Search results for "Geta"

Nonlinear Time-Series Adaptation for Land Cover Classification

2017

Automatic land cover classification from satellite image time series is of paramount relevance to assess vegetation and crop status, with important implications in agriculture, biofuels, and food. However, due to the high cost and human resources needed to characterize and classify land cover through field campaigns, a recurrent limiting factor is the lack of available labeled data. On top of this, the biophysical–geophysical variables exhibit particular temporal structures that need to be exploited. Land cover classification based on image time series is very complex because of the data manifold distortions through time. We propose the use of the kernel manifold alignment (KEMA) method for…

Variaciones espacio-temporales en la composición y/o abundancia de Hongos Micorrízicos Arbusculares (HMA) en táxones vegetales de interés para la rec…

2019

Successful arbuscular mycorrhizal fungi (AMF) symbiosis in sand dunes is a key factor for the maintenance of stable vegetation. Therefore, the main goal of this work was to study the AMF species associated with sand dunes in the Gulf of Valencia (Spain), as well as the effects of environmental and temporal factors on these AMF communities. In order to achieve these, soil samples from the rhizosphere of four plant species were seasonally collected at 6 sites during 2 years in three habitats. Frequency and relative abundance of AMF among these samples were examined. Among the ten AMF species identified, only Corymbiglomus corymbiforme and Diversispora aurantia (Diversisporaceae) had been prev…

The phenology of submerged macrophytes from Mediterranean wetlands as a sentinel of climate change = La fenologia dels macròfits submergits d'aiguamo…

2018

L’estudi de la fenologia, i.e. la temporització dels esdeveniments biològics recurrents, s’està usant per detectar els efectes del canvi climàtic sobre els organismes. Encara que els macròfits submergits exerceixen una funció clau en l’estructuració dels ecosistemes soms, hi ha poca informació sobre la seua fenologia. Aquesta tesi presenta les primeres dades (de 2014 a 2016) d’un esperable estudi a llarg termini. Els objectius principals son (i) establir la base metodològica per a l’estudi fenològic dels macròfits submergits, (ii) descriure la fenologia reproductiva de 6 espècies (Chara hispida, C. aspera, C. canescens, Nitella hyalina, Stuckenia pectinata i Utricularia australis) en dos ll…

Dynamics of changes in the soil organic matter, functional diversity and C and N fluxes after shift in agricultural practices of an annual crops rota…

2015

International audience; Introduction and objectives Agricultural practices (e.g. crop rotation, tillage) lead to profound changes in soil properties, ecosystem structure (e.g. biodiversity) and functioning (e.g. ecosystem services). Whereas this has been very often characterized in the medium and long terms, little is known so far about how fast soil properties respond to changing practices at the time scale (year to several years) in which farmers take their decision in the management of their crops. In agricultural systems, increasing consideration is given to soil biodiversity, whose role has long been overlooked by agronomists, but whose preservation in now recognized as key for maintai…

Ecosystem Services: From Biodiversity to Society, Part 2

2016

SPE Pôle GESTAD; International audience

Long-term changes in collembolan communities in grazed and non-grazed abandoned arable fields in Denmark

2004

Summary In order to explore long-term changes in microarthropod communities after introduction of livestock grazing in abandoned fields with herb–grass vegetation at Mols, E. Jutland, Denmark, soil and litter samples were collected from 7 pairs (blocks) of grazed and non-grazed plots over a period of 14 years. Sampling began just before fencing and initiation of cattle and sheep grazing in the spring of 1985. The total material included 76 collembolan species; 65 and 68 species were recorded in the grazed and non-grazed plots, respectively. The number of species recorded at individual sampling dates fluctuated considerably through the period. In the vegetation/litter layer the mean number o…

Population dynamics of Cyclotella ocellata (Bacillariophyceae): endogenous and exogenous factors

1999

Population dynamics of Cyclotella ocellata PANTOCSEK were examined from 1991 to 1993 in an oligo-mesotrophic, gravel-pit lake near Madrid (Spain). Monthly and daily sampling was carried out to track seasonal- and auxosporulation dynamics, respectively. This species was the most abundant planktonic diatom in the lake. The population increased steadily in spring until the seasonal peak (3.8.10 6 ind/ L in April) and then abundance declined slowly through late winter. Time series techniques showed that the seasonal dynamics were driven by exogenous factors: there was a relationship between Cyclotella abundance and the chemical environment, both TP (synchronic) and SRSi (with delay). Auxosporul…

Spatial analysis of lanner falcon habitat preferences: Implications for agro-ecosystems management at landscape scale and raptor conservation

2014

Abstract Sicily hosts the largest European population of the endangered lanner falcon, a poorly known species which needs conservation planning based on habitat preferences. A distribution model on 10 × 10 km cells of Sicily was described using Generalized Linear Models and variation partitioning methods. This modelling approach extracted explanatory factors, pure and joint effects of greatest influence from subsets of variables controlled for multi-collinearity and spatial autocorrelation. Analytical cartography used the environmental favourability function to assess habitat preferences, and the insecurity index estimated the degree to which lanner falcon occupancy is represented in the Na…

Distribution, ecology and conservation status of Dionysia involucrata Zaprjag., an endangered endemic of Hissar Mts (Tajikistan, Middle Asia)

2014

<em>Dionysia involucrata</em> Zaprjag. (Primulaceae) is known as critically endangered endemic species of Hissar Mountains in Tajikistan. It is reported from few localities mainly in Varzob River valley and its tributaries. The species inhabits steep or overhanging faces of granite rocks in narrow river gorges. During the research all known populations of <em>D. involucrata</em> were examined in respect of the habitat conditions and species composition of vegetation plots. We analyzed the population extent of the species in its range in Tajikistan and the main threats in order to assess its conservation status. The detrended correspondence analysis was performed on a…

2022

The quality of wintering habitats, such as depth of snow cover, plays a key role in sustaining population dynamics of Arctic lemmings. However, few studies so far investigated habitat use during the Arctic winter. Here, we used a unique long-term time series to test whether lemmings are associated with topographical and vegetational habitat features for their wintering sites. We examined yearly numbers and distribution of 22 769 winter nests of the collared lemming Dicrostonyx groenlandicus (Traill, 1823) from an ongoing long-term research on Traill Island, Northeast Greenland, collected between 1989 and 2019, and correlated this information with data on dominant vegetation types, elevatio…