The role of silicon in detecting and explaining forest decline : Air Pollution and Forest Decline. 14th International Meeting for Specialists in Air Pollution Effects on Forest Ecosystems

1989

10 Abb., 2 Tab., 19 Lit. Ang., En, Zfsg. En

Unselbständiges Werk

9091

200034653

The results of a state-wide survey of 156 stands of Norway spruce (Picea abies Karst) are reported. The silicon content of needle tisue in regard to environmental conditions and the vitality of trees received special attention. The concentration of silicon was correlated with -needle age - climate, esp. rainfall, temperature, and aridity index -the contents of F, Cl, S, N, and heavy metals in needles which indicate air pollution -pHvalue of mineral soil close to the trees -needle retention and damage clases of Norway spruce. The "silicon hypothesis" was formulated in order to interpret both statistical analyses and microanalyses of needles and to allow systematic investigations of this subject. The Si-content of needles is regarded as a function of transpiration and the concentration of soluble Si in soil solution. Therefore an increased exposusre of trees, disturbance of stomata regulation or soil acidification would increase the Si-content of needles. The relations between Si and the degree of needle losses lead to the question whether this might also mean some causal connections by affecting water supply or translocation of nutrients and assimilates. The microanalysis of needles supports this suspicion. The 'silicon hypothesis' could therefore combine several different explanations of forest decline which all lead to increased Si-contents.