Within-Patch Structures Influence Small Mammal Abundance in Managed Forests of Northern California, USA

We evaluated how forest type, vegetation structure in trapping webs, and proximate forest types influenced localized (~6.35 hectares) abundances for commonly captured small mammals in northern California, USA. We trapped from May to August of 2011–13 in 69 forest patches that represented: (1) clearcuts (3–5 years postharvest), (2) 10–20 year-old conifer plantations, (3) rotation-aged conifer stands, and (4) Watercourse and Lake Protection Zones. We captured 11 species; four in sufficient numbers for regression modeling. Our average abundance estimates for the study were 4.57 (standard error [SE] = 0.43), 0.32 (SE = 0.11), 0.90 (SE = 0.30), and 0.25 (SE = 0.09) individuals per web location (~0.75 hectares) for Peromyscus spp., Neotoma spp., California ground squirrels, and Allen’s chipmunks. We found that web-level ground cover (shrubs and grass), downed wood, and types of forests containing our trapping webs best described small mammal abundances, whereas proximate forest types were not important. Our results indicated that retaining localized structures in the form of understory shrub cover and downed wood positively influences small mammal abundance in intensively managed forests of northern California.

Effects of timber harvest on small mammal captures in experimental forestry plots

To investigate effects of timber harvest on small mammals, we compared capture rates in experimental forestry arrays of uncut forest, partial cut forest, and clearcuts with high and low coarse downed wood in Missouri, USA. Past studies show that effects of timber harvest on small mammals depend on species and forest type. We used an information theoretic approach to compare the effects of timber harvest treatment and habitat characteristics on capture rates.Sorex longirostriscaptures were best predicted by timber harvest treatment.S. longirostrishad higher captures in the clearcut with low downed wood, intermediate numbers of captures in the partial cut and clearcut with high downed wood, and low captures in uncut forest. However, despite differences in captures between the clearcuts with high and low downed wood, we found no difference in habitat variables between the two clearcut types.Blarinaspp.,Microtus pinetorum, andPeromyscusspp. captures were best predicted by habitat variables rather than timber harvest treatment.Blarinaspp. captures were associated with lower leaf litter depth.Peromyscusspp. andM. pinetorumcaptures were associated with increased coarse downed wood, possibly due to their preference for nest building under logs. Some of these relationships differ from results in other areas of the United States, which may reflect differences in species-habitat relationships in different forest types or regions. Relationships between species and habitat variables will be useful in adjusting forestry practices to meet species management objectives.

Logging Residue Volumes and Characteristics following Integrated Roundwood and Energy-Wood Whole-Tree Harvesting in Central Maine

Integrated roundwood and energy-wood whole-tree, partial harvesting has become common in Maine over the past decade, yet there is limited information about the volume and characteristics of logging residues left behind on such harvest sites. To better inform forest managers about the downed woody material remaining after whole-tree partial harvesting, we measured downed wood volume and characteristics on 12 harvested sites in central Maine using line intersect sampling. All sites were harvested using mechanical systems (feller-bunchers and grapple skidders) within a year prior to sampling. The mean volume of downed wood across all sites was 726 ± 57 ft3/ac (±SE), 47% of which was residue generated by the harvest. The variability of residue volumes was higher within sites (coefficients of variation between 36 and 69%) than between sites (coefficient of variation, 27%). Coarse woody material between 3 and 6 in. in diameter at the large end dominated the postharvest debris, while logs greater than 10 in. in diameter were scarce. The majority of harvest-generated downed wood was in decay class 1, whereas preharvest debris consisted of mostly decay classes 2, 3, and 4. The volumes of downed wood remaining on the study sites were within the range of volumes found on other managed sites of similar forest types. However, further research is necessary to assess whether these amounts and characteristics are adequate for long-term maintenance of ecological processes.