23 research outputs found
Estudio preliminar de la estructura interna del subtipo fitoclimático VI (IV)1 de Allué (1990). Aplicaciones fitoclimáticas
In this paper we try to establish a preliminary methodology for analyzing vegetation structures included in Allué´s (1990) phytoclimatic subtypes, and their phytoclimatic implications. One of the most geographically extensive subtypes (VI(IV)1) has been chosen, which comprises a considerable number of syntaxa.En este trabajo se pretende establecer una metodología preliminar para analizar en profundidad las estructuras de vegetación que están presentes en los subtipos fitoclimáticos de Allué (1990), así como sus implicaciones fitoclimáticas. Se ha elegido para este estudio uno de los subtipos más extensos territorialmente (VI(IV)1), en el que están representados un número considerable de sintáxones
Can environmental constraints determine random patterns of plant species co-occurrence?
Plant community ecologists use the null model approach to infer assembly processes
from observed patterns of species co-occurrence. In about a third of published
studies, the null hypothesis of random assembly cannot be rejected.
When this occurs, plant ecologists interpret that the observed random pattern
is not environmentally constrained – but probably generated by stochastic processes.
The null model approach (using the C-score and the discrepancy index)
was used to test for random assembly under two simulation algorithms. Logistic
regression, distance-based redundancy analysis, and constrained ordination were
used to test for environmental determinism (species segregation along environmental
gradients or turnover and species aggregation). This article introduces
an environmentally determined community of alpine hydrophytes that presents
itself as randomly assembled. The pathway through which the random pattern
arises in this community is suggested to be as follows: Two simultaneous environmental processes, one leading to species aggregation and the other leading
to species segregation, concurrently generate the observed pattern, which results
to be neither aggregated nor segregated – but random. A simulation study supports
this suggestion. Although apparently simple, the null model approach seems to assume that a single ecological factor prevails or that if several factors
decisively influence the community, then they all exert their influence in the
same direction, generating either aggregation or segregation. As these assumptions are unlikely to hold in most cases and assembly processes cannot be
inferred from random patterns, we would like to propose plant ecologists to
investigate specifically the ecological processes responsible for observed random
patterns, instead of trying to infer processes from patternsThis research and publication was possible
thanks to a postdoctoral fellowship at The
Open University (UK) and the project “Development of the recovery plan for A.
rioxana in la Rioja. Measures of research,
monitoring and control (University of
Salamanca)”, both funded by the Regional
Government of La Rioja (Spain
Classification and ordination of plant communities along an altitudinal gradient on the Presidential Range, New Hampshire, USA
An analysis of vegetation along an altitudinal gradient on the Presidential Range, New Hampshire, USA, using the Braun-Blanquet approach followed by multivariate data analysis is presented. Twelve main plant communities have been distinguished. Floristic information is presented in twelve tables and one appendix. The relationships of the communities to complex environmental gradients are analyzed using Correspondence Analysis. Floristic composition and community structure are controlled primarily by the altitudinal gradient (temperature, precipitation), and by mesotopographic conditions (snow accumulation, exposure and cryoturbation, slope position, and soil moisture)
The supra- and oromediterranean climatophilous perennial herbaceous vegetation (Koelerio-Corynephoretea) in the western Sierra de Gredos, Sistema Central, Spain
A phytosociological study of the supra-oromediterranean climatophilous perennial herbaceous vegetation belonging to Koelerio-Corynephoretea has been carried out in the western Sierra de Gredos. The following subasociations have been described Centaureo ornatae-Stipetum lagascae euphorbietosum oxyphyllae, Arrhenathero baetici-Stipetum giganteae euphorbietosum oxyphyllae, Leucant-hemopsio pallidae-Festucetum elegantis stipetosum giganteae and Thymo zygidis-Plantaginetum radicatae euphorbietosum oxyphyllae. New records of Leucanthemopsio pallidae-Festucetum elegantis typicum and Arenario querioidis-Festucetum summilusitanae have been brought out
Soft-water vegetation (Littorellion) in Spanish mountains
This paper presents a systematic review of Spanish high mountain soft water communities based on 46 phytosociological releves. Using a numerical analysis with ordination (correspondence analysis - CA) and classification (Jaccard index and complete-linkage clustering) three groups corresponding to the phytosociological associations Isoeto lacustris-Sparganietum borderei, Sparganio angustifolii-Isoetetum echinospori and Sparganio angustifolii-Callitrichetum font-queri have been defined. Spanish Littorellion communities are characterized by boreal-alpine and endemic elements. The boreal-alpine elements probably spread via the Pyrenees-Iberian System through to the mountains of the western peninsula during a cold period, thus sharing the habitat with the Ibero-Atlantic flora which was able to adapt to the changing climatic conditions