Livestock disturbances in Mediterranean temporary ponds: A mesocosm experiment with sheep manure and simulated trampling

Abstract

The number and quality of temporary wetlands are declining worldwide and many of the remaining habitats are used as pastures and drinking sites for livestock. Livestock can impact wetlands through a combination of herbivory (defoliation), trampling (physical disturbance), and defecation (nutrient input), but how these influence community structure is still poorly understood. It is nonetheless generally accepted that wetland management can include some grazing, and that properly managed livestock can play a major role in wetland conservation. In Mediterranean temporary ponds, however, it is suggested that grazing might negatively affect macrophyte biodiversity within the pond basin. The impact of livestock on the characteristic freshwater fauna also remains understudied. Using an outdoor mesocosm experiment, we focused on two effects of sheep livestock (trampling and defecation) and their combination, on water quality and on faunal and floral communities from Moroccan temporary ponds. Communities from forested and agricultural sites (pond type) were also compared in a factorial design with treatments. We found that sheep‐simulated trampling and nutrient input decreased hatching invertebrate and plant richness, while lasting effects on water quality and actively colonising communities were limited. Temporary pond communities from forested and agricultural sites differed in species composition and interacted with treatments in their effects on hatching crustaceans and macrophyte species composition. Treatments had a larger effect on the species composition of forest ponds compared to agricultural ponds. These results highlight the complex effects livestock may have on aquatic communities. Water quality, taxonomic groups, and trophic levels responded negatively to trampling and waste treatments and these responses changed with pond type. With worldwide declines of seasonal wetland habitat, the effects of land use (i.e. livestock grazing) on these ecosystems and their biota are important to consider for integrated and sustainable management.

How can Mediterranean temporary ponds benefit from disturbance? Challenges and lessons learned from vegetation management

“…By controlling shrubs and the establishment of more competitive species, livestock grazing promotes light availability for small plant development, enhancing the diversity of typical annual species (Rhazi et al 2001; Ferchichi‐Ben Jamaa et al 2014). A similar impact has been reported after wild boar ( Sus scrofa L.) disturbance in the top layer of ponds' soil (Van den Broeck et al 2019; Caria et al 2021). This observation is in compliance with the intermediate disturbance hypothesis , according to which species richness (and diversity) at the local scale is fomented by intermediate values of disturbance frequency; intermediate times after a disturbance; and intermediate spatial extents of disturbance (Grime 1973; Connell 1978; Willig & Presley 2018).…”

Vernal pool wetlands respond to livestock grazing, exclusion and reintroduction

“…Relatively, little is known about the natural history of this ecosystem prior to the arrival of the Spanish in the 1700s, but it has been suggested that these grasslands were widely grazed by ungulates such as Tule elk and small granivores. Eurasian exotic annual grasses now dominate the uplands, leaving only small patches of native plants (Stromberg et al, 2007). There is growing interest in the use of livestock grazing to promote diversity in these ecosystems, where low to moderate stocking rates generally select against perennials, taller plants and graminoids, and promotes smallstatured forbs (Stahlheber & D'Antonio, 2013).…”

Alternative food sources interfere with removal of a fungal amphibian pathogen by zooplankton

“…Since a zooplankton community shift towards smaller species may have a strong impact on pathogen removal rates, preventing chemical contamination and removal of planktivorous fish are suggested as potential management actions to support biological disease control. Habitat restoration, such as introduction of macrophytes as refuge areas and preventing livestock from entering and disturbing amphibian breeding ponds, may also have an indirect beneficial effect on pathogen removal by creating more favourable environmental conditions for these target micropredators (Burks et al., 2002; Jeppesen et al., 1997; Stansfield et al., 1997; Van den Broeck et al., 2019). Besides top‐down control actions, nutrient loadings and related primary productivity may also steer pathogen removal rates.…”