Autumn and spring drought periods affect vegetation on high elevation rangelands of Turkey

The amount and temporal distribution of precipitation received is of critic al importance for regrowth and plant production on rangelands. The effects of drought in the autumn, and spring/summer, as they affected sheep fescue (Festucaa ovina L.) dominated vegetation in Eastern Anatolia, Turkey, were examined between 1996 and 1998. Artificial drought was created using polyet hylene rain-out shelters. The experiment was a randomized complete block de sign with 3 replications with a split-plot arrangement of treatments. Main plots included 2 autumn treatments: imposed artificial autumn-drought or a 40 mm of additional water plus rain. Sub-plots contained 4 treatments: arti ficial drought in May, June, July, or full spring rainfall. The number of r eproductive shoots, aboveground biomass production, protein content, protei n yield, canopy coverage and botanical composition were determined. Reprodu ctive shoot numbers were reduced from 617 to 31 m(-2) when plants entered w inter without autumn regrowth as a result of autumn-drought. Plots subjecte d to drought in the autumn had aboveground biomass of 424 kg ha(-1). Protei n content of forage, crude protein yield and water use efficiency (WUE) wer e 11.6%, 49 kg ha(-1) and 1.5, respectively. These were compared with 1,038 kg ha(-1), 9.6%, 99 kg ha(-1), and 2.4, respectively, for plots received n ormal autumn precipitation in addition to 40 mm of additional water. Aboveg round biomass production increased as short-term drought in spring was dela yed but WUE was decreased. Autumn-drought had no effect on the proportion o f grasses, but reduced legumes and resulted in an increase in other species . Spring/summer-drought had no effect on legumes but, as the onset of droug ht was delayed, grasses decreased and other species increased in compositio n. Autumn-drought reduced canopy coverage from 34.7% to 23.8% but spring dr ought had a negligible effect. Results indicated that autumn precipitation was crucial for productivity of these high elevation rangelands.