No abstract

Many fed beech trees died in parts of !he Maruia Valley between 1978 and 1980 followtng an outbreak of the scale insect Inglisia fagi. Annual diameter increment of trees and climatic data suggest the primary cause to be a series of spring droughts between 1974 and 1978. In the worst affected stands of mixed red and silver beech a large proportion of the red beech trees died. Release from competition was reflected in the greatly increased growth rate of the residual silver beech which generally was not heavily attacked by the scale insect; early response of surviving red beech was limited because of reduced foliage.

Forest dieback in the Kaweka Range appears to be a stage in the natural process of replacement for mountain beech. An examination of stand structure in stable, transitional, and unstable forest showed dieback and tree mortality to be associated with mature and over mature stands. Recruitment peaks suggest periodic natural disturbance, such as severe drought, initiates tree decline. Insects and disease, although contributing to the rate of decline, were shown to be symptoms rather than causes.

No abstract

An investigation into the decline of hard beech on the Mamaku Plateau showed tree death to be due to a loss of new foliage over successive seasons. Severely affected trees shed more than 30% of newly flushed foliage as a result of attack by the leaf-mining weevil Neomycta pulicaris with further losses from attack by the tineid moth Heliostibes vibratrix. Growth and climatic data suggest decline was initiated by drought, with worst affected stands on sites with lowest soil moisture retention capability.