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