Surface Covering of Downed Logs: Drivers of a Neglected Process in Dead Wood Ecology

Many species use coarse woody debris (CWD) and are disadvantaged by the forestry-induced loss of this resource. A neglected process affecting CWD is the covering of the surfaces of downed logs caused by sinking into the ground (increasing soil contact, mostly covering the underside of the log), and dense overgrowth by ground vegetation. Such cover is likely to profoundly influence the quality and accessibility of CWD for wood-inhabiting organisms, but the factors affecting covering are largely unknown. In a five-year experiment we determined predictors of covering rate of fresh logs in boreal forests and clear-cuts. Logs with branches were little covered because they had low longitudinal ground contact. For branchless logs, longitudinal ground contact was most strongly related to estimated peat depth (positive relation). The strongest predictor for total cover of branchless logs was longitudinal ground contact. To evaluate the effect on cover of factors other than longitudinal ground contact, we separately analyzed data from only those log sections that were in contact with the ground. Four factors were prominent predictors of percentage cover of such log sections: estimated peat depth, canopy shade (both increasing cover), potential solar radiation calculated from slope and slope aspect, and diameter of the log (both reducing cover). Peat increased cover directly through its low resistance, which allowed logs to sink and soil contact to increase. High moisture and low temperatures in pole-ward facing slopes and under a canopy favor peat formation through lowered decomposition and enhanced growth of peat-forming mosses, which also proved to rapidly overgrow logs. We found that in some boreal forests, peat and fast-growing mosses can rapidly cover logs lying on the ground. When actively introducing CWD for conservation purposes, we recommend that such rapid covering is avoided, thereby most likely improving the CWD's longevity as habitat for many species

Ophiostomatoid fungi associated with Ips typographus [L.] on Picea abies [L.] H.Karst.] and Pinus sylvestris L. in North-Eastern Poland

This study dealt with the species distribution and frequency of ophiostomatoid fungi associated with the bark beetle Ips typographus on Norway spruce and Scots pine in north-eastern Poland. At all locations high spruce bark beetle damage has occurred in 2002-2003. Fungi were isolated from beetles and from brood systems of trees infested by the spruce bark beetle. The ophiostomatoid fungi were represented by 13 species. A similar spectrum of ophiostomatoid fungi as that recorded from Picea abies was associated with I. typographus on Pinus sylvestris trees. The most frequent ophiostomatoid species isolated from beetles, phloem and sapwood of Norway spruce were O. bicolor and O. penicillatum. The frequency of occurrence of ophiostomatoid fungi varied significantly among the examined locations. O. bicolor was the most frequently found species on Scots pine infested by I. typographus. The potential role of ophiostomatoid fungi in the epidemiology of I. typographus is discussed. Additionally, we also recorded how the ophiostomatoid fungi associated with spruce bark beetle could grow into phloem and sapwood of Pinus sylvestris trees