Vegetation Cover Management and Landscape Plant Species Composition Influence the Chrysopidae Community in the Olive Agroecosystem.

Habitat manipulation through the promotion of semi-natural habitats such as cover and patch vegetation is a possible means of offsetting the negative impacts of the agricultural practices. A baseline situation is crucial before any successful habitat manipulation is attempted. We studied the effects that current vegetation cover management practices have on plant composition and the potential attraction that the plant families from the semi-natural habitats could have on the Chrysopidae community, a key pest control agent, in five olive farms in Granada (Spain). Vegetation cover was assessed using a point quadrat methodology in eight transects per farm. In addition, the patch vegetation was characterized with 60 transects using a line intercept methodology. The woody patch vegetation and olive tree canopies were vacuumed using a field aspirator to collect adult Chrysopidae. In the cover vegetation we observed great variability in both the richness and diversity of plant communities caused by the vegetation cover management techniques and the transect position (in the middle of the rows or beneath the tree canopy). The plant families with the greatest plant cover were the Asteraceae and Fabaceae, where Asteraceae was favoured by tillage and Fabaceae by grazing, while in the patch vegetation, the predominant families were the Rosaceae and Fagaceae. Our results indicate that the genus Chrysoperla was mostly correlated with the Plantaginaceae, Brassicaceae and Asteraceae plant families in the cover vegetation, and with the Caryophyllaceae and Rosaceae families in the patch vegetation. The genera Apertochrysa and Pseudomallada were associated with the families Malvaceae and Poaceae in the cover vegetation, and with the families Cupressaceae, Poaceae and Pinaceae in the patch vegetation. Our study shows to the farmers the possibilities of vegetation cover management to select plant families for the cover vegetation.

Phytosociological analysis of the mesophilic forest of the San Pedro volcano (Guatemala).

From a standpoint of phytosociological research, little is known about the phytocoenosis found on the volcanoes of Central America. This paper analyses the distribution of the vegetation on the volcano of San Pedro in terms of its species-richness, composition, structure and abundance, and the possible relationships between these components and the changes in elevation and orientation that occur there. We divided the study area into three altitudinal belts between 2,400 and 3,020 m a.s.l. where carried out 36 inventories, each one in an area of 0.1 ha. We then applied multivariate analysis to classify and order the data in the matrix obtained from the frequency of the sampled plants. Our results lead us to propose two mixed cloud-forest associations within the class Alnetea acuminatae. The first, Saurauio oreophilae-Alnetum acuminatae ass. nova, is found on the more humid western side, while the second, Adianto andicolae-Quercetum peduncularis ass. nova, appears in sunnier and less shady sites, mainly on the east face. As part of this latter association, we also identified the new subassociation festucetosum amplissimae subass. nova. These syntaxa are part of the alliance Oreopanacion xalapensis all. nova, which we have created to embrace the mesophytic montane forests dominated by broad-leaved species.

A study of the dry forest communities in the Dominican Republic.

This paper is a floristic and phytosociological study of the dry forest communities of the Dominican Republic. A total of 69 relevés in dry forest biotopes were carried out. The samples were subsequently subjected to Detrended Correspondence Analysis for the determination and study of possible groupings. The study does not cover tree formations growing on serpentines, nor the so-called semideciduous forests, peculiar to areas with higher rainfall. A total of nine phytocoenoses were identified. The most significant results led to the description of six new phytosociological associations: Simaroubetum berteroani (thorny dry forest on coastal dunes), Phyllostylo rhamnoidis-Prosopidetum juliflorae (southern Dominican disturbed dry forest), Consoleo moniliformis-Camerarietum linearifoliae (dry forest on hard limestones), Lemaireocereo hystricis-Prosopidetum juliflorae (northern Dominican disturbed dry forest), Lycio americani-Prosopidetum juliflorae (disturbed dry forest on saline soils) and Guettardo ellipticae-Guapiretum discoloris (dry forest on flat-topped hillocks in Montecristi). This is an important step forward in the phytosociological and floristic studies of the Caribbean territories.