Differences in the Dynamics of Radial Tree Increment in the Pine Looper Outbreak Area and in Undamaged Stands and Assessment of the Risk of Pests’ Attack

Abstract

The time series of the radial increment of pine Pinus sylvestris L. in 1945–2015 were studied on the territory of the Krasnoturansky pine forest in the stands damaged during the outbreak of the pine looper Bupalus piniarius L. in 1974–1978 and in the stands not damaged by the pest. To assess the differences in the processes of radial increment of trees in damaged and undamaged stands before the outbreak, it is proposed to use the regulatory characteristics of time series, such as the values ​​of n delay (autocorrelation) and the amplitude s of fluctuations in time series. According to these indicators, one can numerically assess the inertia of the processes of regulation of radial increment. Since the regulatory characteristics can only be correctly calculated for stationary time series, the series of the first differences of the radial increment were used for the calculations. The trees in the stands that were attacked by insects were characterized either by the absence of delay in the time series, or by sufficiently large values ​​of the order of autocorrelation (n). Moreover, fluctuations in the current radial increment relative to the age trend were significantly greater in trees in damaged stands than in undamaged ones. The rate of growth recovery in trees damaged by insects depending on the regulatory characteristics of the time series of radial increment before the onset of damage was assessed. The obtained characteristics can be used to assess the risk of phyllophages’ attacks on stands and the rate of restoration of stands damaged by insects.