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Abstract: Grazing management is probably one of the most extensive land uses, but its effects on plant communities have in many cases been revealed to be contradictory. Some authors have related these contradictions to the stochastic character of grazing systems. Because of that, it is necessary to implement specific analyses of grazing effects on each community, especially in natural protected areas, in order to provide the best information to managers. We studied the effects of grazing on the species composition of the main vegetation types where it takes place (grasslands, shrublands and pine forests) on the island of La Palma, Canary Islands. We used the point-quadrat intersect method to study the species composition of grazed and ungrazed areas, which also were characterized by their altitude, distance to farms, distance to settlements, year of sampling, herbaceous aboveground biomass and soil organic matter. The variables organic matter, productivity and species richness were not significantly affected by grazing. The species composition of the analyzed plant communities was affected more by variables such as altitude or distance to farms than by extensive grazing that has been traditionally carried out on the island of La Palma involving certain practices such as continuous monitoring of animals by goat keepers, medium stocking rates adjusted to the availability of natural pastures, supplementation during the dry season using local forage shrubs or mown pastures and rotating animals within grazing areas Although some studies have shown a negative effect of grazing on endangered plant species, these results cannot be freely extrapolated to the traditional grazing systems that exert a low pressure on plant communities (as has been found in this study). We consider extensive grazing as a viable way of ensuring sustainable management of the studied ecosystems. [Copyright &y& Elsevier]

The effect of herbivores on species richness is important for the conservation of protected areas under grazing management but research findings on this are far from consistent. The main objective of this study is to analyze how the cessation of grazing by goats affects the diversity parameters at different scales over a 5-year period. The study was conducted in the Teno Rural Park in the northwest corner of Tenerife, Canary Islands. The studied areas have been grazed by livestock since the beginning of the 16th century and currently are used by local farmers, mainly for extensive goat production. In these areas we selected four blocks and in each block four 100 m plots were established, two excluded from grazing (located in 12 × 12 m exclosures) and two control plots. The analyses showed an accumulation of species in the control plots significantly higher than in exclosure plots at small scales. Power function parameters such as c and z only showed differences in function for the sampling year and not for the treatment. Although the results showed an increase in species richness due to grazing, this is very small. However, negative effects in native species richness are not detected, so we suggest the promotion of goat grazing as a way to maintain land use, cultural values, and species richness in these pastures. [ABSTRACT FROM AUTHOR]

Extensive goat production systems have played an important role in the structure and specific composition of Tenerife's pastures. Due to the steady decline of grazing goats in the Island, the study of the impact of removal of goat grazing on plant communities is of primary importance, in order to delineate a proper conservation strategy for these ecosystems. We analysed changes in floristic composition, species richness, diversity and soil chemical properties of this plant community during 4 years of removal of goat grazing. No changes in species richness or diversity were detected during the study period, but a species turnover was noted in response to absence of goat grazing, related to soil magnesium content. Although this study showed little changes in Tenerife's pastures after 4 years of removal of goat grazing, changes on this community are expected due to soil chemical properties modification in response to absence of goat grazing. It is suggested that a longer period of exclusion will be necessary to detect changes in plant species composition, and additional studies are necessary to develop a suitable pasture management strategy in order to maintain the stability of these ecosystems. [Copyright &y& Elsevier]