Patterns Of Precipitation Variability Research Articles

Comparative analysis of SPI, SPEI, and RDI ındices for assessing spatio-temporal variation of drought in Türkiye

AbstractThis research presents a comprehensive drought analysis using climate data obtained from 219 homogeneously distributed meteorological stations in Türkiye between 1991 and 2022. In this context, Standard Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI) drought indices were used and comparative analysis was made. Türkiye. The study demonstrates that below-normal precipitation over extended periods and increasing temperatures have contributed to the increased frequency of meteorological drought events. Türkiye's topographic conditions, particularly its location in the Mediterranean basin, significantly influence drought occurrences. It is noted that over the past 20 years, Türkiye has been trending towards drier conditions, with rising temperatures reinforcing this trend. The study observes that the moderate drought class range is the most frequently recurring in the SPI, SPEI, and RDI methods utilized. Regarding atmospheric conditions affecting the climate in Türkiye, it is observed that increased drought severity stands out prominently in years when the North Atlantic Oscillation is positive. During these years, increased drought severity is evident in the SPI, SPEI, and RDI indices, particularly in winter and autumn, while a wide area experiences drought effects in the summer months. Long-term analyses emphasize that drought periods occur less frequently but have more prolonged impacts, attributed to variations in precipitation patterns from year to year and the influence of rising temperatures due to global climate change. The potential future increase in drought in the Mediterranean basin due to global climate change and Türkiye's vulnerability to this situation could have adverse effects on water resources, food security, energy sources, and ecosystems.

Linking Dissolved Organic Matter Composition to Landscape Properties in Wetlands Across the United States of America

AbstractWetlands are integral to the global carbon cycle, serving as both a source and a sink for organic carbon. Their potential for carbon storage will likely change in the coming decades in response to higher temperatures and variable precipitation patterns. We characterized the dissolved organic carbon (DOC) and dissolved organic matter (DOM) composition from 12 different wetland sites across the USA spanning gradients in climate, landcover, sampling depth, and hydroperiod for comparison to DOM in other inland waters. Using absorption spectroscopy, parallel factor analysis modeling, and ultra‐high resolution mass spectroscopy, we identified differences in DOM sourcing and processing by geographic site. Wetland DOM composition was driven primarily by differences in landcover where forested sites contained greater aromatic and oxygenated DOM content compared to grassland/herbaceous sites which were more aliphatic and enriched in N and S molecular formulae. Furthermore, surface and porewater DOM was also influenced by properties such as soil type, organic matter content, and precipitation. Surface water DOM was relatively enriched in oxygenated higher molecular weight formulae representing HUPHigh O/C compounds than porewaters, whose DOM composition suggests abiotic sulfurization from dissolved inorganic sulfide. Finally, we identified a group of persistent molecular formulae (3,489) present across all sites and sampling depths (i.e., the signature of wetland DOM) that are likely important for riverine‐to‐coastal DOM transport. As anthropogenic disturbances continue to impact temperate wetlands, this study highlights drivers of DOM composition fundamental for understanding how wetland organic carbon will change, and thus its role in biogeochemical cycling.

Systematic reduction of natural enemies and competition across variable precipitation approximates buffelgrass invasiveness (Cenchrus ciliaris) in its native range.

Invasive grasses cause devastating losses to biodiversity and ecosystem function directly and indirectly by altering ecosystem processes. Escape from natural enemies, plant-plant competition, and variable resource availability provide frameworks for understanding invasion. However, we lack a clear understanding of how natural stressors interact in their native range to regulate invasiveness. In this study, we reduced diverse guilds of natural enemies and plant competitors of the highly invasive buffelgrass across a precipitation gradient throughout major climatic shifts in Laikipia, Kenya. To do this, we used a long-term ungulate exclosure experiment design across a precipitation gradient with nested treatments that (1) reduced plant competition through clipping, (2) reduced insects through systemic insecticide, and (3) reduced fungal associates through fungicide application. Additionally, we measured the interaction of ungulates on two stem-boring insect species feeding on buffelgrass. Finally, we measured a multiyear smut fungus outbreak. Our findings suggest that buffelgrass exhibits invasive qualities when released from a diverse group of natural stressors in its native range. We show natural enemies interact with precipitation to alter buffelgrass productivity patterns. In addition, interspecific plant competition decreased the basal area of buffelgrass, suggesting that biotic resistance mediates buffelgrass dominance in the home range. Surprisingly, systemic insecticides and fungicides did not impact buffelgrass production or reproduction, perhaps because other guilds filled the niche space in these highly diverse systems. For example, in the absence of ungulates, we showed an increase in host-specific stem-galling insects, where these insects compensated for reduced ungulate use. Finally, we documented a smut outbreak in 2020 and 2021, corresponding to highly variable precipitation patterns caused by a shifting Indian Ocean Dipole. In conclusion, we observed how reducing natural enemies and competitors and certain interactions increased properties related to buffelgrass invasiveness.

Glaciological studies in Mexico, 60 years of academic work: A summary

Glaciers have played a very important role in controlling the climate during most of the geologic history of our planet Earth. Of course, the glaciers have always been at higher latitudes (north and south), and some on high-altitude mountains. Current glaciers in Mexico are those inherited from the Last Glacial Maximum, (26000 - 19000 years before the present), increasing in size during the period of the Little Ice Age (1300 to 1850 common era), and they are unique in several ways; they are located at 19° north latitude, and they received snow precipitation from both the Pacific Ocean and the Gulf of Mexico (Atlantic Ocean). Research on glacial chronology, physical glaciology, and glacial geochemistry at Universidad Nacional Autónoma de México has provided valuable information on climate and environmental changes at different time scales, from millennial to decadal, and even annual. The first part of this work deals with the reconstruction of the glacial history in Mexico and establishing a glacial chronology from the Last Glacial Maximum to the Little Ice Age. The second part of this work focuses on monitoring recent changes (the last 60 years, 1960s to 2023) of the glacier extent on Iztaccíhuatl, Popocatépetl, and Citlaltépetl (the three highest mountains in Mexico), as well as having an updated inventory of all the glaciers at those mountains. Changes in glacier extent and thickness of ice are directly related to the increase in air temperature, variation in precipitation patterns, and glacier dynamics on some of the last glaciers of the northern tropics. The third part or this work focuses on a compilation of geochemical data from 17 years (from 2006 to 2013) of sampling ice (shallow ice cores) and snow at Iztaccíhuatl and Citlaltépetl glaciers. This database has the potential for providing interesting and useful information on natural and anthropogenic-induced changes related to the occurrence of heavy metals in tropical glaciers in the northern hemisphere of North America. Black carbon concentrations analyzed in snow and glacier ice, and preliminary data on stable isotopes of Zn, also add information on natural vs. anthropogenic sources of heavy metals in central Mexico.

Nitrogen addition regulates the effects of variation in precipitation patterns on plant biomass formation and allocation in a Leymus chinensis grassland of northeast China.

Global warming is predicted to change precipitation amount and reduce precipitation frequency, which may alter grassland primary productivity and biomass allocation, especially when interact with other global change factors, such as nitrogen deposition. The interactive effects of changes in precipitation amount and nitrogen addition on productivity and biomass allocation are extensively studied; however, how these effects may be regulated by the predicted reduction in precipitation frequency remain largely unknown. Using a mesocosm experiment, we investigated responses of primary productivity and biomass allocation to the manipulated changes in precipitation amount (PA: 150mm, 300mm, 450mm), precipitation frequency (PF: medium and low), and nitrogen addition (NA: 0 and 10 g N m-2 yr-1) in a Leymus chinensis grassland. We detected significant effects of the PA, PF and NA treatments on both aboveground biomass (AGB) and belowground biomass (BGB); but the interactive effects were only significant between the PA and NA on AGB. Both AGB and BGB increased with an increment in precipitation amount and nitrogen addition; the reduction in PF decreased AGB, but increased BGB. The reduced PF treatment induced an enhancement in the variation of soil moisture, which subsequently affected photosynthesis and biomass formation. Overall, there were mismatches in the above- and belowground biomass responses to changes in precipitation regime. Our results suggest the predicted changes in precipitation regime, including precipitation amount and frequency, is likely to alter primary productivity and biomass allocation, especially when interact with nitrogen deposition. Therefore, predicting the influence of global changes on grassland structure and functions requires the consideration of interactions among multiple global change factors.

Performance Study of the Al Hoceima Seawater Desalination Plant

The growing demand for freshwater, amplified by climate change, can lead to variations in precipitation patterns and cause more frequent and severe droughts, reinforcing the need for seawater desalination to meet these growing needs. Seawater desalination has become a vital solution in many countries, notably Morocco, which has launched an ambitious program to install seawater desalination plants using the reverse osmosis technique in semi-arid zones. The AL HOCEIMA seawater desalination plant came on stream in June 2020. To keep the plant running smoothly and assess the efficiency of all its operational processes, operating indicators for each treatment process were monitored and compared with expected performance. The results of the evaluation showed that the plant is performing well in terms of producing dimenarilated water by reverse osmosis, and this is due to the adequate pre- treatment adopted by the plant. However, optimizing the remineralization of desalinated water still poses a problem in terms of alkalinity and hardness. Treated water always has an aggressive, corrosive character.

Cover crop performance under a changing climate in continuous corn system over Nebraska.

Fall-planted cover crop (CC) within a continuous corn (Zea mays L.) system offers potential agroecosystem benefits, including mitigating the impacts of increased temperature and variability in precipitation patterns. A long-term simulation using the Decision Support System for Agrotechnology Transfer model was made to assess the effects of cereal rye (Secale cereale L.) on no-till continuous corn yield and soil properties under historical (1991-2020) and projected climate (2041-2070) in eastern Nebraska. Local weather data during the historical period were used, while climate change projections were based on the Canadian Earth System Model 2 dynamically downscaled using the Canadian Centre for Climate Modelling and Analysis Regional Climate Model 4 under two representative concentration pathways (RCP), namely, RCP4.5 and RCP8.5. Simulations results indicated that CC impacts on corn yield were nonsignificant under historical and climate change conditions. Climate change created favorable conditions for CC growth, resulting in an increase in biomass. CC reduced N leaching under climate change scenarios compared to an average reduction of 60% (7kg ha- 1 ) during the historical period. CC resulted in a 6% (27mm) reduction in total water in soil profile (140cm) and 22% (27mm) reduction in plant available water compared to no cover crop during historical period. CC reduced cumulative seasonal surface runoff/soil evaporation and increased the rate of soil organic carbon buildup. This research provides valuable information on how changes in climate can impact the performance of cereal rye CC in continuous corn production and should be scaled to wider locations and CC species.

Reconstruction of climate-induced environmental changes in the eastern Gulf of Mexico based on foraminifera sediment assemblages

Foraminifera assemblages are powerful bioindicators of environmental change and were analyzed in a sediment core collected from the Marquesas Keys, located in the southwestern region of the Florida Keys. The composition and abundance of foraminifera tests within the top 85 cm of the sediment core, dated with 14C and 210Pb, revealed changes in foraminifera assemblages in 1990 CE, 1939 CE, and 1872 CE. Based on the ecological preferences of the dominant species, changes in salinity and submerged aquatic vegetation (SAV) cover may have influenced foraminifera species composition. These changes were likely caused by variation in precipitation patterns in the eastern Gulf of Mexico region associated with shifts in the major ocean-atmosphere teleconnections such as the El Niño Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO) along with tropical storms and hurricanes. Prolonged periods of the negative phases of these climate phenomena coincided with shifts in foraminifera assemblages. Despite a generally negative impact of the ocean-atmosphere teleconnections on the South Florida region, a well-developed epiphytic assemblage was recorded in the studied core. The assemblage was recorded in the uppermost part of the core and dated to the period between 1990 and 2010 CE. This implies that a dense SAV community was present within the Marquesas Keys Mooney Harbor since at least the early 1990.

Contrasting impacts of climate warming on Himalayan Hemlock growth: Seasonal and elevational variations

Ongoing climate change can have varying impacts on tree growth within the growing season and across their elevation ranges, with important implications for forest ecosystem functions and services. However, our knowledge of these effects on climate-sensitive Himalayan forests is still limited. Here, we explore the elevational changes in climatic factors driving long-term changes in the radial growth of Himalayan Hemlock (Tsuga dumosa), including recent responses to unprecedented climate warming in the central Himalayas. We evaluated several growth parameters, including total ring width, earlywood width, adjusted latewood width, and maximum latewood density, in unique > 400-year-old forests along an elevational gradient of 2500–3100 m on the southern slopes of Dhaulagiri, Nepal. Our findings show that changing climatic conditions, characterized by increasing temperatures and variable precipitation patterns, had a more detrimental effect on Tsuga growth at the edge of its elevation range compared to the optimal mid-elevation zone. Specifically, at lower elevations, the combination of spring and preceding autumn warming restricted earlywood growth, while warmer temperatures in late summer stimulated growth at the mid-elevation site by alleviating the cool growth-limiting conditions caused by high monsoonal precipitation. Furthermore, increased spring temperatures enhance latewood density, while summer warming promotes latewood growth at higher elevations. Additionally, we observed that the recent rise in autumn temperatures has begun to impede Tsuga growth across all elevations. In conclusion, our study reveals that the growth of Tsuga trees is influenced by multiple climatic factors that vary within the growing season and across different parts of its elevation range. Recent spring warming has constrained growth in lower elevations, while higher previous autumn temperatures have reduced growth at both higher and lower boundaries of the species' range. These findings contribute to a better understanding of the complex relationship between climate change and tree growth dynamics, particularly in vulnerable Himalayan forests.

Phenological development of subterranean clover (Trifolium subterraneum L.) in New Zealand in response to different climate change scenarios

Climate predictions for New Zealand for the coming decades suggest rising temperatures (+0.7–3 °C), increased diurnal temperature and variable precipitation patterns that differ around the country and with seasons. The most common pattern of annual precipitation indicates the largest increases in the west of the South Island and the largest decreases in the east of the North Island and coastal Marlborough. The phenophases of subterranean clover were estimated and quantified using a thermal time-based model under different climate scenarios based on greenhouse gases and aerosol pathways over the 21st century, known as the Representative Concentration Pathways (RCPs), at two periods (mid and end of the century). The estimated flowering (R3) and post- flowering (R6-R11) date change showed a consistent trend across all districts. The largest date advances (≥ 5 days) were predicted for the three current latest flowering districts (Mackenzie, Queenstown and Central Otago). A reduction of the plant’s life cycle, for both ‘Early’ and ‘Late’ maturity cultivars may have undesired consequences for forage yield so genetic material with later flowering dates may be useful. Adaptation strategies to mitigate the future warming effects include using ‘Late’ flowering cultivars and greater use of supplementary feed through summer dry conditions.

Exploring the relationship between droughts and rural-to-urban mobility—a mixed methods approach for Pune, India

Urbanization in the global South is intricately linked with the internal mobility of people and the impacts of climate change. In India, changing precipitation patterns pose pressure on rural livelihoods through the increasing frequency and severity of droughts, contributing to rural-to-urban mobility. At destination, however, insufficient information is available on the complex mobility backgrounds of the new arrivals. We employ a mixed methods approach to investigate mobility patterns to Pune, India, with a special focus on the role of droughts. Combining a household survey with in-depth interviews and monthly precipitation data on district level, we use descriptive statistics and qualitative content analysis to show a significant relationship between drought at origin and mobility to Pune. Particularly affected are recent arrivals, migrants of rural origin and from other states, and those currently living in informal areas. The link between droughts and mobility decisions is usually indirect, hidden behind economic conditions such as the loss of agricultural jobs. Paradoxically, migrants affected by droughts at origin face increased flood risk at destination. This risk, however, is often consciously taken in favor of better livelihood opportunities in the city. With climate scenarios projecting increasingly variable precipitation patterns, understanding the climate-mobility-urbanization nexus gains importance, especially for destination hotspots like the city of Pune.

Climate and fire impacts on tree recruitment in mixed conifer forests in Northwestern Mexico and California.

Frequent-fire forests were once heterogeneous at multiple spatial scales, which contributed to their resilience to severe fire. While many studies have characterized historical spatial patterns in frequent-fire forests, fewer studies have investigated their temporal dynamics. We investigated the influences of fire and climate on the timing of conifer recruitment in old-growth Jeffrey pine-mixed conifer forests in the Sierra San Pedro Martir (SSPM) and the eastern slope of Sierra Nevada. Additionally, we evaluated the impacts of fire exclusion and recent climate change on recruitment levels using statistical models with realized as well as fire suppression and climate change free counterfactual scenarios. Excessive soil drying from anthropogenic climate change resulted in diminished recruitment in the SSPM but not in the Sierra Nevada. Longer fire-free intervals attributable to fire suppression and exclusion resulted in greater rates of recruitment across all sites but was particularly pronounced in the Sierra Nevada where suppression began > 100 years ago and recruitment was 28 times higher than the historical fire return interval scenario. This demonstrates the profound impact of fire's removal on tree recruitment in Sierra Nevada forests even in the context of recent climate change. Tree recruitment at the SSPM coincided with the early Twentieth Century North American Pluvial, as well as a fire quiescent period in the late 18th and early 19th centuries. Episodic recruitment occurred in the SSPM with no 'average' recruitment over the last three centuries. We found that temporal heterogeneity, in conjunction with spatial heterogeneity, are critical components of frequent-fire adapted forests. Episodic recruitment could be a desirable characteristic of frequent-fire adapted forests and this might be more amenable to climate change impacts that forecast more variable precipitation patterns in the future. One key to this outcome would be for frequent-fire to continue to shape these forests versus continued emphasis on fire suppression in California.

Adaptive nitrogen inputs sustain water-nitrogen use and improve maize productivity with varied precipitation conditions on a semi-arid agroecosystem.

Maize productivity in semi-arid regions is increasingly at risk because of the sparse and uneven precipitation, and it is also restricted by excessive or insufficient fertilization management strategies. A 4-year (2016-2019) field experiment was therefore conducted to show the effects of fertilizer with five nitrogen levels (0, 75-90, 150-180, 270, and 360 kg ha-1 , represented as N0 , N75-90 , N150-180 , N270 , N360 , respectively) under two variable precipitation patterns (rainy at pre-anthesis in 2016 and 2018 versus dry at pre-anthesis in 2017 and 2019) on soil water storage (SWS), water use efficiency (WUE), nitrogen use efficiency (NUE), and maize yield in the Loess Plateau. Nitrogen inputs increased the amount of above-ground dry matter and the WUE for dry matter (WUEd). Dry years at pre-anthesis significantly reduced dry matter accumulation and kernel number per plant. However, soil water storage before sowing (SWSs) decreased from 440 mm in 2016 to 384 mm in 2019, and the increase in fertilization resulted in the water imbalance. Both the maximum grain yield and WUE for grain yield were found in N270 under rainy years at pre-anthesis, whereas in N150-180 under dry years at pre-anthesis. The average nitrogen recovery efficiency (NRE),nitrogen agronomy efficiency(NAE) and nitrogen partial factor productivity (NPFP) decreased with increases in N application, compared with N360 , the NRE,NAE and NPFP of N150-180 increased by 63.5%, 189.2% and 135.5%, respectively. Reducing basal N fertilizers could enhance maize yield and maintain moderate water and nitrogen productivity in years with less rainfall. © 2023 Society of Chemical Industry.

Seasonal variations in surface processes and hydroclimate on an alpine lake, NE Tibetan Plateau

Koucha Lake, located in Qinghai Province, north-eastern Tibetan Plateau (NETP) at an elevation of 4530 m a.s.l. Occupies an ideal position to investigate the seasonal hydroclimatic variations and related surface processes during the Holocene. We re-investigated the lake and analysed a new sediment core from the deepest part of the lake. Grain size measurements and related endmember modelling analyses (EMMA) in combination with ostracod associations together with geochemical parameters and mineral compositions from core sediments were used as relevant proxies for hydro-climatic reconstruction.A comparison of δ18O/δD from various waters on the NETP indicates a clear depleted isotopic signature of non-monsoon moisture supply in comparison to summer rainfalls, highlighting the summer evaporation for δ18O enrichment, as a reference for interpreting δ18O values from lake sediments for various situations of hydrological balance. Based on the individual core chronology the multi-proxy data indicate a very low sedimentation rate over the entire period in accordance with the catchment topography and the absence of well-developed and constant river systems, limiting the flux of sediment supply to the lake. Thus, Koucha Lake remains almost a closed system since the Lateglacial, except for the early mid-Holocene part of the sequence. The coarser particle components and their representative endmembers for spring flood and permafrost thaw between 11.9 and 10.1 cal Ka BP and from 4.5 to ca. 1.0 cal Ka BP point to lower lake levels, influenced by long winter duration with dry summer interruptions, and lighter oxygen isotopes were preserved at low evaporations. Fine-grained sediments supplied by permafrost thaw associated with activating summer surface erosion led to lake level rise between 10.1 and 4.5 cal Ka BP and during the last 1000 years, with a maximum during 7.6–7.1 cal Ka BP. Their enriched δ18O values indicate extended summer duration and concomitant evaporation enhancement, albeit a positive hydrological balance. We suggest that the interannual latitudinal shifts of the intertropical convergence zone (ITCZ) and westerly Jet and attendant varying monsoon rain belt locations are responsible tracers for the variation of the hydrological budget of the lake and the variable spatio-temporal precipitation patterns in humid and (semi) arid regions in China.

Spatial variation in specific sediment yield along the Peruvian western Andes

The tropical Andes has been less studied in terms of erosion processes in comparison to other major mountain ranges in the world. Environmental gradients are steepest along the western flank of the Andes that is characterized by marked differences in vegetation, rough topography with deeply incised canyons, and highly variable and extreme precipitation patterns. Previous efforts mostly focused on sediment fluxes in large rivers draining to e.g. the Amazon basin while small to medium-sized rivers such as the ones flowing towards the Pacific Ocean have been relegated. They highlighted the link between sediment yield, anthropogenic and natural factors, e.g. climate, topography, river runoff, lithology and vegetation cover.In this study, we identified the spatial patterns of specific sediment yield along the western slopes of the Peruvian Andes between 3° and 13° S latitude for 21 catchments. We collected and analysed data from 22 environmental factors to elucidate their importance on spatially varying sediment yield. The sediment load was derived from gauging stations, reservoir sedimentation and water turbidity over a 30-yr period. The specific sediment yield varies strongly along the Peruvian western Andes as a consequence of the spatial variation in climate, topography and land cover controlling sediment production and transport. We reported higher-than-average specific sediment yields for the central part (6°-11°S) with values of 2130 and 2300 t km−2 yr−1 and low and uniform yields of 39 to 551 t km−2 yr−1 in the southern part (11° − 14.5° S). Given the scarcity of data on sediment yield, we included an uncertainty assessment based on bootstrapping approaches as to get a better grasp on the potential range of specific sediment yields in the study region. Using statistical techniques including Spearman correlation rank, univariate and multivariate regression analyses, we were able to determine the importance of the 22 environmental variables on the specific sediment yield. About 55 % of the observed variance can be explained by river discharge (Q90) and river steepness index (ks50). By adding an anthropogenic variable based on land cover, the explained variance in SSY increases up to 63 %, however, the effects of land cover on specific sediment yield are not clear because of spurious correlation between land cover, river discharge and topography. Our study therefore provides important new insights in the ongoing scientific debate on sediment yield variability in the western Andes.

Multivariate and multiharvesting trial for agronomic traits in the genetic resources of guineagrass

AbstractThe diversity and use of forages and grasslands for animal feeding are essential in tropical livestock systems. Seasonal changes are mainly marked by variations in precipitation patterns. Grasslands are managed as perennial crops and therefore must be resilient to tolerate both dry and rainy seasons. The integration of animal production with the genetic aspects of forages is important for helping to identify resilient alternatives for sustainability in livestock systems. This study developed a multivariate and multiharvesting trial (MHT) for plant height, green forage weight (GFW), and dry matter yield (DMY) in a diversity panel of 130 accessions of guineagrass [Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs] established in the Patía Valley of Colombia. Our study aims to identify interactions among weather conditions and different genotypes for agronomic variables as well as identify outstanding accessions for their productivity and adaptability. The entry mean heritability values were .88, .47, and .39 for the traits plant height, GFW, and DMY, respectively. The genetic correlations among different harvests ranged .5–.9 for plant height and .2–.9 for GFW. Heritability and genetic correlations suggest that plant height and yield are largely influenced by plant genetic effects. The correlation among plant height and yield was .42 for GFW and .33 for DMY. Negative correlations were not found in the agronomic behavior of the materials among the harvests under rainy and dry conditions. The MHT analyzed under the methodology of factor analysis revealed that accessions 16062 and 6982 stood out consistently for plant height, GFW, and DMY across different harvests. These findings strengthen processes in the search for resilient forages in the transition toward eco‐efficient livestock production and provide knowledge on which agronomic variables and forage materials to select, according to criteria of interest to both producers and plant breeders.

Spatiotemporal characteristics of dry‐wet abrupt alternation events in China during 1960–2018

AbstractThe dry‐wet abrupt alternation (DWAA) can lead to consecutive drought–flood hazards with high socioeconomic losses. Over the past decades, China has suffered huge economic losses of more than $15 billion due to drought and flood hazards. With the rapid socio‐economic development, the damages caused by DWAA are expected to be more serious. However, the spatiotemporal patterns of DWAA were poorly known at the continental scale. In this study, DWAA was identified by the short‐cycle dry‐wet abrupt alternation index (SDWAI) across eight eco‐regions of China from 1960 to 2018. Results showed that DWAA mainly occurred in humid/semihumid region (III), subtropical humid region (V), and tropical humid region (VI). Seasonally, DWAA is mostly concentrated in summer, with the highest frequency in June and July. Meanwhile, 67% of the total DWAA events were observed in nonsummer seasons. From 1960 to 2018, the intensity of dry to wet (DTW) events has increased by 0.015/10 year. The north and west of China (except region III, V, VI, and VII) experienced an increasing trend in DTW intensity, but a decreasing trend in WTD intensity. DWAA events in some parts of China were frequently observed, which was related to the variability in precipitation patterns caused by climate change. The identification of local hotspots and seasonal distribution of DWAA will support decision‐making for warning and mitigating the drought and flood hazards.

Effects of Seasonal Precipitation on the Amount of Seepage-A Case Study of Tunnel 3 of Bazai Irrigation Project Khyber Pakhtunkhwa

Infiltration of water into tunnel within a harsh geological formation is a vital issue in tunnelling. The consequence impacts due to seepage include tunnel rock instability, pore-water pressure impositionand diminution of operational capacity. The spatial variation in rainfall due to climate change intensifies the threat to tunnel stability. Likewise, to understand the impacts of climate change scenarios on the seepage of tunnel 3 of the Bazai irrigation project wasnumerically simulated inSEEP/W software by manipulating the rainfall data. The net annual precipitation is followed by two sets of rainfall data i.e., dry and wet season precipitation depending upon the magnitude of rainfall. The analysis revealed that most of the seepage occurred in the unlined portion. In order to determine the future impacts ofprecipitation on seepage quantity, the wet season precipitation was further increased by 10% and 50% for A1B and B2conditions respectively. The seepage quantity into the tunnel increases with variation in precipitation patterns. To reduce the risk to tunnel stability, the model was also treated with cement-bentonite grout and bentonite slurry containing 6% solids. The performance of both grouting techniques leads to noticeable seepage deduction. The study further suggests that cement-bentonite is more effective in seepage remediation.

Localized carry‐over effects of pond drying on survival, growth, and pathogen defenses in amphibians

AbstractClimate change is increasing variability in precipitation patterns in many parts of the globe. Unpredictable changes in water availability can be particularly challenging for organisms that rely on precipitation‐fed water sources for completing their life cycle, such as many amphibian species. Although developmental plasticity can mitigate the impacts of changing environments for some species, this strategy can come at a cost to other fitness‐linked traits, such as immune function. We investigated localized variation in the capacity to respond to pond drying and evaluated whether developmental responses induced carry‐over effects in disease susceptibility in three leopard frog species (Rana [Lithobates] pipiens and Rana sphenocephala; two populations each, and one population of Rana chiricahuensis). Using mesocosms located near the site of collection (<15 km away) in five regions spanning a latitudinal gradient, we raised tadpoles under simulated fast drying, slow drying, or constant water levels. After metamorphosis, we characterized several aspects of the skin microbiome, immune function, and response to exposure to the fungal pathogen Batrachochytrium dendrobatidis (Bd). Note that for R. chiricahuensis, the only carry‐over effect measured was response to Bd exposure, for which we observed no effects of pond drying. We found that developmental plasticity in response to drying was rare, except in the southernmost population of R. sphenocephala. In this location, tadpoles responded by accelerating development, and frogs with shorter larval periods developed more severe infections following Bd exposure post‐metamorphosis, suggesting a trade‐off between surviving pond drying and pathogen defense investment. In the three other locations, a lack of accelerated metamorphosis in drying treatments was accompanied by increased mortality, decreased anti‐Bd function of the microbiome, and/or greater Bd infection after exposure. Overall, results suggest that faster drying conditions will likely have negative impacts on amphibians with long larval periods, both directly and indirectly via carry‐over effects. Because effects of drying exposure were not uniform within a species, our findings suggest that local responses may not be generalizable to other regions of the range. These multifaceted effects of climate change on pathogen defenses are increasingly relevant as emerging infectious diseases threaten global biodiversity.

Depositional architecture and aggradation rates of sand-rich, supercritical alluvial fans: Control by autogenic processes or high-frequency climatic oscillations?

Alluvial fans are important paleoclimatic archives, that may record high-frequency climatic oscillations. However, climate signals may be overprinted or even be destroyed by autogenic processes caused by channel avulsion and lobe switching. Here we present new data from two different Late Pleistocene (MIS 3–2) alluvial fan systems in northern Germany and compare these systems to experimental alluvial fans and other field examples. The selected fan systems formed under similar climatic and tectonic conditions, but differ in size, type, and drainage area allowing to estimate the role of climate and autogenic controls on flow processes, facies architecture, and fan-stacking patterns. Luminescence dating is used to determine the timing of fan onset and aggradation. Fan onset occurred in response to climate change at the end of MIS 3 when temperatures decreased and periglacial climate conditions were established in northern central Europe. A related increase in sediment supply and strongly variable precipitation patterns probably promoted fan formation. The major period of fan aggradation was approximately between 33 and 18 ka, followed by fan inactivity, abandonment, and incision during the Lateglacial. The highest aggradation rates occurred during the early stage of fan building, when up to 35 m thick sediment accumulated within a few thousand years. Sand-rich, sheetflood-dominated fans are related to larger, low-gradient fan catchments. Steep depositional fan slopes (5°–17°) and short-lived high-energy floods promoted supercritical flow conditions. Well sorted, sediment-laden, rapidly waning flows favored the deposition and preservation of supercritical bedforms and allowed for the aggradation of stable antidunes. Steep, dip-slope catchments enhanced stream gradients and promoted the transport of coarser sediments. These fans have lower gradient slopes (2–6°) and are dominated by channelized flows, alternating with periods of unconfined sheetfloods. Meter-scale coarsening upward successions, characterized by sandy sheetflood deposits at the base, overlain by multilateral or smaller single-story gravelly channel fills may be related to high-frequency climatic fluctuations or seasonal fluctuations in water and sediment supply. These coarsening-upward successions are commonly bounded by a paleo-active layer, from which ice-wedge casts penetrate downwards. The comparison to experimental fans and other field examples implies that the recurrent pattern of multistory, multilateral and single-story channel bodies with a lateral offset to vertical stacking pattern most probably was controlled by autogenic switch in an avulsion-dominated system. The change in deposition from alluvial-dominated processes to aeolian sedimentation with minor alluvial influences during the Lateglacial records alternation of dry and ephemeral wetter phases that are related to rapid climatic variations. The main phase of aeolian sand-sheet deposition probably correlates with Heinrich event H1 between approximately 18–16 ka and reflects sedimentation in response to aridification and high mean wind speeds.