For the past century, woody plants have increased in grasslands and savannas worldwide. Woody encroachment may significantly alter ecosystem functioning including fire regimes, herbivore carrying ...capacity, biodiversity and carbon storage capacity. Traditionally, increases in woody cover and density have been ascribed to changes in the disturbance regime (fire and herbivores) or rainfall. Increased atmospheric CO2 concentrations may also contribute, by increasing growth rates of trees relative to grasses. This hypothesis is still heavily debated because usually potential CO2 effects are confounded by changes in land use (disturbance regime). Here we analyse changes in woody density in fire experiments at three sites in South African savannas where the disturbance regime (fire and herbivores) was kept constant for 30 and 50 years. If global drivers had significant effects on woody plants, we would expect significant increases in tree densities and biomass over time under the constant disturbance regime. Woody density remained constant in a semiarid savanna but tripled in a mesic savanna between the 1970s and 1990s. At the third site, a semiarid savanna near the southern limits of the biome, tree density doubled from the mid 1990s to 2010. Interpretation of the causes is confounded by population recovery after clearing, but aerial photograph analysis on adjacent non‐cleared areas showed an accompanying 48% increase in woody cover. Increased CO2 concentrations are consistent with increased woody density while other global drivers (rainfall) remained constant over the duration of the experiments. The absence of a response in one semiarid savanna could be explained by a smaller carbon sink capacity of the dominant species, which would therefore benefit less from increased CO2. Understanding how savannas and grasslands respond to increased CO2 and identifying the causes of woody encroachment are essential for the successful management of these systems.
The pre-clearance New Zealand lowlands were largely in complex, liana-rich, multi-layered conifer-angiosperm forest. Here it is designated oceanic temperate forest (OTF), its climatic envelope is ...defined, global distribution is assessed and origin is reviewed. Often described as Gondwanan or relic, tree genera characteristic of the OTF are more likely to be shared with tropical regions to the north than with temperate fragments of Gondwana (southern Australia, southern South America). The OTF arose out of the warm temperate to subtropical forests of Zealandia that formed during the Palaeogene. Warm, fire-prone environments in the middle Miocene permitted an influx of Australian taxa. During the Pliocene/Pleistocene increasingly cool climates, less fire and loss of old, leached soils, reduced floristic diversity. Many low-nutrient specialists and arid-adapted Australian-origin taxa were lost, along with many now exclusively tropical genera. Reduction in ectomycorrhizal tall tree genera left only Nothofagaceae and myrtaceous Kunzea and thus OTF formations are largely arbuscular mycorrhizal. Lack of fast-growing, ectomycorrhizal cold-tolerant trees is a key reason for the marked physiognomic differences between northern temperate broadleaved forests and those of the New Zealand OTF. The pronounced oscillations in extent of dry, cool habitats and warm, moist habitats in this isolated archipelago during the Pleistocene had a profound effect on the composition and distribution of the OTF. We suggest two drivers have strongly modified both geographic and trait distribution in the flora. First, 'glacial-interglacial asymmetry'-trees adapted to harsh glacial climates have more difficulty persisting in the face of strong biotic competition in warm, wet interglacial landscapes than trees adapted to interglacials do in persisting in climatically protected sites in cold, dry glacial landscapes. And second, the 'Pleistocene ratchet'-the propensity of many forest species that lose range during a glacial (or interglacial) to fail to recover it entirely during the subsequent interglacial (glacial).
1. The effects of moisture conditions, seed morphology, vegetation structure and hydrodynamic variables on seed retention were examined in a system where the dominant dispersal agent is water. ...Experiments were conducted in a tidal salt marsh and in a flume facility where hydrodynamic variables could be controlled. 2. Moisture condition of seeds greatly influenced which factors were most important in determining seed retention. Seed type (buoyancy) was the most important factor when seeds were dry with seeds possessing very low floating capacity (Plantago maritima) being retained in greater numbers than seeds with intermediate floating capacities (Suaeda maritima and Elytrigia atherica). 3. In contrast, hydrodynamic variables dominated retention processes when seeds were waterlogged. The application of waves in addition to flow velocity dislodged more seeds than flow velocity alone. 4. Vegetation structure influenced retention in both dry and wet conditions but less so than other factors. Denser, less rigid vegetation types retained greater numbers of seeds than more open, more rigid vegetation types. 5. Results suggest that buoyancy traits appear to determine whether seeds move in the drier summer and autumn months after initial detachment from parent plants but the intensity of wave action will determine whether waterlogged seeds stay in a microsite during the wetter months of late autumn to early spring.
While the key role of termites in the decomposition of litter in the tropics has been acknowledged for a long time, much less information exists on their importance in the recycling of dung of ...primary consumers, especially herbivores. A review of published studies shows that a diverse group of termites (at least 126 species) has been reported to feed on a wide range of mammalian dung (18 species). Predominantly, wood-feeding and polyphagous wood-litter feeding species were found to feed also frequently on dung. Moreover, we found that termites can quickly remove large amounts of mammalian dung, especially in the dry season, when on average about 1/3 of the dung deposited in a given habitat is removed by termites within one month (with the highest rates observed in savannas). No distinctive preference for mammalian dung over other organic food sources was observed for fungusgrowing termites (Macrotermitinae), whereas the majority of the non-fungus growing taxa studied prefer dung over other food. As termites bring large quantities of dung below the soil surface, disturb and enrich soils with nutrients, dung feeding by termites appears to be a previously underestimated process important in the functioning of tropical ecosystems. PUBLICATION ABSTRACT
Abstract
For the past century, woody plants have increased in grasslands and savannas worldwide. Woody encroachment may significantly alter ecosystem functioning including fire regimes, herbivore ...carrying capacity, biodiversity and carbon storage capacity. Traditionally, increases in woody cover and density have been ascribed to changes in the disturbance regime (fire and herbivores) or rainfall. Increased atmospheric
CO
2
concentrations may also contribute, by increasing growth rates of trees relative to grasses. This hypothesis is still heavily debated because usually potential
CO
2
effects are confounded by changes in land use (disturbance regime). Here we analyse changes in woody density in fire experiments at three sites in South African savannas where the disturbance regime (fire and herbivores) was kept constant for 30 and 50 years. If global drivers had significant effects on woody plants, we would expect significant increases in tree densities and biomass over time under the constant disturbance regime. Woody density remained constant in a semiarid savanna but tripled in a mesic savanna between the 1970s and 1990s. At the third site, a semiarid savanna near the southern limits of the biome, tree density doubled from the mid 1990s to 2010. Interpretation of the causes is confounded by population recovery after clearing, but aerial photograph analysis on adjacent non‐cleared areas showed an accompanying 48% increase in woody cover. Increased
CO
2
concentrations are consistent with increased woody density while other global drivers (rainfall) remained constant over the duration of the experiments. The absence of a response in one semiarid savanna could be explained by a smaller carbon sink capacity of the dominant species, which would therefore benefit less from increased
CO
2
. Understanding how savannas and grasslands respond to increased
CO
2
and identifying the causes of woody encroachment are essential for the successful management of these systems.
To determine the effect of swine hepatitis E virus (HEV) infection on pregnant gilts, their fetuses, and offspring, 12 gilts were intravenously inoculated with swine HEV. Six gilts, who were not ...inoculated, served as controls. All inoculated gilts became actively infected and shed HEV in feces, but vertical transmission was not detected in the fetuses. There was no evidence of clinical disease in the gilts or their offspring. Mild multifocal lymphohistiocytic hepatitis was observed in 4 of 12 inoculated gilts. There was no significant effect of swine HEV on fetal size, fetal viability, or offspring birth weight or weight gain. The offspring acquired anti-HEV colostral antibodies but remained seronegative after the antibodies waned by 71 days of age. Swine HEV infection induced subclinical hepatitis in pregnant gilts, but had no effect on the gilts' reproductive performance, or the fetuses or offspring. Fulminant hepatitis associated with HEV infection was not reproduced in gilts.
Recent years have seen major changes in clinical practice which may have affected the incidence rates of pheochromocytoma(PCC)/sympathetic paraganglioma(sPGL). There is, however, a lack of up-to-date ...information describing trends in these incidence rates.
We searched the Dutch pathology registry to identify all histopathologically confirmed cases of PCC/sPGL diagnosed between 1995 and 2015. We calculated incidence rates according to age category as well as age-standardized incidence rates (ASR). We also searched Medline and Embase to find data on nationwide incidence rates of PCC/sPGL.
The nationwide pathology study revealed a total of 1493 patients with either PCC or sPGL. The ASR for PCC increased from 0.29 (95% CI: 0.24–0.33) to 0.46 (95% CI: 0.39–0.53) per 100,000 person-years in the periods 1995–1999 and 2011–2015, respectively. For sPGL the ASR in these same periods were 0.08 (95% CI: 0.06–0.10) and 0.11 (95% CI: 0.09–0.13) per 100,000 person-years, respectively. Concomitantly, PCC size decreased (β −0.17; P < .001) and age at diagnosis increased (β 0.13; P = .001). Our systematic search yielded 3 papers reporting on a total of 530 PCC/sPGL cases, showing a combined annual incidence rate varying from 0.04 to 0.21 per 100,000 person-years.
Incidence rates of PCC/sPGL have increased significantly over the past two decades. This trend coincides with a higher age and a smaller tumor size at diagnosis. Most likely these observations are at least in part the result of changes in clinical practice during the study period, with a more intensified use of both imaging studies and biochemical tests for detecting PCC/sPGL.
•Up-to-date epidemiological data on PCC/sPGL are lacking.•The incidence rate of PCC/sPGL has increased significantly during the past two decades.•This rise in incidence rate is accompanied by a reduction in tumor size and a higher age at diagnosis.•The observed epidemiological changes are most likely the result of more intensified use of better diagnostics.
Biomes are important constructs for organizing understanding of how the worlds’ major terrestrial ecosystems differ from one another and for monitoring change in these ecosystems. Yet existing biome ...classification schemes have been criticized for being overly subjective and for explicitly or implicitly invoking climate. We propose a new biome map and classification scheme that uses information on (i) an index of vegetation productivity, (ii) whether the minimum of vegetation activity is in the driest or coldest part of the year, and (iii) vegetation height. Although biomes produced on the basis of this classification show a strong spatial coherence, they show little congruence with existing biome classification schemes. Our biome map provides an alternative classification scheme for comparing the biogeochemical rates of terrestrial ecosystems. We use this new biome classification scheme to analyse the patterns of biome change observed over recent decades. Overall, 13% to 14% of analysed pixels shifted in biome state over the 30‐year study period. A wide range of biome transitions were observed. For example, biomes with tall vegetation and minimum vegetation activity in the cold season shifted to higher productivity biome states. Biomes with short vegetation and low seasonality shifted to seasonally moisture‐limited biome states. Our findings and method provide a new source of data for rigorously monitoring global vegetation change, analysing drivers of vegetation change and for benchmarking models of terrestrial ecosystem function.
Abstract
Context
Pretreatment with α-adrenergic receptor blockers is recommended to prevent hemodynamic instability during resection of a pheochromocytoma or sympathetic paraganglioma (PPGL).
...Objective
To determine which type of α-adrenergic receptor blocker provides the best efficacy.
Design
Randomized controlled open-label trial (PRESCRIPT; ClinicalTrials.gov NCT01379898)
Setting
Multicenter study including 9 centers in The Netherlands.
Patients
134 patients with nonmetastatic PPGL.
Intervention
Phenoxybenzamine or doxazosin starting 2 to 3 weeks before surgery using a blood pressure targeted titration schedule. Intraoperative hemodynamic management was standardized.
Main Outcome Measures
Primary efficacy endpoint was the cumulative intraoperative time outside the blood pressure target range (ie, SBP >160 mmHg or MAP <60 mmHg) expressed as a percentage of total surgical procedure time. Secondary efficacy endpoint was the value on a hemodynamic instability score.
Results
Median cumulative time outside blood pressure targets was 11.1% (interquartile range IQR: 4.3–20.6 in the phenoxybenzamine group compared to 12.2% (5.3–20.2) in the doxazosin group (P = .75, r = 0.03). The hemodynamic instability score was 38.0 (28.8–58.0) and 50.0 (35.3–63.8) in the phenoxybenzamine and doxazosin group, respectively (P = .02, r = 0.20). The 30-day cardiovascular complication rate was 8.8% and 6.9% in the phenoxybenzamine and doxazosin group, respectively (P = .68). There was no mortality after 30 days.
Conclusions
The duration of blood pressure outside the target range during resection of a PPGL was not different after preoperative treatment with either phenoxybenzamine or doxazosin. Phenoxybenzamine was more effective in preventing intraoperative hemodynamic instability, but it could not be established whether this was associated with a better clinical outcome.
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