A Christmas Tree

The goal, stated in the last sentence, for this research from Croatia - conducted from 1991 to 1995 - makes the charmingly naive assumption that the problem it investigates can be ameliorated.  I have left the translation errors intact:

The Forest dieback in Croatia, the Research on the Causes and Afforestation Procedures

"Forest dieback is a global issue concerning the forests immediately impacted by techical civilization. The research is based on the knowledge, that the forest dieback is the result of industrial, urban, traffic and agricultural pollution, partly though, ty the technologies badly adapted to forest ecosystems. The micro-habitat methods helped to assess great changes in the forest soils, dry and moist sulphate deposits, nitrates and other poisons being present in Croatian forests for a considerable time now. Though different tree species react differently, sooner or later all will be destroyed through the alterations of the physiological processes in them. The results of this research should alleviate the disastrous consequences."

Anyone who reads Wit's End, and knows that I am always searching for a scientist who will state openly that ozone is killing trees, will understand why I consider the following link, which I found this morning, as a very special gift from Santa.  The entire thing is a fascinating read, but all you really need to know is excerpted below.

Happy Holidays to all, and thank you for reading, and I hope you enjoy the song.

Air Pollution Increases Forest Susceptibility to Wildfires:

A Case Study in the San Bernardino Mountains in Southern California

Abstract

Many factors increase susceptibility of forests to wildfire. Among them are increases in human population, changes in land use, fire suppression, and frequent droughts. These and other factors have been exacerbating forest susceptibility to wildfires over the past century in southern California. We report on the significant role that air pollution has had on increasing forest susceptibility to wildfires, based on a 1999–2003 case study in the San Bernardino Mountains.

Air pollution, specifically ozone (O3) and wet and dry deposition of nitrogenous (N) compounds as a by-product of fossil fuel combustion, has significantly increased since urbanization and industrialization of the region after 1945. Ozone and elevated N deposition cause specific changes in forest tree carbon (C), N, and water balance that enhance individual tree susceptibility to drought, bark beetle attack, and disease, and when combined, contribute to whole ecosystem susceptibility to wildfire.

For example, elevated O3 and N deposition increase leaf turnover rates, leaf and branch litter, and decrease decomposability of litter, creating excessively deep litter layers in mixed-conifer forests affected by air pollutants. Elevated O3 and N deposition decrease the proportion of whole tree biomass in foliage and roots, thereby increasing tree susceptibility to drought and beetle attack. Because both foliar and root mass are compromised, carbohydrates are stored in the bole over winter. Elevated O3 increases drought stress by significantly reducing plant control of water loss. The resulting increase in canopy transpiration, combined with O3 and N deposition-induced decreases in root mass, significantly increases tree susceptibility to drought stress, likely contributing to successful host colonization and population increases of barkbeetles. Phenomenological and experimental evidence is presented to support the role of these factors contributing to an increase in the susceptibility of forests to wildfire in southern California.

Despite the level of attention given to the causative factors for increased wildfire activity (Westerling et al., 2006), a largely ignored contributing factor is air pollution. Chronic nitrogen (N) deposition

contributes to increased forest densification by stimulating aboveground biomass production and enhances litter accumulation through increased needle production, turnover rates, and depressed long-term decomposition rates (Fog, 1988). Elevated ozone (O3) exposure increases tree susceptibility to drought stress through direct effects on loss of stomatal control with subsequent increased canopy transpiration, and increased successful bark beetle colonization through both increased tree drought

stress and pollutant-induced redistribution of carbohydrates to the bole. The effects of these air pollutants, combined with the human and ecological changes in the fire-adapted ecosystem, have increased forest stand susceptibility to wildfire in southern California (Fig. 17.1).