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Abstract
The resistance of woody plants to phytophage damage consists of a universal system of mechanisms: 1) repellent chemicals, 2) defensive reactions both mechanical and chemical, 3) retention of viability under disturbed metabolism and low biomass accumulation, and 4) recuperative capacity. Siberian coniferous tree species, with the exception of
Larix, are less resistant to phytophage damage than deciduous ones. Evergreen conifers evolved toward constitutive antibiosis by improving their chemical mechanisms of defense, i.e. terpenoid repellents and toxins. In deciduous species, there was evolution of defenses in the direction of an increase in tolerance and recovery (especially after damage or loss of assimilation organs). The universality of the protective mechanisms of woody plants is manifested in the nonspecificity and the relative uniformity of their responses to the different agents of injury (biotic, chemical, or mechanical). We have tried to correlate the main stages of tree decline with tree metabolic and resistance changes (Fig. 1). The number of eliciting damage sources could be extended to include drought or disturbances in soil conditions, but the five categories of tree conditions shown in Fig. 1 were determined to be adequately representative of the processes involved.
Parent Publication
Citation
Rozhkov, Alexandr S.; Massel, Galina I. 1991. Conifer defenses and xylophagous insects. In: Baranchikov, Yuri N.; Mattson, William J.; Hain, Fred P.; Payne, Thomas L., eds. Forest Insect Guilds: Patterns of Interaction with Host Trees; 1989 August 13-17; Abakan, Siberia, U.S.S.R. Gen. Tech. Rep. NE-153. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 391-392.
