Soil Resources Analysis Hurricane Ivan-RCW Expansion Project Conecuh National Forest

Transcription

1 Soil Resources Analysis Hurricane Ivan-RCW Expansion Project Conecuh National Forest Current Conditions of Soil Resources: The project area is wide spread across the forest, the result of a large scale storm event. Analysis for the project area takes into account all upland soil types. Soils found within floodplains and/or wetlands are not intended to be within the project area. Small acreages of floodplains and/or wetlands identified by soil type within the project area will be avoided during sale boundary layout and through use of streamside management zones and riparian area management direction in the current LRMP (Land and Resource Management Plan for the NFs in Alabama, 2004). Soils within the boundaries of the proposed project are located in the Southern Loam Hills Subsection. Within this subsection, soils are located in three landtype associations (LTA): Pine Hills, Dougherty Plain, and Wet Pine Flats. The Pine Hills LTA is generally found in the western and south western third of the forest. The Dougherty Plain LTA is generally found in the central southern portion of the forest. The Wet Pine Flats LTA is generally found in the eastern and south eastern third of the forest. Both the Pine Hills and the Dougherty Plain LTAs consist of upland ridges of low relief that have long side slopes. Surface terrrain is nearly level to gently sloping. The Wet Pine Flats LTA consists of broad, nearly level to flat uplands of very low relief. Surface terrain is nearly level to undulating. The Pine Hills LTA soils formed in sandy loam, loam, and clayey marine deposits. Soils found in the Dougherty Plain and Wet Pine Flats LTAs formed in marine sediments derived from solution and collapse of limestone and the slumping of sandy and clayey sediments. Typical soil characteristics of the Pine Hills LTA are deep, well drained, moderate to moderately rapid to rapidly permeable soils with sandy loam or sandy clay subsoils. Typical soil characteristics of the Dougherty Plain are deep, well drained, slow to moderately permeable soils with sandy clay loam subsoils. Typical soils characteristics of the Wet Pine Flats LTA are deep, somewhat poorly to poorly drained, moderately permeable soils with sandy loam and sandy clay loam subsoils. Wetland soils are common in this LTA. Soils within all three LTAs are acidic and have ph values of strongly acid to very strongly acid. An Order 2 Soil Resource Inventory of the Conecuh National Forest identified 39 soil map units within the proposed project boundary (reference Table 1). Maps are available for viewing at the Ranger Station. Thirty primary soil series are identified within the map units found within the project area. Inclusions of similar and dissimilar soils can be found within each of these map units. A description of the 30 identified soil series and soil maps of the project area can be obtained at the Ranger Station. A total of nine map units are identified as wetland (hydric) soils (reference Table 1, bold print). Initial field review and discussion with District timber staff and marking crews agreed to avoid operating in wetlands by establishing sale area boundaries outside of wetland boundaries. To date, a conservative approach, favoring the soil and water resources, has been taken when delineating SMZs. Specialist review of riparian areas, floodplains and wet sites is currently ongoing during marking and sale area layout as part of pre-harvest monitoring. Environmental Effects on Soil Resources: Disturbance of soils in situ will result in some form of physical, chemical, and biological change. Changes can be short term (lasting less than 5 years), while other changes can be long term (lasting greater than 5 years), or be considered permanent. Analysis takes into account three types of effects that can occur to the soil resource as a result of implementing this project: direct, indirect, and cumulative. This proposed action involves thinning stands to improve Red-cockaded woodpecker foraging and nesting habitat and salvage of downed and damaged standing trees, aftermath of Hurricane Ivan. Timber stands 1

2 scheduled for salvage will have soil resource effects similar to the effects of thinning. On-ground assessment found Hurricane Ivan damage to be scattered within individual stands. A detailed discussion of direct, indirect, and cumulative effects of vegetative management on the soil resource are presented in the 1999 Longleaf Restoration Final Environmental Impact Statement (pages 22-23) and are hereby incorporated into this document. Additional information used for soil analysis, alternative comparison and environmetal effects to soil prductivity can be found in the project file (Specialist Report Supporting Documentation by Forest Soil Scientist Art Goddard). No additional mitigations are required beyond the Standards and Guidelines specified in the LRMP. Soil Name (Map Unit Symbol #) Table 1: Project Area Soils Data. Slope (%) Compaction Hazard Erosion Hazard Arundel loamy fine sand (2) 8-25 Slight Severe Atmore silt loam (3) 0-3 Severe Slight Benndale fine sandy loam (5) 2-5 Slight Slight Benndale fine sandy loam (5) 5-8 Slight Slight Benndale-Orangeburg Complex (8) 5-12 Slight/Moderate Moderate Bonifay loamy fine sand (13) 0-5 Slight Slight Bonifay loamy fine sand (14) 5-10 Slight Slight Cowarts/Dothan Complex (19) 2-5 Slight Slight Cowarts/Dothan Complex (20) 5-10 Slight Moderate Dorovan Muck (24) 0-1 Severe Slight Dothan fine sandy loam (26) 1-5 Slight Slight Dothan fine sandy loam (27) 5-8 Slight Slight Escambia fine sandy loam (28) 0-3 Moderate Slight Esto fine sandy loam (29) 2-8 Moderate Slight Esto-Dothan-Wagram Complex (31) 5-12 Moderate/Slight Moderate/Severe Eunola loamy fine sand (30) 0-2 Slight Slight Florala sandy loam (32) 0-3 Slight Slight Freemanville fine sandy loam (33) 5-8 Moderate Slight Fuquay loamy fine sand (34) 0-5 Slight Slight Grady sandy loam (35) 0-2 Moderate Slight Grasmere silty clay (36) 0-1 Severe Slight Iuka-Bibb sandy loams (38) 0-2 Slight Slight Lucy loamy sand (42) 0-5 Slight Slight Lucy loamy sand (43) 5-8 Slight Slight Lynchburg sandy loam (44) 0-2 Slight Slight Muckalee, Bibb, and Osier soils (10) 0-2 Slight Slight Orangeburg fine sandy loam (47) 2-5 Slight Slight Orangeburg fine sandy loam (48) 5-8 Moderate Slight Plummer loamy sand (50) 0-5 Slight Slight Plummer loamy sand (51) 5-12 Slight Moderate Ponzer muck (53) 0 Severe Slight Rains sandy loam (54) 0-2 Slight Slight Ruston very fine sandy loam (58) 2-5 Moderate Slight Tifton fine sandy loam (62) 2-5 Slight Slight Troup loamy sand (63) 0-5 Slight Slight Troup loamy sand (64) 5-15 Slight Severe Wagram loamy sand (66) 0-5 Slight Slight Wagram loamy sand (67) 5-8 Slight Moderate Weston fine sandy loam (68) 0-1 Severe Slight 2

3 No Action Alternative : There would be no potential for any direct, indirect, or cumulative effect upon the soil resource as a result of implementing this alternative. Effects from existing roads, implementation of the Longleaf Restoration EIS, continued prescibed burning, and other small scale land practices would continue to occur. Some opportunities to improve watershed conditions through implementing watershed improvement projects and road improvements would be forfeited. Proposed Action Alternative: The potential risk for a reduction in soil productivity from this alternative is slight. This alternative proposes thinning up to 8,138 acres and salvaging approximately 8,020 acres. The majority of the acreage to be thinned or salvaged has a slight rating for soil compaction. Approximately 1,327 acres (8.2%) have a moderate potential for soil compaction and approximately 671 acres (4.1%) have a severe potential for soil compaction (Figure 1: Soil Compaction Hazard). The majority of the soils having a severe soil compaction hazard rating are located within wetlands which will be avoided. The Grasmere soil series is the only soil that is rated severe for compaction that is not a wetland soil. Grasmere soils are genrally located at the heads of drains. Figure 1: Soil Compaction Hazard Acres slight moderate severe 0 No Action Proposed Action Alternatives A severe compaction hazaed rating is a result of silty clay surface textures. The soil series rated as moderate for soil compaction are a result of having clay content near the soil surface. These soils are the Escambia, Esto, Freemanville, Orangeburg, and Ruston soil series. The Grady soil series is rated as moderate for soil compaction but is also a wetland soil which will be identified and avoided during stand layout. The guidelines for avoiding wet areas during stand layout, use of SMZs, and performing management practices during either dry soil moisture periods or dry seasonal periods or with use of low PSI equipment will reduce the potential for soil compaction. The maps of soils rated moderate and severe for potential compaction are filed at the Conecuh Ranger District office as part of the project files. Monitoring of timber salvage from the effects of Hurricane Opal (1996) found soil compaction to be minimal off roads and primary skid trails. Compaction was determined by the percentage of tire rutting. Tire ruts observed averaged less than 6 inches and were over short distances of less than 100 feet. Tire rutting was limited to short distances as a result enforcement of sale contract standards and guidelines. Soil compaction can be reduced by operating equipment during dry ground conditions or by the use of low PSI equimpment. Soil compaction has been found to be the most detrimental on roads and skid trails (primary and secondary trails). Thinning involves fewer passes with equipment ( expected as 3

4 well for salvage operations), usually less than two, compared to even-age harvests. Thinning, besides involving fewer passes, uses less skid trails. Implementation of mitigating measures such as ripping/disking, fertilizing and revegetating, can reduce the effects of soil compaction (improve soil bulk density). The majority of the acreage to be thinned or salvaged has a slight rating for soil erosion. Approximately 1,306 acres (8.1%) have a moderate potential for soil erosion and approximately 909 acres (5.6%) have a severe potential for soil erosion (Figure 2: Soil Erosion Hazard). The soils having a severe soil erosion hazard rating are located on steep side slopes. Soils on steep slopes are identified as Arundel, Dothan, Troup, and Wagram. Arundel soils are located on slopes up to 25%. Dothan and Wagram soils are located on slopes up to 12% with Troup soils on slopes up to 15%. Sandy surface textures and slopes exceeding 10% are factors accounting for the severe erosion hazard rating. Avoiding placement of temporary roads and primary skids trails on these sites will reduce the potential for severe soil erosion. The Cowarts, Dothan, Orangeburg, Plummer, and Wagam soils located on slopes between 6% and 10% are rated as moderate for soil erosion. Limiting placement of temporary roads and primary skid trails on these sites will reduce the potential for moderate soil erosion. Soil erosion can be expected under high rainfall and road use if standards and guidelines are not followed. Even-age/uneven-age harvest systems have a higher road frequency use than thinning or salvage. Thinning and salvage also does not require site preparation since no trees are being planted. Site preparation usually accounts for most of the erosion potential. Monitoring of even-age harvests and thinning on the Oakmulgee District, Talladega National Forest, (1988) has found soil exposure off roads and skid trails to be minimal, usually resulting from equipment tire slippage and dragging of tree stems. Soil erosion on these areas has been found to occur over short distances with soil being trapped by surface debris. Revegetation has been found to occur over a two year period returning the site back to non-erosive conditions. This alternative does not propose to construct any roads; proposal is to use existing roads. The construction/reconstruction of only 0.8 miles of temporary use roads are planned. Soil erosion will occur primarily from temporary roads accessing stands and from primary and secondary skid trails. Soil productivity is reduced on roads and skid trails primarily from the loss of organic matter and portions of the surface soil horizon. Acceptable soil erosion rates will result with proper road locations on a landscape followed by implementation of standards for erosion, water control, and revegetation. Implementation of soil and water standards will also result in the restoration of site productivity. Figure 2: Soil Erosion Hazard Acres No Action Proposed Action Slight Moderate Severe Alternatives 4

5 The potential risk for cumulative effects of soil erosion and soil compaction on site productivity is slight for acres to be thinned and salvaged. The soils with severe compaction ratings will be avoided. Soils with moderate soil compaction ratings will have some compaction that is expected to recover within 3 to 5 years. Soils with severe and moderate erosion potential are not expected to have erosion loss outside of roads (permanent and temporary) and skid trails. No permanent road construction is scheduled for this project. Use of existing road corridors will not result in increases in acreage taken out of productivity. Temporary loss in soil productivity will occur on the 0.8 miles of newly constructed temporary roads. Application of restoration standards will improve productivity within 3 years. Other ongoing activities includes prescribed burning. Repeated prescribed burns on the same site on a 3-year or less rotation can have a negative cumulative effect on site productivity. Cumulative effects are generally expected to be short term, lasting one year for thinning and salvage sites and three years or less for a prescribed burn after application of soil restorarion standards. On sites where vegetation management and prescribed fire are scheduled within the same three year period, recovery of site productivity may be as long as five years as a result of an expected longer time period for re-vegetation to occur. Restoration of temporary roads, loading decks, and skid trails will restore soil productivity within one to three years. The potential for the highest soil erosion and compaction in this alternative peaks between the years 2004 and Art Goddard, Forest Soil Scientist National Forests in Alabama November 9,