Horse grazing systems: understory biomass and plant biodiversity of a Pinus radiata stand

Abstract

Horse grazing systems may affect productivity and biodiversity of understory developed under Pinus radiata D. Don silvopastoral systems, while acting as a tool to reduce the risk of fire. This study compared continuous and rotational grazing systems effect upon biomass, fractions of stem, sprouts, leaves and woody parts of Ulex europaeus L. and alpha (Species Richness, Shannon-Wiener) and beta (Jaccard and Magurran) biodiversity for a period of four years in a P. radiata silvopastoral system. The experiment consisted of a randomized block design of two treatments (continuous and rotational grazing). Biomass, and species abundances were measured -biodiversity metrics were calculated based on these results for a two years of grazing and two years of post-grazing periods. Both continuous and rotational grazing systems were useful tools for reducing biomass and, therefore, fire risk. The rotational grazing system caused damage to the U. europaeus shrub, limiting its recovery once grazing was stopped. However, the more intensive grazing of U. europaeus plants under rotational had a positive effect on both alpha and beta biodiversity indexes due to the low capacity of food selection in the whole plot rather than continuous grazing systems. Biomass was not affected by the grazing system; however the rotational grazing system is more appropriate to reduce U. europaeus biomass and therefore forest fire risk at a long term and to enhance pasture biodiversity than the continuous grazing system.

The Role of Feral Goats in Maintaining Firebreaks by Using Attractants

“…In this work, the differences in the biomass of herbaceous plants within the fenced plots compared with the biomass of those outside them were particularly notable, indicating that grazing decreases their biomass, especially in areas near water and salt supply points. Similar results have been obtained with equine cattle in Galicia (Spain), where it was evident that the continuous and rotational management of the grazing system modifies the productivity of herbaceous plants and the evolution of understory biodiversity [44]. This has also been observed with sheep in Andalusia (Spain), where a decrease in biomass of between 53% and 72% was observed [45].…”

Horses and rangelands: perspectives in Europe based on a French case study

“…Conversely, trampling by horses has been shown to limit the development of Vaccinium myrtillus in the upland area of central France (Loiseau and Martin‐Rosset, ). Efficient reduction of the aerial biomass of gorse was also recorded in Galician Pinus radiata woodlands (Mosquera‐Losada et al ., ; Riguero‐Rodriguez et al ., ), decreasing the fire risk. The impact of horses on the development of woody plants requires further studies to analyse the influence of animal and plant characteristics and grazing management (e.g.…”

Impacts of horse grazing on botanical composition and diversity in different types of heathland

“…C. filipendulum, G. pneumonanthe, S. tinctoria and S. humilis) increased in abundance or frequency under horse grazing in our experiment. Also in Galicia, plant species richness and diversity increased under horse grazing in the gorse-dominated understorey of pine stands, and increases were greater with rotational than with continuous grazing (Rigueiro-Rodríguez et al 2012). Other studies have also found positive effects of horse grazing on floristic diversity in different plant communities like coastal and wet grasslands in France (Loucougaray et al 2004;Marion et al 2010).…”

“…The number of horses has increased in the Cantabrian Mountains due to their easier management and lower care needs and feeding costs compared with other herbivore species. Horses are known to reject heather (Gordon 1989;Ferreira et al 2013) but show a good ability to graze gorse (Putman et al 1987;Rigueiro-Rodríguez et al 2012), so they have a potential as management tool to reduce woody phytomass accumulation in heathlands. However, little is known about the environmental and productive consequences of horse grazing in heathlands.…”