differ between processes, and neither Ea nor Topt changed with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature responses, and these responses were not influenced by warming. This led us to reject the hypothesis that anammox is more cold‐adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification. 相似文献
15.
Preferred body temperatures ( T
sel) of ectotherms are important for ecological and evolutionary studies. In lizards, the measurement of T
sel is controversial for several reasons, generally related to hypotheses addressing how T
sel may evolve in the wild. Although seldom explicitly tested, evolutionary hypotheses of adaptation to local climate require
that T
sel meets the conditions of natural selection, which include repeatability, heritability and a link to fitness. Here, we investigated
repeatability ( τ, intra-class correlation coefficient) of T
sel at several time-scales using four Cordylid species from heterogeneous thermal habitats. Although there was significant inter-individual
variation within days ( P < 0.005 in most cases), there was no significant inter-individual variation when calculated across several days ( P > 0.05). Repeatability was low in all species investigated (from 0 to 0.482) when compared against other estimates of repeatability
of T
sel in the literature. Irrespective of how T
sel was calculated, it showed inconsistent and variable temporal effects across species. Furthermore, repeatability of T
sel did not change with acclimation to laboratory conditions. These data have implications for understanding the evolution of
thermoregulation in these and other ectotherms. 相似文献
16.
Widespread species often occur across a range of climatic conditions, through a combination of local genetic adaptations and phenotypic plasticity. Species with greater phenotypic plasticity are likely to be better positioned to cope with rapid anthropogenic climate changes, while those displaying strong local adaptations might benefit from translocations to assist the movement of adaptive genes as the climate changes. Eucalyptus tricarpa occurs across a climatic gradient in south‐eastern Australia, a region of increasing aridity, and we hypothesized that this species would display local adaptation to climate. We measured morphological and physiological traits reflecting climate responses in nine provenances from sites of 460 to 1040 mm annual rainfall, in their natural habitat and in common gardens near each end of the gradient. Local adaptation was evident in functional traits and differential growth rates in the common gardens. Some traits displayed complex combinations of plasticity and genetic divergence among provenances, including clinal variation in plasticity itself. Provenances from drier locations were more plastic in leaf thickness, whereas leaf size was more plastic in provenances from higher rainfall locations. Leaf density and stomatal physiology (as indicated by δ 13C and δ 18O) were highly and uniformly plastic. In addition to variation in mean trait values, genetic variation in trait plasticity may play a role in climate adaptation. 相似文献
17.
研究环境变化下的树木水分利用效率对探讨森林生态系统碳水耦联关系及其对气候变化的响应和适应对策具有重要意义。落叶松(Larix gmelinii)为我国北方森林的建群种之一。将水热条件不同的17个种源落叶松种植在帽儿山森林生态系统研究站的同质园内30年后, 测定其针叶水分利用效率(WUE)及其相关因子。结果表明: WUE、净光合速率(P n)、蒸腾速率(T r)、气孔导度(G s)、比叶面积(SLA)和叶片氮含量(N L)均存在显著的种源差异(p < 0.05)。WUE和G s呈显著指数相关关系, 当G s < 0.2 时WUE随G s的增大而明显增大, 而当G s > 0.2时WUE趋于稳定。WUE和SLA及N L分别呈线性负相关和正相关关系, 且随种源原地的干燥度指数(AI)的增大其相关性明显增强。WUE和种源原地年平均气温、平均年降水量及AI分别呈线性负相关、负相关和正相关关系, 并且相关系数依次增大; T r则仅和种源原地年平均气温呈线性正相关关系, 而P n和种源原地AI呈线性正相关关系。不同种源落叶松由于对种源原地环境条件的适应而存在针叶结构和生理特征的显著差异, 并因此引起针叶水分利用效率的差异。 相似文献
18.
A key aspect of successful restoration projects is the sourcing of propagation material suited to the environmental and biotic conditions of the proposed planting site. Traditionally, the use of propagules collected locally has been advocated for revegetation on the assumption that this material is better adapted to local conditions. A rapidly changing climate, however, is challenging the assumption that the use of local genetic stock will provide the best restoration outcome in the long term. We tested the ‘local is best’ paradigm using open top chambers to simulate the predicted summer temperatures for 2050 in western Sydney, Australia. We compared the establishment success of Eucalyptus tereticornis and Themeda australis, dominant species in Cumberland Plain Woodland, grown from local versus non‐local seed . All plants survived an exceptional summer heatwave and few differences between temperature treatments were found. No evidence of local superiority was found for survival or growth of non‐reproductive tissues of either species. However, local provenance plants of E. tereticornis suffered significantly greater herbivory in the ambient temperature treatment than one non‐local provenance, and local provenance plants of T. australis demonstrated significant superiority to most non‐local provenances in all categories of reproductive growth. For both species, the provenances from warmer climates demonstrated comparable, and often better, growth performance than the local provenance plants. 相似文献
19.
The influence of sub-optimal temperatures (T) on the microbial growth rate (μ) has been assessed by means of dimensionless
variables: T dim = [T−T min]/[T opt−T min] and μ dim = μ/μ opt. T min represents the temperature at which there is no growth, T opt the optimum temperature at which the growth rate, μ opt, is maximum. Data sets, growth rate vs temperature, have been taken from the literature for 12 organisms (psychrotrophs, mesophiles and thermophiles). In order
to compare these organisms, the power law function has been used: [μ dim] = [T dim] α. The parameters μ opt and T opt are determined from direct readings whereas T min and αare estimated by means of a non-linear regression. An accurate estimation of T min is obtained providing low growth rate data are available. A wide range of optimal temperatures where the growth rate almost
equals μ opt prevents one from obtaining a narrow confidence interval forα. On the basis of the analysis hereafter developed, thermophiles
are characterized by values of the power α less than mesophiles and psychrotrophs. Almost all of these values are significantly
different from two, previously determined for Staphylococcus xylosus and widely used for predicting the microbial growth in foods.
Received 15 May 1998/ Accepted in revised form 25 September 1998 相似文献
20.
Aim To identify the effect of climate change on selected plant species representative of the main vegetation types in the Faroe Islands. Due to a possible weakening of the North Atlantic Current, it is difficult to predict whether the climate in the Faroe Islands will be warmer or colder as a result of global warming. Therefore, two scenarios are proposed. The first scenario assumes an increase in summer and winter temperature of 2 °C, and the second a decrease in summer and winter temperature of 2 °C. Location Temperate, low alpine and alpine areas in the northern and central part of the Faroe Islands. Methods The responses of 12 different plant species in the Faroe Islands were tested against measured soil temperature, expressed as T min, T max, snow cover and growing degree days (GDD), using generalised linear modelling (GLM). Results The tolerance to changes in winter soil temperature (0.3–0.8 °C) was found to be lower than the tolerance to changing summer soil temperature (0.7–1.0 °C), and in both cases lower than the predicted climate changes. Conclusions The species most affected by a warming scenario are those that are found with a limited distribution restricted to the uppermost parts of the mountains, especially Salix herbacea, Racomitrium fasciculare, and Bistorta vivipara. For other species, the effect will mainly be a general upward migration. The most vulnerable species are those with a low tolerance, especially Calluna vulgaris, and also Empetrum nigrum, and Nardus stricta. If the climate in the Faroe Islands should become colder, the most vulnerable species are those at low altitudes. A significantly lower temperature would be expected to produce a serious reduction in the extent of Vaccinium myrtillus and Galium saxatilis. Species like Empetrum nigrum, Nardus stricta, and Calluna vulgaris may also be vulnerable. In any case, these species can be expected to migrate downwards. 相似文献
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