Nitrogen Depletion and Redistribution by Free‐Ranging Cattle in the Restoration Process of Mosaic Landscapes: The Role of Foraging Strategy and Habitat Proportion

Abstract

In a mosaic landscape in N-Belgium (W-Europe), consisting of forest, grassland, and wooded pasture on former agricultural land, we assessed nitrogen redistribution by free-ranging cattle (±0.2 animal units ha −1 yr −1 ). We examined if the spatial redistribution of nitrogen among habitats by cattle could restore nutrient-poor conditions in preferred foraging habitats, and conversely whether such translocation could lead to extreme eutrophication in preferred resting habitats. We used nitrogen content of different diet classes, habitat use, foraging and defecation behavior, weight gain, and nitrogen losses in the actual situation to explore four different habitat proportion scenarios and two different foraging strategies to calculate a net nitrogen balance per habitat. An atmospheric deposition of 30 kg N ha −1 yr −1 with varying interception factors according to the habitat types was included in an integrated nitrogen balance. All scenarios showed a net nitrogen transport from grassland and wooded pasture to forest habitat. We found that nitrogen redistribution strongly depends on habitat proportion. Nitrogen losses from preferred grassland habitat can be high, given its proportion is small. Depletion is only to be expected at excretion-free areas and probably is of minor importance to trigger the establishment of woody species. In general, nitrogen transported by cattle was much lower than input by atmospheric deposition, but grazing can compensate for high N inputs in excretion-free areas and maintain grassland types that support critical loads of 20-25 kg N ha −1 yr −1 . In none of the scenarios, N transport by cattle resulted in the exceeding of critical nitrogen loads to vulnerable forest ground vegetation.

Nutrient availability controls the impact of mammalian herbivores on soil carbon and nitrogen pools in grasslands

“…In contrast, C and N may be retained under herbivory (arrow 7) through greater plant root allocation (Derner, Boutton, & Briske, ; Pineiro et al, ; Reeder, Schuman, Morgan, & Lecain, ) and higher soil microbial activity (Lange et al, ). Herbivores can locally remove or add C and N (arrow 10), by feeding on plant biomass in one area, while depositing dung and/or urine in another (Giese et al, ; Singer & Schoenecker, ; Van Uytvanck, Milotic, & Hoffmann, )…”

Does cattle movement between forest pastures and fertilized grasslands affect the bryophyte and vascular plant communities in vulnerable forest pasture biotopes?

“…Our results give evidence of nutrient accumulation in the forest pastures connected to grasslands, but more extensive studies that would also include N-levels and the soil chemistry of the unconnected forest pastures are needed to reveal the details of the nutrient transfer. Indeed, it is quite possible that nutrient accumulation in a forest pasture can depend on the proportional areas of grasslands and forest pastures in an enclosure (Uytvanck et al, 2010). We documented large variations in nutrient levels and in nutrient accumulation between the sites (Appendix B) and this may be explained by differences in the forest pasture/grasslandratios in the enclosures (Appendix B).…”

“…It is worth noting that in practice, farmers adjust grazing intensity and grazing periods in accordance with seasonal weather conditions, prevailing herd sizes on their property and on other practical considerations rather than on official guidelines. The patterns of nutrient accumulation and grazing intensity in forest pastures also depend on the proportional areas of grassland and forest pastures in an enclosure and on the daily movements of cattle (Uytvanck et al, 2010). The nutrient enrichment and subsequent eutrophication can be especially high if cattle use the forest pastures as resting sites and feed mainly on the grasslands (Pykälä, 2001;Uytvanck et al, 2010).…”

“…If the stocking rate in an enclosure that comprises both forest pastures and fertilized grassland pastures is determined by the productivity of the grassland, then there is a risk that the grazing intensity will be too high and potential eutrophication in the forest pasture is likely, as the free-roaming cattle will transfer nutrients in the urine and manure from the highly-productive fertilized grasslands to lowproductive unfertilized forest pastures (Pykälä, 2001;Uytvanck et al, 2010). It is worth noting that in practice, farmers adjust grazing intensity and grazing periods in accordance with seasonal weather conditions, prevailing herd sizes on their property and on other practical considerations rather than on official guidelines.…”

Monitoring van ecologische processen Vlaanderen: Een verkenning

“…Hierdoor wordt het terreingebruik en het daarmee samenhangend graaspatroon sterk beïnvloed. Ook op landschapsniveau zorgt gedifferentieerd graas-en defaecatiegedrag in relocalisatie van nutriënten (Van Uytvanck et al 2010) en transport van diasporen via epi-of endozoöchorie (Couvreur & Cosyns 2004). …”