Elsevier

Forest Ecology and Management

Volume 257, Issue 9, 16 April 2009, Pages 1939-1944
Forest Ecology and Management

Response of soricid populations to repeated fire and fuel reduction treatments in the southern Appalachian Mountains

https://doi.org/10.1016/j.foreco.2009.02.006Get rights and content

Abstract

Fuel hazards have increased in forests across the United States because of fire exclusion during the 20th century. Treatments used to reduce fuel buildup may affect wildlife, such as shrews, living on the forest floor, especially when treatments are applied repeatedly. From mid-May to mid-August 2006 and 2007, we used drift fences with pitfall traps to capture shrews in western North Carolina in 3 fuel reduction treatment areas [(1) twice-burned (2003 and 2006), (2) mechanical understory cut (2002), and (3) mechanical understory cut (2002) followed by 2 burns (2003 and 2006)] and a control. We captured 77% fewer southeastern shrews (Sorex longirostris) in mechanical + twice-burned treatment areas than in mechanical treatment areas in 2006, but southeastern shrew captures did not differ among treatment areas in 2007. Total shrew captures did not differ among treatment areas in either year. Decreases in leaf litter, duff depth, and canopy cover in mechanical + twice-burned treatment areas may have decreased ground-level moisture, thereby causing short-term declines in southeastern shrew captures. Prescribed fire or mechanical fuel reduction treatments in the southern Appalachian Mountains did not greatly affect shrew populations, though the combination of both treatments may negatively affect some shrew species, at least temporarily.

Section snippets

Study objectives

The National Fire and Fire Surrogate Study was initiated in 2000 in 13 different ecosystems across the United States to assess the effects of prescribed fire and fire surrogate treatments on vegetation, wildlife, pathogens, soil, and the forest floor and to evaluate such variables as fire behavior, fuel, smoke, economics, and wood product utilization. Management objectives at our study site were to restore the area to an open woodland structure, reduce potential wildfire severity, and increase

Study area

Our study was conducted on the 5481-ha Green River Game Land (GRGL) in the southern Appalachian Mountains of Polk County, North Carolina. The southern Appalachian Mountains harbor a high diversity of shrews and are an appropriate location to research their response to fuel reduction treatments (Ford et al., 2005). Elevation on the GRGL ranged from 366 to 793 m. Two of our sites (35°17′9″N, 82°19′42″W) were located approximately 2.9 km NW of our third site (35°15′42″N, 82°17′27″W). Forest stands

Methods

Our experimental design followed the National Fire and Fire Surrogate Study guidelines. Three blocks of 4 treatment areas were implemented in a randomized complete block design for a total of 12 treatment areas. The 4 treatments were randomly assigned to areas within each block. Treatments, representing different fuel reduction options, consisted of an untreated control, a twice-burned treatment, a mechanical understory cut, and a combined mechanical understory cut + twice-burned treatment. Each

Treatments

Mechanical understory cut treatments were conducted between December 2001 and February 2002, 1 year before the first prescribed burn. Trees ≥1.8 m tall and <10.2 cm diameter at breast height (dbh) and shrubs regardless of size were cut using chainsaws and left on site. The first burns were conducted in March 2003. Treatment areas within 2 blocks were ignited by helicopter using spot fires and within 1 block by hand using spot fires and strip-headfires (Greenberg et al., 2007a). Maximum

Soricid sampling

The 2 drift fence arrays per treatment area installed in 2001 were reopened from 17 May to 16 August 2006. We installed 1 additional array in each treatment area, ≥100 m from original arrays; these were opened concurrently on 11 July so that 3 arrays per treatment area were operational from 11 July to 16 August 2006. In 2007, all 3 drift fence arrays per treatment area were opened from 15 May to 13 August. The tri-arm (‘Y’ formation) arrays (Kirkland and Sheppard, 1994), constructed of 50-cm

Habitat data

Habitat variables were measured in all treatment areas during the summer of 2006, the first summer after the second burn. Variables recorded were density, volume, and percent cover of coarse woody debris, litter depth, duff depth, basal area of live and dead trees, percent herbaceous cover, and percent shrub cover. Shrubs were recorded in 2 height categories: < or ≥1.4 m.

We established permanent gridpoints spaced at 50-m intervals throughout each treatment area. Leaf litter and duff depth were

Analyses

We defined relative abundance as the number of shrews captured per 100 array nights. Live and dead shrews were combined in analyses. Shrew relative abundance was compared among treatments using a randomized complete block design ANOVA (SAS v.9.1.3, Cary, NC). We also compared relative abundance per 100 array nights for the most common species, the southeastern shrew (Sorex longirostris). Treatment means of relative abundance were compared using Tukey's Honestly Significant Different (HSD) test.

Results

Leaf litter depth was lower in twice-burned and mechanical + twice-burned treatment areas than in mechanical or control treatment areas; duff depth was lower in mechanical + twice-burned treatment areas than in all other treatment areas (Table 1). Live-tree basal area was 43% lower and basal area of snags was 245% greater in mechanical + twice-burned treatment areas than in mechanical treatment areas because of higher tree mortality (Table 1). Percent cover of shrubs ≥1.4 m was 96% lower in mechanical +

Soricids

We captured 5 species of shrews over both years: 13 least shrews (Cryptotis parva), 53 northern short-tailed shrews (Blarina brevicauda), 23 pygmy shrews, 51 smoky shrews (Sorex fumeus), and 130 southeastern shrews. Least shrews were not captured in twice-burned treatment areas in 2006. Pygmy shrews were not captured in mechanical + twice-burned treatment areas in 2006 or in twice-burned treatment areas in 2007. All other species were captured in all treatments both years. We captured 13 live

Discussion

Our results indicate that shrew response to fuel reduction treatments was minimal, even after 2 prescribed burns and 4–5 years after initial treatments. Shrew abundance differed only between mechanical and mechanical + twice-burned treatment areas. These longer-term results indicate that shrew response to these treatments was consistent with the shorter-term response that was documented soon after initial treatments in the previous study (Greenberg et al., 2007a). During the first 2 years after

Conclusion

Shrew abundance is not greatly affected by prescribed burning for fuel reduction in the southern Appalachian Mountains. However, hot fires that open the canopy may have a slight negative effect on some shrew species, at least immediately after disturbance. On the other hand, treatments that add to the leaf litter layer may benefit shrew populations. Longer-term studies of shrew response to different levels, combinations, and frequencies of fuel reduction treatments could improve our

Acknowledgments

This is Contribution Number 193 of the National Fire and Fire Surrogate Project, funded by the US Joint Fire Science Program, the US Forest Service, Southern Research Station (SRS-4156) through the National Fire Plan, and the North Carolina State University, Department of Forestry and Environmental Resources. A US Forest Service team, consisting of R. Phillips, H. Mohr, G. Chapman, C. Flint, and M. Smith assisted in the field and collected all habitat, fuel, and fire data. K. Pollock provided

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