Longer Summer Research Articles

TRENDS, PROBLEMS AND PROSPECTS FOR TEXTILE PRODUCTION IN FUTURE

Demand for textile products is increasing and the adequate supply of textile fibres may become a major problem in coming years because of both changes in world climatic conditions affecting supply of natural fibre sources and because of financial and economic problems. Longer summers and warmer days will support fashion trends for light weight and casual wear. Thus, research on energy saving methods and processes, on fibre modification and structuring of yarns and fabrics will be beneficial.

The role of semiannual cycle in modulating seasonality changes of surface air temperature over China and its mechanism

Taking the semiannual cycle of surface air temperature (SAT) into account in fitting the finer structure of the seasonal cycle, this study reveals the specific role of the semiannual cycle in modulating variations of the season onsets and lengths for the first time. The time-varying amplitudes and phases of the annual and semiannual SAT cycle for the period 1964 to 2017 in China are extracted from daily observations based on harmonic analysis. The results show that the phase differences between the two harmonics remain essentially unchanged, while the amplitude ratio of the semiannual to annual harmonics tends to increase after 1988. This enhanced semiannual cycle together with the global warming and annual cycle changes jointly led to a much longer summer with an average speed of 7.45 days/10 years and shorter spring, autumn, and winter with speeds of − 2.43, − 1.63, and − 4.26 days/10 years, respectively. Such obvious asymmetry cannot be found in fitting seasonal cycles by only annual harmonics. The average absolute percentages of the linear trends of season onsets and lengths caused by the intensification of the semiannual cycle are 52.63% and 78.66%. It indicates that season onsets and length not only depend on the phase of annual and semiannual harmonic, but also highly related to the strength of semiannual cycle. The time evolutions of semiannual cycle strength in China are found to be significantly correlated to the meridional temperature advection. The anomalous stronger southward wind in December can result in colder temperature and hence intensify the semiannual component.

Historical and long-term climate trends in warm permafrost regions: A case study of Bethel, AK

Permafrost is very sensitive to climate factors, with warm permafrost particularly vulnerable to climate change. This paper aims to provide a detailed case study of climate trends of a high-latitude Alaskan site underlain by warm permafrost based on historical data and predictions from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The climate data, including air temperature, precipitation, wind speed, and their annual and seasonal trends from 1950 to 2099, are presented for Bethel, Alaska. The downscaled data are compared with the historical data in the overlap period. Both air and design freezing and thawing indices are calculated using various methods. In comparison, the downscaled model predictions align well with air temperature and wind speed records but not for precipitation, indicating the need for further downscaling at a finer resolution. The historical annual temperature records show a warming rate of 0.40 °C per decade, which is predicted to almost double to 0.78 °C per decade in the 21st century, leading to shorter winters and longer summers. The historical annual precipitation increased by a rate of 14.8 mm per decade from 1950 to 2020, and this trend is predicted to continue but at a slightly lower rate. The wind speed decreased consistently from 1984 to 2020 by 0.9 km/h per decade. However, the CMIP5 predicts that such a trend will diminish, with the mean annual wind speed remaining almost unchanged in this century. The air freezing index exhibits a consistent downtrend from 1950 to 2020, whereas the air thawing index remained flat until 1980 and rose afterward; the CMIP5 predicts that both trends will continue in the 21st century. The design air freezing and thawing indices are sensitive to the assessment periods for both methods. An assessment period shorter than 30 years, e.g., ten years, is recommended to find design indices. It is conservative to use the monthly mean air temperature method for evaluating the design air freezing index and apply the extreme event method for the design thawing index.

Analysis of Climate and Income-Related Factors for High Regional Child Drowning Mortality in China.

Objectives: To assess the relationship between regional climatic factors and child drowning in China. Methods: Provincial age-specific drowning rate, climatic and income data were collected. We conducted a geographically weighted regression to evaluate the association between drowning and climatic factors. A generalized additive model was used to comprise a bivariate term with which to investigate the interaction of environmental risk factors and whether such interactions influence drowning mortality. Results: In southern China, an abundance of water systems and increased precipitation, as well as hotter and longer summers, lead to significantly higher drowning compared with that in northern China. Long summers and low economic performance in parts of Xinjiang were key factors for its high drowning mortality rate. Linear and nonlinear joint effects were observed between the risk factors of drowning. Conclusion: Different regions should use adaptive measures to reduce drowning risks, for example, communication campaigns during the summer period or when the weather changes.

A Probe in the Language Features of Fruit Chan's Films from the Perspective of Audio-visual Characteristics: Taking the Trilogy on Hong Kong's Return to China as an Example

After the territory of Hong Kong formally returned in 1997 to its rightful owner of China, Fruit Chan (Chen Guo), a director, rose to fame with his trilogy on HK's return (namely Little Cheung, Made in Hong Kong, and The Longest Summer). Since then, he has successively made many films reflecting humans' real living status. Most of Hong Kong-made films in the past were standardized and industrialized, such as comedies and action films which are familiar to us, while there were few realistic films that could indeed depict and present the social changes to the public. Therefore, films like Fruit Chan's, which demonstrates tragic and profound ideas, are extremely rare and valuable in Hong Kong's film industry. Although Chan has not produced many works, all of them are endowed with realistic hue, aesthetic characteristics, and profound humanistic thoughts, which makes his films monuments of Hong Kong's realistic ones. It is easy to find sense of mission and sentimental feelings in his films, enabling us to better see how Hong Kong films move forward in the direction of visual transmission after Hong Kong’s return to China from multiplex angles of view.

LOCAL MANIFESTATIONS OF CLIMATE CHANGES ON THE EXAMPLE OF “MEDOBORY” NATURE RESERVE DURING 2006-2020

The analysis of the main meteorological indicators, given according to the data of hydrometeorological post in the village of Hrymailiv for the last fifteen years, is presented. The dynamics of changes in the average annual, monthly and daily, minimum, maximum air temperatures, precipitation, relative humidity, atmospheric pressure, etc. has been studied for the Nature Reserve "Medobory", the analysis of climatic features of months for the period of 2006-2020 is carried out. The temperature mode of the Reserve during the year is marked by considerable fluctuations of temperatures: from + 18,9ºС in July to -4,7ºС in January. The established duration of seasons is marked by strong variability, which is a sign of climate changing: the shortest and latest winter in the period of investigation recorded in 2016, began on December 29 and lasted 42 days, and the longest one - in 2018, lasted 130 days; the longest spring was in 2020 - 116 days, the shortest one - in 2018, lasted 30 days. The longest summer in 2018 lasted 147 days; in 2017-2018 a significant decrease in average daily air temperatures in the first half of July was observed; August and September parts of summer in 2016-2020 were hot, with fairly high maximums and very little precipitation. The latest beginning of autumn for the entire observation period is September 27, 2020, the shortest season - in 2016, only 53 days. The duration of autumn decreases, the average value reaches 75 days, the duration of summer increases - 112 days. It is noted that the nature of precipitation has changed - rain falls in the form of heavy, short-term showers, for one downpour the monthly norm of precipitations can fall out; over the last five years, the average length of the growing season has increased by 19 days and 13 days more than the average for fifteen years, the sum of active temperatures above the average for the last five years by 299.3ºC, for the last fifteen years - by 183.5ºС. On the territory of the Nature Reserve "Medobory" other local manifestations of climate changing were recorded, expressed as follows: the average annual air temperature over the past five years increased by 0.5 ° C (the warmest for the entire observation period was 2020 with an average temperature of 10, 1ºС, just then there were 43 days in winter (61%) with positive daily average air temperatures); meteorological natural phenomena of nature became more frequent: heavy rains, snowfalls, heavy hail showers, ice, fogs, dust storms, ice frosting-up; exceeded the maximum air temperature for the last five years: October 3, 2016 (27.0 ° C), August 3, 2017 (38.5 ° C), May 25, 2018 (34.0 ° C), 21 June 2018 (34.0ºC), March 31, 2019 (21.2ºC), and the minimum - June 8, 2016 (0.0°C), July 7, 2017 (4.7°C), September 30, 2018 (-2.5°C), April 1, 2020 (-7.0°C). The latest spring light frost recorded on May 22, 2020 (-1.0ºC), which led to mass frosting-up of herbaceous plant species. Every autumn at the end of September, light frosts are already registered: -1.5ºC - September 28, 2016, -1.0ºC and -0.9ºC - September 29 and September 30, 2017, -2.5ºC - September 30, 2018, - 1.8ºС - September 21, 2019, -1.0ºС - September 19, 2020, the last one - the earliest during the observation period and also in the summer part of September. For the first time in 2020, the relative humidity in March was 16% below normal, mainly due to the second and third decades (58% and 47% correspondingly), in April it was only 39% - 27% below normal. Such deviations were not observed even in the dry summer and autumn months.
 Key words: air temperature, precipitation, climatic seasons, meteorological natural phenomena.

Longer summers in the Northern Hemisphere under global warming

Longer summers in the Northern Hemisphere under global warming

Temporal-Spatial changes of monthly vegetation growth and their driving forces in the ancient Yellow river irrigation system, China

Irrigation systems play vital roles not only in food production but also in supporting ecosystems. Understanding how the ecosystem has evolved in response to human activities is crucial for sustainable food production, especially for arid and semi-arid regions. In this study, we examined the trends of vegetation growth on a monthly basis in the ancient Yellow River irrigation system in Ningxia, China. We used the leaf area index (LAI) to characterize the vegetation growth from 2007 to 2019. The LAI trends were associated with a series of driving forces, explaining the spatial and temporal change of vegetation growth. With the provision of the Wilks feature importance method, 2-month averaged air temperature and irrigation were identified as the two most important variables for monthly LAI simulation. Future climate projections based on the Regional Climate Model system (RegCM) suggested dryer and longer summers under the RCP 8.5 scenario. These changes will increase the crop water demand during the growing months. In the future, water conflict might be further intensified in May, in which the present irrigation water has already led to a decreased crop growth. Our findings demonstrated that the Mann Kendall monthly trend analysis could provide more helpful information for monitoring the vegetation growth than the trend analysis on a yearly and seasonal basis.

Warming Arctic summers unlikely to increase productivity of shorebirds through renesting

Climate change in the Arctic is leading to earlier summers, creating a phenological mismatch between the hatching of insectivorous birds and the availability of their invertebrate prey. While phenological mismatch would presumably lower the survival of chicks, climate change is also leading to longer, warmer summers that may increase the annual productivity of birds by allowing adults to lay nests over a longer period of time, replace more nests that fail, and provide physiological relief to chicks (i.e., warmer temperatures that reduce thermoregulatory costs). However, there is little information on how these competing ecological processes will ultimately impact the demography of bird populations. In 2008 and 2009, we investigated the survival of chicks from initial and experimentally-induced replacement nests of arcticola Dunlin (Calidris alpina) breeding near Utqiaġvik, Alaska. We monitored survival of 66 broods from 41 initial and 25 replacement nests. Based on the average hatch date of each group, chick survival (up to age 15 days) from replacement nests (Ŝi = 0.10; 95% CI = 0.02–0.22) was substantially lower than initial nests (Ŝi = 0.67; 95% CI = 0.48–0.81). Daily survival rates were greater for older chicks, chicks from earlier-laid clutches, and during periods of greater invertebrate availability. As temperature was less important to daily survival rates of shorebird chicks than invertebrate availability, our results indicate that any physiological relief experienced by chicks will likely be overshadowed by the need for adequate food. Furthermore, the processes creating a phenological mismatch between hatching of shorebird young and invertebrate emergence ensures that warmer, longer breeding seasons will not translate into abundant food throughout the longer summers. Thus, despite having a greater opportunity to nest later (and potentially replace nests), young from these late-hatching broods will likely not have sufficient food to survive. Collectively, these results indicate that warmer, longer summers in the Arctic are unlikely to increase annual recruitment rates, and thus unable to compensate for low adult survival, which is typically limited by factors away from the Arctic-breeding grounds.

Limitations to adjusting growing periods in different agroecological zones of Pakistan

CONTEXTClimate change affects the timing and length of crop seasons. Adjusting sowing dates is a commonly recommended adaptation, but little is known about its efficacy in practice. OBJECTIVEThis study investigated farm-level adjustments to sowing and harvesting dates (i.e., the growing period) in response to shifts in meteorological crop seasons during the last 30 years. Impacts on yields and farmers' complementary adaptation strategies were also examined. METHODSUsing data from 287 farm households in four agroecological zones of the Indus Basin, Pakistan, we explored farmers' perceptions of shifts in seasons and adjustments in crop growing period. We verified these using meteorological station data on temperatures, precipitation and growing degree days. RESULTS AND CONCLUSIONSAt lower altitudes (irrigated plains and mid-hills), the summer crop season had lengthened and the winter season shortened, but in both seasons the growing period was shorter, due to higher temperatures. The summer growing period was shorter by 5 (±11) days on the irrigated plains, while there was no significant change in length of the summer growing period in the mid-hills. The winter growing period was shorter by 15 (±6) days on both the plains and in the mid-hills, which negatively impacted yields. As an adaptation strategy, changing sowing dates was only somewhat effective in preventing yield losses. Farmers adopted complementary strategies, but these brought additional costs. At higher altitudes (valleys and mountains), the frost period had shortened, resulting in longer summer and winter crop seasons, and longer growing periods. The summer growing period was extended by 7 (±4) days in the valleys and 10 (±6) days in the mountains, while the winter growing period was extended by 3 (±3) days in the valleys and 13 (±5) days in the mountains, positively impacting yields. Farmers' adjustments in sowing dates did not necessarily parallel to seasonal shifts, as farm decision-making also had to consider risks linked to climate variability and management limitations. For the future, farmers at lower altitudes indicated limited further scope for adjusting sowing and harvesting dates. SIGNIFICANCEOur results contribute to a contextual understanding of farmers' responses to shifts in crop seasons. They indicate the need for adaptation planning to take advantage of extended growing periods in higher altitude zones, while supporting farmers in areas where seasonal shifts have negative impacts. Our findings furthermore indicate limits to adaptation in regions where agriculture is already challenged and provide suggestions for crop system-specific complementary measures.

Regional Differences in Height, Weight, and Body Composition may Result from Photoperiodic Responses: An Ecological Analysis of Japanese Children and Adolescents.

This ecological study examined whether geographical differences in the physique of Japanese children and adolescents can be explained from the perspective of photoperiodicity induced by effective day length (light duration exceeding a certain threshold of illuminance) using prefecture-level anatomical data and Mesh Climatic Data. Multiple regression analysis for height prediction demonstrated that when controlled by weight, effective day lengths of the longest and shortest months were inversely correlated with height distribution. Conversely, for weight prediction, when controlled by height, the effective day lengths of the longest and shortest months were positively correlated with weight distribution. The regression coefficients were greater for the effective day length of the shortest month in both height and weight prediction. This phenomenon where the same two explanatory variables are negatively correlated with height and positively correlated with weight in a significant manner is rare, and there may be no physiological interpretation of this phenomenon other than one based on changes in thyroid hormone signaling. These distribution characteristics are common to the photoperiodicity by which seasonal breeding vertebrates reciprocally switch thyroid hormone signaling according to prior photoperiodic history through epigenetic functions. From these perspectives, thyroid hormone signaling in a certain region was assumed to be activated in summer according to the prior shorter winter day length and inactivated in winter according to the prior longer summer day length. Regarding the prevalence of obesity, the coexistence of longer summer and winter day lengths was thought to set body composition to be short and fat in early adolescence.

Cultural artefacts and the ‘migration crisis’: Disruptive materialities in works by Navid Kermani and Maxi Obexer

Amplified worldwide fragility and growing mobility have contributed to increased forced migration towards Europe. However, Europe’s present focus on border protection has furthered the ‘migrant crisis’ which is very much a crisis of response. News about the ‘migrant crisis’ continues to dominate political discourse in Europe and elsewhere. The discussions typically focus on Europe’s supposed solutions in the form of increased border security, new political agreements, and various forms of humanitarian aid. This article reviews four literary texts about Europe’s responses to forced migration and proposes that the literary treatment of various cultural artefacts employed in these texts critiques Europe’s current restrictionism. Two speeches by Navid Kermani, ‘Towards Europe’ and ‘On the sixty-fifth Anniversary of the Promulgation of the German Constitution’ and two novels by Maxi Obexer, Wenn gefährliche Hunde lachen (‘When dangerous dogs laugh’) and Europas längster Sommer (‘Europe’s longest summer’) make reference to several phenomenal objects and also to gestures. In and of themselves, these cultural artefacts such as beds, blankets, buses, lipsticks, T-shirts, shoes, and even the gestures of kneeling and bowing, may not possess anything disruptive. However, there is an unruly quality about them that puts a spotlight on the precarity of survival migrants who cannot access the European asylum process.

A regional approach to climate and health adaptation in the Middle East

Abstract Background The Middle East (ME) is expected to be influenced by climate changes that will significantly affect human health. An increase in temperature and in the intensity, length and frequency of heat waves, alongside a decrease in precipitation, have been observed, and longer summers and shorter winters are expected. Population growth intensifies the stress on water and the ecosystem in an already sensitive region. Moreover, political conflicts intensify the vulnerability of the region's population and prevent cross-border collaboration and knowledge transfer. The aims of this talk are to: 1) present climate scenarios and potential health risks for the ME; and 2) present a regional inter-disciplinary collaboration that focuses on climate and health research. Methods To prioritize regional research directions, a group of climatologists and public health researchers from the ME and Europe convened in an expert workshop, which included a process of consensus-building regarding research priorities and potential collaboration. Results Associated health risks are mainly increases in morbidity and mortality due to heatwaves, and increases in potentially deadly vector- water- air- and food-borne diseases such as chikungunya, yellow fever and dengue fever, due to expansion of invasive species of mosquitoes. There are wide economic and infrastructure gaps among the region's countries, entailing different levels of preparedness. Countries also face multiple intra- and inter-country political conflicts and instability which further weaken their ability to adapt at the regional level. However, climate change has regional impacts which should be understood and mitigated at that level. Research priorities include spatio-temporal research on heat and health outcomes; regional surveillance of infectious diseases; and preparedness of health systems and pathways for collaboration among health agencies in the midst of a political conflict with an emphasis on vulnerable populations. Key messages Inter-sectoral and inter-disciplinary work is a known requirement for tackling climate change challenges. Structural changes are needed at both the local and regional levels to fulfill this vision. Political conflicts in the Middle East weaken the ability to adapt to climate change in a vulnerable region.

Perceived Climate Variability and Compounding Stressors: Implications for Risks to Livelihoods of Smallholder Indian Farmers.

Micro-scale perspectives are seldom included in planned climate change adaptations, yet farmers' perceptions can provide useful insights into livelihood impacts from interactions between climatic and other stressors. This research aims to understand how climate variability and other stressors are impacting the livelihoods of smallholder farmers in Azamgarh district, eastern Uttar Pradesh, India. Data from 84 smallholder farmers were collected using mixed qualitative and quantitative approaches, including interview and participatory methods, informed by multiple stressor and sustainable livelihood frameworks. Results revealed that farmers are increasingly facing problems caused by the reduced duration and number of rainy days, and erratic rainfall. Anomalies in seasonal cycles (longer summers, shorter winters) seem to have altered the local climate. Farmers reported that repeated drought impacts, even in years of moderate rainfall, are adversely affecting the rice crop, challenging the formal definition of drought. Climate variability, identified as the foremost stressor, often acts as a risk multiplier for ecological (e.g., soil sodicity), socio-economic (e.g., rising costs of cultivation) and political (e.g., mismatching policies and poor extension systems) stressors. In addition to climate stresses, resource-poor marginal groups in particular experienced higher risks resulting from changes in resource management regimes. This study provides an important cue to revisit the formal definitions of normal rainfall and drought, accommodating farmers' perceptions that evenly distributed rainfall, and not total rainfall is a key determinant of crop yields. Though India has developed adaptive measures for climate change and variability, integration of farmers' perceptions of climate and other stressors into such policies can improve the resilience of smallholder farmers, who have hitherto depended largely on autonomous adaptation strategies.

Population dynamics of Rana sierrae at Dusy Basin: influence of non‐native predators, drought, and restoration potential

AbstractThe Sierra Nevada yellow‐legged frog (Rana sierrae) was once an abundant and widely distributed amphibian in California's alpine ranges. Rana sierrae is adapted to high‐elevation, fishless habitats. Its adaptions are reflected in a unique life cycle that involves a flexible, extended juvenile phase due to the short growing season typical of its alpine habitat. However, today this species is critically endangered, and most populations have been extirpated from their native range. Here, we present an 18‐yr‐long demographic study of a R. sierrae population in 15 lakes at Dusy Basin in Kings Canyon National Park. We focused on the period leading up to the arrival of the pathogenic chytrid fungus, Batrachochytrium dendrobatidis (Bd), and the subsequent local extinction of R. sierrae. We used N‐mixture abundance modeling, which accounts for detection probabilities, to quantify factors affecting frog abundance at different life stages. The abundance of subadult and adult frogs was negatively associated with the presence of introduced trout (Oncorhynchus mykiss and O. aquabonita). Frog abundance in all life stages was positively associated with lake surface area. The propensity of lakes drying correlated negatively with abundance of eggs, subadults, and adults in the following year. Moreover, drought years, characterized by longer summers and less winter snowpack, led to higher rates of lakes drying. Finally, our results suggest that the frequency of such droughts in the region has increased since 1937. Increased frequency or severity of droughts is expected to decrease the value of shallow lakes for Sierra Nevada yellow‐legged frogs because these habitats are prone to drying. We discuss our results in terms of future restoration strategies, including reintroduction and probiotic treatment, in this changed and changing ecosystem.

Phenological mismatch in Arctic-breeding shorebirds: Impact of snowmelt and unpredictable weather conditions on food availability and chick growth.

The ecological consequences of climate change have been recognized in numerous species, with perhaps phenology being the most well‐documented change. Phenological changes may have negative consequences when organisms within different trophic levels respond to environmental changes at different rates, potentially leading to phenological mismatches between predators and their prey. This may be especially apparent in the Arctic, which has been affected more by climate change than other regions, resulting in earlier, warmer, and longer summers. During a 7‐year study near Utqiaġvik (formerly Barrow), Alaska, we estimated phenological mismatch in relation to food availability and chick growth in a community of Arctic‐breeding shorebirds experiencing advancement of environmental conditions (i.e., snowmelt). Our results indicate that Arctic‐breeding shorebirds have experienced increased phenological mismatch with earlier snowmelt conditions. However, the degree of phenological mismatch was not a good predictor of food availability, as weather conditions after snowmelt made invertebrate availability highly unpredictable. As a result, the food available to shorebird chicks that were 2–10 days old was highly variable among years (ranging from 6.2 to 28.8 mg trap−1 day−1 among years in eight species), and was often inadequate for average growth (only 20%–54% of Dunlin and Pectoral Sandpiper broods on average had adequate food across a 4‐year period). Although weather conditions vary among years, shorebirds that nested earlier in relation to snowmelt generally had more food available during brood rearing, and thus, greater chick growth rates. Despite the strong selective pressure to nest early, advancement of nesting is likely limited by the amount of plasticity in the start and progression of migration. Therefore, long‐term climatic changes resulting in earlier snowmelt have the potential to greatly affect shorebird populations, especially if shorebirds are unable to advance nest initiation sufficiently to keep pace with seasonal advancement of their invertebrate prey.

Progressive sensitivity of trophic levels to warming underlies an elevational gradient in ant–aphid mutualism strength

Although species interactions are often proposed to be stronger at lower latitudes and elevations, few studies have evaluated the mechanisms driving such patterns. In this study, we assessed whether, and by which mechanisms, abiotic changes associated with elevation altered the outcome of an ant–aphid protection mutualism. To do so, we characterized the multi‐trophic interactions among the ant Formica podzolica, the aphid Aphis varians, and aphid natural enemies occurring on the plant Chamerion angustifolium within replicate high and low elevation valleys. Low (versus high) elevation sites had longer summers (snowmelt 13 days earlier) and were on average 1.1°C warmer and 41% drier throughout the year. At low elevations, individual ant colonies consumed approximately double the volume of carbohydrate baits, likely due to a higher foraging tempo, and possibly due to a greater demand for sugar‐ versus protein‐rich resources (as indicated by stable isotope analysis). Wild aphid colonies at low elevations were visited by 1.4‐fold more natural enemies (controlling for variation in aphid abundance), while experimental aphid colonies on potted plants were tended 52% more frequently by ants. As a result, ants increased aphid colony survival by 66% at low elevations but had no detectable effect at high elevations; at low (versus high) elevations aphid colonies without ants had lower survival, demonstrating stronger predator effects, while aphid colonies with ants had higher survival, demonstrating even stronger ant benefits. Analyses for the effects of mean summer temperature yielded qualitatively identical results to those based on elevation. Collectively, these findings support predictions for a greater sensitivity of higher trophic levels to warming and demonstrate how species interactions can vary across environmental gradients due to simultaneous changes in species traits and abundances across multiple trophic levels.

Effects of water level and climate on the hydrodynamics and water quality of Anvil Lake, Wisconsin, a shallow seepage lake

ABSTRACTRobertson DM, Juckem PF, Dantoin ED, Winslow LA. 2018. Effects of water level and climate on the hydrodynamics and water quality of Anvil Lake, Wisconsin, a shallow seepage lake. Lake Reserv Manage. 34:00–00.Interannual differences in the water quality of Anvil Lake, Wisconsin, were examined to determine how water level and climate affect the hydrodynamics and trophic state of shallow lakes, and their importance compared to anthropogenic changes in the watershed. Anvil Lake is a relatively pristine seepage lake with hydrology dominated by precipitation, evaporation, and groundwater exchange enabling the typically subtle effects of water level and climate to be evaluated. Groundwater and hydrodynamic models were used to describe lake water and phosphorus budgets and how its hydrodynamics are affected by water level and air temperature. Decreases in water level are expected to cause Anvil Lake and other shallow lakes to stratify fewer days, and have warmer bottom temperatures and more deep-mixing events. Increasing air temperatures should cause these lakes to have shorter ice cover, longer summer stratification periods, and warmer bottom temperatures. How water level affects water quality depends on how nutrient loading and lake volume vary: during drier, low-water years, lakes with large interannual changes in loading should have better water quality, whereas lakes with small changes in loading should degrade slightly. Anthropogenic changes in Anvil Lake's watershed over the past ∼100 yr were about 1.5 times the effects of changes in water level when levels were low, but the effects were similar when levels were high. Climate warming is expected to increase productivity in shallow lakes because warmer air temperatures will likely increase bottom temperatures increasing sediment phosphorus release and deep-mixing events enabling this phosphorus to reach the epilimnion.

Warming drives a front of white spruce establishment near western treeline, Alaska.

Regional warming has led to increased productivity near the boreal forest margin in Alaska. To date, the effects of warming on seedling recruitment have received little attention, in spite of forecasted forest expansion. Here, we used stand structure and environmental data from 95 white spruce (Picea glauca) plots sampled across a longitudinal gradient in southwest Alaska to explore factors influencing spruce establishment and recruitment near western treeline. We used total counts of live seedlings, saplings, and trees, representing five life stages, to evaluate whether geospatial, climate, and measured plot covariates predicted abundance, using current abundance distributions as a surrogate for climate conditions in the past. We used generalized linear models to test the null hypothesis that conditions favorable for recruitment were similar along the environmental gradient represented by longitude, by exploring relationships between per-plot counts of each life stage and the covariates hypothesized to affect abundance. We also examined the relationship between growing degree days (GDD) and seedling establishment over a period of three decades using tree-ring chronologies obtained from cores taken at a subset of our sites (n=30). Our results indicated that seedling, sapling, and tree abundance were positively correlated with temperature across the study area. The response to longitude was mixed, with earlier life stages (seedlings, saplings) most abundant at the western end of the gradient, and later life stages (trees) most abundant to the east. The differential relationship between longitude and life-stage abundance suggests a moving front of white spruce establishment through time, driven by changes in environmental conditions near the species' western range limit. Likewise, we found a positive relationship between periods of seedling establishment and GDD, suggesting that longer summers and/or greater heat accumulation might enhance establishment, consistent with the positive relationship we found between life-stage abundance and temperature.

Behavioral responses to annual temperature variation alter the dominant energy pathway, growth, and condition of a cold-water predator

There is a pressing need to understand how ecosystems will respond to climate change. To date, no long-term empirical studies have confirmed that fish populations exhibit adaptive foraging behavior in response to temperature variation and the potential implications this has on fitness. Here, we use an unparalleled 11-y acoustic telemetry, stable isotope, and mark-recapture dataset to test if a population of lake trout (Salvelinus namaycush), a cold-water stenotherm, adjusted its use of habitat and energy sources in response to annual variations in lake temperatures during the open-water season and how these changes translated to the growth and condition of individual fish. We found that climate influenced access to littoral regions in spring (data from telemetry), which in turn influenced energy acquisition (data from isotopes), and growth (mark-recapture data). In more stressful years, those with shorter springs and longer summers, lake trout had reduced access to littoral habitat and assimilated less littoral energy, resulting in reduced growth and condition. Annual variation in prey abundance influenced lake trout foraging tactics (i.e., the balance of the number and duration of forays) but not the overall time spent in littoral regions. Lake trout greatly reduced their use of littoral habitat and occupied deep pelagic waters during the summer. Together, our results provide clear evidence that climate-mediated behavior can influence the dominant energy pathways of top predators, with implications ranging from individual fitness to food web stability.