Abstract
Spruce bud scale (Physokermes piceae (Schrnk.)) has gained attention due to recent outbreaks in the eastern Baltic Sea region—Poland, Lithuania, and Latvia. In the spring of 2010, it spread rapidly across Latvia, affecting large areas of Norway spruce stands. Therefore, the aim of our study was to assess the effects of landscape heterogeneity on the damage caused by spruce bud scale in Norway spruce stands. In this study, we evaluated landscape metrics for middle-aged (40 to 70 years old) Norway spruce-dominated stands (>70% of stand’s basal area) in four of the most affected forest massifs and two unaffected forest massifs. We used a binary logistic generalized linear mixed effects model (GLMMs) to assess the effect of environmental factors on the abundance of the spruce bud scale. Our results show that increased local diversity within 100 m of a forest patch apparently reduced the probability of spruce bud scale presence. We also found that the diversity within 1000 m of a patch was associated with an increased probability of spruce bud scale damage. A quantitative analysis of landscape metrics in our study indicated that greater landscape-scale diversity of stands may reduce insect damages.
Highlights
Norway spruce (Picea abies (L.) Karst.) is highly susceptible to both abiotic and biotic disturbances such as windthrow, drought and outbreaks of pests due to tree architecture [1,2,3]
The IJI indicated that the patch interspersion of selected Norway spruce stands distributed quite among available patch categories in both affected and unaffected forest massifs (70.9% and 68.17%, respectively)
The 2010 outbreak of SBS was evaluated through the interrelated analysis of landscape metrics for patches of selected Norway spruce stands among affected and unaffected forest massifs
Summary
Norway spruce (Picea abies (L.) Karst.) is highly susceptible to both abiotic and biotic disturbances such as windthrow, drought and outbreaks of pests due to tree architecture [1,2,3]. Norway spruce in the hemiboreal and boreal forests could potentially lead to difficulties with growth and regeneration under most scenarios of predicted climate changes [2,4,5]. Previous studies in the hemi-boreal and boreal zones have focused primarily on the damage to Norway spruce caused by spruce bark beetles [8,9], whereas little is known about other insect pests, e.g., bud scale [10,11]. Severe damage to Norway spruce stands by scale insects has previously been reported from Lithuania [14]
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