Long-term population dynamics of the black grouse Lyrurus tetrix in the steppe zone of Orenburg region under the influence of fires (on the example of Burtinskaya steppe, Orenburg reserve)

A significant negative correlation between the size of the burnt area and the number of the Black Grouse Lyrurus tetrix was found in Orenburg State Nature Reserve on the basis of a long-term observation. The paper provides the data on the long-term population dynamics of the Lyrurus tetrix in Burtinskaya Steppe, a part of Orenburg Nature Reserve. It was shown that the population of the Black Grouse is affected by both the increasing number of grassland fires and the enlarged burnt area size over the past decades. According to a recent study (Pavleichik 2015) the impact of the pyrogenic factor on the abundance of grouse subspecies Lyrurus tetrix viridanus Lorenz was assessed. This subspecies, 1891 (Potapov, 1987) has occurred in this specially protected territory for a long time. Burtinskaya Steppe (4500 hectares) is located in the Orenburg region (N51 ° 13.727 'E056 ° 39.990') in the southeast of the European Russia and is a part of Orenburg State Natural Reserve, founded in 1989. It lies in the subzone of herb-fescue-feather grass steppe dominated by Zaleski feather grass (Stīpa zalēsskii). This steppe area has a complex structure: u-shaped valleys and small, isolated woodlands with the maximum size of 11.5 ha. During the analyzed period 1991-2015, 8 fires breached the perimeter of this territory from outside resulting in decreasing the annual average and maximum numbers of the Black Grouse. The negative correlation between the predicted values of the regression for the parameters Burned Area and Average Number per Year was found high (r = –0.7264, P = 0.002). The correlation coefficient found between the predicted values of the regression for the parameters Burned Area and Maximum Flock Size per Year was –0.589 (r = –0.5899, P = 0.002), indicating moderate inverse relationship. It is assumed that cycles of reduced numbers followed by the extensive fires was a grouse response to a temporary deterioration of feeding conditions and destruction of nesting habitats under the impact of pyrogenic factor.