Evapotranspiration (ET) is regulated by vapor pressure deficit (VPD) and soil moisture (SM) which are expected to change in global climate change. Understanding the impacts of VPD and SM on maize ET ...is essential for global food security and water cycle. Here, we estimate the actual maize ET in Southwest China during 2001–2011 based on Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) model using remote-sensing data and reanalysis data. Then, we define the extreme drought events in 2009–2011 using the smoothed standardized anomaly of the three-month Standardized Precipitation Evapotranspiration Index (SPEI) to investigate the responses of maize ET to VPD and SM during extreme drought events in Southwest China. We detected the lag times of maize ET responses to VPD and SM, and then analyzed the sensitivity of maize ET to VPD and SM with lagged effects. We found pervasive lagged responses of maize ET with a shorter lag time of VPD (1.12 ±0.006 months, P < 0.05) than SM (1.28±0.006 months, P < 0.05). We analyzed the lag times of maize ET in relation to elevation, temperature, and precipitation to investigate the abiotic impacts on the lagged responses and found the lagged responses were more prevalent in areas at higher altitudes with lower temperatures but there was less variation across precipitation gradients. Maize ET was more sensitive to VPD than SM with lagged effects. High VPD enhanced maize ET under sufficient SM but during an extreme drought event, maize ET might be dramatically reduced due to SM depletion in spite of high VPD. The study highlights the significance of atmospheric water demand for crop water consumption under extreme climate events.
•Maize ET had a shorter lag time to VPD (1.12 months) than SM (1.28 months).•The lagged response was prevalent at high altitudes with low temperatures.•Maize ET was more sensitive to VPD than SM with lagged effects.•Maize ET rose under high VPD with ample SM but might decrease due to SM depletion.
Atmospheric dryness, as indicated by vapor pressure deficit (VPD), has a strong influence on forest greenhouse gas exchange with the atmosphere. In this study, we used long‐term (10–30 years) net ...ecosystem productivity (NEP) measurements from 60 forest sites across the world (1003 site‐years) to quantify long‐term changes in forest NEP resistance and NEP recovery in response to extreme atmospheric dryness. We tested two hypotheses: first, across sites differences in NEP resistance and NEP recovery of forests will depend on both the biophysical characteristics (i.e., leaf area index LAI and forest type) of the forest as well as on the local meteorological conditions of the site (i.e., mean VPD of the site), and second, forests experiencing an increasing trend in frequency and intensity of extreme dryness will show an increasing trend in NEP resistance and NEP recovery over time due to emergence of long‐term ecological stress memory. We used a data‐driven statistical learning approach to quantify NEP resistance and NEP recovery over multiple years. Our results showed that forest types, LAI, and median local VPD conditions explained over 50% of variance in both NEP resistance and NEP recovery, with drier sites showing higher NEP resistance and NEP recovery compared to sites with less atmospheric dryness. The impact of extreme atmospheric dryness events on NEP lasted for up to 3 days following most severe extreme events in most forests, indicated by an NEP recovery of less than 100%. We rejected our second hypothesis as we found no consistent relationship between trends of extreme VPD with trends in NEP resistance and NEP recovery across different forest sites, thus an increase in atmospheric dryness as it is predicted might not increase the resistance or recovery of forests in terms of NEP.
This article explores the spatial and temporal changes in forest's resistance to and recovery from extreme atmospheric dryness (indicated by extreme VPD) events. The results showed that forest types, LAI, and median local VPD conditions explained over 50% of variance in both resistance and recovery across 60 forest sites. In addition, we found no consistent relationship between trends of extreme VPD with trends in resistance and recovery across different forest sites, thus an increase in atmospheric dryness as it is predicted might not increase the resistance or recovery of forests in terms of net ecosystem productivity.
Abstract
Ground squirrels act as important members of grassland ecosystems by serving as both ecosystem engineers and as a prey base for carnivores. There is mounting evidence that climate change is ...driving ground squirrel population declines. We resurveyed 54 historical localities throughout the Wyoming Basin and western Colorado where Wyoming Ground Squirrel (Urocitellus elegans) specimens were collected to investigate if climate change was driving extirpations at these historically occupied sites. We detected extirpations at 12 sites and used binomial generalized linear models in an information-theoretic framework to investigate if climate change was associated with these extirpations. Additionally, we investigated if land cover change was associated with persistence and if land cover ameliorated or exacerbated the effects of climate change. We found that changes in climate, especially increasingly dry summer air and increasing mean summer temperatures, were associated with a reduced probability that U. elegans persisted at a historically occupied site. In addition, we found that current forest cover at a site and increasing rangeland cover at the regional level were associated with reduced probability that U. elegans persisted, although these associations were weaker than the climate associations. The effects of climate change and land cover change did not interact. Our findings build on mounting evidence that montane-associated ground squirrels throughout the Western United States are negatively impacted by climate change. The reduction in ground squirrel abundance or their extirpation due to climate change could lead to changes in ecosystem structure or reductions in trophic complexity.
We resurveyed historical localities throughout the Wyoming Basin and western Colorado where Wyoming Ground Squirrel, Urocitellus elegans, specimens were collected to investigate if climate or land cover change was driving extirpations at these historically occupied sites.
Future climate will be characterized by an increase in frequency and duration of drought and warming that exacerbates atmospheric evaporative demand. How trees acclimate to long-term soil moisture ...changes and whether these long-term changes alter trees' sensitivity to short-term (day to months) variations of vapor pressure deficit (VPD) and soil moisture is largely unknown. Leaf gas exchange measurements were performed within a long-term (17 years) irrigation experiment in a drought-prone Scots pine-dominated forest in one of Switzerland's driest areas on trees in naturally dry (control), irrigated, and 'irrigation-stop' (after 11 years of irrigation) conditions. Seventeen years of irrigation increased photosynthesis (A) and stomatal conductance (gs) and reduced gs sensitivity to increasing VPD and soil drying. Following irrigation-stop, gas exchange decreased only after 3 years. After 5 years, maximum carboxylation (Vcmax) and electron transport (Jmax) rates in irrigation-stop recovered to similar levels as to before the irrigation-stop. These results suggest that long-term release from soil drought reduces the sensitivity to VPD and that atmospheric constraints may play an increasingly important role in combination with soil drought. Moreover, our study indicates that structural adjustments lead to an attenuation of initially strong leaf-level acclimation to strong multiple-year drought.
Velopharyngeal dysfunction (VPD) diagnosis and speech surgery outcomes are currently based solely on subjective evaluation criteria consisting of perceptual speech assessment and functional imaging. ...This study describes an objective and comparable method in VPD assessment and investigates the concurrence between the objective and subjective evaluations.
The present study included 20 paediatric patients presenting with VPD after primary repair (intravelar veloplasty) of cleft palate. Our protocol was based on computerized analysis of voice parameters by means of an objective tool, spectrography integrated with Multi-Dimensional Voice Program (MDVP). The protocol also included perceptual evaluation by speech therapist and phoniatrician (consensus listening), and parents. This is a single surgeon, single centre experience and all patients underwent a secondary Furlow's palatoplasty. Assessments were performed pre- and postoperatively and upon completion of speech therapy. Results were compared using the two-tailed t student test for paired data. Statistical significance was set for p-values <0.05.
Data analysis confirmed an improvement in velopharyngeal closure after surgery and speech therapy consistently with the results of perceptual evaluations.
The results of the study confirmed the availability and reliability of an objective method for VPD evaluation based on the analysis of voice parameters with investigations that are simple and easily available in a hospital setting.
•Semi-empirical SIF-based ET estimation model is proposed.•The effectiveness of SIF is improved after multiplying SIF by VPD0.5.•SIF-based model showed better performance than traditional ...meteorological model.
Terrestrial evapotranspiration (ET) is a critical component of the land surface and its accurate estimation is crucial in understanding the global water and energy budgets. Current large-scale ET estimation models depend on remotely sensed data products of meteorological conditions and vegetation phenology, but high uncertainty remains to correctly represent ecological factors, which are regulated by biochemistry. In recent years, solar-induced fluorescence (SIF), a proxy for photosynthesis, has been extensively used in different ecological research and is conceived to be of great potential for ET estimation to constrain the transpiration flux, which is the significant component of ET. So far, most SIF-based ET estimation methods are achieved via empirical methods, which lack a solid physical foundation. In this work, we estimated ET by combining SIF and meteorological variables with Fick's law and an optimal stomatal behavior model and validated the model across different eddy-covariance flux stations around the globe. The model showed overall good performance across different ecosystems and when compared with other remote sensing-based ET models, such as the Priestley Taylor-JPL (PT-JPL) model, the Moderate Resolution Imaging Spectroradiometer (MODIS)-ET products, and a simple empirical linear SIF-ET model, the RMSE of estimated ET of the model proposed in this paper demonstrated better performance. The model we proposed here can be potentially extended for a reliable ET estimation at a global scale.
High vapour pressure deficit (VPD) in the air and water deficits in the soil are considered two key stress factors limiting crop growth and production. To explore their interactive effects on ...stomatal behaviour and plant water use and the role of abscisic acid (ABA) in mediating these responses, two tomato (Solanum lycopersicum) genotypes, Ailsa Craig (AC) and its ABA-deficient mutant (flacca), were grown at two VPD levels (VPD1, 0.71 kPa and VPD2, 1.25 kPa) and were exposed to progressive soil drying. The results showed that the relatively higher VPD, i.e. VPD2, decreased stomatal conductance only in AC, and increased transpiration rate and water consumption in both genotypes, which was associated with altered stomatal morphological traits, including lowered stomatal density, reduced stomatal size and pore aperture. During progressive soil drying, both AC and flacca grown at VPD2 closed stomata earlier than VPD1-plants with a low leaf ABA concentration, indicating that rising VPD advanced stomatal drought response in an ABA-independent way. At the end of soil drying, the stomata of VPD1-AC plants remained widely opened resulting in fast desiccation of the leaves excised from the plants upon exposure to VPD2, which implied an interaction of VPD and ABA in mediating short-term stomatal response. VPD2 increased the intrinsic water use efficiency (WUE) in AC plants but decreased the whole-leaf and plant WUE in both genotypes, as affirmed by the corresponding changes in leaf δ13C and δ 18O. Compared to δ 18O, δ13C was a more robust indicator of stomatal movement when plants were exposed to combined atmospheric and soil droughts. Collectively, these findings provide some novel insights into the stomatal regulation of tomato plants confronting combined atmospheric and edaphic droughts.
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•Abscisic acid is involved in the modulation of stomatal behavior by VPD.•Low VPD leads to impairment of stomata responsiveness through interaction with ABA.•Plants close stomata earlier in response to soil drought at higher VPD environment.•δ13C is a more robust indicator of stomatal movement than δ18O under changing environment.
This paper studies a parallel heterogeneous machine batching and scheduling problem in which weighted jobs are first batched, and the batches are then assigned and sequenced on machines of varying ...capacities. The duration of a batch is the longest time needed to process a job, and the objective is that of minimizing the makespan, or the sum of the batches durations on the machine finishing last. The authors develop polynomial-size mathematical formulations and a variable neighborhood search metaheuristic. Extensive computational results suggest that a flow-based formulation outperforms a compact formulation, despite its larger number of variables. The metaheuristic is capable of producing high-quality solutions within a limited computing time.
•We introduce two models for the (Pm|p−batch|Cmax) batch processing problem.•A variable neighborhood search (VNS) metaheuristic is developed.•The performance of the formulations, the VNS and known algorithms are compared.
