Search results for "seasonal"
showing 10 items of 484 documents
Soil and Plant Nitrogen Pools as Related to Plant Diversity in an Experimental Grassland
2007
Increasing plant species richness decreases soil NO 3 - concentrations in experimental plant mixtures, but the role of particular plant functional groups has remained unclear. Most analyses have focused on particular times of the year or were restricted to NO 3 - . We tested whether plant species richness or particular plant functional groups affect the size of plant-available N pools in soil (KCl-extractable NO 3 - , dissolved inorganic N and organic N [DON] and total dissolved N [TDN] in soil solution) and N concentrations and pools in aboveground biomass. Furthermore, we assessed seasonal variations in the effects of plant species richness and plant functional groups. The experimental gr…
Variation characteristics of soil respiration fluxes in four types of grassland communities under different precipitation intensity
2005
A two consecutive years’ field experiment was carried out on four types of semiarid grassland along precipitation gradient in Xilin River Basin of Inner Mongolia during 2001–2003 using a static enclosed black chamber technique. The variation characteristics of soil respiration fluxes from four different types of grassland along precipitation gradient were compared. The possible effect of water-heat factors on characteristics of grassland soil respiration was statistically analyzed and the numerical relational model between soil respiration and water-heat factors was established. Meanwhile the soil CO2 annual emissions of different types of grassland were estimated based on the consecutive a…
Predation risk and habitat selection of Australian house mice , Mus domesticus , during an incipient plague: desperate behaviour due to food depletion
2002
We studied habitat selection and foraging behaviour of the house mouse (Mus domesticus) related to increasing mouse densities and depleting food resources over the breeding season. The study was conducted during the increase phase of an incipient outbreak of mice in a grain-growing area of southeastern Australia. A 3-year rotation created a mosaic of large paddocks of grain crop, pasture, and fallow. The narrow fence lines between paddocks provide an important stable habitat for the mice. We monitored population densities with live-trapping and habitat preference by measuring giving-up densities (GUD) using artificial food patches. Food patches were established in crop fields, fence lines, …
Vertical distribution of planktonic rotifers in a karstic meromictic lake
1993
Vertical distribution of planktonic rotifers is described in relation to temperature and oxygen in Lake La Cruz, a single-doline, closed karstic lake (121 m diameter and 25 m maximum depth) which shows iron meromixis. Samples were taken by peristaltic pumping at 10 cm depth intervals in the oxycline zone from June 1987 to September 1988. A model of rotifer vertical structure in stratified lakes is proposed. Rotifers concentrate their populations at the depths with intense gradients. As stratification develops some rotifer populations show a downward migration following the thermocline and some others show an upward migration following the oxycline. The production-respiration balance in the …
Zooplankton communities in doline lakes and pools, in relation to some bathymetric parameters and physical and chemical variables
1999
The zooplankton communities from several lakes and pools in three zones of a karstic area in central Spain were studied in spring and early autumn, in relation to morphometric, physical and chemical characteristics of the lakes. Zooplankton diversity was higher in autumn than in spring and it was positively correlated with lake size (area and depth) in spring, but not in early autumn. This effect is partially explained by the sharp zooplankton stratification in deep lakes, in early autumn. Some morphometric characteristics of lake basins were also correlated with the structure of zooplank- ton communities. Principal component analyses (PCA) and Two-Way Indicator Species Analysis (TWINSPAN) …
Ash resuspension related to the 2011–2012 Cordón Caulle eruption, Chile, in a rural community of Patagonia, Argentina
2017
Abstract The 2011–2012 Cordon Caulle eruption emitted about 1 km3 of rhyodacitic tephra. Dominant westerly winds in the region caused most of the primary tephra to deposit in neighboring Argentina. In addition to the impact of widespread dispersal and fallout of primary tephra during the eruption, Argentina was also significantly affected by remobilization of the primary ash even several years after the climactic phase of the eruption. In this mixed methods study, we combine aspects of natural and social sciences to characterize the ash resuspension events associated with the 2011–2012 Cordon Caulle deposits and assess the impacts on the Argentinian farming community of Ingeniero Jacobacci …
Control of Seasonality and Interannual to Centennial Climate Variability in the Caribbean During the Holocene—Combining Coral Records, Stalagmite Rec…
2014
This study aimed at quantifying the amplitudes of seasonality and interannual to centennial climate variability in the Caribbean region throughout the Holocene, by using marine (shallow-water corals) and terrestrial (speleothems) climate archives, and climate model simulations (COSMOS). Sea-surface temperature (SST) variability on interdecadal to multidecadal timescales was more pronounced during the mid-Holocene compared to the late Holocene. The amplitude of the SST annual cycle was within the present-day range throughout most of the last 6,000 years. Exceptions include slightly increased SST seasonality at 6,200 years ago, which can be attributed mainly to insolation forcing on orbital t…
Pre-Migratory Movements of Adult Montagu's HarriersCircus pygargus
2008
Pre-migratory and migratory movements of Montagu's Harrier Circus pygargus, a long-distance migrant, are poorly documented by ring recoveries and observations. In the present study, we tagged 10 adult Montagu's Harriers in NE Spain with satellite transmitters and tracked their movements until their arrival on the wintering grounds. To identify the end of the breeding season and the onset of the migration based on our satellite-telemetry data we developed and applied a statistical approach, defining the time period between these two events as the pre-migratory stage. We then compared habitat preferences during the breeding season and the pre-migratory stage. The duration of the pre-migratory…
Effects of NH3 and alkaline metals on the formation of particulate sulfate and nitrate in wintertime Beijing
2020
Sulfate and nitrate from secondary reactions remain as the most abundant inorganic species in atmospheric particle matter (PM). Their formation is initiated by oxidation (either in gas phase or particle phase), followed by neutralization reaction primarily by NH3, or by other alkaline species such as alkaline metal ions if available. The different roles of NH3 and metal ions in neutralizing H2SO4 or HNO3, however, are seldom investigated. Here we conducted semi-continuous measurements of SO4 2−, NO3 −, NH4 +, and their gaseous precursors, as well as alkaline metal ions (Na+, K+, Ca2+, and Mg2+) in wintertime Beijing. Analysis of aerosol acidity (estimated from a thermodynamic model) indicat…
Il lavoro nel turismo
2019
Il contributo offre una breve disamina delle principali caratteristiche del mercato del lavoro nel settore del turismo. A partire dall’elemento della stagionalità, che si traduce in esigenze di flessibilità e dinamicità del mercato, si individuano le tipologie contrattuali cui prevalentemente si suole far ricorso. Con l’ausilio di risultanze empiriche, desumibili dalle principali banche dati a disposizione, viene restituito un quadro di modelli organizzativi prevalenti (il contratto di lavoro a tempo determinato, il part-time, il contratto di apprendistato, il lavoro intermittente); in cui, dunque, i contratti diversi dai “classici” modelli a tempo indeterminato e/o tempo pieno costituiscon…