DIAGNOSTICS OF SPECIES VIABILITY ON CONIFEROUS PLANTATIONS BASED ON BIOELECTRIC INDICATORS

Abstract

Introduction. Electric signals propagation in plants on the cellular level is thoroughly studied and described in detail in a number of research papers. However, the formation of bioelectric indicators of woody plants in the natural environment is understudied. The research is aimed at the detection of information capacity of bioelectric parameters for instant diagnostics of viability of coniferous species under continuous climate and anthropogenic impact. The research is focused on the plantations of Scots pine, Siberian larch and Norway spruce growing in the Middle Volga Region. Bioelectric potentials were measured using high-impedance millivoltmeter of direct current with platinum electrodes (Extra-999). Bioelectric potentials were referenced at root collar and at the height of 1.3m. Impedance of pre-cambial plant tissues  was measured using C 4314 apparatus with 500 frequency  using the sensing system of timber humidity electronic indicator EV-2K. The distance between the electrodes was 20.0 mm, the length of electrode active part was 10.0 mm, the diameter was 1.0 mm. All the measurements were carried out in the mid vegetation period from the north (shady) side at the height of 1.3 m. Results. Fast growing local coniferous species have high values of bioelectric potential (150-200 mV), while the slowly growing introductions (Mountain pine), the same values are below 50mV. Under significant anthropogenic disturbance the bioelectric parameters are between 60-70 mV. The dominant trees have higher bioelectric parameters and lower impedance parameters  of pre-cambial plant tissue as compared to the weakened ones. There is direct and reverse interlinking between the humidity of plant tissue and pre-cambial plant tissue impedance (r = -0.85…-0.90). The trees of 1st and 2nd class of Kraft's  biological classification, forming the dominating canopy feature pre-cambial plant tissue impedance values between 20 and 40 kW. The trees of 4^th and 5th class of Kraft's  biological classification feature impedance values above 40kW. Under anthropogenic disturbance occurred in urban plantations the bioelectric values are going down, the total chlorophyll is decreasing and the catalase activity in needles is weakened. In weakened treed the osmotic potential and pre-cambial plant tissue impedance values are growing. The bioelectric parameters for Siberian larch planted along the main roads with anthropogenic disturbance is 108 mV, while the same indicator for the greenbelt is 144 mV. Conclusion. The trees with good viability characteristics demonstrate high bioelectric parameters of 150-200 mV. Weakened trees feature far lower values. Water regime abnormalities that result in plant weakening can be diagnosed by variations of pre-cambial plant tissue impedance values. Under deterioration of species viability the impedance value is increased by 2-3 times. Any changes in bioelectric parameters tell about deterioration of species viability on the initial weakening stages. Bioelectric potential and pre-cambial plant tissue impedance values should be used for early instant diagnostics of species viability under climate and anthropogenic impact.