Dry Spring Research Articles

Prairie Dog (Cynomys ludovicianus) Influence on Forage Quantity and Quality in a Grazed Grassland-Shrubland Ecotone

Black-tailed prairie dogs (Cynomys ludovicianus) have high dietary overlap with livestock, which can cause forage-centric conflicts between agriculture and conservation. Research suggests prairie dogs can enhance forage quality, but trade-offs between quality and quantity throughout the growing season remain unclear, as well as the degree to which increased forage quality is caused by altered species composition versus altered plant physiology. To assess the effects of prairie dog herbivory on forage in a northern mixed-grass prairie, we collected samples on prairie dog colonies and at sites without prairie dogs during June, July, and August 2016 - 2017 for forage quality, and August 2015 - 2017 for herbaceous biomass. To isolate mechanisms affecting forage quality, we collected both composite samples of all herbaceous species and samples of western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve). Across years and plant sample types, crude protein, phosphorus, and fat were 12-44% greater and neutral detergent fiber was 6-10% lower on prairie dog colonies than at sites without prairie dogs. The effects of prairie dogs on forage quality persisted throughout the season for western wheatgrass samples (all treatment*time p-values ≥ 0.4). Across years, aboveground herbaceous biomass did not differ significantly between prairie dog colonies and sites without prairie dogs (on-colony: 933 ± 156 kg/ha, off-colony: 982 ± 117 kg/ha). The effects of prairie dogs on herbaceous biomass were significantly influenced by spring precipitation. In years with dry springs, herbaceous biomass was lower on colonies than sites without prairie dogs and this pattern was reversed in years with wet springs. Our results demonstrate season-long enhanced forage quality on prairie dog colonies, indicating that multiple mechanisms are shaping forage quality in this system, including altered species composition, phenological growth stage, and soil condition. Across years, enhanced forage quality may help to offset reductions in forage quantity for agricultural producers.

Weather fluctuations affect the impact of consumers on vegetation recovery following a catastrophic die-off.

Prolonged droughts exacerbated by climate change have been widely documented to interact with consumers to decimate vegetation in many ecosystems. Although climate change is increasing within-year variation in precipitation and temperature, how weather fluctuations affect the impact of consumers on vegetation processes remains poorly understood. In a salt marsh that has recently experienced drought-associated vegetation die-off, we investigated how top-down control of plant recovery by a prominent salt marsh grazer varies with weather. Our results showed that grazing-driven plant mortality varied strongly with weather in spring, with intense grazing occurring during cool, wet days immediately following rain. Intense grazing on cool, wet days across the generally dry spring season had a strong impact that eliminated plant seedlings that could otherwise have become tolerant of grazing in the following summer, thereby restricting vegetation recovery and contributing to the persistence of an unvegetated salt barren state. Thus, weather fluctuations can modulate the impact of consumers on vegetation recovery, a fundamental process underlying the fate of ecosystems after disturbances. A multi-timescale perspective on top-down control that combines the impact of short-term fluctuations in weather and that of long-term variation in mean climate can not only help understand ecosystem dynamics in an increasingly variable climate, but may also inform conservation strategies or recovery plans for ecosystems that are already lost to climate change.

Moderate water stress does not inhibit nitrogen remobilization, allowing fast growth in high nitrogen content Quercus variabilis seedlings under dry conditions.

Remobilization of stored nitrogen (N) plays an important role in the early growth of deciduous trees in spring. Several environmental factors can modulate N remobilization, but whether water stress is one such factors is unknown. This study analyzes how the size of N storage in Quercus variabilis Blume seedlings interacts with water stress to affect N remobilization, uptake and new growth. This information is important for improving success of forest tree plantations under dry spring conditions. During the first growing season, we produced seedlings with distinct N content by applying two fall N fertilization rates (12 or 24 mg N per seedling) using 15N-enriched fertilizer. At the beginning of the second growing season, a new experiment was started where seedlings were transplanted into larger pots and subjected to two watering levels (85 or 40% of field capacity). The plants were sampled at 4 weeks (T1), 8 weeks (T2) and 12 weeks (T3) after transplanting. Low watering reduced the growth of high and low N seedlings, but high N seedlings showed greater growth than low N seedlings. During bud burst and initial shoot elongation (T1), restricted watering, which induced a moderate water stress, did not affect the amount of N remobilized from roots, the major source of stored N source at this growth stage. This suggests that high N storage can partially counteract the negative effect of moderate water stress on early growth. At T1, water stress did not affect N uptake, and high N content seedlings absorbed significantly less soil N than did low N content seedlings. At T3, in contrast, water stress was the main determinant for N uptake, with drought-stressed plants showing lower uptake than well-watered plants. We conclude that moderate drought does not inhibit N remobilization from the major storage organ at early growth stages in spring, and that increasing N storage of planted seedlings through fall fertilization can mitigate the negative effect of moderate spring drought on growth.

Seasonal Local Temperature Responses to Paddy Field Expansion from Rain-Fed Farmland in the Cold and Humid Sanjiang Plain of China

Numerous studies have documented the effects of irrigation on local, regional, and global climate. However, most studies focused on the cooling effect of irrigated dryland in semiarid or arid regions. In our study, we focused on irrigated paddy fields in humid regions at mid to high latitudes and estimated the effects of paddy field expansion from rain-fed farmland on local temperatures based on remote sensing and observational data. Our results revealed much significant near-surface cooling in spring (May and June) rather than summer (July and August) and autumn (September), which was −2.03 K, −0.73 K and −1.08 K respectively. Non-radiative mechanisms dominated the local temperature response to paddy field expansion from rain-fed farmland in the Sanjiang Plain. The contributions from the changes to the combined effects of the non-radiative process were 123.6%, 95.5%, and 66.9% for spring (May and June), summer (July and August), and autumn (September), respectively. Due to the seasonal changes of the biogeophysical properties for rain-fed farmland and paddy fields during the growing season, the local surface temperature responses, as well as their contributions, showed great seasonal variability. Our results showed that the cooling effect was particularly obvious during the dry spring instead of the warm, wet summer, and indicated that more attention should be paid to the seasonal differences of these effects, especially in a region with a relatively humid climate and distinct seasonal variations.

DEVELOPMENT OF THE CONSERVATIVE VILLAGE MODEL IN THE UPSTREAM BRANTAS RIVER

Water spring (WS) conservation in the upstream area of Brantas River is intended to protect the potency of the main water spring in East Java Province that is being threatened. The threat occurred is caused by a lot of dry water springs, the lowering of river discharge in the dry season, the dam shallowness leading to the flood and the lack of water. Although the conservative activity has involved many agencies, a non-profit organization, local people and the higher education, the achievement rate is still low. The partial activities in the form of the pilot project, in the end, give priority to togetherness that is the establishment of village conservation. The variety of conservative village has been developed by many agencies in accord with the goal and its concept. For the recent time, the conservative village which has been established does not have any capability to take the roll as the pilot that led to the spriit of the other village society conservation. The physical condition variety of the river stream area and social society in upstream Brantas River influence the condition of the conservative village. Therefore, the research is done the research to find the formulation of conservative village condition in upstream Brantas which is conditioned to establish the conservative culture as the implementation of daily activity part. The evaluation result of middle-term village development planning by comparing the conservative need from the analysis shows that conservation has not become the important issue. Therefore it is suggested a regulation to compose village RPJM in order to pay attention to the rules of water spring resources conservaiton. Thus, composed village RPJM, if ti is implemented, will improve the flow coefficient value without decreasing the importance of the other sector development.

Tick-borne disease risk in a forest food web.

Changes to the community ecology of hosts for zoonotic pathogens, particularly rodents, are likely to influence the emergence and prevalence of zoonotic diseases worldwide. However, the complex interactions between abiotic factors, pathogens, vectors, hosts, and both food resources and predators of hosts are difficult to disentangle. Here we (1) use 19yr of data from six large field plots in southeastern New York to compare the effects of hypothesized drivers of interannual variation in Lyme disease risk, including the abundance of acorns, rodents, and deer, as well as a series of climate variables; and (2) employ landscape epidemiology to explore how variation in predator community structure and forest cover influences spatial variation in the infection prevalence of ticks for the Lyme disease bacterium, Borrelia burgdorferi, and two other important tick-borne pathogens, Anaplasma phagocytophilum and Babesia microti. Acorn-driven increases in the abundance of mice were correlated with a lagged increase in the abundance of questing nymph-stage Ixodes scapularis ticks infected with Lyme disease bacteria. Abundance of white-tailed deer 2 yr prior also correlated with increased density of infected nymphal ticks, although the effect was weak. Density of rodents in the current year was a strong negative predictor of nymph density, apparently because high current abundance of these hosts can remove nymphs from the host-seeking population. Warm, dry spring or winter weather was associated with reduced density of infected nymphs. At the landscape scale, the presence of functionally diverse predator communities or of bobcats, the only obligate carnivore, was associated with reduced infection prevalence of I.scapularis nymphs with all three zoonotic pathogens. In the case of Lyme disease, infection prevalence increased where coyotes were present but smaller predators were displaced or otherwise absent. For all pathogens, infection prevalence was lowest when forest cover within a 1km radius was high. Taken together, our results suggest that a food web perspective including bottom-up and top-down forcing is needed to understand drivers of tick-borne disease risk, a result that may also apply to other rodent-borne zoonoses. Prevention of exposure based on ecological indicators of heightened risk should help protect public health.

Extensive gypsy moth defoliation in Southern New England characterized using Landsat satellite observations

Southern New England is currently experiencing the first major gypsy moth (Lymantria dispar) defoliation event in nearly 30 years. Using a novel approach based on time series of Landsat satellite observations, we generated consistent maps of gypsy moth defoliation for 2015 (first year of the outbreak), 2016 (second year of outbreak), and 2017 (third year of outbreak). Our mapped results demonstrate that the defoliation event continued through the 2017 growing season. Moreover, the affected area more than doubled in extent each year and expanded radially to encompass 4386 km2 of forested area in Rhode Island, eastern Connecticut, and central Massachusetts. The current gypsy moth outbreak is believed to be the result of a series of unusually dry springs in 2014, 2015, and 2016, which suppressed Entomophaga maimaiga, a fungal mortality agent that has historically reduced gypsy moth impacts in this region. The continuation and marked expansion of the outbreak in 2017 despite average spring rainfall suggests that caterpillars were active early in the growing season, and mortality from the fungus likely peaked after significant defoliation had already occurred. Our Landsat time series approach represents an important new source of data on spatial and temporal patterns in gypsy moth defoliation, and continued satellite-based monitoring will be essential for tracking the progress of this and other gypsy moth outbreaks.

Effect of tree pruning intensity on the content of mineral components in the sour cherry leaves of ‘Łutówka’

Abstract The aim of the study was to estimate the effect of' tree pruning intensity on the content of nutrients in leaves of the ‘Łutówka’ sour cherry cultivar (Prunus cerasus L.). Between 2006 and 2010 an experiment with different tree pruning intensity was carried out. The study material consisted of first- class one-year old budded plants of the ‘Łutówka’ cultivar IR2 type, on Prunus mahaleb rootstock. The plants were planted in the spring of 2001 (orchard 1) and 2002 (orchard 2) and spaced at 4.0 × 1.3 m2, giving a total of 1.920 trees ha−1. Three pruning regimes were applied in the plantation: 1) no pruning; (only sanitation felling was applied), 2) moderate traditional pruning - branches were shortened, 3) intensive pruning by removing branches older than three years. The cherry tree pruning intensity significantly influenced the content of mineral components in leaves. The content of N increased, whereas the content of Ca and Mg decreased. The maximum temperatures at the beginning of the growth period had particularly beneficial effect on the P and K content. Chilly and dry spring limited the P and K content in the plants. The content of minerals in sour cherry leaves depended on the age of trees.

Use of cast antlers to assess antler size variation in red deer populations: effects of mast seeding, climate and population features in Mediterranean environments

AbstractFundamental understanding of the factors influencing cervid antler size, development and investment has been traditionally drawn from harvest data. However, depending on the hunting tactic, harvest data may not represent a random sample of the population leading to possible inferential biases. Cast antlers may represent an alternative, cost‐effective and non‐invasive method. We used 4756 red deer (Cervus elaphus L.) cast antlers collected during a 10‐year period to evaluate the relationship between annual antler gross score and three key environmental components that determine habitat quality and resource availability in Mediterranean systems: (1) population traits (density and male age structure), (2) acorn yield and (3) a proxy of plant productivity [Real Bioclimatic Index(RBI)]. Population traits and acorn yield were measured before antler formation (autumn/winter) whereas RBI was calculated before (autumn/winter) and during (spring) antler formation. Population traits explained the highest amount of variance in antler score, followed by acorn yield and spring RBI, while no effect was found for autumn/winter RBI. Antler gross score was negatively related to population density but positively associated with acorn yield, spring RBI and male age structure. Interestingly, a significant interaction between population traits and acorn yield suggests a disproportional effect of population traits on antler size during non‐mast years (poor acorn crops), whereas no significant population effect was observed during mast years. Similarly, we found a positive effect of spring RBI on antlers when density was medium or low and/or age structure was balanced or older. These findings have important ecological implications in environments with high inter‐annual resources variability where high population densities lead to strong intraspecific competition during years of low food availability (e.g. during non‐mast years or drier springs), producing large antler size variation. Finally, although cast antlers reflect changes in environmental conditions we do not recommend their use unless reliable data on age structure is available.

UNDERSTANDING FARMERS SEASONAL AND FULL YEAR STALL FEEDING ADOPTION IN NORTHERN ETHIOPIA

Adoption of stall feeding (SF) as well as choices of animals and seasons for its application were assessed in northern Ethiopia in 2015 using a household field survey. The study was conducted in 21 communities to account for differences in agro ecology and to better understand the adoption process. A Heckman selection model was used to estimate adoption and extent of adoption based on a model of technology adoption within an agricultural household framework. A Poisson model was also applied to explain the number of SF adopting seasons. Further a multinomial logit model was estimated in order to reinforce understanding of the choices. The purpose of this study was to understand the driving factors of full or seasonal SF adoption and its intensity as well as animal and seasonal choices. The study results indicate that farmers actually practicing SF in a full year are 36% while those of actual seasonal adopters are 55.6%. The choice of animals allocated to SF include cow (40%), ox (31%) and other animals (29%) of the given sample indicating feeding cow under SF takes the largest share. Similarly, the choice for season were, 65% full year, 29 % wet (summer and autumn) and 6% dry (winter and spring), implying that more than half of the sample farmers practice SF the year round. Empirical results of this study showed that result is in favour of the Boserupian hypothesis indicating that small grazing land and large exclosure are associated with a higher probability of use of SF and with a higher number of SF adopting seasons throughout the year. In a similar vein, small average village farm size stimulated full SF adoption and SF adopting seasons, Availability of labour relative to farm size and a number of breed cows significantly increased the probability of using SF by 0.01% and 66% respectively. While animal shock appeared to have a marginal effect of 14%.The finding also revealed that factors such as access to information and early exposure increased the probability of SF adoption by 18% and 6%. Similarly, the positive marginal effect of real milk price is 15%. However, SF appears to be less attractive to those farmers with more herd size relative farm size and less crop residue. Regarding the intensity of SF adoption, while total labour time, farm size positively affect the extent of SF adoption, total herd size and grazing land ratio negatively influence farmers’ extent of SF adoption in all seasons.

Extreme droughts affecting Mediterranean tree species' growth and water-use efficiency: the importance of timing.

It has been known for a long time that drought intensity is a critical variable in determining water stress of Mediterranean tree species. However, not as much attention has been paid to other drought characteristics, for example the timing of the dry periods. We investigated the impact of the timing and intensity of extreme droughts on growing season length, growth and water-use efficiency of three tree species, Pinus nigra ssp. Salzmannii J.F. Arnold, Quercus ilex ssp. ballota (Desf.) Samp. and Quercus faginea Lam. coexisting in a continental Mediterranean ecosystem. Over the study period (2009-13), intense droughts were observed at annual and seasonal scales, particularly during 2011 and 2012. In 2012, an atypically dry winter and spring was followed by an intense summer drought. Quercus faginea growth was affected more by drought timing than by drought intensity, probably because of its winter-deciduous leaf habit. Pinus nigra showed a lower decrease in secondary growth than observed in the two Quercus species in extremely dry years. Resilience to extreme droughts was different among species, with Q. faginea showing poorer recovery of growth after very dry years. The highest intra- and inter-annual plasticity in water-use efficiency was observed in P. nigra, which maintained a more water-saving strategy. Our results revealed that the timing of extreme drought events can affect tree function to a larger extent than drought intensity, especially in deciduous species. Legacy effects of drought over months and years significantly strengthened the impact of drought timing and intensity on tree function.

Sensitivity of short rotation poplar coppice biomass productivity to the throughfall reduction – Estimating future drought impacts

We examined the effect of throughfall exclusion on aboveground woody biomass (AGB) productivity in a short-rotation woody coppice plantation. This study was carried out between the 3rd and 7th year (2011–2015) of the second rotation cycle in hybrid poplar plantation (Populus nigra × P. maximowiczii) in the Czech Republic. A partial-throughfall exclusion (R) treatment and a control (C) treatment were applied. Throughfall exclusion was set to 40% in 2011–2012 and increased to 70% thereafter. The annual mean (standard error) AGB productivity for C and R during 2012–2015 were 11.2 (0.84) and 10.1 (0.89) Mg ha−1 y−1 of dry matter (DM), respectively. The lowest AGB productivity and most pronounced reduction (18.8%) in the annual AGB productivity by the R treatment occurred in 2014 - a year with the driest spring. The observed inter-annual variability in AGB productivity was not explained by precipitation nor by precipitation-treatment interaction. However, the annual AGB productivity variation depended (p = 0.002) on the throughfall totals during period May–July. The total harvestable biomass in 2015 reached 81.9 (7.2) and 75.0 (6.2) Mg ha−1 DM for the C and R treatments, respectively. Despite the non-negligible mean treatment difference (5.7 Mg ha−1 DM, i.e. 7.6%), the large between-plot variance and shifts in stand structure resulted in the nonsignificant differences. We suggest that once the root system is established, hybrid poplar plantations are relatively resilient to drought and might act as an income-stabilizing factor when traditional agricultural crops fail to deliver viable yields in drier climate.

Decomposing the notion of vine vigour with a proxydetection shoot sensor: Physiocap®

The vigour and the vegetative expression of grapevines are parameters of great interest in viticulture, as they describe a general state of growth capacity. Understanding the impacts of agricultural practices on vine vigour, under particular soil and climate conditions, is essential to give a more accurate technical advice, especially on what soil management and vine nutrition are concerned. A shoot sensor called Physiocap®, designed and developed by the CIVC (Comité interprofessionel du vin de Champagne), is used during dormancy season to measure the shoot section, the shoot number and an estimation of the aboveground biomass. The sensor maps vigour spatial variability within a plot, among plots and over years. Physiocap database in Champagne has been analysed since 2011 at different scales, in order to determine the factors impacting the vine vigour. The vintage appeared to be the most impacting factor. For example, climate variability or accidents like dry springs and early spring frosts reduce vine vigour. Champagne vine varieties did not significantly impact vine vigour according to the database. At the scale of the Champagne vineyard, the aboveground biomass estimation of Physiocap® was strongly correlated with the yield of the following year, leaving a promising basis for analysing the impact of different factors on vine vigour. At the scale of the plot, winegrowers are able to compare their plot vigour to a Champagne threshold, which is being refined every year as the Physiocap database is enriched. They can therefore manage their fertilization and soil tillage program more accurately according to their objectives. The Physiocap® sensor appears to be an interesting multidimensional tool binding vine physiology, agronomy and precision viticulture at different scales. When coupled with other data, especially the one describing soil characteristics, it could even be the baseline for creating a decision-aid tool in Champagne for fertilization, tillage and pruning practices.

Critical temperature and precipitation thresholds for the onset of xylogenesis of Juniperus przewalskii in a semi-arid area of the north-eastern Tibetan Plateau.

The onset of xylogenesis plays an important role in tree growth and carbon sequestration, and it is thus a key variable in modelling the responses of forest ecosystems to climate change. Temperature regulates the resumption of cambial activity, but little is known about the effect of water availability on the onset of xylogenesis in cold but semi-arid regions. The onset of xylogenesis during 2009-2014 was monitored by weekly microcoring Juniperus przewalskii trees at upper and lower treelines on the north-eastern Tibetan Plateau. A logistic regression was used to calculate the probability of xylogenic activity at a given temperature and a two-dimensional reverse Gaussian model to fit the differences between the observed and estimated days of xylogenesis onset at given temperatures and precipitation within a certain time window. The thermal thresholds at the beginning of the growing season were highly variable, suggesting that temperature was not the only factor initiating xylem growth under cold and dry climatic conditions. The onset of xylogenesis was well predicted for climatic thresholds characterized by a cumulative precipitation of 17.0 ± 5.6 mm and an average minimum temperature of 1.5 ± 1.4 °C for a period of 12 d. Xylogenesis in semi-arid regions with dry winters and springs can start when both critical temperature and precipitation thresholds are reached. Such findings contribute to our knowledge of the environmental drivers of growth resumption that previously had been investigated largely in cold regions without water shortages during early growing seasons. Models of the onset of xylogenesis should include water availability to improve predictions of xylem phenology in dry areas. A mismatch between the thresholds of temperature and moisture for the onset of xylogenesis may increase forest vulnerability in semi-arid areas under forecasted warmer and drier conditions.

Climate of seed source affects susceptibility of coastal Douglas‐fir to foliage diseases

AbstractSeed‐source movement trials using common garden experiments are needed to understand climate, tree (host), and pathogen interactions. Douglas‐fir (Pseudotsuga menziesii var menziesii) is an important tree species native to western North America influenced by the foliar fungi Phaeocryptopus gaeumannii, a biotroph and causal agent of Swiss needle cast (SNC), and Rhabdocline species, necrotrophs that cause Rhabdocline needle cast. We used the Douglas‐fir Seed‐Source Movement Trial, a large provenance study of Douglas‐fir that consists of populations and test sites chosen to represent the range of climate conditions experienced by Douglas‐fir west of the Cascade and northern Sierra Nevada Mountains, USA, to assess disease severity and symptom expression in Douglas‐fir in relation to climatic differences between test sites and population sources. Using generalized linear mixed models, probability of disease severity/expression was modeled with respect to the climate variables May through September precipitation (MSP), mean winter temperature (MWT), and continentality. Stark differences in disease expression were observed in trees from different regions, especially in relation to resistance to Rhabdocline spp. and tolerance to P. gaeumannii. There were no major differences across seed‐source regions at any particular site in infection levels of P. gaeumannii assessed by fruiting body abundance, yet disease tolerance followed similar geographic patterns as resistance to Rhabdocline spp. Transfers of populations from low to high MSP, and/or cool to warm MWT, increased the probability of moderate to severe Rhabdocline spp. infection and SNC disease symptoms. Our results suggest that local seed sources are adapted to local climate and pathogen pressures and that seed sources from regions with high foliage disease pressure are most resistant/tolerant to those foliage diseases. We also confirm that temperature and precipitation are important epidemiological factors in forest disease and that assisted migration must take into account trophic interactions of trees. Movement of seed sources from dry spring and summer and/or cool winter conditions to mild, mesic environments is likely to lead to increased probability of losses due to these foliage diseases.

Effect of Spring Precipitation on Summer Precipitation in Eastern China: Role of Soil Moisture

The relation of spring (March–May) to summer (July–August) precipitation in eastern China is examined using observed data. It is found that when spring precipitation from the lower and middle reaches of the Yangtze River valley to northern China (the YRNC region) is higher (lower), more (less) summer precipitation occurs in northeastern China and the lower and middle reaches of the Yangtze River valley, and less (more) in southeastern China. The analysis of physical mechanism showed that higher (lower) spring precipitation in the YRNC region is closely related to wet (dry) spring soil moisture, which decreases (increases) the surface temperature and sensible heat flux in late spring. Because the memory of spring soil moisture in the YRNC region reaches about 2.4 months, the surface thermal anomaly lasts into the subsequent summer, resulting in a weak (strong) East Asian summer monsoon. A weak East Asian summer monsoon corresponds to an anomalous anticyclone and a cyclone over southeastern and northeastern China, respectively, in the lower troposphere. The anomalous anticyclone depresses the summer precipitation in southeastern China, and the anomalous cyclone promotes precipitation over northeastern China. The abnormal northerly and southerly winds associated with the anomalous cyclone and anticyclone, respectively, converge in the lower and middle reaches of the Yangtze River valley, inducing more summer precipitation there.

Space‐Time Patterns of Meteorological Drought Events in the European Greater Alpine Region Over the Past 210 Years

AbstractDroughts may have tremendous impacts on humans. However, the space‐time characteristics of droughts are not very well understood, as case studies usually focus on individual drought events. Here we investigate the spatiotemporal drought characteristics of a large sample of events over the past 210 years in the Greater Alpine Region of Central Europe. We use monthly precipitation data, and flag, for each grid point, time steps with precipitation below a 20% percentile. We then propose a new method that detects drought events by connecting the flagged elements to space‐time drought regions. In contrast to the traditional drought indices that are based on a fixed, prescribed time window, this method is able to identify droughts of different durations in an objective way. The data show multidecadal variations of drought frequency, duration, intensity, and severity, but no consistent trends over the 210 year period. The top 5% of events in terms of their severity show a shift in seasonality from winter/spring events in the late nineteenth century toward autumn events during the last decades of the twentieth century. The most severe events center either in the Northwest or in the Southeast of the region analyzed. We found no significant correlations of drought frequency, duration, intensity, and severity with the temperature increases in the past three decades. Dry springs significantly enhance temperatures during summer droughts, suggesting a soil moisture‐temperature feedback.

Anthropogenic and climatic factors enhancing hypolimnetic anoxia in a temperate mountain lake

Oxygen depletion (temporal or permanent) in freshwater ecosystems is a widespread and globally important environmental problem. However, the factors behind increased hypolimnetic anoxia in lakes and reservoirs are often diverse and may involve processes at different spatial and temporal scales. Here, we evaluate the combined effects of different anthropogenic pressures on the oxygen dynamics and water chemistry of Lake Enol, an emblematic mountain lake in Picos de Europa National Park (NW Spain). A multidisciplinary study conducted over a period of four years (2013–2016) indicates that the extent and duration of hypolimnetic anoxia has increased dramatically in recent years. The extent and duration of hypolimnetic anoxia is typical of meso-eutrophic systems, in contrast with the internal productivity of the lake, which remains oligo-mesotrophic and phosphorus-limited. This apparent contradiction is ascribed to the combination of different external pressures in the catchment, which have increased the input of allochthonous organic matter in recent times through enhanced erosion and sediment transport. The most important among these pressures appears to be cattle grazing, which affects not only the import of carbon and nutrients, but also the lake microbiology. The contribution of clear-cutting, runoff channelling, and tourism is comparatively less significant. The cumulative effects of these local human impacts are not only affecting the lake metabolism, but also the import of sulfate, nitrate- and ammonium-nitrogen, and metals (Zn). However, these local factors alone cannot explain entirely the observed oxygen deficit. Climatic factors (e.g., warmer and drier spring and autumn seasons) are also reducing oxygen levels in deep waters through a longer and increasingly steep thermal stratification. Global warming may indirectly increase anoxia in many other mountain lakes in the near future.

Feedbase intervention in a cow-calf system in the flooding pampas of Argentina: 2. Estimation of the marginal value of additional feed

Temporal variability in the availability of forage reduces the production and economic performance of livestock systems. The marginal value of feed (MVF, the possible gross economic benefit of additional feed on offer during an annual cycle), was assessed under the expected variability of climate and prices in a cow-calf operation from the Flooding Pampas, Argentina. Herbage mass accumulation (HMA) was simulated on a daily basis over 20 different years with DairyMod, grouped by month and season and where the HMA was equal or below 50% of its long-term average, it was tagged as “Dry”. Typical monthly pasture growth rates were synthetically depicted for average years (Average), or with dry autumn (D-Au), winter (D-Wi), spring (D-Sp) or summer (D-Su) conditions. These pasture growth curves were incorporated into whole-farm scenarios which were modelled with SIMUGAN, a bio-economic whole-farm model. Farm scenarios were baseline (unchanged HMA) or with additional 10% of the annual HMA. This additional feed was either evenly distributed across each month of the year (all year), or the full amount provided in one of the four seasons. These scenarios were repeated in a factorial design across a range of stocking rates (SR; 0.9–1.3cows/ha) on an average year or years including one dry season (D-Au, D-Wi, D-Sp orD-Su). SIMUGAN results were fed to an ad-hoc built model to calculate production and market risk profiles. In years with average HMA, MVF were always below 0.05US$/kg DM but the presence of a dry season caused significantly higher MVF. Years with dry autumn presented the highest economic responses when the extra feed was fed during autumn or winter. MVF analyses showed a positive impact of additional forage only above 1.1head/ha and this increased with SR, whereas MVF at the low SR were mostly negative due to extra hay making costs. At 1.1 and 1.2head/ha, allocating additional feed in autumn produced a higher return (0.04 and 0.08US$/kg DM) than feed provided at other times of the year (averaging 0.02 and 0.05US$/kg DM). Otherwise, at 1.3 SR extra feed in winter always had the highest MVF (up to 0.19US$/kg DM). Bio-physical variables of livestock demand and seasonality of pasture growth were the main drivers of MVF variability. Overall, the framework developed by integrating forage, livestock and economic models “in a series” effectively identified the economic feasibility of changes to the farm feed-base under different climatic and livestock management conditions.

Impacts of 1.5 and 2\xa0\xb0C global warming on water availability and extreme hydrological events in Yiluo and Beijiang River catchments in China

In the discussion of climate impacts, 1.5 and 2 °C have become iconic values. This study examines the impacts of 1.5 and 2 °C global warming on water availability, runoff seasonality, and extreme monthly and daily runoff in two catchments, using the semi-distributed hydrological model Hydrologiska Byråns Vattenbalansavdelning-D, based on a combination of five global climate models (GCMs) and four representative concentration pathways (RCPs). Subsequently, quantitative assessments were made for projection uncertainties from GCMs and RCPs. The two catchments are the Yiluo River catchment (YLC) in northern China and the Beijiang River catchment (BJC) in southern China. The results indicate wetter flood seasons for YLC and warmer mean annual temperatures, drier springs, and more severe floods over long return periods (25 and 50 years) for both catchments. The change magnitude of most indicators is expected to be larger in YLC than in BJC. Mean annual temperatures in both catchments are expected to have smaller changes under the 1.5 °C scenario than under the 2.0 °C scenario. However, the change magnitude of the other hydrological variables is projected to be approximately equivalent for both catchments under both scenarios. Uncertainties of projected impacts from GCMs are generally larger than those from RCP scenarios, for both catchments and warming scenarios, with the exception of mean annual temperature of BJC. These findings indicate that effective measures are required to address increasing annual temperatures, more severe flood events (25- and 50-year return periods), and drier spring seasons in both catchments and wetter flood seasons in YLC.