Attractiveness of salt placement to cattle in the Mediterranean mountain areas

Socio-economic changes occurred after World War II have resulted in a dramatic agro-pastoral abandonment with an extended shrub and tree encroachment of Italian mountain grasslands. This phenomenon has affected either the temperate and Mediterranean mountains, where invasion is the first step of the ecological succession towards the potential forest vegetation (Bagella et al. 2017). Biodiversity loss (Bagella et al., 2016; Orlandi et al., 2016), increase of wild-fires, erosion and avalanches over large areas (Pittarello et al. 2016) are the main effects of changing vegetation. As a consequence, the conservation and restoration of semi-natural grasslands have become important agri-environmental issues. Recent research show the benefits of the strategic placement of mineral mix supplements (MMS) to lure cattle into traditionally undergrazed areas and restore sub-alpine shrub-encroached grasslands (Probo et al. 2014; Pittarello et al., 2016). Due to the combined effects of grazing, trampling, seed transportation, and nutrient redistribution by cattle, these practices were effective in temperate grasslands in reducing woody species cover and in increasing the cover of herbaceous species characterized by good forage quality, while enhancing the diversity of plants and some insect taxa at the same time. The present work, which is part of in progress project iGral1, has the ultimate goal of defining innovative options for the development of sustainable sylvo-pastoral systems. Here we report the first results on the strategic use of MMS in a sylvo-pastoral rangeland at Mediterranean mountains in Sardinia. The study was conducted in the experimental farm of the Agricultural Research Agency of Sardinia (AGRIS Sardegna), located in municipality of Macomer (Nuoro, 600-700 m asl; lat.40°233N, long. 8°702E ), as representative of sylvo-pastoral areas in Mediterranean mountains. The area is encroached mainly by downy oaks (Quercus pubescens Willd.) and shrubs of Pruno-Rubion and Cytisetea scopario-striati (Ruiu et al., 2017). Secondary grasslands are represented by communities referable to the classes Poetea bulbosae (habitat 6220*), Molinio-Arrhenatheretea and Stellarietea mediae (Bacchetta et al., 2007). The study area consisted of a pasture (40 ha) managed under a continuous stocking system and grazed by a herd of 12 mature Sarda suckler cows with their calves (16.7 AU - Allen et al., 2011), at a stocking rate of 208 kg live weight/ha. Nine MMS were supplied in 5-kg blocks (fosfatic salt blocks), which were placed on metal poles arranged along a line of 250 meters, in traditionally undergrazed and shrub-encroached locations. The linear arrangement of poles rather than a clustered one was used to help cows spread across these underutilized areas and find all the MMS sites (Pittarello et al., 2016). A paired control site without any supplement (C) with similar vegetation and topographic conditions was identified for each MMS site at a distance of 104±53 m (mean ± SD). Three randomly selected cows were tracked with Global Positioning System (GPS) collars during period 15- 25/07/2019. Knight GPS tracking collars, based on igotU Gt - 600 GPS units equipped with a large size rechargeable battery pack were used (Knight et al. 2018). The manufacturer reports an average accuracy of acquisitions within 10 m. Positions were recorded every 3 min. MMS and C locations were recorded with a hand-held GPS (Garmin Oregon ® 650t, Maps Trekmap ® Italia v4 pro). The use of sites by cattle was expressed as the time spent within a 50-m buffer area around MMS and corresponding C poles and it was calculated by counting the GPS fixes within each buffer area. Each fix was representative of a 3-minutes period. Then, differences in the time spent at MMS and C poles