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To understand how climate change affects crop yields, we need to identify the climatic indices that best predict yields. Grain yields are most often predicted using precipitation and temperature in statistical models, assuming linear dependences. However, soil water availability is more influential for plant growth than precipitation and temperature, and there is ecophysiological evidence of intermediate yield maximizing conditions. Using rainfed maize and soybean yields for 1970–2010 across the USA, we tested whether the aridity index, that is, the ratio of precipitation and potential evapotranspiration seasonal totals and a proxy of soil water availability, better predicts yield than growing season precipitation total, average temperature and their interaction. We also tested for non‐monotonic responses allowing for intermediate yield‐maximizing conditions. The aridity index alone explained 77% and 72% of maize and soybean yield variability, compared with 78% and 73% explained by temperature, precipitation and their interaction. Yield responses were non‐monotonic, with yields maximized at intermediate precipitation and temperature as well as at intermediate aridity index of 0.79 for maize and 0.98 for soybean. The yield maximizing precipitation also increased with growing season average temperature, faster in maize than soybean. The intermediate yield maximizing conditions show that rainfed maize and soybean yields could both increase and decrease depending on whether climatic conditions come closer to or deviate from the yield maximizing conditions in the future. In most counties, during 1970–2010, the precipitation and aridity index were lower and temperature higher compared with those maximizing yields, suggesting that climate change will reduce yields. [ABSTRACT FROM AUTHOR]

The main content of this article is gambling and the pathology it can bring on. In order to introduce the subject I have examined national gambling organizations and the legislative body responsible for gambling. Then I have analysed the clinical picture of the pathology and personality and behavioural characteristics of the pathological gambler. After a short analysis of the main treatments of pathological gambling. I have examined closely the particular therapy of “Gamblers Anonymous”. This is the clinical context where I have done research involving 10 members of Florence Gamblers Anonymous in order to examine two particular aspects of pathological gamblers: their wrong thinking about games and their decision to take part in the association. In short, in view of the gravity of this pathology, I have analysed some important measures to prevent and to protect pathological gamblers. Le sujet de cet article est le jeu de hasard et, en particulier, la pathologie qui s’y rapporte. Tout d’abord, on examine l’organisation des jeux d’argent réservée aux opérateurs publics italiens et sa réglementation. Pour continuer, on analyse d’un point de vue clinique la pathologie, les caractéristiques et les comportements typiques des joueurs problématiques. Après un bref aperçu des différents traitements de la pathologie, on considère celui du groupe d’entraide mutuelle des « Joueurs Anonymes ». Dans ce contexte clinique, on a mené une recherche sur 10 membres d’un groupe de Joueurs Anonymes de Florence, afin d’approfondir les deux aspects suivants concernants les joueurs problématiques : leurs idées erronées sur le jeu et leur décision de se joindre au groupe de soutien des « Joueurs Anonymes ». Pour conclure, en raison de la gravité de cette pathologie inconnue de la plupart des gens, on réfléchit à certaines mesures de prévention importantes ainsi que de protection des personnes dépendantes du jeu de hasard.Argomento centrale di questo articolo è il gioco d’azzardo ed in particolare la patologia che esso può indurre. Al fine di introdurre il tema, viene esaminata l’organizzazione del gioco pubblico in Italia ed il contesto normativo in cui la materia è inserita. E’ poi analizzato l’inquadramento clinico della patologia e le caratteristiche di personalità e comportamentali tipiche del giocatore d’azzardo problematico. Dopo una breve disamina dei diversi programmi di trattamento della patologia, viene approfondita la particolare forma di terapia del gruppo di auto-aiuto dei “Giocatori Anonimi”. Essa rappresenta il contesto clinico all’interno del quale si è svolta una ricerca, che ha coinvolto 10 membri di un gruppo dell’associazione Giocatori Anonimi di Firenze, volta ad approfondire due aspetti peculiari dei giocatori d’azzardo patologici, cioè quelli relativi alle loro modalità erronee di pensiero concernenti il gioco ed alla loro decisione di partecipare al programma. In conclusione, data la gravità di questa patologia ai più sconosciuta, sono analizzate alcune importanti misure di prevenzione e di tutela dei giocatori d’azzardo problematici.

In arable systems, large amounts of nutrients, particularly of nitrogen (N) and phosphorus (P), are not efficiently converted into harvestable products and are lost from agricultural systems, with negative consequences for agricultural productivity and the environment. These nutrient losses are mediated by hydroclimatic processes causing nutrient leaching and volatilization. We quantify over the period 1987–2012 how water availability through the evaporative ratio (actual evapotranspiration divided by precipitation) and irrigation, agricultural practices, and edaphic conditions jointly affect nutrient use efficiencies in 110 agricultural catchments in the United States. We consider N and P use efficiencies (nitrogen use efficiency [NUE] and phosphorous use efficiency [PUE]) defined as ratios of catchment-scale N and P in harvested products over their respective inputs, as well as the NUE/PUE ratio, as an indication of catchment-scale N and P imbalance. Both efficiencies increase through time because of changes in climate and agronomic practices. Setting all else at the median value of the data set, NUE and PUE increased with evaporative ratio by 0.5% and 0.2% when increasing the evaporative ratio by 20% and by 4.9% and 18.8% in the presence of irrigation. NUE was also higher in catchments where maize and soybean were dominant (increasing by 2.3% for a 20% increase in maize and soybean fractional area). Soil properties, represented by mineral soil texture and organic matter content, had only small effects on the efficiencies. Our results show that both climatic conditions and crop choice are important drivers of nutrient use efficiencies in agricultural catchments. [ABSTRACT FROM AUTHOR]

In this stochastic rainfall scenario, we can exchange the long-term average in Equation 3 with the ensemble average so that the long-term mean net carbon gain rate defined with Equation 3 becomes (Lu et al., 2016) 10 HT ht Implementation In the single dry-down scenario (but not in the stochastic rainfall scenario), the simulations were run in discrete time with all the state variables updated daily. Stomatal regulation is a cornerstone process that links the exchange of carbon and water between vegetation and atmosphere, and how it is affected by plant water stress. [Extracted from the article]

Droughts affect ecosystems at multiple time scales, but their sub‐seasonal legacy effects on vegetation activity remain unclear. Combining the satellite‐based enhanced vegetation index MODIS EVI with a novel location‐specific definition of the growing season, we quantify drought impacts on sub‐seasonal vegetation activity and the subsequent recovery in the Northern Hemisphere. Drought legacy effects are quantified as changes in post‐drought greenness and sensitivity to climate. We find that greenness losses under severe drought are partially compensated by a ∼+5% greening within 2–6 growing‐season months following the droughts, both in woody and herbaceous vegetation but at different timings. In addition, post‐drought sensitivity of herbaceous vegetation to hydrological conditions increases noticeably at high latitudes compared with the local normal conditions, regardless of the choice of drought time scales. In general, the legacy effects on sensitivity are larger in herbaceous vegetation than in woody vegetation. Plain Language Summary: Droughts are increasingly severe and widespread globally, but their impacts on the global carbon cycle remain unclear due to the complexity of vegetation response to climate under and after droughts. In particular, how much plant activity decreases during drought and how quickly it recovers in the following months or years is not well understood. Here, by employing large‐scale satellite‐derived vegetation information, we identify the existence of widespread drought legacy effects on vegetation activity in the Northern Hemisphere ecosystems. We find that vegetation becomes greener in 2–6 growing‐season months after severe droughts with a stronger response to climate. These findings are in general more prominent at mid‐ and high‐latitudes, in particular for the grass‐dominated ecosystems compared with the tree‐dominated ones. Our analyses extend the picture for understanding how vegetation responds to severe droughts and could provide useful information to assist the development of dynamic vegetation models toward assessing changes in ecosystem resilience under changing climates. Key Points: Prominent increases in the sensitivity of herbaceous vegetation to hydrological conditions after severe droughts in the high‐latitudesSignificant vegetation greening in the 2–6 growing‐season months following severe droughtsLarger drought legacy effects on the sensitivity of herbaceous vegetation to climate compared with woody vegetation [ABSTRACT FROM AUTHOR]

Elevated atmospheric CO2 concentration is expected to increase leaf CO2 assimilation rates, thus promoting plant growth and increasing leaf area. It also decreases stomatal conductance, allowing water savings that have been hypothesized to drive large-scale greening, in particular in arid and semiarid climates. However, the increase in leaf area could reduce the ameliorating effect of elevated CO2 concentration on soil water depletion. The net effect of elevated CO2 on leaf- and canopy-level gas exchange thus remains unclear. To address this question, a heuristic model based on the Partitioning of Equilibrium Transpiration and Assimilation (PETA) hypothesis and a model based on stomatal optimization theory are used and their outcomes compared. Predicted relative changes in leaf- and canopy-level gas exchange rates are used as a metric of responses to changes in atmospheric CO2 concentration. Both models predict reductions of leaf-level transpiration rate due to decreased stomatal conductance under elevated CO2, but negligible (PETA) or no (optimization) changes in canopy-level transpiration due to the compensatory effect of increased leaf area. Leaf-and canopy-level CO2 assimilation are predicted to increase, with an amplification of the CO2 fertilization effect at the canopy-level due to the enhanced leaf area. The expected increase in vapor pressure deficit (VPD) under warmer conditions is predicted to decrease the sensitivity of gas exchange to atmospheric CO2 concentration in both models except at growth temperatures lower than the photosynthetic thermal optimum. The consistent predictions by different models that canopy-level transpiration varies little under elevated CO2 due to combined stomatal conductance reduction and leaf area increase highlights the coordination of physiological and morphological characteristics in vegetation to maximize resource use (here water) under altered atmospheric conditions. [ABSTRACT FROM AUTHOR]

Intercropping of two or more species on the same piece of land can enhance biodiversity and resource use efficiency in agriculture. Traditionally, intercropping systems have been developed and improved by empirical methods within a specific local context. To support the development of promising intercropping systems, the individual species that are part of an intercrop can be subjected to breeding. Breeding for intercropping aims at resource foraging traits of the admixed species to maximize niche complementarity, niche facilitation, and intercrop performance. The breeding process can be facilitated by modeling tools that simulate the outcome of the combination of different species' (or genotypes') traits for growth and yield development, reducing the need of extensive field testing. Here, we revisit the challenges associated with breeding for intercropping, and give an outlook on applying crop growth models to assist breeding for intercropping. We conclude that crop growth models can assist breeding for intercropping, provided that (i) they incorporate the relevant plant features and mechanisms driving interspecific plant–plant interactions; (ii) they are based on model parameters that are closely linked to the traits that breeders would select for; and (iii) model calibration and validation is done with field data measured in intercrops. Minimalist crop growth models are more likely to incorporate the above elements than comprehensive but parameter-intensive crop growth models. Their lower complexity and reduced parameter requirement facilitate the exploration of mechanisms at play and fulfil the model requirements for calibration of the appropriate crop growth models. [ABSTRACT FROM AUTHOR]

Seed predation can reduce the abundance and spread of unwanted vegetation in agricultural and other semi‐natural ecosystems. However, knowledge of how variations in seed predation rates affect plant species population dynamics is needed for decision making and knowledge‐based ecosystem management.We developed a stage‐classified stochastic matrix population model for Alopecurus myosuroides Huds. (blackgrass), an annual plant species thriving as a weed in temperate agroecosystems of Western and Northern Europe. The model was parameterised using empirical demographic data from long‐term experiments in Swedish winter wheat fields, including information on post‐dispersal seed losses by vertebrate and invertebrate seed predators.For agroecosystems with highly effective weed control measures (e.g. chemical and mechanical weed control), model simulations showed that seed losses via seed predation need to reach at least 78% at peak seed shedding to suppress population growth of A. myosuroides.The field experiment showed that vertebrates were most important for seed predation in July, at peak seed shedding. In August, after crop harvest, invertebrates were responsible for almost all seed predation. The model indicated that weed seed predation was much more important for weed regulation when it occurred before crop harvest in July. Vertebrates most strongly reduced population growth of A. myosuroides, although both vertebrates and invertebrates were needed to prevent it entirely.Synthesis and applications. We showed that weed seed predation by vertebrate and invertebrate seed predators is key for reducing the population growth of winter annual weeds like A. myosuroides in intensively managed agroecosystems. Therefore, protection of weed seed predators is essential for making management of unwanted vegetation less dependent on chemical and mechanical measures. [ABSTRACT FROM AUTHOR]

When modelling forest growth, capturing the effects of climate change is needed for reliable long-term predictions and management choices. This remains a challenge because commonly used mensurational forest growth and yield models, relying on inventory data, cannot account for climate change effects. We developed hybrid physiological/mensurational basal area growth and yield models, which combine physiological response to climatic conditions and empirical relations. We included climate and site effects by replacing time with light sums of photosynthetically active radiation and modifying the latter with monthly soil water, vapour pressure deficit, temperature, and frost days. When parameterised with permanent sample plot data for Scots pine and Norway spruce across Sweden, the hybrid models could reproduce observations well, although with no increase in precision compared with time-based mensurational models. When considering different climate scenarios, a significant impact on productivity from climate change emerged. For example, a 2 °C warming enhanced Scots pine production by up to 14% in regions where temperatures were originally cooler and soil water deficit was low (i.e. northwest Sweden), but depressed it, up to 9%, elsewhere. Hence, climate-sensitive models that take local variations into account are necessary for accurate predictions and sustainable forest management. [ABSTRACT FROM AUTHOR]

Summary: Stomatal optimization models can improve estimates of water and carbon fluxes with relatively low complexity, yet there is no consensus on which formulations are most appropriate for ecosystem‐scale applications. We implemented three existing analytical equations for stomatal conductance, based on different water penalty functions, in a big‐leaf comparison framework, and determined which optimization principles were most consistent with flux tower observations from different biomes.We used information theory to dissect controls of soil water supply and atmospheric demand on evapotranspiration in wet to dry conditions and to quantify missing or inadequate information in model variants. We ranked stomatal optimization principles based on parameter uncertainty, parsimony, predictive accuracy, and functional accuracy of the interactions between soil moisture, vapor pressure deficit, and evapotranspiration.Performance was high for all model variants. Water penalty functions with explicit representation of plant hydraulics did not substantially improve predictive or functional accuracy of ecosystem‐scale evapotranspiration estimates, and parameterizations were more uncertain, despite having physiological underpinnings at the plant level.Stomatal optimization based on water use efficiency thus provided more information about ecosystem‐scale evapotranspiration compared to those based on xylem vulnerability and proved more useful in improving ecosystem‐scale models with less complexity. [ABSTRACT FROM AUTHOR]