Effects of global climatic warming on the boreal forest

On the basis of the predictions of the global climatic warming induced by anthropogenic activities, as provided by climatologists, current state of knowledge regarding possible ecological consequences of the warming on the boreal biome was discussed. A 600 to 700 km northward advance of the biome along with the warming was predicted. Such a shift could take place for half a century or so, which would be an unprecedentedly fast rate of progression. This might cause a serious disorder in species composition of the biome, particularly in the boundary regions. As to the carbon sink or source issues, considerable uncertainties and knowledge gaps existed. Elevated temperature and CO₂ levels would stimulate photosynthesis to result in an increase of CO₂ uptake, while the temperature increase would promote decomposition of organic matter especially that stored in the soils to release CO₂ to the atmosphere. Behaviors of northern peat bogs, whereca. 700 Gt of organic matter was thought to be accumulated, would seriously affect the balance. However, overall ecosystematic carbon balance was yet to be fully studied. It was realized that multifunctional approaches needed to be developed so as to integrate pieces of various information into a holistic picture. Need for international collaboration research efforts was also addressed.     

气候变暖对麦蚜的影响

麦蚜是体型小、生活周期短的变温动物,对环境温度尤其是高温的变化十分敏感。气候变暖导致的温度升高是影响麦蚜最直接和最重要的因子。本文综述了国内外有关气候变暖对麦蚜影响的野外观测、预测模型及模拟试验的研究进展。气候变暖将导致麦蚜的主要分布和为害区向高纬度地区转移;气候变暖增加了生长季的有效积温,导致麦蚜始见期、迁飞期、盛虫期等物候发生期提前;温度升高提高了麦蚜的越冬存活率,使温带地区春夏季种群数量增加;处于不同营养级的物种对温度变化的敏感性不尽相同,气候变暖可能影响麦类作物-麦蚜-天敌昆虫多营养级系统的种间互作。麦蚜的耐热性较差,气候变暖导致的高温幅度增加、持续时间延长、夜间最低温升高、极端高温幅度和频率增加等典型特征对其有深刻影响。高温的幅度、持续时间对麦蚜的存活和繁殖有显著的抑制作用;夜间变暖导致麦蚜存活线性下降,进一步恶化了日间高温对蚜虫的不利影响;极端高温事件的幅度和频率影响麦蚜的种群增长参数,不同种类麦蚜对极端高温事件的非对称响应改变了麦蚜种间的相对适合度、时间和空间上的群落结构和物种间的相对优势度。麦蚜可通过爬行和跌落等行为来缓解气候变暖造成的高温胁迫,在研究气候变暖对麦蚜影响的同时,应充分考虑麦蚜对气候变暖的适应和缓冲能力。如何人工模拟气候变暖趋势下温度的变化模式,精巧设计试验反映气候变暖主要特征,开展接近自然界变化的温度模式对麦蚜的影响和麦蚜对环境改变的适应性响应研究,将是未来该领域的主要研究方向。     

Modelling effects of habitat fragmentation on the ability of trees to respond to climatic warming

The ability of trees to migrate in response to climatic warming was simulated under various conditions of habitat availability. The model uses Holocene tree migration rates to approximate maximum migration rates in a forested landscape. Habitat availability and local population size was varied systematically under two dispersal and colonization models. These dispersal models varied in the likelihood of long-distance dispersal events. The first model used a negative exponential function that severely limited the probability of long-distance dispersal. The results of this model indicate that migration rate could decline an order of magnitude where the habitat availability is reduced from 80 to 20% of the matrix. The second model, using an inverse power function, carried a higher probability of long-distance dispersal events. The results from this model predict relatively small declines in migration rates when habitat availability is reduced to 50% of the simulation matrix. Below 50% habitat availability, mean migration rate was similar to the negative exponential model. These results predict a failure of many trees to respond to future climatic change through range expansion.     

Impact of global warming on the distribution and survival of the gelada baboon: a modelling approach

The gelada baboon is a graminivorous primate whose ecology is unusually sensitive to ambient temperature. A systems model of the socio-ecology of the gelada is used to predict the impact of global warming on the species’ altitudinal distribution. The species’ lower altitudinal limit will rise by ≈ 500 m for every 2 °C increase in global mean temperature. A 7 °C rise in temperature would be sufficient to result in the species being confined to a small number of isolated mountain peaks, where its chances of survival will be greatly reduced. Changes in local climate are also likely to have significant effects on agricultural practice on the Ethiopian highlands, and this in turn is likely to have repercussions for the distribution patterns of the gelada by further constraining the habitat available to them.     

Impact of global warming on the tree species composition of boreal forests in Finland and effects on emissions of isoprenoids

This study aims to identify how climate change may influence total emissions of monoterpene and isoprene from boreal forest canopies. The whole of Finland is assumed to experience an annual mean temperature (T) increase of 4 °C and a precipitation increase of 10% by the year 2100. This will increase forest resources throughout the country. At the same time, the proportions of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) in southern Finland (60°≤ latitude < 65°N) will be reduced from the current 40–50% to less than 10–20%, with increased dominance of birches (Betula pendula and Betula pubescens). In northern Finland (65°≤ latitude < 70°N), the proportions of Norway spruce and Scots pine will be balanced at a level of about 40% as the result of an increase in Norway spruce from the current 21% to 37% and a concurrent reduction in Scots pine from 63% to 40%. The proportion of birches is predicted to increase from the current 17% to 23%, but these will become the dominant species only on the most fertile sites. Total mean emissions of monoterpene by Scots pine will be reduced by 80% in southern Finland, but will increase by 62% in the north. Emissions from Norway spruce canopies will increase by 4% in the south but by 428% in the north, while those from birch canopies will increase by about 300% and 113%, respectively. Overall emissions of monoterpene over the whole country amount to about 950 kg km^?2 y^?1 under current temperature conditions and will increase by 17% to 1100 kg km^?2 y^?1 with elevated temperature and precipitation, mainly because of an increase at northern latitudes. Under current conditions, emissions of isoprene follow the spatial distribution of spruce canopies (the only isoprene‐emitting tree species that forms forests in Finland) with four times higher emissions in the south than in the north. The elevated temperature and the changes in the areal distribution of Norway spruce will result in increases in isoprene emissions of about 37% in southern Finland and 435% in northern Finland. Annual mean isoprene emissions from Norway spruce canopies over the whole country will increase by about 60% up to the year 2100.     

Synergistic impacts of global warming on the resilience of coral reefs

Recent epizootics have removed important functional species from Caribbean coral reefs and left communities vulnerable to alternative attractors. Global warming will impact reefs further through two mechanisms. A chronic mechanism reduces coral calcification, which can result in depressed somatic growth. An acute mechanism, coral bleaching, causes extreme mortality when sea temperatures become anomalously high. We ask how these two mechanisms interact in driving future reef state (coral cover) and resilience (the probability of a reef remaining within a coral attractor). We find that acute mechanisms have the greatest impact overall, but the nature of the interaction with chronic stress depends on the metric considered. Chronic and acute stress act additively on reef state but form a strong synergy when influencing resilience by intensifying a regime shift. Chronic stress increases the size of the algal basin of attraction (at the expense of the coral basin), whereas coral bleaching pushes the system closer to the algal attractor. Resilience can change faster—and earlier—than a change in reef state. Therefore, we caution against basing management solely on measures of reef state because a loss of resilience can go unnoticed for many years and then become disproportionately more difficult to restore.     

Comparison of climatic effects on radial growth of evergreen broad-leaved trees at their northern distribution limit and co-dominating deciduous broad-leaved trees and evergreen conifers

Using dendrochronological techniques, this study examined whether tree-ring width of two evergreen broad-leaved species (Cleyera japonica, Eurya japonica) at their inland northern distribution limit in central Japan is more limited by low temperature compared with two co-dominating deciduous broad-leaved species (Fagus japonica, Magnolia hypoleuca) and two evergreen conifer species (Chamaecyparis obtusa, Abies firma), whose distribution limits are further north. The two deciduous broad-leaved species and the two evergreen conifers are tall tree species. Evergreen broad-leaved Cleyera japonica is a sub-canopy species and Eurya japonica is a small tree species. The tree-ring widths of four of the six species (except for Eurya japonica and Magnolia hypoleuca) correlated positively with the March temperature just before the start of the growth period. For deciduous broad-leaved Magnolia hypoleuca, the tree-ring width was correlated positively and negatively with July temperature and precipitation, respectively. However, the other deciduous broad-leaved Fagus japonica showed no such relationships. For the evergreen broad-leaved Cleyera japonica and evergreen conifers Chamaecyparis obtusa and Abies firma, tree-ring widths correlated positively with winter temperatures, probably because evergreen species can assimilate during warm winters. The tree-ring width of Cleyera japonica also correlated positively with temperatures of many months of the growth period. By contrast, the tree-ring width of the other evergreen broad-leaved Eurya japonica showed no positive correlation with the temperature in any month. Most Eurya japonica trees were suppressed by tall trees, which might disguise any climate effect. Thus, there were species differences in response to climate for each life form, and the tree-ring width of Cleyera japonica at the northern distribution limit was more limited by low temperatures compared with co-dominating species. It is suggested that growth of Cleyera japonica is increased by global warming at the latitudinal ecotone.     

Microbial diseases of corals and global warming

Coral bleaching and other diseases of corals have increased dramatically during the last few decades. As outbreaks of these diseases are highly correlated with increased sea-water temperature, one of the consequences of global warming will probably be mass destruction of coral reefs. The causative agent(s) of a few of these diseases have been reported: bleaching of Oculina patagonica by Vibrio shiloi; black band disease by a microbial consortium; sea-fan disease (aspergillosis) by Aspergillus sydowii; and coral white plague possibly by Sphingomonas sp. In addition, we have recently discovered that Vibrio coralyticus is the aetiological agent for bleaching the coral Pocillopora damicornis in the Red Sea. In the case of coral bleaching by V. shiloi, the major effect of increasing temperature is the expression of virulence genes by the pathogen. At high summer sea-water temperatures, V. shiloi produces an adhesin that allows it to adhere to a beta-galactoside-containing receptor in the coral mucus, penetrate into the coral epidermis, multiply intracellularly, differentiate into a viable-but-not-culturable (VBNC) state and produce toxins that inhibit photosynthesis and lyse the symbiotic zooxanthellae. In black band disease, sulphide is produced at the coral-microbial biofilm interface, which is probably responsible for tissue death. Reports of newly emerging coral diseases and the lack of epidemiological and biochemical information on the known diseases indicate that this will become a fertile area of research in the interface between microbial ecology and infectious disease.     

Predicted changes in the synchrony of larval emergence and budburst under climatic warming

Summary The impact of climatic warming on the synchrony of insect and plant phenologies was modelled in the case of winter moth (Operophtera brumata) and Sitka spruce (Picea sitchensis) in the Scottish uplands. The emergence of winter moth larvae was predicted with a thermal time requirement model and the budburst of Sitka spruce was predicted from a previously published model (Cannell and Smith 1983) based on winter chilling and thermal time. The date of emergence of winter moth larvae was predicted to occur earlier under climatic warming but the date of budburst of Sitka spruce was not greatly changed, resulting in decreased synchrony between larval emergence and budburst. The general question of how a change of climate might affect phenological synchrony and insect abundance is discussed.     

Olive phenology as a sensitive indicator of future climatic warming in the Mediterranean

Experimental and modelling work suggests a strong dependence of olive flowering date on spring temperatures. Since airborne pollen concentrations reflect the flowering phenology of olive populations within a radius of 50 km, they may be a sensitive regional indicator of climatic warming. We assessed this potential sensitivity with phenology models fitted to flowering dates inferred from maximum airborne pollen data. Of four models tested, a thermal time model gave the best fit for Montpellier, France, and was the most effective at the regional scale, providing reasonable predictions for 10 sites in the western Mediterranean. This model was forced with replicated future temperature simulations for the western Mediterranean from a coupled ocean‐atmosphere general circulation model (GCM). The GCM temperatures rose by 4·5 °C between 1990 and 2099 with a 1% per year increase in greenhouse gases, and modelled flowering date advanced at a rate of 6·2 d per °C. The results indicated that this long‐term regional trend in phenology might be statistically significant as early as 2030, but with marked spatial variation in magnitude, with the calculated flowering date between the 1990s and 2030s advancing by 3–23 d. Future monitoring of airborne olive pollen may therefore provide an early biological indicator of climatic warming in the Mediterranean.     

Implications of global warming for the climate of African rainforests

African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions.     

Effect of climatic warming on the Pacific walrus, and potential modification of its helminth fauna

The decreasing extent of sea-ice in the arctic basin as a consequence of climatic warming is modifying the behavior and diets of pagophilic pinnipeds, including the Pacific walrus, Odobenus rosmarus divergens Illiger, the species emphasized here. Mammals such as the walrus and bearded seal, Erignathus barbatus (Erxleben), cannot remain associated with the sea-ice, and continue to feed on their usual diet of benthic invertebrates inhabiting coastal waters to a depth of approximately 100 m, when the northwestward retreating ice reaches deep waters beyond the margins of the continental shelf. With reduction of their customary substrate (ice), the walrus has become more pelagic and preys more often on ringed seals, Phoca hispida Schreber. Dietary changes, with modifications of helminth faunas, may be induced by various factors. Increased consumption of mammals or their remains by walruses may lead to a higher prevalence of trichinellosis in them and to more frequent occurrence in indigenous peoples inhabiting the arctic coasts. To assess predicted effects on the composition of helminth fauna of the walrus, we recommend systematic surveys of their helminths as part of research on effects of climatic warming.     

Regional climatic warming drives long-term community changes of British marine fish

Climatic change has been implicated as the cause of abundance fluctuations in marine fish populations worldwide, but the effects on whole communities are poorly understood. We examined the effects of regional climatic change on two fish assemblages using independent datasets from inshore marine (English Channel, 1913-2002) and estuarine environments (Bristol Channel, 1981-2001). Our results show that climatic change has had dramatic effects on community composition. Each assemblage contained a subset of dominant species whose abundances were strongly linked to annual mean sea-surface temperature. Species' latitudinal ranges were not good predictors of species-level responses, however, and the same species did not show congruent trends between sites. This suggests that within a region, populations of the same species may respond differently to climatic change, possibly owing to additional local environmental determinants, interspecific ecological interactions and dispersal capacity. This will make species-level responses difficult to predict within geographically differentiated communities.     

Impact of future warming on winter chilling in Australia

Increases in temperature as a result of anthropogenically generated greenhouse gas (GHG) emissions are likely to impact key aspects of horticultural production. The potential effect of higher temperatures on fruit and nut trees’ ability to break winter dormancy, which requires exposure to winter chilling temperatures, was considered. Three chill models (the 0–7.2°C, Modified Utah, and Dynamic models) were used to investigate changes in chill accumulation at 13 sites across Australia according to localised temperature change related to 1, 2 and 3°C increases in global average temperatures. This methodology avoids reliance on outcomes of future GHG emission pathways, which vary and are likely to change. Regional impacts and rates of decline in chilling differ among the chill models, with the 0–7.2°C model indicating the greatest reduction and the Dynamic model the slowest rate of decline. Elevated and high latitude eastern Australian sites were the least affected while the three more maritime, less elevated Western Australian locations were shown to bear the greatest impact from future warming.     

Infra‐red thermometry of alpine landscapes challenges climatic warming projections

Rough mountain terrain offers climatic conditions (niches) to plants and animals poorly represented by conventional climate station data. However, the extent to which actual temperatures deviate from those of the freely circulating atmosphere had never been assessed at a landscape level. Here, we quantify thermal life conditions across topographically rich mountain terrain by using a combination of thermal (IR) imagery of surface temperature with data from a large number of miniature data loggers buried at 3 cm soil depth. The data obtained from six alpine (Alps) and arctic‐alpine slopes (Norway, Sweden, Svalbard) evidence persistent root zone temperatures of 2–4 K above air temperature during summer. Surface temperatures show strong positive (2–9 K) and negative (3–8 K) deviations from air temperature on bright days and clear nights, respectively. As to be expected, south oriented slopes are warmer than west and north slopes but microclimatic variation on clear sky days was strong within all slopes, with 8.4±2.5 K (mean±SD) surface temperature differences persisting over several hours per day along horizontal (i.e., equal elevation) transects. Life conditions of alpine organisms are thus strongly decoupled from conditions in the free atmosphere and cannot reliably be inferred from climate station data in both, temperate and arctic latitudes. Microtopography can mimic temperature differences of large elevational (or latitudinal) gradients over very short horizontal distances. This is important in the context of climate change because it shows that species do not necessarily need to climb several hundred meters in elevation to escape the warmth. Quite often, few meters of horizontal shift will do. For plants unable to, or too slow to adapt to a warmer climate, thermal microhabitat mosaics offer both refuge habitats as well as stepping stones as atmospheric temperatures rise.