Dry Summer Research Articles

Effects of mild water restriction on nutrient digestion and protein metabolism in desert-adapted goats

• Mildly restricting drinking water intake by ≤ 21 % does not reduce feed intake in desert-adapted goats. • Declining drinking water intake enhances rumen fermentation, but reduces microbial growth. • Lowering drinking water intake shifts nitrogen excretion from urine to faeces. • Effects of drinking water restriction differ depending on diet and animal factors. The aim of the present study was to determine the effects of mild drinking water restriction ( WR ) on feed intake, diet digestibility, rumen fermentation, and nitrogen ( N ) balance in a desert-adapted goat breed of Oman. Two feeding trials were conducted during the dry summer months (August-October) in 2013 and 2014. In each trial, nine adult male Batinah goats were exposed to two levels of mild WR (WR: 85 % (WR15) and 70 % (WR30) of individual ad libitum consumption; 100 % (WR0)) in a 3 × 3 Latin Square design. Drinking water intake, feed offered and refused, and excretion of urine and faeces were quantified and samples analysed for crude nutrient and fibre fractions. Moreover, rumen microbial protein synthesis was estimated from urinary purine derivatives excretion. In trial 2, rumen fermentation characteristics were additionally studied in three rumen-fistulated goats. Linear and quadratic effects of WR in each trial were assessed by mixed model analysis, whereas correlations between drinking water intake and response variables were determined across both trials. For WR30, drinking water intake was 79 % and 90 %, respectively, of the water intake of WR0 goats in trial 1 and WR15 goats in trial 2. Water restriction had no effect on feed intake, rumen microbial protein synthesis, and N balance in both trials. However, apparent total tract digestibilities of neutral and acid detergent fibre tended to decrease linearly ( p ≤ 0.081) with increasing WR level in trial 1, whereas those of dry matter and organic matter were lower ( p ≤ 0.028) for WR15 than for WR0 and WR30 in trial 2. Proportions of butyrate ( p ≤ 0.046) and isovalerate ( p = 0.087) in rumen fluid were greater and those of propionate ( p = 0.079) and valerate ( p = 0.062) lower for WR30 as compared to one or both of the other WR levels. Duodenal microbial N flow and efficiency of microbial protein synthesis did not differ between WR levels. Yet, across both trials, both variables correlated positively with drinking water intake. Similarly, declining drinking water intake increased the ratio between faecal and urine N excretion (r=−0.55) and the N concentration in faeces (r=−0.42), but reduced the fibre concentration (r=0.38) and the proportion of undigested feed N in faeces (r=0.49). Mild restriction of drinking water intake to ≥ 79 % of the ad libitum consumption, which is expected to occur more frequently with advancing climate change in the semi-arid tropics and subtropics, may impair feed nutrient use and thus performance of regionally adapted small ruminants, while improving the quality of their manure.

Guidelines for Studying Diverse Types of Compound Weather and Climate Events

AbstractCompound weather and climate events are combinations of climate drivers and/or hazards that contribute to societal or environmental risk. Studying compound events often requires a multidisciplinary approach combining domain knowledge of the underlying processes with, for example, statistical methods and climate model outputs. Recently, to aid the development of research on compound events, four compound event types were introduced, namely (a) preconditioned, (b) multivariate, (c) temporally compounding, and (d) spatially compounding events. However, guidelines on how to study these types of events are still lacking. Here, we consider four case studies, each associated with a specific event type and a research question, to illustrate how the key elements of compound events (e.g., analytical tools and relevant physical effects) can be identified. These case studies show that (a) impacts on crops from hot and dry summers can be exacerbated by preconditioning effects of dry and bright springs. (b) Assessing compound coastal flooding in Perth (Australia) requires considering the dynamics of a non‐stationary multivariate process. For instance, future mean sea‐level rise will lead to the emergence of concurrent coastal and fluvial extremes, enhancing compound flooding risk. (c) In Portugal, deep‐landslides are often caused by temporal clusters of moderate precipitation events. Finally, (d) crop yield failures in France and Germany are strongly correlated, threatening European food security through spatially compounding effects. These analyses allow for identifying general recommendations for studying compound events. Overall, our insights can serve as a blueprint for compound event analysis across disciplines and sectors.

Comparative evaluation of varieties of winter hard wheat by the weight of 1000 grains with different morphotype of the germ

s. The productivity of plants depends on the weight of 1000 grains (M1000), the density of the productive stalk, the number of grains per ear, cultivation conditions, etc. The aim of the research was to comparatively evaluate M1000 in seeds differing in the morphology of the embryonic part, in varieties of durum winter wheat bred by the Agrarian Scientific Center “Donskoy”. The weight of 1000 grains were determined according to the State Standard 10842-89. The most productive and frequently encountered are the seeds with the main morphotypes 2, 3, 4, and 5, and the seeds with minor morphotypes 1a, 1, 6, and 7 make up 5%. An average positive relationship with M1000 of the entire heap of seeds was shown only for seeds of 2 main morphotypes - embryo morphotypes 2 (r = 0.45) and embryo morphotypes 5 (r = 0.42). Indicator M1000 embryo morphotypes 3 is not associated with M1000 of the whole seed heap, and all other embryo morphotypes for this trait have medium and strong negative correlation. Consequently, obtaining a fully formed grain in the dry spring and summer period is ensured by the stability of the filling of seeds of the main morphotypes 2 and 5.

Community cooling infrastructure from waste heat among diverse building types in Rourkela Steel Township, India

Urban building energy modeling is an important field in the current decade due to the rising rate of urbanization, specifically in developing countries. The UN environment is promoting urban level space cooling approaches in the upcoming smart cities of India. Rourkela is a tier-2 steel township included within the ‘smart city’ mission in India and houses one of the largest Steel Plants of India, classified under Koppen Aw tropical climate zone. However it experiences extreme heat stress in the dry summer season before the onset of monsoons. The given study proposes an alternative cooling scenario utilizing waste heat from the rolling mill with which cooling in the range of 700-900 tons of nearly zero energy cooling can be made available in the surrounding areas, otherwise catered by an energy intensive cooling system reporting a COP of 2.45. This study can be further expanded to provide cooling to the nearby residential communities keeping the steel plant area as center point for community cooling infrastructure provision.

Diverse biosphere influence on carbon and heat in mixed urban Mediterranean landscape revealed by high resolution thermal and optical remote sensing

A fundamental challenge in verifying urban CO2 emissions reductions is estimating the biological influence that can confound emission source attribution across heterogeneous and diverse landscapes. Recent work using atmospheric radiocarbon revealed a substantial seasonal influence of the managed urban biosphere on regional carbon budgets in the Los Angeles megacity, but lacked spatially explicit attribution of the diverse biological influences needed for flux quantification and decision making. New high-resolution maps of land cover (0.6 m) and irrigation (30 m) derived from optical and thermal sensors can simultaneously resolve landscape influences related to vegetation type (tree, grass, shrub), land use, and fragmentation needed to accurately quantify biological influences on CO2 exchange in complex urban environments. We integrate these maps with the Urban Vegetation Photosynthesis and Respiration Model (UrbanVPRM) to quantify spatial and seasonal variability in gross primary production (GPP) across urban and non-urban regions of Southern California Air Basin (SoCAB). Results show that land use and landscape fragmentation have a significant influence on urban GPP and canopy temperature within the water-limited Mediterranean SoCAB climate. Irrigated vegetation accounts for 31% of urban GPP, driven by turfgrass, and is more productive (1.7 vs 0.9 μmol m−2 s−1) and cooler (2.2 ± 0.5 K) than non-irrigated vegetation during hot dry summer months. Fragmented landscapes, representing mostly vegetated urban greenspaces, account for 50% of urban GPP. Cooling from irrigation alleviates strong warming along greenspace edges within 100 m of impervious surfaces, and increases GPP by a factor of two, compared to non-irrigated edges. Finally, we note that non-irrigated shrubs are typically more productive than non-irrigated trees and grass, and equally productive as irrigated vegetation. These results imply a potential water savings benefit of urban shrubs, but more work is needed to understand carbon vs water usage tradeoffs of managed vs unmanaged vegetation.

37 Years of Forest Monitoring in Switzerland: Drought Effects on Fagus sylvatica

European beech is one of the most important deciduous tree species in natural forest ecosystems in Central Europe. Its dominance is now being questioned by the emerging drought damages due to the increased incidence of severe summer droughts. In Switzerland, Fagus sylvatica have been observed in the Intercantonal Forest Observation Program since 1984. The dataset presented here includes 179176 annual observations of beech trees on 102 plots during 37 years. The plots cover gradients in drought, nitrogen deposition, ozone, age, altitude, and soil chemistry. In dry regions of Switzerland, the dry and hot summer of 2018 caused a serious branch dieback, increased mortality in Fagus sylvatica and increased yellowing of leaves. Beech trees recovered less after 2018 than after the dry summer 2003 which had been similar in drought intensity except that the drought in 2018 started earlier in spring. Our data analyses suggest the importance of drought in subsequent years for crown transparency and mortality in beech. The drought in 2018 followed previous dry years of 2015 and 2017 which pre-weakened the trees. Our long-term data indicate that the drought from up to three previous years were significant predictors for both tree mortality and for the proportion of trees with serious (>60%) crown transparency. The delay in mortality after the weakening event suggests also the importance of weakness parasites. The staining of active vessels with safranine revealed that the cavitation caused by the low tree water potentials in 2018 persisted at least partially in 2019. Thus, the ability of the branches to conduct water was reduced and the branches dried out. Furthermore, photooxidation in light-exposed leaves has increased strongly since 2011. This phenomenon was related to low concentrations of foliar phosphorus (P) and hot temperatures before leaf harvest. The observed drought effects can be categorized as (i) hydraulic failure (branch dieback), (ii) energy starvation as a consequence of closed stomata and P deficiency (photooxidation) and (iii) infestation with weakness parasites (beech bark disease and root rots).

Drought Tolerant Varieties of Common Beans (Phaseolus vulgaris) in Central Afghanistan

Legume crops have played a significant role in the historical dietary regime of Afghan peoples. Recently, production of common beans has increased on Afghan farms relative to other leguminous crops. However, compared with other pulse crops, common beans are more prone to water stress. To select drought resistant common beans, several varieties were assessed in the field during a sequence of restricted water supplies for two years and the local drought regime was analyzed for a 12-years period. The first experiment in 2018 compared five bean varieties under four irrigation regimes. White and black beans with long maturation periods and climber habits, and motley beans, characterized by moderate maturity and semi-climber structures, were susceptible to drought and did not mature well under restricted irrigation and ambient climate conditions. The other two varieties, red and pied beans, adapted to restricted water supplies and the long dry summers; these two varieties were assessed again in 2019. Statistical analyses and inferences based on the 2019 study suggest that red beans are more adaptable to water deficit treatments compared to pied beans. Therefore, red beans are considered a better option given the frequent mid- to late-summer droughts that occur in this region, together with the generally harsh mountain climate and short growing season of the central Afghanistan highlands. As a second varietal choice, pied beans are reasonably drought tolerant based on our findings.

Did desmid assemblages in Dutch moorland pools recover from acidification in the past century?

In order to monitor recovery from acidification caused by acid atmospheric deposition, desmids and water chemistry were sampled in three Dutch moorland pools regularly from 1978 to 2014. Reference desmid samples from the early twentieth century were retrieved from old collections. Changes of the desmid assemblages were assessed by analyses of traits, including indicator values for pH and total phosphate, conservation value, cell volume and surface/volume (s/v) ratio. Direct correspondence analysis (DCA) traced relations between desmids and environmental variables. Between 1916 and 2014, species composition altered due to changes in acidifying atmospheric deposition: The change was most pronounced in pools with relatively flat shores exposed to the atmosphere in extremely dry summers. After the dry summer of 1921, changes were slight, but after the dry summer of 1976, changes were dramatic, when the sulphur and nitrogen compounds stored in the water bottom oxidized and acidified the water. The conservation value declined sharply but increased again until the 1990s, partly due to the decrease in acidifying deposition. Although the acid atmospheric deposition continued to decline until the early 21th century, the conservation value declined again, as did the stability of the desmid assemblages. It is likely that internal eutrophication (nutrients), presence of toxic substances (such as hydrogen sulphide), the decline of aquatic macrophytes (substrate), shading by afforestation (light) and/or reduced supply of carbon dioxide (due to decreased local seepage) play a role. The chemical dynamics due to the large stock of sulphur and nitrogen compounds will hamper the development of rare desmids, bound to stable environmental conditions.

Grassification and Fast-Evolving Fire Connectivity and Risk in the Sonoran Desert, United States

In the southwestern United States, non-native grass invasions have increased wildfire occurrence in deserts and the likelihood of fire spread to and from other biomes with disparate fire regimes. The elevational transition between desertscrub and montane grasslands, woodlands, and forests generally occurs at ∼1,200 masl and has experienced fast suburbanization and an expanding wildland-urban interface (WUI). In summer 2020, the Bighorn Fire in the Santa Catalina Mountains burned 486 km2and prompted alerts and evacuations along a 40-km stretch of WUI below 1,200 masl on the outskirts of Tucson, Arizona, a metropolitan area of >1M people. To better understand the changing nature of the WUI here and elsewhere in the region, we took a multidimensional and timely approach to assess fire dynamics along the Desertscrub-Semi-desert Grassland ecotone in the Catalina foothills, which is in various stages of non-native grass invasion. The Bighorn Fire was principally a forest fire driven by a long-history of fire suppression, accumulation of fine fuels following a wet winter and spring, and two decades of hotter droughts, culminating in the hottest and second driest summer in the 125-yr Tucson weather record. Saguaro (Carnegia gigantea), a giant columnar cactus, experienced high mortality. Resprouting by several desert shrub species may confer some post-fire resiliency in desertscrub. Buffelgrass and other non-native species played a minor role in carrying the fire due to the patchiness of infestation at the upper edge of the Desertscrub biome. Coupled state-and-transition fire-spread simulation models suggest a marked increase in both burned area and fire frequency if buffelgrass patches continue to expand and coalesce at the Desertscrub/Semi-desert Grassland interface. A survey of area residents six months after the fire showed awareness of buffelgrass was significantly higher among residents that were evacuated or lost recreation access, with higher awareness of fire risk, saguaro loss and declining property values, in that order. Sustained and timely efforts to document and assess fast-evolving fire connectivity due to grass invasions, and social awareness and perceptions, are needed to understand and motivate mitigation of an increasingly fire-prone future in the region.

Surface runoff and losses of phosphorus from hydrophobic pastoral soils

The impact of soil water repellency (SWR) on soil phosphorus (P) mobility in surface water runoff remains contentious. Although SWR may cause a significant increase in surface runoff, especially in post-summer rainfall events, whether it contributes to background phosphorus losses remains unclear. Surface runoff and P concentrations in runoff were measured on hilly Allophanic pastoral soils with different water repellency levels using seven runoff collectors. Phosphorus fertilizer was broadcasted at 18 kg P ha−1 in the summer over dry soils. Runoff volumes and P concentrations were measured after each natural rain event prompting surface runoff. The highest runoff/rainfall ratios were observed at the early rainfall events following the dry summer and then decreased significantly by the end of autumn and winter. The post-summer surface runoff correlation with SWR had an R2 of 0.46, and hydrophobic soils had significantly higher runoff ratios than wettable soils. Measurements of the dissolved reactive phosphorus (DRP) and total phosphorus (TP) in the surface runoff showed decreasing exponential trends, with the highest values recorded in the first runoff event following P fertilizer application, where over 90% of losses occurred (incidental losses). After the incidental loss phase, DRP concentrations were related to surface runoff ratio, soil P extractability by water, and SWR. Our data point to non-incidental TP loads being related to SWR (R2 = 0.53). The present results will improve the understanding of the SWR effect on surface runoff and will reconcile the controversy regarding its contribution to non-incidental P losses.

Vulnerability of European ecosystems to two compound dry and hot summers in 2018 and 2019

Abstract. In 2018 and 2019, central Europe was affected by two consecutive extreme dry and hot summers (DH18 and DH19). The DH18 event had severe impacts on ecosystems and likely affected vegetation activity in the subsequent year, for example through depletion of carbon reserves or damage from drought. Such legacies from drought and heat stress can further increase vegetation susceptibility to additional hazards. Temporally compound extremes such as DH18 and DH19 can, therefore, result in an amplification of impacts due to preconditioning effects of past disturbance legacies. Here, we evaluate how these two consecutive extreme summers impacted ecosystems in central Europe and how the vegetation responses to the first compound event (DH18) modulated the impacts of the second (DH19). To quantify changes in vegetation vulnerability to each compound event, we first train a set of statistical models for the period 2001–2017, which are then used to predict the impacts of DH18 and DH19 on enhanced vegetation index (EVI) anomalies from MODIS. These estimates correspond to expected EVI anomalies in DH18 and DH19 based on past sensitivity to climate. Large departures from the predicted values can indicate changes in vulnerability to dry and hot conditions and be used to identify modulating effects by vegetation activity and composition or other environmental factors on observed impacts. We find two regions in which the impacts of the two compound dry and hot (DH) events were significantly stronger than those expected based on previous climate–vegetation relationships. One region, largely dominated by grasslands and crops, showed much stronger impacts than expected in both DH events due to an amplification of their sensitivity to heat and drought, possibly linked to changing background CO2 and temperature conditions. A second region, dominated by forests and grasslands, showed browning from DH18 to DH19, even though dry and hot conditions were partly alleviated in 2019. This browning trajectory was mainly explained by the preconditioning role of DH18 on the impacts of DH19 due to interannual legacy effects and possibly by increased susceptibility to biotic disturbances, which are also promoted by warm conditions. Dry and hot summers are expected to become more frequent in the coming decades, posing a major threat to the stability of European forests. We show that state-of-the-art process-based models could not represent the decline in response to DH19 because they missed the interannual legacy effects from DH18 impacts. These gaps may result in an overestimation of the resilience and stability of temperate ecosystems in future model projections.

КАЧЕСТВО ЗЕРНА НОВЫХ ГЕНОТИПОВ ОЗИМОЙ ПШЕНИЦЫ

The research on genotypes of soft winter wheat was carried out in “North CaucasusFederal Agrarian Research Centre” in order to study and identify their prospects as a sourcematerial in wheat breeding. The climate of the research area is moderately continental withhot and dry summers. The soil of the experimental area is slightly humic, medium loamordinary chernozem with medium humus layer thickness. The study material was 15 lines ofsoft winter wheat. As a result of this research, 4 winter wheat lines with the highest rates oftotal vitreousness (43-44,5%) were identified: 21378, 21242, 21963, 20029. Lines 20029 and21728 formed more than 23% of gluten, the 1st group , which is the 3rd degree of quality. Thelines studied showed different rates of flour strength by its swelling in acetic acid solution.Lines 21420, 21663, 21683, 21118, 21944, 21924 are classified as strong wheat – 52-54.5 ml.The genotypes isolated by complex of traits can be used as sources of high quality grain whendeveloping new varieties of soft winter wheat for regions with a dry grain-filling period.

Extensive rain events have a more substantial impact than advanced effluent treatment on the endocrine-disrupting activity in an effluent-dominated small river

Wastewater treatment plants (WWTPs) remain an important primary source of emission for endocrine-disrupting compounds in the environment. As an advanced wastewater treatment process, ozonation is known to reduce endocrine-disrupting activity. However, it remains unclear to which extend improved wastewater treatment may reduce the endocrine-disrupting activity in the receiving water body. The present study investigated possible factors for the endocrine-disrupting activity in a small receiving water body, the Wurm River (North-Rhine Westphalia, Germany), up- and downstream of a local WWTP. The cell-based reporter gene CALUX® assay was applied to identify the endocrine-disrupting activity in the water, sediment, and suspended particulate matter. The water phase and the effluent sampling were primarily driven by applying the full-scale effluent ozonation (sampling campaigns in June 2017 and March 2019). In contrast, the sediment sampling aimed to compare the particle-bound endocrine-disrupting activity during dry (June 2017) and rainy summer (June 2018) seasons. The water phase showed low to moderate estrogenic/antiandrogenic activity. Advanced effluent treatment by ozonation led to a complete reduction of the endocrine-disrupting activity according to the limit of detection of the CALUX® assays. The suspended particulate matter originated from the water phase of the second sampling campaign revealed antiandrogenic activity only. Sediments at the sampling sites along the local WWTP revealed higher estrogenic and antiandrogenic activity after extensive rain events and were not affected by the ozonated effluent. Fluctuation patterns of the endocrine-disrupting activity in sediments were in line with fluctuated concentrations of polycyclic aromatic hydrocarbons. Rainwater overflow basin release was suggested as a vector for particle-bound and dissolved endocrine-disrupting activity in the receiving water body. The present study underlined the necessity for monitoring both water and sediment phases to achieve reliable profiling of the endocrine-disrupting activity. The receptor-mediated CALUX® assays were proven to be suitable for investigating the endocrine-disrupting activity distribution in different river compartments and WWTP effluents.

Seasonal variation in reversal learning reveals greater female cognitive flexibility in African striped mice

Cognitive flexibility describes the ability of animals to alter cognitively mediated behaviour in response to changing situational demands, and can vary according to prevailing environemental conditions and individual caracteristics. In the present study, we investigated (1) how learning and reversal learning performance changes between seasons, and (2) how cognitive flexibility is related to sex in a free-living small mammal. We studied 107 African striped mice, Rhabdomys pumilio, in an arid semi-desert, 58 during the hot dry summer with low food availability, and 49 during the cold wet winter with higher food availability. We used an escape box task to test for learning and reversal learning performance. We found that learning and reversal learning efficiency varied seasonally by sex: females tested in summer were faster at solving both learning and reversal tasks than males tested in winter. Performance varied within sex: males tested in winter showed faster learning compared to males tested in summer. During reversal learning, females tested in summer were more efficient and solve the task faster compared to females tested in winter. We suggest that seasonal cognitive performance could be related to sex-specific behavioural characteristics of the species, resulting in adaptation for living in harsh environmental conditions.

Assessing remote sensing as a tool to monitor hydrological stress in Irish catchments with Freshwater Pearl Mussel populations

The West Coast of Ireland hosts many of the few populations of Freshwater Peal Mussels (FPM) left in Europe. The decline of this keystone species is strongly related to deteriorating hydrological conditions, specifically to the threat of low flows during dry summers. Populations still capable of reproducing require a minimum discharge and flow velocity to support juvenile mussels, or else stress builds up and an entire generation may be lost. Monitoring environmental and hydrological conditions in small and remote FPM catchments is difficult due to the lack of infrastructure. Indices derived from remote sensing imagery can be used to assess hydrological variables at the catchment scale. Here, five indices are tested as possible surrogates for soil moisture and evapotranspiration, based on two relevant land-cover types: open peat habitats (OPH) and forestry. Selected indices are then assessed in their ability to reproduce seasonal patterns and in their response to a severe drought event. The moisture stress index (MSI) and normalized difference vegetation index (NDVI) were found to be the best surrogates for soil moisture and evapotranspiration respectively. Both indices showed seasonality patterns in the two land-cover types, although the variability of MSI was significantly higher. During the 2018 drought, MSI visibly increased only in OPH, while NDVI rose only for forestry. The results suggest that OPH enhances the long-term hydrological resilience of a catchment by conserving water in the peat substrate, while industrial forestry plantations exacerbate the pressure on water during drier periods. This has consequences for river discharge, freshwater biodiversity and specifically for FPM. Implementing these surrogates have the potential to identify land-use management strategies that reduce and even avert the effects of drought on FPM. Such strategies are increasingly necessary in a climate change context, as recurring summer droughts are expected in most of Europe.

Has the risk of a 1976 north‐west European summer drought and heatwave event increased since the 1970s because of climate change?

AbstractIn the summer of 1976, north‐west Europe experienced an exceptional heatwave and drought, which impacted agriculture and public water supply. This study aims to assess how the likelihood of the event in the present‐day climate has changed since 1976 because of climate change. The analysis focuses on the England and Wales region, which was particularly badly impacted. Three key factors contributing to the extreme summer were identified: the dry preceding winter–spring period, the dry summer and the hot summer. Following the principles of event attribution, three methods are used to evaluate the change in event risk: one using observational data, a second using CMIP5 coupled climate models and a third using HadGEM3‐A atmosphere‐only simulations. This is the first time that this method has been used to evaluate how the risk of a historical extreme event has changed since it originally occurred. The results from the three methods agree qualitatively. The probability of a summer at least as hot as 1976 has increased significantly between the 1970s and the present‐day climate (estimated risk ratios 11 (5–95% confidence interval (CI) [7,14]), 9 (CI [4,28]) and 19 (CI [5,25]) based on the three respective methods). In contrast, no significant change in the probability of an extreme dry winter–spring or an extreme dry summer was found. However, the joint probability of an extreme dry winter–spring followed by an extreme hot summer and the probability of an extreme hot and dry summer have both increased significantly between the 1970s and the present day (estimated risk ratios between 5 and 79, and between 3 and 39, respectively). Water resource systems should therefore be robust enough to cope with more frequent occurrences of summers as extreme as 1976.

Drying conditions in Switzerland – indication from a 35-year Landsat time-series analysis of vegetation water content estimates to support SDGs

ABSTRACT Exacerbated by climate change, Europe has experienced series of hot and dry summer since the beginning of the 21st century. The importance of land conditions became an international concern with a dedicated sustainable development goal (SDG), the SDG 15. It calls for developing and finding innovative solutions to follow and evaluate impacts of changing land conditions induced by various driving forces. In Switzerland, drought risk will significantly increase in the coming decades with severe consequences on agriculture, energy production and vegetation. In this paper, we used a 35-year satellite-derived annual and seasonal times-series of normalized difference water index (NDWI) to follow vegetation water content evolution at different spatial and temporal scales across Switzerland and related them to temperature and precipitation to investigate possible responses of changing climatic conditions. Results indicate that there is a small and slow drying tendency at the country scale with a NDWI mean decreasing slope of −0.22%/year for the 23% significant pixels across Switzerland. This tendency is mostly visible below 2000 m above sea level (m.a.s.l.) and in all biogeographical regions. The Southern Alps regions appear to be more responsive to changing drying conditions with a significant and slight negative NDWI trend (−0.39%/year) over the last 35 years. Moreover, NDWI values are mostly a function of temperature at elevations below the tree line rather than precipitation. Findings suggest that multi-annual and seasonal NDWI can be a valuable indicator to monitor vegetation water content at different scales, but other components such as land cover type and evapotranspiration should be considered to better characterize NDWI variability. Satellite Earth Observations data can provide valuable complementary observations for national statistics on the ecological state of vegetation to support SDG 15 to monitor land affected by drying conditions.

Isotope hydrology and water sources in a heavily urbanized stream

AbstractComplex networks of both natural and engineered flow paths control the hydrology of streams in major cities through spatio‐temporal variations in connection and disconnection of diverse water sources. We used spatially extensive and temporally intensive sampling of water stable isotopes to disentangle the hydrological sources of the heavily urbanized Panke catchment (~220 km2) in the north of Berlin, Germany. The isotopic data enabled us to partition stream water sources across the catchment using a Bayesian mixing analysis. The upper part of the catchment streamflow is dominated by groundwater (~75%) from gravel aquifers. In dry summer periods, streamflow becomes intermittent in the upper catchment, possibly as a result of local groundwater abstractions. Storm drainage dominates the responses to precipitation events. Although such events can dramatically change the isotopic composition of the upper stream network, storm drainage only accounts for 10%–15% of annual streamflow. Moving downstream, subtle changes in sources and isotope signatures occur as catchment characteristics vary and the stream is affected by different tributaries. However, effluents from a wastewater treatment plant (WWTP), serving 700,000 people, dominate stream flow in the lower catchment (~90% of annual runoff) where urbanization effects are more dramatic. The associated increase in sealed surfaces downstream also reduces the relative contribution of groundwater to streamflow. The volume and isotopic composition of storm runoff is again dominated by urban drainage, though in the lower catchment, still only about 10% of annual runoff comes from storm drains. The study shows the potential of stable water isotopes as inexpensive tracers in urban catchments that can provide a more integrated understanding of the complex hydrology of major cities. This offers an important evidence base for guiding the plans to develop and re‐develop urban catchments to protect, restore, and enhance their ecological and amenity value.

Documentary evidence of droughts in Sweden between the Middle Ages and ca. 1800 CE

Abstract. This article explores documentary evidence of droughts in Sweden in the pre-instrumental period (1400–1800 CE). A database has been developed using contemporary sources, such as private and official correspondence letters, diaries, almanac notes, manorial accounts, and weather data compilations. The primary purpose is to utilize hitherto unused documentary data as an input for an index that can be useful for comparisons on a larger European scale. The survey shows that eight subperiods can be considered as having been particularly struck by summer droughts, causing concomitant harvest failures and having great social impacts in Sweden. This is the case with 1634–1639, 1652–1657, 1665–1670, 1677–1684, 1746–1750, 1757–1767, 1771–1776, and 1780–1783 CE. Within these subperiods, 1652 and 1657 stand out as particularly troublesome years. A number of data for dry summers are also found for the middle decades of the 15th century, the first decade of the 1500s, and the 1550s.

Shifting seasonal patterns of water availability: ecosystem responses to an unappreciated dimension of climate change.

Seasonal patterns of water availability can differ dramatically among ecosystems, with well-known consequences for ecosystem structure and functioning. Less appreciated is that climate change can shift the seasonality of water availability (e.g. to wetter springs, drier summers), resulting in both subtle and profound ecological impacts. Here we (1) review evidence that the seasonal availability of water is being altered in ecosystems worldwide, (2) explore several mechanisms potentially driving these changes, and (3) highlight the breadth of ecological consequences resulting from shifts in the seasonality of water availability. We conclude that seasonal patterns of water availability are changing globally, but in regionally specific ways requiring more rigorous and nuanced assessments of ecosystem vulnerability as well as the ecological consequences.