Effects of seasonal grazing and annual mowing on floristic composition and plant diversity in the Saral rangeland, Kurdistan, Iran

Abstract

This study examined the impact of long-term (40 years) seasonal grazing and annual scythe mowing on changes in plant diversity, floristic composition and plant functional groups in the cold semi-arid rangelands of Mangahul-Zardawan located in Saral, Kurdistan. In this investigation, 900 plots (2 m2) were sampled in grazed (450 plots) and mowed sites (450 plots) to measure vegetation and plant characteristics. Data were collected in two consecutive growing seasons from late May to early June in 2017 and 2018. Both years recorded below average rainfall. The results showed that after 40 years, seasonal grazing compared to scythe mowing increased canopy cover and species richness of different functional groups including annuals, perennial grasses, perennial forbs and total vegetation. On the other hand, both the total above-ground plant material and the palatability index were higher for the mowed than the grazed sites, although scythe mowing had caused the Boraginaceae family to disappear. Based on these results, the mean of total plant material (above-ground live + standing dead + litter) was substantially higher in the mowed area, where two-year mean totals were 271 g/m2 compared with 216 g/m2 for the grazed area. In terms of a three-level palatability classification (high, medium and low), only the plants with moderate palatability differed in contribution between the sites, with mowed sites having a significantly greater proportion of this class than the grazed sites. Our results suggested that in the long term, grazing can maintain species richness and the typical floristic composition of rangelands; but when socio-economic issues have priority, mowing has more advantages. In rangelands with the same ecological and geographic conditions, users and managers can choose the most appropriate management approach based on their long- and short-term policies.