Human activities are transforming grassland biomass via changing climate, elemental nutrients, and herbivory. Theory predicts that food-limited herbivores will consume any additional biomass ...stimulated by nutrient inputs ('consumer-controlled'). Alternatively, nutrient supply is predicted to increase biomass where herbivores alter community composition or are limited by factors other than food ('resource-controlled'). Using an experiment replicated in 58 grasslands spanning six continents, we show that nutrient addition and vertebrate herbivore exclusion each caused sustained increases in aboveground live biomass over a decade, but consumer control was weak. However, at sites with high vertebrate grazing intensity or domestic livestock, herbivores consumed the additional fertilization-induced biomass, supporting the consumer-controlled prediction. Herbivores most effectively reduced the additional live biomass at sites with low precipitation or high ambient soil nitrogen. Overall, these experimental results suggest that grassland biomass will outstrip wild herbivore control as human activities increase elemental nutrient supply, with widespread consequences for grazing and fire risk.
Psychopharmacologic treatments for eating disorders (EDs) remain unclear, particularly for anorexia nervosa. As in attention-deficit hyperactivity disorder, a dopaminergic mechanism has been ...implicated in EDs, prompting our use of atomoxetine in an 18-year-old woman with anorexia nervosa, binge/purge type. Atomoxetine is a highly selective norepinephrine reuptake inhibitor with nonaddictive properties and limited effects of appetite suppression. Doses followed those used in a previous trial of atomoxetine in the treatment of binge ED, and response was assessed over 4 months, with significant improvement in ED behaviors and mood. Larger-scale, randomized studies that assess the efficacy of atomoxetine in the treatment of anorexia nervosa, binge/purge type are warranted.
Successful alien plant invasion is influenced by both climate change and plant–plant interactions. We estimate the single and interactive effects of competition and extreme weather events on the ...performance of the global legume invader Lupinus polyphyllus (Lindl.).
In three experimental studies we assessed (i) the stress tolerance of seedling and adult L. polyphyllus plants against extreme weather events (drought, fluctuating precipitation, late frost), (ii) the competitive effects of L. polyphyllus on native grassland species and vice versa, and (iii) the interactive effects of extreme weather events and competition on the performance of L. polyphyllus.
Drought reduced growth and led to early senescence of L. polyphyllus but did not reduce adult survival. Fluctuating precipitation events and late frost reduced the length of inflorescences. Under control conditions, interspecific competition reduced photosynthetic activity and growth of L. polyphyllus. When subjected to competition during drought, L. polyphyllus conserved water while simultaneously maintaining high assimilation rates, demonstrating increased water use efficiency. Meanwhile, native species had reduced performance under drought.
In summary, the invader gained an advantage under drought conditions through a smaller reduction in performance relative to its native competitors but was competitively inferior under control conditions. This provides evidence for a possible invasion window for this species. While regions of high elevation or latitude with regular severe late frost events might remain inaccessible for L. polyphyllus, further spread across Europe seems probable as the predicted increase in drought events may favour this non‐native legume over native species.
Dysphagia is common but may be underreported. Specific symptoms, rather than their perceived location, should guide the initial evaluation and imaging. Obstructive symptoms that seem to originate in ...the throat or neck may actually be caused by distal esophageal lesions. Oropharyngeal dysphagia manifests as difficulty initiating swallowing, coughing, choking, or aspiration, and it is most commonly caused by chronic neurologic conditions such as stroke, Parkinson disease, or dementia. Symptoms should be thoroughly evaluated because of the risk of aspiration. Patients with esophageal dysphagia may report a sensation of food getting stuck after swallowing. This condition is most commonly caused by gastroesophageal reflux disease and functional esophageal disorders. Eosinophilic esophagitis is triggered by food allergens and is increasingly prevalent; esophageal biopsies should be performed to make the diagnosis. Esophageal motility disorders such as achalasia are relatively rare and may be overdiagnosed. Opioid-induced esophageal dysfunction is becoming more common. Esophagogastroduodenoscopy is recommended for the initial evaluation of esophageal dysphagia, with barium esophagography as an adjunct. Esophageal cancer and other serious conditions have a low prevalence, and testing in low-risk patients may be deferred while a four-week trial of acid-suppressing therapy is undertaken. Many frail older adults with progressive neurologic disease have significant but unrecognized dysphagia, which significantly increases their risk of aspiration pneumonia and malnourishment. In these patients, the diagnosis of dysphagia should prompt a discussion about goals of care before potentially harmful interventions are considered. Speech-language pathologists and other specialists, in collaboration with family physicians, can provide structured assessments and make appropriate recommendations for safe swallowing, palliative care, or rehabilitation.
Dramatic shifts in marijuana laws, along with federal deregulation of hemp with the 2018 Farm Bill, have resulted in increased availability and use of cannabidiol (CBD) supplements throughout the ...United States (US). Given the rapid increase in CBD use in the U.S. general population, in this study, we aim to characterize primary care physician (PCP) attitudes and practice behaviors and to assess whether differences in provider attitudes and behaviors vary as a function of marijuana legalization (ML) status in the state of practice.
Data are from an online provider survey on CBD supplement-related attitudes, beliefs, and behaviors administered to 508 PCPs as part of a larger mixed methods study. Participating PCPs were recruited from the Mayo Clinic Healthcare Network and provided medical care in primary care settings across four U.S. states (Minnesota, Wisconsin, Florida, and Arizona).
The survey response rate was 45.4% (
=236/508). According to providers, CBD was frequently brought up in PCP settings, typically by patients. PCPs were generally hesitant to screen for or discuss CBD with their patients and identified multiple barriers to open patient-provider dialogue about CBD. PCPs practicing in states that had passed ML were more receptive to patients using CBD supplements, whereas PCPs practicing in states that had not passed ML were more concerned about CBD-related side effects. Regardless of state ML status, most PCPs did not feel that they should be recommending CBD supplements to their patients. Most PCPs reported believing that CBD was unhelpful for most conditions for which it is marketed, with chronic non-cancer pain and anxiety/stress being exceptions. PCP respondents generally felt that they had insufficient knowledge/training around CBD.
Results from this mixed methods study show that PCPs practicing in the U.S. rarely screen for or discuss CBD use with their patients and report several barriers to engage in proactive CBD-focused practice behaviors. Furthermore, survey results show that some PCP attitudes, practice behaviors, and barriers vary as a function of state ML status. These findings may guide medical education efforts and inform primary care practice modifications aimed at enhancing screening and monitoring of patient CBD use by PCPs.
Nutrient enrichment can simultaneously increase and destabilise plant biomass production, with co‐limitation by multiple nutrients potentially intensifying these effects. Here, we test how factorial ...additions of nitrogen (N), phosphorus (P) and potassium with essential nutrients (K+) affect the stability (mean/standard deviation) of aboveground biomass in 34 grasslands over 7 years. Destabilisation with fertilisation was prevalent but was driven by single nutrients, not synergistic nutrient interactions. On average, N‐based treatments increased mean biomass production by 21–51% but increased its standard deviation by 40–68% and so consistently reduced stability. Adding P increased interannual variability and reduced stability without altering mean biomass, while K+ had no general effects. Declines in stability were largest in the most nutrient‐limited grasslands, or where nutrients reduced species richness or intensified species synchrony. We show that nutrients can differentially impact the stability of biomass production, with N and P in particular disproportionately increasing its interannual variability.
Nutrient enrichment can simultaneously increase and destabilise plant biomass production, with co‐limitation by multiple nutrients potentially intensifying these effects. Here, using data from 34 grasslands over 7 years, we show prevalent destabilisation with fertilisation was driven by single‐nutrient effects on the temporal standard deviation of biomass production but was not influenced by synergistic interactions among multiple nutrients. Declines in stability were largest in the most nutrient‐limited grasslands, or where nutrients reduced species richness or intensified species synchrony.
Global change drivers, such as anthropogenic nutrient inputs, are increasing globally. Nutrient deposition simultaneously alters plant biodiversity, species composition and ecosystem processes like ...aboveground biomass production. These changes are underpinned by species extinction, colonisation and shifting relative abundance. Here, we use the Price equation to quantify and link the contributions of species that are lost, gained or that persist to change in aboveground biomass in 59 experimental grassland sites. Under ambient (control) conditions, compositional and biomass turnover was high, and losses (i.e. local extinctions) were balanced by gains (i.e. colonisation). Under fertilisation, the decline in species richness resulted from increased species loss and decreases in species gained. Biomass increase under fertilisation resulted mostly from species that persist and to a lesser extent from species gained. Drivers of ecological change can interact relatively independently with diversity, composition and ecosystem processes and functions such as aboveground biomass due to the individual contributions of species lost, gained or persisting.
We link changes in species composition to changes in biomass through time in a globally distributed grassland experiment. We investigate how local extinctions, colonisations and species that persist contribute to biomass change under fertilization (NPK) and under ambient conditions (control) through time. We show that the relationship between compositional and biomass changes depends on the component contributions of species that leave, enter or persist in communities experiencing global change.
Spatial rarity is often used to predict extinction risk, but rarity can also occur temporally. Perhaps more relevant in the context of global change is whether a species is core to a community ...(persistent) or transient (intermittently present), with transient species often susceptible to human activities that reduce niche space. Using 5–12 yr of data on 1,447 plant species from 49 grasslands on five continents, we show that local abundance and species persistence under ambient conditions are both effective predictors of local extinction risk following experimental exclusion of grazers or addition of nutrients; persistence was a more powerful predictor than local abundance. While perturbations increased the risk of exclusion for low persistence and abundance species, transient but abundant species were also highly likely to be excluded from a perturbed plot relative to ambient conditions. Moreover, low persistence and low abundance species that were not excluded from perturbed plots tended to have a modest increase in abundance following perturbance. Last, even core species with high abundances had large decreases in persistence and increased losses in perturbed plots, threatening the longterm stability of these grasslands. Our results demonstrate that expanding the concept of rarity to include temporal dynamics, in addition to local abundance, more effectively predicts extinction risk in response to environmental change than either rarity axis predicts alone.
Abstract
Dominance often indicates one or a few species being best suited for resource capture and retention in a given environment. Press perturbations that change availability of limiting resources ...can restructure competitive hierarchies, allowing new species to capture or retain resources and leaving once dominant species fated to decline. However, dominant species may maintain high abundances even when their new environments no longer favour them due to stochastic processes associated with their high abundance, impeding deterministic processes that would otherwise diminish them.
Here, we quantify the persistence of dominance by tracking the rate of decline in dominant species at 90 globally distributed grassland sites under experimentally elevated soil nutrient supply and reduced vertebrate consumer pressure.
We found that chronic experimental nutrient addition and vertebrate exclusion caused certain subsets of species to lose dominance more quickly than in control plots. In control plots, perennial species and species with high initial cover maintained dominance for longer than annual species and those with low initial cover respectively. In fertilized plots, species with high initial cover maintained dominance at similar rates to control plots, while those with lower initial cover lost dominance even faster than similar species in controls. High initial cover increased the estimated time to dominance loss more strongly in plots with vertebrate exclosures than in controls. Vertebrate exclosures caused a slight decrease in the persistence of dominance for perennials, while fertilization brought perennials' rate of dominance loss in line with those of annuals. Annual species lost dominance at similar rates regardless of treatments.
Synthesis.
Collectively, these results point to a strong role of a species' historical abundance in maintaining dominance following environmental perturbations. Because dominant species play an outsized role in driving ecosystem processes, their ability to remain dominant—regardless of environmental conditions—is critical to anticipating expected rates of change in the structure and function of grasslands. Species that maintain dominance while no longer competitively favoured following press perturbations due to their historical abundances may result in community compositions that do not maximize resource capture, a key process of system responses to global change.
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