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Yadvinder Malhi, Cécile A J Girardin, Gregory R Goldsmith, Christopher E Doughty, Norma Salinas, Daniel B Metcalfe, Walter Huaraca Huasco, Javier E Silva-Espejo, Jhon Del Aguilla-Pasquell, Filio Farfán Amézquita, Luiz E O C Aragão, Rossella Guerrieri, Françoise Yoko Ishida, Nur H A Bahar, William Farfan-Rios, Oliver L Phillips, Patrick Meir, Miles Silman
Why do forest productivity and biomass decline with elevation? To address this question, research to date generally has focused on correlative approaches describing changes in woody growth and biomass with elevation. We present a novel, mechanistic approach to this question by quantifying the autotrophic carbon budget in 16 forest plots along a 3300 m elevation transect in Peru. Low growth rates at high elevations appear primarily driven by low gross primary productivity (GPP), with little shift in either carbon use efficiency (CUE) or allocation of net primary productivity (NPP) between wood, fine roots and canopy...
October 21, 2016: New Phytologist
Víctor Resco de Dios, Arthur Gessler, Juan Pedro Ferrio, Josu G Alday, Michael Bahn, Jorge Del Castillo, Sébastien Devidal, Sonia García-Muñoz, Zachary Kayler, Damien Landais, Paula Martín-Gómez, Alexandru Milcu, Clément Piel, Karin Pirhofer-Walzl, Olivier Ravel, Serajis Salekin, David T Tissue, Mark G Tjoelker, Jordi Voltas, Jacques Roy
BACKGROUND: Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance, and other cell and leaf-level processes over ~24 h under controlled laboratory conditions. The influence of such circadian regulation over whole-canopy fluxes remains uncertain; diurnal CO2 and H2O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other environmental factors. We tested whether circadian regulation would affect plant and canopy gas exchange at the Montpellier European Ecotron...
October 20, 2016: GigaScience
Changliang Shao, Jiquan Chen, Linghao Li, Gang Dong, Juanjuan Han, Michael Abraha, Ranjeet John
Quantifying the surface energy fluxes of grazed and ungrazed steppes is essential to understand the roles of grasslands in local and global climate and in land use change. We used paired eddy-covariance towers to investigate the effects of grazing on energy balance (EB) components: net radiation (Rn ), latent heat (LE), sensible heat (H), and soil heat (G) fluxes on adjacent grazed and ungrazed areas in a desert steppe of the Mongolian Plateau for a two-year period (2010-2012). Near 95% of Rn was partitioned as LE and H, whereas the contributions of G and other components of the EB were 5% at an annual scale...
October 20, 2016: Ecological Applications: a Publication of the Ecological Society of America
K Huusko, A L Ruotsalainen, A M Markkola
Soil fungal community and dominant mycorrhizal types are known to shift along with plant community changes during primary succession. However, it is not well understood how and why root fungal symbionts and colonization types vary within the plant host when the host species is able to thrive both at young and at old successional stages with different light and nutrient resource availability. We asked (i) how root fungal colonization of Deschampsia flexuosa (Poaceae) by arbuscular mycorrhizal (AM) fungi and dark septate endophytes (DSE) changes along a postglacial primary successional land uplift gradient...
October 19, 2016: Mycorrhiza
Andrew N Gherlenda, Ben D Moore, Anthony M Haigh, Scott N Johnson, Markus Riegler
BACKGROUND: Climate change factors such as elevated atmospheric carbon dioxide concentrations (e[CO2]) and altered rainfall patterns can alter leaf composition and phenology. This may subsequently impact insect herbivory. In sclerophyllous forests insects have developed strategies, such as preferentially feeding on new leaf growth, to overcome physical or foliar nitrogen constraints, and this may shift under climate change. Few studies of insect herbivory at elevated [CO2] have occurred under field conditions and none on mature evergreen trees in a naturally established forest, yet estimates for leaf area loss due to herbivory are required in order to allow accurate predictions of plant productivity in future climates...
October 19, 2016: BMC Ecology
Pierre D Thiriet, Antonio Di Franco, Adrien Cheminée, Paolo Guidetti, Olivier Bianchimani, Solène Basthard-Bogain, Jean-Michel Cottalorda, Hazel Arceo, Joan Moranta, Pierre Lejeune, Patrice Francour, Luisa Mangialajo
In Mediterranean subtidal rocky reefs, Cystoseira spp. (Phaeophyceae) form dense canopies up to 1 m high. Such habitats, called 'Cystoseira forests', are regressing across the entire Mediterranean Sea due to multiple anthropogenic stressors, as are other large brown algae forests worldwide. Cystoseira forests are being replaced by structurally less complex habitats, but little information is available regarding the potential difference in the structure and composition of fish assemblages between these habitats...
2016: PloS One
C Guillermo Bueno, Scott N Williamson, Isabel C Barrio, Ágústa Helgadóttir, David S HiK
In tundra ecosystems, bryophytes influence soil processes directly and indirectly through interactions with overstory shrub species. We experimentally manipulated moss cover and measured seasonal soil properties and processes under two species of deciduous shrubs with contrasting canopy structures, Salix planifolia pulchra and Betula glandulosa-nana complex. Soil properties (seasonal temperature, moisture and C:N ratios) and processes (seasonal litter decomposition and soil respiration) were measured over twelve months...
2016: PloS One
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
Luis Abdala-Roberts, Johnattan Hernández-Cumplido, Luis Chel-Guerrero, David Betancur-Ancona, Betty Benrey, Xoaquín Moreira
PREMISE OF STUDY: Although there is increasing recognition of the effects of plant intraspecific diversity on consumers, the mechanisms by which such effects cascade-up to higher trophic levels remain elusive. METHODS: We evaluated the effects of plant (lima bean, Phaseolus lunatus) intraspecific diversity on a suite of insect herbivores (leaf-chewers, aphids, and seed-eating beetles) and their third trophic-level associates (parasitoids and aphid-tending ants)...
October 18, 2016: American Journal of Botany
Benoit Gendreau-Berthiaume, S Ellen Macdonald, J John Stadt
Understanding processes driving mortality in forests is important for comprehension of natural stand dynamics and for informing natural disturbance-based ecosystem management. There has been considerable study of mortality in forests during the self-thinning phase but we know much less about processes driving mortality in stands at later successional stages. We addressed this through study of five 1-ha spatially explicit permanent plots in mature (111-186 yr old in 2012) Pinus contorta stands in the Canadian Rocky Mountains using data from repeated measurements over a 45-yr period, dendrochronological information, and point pattern analysis...
July 2016: Ecological Applications: a Publication of the Ecological Society of America
Daniel A Nidzgorski, Sarah E Hobbie
Many urban waterways suffer from excess nitrogen (N) and phosphorus (P), feeding algal blooms, which cause lower water clarity and oxygen levels, bad odor and taste, and the loss of desirable species. Nutrient movement from land to water is likely to be influenced by urban vegetation, but there are few empirical studies addressing this. In this study, we examined whether or not urban trees can reduce nutrient leaching to groundwater, an important nutrient export pathway that has received less attention than stormwater...
July 2016: Ecological Applications: a Publication of the Ecological Society of America
Camille Stevens-Rumann, Penelope Morgan
Most models project warmer and drier climates that will contribute to larger and more frequent wildfires. However, it remains unknown how repeated wildfires alter post-fire successional patterns and forest structure. Here, we test the hypothesis that the number of wildfires, as well as the order and severity of wildfire events interact to alter forest structure and vegetation recovery and implications for vegetation management. In 2014, we examined forest structure, composition, and tree regeneration in stands that burned 1-18 yr before a subsequent 2007 wildfire...
September 2016: Ecological Applications: a Publication of the Ecological Society of America
Benedicte Bachelot, María Uriarte, Jess K Zimmerman, Jill Thompson, Jonathan W Leff, Ava Asiaii, Jenny Koshner, Krista McGuire
Our understanding of the long-lasting effects of human land use on soil fungal communities in tropical forests is limited. Yet, over 70% of all remaining tropical forests are growing in former agricultural or logged areas. We investigated the relationship among land use history, biotic and abiotic factors, and soil fungal community composition and diversity in a second-growth tropical forest in Puerto Rico. We coupled high-throughput DNA sequencing with tree community and environmental data to determine whether land use history had an effect on soil fungal community descriptors...
September 2016: Ecological Applications: a Publication of the Ecological Society of America
Wei Li, Lorenzo Katin-Grazzini, Sanalkumar Krishnan, Chandra Thammina, Rania El-Tanbouly, Huseyin Yer, Emily Merewitz, Karl Guillard, John Inguagiato, Richard J McAvoy, Zongrang Liu, Yi Li
When subjected to shade, plants undergo rapid shoot elongation, which often makes them more prone to disease and mechanical damage. Shade-tolerant plants can be difficult to breed; however, they offer a substantial benefit over other varieties in low-light areas. Although perennial ryegrass (Lolium perenne L.) is a popular species of turf grasses because of their good appearance and fast establishment, the plant normally does not perform well under shade conditions. It has been reported that, in turfgrass, induced dwarfism can enhance shade tolerance...
2016: Frontiers in Plant Science
H Calvete-Sogo, I González-Fernández, H García-Gómez, R Alonso, S Elvira, J Sanz, V Bermejo-Bermejo
Ozone (O3) critical levels (CLe) are still poorly developed for herbaceous vegetation. They are currently based on single species responses which do not reflect the multi-species nature of semi-natural vegetation communities. Also, the potential effects of other factors like the nitrogen (N) input are not considered in their derivation, making their use uncertain under natural conditions. Exposure- and dose-response relationships were derived from two open-top chamber experiments exposing a mixture of 6 representative annual Mediterranean pasture species growing in natural soil to 4 O3 fumigation levels and 3 N inputs...
October 14, 2016: Environmental Pollution
Zhenyi Chen, Cheng Liu, Wenqing Liu, Tianshu Zhang, Jin Xu
Despite extensive efforts into the characterization of air pollution during the past decade, concurrent real-time characterization of aerosol and NO2 as well as satellite observation above the urban canopy in the megacity of Beijing has sparsely been performed to date. We conducted a simultaneous real-time measurement of aerosol and NO2 in urban Beijing in a pollution episode from November 25, 2015 to December 2, 2015. The aerosol extinction coefficient was measured by a 532 Mie lidar and the NO2 concentration by a Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)...
October 14, 2016: Science of the Total Environment
Robert Marshall Beresford, Joy Lorraine Tyson, Warwick Ralph Henshall
A weather-based disease prediction model for bacterial canker of kiwifruit (known worldwide as Psa; Pseudomonas syringae pv. actinidiae biovar 3) was developed using a new mechanistic scheme for bacterial disease forecasters, the multiplication and dispersal concept. Bacterial multiplication is estimated from a temperature function, the M index, accumulated from hourly air temperature over 3 days for hours when the leaf canopy is wet. Rainfall provides free water to move inoculum to infection sites and the daily risk indicator, the R index, is the 3-day accumulation of the M index, output on days with total rainfall > 1 mm; otherwise R is zero...
October 17, 2016: Phytopathology
B L Aigner, D A Herbert, G P Dively, D Venugopal, J Whalen, B Cissel, T P Kuhar, C C Brewster, J W Hogue, E Seymore
Sampling soybean fields for the brown marmorated stink bug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), can be challenging. Both adults and nymphs have a "startle response" and drop to the ground with even the slightest disturbance. This behavior could reduce the effectiveness of the traditional sweep net and ground cloth sampling methods. In 2013 and 2014, in Virginia, Delaware, and Maryland, we evaluated a visual plant inspection method that consisted of counting the number of brown marmorated stink bug nymphs and adults seen on soybean plants in a 2-min inspection period while walking carefully between two rows...
October 15, 2016: Journal of Economic Entomology
Hemmat Khattab, Zeinab El Marid
Now days, production of fuels and petrochemicals from renewable lignocellulosic biomass is an indispensable issue to meet the growing energy demand. Meanwhile, the changes in the climate and soil topography influence the growth and development as well as canopy level of the lignocellulosic biomass. In this study, Zilla spinosa Turr (Zilla) plants with similar age and size were collected from three main sectors (upstream, midstream, and downstream) of Wadi Hagul during spring (April) and summer (July) seasons...
October 14, 2016: Zeitschrift Für Naturforschung. C, A Journal of Biosciences
Jaime L Stephens, Eric C Dinger, John D Alexander, Sean R Mohren, C John Ralph, Daniel A Sarr
We examined avian community ecology in the Klamath Ecoregion and determined that individual bird species co-exist spatially to form 29 statistically distinguishable bird groups. We identified climate, geography, and vegetation metrics that are correlated with these 29 bird groups at three scales: Klamath Ecoregion, vegetation formation (agriculture, conifer, mixed conifer/hardwood, shrubland), and National Park Service unit. Two climate variables (breeding season mean temperature and temperature range) and one geography variable (elevation) were correlated at all scales, suggesting that for some vegetation formations and park units there is sufficient variation in climate and geography to be an important driver of bird communities, a level of variation we expected only at the broader scale...
2016: PloS One
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