Wet Spring Research Articles

Estimated Economic Impacts of the 2019 Midwest Floods

In the spring of 2019, U.S. agriculture experienced a record high number of prevented planted acres primarily due to historic rainfall across large portions of the Corn Belt and Mid-South. Producers of corn, upland cotton, soybean, and wheat were impacted with a substantial loss of revenue due to no crops being produced and marketed. With about 11.4 million acres of corn not planted, foregone gross revenue from crop sales likely exceeded $6 billion alone. Instead of focusing on the loss of producers’ incomes as a result of prevented planted acres, our analysis focuses on the economic impacts, due to lost sales, for firms that provide inputs to farmers. Acres prevented from planting resulted in producers not incurring typical expenditures for planting and post planting inputs such as seed, crop nutrients, and crop protection (herbicides, insecticides, fungicides, etc.). Agricultural input manufacturers, wholesalers, and retailers do not have similar opportunities to insure against foregone sales and have received no disaster assistance payments. Normally, the large geographic footprint of many of these firms mitigates the impact of localized weather effects. However, given the widespread nature of the wet spring, these firms were negatively affected across Corn Belt and Mid-South representing a substantial production area. Regional economic impact of declines in sales by agricultural input providers due to wet weather-based prevented plantings on 13.1 million acres. Direct sale losses of $2.9 billion led to $4.5 billion losses in total sales that were concentrated in parts of Minnesota, South Dakota, and Illinois.

Investigating the controls on greenhouse gas emission in the riparian zone of a small headwater catchment using an automated monitoring system

AbstractRiparian zones as the transition zone between terrestrial and aquatic ecosystems play an important role in C and N cycling and greenhouse gas (GHG) emissions. As such, they may help to mitigate climate change but could also accelerate it, depending on the particular processes affected by changes in the hydrologic regime. Hydrological observations indicated frequent shallow groundwater in the riparian zone, especially near the stream and during the wet winter and spring seasons with consequently frequent occurrence of soil water saturation. The redox potential was mainly governed by the soil water regime: under water saturation conditions, the redox potential of the soil decreased and returned to the oxic state after soil drainage. We found that soil temperature and soil water content were the main drivers of the variations in CO2 fluxes, with highest CO2 emission during summer and the lowest emissions in the winter period (162.2–5.4 mg CO2–C m−2 h−1). The annual average daily N2O emission rate was low (2.3 μg N2O‐N m−2 h−1), with the highest average daily N2O emission in March as a result of low temperature and partial soil saturation after heavy precipitation events (37.5 μg N2O‐N m−2 h−1). Our study showed that continuous measurement of redox potential, soil temperature, and soil water content can improve the understanding of GHG emissions in riparian zones.

Is the Life History Flexibility of Cold Desert Annuals Broad Enough to Cope with Predicted Climate Change? The Case of Erodium oxyrhinchum in Central Asia.

Simple SummaryThe broad objective of our study was to evaluate the life history flexibility of the annual Erodium oxyrhinchum in relation to the predicted changes in precipitation in the cold desert due to climate change. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring- and autumn-germinated seeds of the cold desert annual E. oxyrhinchum from 2016–2020. Also, the future climate for the region was modeled. Our results found that given the flexibility in the life history of E. oxyrhinchum, it seems unlikely that future climate change will have much of an impact on the life history and dominant position of this species in the herbaceous plant community in the unpredictable-rainfall environment of the cold desert. Our study challenges the commonly-held perception that desert organisms may be negatively affected by climate change.Interannual seasonal variability in precipitation may strongly affect the life history and growth of desert annual plants. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring (SG)- and autumn (AG)-germinated seeds of the cold desert annual Erodium oxyrhinchum. Vegetative and reproductive growth and F2 seed dormancy and germination were monitored from September 2016 to November 2020 in the sandy Gurbantunggut Desert in NW China in Central Asia. Dry autumns decreased the density of AG plants, and dry springs decreased the density of SG plants and growth of SG and AG plants. In dry springs, SG plants were more sensitive to precipitation than AG plants, while in wet springs SG and AG plants had similar responses to precipitation. During growth in both dry and wet springs, most morphological characters of SG and AG plants initially increased rapidly in size/number and then plateaued or decreased, except for SG plants in dry springs. In dry springs, most morphological characters of AG plants were larger or more numerous than those of SG plants, and they were larger/more numerous for SG plants in wet than in dry springs. The percentage biomass allocated to reproduction in SG plants was slightly higher in a wet than in a dry spring. A much higher proportion of dormant seeds was produced by AG plants in a wet spring than in a dry spring. Projected changes in precipitation due to climate change in NW China are not likely to have much of an effect on the biology of this common desert annual plant.

How could simulated dewatering of slurry mitigate nitrous oxide emissions from fall and spring injections? – A modelling study in a Chernozem soil in Western Canada

Process-based ecosystem models, such as ecosys, can be useful tools to gain insights and accurately project nitrous oxide (N2O) inventories in national, regional and global scales, and to explore potential emission reduction strategies. Our objectives are to investigate how the ecosys model simulate the effects of fall and spring slurry injections on N2O production and if de-watering slurry could become a potential N2O mitigation strategy for both fall and spring injections. The ecosys model was used to simulate hourly N2O fluxes from 2014 to 2017 in a cropping system with and without slurry (fall and spring additions) in comparison with field measurements in Alberta, Canada. Furthermore, we performed simulations of de-watered fall and spring slurry applications in the same scenarios. Our results showed ecosys adequately simulated soil temperatures and moisture contents at 10 and 20 cm depths [correlation coefficients (r) ≥ 0.929 for temperatures; r ≥ 0.529 for moistures]. The divergences of modelled and measured soil water contents during spring thaws could be attributed to uncertainties in model inputs for soil hydrological parameters as well as uncertainties in field measurements. The model captured reasonably well the dynamics of N2O fluxes from soils receiving fall and spring slurry (r = 0.356). However, the concurrent discrepancies of N2O fluxes between modelled and measured values during the wetter spring thaw of 2017 might be a result of an unsatisfactory simulation of snowmelt infiltration and runoff. Compared to whole slurry, simulated de-watered slurry resulted in considerable reductions in cumulative N2O emissions by 16–36 and 23–29% for fall and spring slurry injections, respectively. The model results indicate that de-watering slurry would potentially be an efficient emission mitigation strategy; however, there is still a paucity of studies addressing the feasibility of dewatering as a practice and further research can focus on this knowledge gap.

Early-life seasonal, weather and social effects on telomere length in a wild mammal.

Early-life environmental conditions can provide a source of individual variation in life-history strategies and senescence patterns. Conditions experienced in early life can be quantified by measuring telomere length, which can act as a biomarker of survival probability in some species. Here, we investigate whether seasonal changes, weather conditions and group size are associated with early-life and/or early-adulthood telomere length in a wild population of European badgers (Meles meles). We found substantial intra-annual changes in telomere length during the first 3years of life, where within-individual effects showed shorter telomere lengths in the winter following the first spring and a trend for longer telomere lengths in the second spring compared to the first winter. In terms of weather conditions, cubs born in warmer, wetter springs with low rainfall variability had longer early-life (3-12months old) telomeres. Additionally, cubs born in groups with more cubs had marginally longer early-life telomeres, providing no evidence of resource constraint from cub competition. We also found that the positive association between early-life telomere length and cub survival probability remained when social and weather variables were included. Finally, after sexual maturity, in early adulthood (i.e., 12-36months) we found no significant association between same-sex adult group size and telomere length (i.e., no effect of intrasexual competition). Overall, we show that controlling for seasonal effects, which are linked to food availability, is important in telomere length analyses, and that variation in telomere length in badgers reflects early-life conditions and also predicts first year cub survival.

Episodic occurrence of favourable weather constrains recovery of a cold desert shrubland after fire

Abstract Key to the long‐term resilience of dryland ecosystems is the recovery of foundation plant species following disturbance. In ecosystems with high interannual weather variability, understanding the influence of short‐term environmental conditions on establishment of foundation species is essential for identifying vulnerable landscapes and developing restoration strategies. We asked how annual environmental conditions affect post‐fire establishment of Artemisia tridentata, a shrub species that dominates landscapes across much of the western United States, and evaluated the influence of episodic establishment on population recovery. We collected A. tridentata stem samples from 33 plots in 12 prescribed fire sites that burned 8–11 years before sampling. We determined individual establishment years using annual growth rings. We measured seasonal soil environmental conditions at the study sites and asked if these conditions predicted annual establishment density. We then evaluated whether establishment patterns could be predicted by site‐level climate or dominant subspecies. Finally, we tested the effect of the magnitude and frequency of post‐fire establishment episodes on long‐term population recovery. Annual post‐fire recruitment of A. tridentata was driven by the episodic availability of spring soil moisture. Annual establishment was highest with wetter spring soils (relative influence [RI] = 19.4%) and later seasonal dry‐down (RI = 11.8%) in the year of establishment. Establishment density declined greatly 4 to 5 years after fire (RI = 17.1%). Post‐fire establishment patterns were poorly predicted by site‐level mean climate (marginal R2 ≤ 0.18) and dominant subspecies (marginal R2 ≤ 0.43). Population recovery reflected the magnitude, but not the frequency, of early post‐fire establishment pulses. Post‐fire A. tridentata density and cover (measured 8–11 years after fire) were more strongly related to the magnitude of the largest establishment pulse than to establishment frequency, suggesting that population recovery may occur with a single favourable establishment year. Synthesis and applications. This study demonstrates the importance of episodic periods of favourable weather for long‐term plant population recovery following disturbance. Management strategies that increase opportunities for seed availability to coincide with favourable weather conditions, such as retaining unburned patches or repeated seeding treatments, can improve restoration outcomes in high‐priority areas.

Crop responses to topsoil replacement within eroded landscapes

AbstractApproaches to restore productivity to eroded soils are urgently needed to sustain food security. We evaluated plant response to soil‐landscape rehabilitation, in which approximately 15 cm of topsoil was moved from depositional landscape positions to the eroded upper slope. Crop response was monitored for 6 yr of a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation at a severely eroded site and for 4 yr of a wheat (Triticum aestivum L.)–soybean rotation at a moderately eroded site. Experiments were conducted in years with relatively wet springs and droughty summers. In the severely eroded landscape, addition of 15 cm of soil increased crop biomass by 25–95% on a kg ha–1 basis and increased grain yields by 20–49% (corn) and 12–59% (soybean), with the largest yield increases recorded in the most eroded landscape positions. Soil addition increased corn grain protein and test weight. No significant differences were observed in crop emergence rate or stand establishment. In the moderately eroded landscape, soil addition significantly increased crop biomass, but not grain yield. In both landscapes, yields were lower in areas of soil removal than in adjacent areas from which no soil was removed, which is likely at least partially an artifact of the plot design. While more research is needed to evaluate long‐term impacts, the results of these studies show that soil‐landscape rehabilitation may help alleviate the effects of past erosion and provide immediate benefits to the productivity of severely eroded soils.

Grazing winter rye cover crop in a cotton no‐till system: Soil strength and runoff

AbstractGrazing cover crops (CC) could provide an economic incentive to increase adoption rates in the southeastern United States. However, understanding grazing effects on soil properties is lacking for most soils of the region. Effects of grazing or rolling a cereal rye (Secale cereale L.) CC prior to no‐till planting cotton (Gossypium hirsutum L.) were determined in 2009 after 4 yr on Cecil soil, in the Southern Piedmont near Watkinsville, GA. The four catchments had a previous long history of no‐till cropping with CC. Wet spring conditions in 2009 resulted in visible surface roughness from cattle hooves. Average soil penetration resistance (PR) for the 0‐ to 30‐cm profile was 14% greater following rye CC grazing than rolling (1.95 vs. 1.53 MPa) and was still apparent the following February (1.86 vs. 1.58 MPa) after cotton harvest. Increases in PR at 2.5‐ to 7.5‐ and 7.5‐ to 15‐cm soil depths were observed following CC grazing but not rolling. Depth to 2 MPa resistance, considered sufficient to impede root growth, was similar for CC grazing and rolling treatments in March prior to grazing but decreased in the grazed treatment to 10.7 cm in May and 15.6 cm in February. Seasonal runoff data for 2006–2009 indicated no differences between grazed and rolled CC management. We concluded that grazing CC for short periods under wet conditions presents a risk of short‐term negative effects even for Southern Piedmont soils where a long history of conservation tillage and CC has improved soil quality.

Simulating compound weather extremes responsible for critical crop failure with stochastic weather generators

Abstract. In 2016, northern France experienced an unprecedented wheat crop loss. The cause of this event is not yet fully understood, and none of the most used crop forecast models were able to predict the event (Ben-Ari et al., 2018). However, this extreme event was likely due to a sequence of particular meteorological conditions, i.e. too few cold days in late autumn–winter and abnormally high precipitation during the spring season. Here we focus on a compound meteorological hazard (warm winter and wet spring) that could lead to a crop loss. This work is motivated by the question of whether the 2016 meteorological conditions were the most extreme possible conditions under current climate, and what the worst-case meteorological scenario would be with respect to warm winters followed by wet springs. To answer these questions, instead of relying on computationally intensive climate model simulations, we use an analogue-based importance sampling algorithm that was recently introduced into this field of research (Yiou and Jézéquel, 2020). This algorithm is a modification of a stochastic weather generator (SWG) that gives more weight to trajectories with more extreme meteorological conditions (here temperature and precipitation). This approach is inspired by importance sampling of complex systems (Ragone et al., 2017). This data-driven technique constructs artificial weather events by combining daily observations in a dynamically realistic manner and in a relatively fast way. This paper explains how an SWG for extreme winter temperature and spring precipitation can be constructed in order to generate large samples of such extremes. We show that with some adjustments both types of weather events can be adequately simulated with SWGs, highlighting the wide applicability of the method. We find that the number of cold days in late autumn 2015 was close to the plausible minimum. However, our simulations of extreme spring precipitation show that considerably wetter springs than what was observed in 2016 are possible. Although the relation of crop loss in 2016 to climate variability is not yet fully understood, these results indicate that similar events with higher impacts could be possible in present-day climate conditions.

Mountain treelines climb slowly despite rapid climate warming

AbstractAimTo better understand how climate change drives altitudinal treeline dynamics at large spatial scales.LocationNorthern Hemisphere.Time period1901–2018.Major taxa studiedTree species that constitute alpine treelines.MethodsWe conducted a meta‐analysis of annual treeline shift rates at 143 sites from 38 published studies. For each site, we calculated current change rates in annual or seasonal temperatures, precipitation and drought (standardized precipitation evapotranspiration index). We then evaluated relationships between treeline shift rates, and site characteristics and climate using standard and partial correlation analyses, as well as generalized linear models. These analyses were conducted at the hemispheric scale and for two geographic subsets of subarctic (north of 60° N) and temperate regions (south of 60° N).ResultsTreelines ascended at 88.8%, remained stable at 10.5% and descended at 0.7% of the sites. The mean hemispheric shift rate (0.354 m/year) was half of what would be expected from climate warming alone. Treeline shifts were significantly faster in subarctic than temperate regions. The precipitation effect was more important than temperature for predicting treeline shift rate. In the subarctic regions, autumn precipitation mostly determined treeline shift rates. In the temperate region, warmer temperatures and higher autumn precipitation accelerated shift rates, whereas wetter springs reduced them. Autumn precipitation and winter mean minimum temperature best explained the treeline shift rates across the Northern Hemisphere.Main conclusionsA combination of thermal and hydrological factors drives treeline shift rates across the Northern Hemisphere, with precipitation assuming an important modifying role of the general temperature‐driven treeline ascent. Regional treeline shift rates, therefore, co‐depend on drying and wetting trends, which should be considered in future estimates of global change impacts on alpine ecosystems.

Assessing the Effectiveness of Sustainable Drainage Systems (SuDS): Interventions, Impacts and Challenges

Sustainable drainage systems (SuDS) can be a key tool in the management of extremes of rainfall, due to their capacity to attenuate and treat surface water. Yet, implementation is a complex process, requiring buy-in from multiple stakeholders. Buy-in is often undermined by a lack of practical evidence and monitoring of implemented SuDS. In this paper, we present a collaborative case study between a local authority, university and the UK Environment Agency. This partnership approach enabled the installation of SuDS and monitoring equipment to address surface runoff in the north east of England. Ultrasonic sensors were installed in the drainage network to evaluate the attenuation of surface water. SuDS were installed during an atypically wet spring, followed by a hot and dry summer, providing a range of conditions to assess their performance. Results demonstrate that there was a statistically significant difference in the detected flow level in manholes downstream of the SuDS interventions. Several challenges occurred, from signal obstacles in wireless telecommunication services, to logistical constraints of installing sensors in the drainage network, and issues with the adoption of property level SuDS. These issues require further research. Qualitative support for partnership working was crucial to increase the capacity for delivering SuDS. To ensure the success of future schemes and likelihood of SuDS uptake, partnership working and engaging with communities is vital.

Population Trends in Royal Catchfly (Silene regia) at Wilson's Creek National Battlefield, Missouri

Royal catchfly (Silene regia, Caryophyllaceae) is a rare, tap-rooted, perennial forb known to occupy Midwestern prairies, glades, and savannas, which are increasingly fragmented. Though not federally listed, it is recognized as rare, threatened, or endangered in six states. We resurveyed 15 populations identified in 1980s–1990s monitoring at Wilson's Creek National Battlefield, Republic, MO. Abundance at each site was collected in 6 y (1988–1989, 1998–2000, 2019); measures of plant height and stems browsed were collected in 4 y (1998–2000, 2019). Fire history and precipitation were also explored. Mean royal catchfly abundance per population declined significantly over the study period, and only five of 15 populations supported extant populations in 2019. Year, site location, and the interaction between the two were highly significant factors in explaining variation of height measures and proportion of stems browsed. Plant height was significantly higher in 2019 than any other year, corresponding with overgrowth of competing vegetation and a wet spring. Prescribed fires became less frequent over the study period, and the mean fire return interval was higher than the historical regime of the region (9.7 y vs. 4–8 y). The decline of royal catchfly at Wilson's Creek National Battlefield and similar sites points to the need for fire management and restoration of prairie and savanna ecosystems for the persistence of this rare species.

Dynamics of Microbial Community Structure and Ecological Functions in Estuarine Intertidal Sediments

Microbial communities are important indicators of aquatic ecosystem health, responsible for functional roles sustaining the ecosystem such as nutrient cycling, as well as environmental problems. Urbanized estuaries are vulnerable intersections between terrestrial and marine ecosystems and are susceptible to pressure and perturbation from both natural processes and human activities over time. The response by microbial communities towards changes in the environment should be closely monitored and studied. In this study, microbial communities in brackish intertidal sediments, sampled seasonally over a year along the coast of Yangtze River estuary, were analyzed using 16S rRNA gene sequencing. Potential compositional and functional changes in microbial communities resulting from temporal variation and associated physiochemical gradients in the environment were studied and notable patterns were observed over time. Summer season was recorded with the lowest microbial community α-diversity. For β-diversity, spatiotemporal differentiation in community structures was recorded with seasonal clustering. Proteobacteria was recorded as the most dominant phylum among all sampling sites throughout the year but its relative abundance showed no temporal changes. Instead, relative abundances of phyla Actinobacteria, Chloroflexi, and Verrucumicrobia were found to differ significantly over time, generally favoring the wet Spring and Summer. In contrast, temporal variation was observed for the class Deltaproteobacteria and some of the corresponding sulfate/sulfur-reducing bacterial genera, favoring the dry Autumn and Winter. However, there were no major temporal changes in ecological functions contributed by microbial communities throughout the study period. While results from redundancy analysis showed that the subtle changes in pH in the environment had the greatest impact on microbial community composition, the variation it explained remained relatively low. Alternatively, precipitation, distinguishing the dry and wet seasons of the subtropical monsoon climate zone, was suggested to be another potential key factor influencing microbial community composition and their relative abundances. The present study provides new data and insights on the impact of temporal variation on microbial community composition and ecological function in an urbanized estuarine ecosystem.

Associations between climate and earlywood and latewood width in boreal and Mediterranean Scots pine forests

Earlywood and latewood widths differently respond to the climate in boreal and Mediterranean Scots pine forests. The response is constrained by allometric relationships. Measurements of earlywood (EW) and latewood (LW) width can be used to assess how tree growth responds to the climate in different biomes. Through tree-ring analyses, we quantified and analysed EW and LW width in six Scots pine (Pinus sylvestris) forests situated in the boreal and Mediterranean biomes. We aimed to answer: (i) how coupled are EW and LW width in Scots pine boreal and Mediterranean European forests, and (ii) how do they respond to climate and atmospheric patterns. Using allometric approaches to assess the EW‒LW coupling and correlations with climate variables and indices we found that EW and LW width in Scots pine responds to different climate variables depending on biome and site. We identified two groups of sites with slow-growing trees producing dense wood with more LW in boreal sites vs. fast-growing trees producing more conductive wood with a higher EW proportion in Mediterranean sites. In these sites, spring-to-summer drought was the main constraint of EW and LW production. In boreal sites, wet springs and warm summers improved EW and LW width, respectively. We also found a high coupling between EW and LW width in cold, dry Mediterranean sites. LW width was very responsive to climate and atmospheric patterns in warm, dry Mediterranean sites. The most consistent response to atmospheric patterns was a negative correlation between EW and the January North Atlantic Oscillation index in Mediterranean sites. Mediterranean Scots pine forests where LW width is not very dependent on EW width are potential sites for using LW variables as proxies of drought during the growing season.

Drought in the Eastern Cape region of South Africa and trends in rainfall characteristics.

Much of the Eastern Cape province in South Africa has been experiencing a severe drought since 2015. This drought has had major socio-economic effects particularly on the large impoverished rural population as well as on some urban areas where supplied water services have broken down in several cases. The region is influenced by both midlatitude and tropical systems leading to a complex regional meteorology that hitherto has not been much studied compared to other parts of South Africa. Here, the ongoing drought is examined in the context of long-term trends and the interannual rainfall variability of the region. Although the region has experienced drought in all seasons since 2015, focus here is placed on the spring (September–November) which shows the most consistent and robust signal. On average, this season contributes between about 25–35% of the annual rainfall total. Based on CHIRPS data, it is found that this season shows a significant decreasing trend in both rainfall totals as well as the number of rainfall days (but not heavy rainfall days) for spring over most of the province since 1981. On interannual time scales, the results indicate that dry (wet) springs over the Eastern Cape are associated with a cyclonic (anticyclonic) anomaly southeast of South Africa as part of a shift in the zonal wavenumber 3 pattern in the midlatitudes. Over the landmass, a stronger (weaker) Botswana High is also apparent with increased (decreased) subsidence over and near the Eastern Cape which is less (more) favourable for cloud band development and hence reduced (enhanced) rainfall during dry (wet) springs. Analysis of mid-century (2040–2060) CMIP5 rainfall projections suggests that there may be a flattening of the annual cycle over the Eastern Cape with the winter becoming wetter and the summer drier. For the spring season of interest here, the multi-model projections also indicate drying but less pronounced than that projected for the summer.

Population Trends in Royal Catchfly (Silene regia) at Wilson's Creek National Battlefield, Missouri

Royal catchfly (Silene regia, Caryophyllaceae) is a rare, tap-rooted, perennial forb known to occupy Midwestern prairies, glades, and savannas, which are increasingly fragmented. Though not federally listed, it is recognized as rare, threatened, or endangered in six states. We resurveyed 15 populations identified in 1980s–1990s monitoring at Wilson's Creek National Battlefield, Republic, MO. Abundance at each site was collected in 6 y (1988–1989, 1998–2000, 2019); measures of plant height and stems browsed were collected in 4 y (1998–2000, 2019). Fire history and precipitation were also explored. Mean royal catchfly abundance per population declined significantly over the study period, and only five of 15 populations supported extant populations in 2019. Year, site location, and the interaction between the two were highly significant factors in explaining variation of height measures and proportion of stems browsed. Plant height was significantly higher in 2019 than any other year, corresponding with overgrowth of competing vegetation and a wet spring. Prescribed fires became less frequent over the study period, and the mean fire return interval was higher than the historical regime of the region (9.7 y vs. 4–8 y). The decline of royal catchfly at Wilson's Creek National Battlefield and similar sites points to the need for fire management and restoration of prairie and savanna ecosystems for the persistence of this rare species.

Biogeographic, Atmospheric, and Climatic Factors Influencing Tree Growth in Mediterranean Aleppo Pine Forests

There is a lack of knowledge on how tree species respond to climatic constraints like water shortages and related atmospheric patterns across broad spatial and temporal scales. These assessments are needed to project which populations will better tolerate or respond to global warming across the tree species distribution range. Warmer and drier conditions have been forecasted for the Mediterranean Basin, where Aleppo pine (Pinus halepensis Mill.) is the most widely distributed conifer in dry sites. This species shows plastic growth responses to climate, being particularly sensitive to drought. We evaluated how 32 Aleppo pine forests responded to climate during the second half of the 20th century by using dendrochronology. Climatic constraints of radial growth were inferred by fitting the Vaganov–Shashkin (VS-Lite) growth model to ring-width data from our Aleppo pine forest network. Our findings reported that Aleppo pine growth decreased and showed the highest common coherence among trees in dry, continental sites located in southeastern and eastern inland Spain and Algeria. In contrast, growth increased in wetter sites located in northeastern Spain. Overall, across the Aleppo pine network tree growth was enhanced by prior wet winters and cool and wet springs, whilst warm summers were associated with less growth. The relationships between site ring-width chronologies were higher in nearby forests. This explains why Aleppo pine growth was distinctly linked to indices of atmospheric circulation patterns depending on the geographical location of the forests. The western forests were more influenced by moisture and temperature conditions driven by the Western Mediterranean Oscillation (WeMO) and the Northern Atlantic Oscillation (NAO), the southern forests by the East Atlantic (EA) and the august NAO, while the Balearic, Tunisian and northeastern sites by the Arctic Oscillation (AO) and the Scandinavian pattern (SCA). The climatic constraints for Aleppo pine tree growth and its biogeographical variability were well captured by the VS-Lite model. The model performed better in dry and continental sites, showing strong growth coherence between trees and climatic limitations of growth. Further research using similar broad-scale approaches to climate–growth relationships in drought-prone regions deserves more attention.

Weather fluctuations drive short‐term dynamics and long‐term stability in plant communities: A 25‐year study in a Central European dry grassland

AbstractQuestionInfrequent events of extreme drought or extreme temperatures may considerably affect the structure and functioning of vegetation. Here we investigate how fluctuations in precipitation and temperature shape year‐to‐year dynamics and plant species composition in a dry grassland community, and how this variation affects plants with different life histories.LocationDry grassland (Festucion valesiacae) in the Pavlov Hills, SE Czech Republic.MethodsLong‐term trends in vegetation change in the grassland studied were assessed by the ordination of plot records from vegetation surveys performed between 1930 and 2019. In addition, year‐to‐year changes in vegetation were studied in seven permanent plots of 16 m2 surveyed annually from 1993 to 2018. Variation in species composition and abundances was related to temperature and precipitation in the preceeding two springs, summers, autumns and winters using ordinations and mixed‐effect linear models.ResultsThere were no remarkable directional changes in the grassland community over the period 1930–2019. However, during the last 25 years, the community exhibited pronounced year‐to‐year fluctuations, which depended on weather conditions in the previous two years. Species with different life histories (e.g. perennials vs. annuals) and different ecology (e.g. ruderal vs. dry‐grassland species) responded differently to specific weather patterns. Perennials were sustained by wet summers, annuals benefitted from wet springs and autumns and moderately warm and wet winters, and covers of ruderals of mixed life histories increased after dry summers.ConclusionsPlant species composition in a Central European dry grassland shows remarkable year‐to‐year dynamics in response to weather patterns over the previous two years. These community changes are non‐directional and contribute to the stability of this grassland, which has not changed considerably over the past 90 years. However, increasing frequency of drought events because of ongoing climate change can result in a directional change with an expansion of ruderal species.

The effects of cassava variety, fertilizer type and dosage on physical and sensory characteristics of cassava-wheat composite bread

Substitution of wheat flour with high quality cassava flour (HQCF) in bread making is economically important in Nigeria as wheat is mainly imported. Different treatments are applied to cassava used for HQCF production and the effects of such a treatment on cassava-wheat bread quality is scarce in literature. This study was conducted to study the effects of cassava varieties (TME 419, TMS 30572), fertilizer type ((NPK 15-15-15, 20-10-10, 12-12-17) and dosage (150, 300 kg/ha) on physical and sensory characteristics of cassava-wheat composite bread according to General Linear Model (GLM) analysis. According to the results, the independent variables had varying effects on the composite bread quality. While the main effect of fertilizer type was significant for oven spring and crumb moisture content, the interactive effects of fertilizer type and dosage significantly influenced crumb texture and taste. In spite of the significant differences in certain physical and sensory attributes, the overall acceptability of bread samples did not differ significantly. HQCF from cassava variety TMS 30572 showed the best performance in making composite cassava-wheat bread in terms of physical and sensory properties.

Modelling nitrification inhibitor effects on N<sub>2</sub>O emissions after fall- and spring-applied slurry by reducing nitrifier NH<sub>4</sub><sup>+</sup> oxidation rate

Abstract. Reductions in N2O emissions from nitrification inhibitors (NI) are substantial but remain uncertain because measurements of N2O emissions are highly variable and discontinuous. Mathematical modelling may offer an opportunity to estimate these reductions if the processes causing variability in N2O emissions can be accurately simulated. In this study, the effect of NI was simulated with a simple, time-dependent algorithm to slow NH4+ oxidation in the ecosystem model ecosys. Slower nitrification modelled with NI caused increases in soil NH4+ concentrations and reductions in soil NO3- concentrations and in N2O fluxes that were consistent with those measured following fall and spring applications of slurry over 2 years from 2014 to 2016. The model was then used to estimate direct and indirect effects of NI on seasonal and annual emissions. After spring slurry applications, NI reduced N2O emissions modelled and measured during the drier spring of 2015 (35 % and 45 %) less than during the wetter spring of 2016 (53 % and 72 %). After fall slurry applications, NI reduced modelled N2O emissions by 58 % and 56 % during late fall in 2014 and 2015 and by 8 % and 33 % during subsequent spring thaw in 2015 and 2016. Modelled reductions were consistent with those from meta-analyses of other NI studies. Simulated NI activity declined over time so that reductions in N2O emissions modelled with NI at an annual timescale were relatively smaller than those during emission events. These reductions were accompanied by increases in NH3 emissions and reductions in NO3- losses with NI that caused changes in indirect N2O emissions. With further parameter evaluation, the addition of this algorithm for NI to ecosys may allow emission factors for different NI products to be derived from annual N2O emissions modelled under diverse site, soil, land use and weather.