Effects of air pollution on the condition of sessile oak forests in Hungary

Publisher Summary Industrial air pollution may alter—directly and indirectly—the healthy state of forests. Besides inducing serious direct damages in the tree foliage, they also result in the deterioration of many soil processes and thereby influence the conditions of plant mineral nutrition. Air pollution can cause soil acidification and, in this way, affect the availability of nutrients and microbiological activity. This may lead to a reduction in the rates of biochemical processes and a considerable decrease in the overall biological activity of the soil environment. During the past several years, an accelerated deterioration of natural forests has also been observed in Hungary, which has affected mainly the natural stands of sessile oak ( Quercus petraea ) on the mountainous and hilly regions. This chapter presents the results of investigations aimed at revealing the alteration of the condition of sessile oak stands as a consequence of immission loads. The chapter investigates three different aspects of oak forest degradation: (1) the soil compartment and its main chemical properties and microbial activity, (2) the responses of underground vegetation layers with respect to the species composition and the leaf nitrate activity (NRA) of some dominant shrub species, and (3) the physiological state of healthy and declining trees of Quercus petraea in forest stands with different immission loads.