Pine Stands as Bioindicators: Justification for Air Toxicity Monitoring in an Industrial Metropolis

Five permanent sample plots (SPs; 200–250 trees per plot) were established in middle-aged high-grade suburban pine stands near the industrial city of Krasnoyarsk, Siberia, Russia. Needle damage, inventory parameters of the stands, and the defense response of the stem phloem were evaluated annually for the years 2002–2019 and attributed to acute or chronic toxic exposures (creeping fire or industrial pollutants, respectively). The results form a basis for using trees as bioindicators. A newly elaborated stem lesion test was formed from a hypothesis on the upward sugar transport for the regeneration of an injured crown, based on Eschrich’s model of bidirectional sugar transport in the phloem. The formation of a phloem lesion was induced by inoculation of the stem with a mycelial extract of the ophiostomatoid fungus Ceratocystis laricicola. The lesion length and its shift relative to the inoculation hole were measured. An increase in the length of needles at early stages of stand weakening by pollutants was found to correspond to the hormesis model (Selye’s adaptation syndrome). A possibility of assessing the chronology of pollutant toxicity and the duration of the recovery period after creeping fire was shown.