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D L Hoover, A K Knapp, M D Smith
Extreme heat waves and drought are predicted to increase in frequency and magnitude with climate change. These extreme events often co-occur, making it difficult to separate their direct and indirect effects on important ecophysiological and carbon cycling processes such as photosynthesis. Here, we assessed the independent and interactive effects of experimental heat waves and drought on photosynthesis in Andropogon gerardii, a dominant C4 grass in a native mesic grassland. We experimentally imposed a two-week heat wave at four intensity levels under two contrasting soil moisture regimes: a well-watered control and an extreme drought...
October 18, 2016: Oecologia
V Yatat, P Couteron, J J Tewa, S Bowong, Y Dumont
Fires and mean annual rainfall are major factors that regulate woody and grassy biomasses in savanna ecosystems. Within the savanna biome, conditions of long-lasting coexistence of trees and grasses have been often studied using continuous-time modelling of tree-grass competition. In these studies, fire is a time-continuous forcing while the relationship between woody plant size and fire-sensitivity is not systematically considered. In this paper, we propose a new mathematical framework to model tree-grass interactions that takes into account both the impulsive nature of fire occurrence and size-dependent fire sensitivity (via two classes of woody plants)...
September 22, 2016: Journal of Mathematical Biology
Peter M Homyak, Matthew Kamiyama, James O Sickman, Joshua P Schimel
Soils are an important source of NO, particularly in dry lands because of tradeoffs that develop between biotic and abiotic NO-producing processes when soils dry out. Understanding how drier climates may offset the balance of these tradeoffs as soils transition toward more arid states is, therefore, critical to estimating global NO budgets, especially because drylands are expected to increase in size. We measured NO emission pulses after wetting soils from similar lithologies along an altitudinal gradient in the Sierra Nevada, CA, where mean annual precipitation varied from 670 to 1,500 mm...
September 19, 2016: Global Change Biology
Nadine Brinkmann, Werner Eugster, Roman Zweifel, Nina Buchmann, Ansgar Kahmen
Temperate forests are expected to be particularly vulnerable to drought and soil drying because they are not adapted to such conditions and perform best in mesic environments. Here we ask (i) how sensitively four common temperate tree species (Fagus sylvatica, Picea abies, Acer pseudoplatanus and Fraxinus excelsior) respond in their water relations to summer soil drying and seek to determine (ii) if species-specific responses to summer soil drying are related to the onset of declining water status across the four species...
September 8, 2016: Tree Physiology
Sharon B Gray, Orla Dermody, Stephanie P Klein, Anna M Locke, Justin M McGrath, Rachel E Paul, David M Rosenthal, Ursula M Ruiz-Vera, Matthew H Siebers, Reid Strellner, Elizabeth A Ainsworth, Carl J Bernacchi, Stephen P Long, Donald R Ort, Andrew D B Leakey
Stimulation of C3 crop yield by rising concentrations of atmospheric carbon dioxide ([CO2]) is widely expected to counteract crop losses that are due to greater drought this century. But these expectations come from sparse field trials that have been biased towards mesic growth conditions. This eight-year study used precipitation manipulation and year-to-year variation in weather conditions at a unique open-air field facility to show that the stimulation of soybean yield by elevated [CO2] diminished to zero as drought intensified...
2016: Nature Plants
Linda E Neaves, Greta J Frankham, Siobhan Dennison, Sean FitzGibbon, Cheyne Flannagan, Amber Gillett, Emily Hynes, Kathrine Handasyde, Kristofer M Helgen, Kyriakos Tsangaras, Alex D Greenwood, Mark D B Eldridge, Rebecca N Johnson
The Australian continent exhibits complex biogeographic patterns but studies of the impacts of Pleistocene climatic oscillation on the mesic environments of the Southern Hemisphere are limited. The koala (Phascolarctos cinereus), one of Australia's most iconic species, was historically widely distributed throughout much of eastern Australia but currently represents a complex conservation challenge. To better understand the challenges to koala genetic health, we assessed the phylogeographic history of the koala...
2016: PloS One
Marcella A Windmuller-Campione, James N Long
As forest communities continue to experience interactions between climate change and shifting disturbance regimes, there is an increased need to link ecological understanding to applied management. Limber pine (Pinus flexilis James.), an understudied species of western North America, has been documented to dominate harsh environments and thought to be competitively excluded from mesic environments. An observational study was conducted using the Forest Inventory and Analysis Database (FIAD) to test the competitive exclusion hypothesis across a broad elevational and geographic area within the Intermountain West, USA...
2016: PloS One
L Zapletalová, M Zapletal, M Konvička
A comparison of 95 species of Central European moths, representing 11 families and inhabiting various habitats, was carried out in order to detect the potential impact of biotope on the ultraviolet (UV) light reflectance of their wings. Based on digitized photographs taken under UV light conditions, a phylogeny-controlled redundancy analysis relating UV reflectance to preferred habitat type (xerophilous, mesophilous, and hygrophilous) and habitat openness (open, semiopen, and closed) was carried out. Species preferring hygrophilous habitats displayed significantly higher UV wing reflectance than species inhabiting xerothermic and mesic habitats, and this pattern remained significant even after controlling for phyletic relationships...
October 2016: Environmental Entomology
Matthew B Dickinson, Todd F Hutchinson, Mark Dietenberger, Frederick Matt, Matthew P Peters
Mesophytic species (esp. Acer rubrum) are increasingly replacing oaks (Quercus spp.) in fire-suppressed, deciduous oak-hickory forests of the eastern US. A pivotal hypothesis is that fuel beds derived from mesophytic litter are less likely than beds derived from oak litter to carry a fire and, if they do, are more likely to burn at lower intensities. Species effects, however, are confounded by topographic gradients that affect overstory composition and fuel bed decomposition. To examine the separate and combined effects of litter species composition and topography on surface fuel beds, we conducted a common garden experiment in oak-hickory forests of the Ohio Hills...
2016: PloS One
Kristen K Beck, Andrew S Medeiros, Sarah A Finkelstein
A Holocene lake sediment record spanning the past 7300 years from Wishart Lake in the Turkey Lakes Watershed in the Hemi-Boreal of central Ontario, Canada, was used to evaluate the potential drivers of long-term change in diatom assemblages at this site. An analysis of diatom assemblages found that benthic and epiphytic taxa dominated the mid-Holocene (7300-4000 cal yr BP), indicating shallow, oligotrophic, circum-neutral conditions, with macrophytes present. A significant shift in diatom assemblages towards more planktonic species (mainly Cyclotella sensu lato, but also several species of Aulacoseira, and Tabellaria flocculosa) occurred ~4000 cal yr BP...
2016: PloS One
Li Lin, Biao Zhu, Chengrong Chen, Zhenhua Zhang, Qi-Bing Wang, Jin-Sheng He
Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock...
2016: Scientific Reports
Lindsey C Slaughter, Rebecca L McCulley
Cool season grasses host multiple fungal symbionts, such as aboveground Epichloë endophytes and belowground arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSEs). Asexual Epichloë endophytes can influence root colonization by AMF, but the type of interaction-whether antagonistic or beneficial-varies. In Schedonorus arundinaceus (tall fescue), Epichloë coenophiala can negatively affect AMF, which may impact soil properties and ecosystem function. Within field plots of S. arundinaceus that were either E...
October 2016: Microbial Ecology
Julia I Chapman, Ryan W McEwan
Ecological communities are structured in response to spatial and temporal variation of numerous factors, including edaphic conditions, biotic interactions, climatic patterns and disturbance regimes. Widespread anthropogenic factors such as timber harvesting can create long-lasting impacts, obscuring the relationship between community structure and environmental conditions. Minimally impacted systems such as old-growth forests can serve as a useful ecological baseline for predicting long-term compositional shifts...
2016: PloS One
Larisa Mešić Ðogić, Dragana Mićić, Feđa Omeragić, Refka Kovač, Seid Fazlagić
Aim To establish a correlation between positive values of IGFBP-1(>10 mg/L, Actim Partus Test, APT) and premature cervical ripening in imminent preterm labor. Methods A prospective study was conducted in primary health care centers in Tuzla, Gynecology and Obstetrics Clinic of the University Clinical Centre in Tuzla and General Hospital Tešanj. The study included 50 women (singleton pregnancy, 28-37 week) with imminent preterm labor diagnosed by cervical biometry and modified Bishop score) (examinees) and 30 healthy pregnant women (control group)...
August 1, 2016: Medicinski Glasnik
James H McMahon, Tim Spelman, Nathan Ford, Jane Greig, Anita Mesic, Charles Ssonko, Esther C Casas, Daniel P O'Brien
BACKGROUND: Antiretroviral therapy (ART) treatment interruptions lead to poor clinical outcomes with unplanned or unstructured TIs (uTIs) likely to be underreported. This study describes; uTIs, their risk factors and association with survival. METHODS: Analysis of ART programmatic data from 11 countries across Asia and Africa between 2003 and 2013 where an uTI was defined as a ≥90-day patient initiated break from ART calculated from the last day the previous ART prescription would have run out until the date of the next ART prescription...
2016: AIDS Research and Therapy
Richard J Douglass, María Victoria Vadell
We use data collected on 18,1-ha live trapping grids monitored from 1994 through 2005 and on five of those grids through 2013 in the mesic northwestern US to illustrate the complexity of the deer mouse (Peromyscus maniculatus)/Sin Nombre virus (SNV) host-pathogen system. Important factors necessary to understand zoonotic disease ecology include those associated with distribution and population dynamics of reservoir species as well as infection dynamics. Results are based on more than 851,000 trap nights, 16,608 individual deer mice and 10,572 collected blood samples...
June 2016: Ecosphere
J Judson Wynne, William A Shear
Austrotyla awishoshola n. sp. is described from the moss gardens of one lava tube cave in El Malpais National Monument, Cibola Co., New Mexico. Most chordeumatidans require mesic conditions, and these environments are limited to moss gardens in several cave entrances and beneath cave skylights in El Malpais. Presently, this species is known from the moss gardens of a single of cave in the monument. We suggest A. awishoshola may be a climatic relict, having become restricted to the cave environment following the end of the Pleistocene...
2016: Zootaxa
Vanessa Haverd, Anders Ahlström, Benjamin Smith, Josep G Canadell
Recent evidence shows that warm semi-arid ecosystems are playing a disproportionate role in the inter-annual variability and greening trend of the global carbon cycle given their mean lower productivity when compared with other biomes (Ahlström et al. (2015)). Using multiple observations (land-atmosphere fluxes, biomass, streamflow and remotely sensed vegetation cover) and two state-of-the-art biospheric models, we show that climate variability and extremes lead to positive or negative responses in the biosphere, depending on vegetation type...
July 8, 2016: Global Change Biology
Bryan G Valencia, Frazer Matthews-Bird, Dunia H Urrego, Joseph J Williams, William D Gosling, Mark Bush
Microrefugia are important for supporting populations during periods of unfavourable climate change and in facilitating rapid migration as conditions ameliorate. With ongoing anthropogenic climate change, microrefugia could have an important conservation value; however, a simple tool has not been developed and tested to predict which settings are microrefugial. We provide a tool based on terrain ruggedness modelling of individual catchments to predict Andean microrefugia. We tested the predictions using nine Holocene Polylepis pollen records...
October 2016: New Phytologist
Agnieszka Gudowska, Leigh Boardman, John S Terblanche
The discontinuous gas exchange (DGE) pattern of respiration shown by many arthropods includes periods of spiracle closure (C-phase) and is largely thought to serve as a physiological adaptation to restrict water loss in terrestrial environments. One major challenge to this hypothesis is to explain the presence of DGE in insects in moist environments. Here, we show a novel ecological correlate of the C-phase, namely, diving behaviour in mesic Paracinema tricolor grasshoppers. Notably, maximal dive duration is positively correlated with C-phase length, even after accounting for mass scaling and absolute metabolic rate...
August 15, 2016: Journal of Experimental Biology
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