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Research article - Peer-reviewed, 2004

Comparison of methods for estimation of needle losses in Scots pine following defoliation by Bupalus piniaria

Langstrom B, Hellqvist L, Cedervind J

Abstract

In 1996, ca. 7000 hectares of pine forests at Hokensas in SW Sweden were defoliated by the pine looper, Bupalus piniara (L.) (Lepidoptera. Geometridae). Following an aerial damage survey using CIR (colour infra red) photography, and estimation of pupal densities in the soil, ca 4000 ha of the most defoliated pine stands were sprayed in early August 1997 with Bacillus thuringiensis var. kurstaki. The control operation was succeessful but probably redundant, as no further defoliation occur-red in unsprayed reference areas. In order to assess defoliation levels in different damage classes for later growth loss studies, 47 circular study plots were laid out in pine stands representing different damage and age classes. The remaining foliage was recorded for each tree using the following classes: 0, 10, 30, 50, 70, 90 and 100%. The defoliation levels in 1996 were estimated by disregarding the 1997 needle age class. Thirteen ca. 40-year-old sample trees representing different damage classes were felled, and the remaining foliage of all branches was estimated by needle age class using the above-mentioned scale. One branch in each of the whorls 1996, 1991, 1986 and 1981 was sampled and its needle dry weight was determined. The sample branch data confirmed the field observations that virtually no additional defoliation took place in 1997. The damage classes estimated from the CIR-pictures only agreed with the field damage estimates at the higher end of the damage scale. In contrast, the field estimate correlated well with plot means derived from tree-wise estimates (R-2 = 0.93), and with with the calculated needle biomasses per tree (R-2 = 0.90). Thus, the field damage classification was supported by the more detailed defoliation estimates, and hence forms a relevant basis for later growth loss studies

Published in

Silva Fennica
2004, Volume: 38, number: 1, pages: 15-27
Publisher: FINNISH SOCIETY FOREST SCIENCEFINNISH FOREST RESEARCH

      SLU Authors

    • UKÄ Subject classification

      Forest Science
      Environmental Sciences related to Agriculture and Land-use

      Publication identifier

      DOI: https://doi.org/10.14214/sf.432

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/4992