Global warming allows trees to grow faster, but reduces the strength of new wood.
As the planet warms, the growing season lengthens - and in some regions, plants have received a whole extra week a year when they can continue to grow normally. However, high temperatures and anthropogenic pollution neutralize this effect: the resulting tissues turn out to be fragile, making trees brittle and reducing the quality of the extracted wood. These are the conclusions reached by Hans Pretzsch and his colleagues from the Technical University of Munich, whose article is published in the journal Forest Ecology and Management.
Indeed, in one of his previous studies, Hans Pretzsch found that, amid notable increases in average temperatures, the growth rate of spruce and beech in Central Europe has grown by an impressive 77 percent per year over the past century. That would be good: increased productivity of trees means more carbon dioxide associated with the atmosphere and more resources available for human use. Unfortunately, Pretzsch's new work shows that this is not the case.
The authors of the study relied on monitoring data from 41 forest sites in southern Germany, some of which have been collected since 1870. They also collected and analyzed wood samples from local spruces (Picea abies), oaks (Quercus petraea), beeches (Fagus sylvatica) and pines (Pinus sylvestris). For all four species, it was found that wood density had dropped by 8-12 percent compared to 1870. Part of this effect is due to the accelerated growth itself. However, to a greater extent, it can be caused by the action of nitrogen-containing pollutants entering the air with the exhaust of cars, and into water and soil in the form of agricultural fertilizers.
According to scientists, the specific carbon content in such weakened wood is half what it was at the end of the 19th century, which reduces the efficiency of fixing atmospheric carbon dioxide. Nevertheless, the authors consider the process as a whole positive: albeit in a weakened form, but trees grow more actively, and forests begin to spread faster, which can at least slightly weaken the negative impact on the human biosphere.
Sergey Vasiliev
