Consecutive Dry Years Research Articles

Fuzzy rule–based control of multireservoir operation system for flood and drought mitigation in the Upper Mun River Basin

Strategic reservoir operation, a primary water management measures, plays a significant role in mitigating floods and droughts. Since the reservoir operation involves making complicated decisions on uncertain hydrological variables driven by climate variability, therefore, constructive tool for decision making like fuzzy logic is essential to optimize reservoir management and ensure water security. This study demonstrated fuzzy logic application to multiple reservoir operation in tropical region like Thailand. A Fuzzy Rule–Based Model (FRBM) exploiting FL approach was developed to control the upstream reservoir operation in the Upper Mun River Basin (UMRB) using the data from 2008 to 2021. Implementing FRBM for UMRB was conducted by identifying two key variables; available water storage and 7–day ahead predicted inflow, as fuzzy inputs. The fuzzy output of the system is the release fraction determined by three operational condition modules; flood, neutral, and drought. For flood module, fuzzy release is primarily determined by the predicted inflow. However, the determination of reservoir release for drought and neutral modules is influenced by the targeted water demand. The results of base case illustrate the capability of FRBM in increasing reservoir storages at the start of dry season by 123.56 MCM/yr in UMRB due to the new daily release schemes generated. This allows supplying water closer to the theoretical agricultural needs and gross irrigation water requirement potentially reducing the risk of water shortfall during consecutive dry years. Whereas, the maximum fuzzy release is constrained corresponding to safe channel capacity of tributaries and Upper Mun river, therefore, downstream flooding is accordingly prevented.

Reason for less water supply shortages under climate change condition: evaluation of future rainfall data

Abstract This study evaluates the appropriateness of general circulation model-based future rainfall data used in Korea. The evaluation is done through the analysis of long-term occurrence characteristics of dry years, as well as the analysis of the water supply system including the daily based rainfall-runoff analysis and reservoir operation. This study considers the Boryeong Dam basin in Korea as a study basin. Summarizing the results is as follows. First, the future rainfall data show that the occurrence frequency of dry years is similar to the observed, but the occurrence frequency of consecutive multi-year dry years is far smaller than the observed. Second, the future rainfall data result in no or far less water supply shortages. This is mainly due to the fact that the Boryeong Dam has the ability to overcome the one-year drought and the future rainfall data contain far fewer multi-year droughts. However, these results clearly indicate the problems of the future rainfall data, especially in the long-term persistence of rainfall. It is thus disappointing that these future climate rainfall data may not be used to evaluate the water supply system in the future, at least in the Boryeong Dam basin.

Impacts of climate variability on the production of Dwarf x Tall and Tall x Tall coconut (Cocos nucifera L.) palm hybrids planted on the coast in Côte d'Ivoire

The Ivorian coast is the main coconut production area where agriculture is mainly rainfed. However, in this area, climate variability poses a great threat to the growth and sustainable development of agriculture. This study aimed at highlighting the impacts of climate variability on the production of the most popular Dwarf x Tall and Tall x Tall coconut palm hybrids in the world. It is based on the evaluation of the production of the hybrids from statistical tests (ANOVA, STUDENT's T-test at 5%) and the results of the standardized precipitation and evapotranspiration indices (SPEI) during the period of 2009 to 2018 of the study area. The results obtained revealed that the NJM×GOA+ hybrid was significantly differentiated by its good production potential of bunches (10 bunches), fruits (151 nuts) and copra (3.69 t). The maximum fruit production per year was observed in the Dwarf × Tall hybrids (101 nuts). The highest mass productions of copra per tree and copra per hectare were recorded in the Tall × Tall hybrids. The maximum productions of the ten hybrids were observed in 2012, 2015 and 2018 and the lowest in 2014 and 2017. Productions gradually increase or remain stable for consecutive wet years (2009 to 2011) prior to harvest. The onset of drought in one year (2012, 2013, 2015, 2016) and pronounced for two consecutive dry years (2012 to 2013 and 2015 to 2016) prior to harvest significantly decrease the level of production. These cumulative effects of drought are most pronounced in NRC×GRL+, NRM×GTN, NJM×GD001, NJM×GD002, and NJM×GD003 hybrids. NJM×GOA+, GVT×GTN, GSL×GTN, NRM×GVT, and NVS×GVT hybrids are developing abilities to express themselves better under this climate variability. They could be taken into account in the crop improvement program and proposed to growers to improve the yield of coconut trees under rainfed conditions.

Hazard Assessment of Drought Using PNPI and GIS in Fars Province, Iran

Drought is among the natural disasters that seriously impact the environment and human life. This study aims to explore the spatial pattern of drought using the percent of normal precipitation index (PNPI) in Fars Province, located in the Southern part of Iran. To this end, a drought risk model based on data from 42 stations in Fars province from 1990 to 2019 was evaluated. The model includes three criteria of maximum drought intensity in the period, drought trend, and a maximum number of consecutive dry years. The final drought risk map was obtained with an arithmetic mean of three indicators of intensity, continuity, and trend. The final hazard map and the 3-criteria map were interpolated by the inverse distance weighting (IDW) method and were classified into five risk classes: none, mild, moderate, severe, and very severe. The final vulnerability map shows that moderate hazard areas (5% of the region), which are observed in the Sothern parts of the region, are less widespread than areas under severe hazard (83% of the region), which are observed in almost all parts of the region. According to the final vulnerability map, about 94% of the area of Fars province is under severe and very severe conditions. Overall, this study, regarding its simplicity and considering different dimensions of drought, may be utilised as a basic framework to evaluate drought hazards for other locations worldwide. In this respect, it is necessary to study the multiple sights of this phenomenon for land use planning, resource management, and prevention of water and food crises. Therefore, this model can help users and administrations with executive initiatives.

Drought Governance in Transition: a Case Study of the Meuse River Basin in the Netherlands

The Netherlands is internationally renowned for its flood risk management, but three consecutive dry years between 2018–2020 fuelled the debate on how to deal with future drought risk. Drought governance in the Netherlands is still in its infancy. The increased sense of urgency has led many scholars and policy makers to call for transitions towards a more anticipatory drought governance which enables transformative actions in an adequate and timely manner. Whilst transitions have been studied before, few have looked at governance systems, and even fewer on the processes that can steer the direction and speed of governance transitions in the future. This paper adopts a novel perspective by combining theories on mechanisms and transitions to analyse future governance transitions. The aim of this study is to identify the key mechanisms that have potential to steer and/or accelerate transitions in Dutch drought governance. This study focusses on the upper part of the Dutch Meuse River basin. Using a document analysis, expert interviews, and focus group discussions, the findings show that five underlying micro-level mechanisms are critical to steer and accelerate transitions. These include social learning, shared problem perception, administrative courage and leadership, persistency, and institutionalisation. The novel transition-mechanistic conceptual approach adopted in this study offers a starting point for other studies that wish to obtain a better understanding of underlying processes in a transition.

How precipitation legacies affect broad-scale patterns of primary productivity: Evidence from the Inner Mongolia grassland

The legacy effects of precipitation, defined as the impact of precipitation from previous years on current-year net primary productivity (NPP), have been well recognized in field experiments and site-level observational studies. However, it remains unclear how consecutive dry or wet years influence the directions and magnitude of legacies and broad-scale patterns of NPP. Here, we quantified the spatial and temporal patterns of legacy effect across different numbers of consecutive wet and dry years from 2000 to 2020 in the Inner Mongolia grassland. Spatially, the response of legacies to precipitation transitions was asymmetric along the mean annual precipitation gradient. The positive response of legacies to precipitation decrease was found for desert steppe and typical steppe after preceding wetness. In contrast, the response of legacies to precipitation increase was negative for desert steppe and meadow steppe after preceding drought. Moreover, legacies were more sensitive in desert steppe than that in typical steppe and meadow steppe for both the preceding wetness and preceding drought. However, the meadow steppe showed the highest response to the inter-annual precipitation change among the three grassland types. Furthermore, the legacies responded more strongly to precipitation decrease (preceding consecutive wet years) than the increase (preceding consecutive dry years) for meadow steppe and typical steppe. Yet, the desert steppe showed the opposite response to precipitation change. Temporally, the legacy effects lasted for only one year and could be transmitted year by year. Our findings highlight that consecutive wet and dry years play essential roles in controlling the NPP responses to climate fluctuations in arid and semi-arid grasslands. Understanding ecosystem responses to climatic periods can provide insights into the effects of directional changes in rainfall associated with climate change.

Annual nitrate load patterns in an agricultural watershed in consecutive dry years

Abstract Nitrate (NO3-N) load characteristics in consecutive dry years in the Huai River Basin (HRB), China, were examined using streamflow and NO3-N concentration data. The data set spanned 12 years including three consecutive dry years. Baseflow separation, load estimation, and nonparametric linear regression were applied to separate point source (PS), baseflow, and surface runoff NO3-N loads from the total load. The mean annual nonpoint source (NPS) load was 2.84 kg·ha−1·yr−1, accounting for 90.8% of the total load. Baseflow contributed approximately one-fourth of the natural runoff and half of the NPS load. The baseflow nitrate index (i.e., the ratio of baseflow NO3-N load to total NPS NO3-N load) was 25.4% higher in consecutive dry years than in individual dry years. This study demonstrated that baseflow is the preferential hydrological pathway for NO3-N transport in the HRB and that baseflow delivers a higher NO3-N percentage to streams under long-term drought than under short-term drought. This study highlights the alarming evidence that continuous drought caused by climate change may lead to a higher rate of nitrogen loss in agricultural watersheds.

Characterization of Groundwater Recharge and Flow in California's San Joaquin Valley From InSAR-Observed Surface Deformation.

Surface deformation in California's Central Valley (CV) has long been linked to changes in groundwater storage. Recent advances in remote sensing have enabled the mapping of CV deformation and associated changes in groundwater resources at increasingly higher spatiotemporal resolution. Here, we use interferometric synthetic aperture radar (InSAR) from the Sentinel‐1 missions, augmented by continuous Global Positioning System (cGPS) positioning, to characterize the surface deformation of the San Joaquin Valley (SJV, southern two‐thirds of the CV) for consecutive dry (2016) and wet (2017) water years. We separate trends and seasonal oscillations in deformation time series and interpret them in the context of surface and groundwater hydrology. We find that subsidence rates in 2016 (mean −42.0 mm/yr; peak −345 mm/yr) are twice that in 2017 (mean −20.4 mm/yr; peak −177 mm/yr), consistent with increased groundwater pumping in 2016 to offset the loss of surface‐water deliveries. Locations of greatest subsidence migrated outwards from the valley axis in the wetter 2017 water year, possibly reflecting a surplus of surface‐water supplies in the lowest portions of the SJV. Patterns in the amplitude of seasonal deformation and the timing of peak seasonal uplift reveal entry points and potential pathways for groundwater recharge into the SJV and subsequent groundwater flow within the aquifer. This study provides novel insight into the SJV aquifer system that can be used to constrain groundwater flow and subsidence models, which has relevance to groundwater management in the context of California's 2014 Sustainable Groundwater Management Act (SGMA).

Biomass Dynamics in a Fragment of Brazilian Tropical Forest (Caatinga) over Consecutive Dry Years

Increases in water scarcity due to climate change, especially in dry regions, can affect the dynamics of successional species. In view of the longest sequence of dry years (2010–2019) to have occurred in the Brazilian semi-arid region, with a consequent reduction in water availability, the influence of rainfall distribution on the production of above-ground plant biomass was investigated in a Dry Tropical Forest (DTF). This natural change monitoring experiment was conducted over 11 years (2009–2019) in a fragment of DTF under regeneration for 40 years, in the district of Iguatu, Ceará, Brazil. All living individuals of the woody component with a Diameter at Ground Level (DGL) ≥3 cm and a height (h) ≥100 cm were measured during 2009–2010, 2015–2016, 2018–2019. Biomass production was calculated using an allometric equation defined for DTF species. A mean mortality rate of 134 ind. ha−1 yr−1 was registered, with a recruitment of 39 ind. ha−1 yr−1, generating a mean deficit of 95 ind. ha−1 yr−1. The mean reduction in biomass was 3.26 Mg ha−1 yr−1. Climate conditions during consecutive dry years have a direct effect on the mortality and recruitment of woody species, with a recruitment/mortality ratio of 0.11. Shrubby-tree individuals of smaller diameter showed less resilience to the cumulative effect of drought.

Severe Drought in the Spring of 2020 in Poland—More of the Same?

Two consecutive dry years, 2018 and 2019, a warm winter in 2019/20, and a very dry spring in 2020 led to the development of severe drought in Poland. In this paper, changes in the Standardized Precipitation-Evapotranspiration Index (SPEI) for the interval from 1971 to the end of May 2020 are examined. The values of SPEI (based on 12, 24 and 30 month windows, i.e., SPEI 12, SPEI 24 and SPEI 30) were calculated with the help of the Penman–Monteith equation. Changes in soil moisture contents were also examined from January 2000 to May 2020, based on data from the NASA Goddard Earth Sciences Data and Information Services Center, presenting increasing water shortages in a central belt of Poland. The study showed that the 2020 spring drought was among the most severe events in the analyzed period and presented decreasing trends of SPEI at most stations located in central Poland. This study also determined changes in soil moisture contents from January 2000 to May 2020 that indicate a decreasing tendency. Cumulative water shortages from year to year led to the development of severe drought in the spring of 2020, as reflected in very low SPEI values and low soil moisture.

Preliminary indications for diverging heat and drought sensitivities in Norway spruce and Scots pine in Central Europe

Massive and increasing tree mortality is currently observed in the two conifer species Norway spruce and Scots pine in Central Europe. Consecutive dry years are made responsible for this phenomenon. Leaf trait measurements, in specific leaf osmotic potential (πosm) and leaf water potential at turgor loss (πtlp), indicate that the underlying mechanisms for tree mortality are most likely different between the two species. πtlp of spruce was highly negative, revealing a potentially high drought tolerance of the species. πtlp of Scots pine was less negative, suggesting a higher susceptibility to drought stress. I conclude that the mortality of Norway spruce might be caused by rising temperatures and that the summer temperatures in the past years were beyond the species thermal tolerance threshold. Overall, I want to highlight and enhance the discussion that the search for suitable species for a climate change adapted forest should go in both directions, i.e., species should be chosen to make the forest fit for both increasing drought and heat stress.

Asymmetric impacts of dryness and wetness on tree growth and forest coverage

The prevalence of legacy effects, especially in drought-prone forests, makes the accurate assessment of forest dynamics under frequent climate fluctuations challenging. Here, we investigated the dynamic impacts of inter-annual water deficit on both tree radial growth and forest coverage in the southwest USA. We designed a series of regional-scaled “natural experiments”, specifically, we preset hypothetical water conditions of current- and antecedent-hydrological years and conducted quantitative analysis on grouped tree-ring records and sub-pixel changes of forest coverage under these conditions. Results showed that the temporal patterns of growth legacy changed dynamically when studying it on multiple events level (i.e., both past and current climate condition are taken into consideration): under current-hydrological year dry conditions, legacy effects over 3 years could be detected; while under current-hydrological year wet conditions, only previous 1 year's legacy could be detected, and its intensity was only 57% of that under current-hydrological year dry conditions. Furthermore, our results revealed that growth dynamics observed in tree rings were not fully consistent with the dynamic of forest coverage. Wetness enhanced growth pronouncedly, whereas normal to wet conditions only barely maintained the stability of forest coverage, suggesting that tree growth is more sensitive to wetness than forest coverage. In addition, the impact of consecutive dry years on tree radial growth showed no significant difference from that of a single dry year, but the decline of forest coverage accelerated after consecutive droughts. A possible explanation is that trees sampled from environmentally harsh locations though climate sensitive are not subjected to strong competitive constraints. These findings suggest that examining the responses at multiple scales in forests can help us gain more comprehensive understanding of processes involved in forest dynamics.

Green manure and phosphorus fertilization affect weed community composition and crop/weed competition in organic maize

AbstractGreen manure and compost-enriched in phosphorus can promote the sustainability of cropping systems by increasing soil fertility over the long term. They can also be used to manage crop/weed interactions, a key element in guaranteeing an appropriate level of satisfactory crop yields. We studied how green manuring with hairy vetch (Vicia villosaRoth.) and the application of different types of phosphorous-enriched compost affect weed/maize (Zea maysL.) interactions in an organic stockless Mediterranean agroecosystem for two consecutive dry years. Green manure stimulated the expression of maize traits related to a higher competitive ability against weeds, such as early growth, height and leaf area index, while the effect of compost was less clear. Regarding crop/weed competition, both green manuring and a phosphorus-enriched compost application gave a significant advantage to maize. Neither green manure nor compost increased total weed density and biomass compared to the control. Green manuring significantly affected the weed community composition. The relative density of ruderal and competitive-ruderal species (according to Grime's classification) was higher in plots where the green manure was applied. The use of green manure, together with novel composting techniques, significantly affected crop/weed competitive interactions, favoring maize, but also creating favorable conditions for unwanted weed species such as competitive-ruderals. Increasing nitrogen availability in the early growth stages of maize through green manuring can increase crop competitive ability. However, this may not suffice to preserve the system from future weed problems, should potentially detrimental species be selected. Dedicated strategies for the control of emerging weed species may thus be needed.

Conservation farming practices in winter wheat–summer maize cropping reduce GHG emissions and maintain high yields

No-till (NT), straw incorporation (SI) and optimized N fertilization are important mitigation options for reducing greenhouse gas (GHG) emissions from agroecosystems. These measures may also help to maintain high crop production and are frequently recommended for use in northern China. Few studies, however, have addressed the interactive effects of these conservation and fertilization practices with respect to GHG emissions and crop yields. We report on a field experiment conducted in two consecutive dry years (2013–2015) when precipitation was much lower than the long-term average. We examined the effects of three different N fertilizer application rates, tillage practice and straw management on crop yields, GHG, area-scaled GHG (in global warming potential) and net ecosystem economic budget (NEEB) of a winter wheat-summer maize rotation system in northern China. Results showed that reducing N fertilizer significantly decreased soil N2O emissions without affecting annual crop yields. Compared with the average of all other fertilization treatments, the no-till × straw incorporation (NT × SI) practice increased both wheat and maize yields. However, in the maize season, NT also increased cumulative N2O emissions compared with conventional tillage (CT). The practices of combining N fertilization with straw management conferred an additional effect on N2O emissions when compared with single practices (i.e. fertilization or straw management). Compared with straw removal (SR) treatments, SI increased annual cumulative N2O emissions by 37% for the conventional N fertilization, but decreased them by 13% at the optimized N fertilization. Neither single practice nor integrated practices had a significant effect on cumulative CH4 uptake. The highest NEEB values were obtained in NT × SI × optimal N fertilization (OPT) and NT × SR × OPT in the 1st and 2nd cropping years, respectively. We conclude that, when considering the additional benefits of SI for improving soil fertility and C sequestration, the NT × SI × OPT practice would be a viable strategy to achieve high crop yields, while simultaneously reducing GHG emissions.

Gene expression profiling of periodontitis-affected gingival tissue by spatial transcriptomics

This study represents the first large-scale systematic dendroclimatic sampling focused on developing chronologies from different species in the eastern Mediterranean region. Six reconstructions were developed from chronologies ranging in length from 115years to 600years. The first reconstruction (18852000) was derived from principal components (PCs) of 36 combined chronologies. The remaining five, 18002000, 17002000, 16002000, 15002000 and 14002000 were developed from PCs of 32, 18, 14, 9, and 7 chronologies, respectively. Calibration and verification statistics for the period 19312000 show good levels of skill for all reconstructions. The longest period of consecutive dry years, defined as those with less than 90% of the mean of the observed MayAugust precipitation, was 5years (15911595) and occurred only once during the last 600years. The longest reconstructed wet period was 5years (16011605 and 17511755). No long term trends were found in MayAugust precipitation during the last few centuries. Regression maps are used to identify the influence of large-scale atmospheric circulation on regional precipitation. In general, tree-ring indices are influenced by MayAugust precipitation, which is driven by anomalous below (above) normal pressure at all atmospheric levels and by convection (subsidence) and small pressure gradients at sea level. These atmospheric conditions also control the anomaly surface air temperature distribution which indicates below (above) normal values in the southern regions and warmer (cooler) conditions north of around 40N. A compositing technique is used to extract information on large-scale climate signals from extreme wet and dry summers for the second half of the twentieth century and an independent reconstruction over the last 237years. Similar main modes of atmospheric patterns and surface air temperature distribution related to extreme dry and wet summers were identified both for the most recent 50years and the last 237years. Except for the last few decades, running correlation analyses between the major European-scale circulation patterns and eastern Mediteranean summer precipitation over the last 237years are non-stationary and insignificant, suggesting that local and/or sub-regional geographic factors and processes are important influences on tree-ring variability over the last few centuries.

Longevity and population age structure of the arroyo southwestern toad (Anaxyrus californicus) with drought implications.

The arroyo southwestern toad is a specialized and federally endangered amphibian endemic to the coastal plains and mountains of central and southern California and northwestern Baja California. It is largely unknown how long these toads live in natural systems, how their population demographics vary across occupied drainages, and how hydrology affects age structure. We used skeletochronology to estimate the ages of adult arroyo toads in seven occupied drainages with varying surface water hydrology in southern California. We processed 179 adult toads with age estimates between 1 and 6 years. Comparisons between skeletochronological ages and known ages of PIT tagged toads showed that skeletochronology likely underestimated toad age by up to 2 years, indicating they may live to 7 or 8 years, but nonetheless major patterns were evident. Arroyo toads showed sexual size dimorphism with adult females reaching a maximum size of 12 mm greater than males. Population age structure varied among the sites. Age structure at sites with seasonally predictable surface water was biased toward younger individuals, which indicated stable recruitment for these populations. Age structures at the ephemeral sites were biased toward older individuals with cohorts roughly corresponding to higher rainfall years. These populations are driven by surface water availability, a stochastic process, and thus more unstable. Based on our estimates of toad ages, climate predictions of extreme and prolonged drought events could mean that the number of consecutive dry years could surpass the maximum life span of toads making them vulnerable to extirpation, especially in ephemeral freshwater systems. Understanding the relationship between population demographics and hydrology is essential for predicting species resilience to projected changes in weather and rainfall patterns. The arroyo toad serves as a model for understanding potential responses to climatic and hydrologic changes in Mediterranean stream systems. We recommend development of adaptive management strategies to address these threats.

Hurry up and wait: life cycle and distribution of an intermittent stream specialist (Mesocapnia arizonensis)

Species inhabiting intermittent streams must have life-history traits that confer resistance or resilience to flow cessation or drying. However, we lack basic life-history information for most aquatic invertebrate species, especially those from intermittent streams. I documented the life cycle and distribution of an unusual winter stonefly species, Mesocapnia arizonensis (Capniidae). The species was first described from 6 localities in 1969, but its natural history remained enigmatic. I surveyed >90 streams across the southwestern USA, documented the life cycle of M. arizonensis at 1 locality, and experimentally rehydrated dry streambed sediment in search of dormant stoneflies at another locality. Field surveys expanded the number of localities from 22 to 98, most of which were intermittent with flow durations as brief as 3 mo/y, and extended the known range of the species by 800 km. Nymphs were abundant within days of flow resumption, grew rapidly as a single cohort, and started emerging as adults 42 d after flow resumed. The brief appearance of a 2nd cohort of tiny nymphs 1 mo before the stream dried indicates direct hatching of at least some eggs. I failed to find dormant stoneflies in the top 30 cm of dry stream sediment, suggesting that M. arizonensis undergoes dormancy deep in the substrate, putting it safely out of reach of scouring summer floods that occur between favorable winter seasons. The remarkable ability of M. arizonensis to survive in short-flow duration streams and to endure multiple consecutive dry years, suggests that the species is well prepared for the drier climatic conditions predicted to occur across its range.

Refining the cheatgrass–fire cycle in the Great Basin: Precipitation timing and fine fuel composition predict wildfire trends

Larger, more frequent wildfires in arid and semi‐arid ecosystems have been associated with invasion by non‐native annual grasses, yet a complete understanding of fine fuel development and subsequent wildfire trends is lacking. We investigated the complex relationships among weather, fine fuels, and fire in the Great Basin, USA. We first modeled the annual and time‐lagged effects of precipitation and temperature on herbaceous vegetation cover and litter accumulation over a 26‐year period in the northern Great Basin. We then modeled how these fine fuels and weather patterns influence subsequent wildfires. We found that cheatgrass cover increased in years with higher precipitation and especially when one of the previous 3 years also was particularly wet. Cover of non‐native forbs and native herbs also increased in wet years, but only after several dry years. The area burned by wildfire in a given year was mostly associated with native herb and non‐native forb cover, whereas cheatgrass mainly influenced area burned in the form of litter derived from previous years’ growth. Consequently, multiyear weather patterns, including precipitation in the previous 1–3 years, was a strong predictor of wildfire in a given year because of the time needed to develop these fine fuel loads. The strong relationship between precipitation and wildfire allowed us to expand our inference to 10,162 wildfires across the entire Great Basin over a 35‐year period from 1980 to 2014. Our results suggest that the region's precipitation pattern of consecutive wet years followed by consecutive dry years results in a cycle of fuel accumulation followed by weather conditions that increase the probability of wildfire events in the year when the cycle transitions from wet to dry. These patterns varied regionally but were strong enough to allow us to model annual wildfire risk across the Great Basin based on precipitation alone.

Interactions between temperature and drought in global and regional crop yield variability during 1961-2014.

Inter-annual crop yield variation is driven in large parts by climate variability, wherein the climate components of temperature and precipitation often play the biggest role. Nonlinear effects of temperature on yield as well as interactions among the climate variables have to be considered. Links between climate and crop yield variability have been previously studied, both globally and at regional scales, but typically with additive models with no interactions, or when interactions were included, with implications not fully explained. In this study yearly country level yields of maize, rice, soybeans, and wheat of the top producing countries were combined with growing season temperature and SPEI (standardized precipitation evapotranspiration index) to determine interaction and intensification effects of climate variability on crop yield variability during 1961–2014. For maize, soybeans, and wheat, heat and dryness significantly reduced yields globally, while global effects for rice were not significant. But because of interactions, heat was more damaging in dry than in normal conditions for maize and wheat, and temperature effects were not significant in wet conditions for maize, soybeans, and wheat. Country yield responses to climate variability naturally differed between the top producing countries, but an accurate description of interaction effects at the country scale required sub-national data (shown only for the USA). Climate intensification, that is consecutive dry or warm years, reduced yields additionally in some cases, however, this might be linked to spillover effects of multiple growing seasons. Consequently, the effect of temperature on yields might be underestimated in dry conditions: While there were no significant global effects of temperature for maize and soybeans yields for average SPEI, the combined effects of high temperatures and drought significantly decreased yields of maize, soybeans, and wheat by 11.6, 12.4, and 9.2%, respectively.

Effects of grazing and precipitation variability on vegetation dynamics in a Mongolian dry steppe

Grazing and water availability are the primary drivers of vegetation dynamics in grazing-dominated regions of Mongolia with a semi-arid climate and frequent droughts. Nomadic animal husbandry still plays a large part in the economy of Mongolia, but more variable precipitation regime and increase in livestock number have severely affected grassland ecosystems through overgrazing, leading to pasture degradation. This study aimed to examine the effects of grazing exclusion, interannual variation of plant-available precipitation (PAP) and their interaction on the aboveground biomass (AGB) of each dominant species, the AGB of annual species and the total AGB in a Mongolian dry steppe, using long-term field data. To detect the effect of grazing on vegetation dynamics, vegetation surveys were conducted in a non-grazed exclosure zone and a fully grazed area outside the exclosure. We assessed the effects of grazing, PAP and their interaction on AGB parameters using a generalized linear model. A detrended correspondence analysis (DCA) was used to visualize the effects of grazing and PAP on the AGB of each species. Grazing, PAP and their interaction had significant effects on AGB. The effect of grazing on AGB was larger with higher precipitation and higher amounts of AGB (i.e. forage) while AGB was strongly limited in drought years, which resulted in a smaller grazing effect. The current year PAP had the highest impact (r = 0.88, P < 0.01) on AGB. The dominance of annual species was characterized by the amount of PAP in the current and preceding years: annuals dominated in wet years that followed consecutive dry years. The DCA Axis 1 reflected the variation of AGB with interannual variation of PAP while the DCA Axis 2 differentiated the grazing effect. The DCA scatter diagram based on species score illustrated that Artemisia adamsii (an unpalatable herb) was clearly linked to grazing disturbance whereas palatable perennials such as Agropyron cristatum, Stipa krylovii and Cleistogenes squarrosa were related to grazing abandonment and wetter conditions. In brief, number of livestock, hence the grazing impacts on vegetation dynamic in this region could have driven by forage availability, which is mainly controlled by current-year PAP.