Lower Jack Unit 85 Soil Monitoring Update Sisters Ranger District 7/6/06

Transcription

1 Lower Jack Unit 85 Soil Monitoring Update Sisters Ranger District 7/6/06 The Lower Jack Salvage Sale on the Sisters Ranger District was conducted during the summer months of 2004, approximately eight months after the 2003 B&B Complex fire burned through a number of commercial sale units from the original Lower Jack Timber Sale. Lower Jack unit 85 was monitored in 2004 to assess levels of soil disturbance following salvage activities. Detrimental conditions were measured to exceed Forest Plan standards and guidelines for maintaining soil productivity, primarily as a result of compaction on skid trails and landings and cumulative compaction where off trail tracks overlapped impacts from previous harvest entries. Subsoiling restoration of primary skid trails and landings occurred during the fall of 2004 in order to reduce compaction levels and meet detrimental disturbance standards in the Forest Plan. This report summarizes observations of physical soil conditions and vegetative recovery in areas of disturbance in unit 85 two years following management activities. A number of photos taken during the 2004 monitoring visit were re-shot in 2006 in order to visually display the type and rate of vegetative recovery on different areas of soil disturbance. These include subsoiled and unsubsoiled sections of skid trails, off trail harvester machinery tracks, and undisturbed areas between skid trails. Observations: The recovery of vegetation across the unit area is visually substantial, especially on areas located between skid trails. Primary vegetative species currently present on site are ceanothus, bracken fern and long stolon sedge. The recovery of ceanothus is pervasive and observed to have germinated from seed on approximately 75% of the unit area. The germination observed in 2004 is now a dense cover of individual plants ranging from eight to fifteen inches in height that provides up to 80% aerial cover (Figure_1). Recovery between skid trails on undisturbed ground is very aggressive (Figure_2) and only slightly less so on previously disturbed ground not affected by machines from this most recent entry (Figure_3). Figure_1. Ceanothus germinants in 2004 (left) and 2006 (right).

2 Figure_2. Vegetative recovery on previously undisturbed ground. Figure_3. Vegetative recovery on previously compacted ground. Off trail tracks: The recovery of vegetation on ground disturbed by off trail tracks during this entry is variable. Areas of single out and back passes by the harvester/shear show reasonable rates of recovery, with some vegetation growing back on the tracks themselves (Figure_4). Other tracks have vegetation primarily encroaching in from the lesser or undisturbed areas immediately adjacent to the tracks (Figure_5). Figure_4. Natural revegetation of disturbed ground on off trail harvester/shear tracks.

3 Figure_5. Disturbed ground from out and back pass of harvester/shear. Although the growth and density of vegetative recovery two years following management activities is delayed or reduced on most off trail tracks, many of these areas are supporting individual plants on their surfaces or have vegetating encroaching from lesser or undisturbed areas adjacent to them (Figure_6, left photo). The slight troughs that are present as a result of these tracks were also observed to be accumulating leaf litter and other organics (Figure_6, right photo), a process that should replenish the organic matter layer on the soil surface in these areas and improve growing conditions over time. The physical conditions of these tracks were observed to be conducive to supporting vegetative growth at various levels following this entry. Figure_6. Off trail tracks with sparse vegetation on surfaces and some encroachment from adjacent, undisturbed areas.

4 Gouging and Displacement: Areas in the unit where the maneuvering of harvester shears or skidders gouged and/or displaced soil also show variable rates of vegetative recovery. Soils were mixed, displaced and variably compacted from this type of machinery maneuvering, with a near complete loss of surface organic cover in some areas (Figures_7 and _8, left photos). While these sites are supporting vegetative re-growth (Figures_7 and _8, right photos), the rates appear slowed, possibly due to the displacement of residual seeds from the immediate areas of disturbance. Encroachment of vegetation from adjacent, lesser disturbed areas is likely to be the primary method of vegetative recovery on these areas. Figure_7. Disturbed ground from skidder maneuvering. Figure_8. Disturbed ground from harvester/shear maneuvering. Skid Trails and Landings: Recovery of vegetation on skid trails and landings within the units was also observed to be variable within the unit, especially on subsoiled areas. The majority of skid trails were subsoiled in the fall of 2004 with variable rates of fracture effectiveness due to shallow soil depths and inconsistent radial fracture from the subsoiler wings. Most sections of subsoiled skid trails were highly disturbed during the yarding operations and had little or no vegetation present prior to subsoiling (Figure_9, left photo). Current levels of re-vegetation were influenced by a heavy rainstorm on June

5 13 th, 2006, which gullied portions of subsoiled skid trails where slopes exceeded 10% (Figure_9, right photo). This storm was a short duration, high intensity event that dropped nearly 0.8 inches in less than an hour at the Hogg Pass RAWS station located approximately five miles to the southwest. This storm was likely a greater than 25 year event that produced high energy overland flows throughout the Metolius Basin area. The lack of waterbars or appreciable slash on the surface of these slopes, as well as the loosened nature of the mineral soil following subsoiling, likely contributed to the gullying that occurred during this event. Figure_9. Steep skidtrail after yarding (left) and following subsoiling and rain event (right). The recovery of vegetation on other sections of subsoiled skidtrails is variable. Vegetative recovery and cover provided by woody biomasss appear to increase slightly when the slope decreases, as observed on a section of the same skid trail depicted in Figure_9 located further uphill, and on another skid trail along the top of the ridge (Figure_10, left and right photos, respectively). In general, vegetation was observed to be present on subsoiled skid trail surfaces as smaller sized germinants of ceanothus, bracken fern and long stolon sedge, although vegetation is also encroaching in from adjacent, undisturbed areas. Woody material in the 1 to 3 inch size class (100 hour fuels) accumulated along some sections as breakage during felling and yarding and is present as effective surface cover in variable amounts as high as 25%. Current effective cover from vegetation is generally less than 10%, although some areas have significantly higher levels (Figure_11). The majority of subsoiled trails have variable physical conditions that are generally conducive to continued vegetative recovery, although at a somewhat reduced rate when compared to undisturbed areas. As in gouged or displaced machine tracks, the removal/displacement of residual seeds from

6 multiple yarding passes may be responsible for the delayed recovery of vegetative growth following the reduction of soil strength from subsoiling. Many subsoiled areas also have planted conifer seedlings that appear to have good survival and growth rates one year after planting. Figure_10. Vegetative recovery and woody biomass on lower gradient subsoiled skidtrails.

7 Figure_11. Subsoiled skidtrails with very good revegetation. Vegetative recovery and woody biomass is also present on landings and adjacent skid trails to a lesser degree (Figure_12). Landing areas were also observed to have very high amounts of woody biomass on the surface near the landing piles. Figure_12. Subsoiled skid trail and landing with some vegetative recovery. Unsubsoiled skid trails: Some areas of skid trails were not subsoiled due to physical restrictions or a predetermined decision for a comparison of recovery on site. Anecdotal observations of the differences between the subsoiled and unsubsoiled skid trails include higher amounts of annuals on a non-primary, unsubsoiled skid trail that received multiple trips during skidder turn around traffic (Figure_13). Higher amounts of ceanothus were also observed to be present in one section of unsubsoiled skid trail immediately adjacent to subsoiled sections (Figure_14). A clear reason for this difference was not immediately evident in the field, although seed source is likely to be the primary determinant in the presence of recovery, while physical characteristics of the soil are likely to influence the rate of vegetative growth over an extended period of time.

8 Figure_13. Unsubsoiled area of multiple passes with annuals and planted conifer seedling. Figure_14. Unsubsoiled skid trail section with ceanothus. Conclusions: Overall recovery of vegetation within Lower Jack unit 85 was observed to be very aggressive during the third full growing season following the fire and second full growing season following the salvage operations. Recovery of vegetation on off trail tracks, although variable, is occurring and indicates that the majority of these tracks are not detrimentally impacted. Recovery on subsoiled skid trails and landings is noticeably slower, although quite variable depending on seed source and slope. Ceanothus cover in areas between skid trails that were not disturbed by machine traffic is fairly contiguous and aggressive, while vegetative recovery in areas of machine disturbance from this entry is somewhat less so (Figure_15a and _15b). Overall vegetative recovery across the unit is indicative of the presence of soil conditions sufficient to maintain soil productivity following salvage and subsoiling restoration management activities. Observations of gullying on subsoiled skidtrails exceeding 10% in slope suggest that future management of skid trails located directly parallel to slope aspect should include the creation of

9 waterbars or the placement of slash on the surface following subsoiling operations in order to minimize effects from high intensity rainfall events. Figure_15a. Ceanothus recovery across areas of disturbance in Lower Jack unit (left) and 2006 (right) Figure_15b. Ceanothus recovery across areas of disturbance in Lower Jack unit (left) and 2006 (right)

10 Figure_16. Oblique view of vegetative recovery across Lower Jack unit 85.