Anticipated Climate Change Scenarios Research Articles

Sap Flow Responses of the Endangered Species Juniperus drupacea Labill. to Environmental Variables in Parnon Mountain, Greece

In the face of ongoing climatic changes, understanding the species’ sap flow responses is of crucial importance for adaptation and resilience of ecosystems. This study investigated diurnal variability and radial sap flux density (Js) in a natural Juniperus drupacea forest on Mt Parnon and determined the climatic factors affecting its total sap flow (Qs). Between July 2021 and March 2022, Granier-type sensors and automatic weather stations monitored Js of J. drupacea trees and environmental factors. Utilizing a multi-point sensor for Js radial profile variability, correction factors were applied to calculate (Qs), ranging from 4.78 to 16.18 L day−1. In drier months of the study period (July–September), Qs progressively increased with increasing PAR and soil temperature, reaching a plateau at maximum values (app. 600 µmol m−2 s−1 and 26 °C respectively) indicating partial stomatal closure. Whereas, during the wetter period (October–March), when water was no longer a limiting factor, VPD and PAR emerged as significant controllers of stand transpiration. In this period, Qs responded positively to increasing soil water content (θ) only on days with high VPD (>0.5 kPa). The studied J. drupacea stand demonstrated adaptability to varying environmental conditions, crucial for the species’ survival, considering anticipated climate change scenarios.

Refining the Occurrence of Viral Encephalopathy and Retinopathy, Photobacteriosis, and Vibriosis in Connection with Seawater Physicochemical Parameters: A Five-Year Case Study

The marine environment and its physicochemical parameters play a pivotal role in the context of fish farming. Fundamental physicochemical factors of water, including temperature (T°C), salinity (S psu), dissolved oxygen (D.O. mg/l), and pH, exert a profound influence on the physiology of farmed aquatic animals and the composition of microbial communities. This study aimed to establish correlations between documented disease occurrences in sea bass intensive rearing and the prevailing physicochemical parameters of water. The objective was to analyse the significance of these parameters in disease outbreaks and develop a predictive model for the outbreak risk of key diseases. To this end, real-time physicochemical data were collected daily over five years (2011-2015) from two fish farms (A and B) located in the Gulf of Argostoli, island of Cephalonia, Western Greece. The focus was on incidences of Viral Encephalopathy and Retinopathy (VER), Photobacteriosis caused by Photobacterium damselae subsp. piscicida (PHDP) and Vibriosis caused by Vibrio anguillarum serotype O1 (VAO1). Statistically significant correlations were found between increasing water temperature and salinity and the occurrence of VER, PHDP, and VAO1 diseases. The reduction of dissolved oxygen, when combined with other parameters, synergistically triggered the manifestation of these three diseases. The study’s findings were discussed within the context of their potential to predict disease outbreaks based on fluctuations in the physicochemical parameters of water and anticipated climate change scenarios.

Niche overlap between the endemic Albizia lathamii and the invasive Prosopis juliflora in response to changing climate: insights from a protected area in Western Ghats, India

ABSTRACT Forest management must consider how organisms respond to climate change wildly when invasive and vulnerable species coexist in the same region. Albizia lathamii (AL), a threatened legume endemic to southern India, is being conserved in Chinnar Wildlife Sanctuary (CWS), a protected area (PA) in the Western Ghats. Prosopis juliflora (PJ), a dangerous intruder that seriously harms the environment has grown significantly in the PA over the past 10 years. This study attempted to comprehend the current distribution overlap of both species and to simulate their future distribution inside PA under the anticipated climate change scenarios. Overall, 103 standing positions of PJ and 69 of little-known AL were recorded and rarefied to 14 (seven PJ and seven AL) by a distance of 1-km resolution. Using the maximum entropy species distribution model, we estimated the future distribution overlap of both species for the years 2050 and 2070. The results reveal a sizable overlap between the two species in their future distribution. The “Suitable for AL-only” class exhibits a reduction in the area (by 44%) when projected to future scenarios. This indicates that AL’s natural habitat in the CWS-PA is at risk due to the invasiveness of the plant PJ and climate change. To conserve endemic and vulnerable plants, it is crucial to comprehend the distributional overlaps between the two species and design effective management strategies.

Gadolinium accumulation and its biochemical effects in Mytilus galloprovincialis under a scenario of global warming

Electrical and electronic equipment reaching the end of its useful life is currently being disposed of at such an alarmingly high pace that raises environmental concerns. Together with other potentially dangerous compounds, electronic waste contains the rare-earth element gadolinium (Gd), which has already been reported in aquatic systems. Additionally, the vulnerability of aquatic species to this element may also be modified when climate change related factors, like increase in temperature, are taken into consideration. Thus, the present study aimed to evaluate the toxicity of Gd under a scenario of increased temperature in Mytilus galloprovincialis mussels. A multi-biomarker approach and Gd bioaccumulation were assessed in mussels exposed for 28 days to 0 and 10 μg/L of Gd at two temperatures (control – 17 °C; increased – 22 °C). Results confirmed that temperature had a strong influence on the bioaccumulation of Gd. Moreover, mussels exposed to Gd alone reduced their metabolism, possibly to prevent further accumulation, and despite catalase and glutathione S-transferases were activated, cellular damage seen as increased lipid peroxidation was not avoided. Under enhanced temperature, cellular damage in Gd-exposed mussels was even greater, as defense mechanisms were not activated, possibly due to heat stress. In fact, with increased temperature alone, organisms experienced a general metabolic depression, particularly evidenced in defense enzymes, similar to the results obtained under Gd-exposure. Overall, this study underlines the importance of conducting environmental risk assessment taking into consideration anticipated climate change scenarios and exposures to emerging contaminants at relevant environmental concentrations.

A comparison of mesophotic and shallow sponge holobionts resilience to predicted future temperature elevation

Climate change is predicted to have detrimental impacts on sessile invertebrates, including sponges. Mesophotic ecosystems have been suggested to play a major role as refugia for coral reef sponge species, however knowledge regarding the ability of mesophotic sponges to cope with thermal stress is scarce. In this study we compared the response of the sponge Diacarnus erythraeanus, a widespread Red Sea sponge, from the shallow and mesophotic reef, to moderate and acute temperature elevation (2°C and 6°C, respectively) for short and long term periods (two and 35 days, respectively) by measuring physiological parameters (respiration, oxygen removal, pumping rates, and photosynthetic efficiency), and the microbiome composition change. The results indicated that mesophotic and shallow populations of D. erythraeanus are highly tolerant to both moderate and acute heat stress, demonstrating a high survival rate (100%) across the experimental treatments, with no visible signs of bleaching or necrosis. Exposure to heat stress resulted in significant alterations in the physiological parameters of sponges, including higher respiration rate and lower photosynthetic efficiency. These alterations were accompanied by correspondingly significant microbial adjustments, thus emphasizing the essential role of the microbiome in the host’s ability to persist when facing essential environmental stress. Moreover, while shallow and mesophotic sponges showed similar physiological tolerance to heat stress, their microbial response differed: while the microbiome diversity of the mesophotic sponges remained stable throughout the experiment, the shallow one significantly changed. This result suggests that their underlying coping mechanisms might differ between mesophotic and shallow populations. Since the associated-microbiome is largely regulated by the sponge-host genetics, difference in microbial adjustments to stress between populations, could indicate genetic variability between hosts. Therefore, while the results of this study support the hypothesis that mesophotic coral reefs could serve as thermal refugia for some sponge species, it raises the question regarding the validity of MCEs as a refuge for shallow populations. Finally, it emphasizes the crucial need to elucidate the underlying mechanisms governing the sponge-microbiome interactions, specifically in the context of the anticipated climate change scenarios.

Animal conflicts escalate in a warmer world

The potential for climate change to affect animal behaviour is widely recognized, yet its possible consequences on aggressiveness are still unclear. If warming and drought limit the availability of food resources, climate change may elicit an increase of intraspecific conflicts stemming from resource competition. By measuring aggressivity indices in a group-living, herbivorous mammal (the Apennine chamois Rupicapra pyrenaica ornata) in two sites differing in habitat quality, and coupling them with estimates of plant productivity, we investigated whether harsh climatic conditions accumulated during the growing season influenced agonistic contests at feeding via vegetation-mediated effects, and their interaction with the site-specific habitat quality. We focused on females, which exhibit intra-group contest competition to access nutritious food patches. Accounting for confounding variables, we found that (1) the aggression rate between foraging individuals increased with the warming accumulated over previous weeks; (2) the probability to deliver more aggressive behaviour patterns toward contestants increased with decreasing rainfall recorded in previous weeks; (3) the effects of cumulative warming and drought on aggressivity indices occurred at time windows spanning 15–30 days, matching those found on vegetation productivity; (4) the effects of unfavourable climatic conditions via vegetation growth on aggressivity were independent of the site-specific habitat quality. Simulations conducted on our model species predict a ~50 % increase in aggression rate following the warming projected over the next 60 years. Where primary productivity will be impacted by warming and drought, our findings suggest that the anticipated climate change scenarios may trigger bottom-up consequences on intraspecific animal conflicts. This study opens the doors for a better understanding of the multifactorial origin of aggression in group-living foragers, emphasising how the escalation of agonistic contests could emerge as a novel response of animal societies to ongoing global warming.

Distinct contributions of drought avoidance and drought tolerance to yield improvement in dryland wheat cropping

AbstractCrop avoidance and tolerance strategies are critical adaptive mechanisms of drought stress and play different roles in grain yield. However, little is known about the contribution of these two mechanisms to grain yield in old and modern wheat genotypes. Here, pot and field experiments were carried out to characterize and compare the mechanisms of drought avoidance and drought tolerance, and determine their differential contributions to the yield in six wheat genotypes. The pot experiment results demonstrated that the old genotypes acquired a better avoidance ability to adapt to drought stress. These avoidance abilities include larger root systems, lower leaf areas, low stomatal conductance, pale green leaf colour, higher degrees of leaf rolling and leaf waxiness. The modern genotypes displayed stronger drought tolerance advantages, such as high osmotic adjustment and antioxidant enzyme activity, and a smaller root system. Our field experiment further showed that under severe water‐deficit conditions, the old genotypes with stronger drought avoidance traits had higher yields and water use efficiency (WUEg), whereas the modern genotypes with strong drought tolerance characteristics produced higher yields and had higher WUEg under mild and intermediate water deficits. The results indicate that the relative contribution of drought tolerance and drought avoidance to grain yield depends to a large extent on the degree of drought stress and genotypes. Understanding the differential plant response depending on genotype and drought stress may help plant breeders develop drought‐resistant varieties suitable for drought‐prone environments under anticipated climate change scenarios.

Effect of Different Climate Change Variables on the Ecology and Management of Sesbania cannabina through Glyphosate.

An elevated atmospheric carbon dioxide (CO2) concentration and frequent droughts are two anticipated climate change scenarios in which certain invasive weeds may develop competitive advantages over crops and adversely impact productivity and herbicide efficacy. Hence, a study was conducted to explore the effect of different climatic scenarios on the growth and management of Sesbania cannabina (Retz.) Pers with glyphosate. The variables investigated were two CO2 concentrations (400 and 700 ppm), two soil moisture levels (100% and 50% of field capacity (FC)), and three glyphosate rates (0 (control), 517 (50% of recommended rate), and 1034 g ae ha−1 (recommended rate)). CO2 concentrations and soil moisture levels had different effects on the growth and management of S. cannabina. Overall, 100% FC and elevated [CO2] of 700 ppm recorded the maximum plant height (38 cm), leaves per plant (20), growth index (60), chlorophyll content (SPAD value 37), and dry biomass (3 g) in comparison with ambient [CO2] of 400 ppm and 50% FC treatment. The recommended glyphosate application gave 100% weed biomass reduction; however, efficacy was reduced (63%) when applied at 50% of the recommended rate under elevated [CO2] of 700 ppm and 50% FC conditions.

Assessment of hydrological response in Subarnarekha river basin under anticipated climate change scenarios

<p>Two hydrological climate modelling techniques, general circulation model (GCM) and hypothetical climate change scenarios, were used to analyse the hydrological response to the anticipated climate change scenarios in the Subarnarekha river basin in Eastern India. Both models verified individually for the same river basin and a comparative performance of the models was evaluated to relate the two models for the near (2014-2040) period climate. The hydrological response under the anticipated climate change in the Subarnarekha river basin is well assessed by GCM under the RCP 8.5 scenarios compared to the RCPs 4.5. Results indicate GCM best suited over the hypothetical climate change scenarios as GCM has demonstrated their potential in accurately reproducing the past observed climatic changes. The strong performance of the hypothetical climate change scenarios model, particularly for warming climate scenarios, suggests that it may have distinct advantages for the analysis of water balance components in the river basin. The monthly streamflows of Subarnarekha river basin was simulated using a total of 14 years (2000-2013) daily observed streamflow data in the ArcSWAT model integrated with model calibration and uncertainty analysis by means of SUFI-2 algorithm. The results indicate during the calibration the coefficient of determination (R2) and Nash-Sutcliff Efficiency (NSE) were reported as 0.98 and 0.97, respectively, while during the validation the R2 and NSE were obtained as 0.94 and 0.94, respectively, confirms the hydrological model performance was very good both in calibration and validation. The obtained climate change water impact index (ICCWI) values reveal the Subarnarekha river basin is more responsive to climate change. The reduction in precipitation along with the significant warming under the projected future climate is likely to reduce availability of water substantially in the study region. This work would be useful for the effective management of water resources for sustainable agriculture and in mitigating natural hazards such as droughts and floods in the study region.</p>

Key biological responses over two generations of the sea urchin Echinometra sp. A under future ocean conditions

Few studies have investigated the effects of ocean warming and acidification on marine benthic organisms over ecologically relevant time scales. We used an environmentally controlled coral reef mesocosm system to assess growth and physiological responses of the sea urchin species Echinometra sp. A over 2 generations. Each mesocosm was controlled for temperature and pCO2 over 29 mo under 3 climate change scenarios (present day and predicted states in 2050 and 2100 under RCP 8.5). The system maintained treatment conditions including annual temperature cycles and a daily variation in pCO2. Over 20 mo, adult Echinometra exhibited no significant difference in size and weight among the treatments. Growth rates and respiration rates did not differ significantly among treatments. Urchins from the 2100 treatment had elevated ammonium excretion rates and reduced O2:N ratios, suggesting a change in catabolism. We detected no difference in spawning index scores or oocyte size after 20 mo in the treatments, suggesting that gonad development was not impaired by variations in pCO2 and temperature reflecting anticipated climate change scenarios. Larvae produced from experimentally exposed adults were successfully settled from all treatments and raised for 5 mo inside the mesocosm. The final size of these juveniles exhibited no significant difference among treatments. Overall, we demonstrated that the mesocosm system provided a near natural environment for this urchin species. Climate change and ocean acidification did not affect the benthic life stages investigated here. Importantly, in previous short-term (weeks to months) experiments, this species exhibited reductions in growth and gonad development, highlighting the potential for short-term experiments with non-acclimated animals to yield contrasting, possibly erroneous results.

Viability of the critically endangered African wild ass (Equus africanus) population on Messir Plateau (Eritrea)

Globally, the African wild ass (Equus africanus) is at risk of extinction in the wild. Major threats to its survival are hunting, competition with livestock, and interbreeding with the domestic donkey. An important but rare population exists on the Messir Plateau in the Danakil ecosystem of Eritrea. Long-term data on reproduction and survival rate of African wild asses are limited, making it difficult to predict the population trend. Therefore, we assessed the population's potential viability given certain assumptions. An age-structured matrix model was used to project the population growth rate generated by assumed vital rates. The probability of population persistence over 50 years was estimated allowing for stochastic dynamics, density dependence, influences of rainfall on carrying capacity, and episodic disturbances reducing survival rates. Scenarios used either historical rainfall patterns or potential future rainfall with the same or amplified coefficient of variation. We contrasted two estimates of carrying capacity based either on recent population assessments, or on the potential capacity of the study site. Our models also compared realistic versus optimistic scenarios for age at first reproduction and potential longevity. The probability of persistence of a population of 18 females was reduced to < 50% in the worst-case scenario. With a potential carrying capacity of 37 females, persistence was projected to be almost 100% under all scenarios. The greatest threat to population viability seems to come from livestock impacts on the resources that limit the African wild ass population size under anticipated climate change scenarios. Further studies are required to assess the level of competition between African wild asses and livestock to guide effective conservation strategies

Towards sustainable protection of public health: The role of an urban wetland as a frontline safeguard of pathogen and antibiotic resistance spread

Wetlands are known for providing important ecosystem services, such as reduction of eutrophication. However, less research has focused on public health service of wetlands: their ability to protect microbial quality of water for downstream while they attract wildlife populations. For urban surface water, transmission of antibiotic resistance is also an important concern. Under anticipated climate change scenarios, more extreme precipitation patterns are emerging. Thus, runoff and flooding from increased precipitation will impair surface water quality more significantly. The objectives of this study were to 1) evaluate the dynamics of bacteria of public health concern in urban wetlands, including: Escherichia coli, Campylobacter, Shiga toxin-producing Escherichia coli (STEC), Arcobacter, and two antibiotic resistance genes (sulfonamide, sul1 and tetracycline, tetQ); and 2) identify the major fecal contamination sources using microbial source tracking (MST). Water samples were collected across the urban wetlands in central Ohio from June 2013 to June 2014 and tested with a culture-based (E. coli) and quantitative PCR (the rest) methods. Since Canada geese were the most observed wildlife at the study sites and they are known to carry an array of infectious disease agents, their fecal samples were also collected. From the water samples, E. coli (fecal indicator) had the highest occurrence in 99.2% of the total samples, followed by sul1 (98.3%), Arcobacter (94.9%), STEC (74.6%), tetQ (58.5%), and Campylobacter (1.7%). Overall reduction in E. coli was 22.3% across the wetlands, but variation was observed depending on the season. Microbial source tracking suggested a high prevalence of avian- (44.9%) and ruminant- (38.1%) originated fecal contaminations (e.g., Canada geese and deer). From the geese fecal samples, STEC (93.2%) and Arcobacter (4.5%) were detected, which could potentially compromise wetlands’ functions in reductions in bacteria of public health concern and antibiotic resistance. The results suggest that careful wildlife management together with long-term monitoring of microorganisms of concern are needed for making urban wetlands as a sustainable frontline safeguard of pathogen and antibiotic resistance spread in surface water.

Thermal alteration of soil physico-chemical properties: a systematic study to infer response of Sierra Nevada climosequence soils to forest fires

Abstract. Fire is a common ecosystem perturbation that affects many soil properties. As global fire regimes continue to change with climate change, we investigated thermal alteration of soils' physical and chemical properties after they are exposed to a range of temperatures that are expected during prescribed and wildland fires. For this study, we used topsoils collected from a climosequence transect along the western slope of the Sierra Nevada that spans from 210 to 2865 m a.s.l. All the soils we studied were formed on a granitic parent material and had significant differences in soil organic matter (SOM) concentration and mineralogy owing to the effects of climate on soil development. Topsoils (0–5 cm depth) from the Sierra Nevada climosequence were heated in a muffle furnace at six set temperatures that cover the range of major fire intensity classes (150, 250, 350, 450, 550 and 650 °C). We determined the effects of heating temperature on soil aggregate strength, aggregate size distribution, specific surface area (SSA), mineralogy, pH, cation exchange capacity (CEC), and carbon (C) and nitrogen (N) concentrations. With increasing temperature, we found significant reduction of total C, N and CEC. Aggregate strength also decreased with further implications for loss of C protected inside aggregates. Soil pH and SSA increased with temperature. Most of the statistically significant changes (p &lt; 0.05) occurred between 350 and 450 °C. We observed relatively smaller changes at temperature ranges below 250 °C. This study identifies critical temperature thresholds for significant physico-chemical changes in soils that developed under different climate regimes. Our findings will be of interest to studies of inferences for how soils are likely to respond to different fire intensities under anticipated climate change scenarios.

Annual growth in longleaf (Pinus palustris) and pond pine (P. serotina) in the Sandhills of North Carolina is driven by interactions between fire and climate

Understory fires are important for the maintenance of pine savanna ecosystems of the southeastern U.S., which contain high biodiversity and numerous federally endangered species. Prescribed burns are administered to maintain the open structure of pine savannas, conserve biodiversity, and to reduce wildfire hazard. However, relatively little research has examined which factors control the effects of prescribed burns on mature trees, and how responses might be altered by changing climate. The impact of prescribed burning on growth responses is likely to vary by tree species and by environmental conditions. To test the importance of these factors, tree cores were taken from mature Pinus palustris and Pinus serotina individuals at multiple locations across Fort Bragg, NC, a military preserve with detailed records on prescribed burn history dating back to 1991. Individual trees were sampled along the hydrologic gradient from xeric uplands to streamside wetlands. Annual growth was modeled as a function of species identity, hydrologic position, fire history, and climate conditions. We determined that prescribed burning produced a moderate decline in annual growth indicating that stress from prescribed burns outweighs benefits from increased water and nutrient availability. We found that the negative effects from prescribed burning were diminished or reversed during warmer years, and that the model predicts potential increases in growth during burn years under anticipated climate change scenarios. Surprisingly, there were no significant differences in growth rate by species or hydrologic position. Together these findings suggest that while prescribed burns may have minor, short-term impacts on tree growth under most current conditions, these effects are small enough that they are unlikely to outweigh the many benefits of this management technique for other aspects of ecosystem structure.

Drought-adaptation potential in Fagus sylvatica: linking moisture availability with genetic diversity and dendrochronology.

BackgroundMicroevolution is essential for species persistence especially under anticipated climate change scenarios. Species distribution projection models suggested that the dominant tree species of lowland forests in Switzerland, European beech (Fagus sylvatica L.), might disappear from most areas due to expected longer dry periods. However, if genotypes at the moisture boundary of the species climatic envelope are adapted to lower moisture availability, they can serve as seed source for the continuation of beech forests under changing climates.Methodology/Principal FindingsWith an AFLP genome scan approach, we studied neutral and potentially adaptive genetic variation in Fagus sylvatica in three regions containing a dry and a mesic site each (n ind. = 241, n markers = 517). We linked this dataset with dendrochronological growth measures and local moisture availabilities based on precipitation and soil characteristics. Genetic diversity decreased slightly at dry sites. Overall genetic differentiation was low (F st = 0.028) and Bayesian cluster analysis grouped all populations together suggesting high (historical) gene flow. The Bayesian outlier analyses indicated 13 markers with three markers differing between all dry and mesic sites and the others between the contrasting sites within individual regions. A total of 41 markers, including seven outlier loci, changed their frequency with local moisture availability. Tree height and median basal growth increments were reduced at dry sites, but marker presence/absence was not related to dendrochronological characteristics.Conclusion and Their SignificanceThe outlier alleles and the makers with changing frequencies in relation to moisture availability indicate microevolutionary processes occurring within short geographic distances. The general genetic similarity among sites suggests that ‘preadaptive’ genes can easily spread across the landscape. Yet, due to the long live span of trees, fostering saplings originating from dry sites and grown within mesic sites might increase resistance of beech forests during the anticipated longer dry periods.

A validated genome wide association study to breed cattle adapted to an environment altered by climate change.

Continued production of food in areas predicted to be most affected by climate change, such as dairy farming regions of Australia, will be a major challenge in coming decades. Along with rising temperatures and water shortages, scarcity of inputs such as high energy feeds is predicted. With the motivation of selecting cattle adapted to these changing environments, we conducted a genome wide association study to detect DNA markers (single nucleotide polymorphisms) associated with the sensitivity of milk production to environmental conditions. To do this we combined historical milk production and weather records with dense marker genotypes on dairy sires with many daughters milking across a wide range of production environments in Australia. Markers associated with sensitivity of milk production to feeding level and sensitivity of milk production to temperature humidity index on chromosome nine and twenty nine respectively were validated in two independent populations, one a different breed of cattle. As the extent of linkage disequilibrium across cattle breeds is limited, the underlying causative mutations have been mapped to a small genomic interval containing two promising candidate genes. The validated marker panels we have reported here will aid selection for high milk production under anticipated climate change scenarios, for example selection of sires whose daughters will be most productive at low levels of feeding.

Regulation of planktonic ciliate dynamics and functional composition during spring in Lake Constance

Protozoans are among the most important grazers of phytoplankton and remineralizers of nutrients in marine and freshwater ecosystems, but less is known about the regulation of their pop- ulation dynamics. We analyzed a 12 yr data set of ciliate biomass and species composition in large, deep Lake Constance to understand the factors influencing ciliate spring development. The start of ciliate net growth in spring was closely linked to that of edible algae, chlorophyll a and the vertical mixing intensity, but independent of water temperature. During ciliate spring growth, the relative contribution of ciliated interception feeders was positively related to that of cryptomonads, whereas the relative contribution of filter feeders correlated positively with that of non-cryptomonads. The duration of ciliate dominance in spring was largely controlled by the highly variable onset of the phytoplankton bloom, as the termination of the ciliate bloom was less variable. During years with an extended spring bloom of algae and ciliates, internally forced species shifts were observed in both communities. Interception feeders alternated with filter feeders in their relative importance as did cryptomonads and non-cryptomonads. Extended spring blooms were observed when vertical mixing intensity was low at low temperatures during early spring, which will become less likely under the anticipated climate change scenarios. The termination of the ciliate spring bloom occurred prior to a reduction in food concentration and mostly also prior to the mass development of daphnids alone, but coincided with increased grazing by various predators together, such as rotifers, copepods and daphnids in late May/early June.

Canadian boreal forest ecosystem structure and function in a changing climate: impact on fire regimes

Boreal forest fire regime, which encompasses fire intensity, frequency, seasonality, size, type (crown versus surface), and severity (depth of burn), is an organizing factor of boreal forest landscapes and highly dependant on climate. This review combines what is known about boreal forest dynamics from paleological studies, with the information derived from state-of-the-art climate and vegetation modeling, to present possible scenarios of the impact of anticipated climate change on boreal forest ecosystem structure and function, particularly in relation to fire regimes. Anticipated climatic/atmospheric impact on plant physiological, communal, ecosystem, and finally landscape-level interactions with fire are reviewed. All indications from the modeling sector point towards unprecedented increased regional or seasonal temperatures, with projected changes most pronounced at high latitudes and there greatest in winter. Anticipated climate change scenarios are expected to alter dramatically the boreal forest ecosystems and fire regimes with which they are currently in equilibrium. Changed fire regimes could be represented by increased annual area burned because of an extended fire season, increased fire frequency, and severity. Simulation studies show the potential for greatly reduced boreal forest area and increased fragmentation due to climate change. Fire regime as an ecosystem process is highly sensitive to climate change because fire behaviour responds immediately to fuel moisture, which is affected by precipitation, relative humidity, air temperature, and wind speed. This interaction between climate change and fire regime has the potential to overshadow the importance of the direct effects of global warming on species distribution, migration, substitution, and extinction. Such a scenario suggests that rate and magnitude of fire-regime-induced changes to the boreal forest landscape could greatly exceed anything expected due to atmospheric warming alone. Socioeconomic implications of altered fire regimes in a changing climate are discussed in terms of adaptive fire management strategies, age class distribution, and such global stewardship issues as biodiversity, carbon cycling, and sequestration.