IPNF Soil Monitoring 1997

IPNF Soil Monitoring 1997

1997 MONITORING REPORT

Idaho Panhandle National Forests

Soil Monitoring

This section briefly summarizes the soil monitoring results for 1997. See Appendix F for background information about the IPNF soil monitoring program

and some of the results of our multi-year monitoring.

Our management objectives for the Forests' soil resources are to maintain and restore long-term productivity, to support healthy vegetative communities,

and to protect watersheds. Key elements of maintaining long-term soil productivity include retaining the following soil properties within their natural ranges of variability: the surface organic layers, the surface volcanic ash, and the low bulk density of the surface volcanic ash.

a. Equipment operations

This years monitoring focused on harvester-forwarder logging operations. Four units were monitored: three units on the Lakeface-Lamb sale area at Priest Lake and one unit on the Trout Creek sale at Sandpoint. The Lakeface-Lamb units were partially logged and then grappled piled, the Trout Creek unit was just harvester-forwarder logged. The detrimental compaction on these units ranged from 10 to 18 percent. No detrimental displacement occurred on these units. (See Appendix F for definitions of detrimental compaction, detrimental displacement, and other terms used in this section.)

Many of the designated skidtrails used in timber harvest are restored to near natural conditions after the harvest operation. Numerous decompaction methods have proved to be successful, they are as follows:

-The winged subsoiler has done a good job of breaking up compaction over a full range of soils and compaction depths on the Forest.

This years monitoring looked at the use of a track mounted excavator with bucket to break up heavy compaction on skidtrails within the Bobcat Timber Sale, and lightly excavated skid roads which occur on volcanic ash and clay loam soils within section 4 of Hume Creek on the St. Joe District. The results looked very good, in that the compacted soil layers were highly fractured and little to no soil horizon mixing occurred.

A fisheries project was monitored this year which involved the gathering of wind blown trees around the Coeur d' Alene River District for use as large woody debris that is lacking in many streams. The first attempt at this was on the Simmons Draw Timber Sale area, units 1 and 4. These units were previously logged and the slash treated. The leave trees in these units blew down and fisheries specialists extracted these windthrown trees with a track mounted excavator. The end result of the previous logging and fisheries tree extraction produced 21 percent detrimental impacts on unit 1, and 18 percent impacts on unit 4. Unit 1 exceeded our Forest plan standards. With knowledge of this monitoring data, the next tree collection area was on Grass Mountain. On this project area, detrimental compaction and displacement was only 2 percent. An emphasis item in project planning has been keeping to a minimum the amount of land taken out of production for roads, landings and skidtrails.

b. Residue Management:

In monitoring the Lakeface-Lamb and Trout Creek harvest units, we estimated that fine and coarse woody debris was about 20 tons/acre on one unit, and on the other three units the combined woody debris exceeded 35 tons/acre. A balance between fire hazard risk and nutrient cycling needs to be evaluated on sites that are mechanically treated. Leaving too little residue may reduce long-term soil productivity, while leaving too much may cause excessive fire danger.

c. Burning:

This year we monitored the Red Belt and Highway 3 prescribed burn projects on the St. Joe District, and the Castro and Pee Wee prescribed burns on the Priest Lake District. All of these prescribed burns were ignited when surface soil moistures were above 25 percent. The results were excellent, in that none of these burn units had any ground that was severely burned. The prescribed fire reduced fuel hazards, but retained large woody debris and all of the decomposing duff layer and surface soil organics. Soil productivity was improved on all of these prescribed burn sites.

In summarizing the soil monitoring results for 1997, we found that all management activities monitored met Forest and Regional soil quality standards, except for the first fisheries program tree extraction attempt in unit 1 of the Simmons Draw sale area.

Appendix F SOIL MONITORING

This section summarizes the results of multi-year monitoring of the Forest's soil resources. It also discusses some of the practices we have adopted to maintain long-term soil productivity. The soil monitoring section in the earlier part of the report focuses on the monitoring that was done during 1997.

Our forest soil resource objective is to maintain and restore long-term productivity, to support healthy vegetative communities, and protect watersheds. Key elements of maintaining long-term soil productivity include retaining surface organic layers and surface volcanic ash, and maintaining the bulk density of the surface volcanic ash within natural ranges of variability.

We have monitored the full range of our management activities over the last twelve years and have identified the major detrimental impacts and associated practices, which negatively affect the soil quality standards listed in the Forest Plan.

The major detrimental impacts to long-term soil productivity are:

- compaction

- removal of topsoil (displacement)

- land taken out of production by roads, landings and skidtrails

- units with insufficient woody-debris left on-site

- areas that have been severely burned

Detrimental impacts are defined as follows:

-Detrimental Compaction: More than 20% increase in bulk density over natural for volcanic ash surface soils.

-Detrimental Displacement: Removal of the forest floor and one inch or more of the surface mineral soil over a 25 sq.ft. or more area.

-Severely Burned: The soil surface is in a condition where most woody debris and the entire forest floor is consumed down to mineral soil. The soil surface may have turned red due to extreme heat. Also, fine roots and organic matter are consumed or charred in the upper inch of mineral soil.

-Insufficient woody-debris left on-site consists of:

-Douglas-fir sites with less than 5 tons per acre

-grand fir sites with less than 10 tons per acre

-western hemlock/cedar sites with less than 20 tons per acre

-subalpine fir sites with less than 15 tons per acre

When Forest monitoring of soil quality standards began in 1985, tractor yarding and piling were the most common practices used on gently to moderate sloping lands. Our soil monitoring found these practices to result in up to 40 to 90 percent detrimental compaction and displacement. Most of this damage occurred in the piling phase of the operation.

Based on our monitoring knowledge, we have adjusted our management practices by implementing the following actions:

1. Manage ecosystems to maintain acceptable soil productivity potential for trees and other managed vegetation over a minimum of 80 percent of an activity area.

Protection of long-term soil productivity: The following are practices that have been implemented to minimize the impacts of soil compaction, displacement of topsoil and severe burning on long-term soil productivity. The use of these practices in almost all cases has resulted in meeting or exceeding the soil quality standards listed nationally, regionally and within the Forest Plan.

a. Equipment Operations: Cable logging, tractor/skidder yarding and harvester-forwarder/feller-buncher operations over slash, winter logging, using designated skidtrails, broadcast burning during moist soil conditions, leaving slash on the ground (where it will not be a fire hazard), and grapple piling are all practices which minimize soil impacts and protect long term productivity.

On the average, cable logging is the least impactive and will detrimentally affect about 2 percent of an activity area. Dozer and skidder yarding on designated skidtrails and then grapple piling over slash, tends to have the highest impact, while still meeting soil quality standards. This practice detrimentally affects about 18 percent of an activity area. Operating all forms of heavy equipment on designated skidtrails, or on a cushioning layer of slash produces detrimental ground disturbance that ranges between 10 to 20 percent of an activity area depending on distance between skidtrails and amount of slash being operated on. Most of the detrimental impact to the ground is in the form of surface soil compaction.

-The winged subsoiler has done a good job of breaking up compaction over a full range of soils and compaction depths on the Forest.

-The forest cultivator has worked well on compacted surface volcanic ash layers, but was ineffective in breaking up compaction in heavy soils, deeply compacted soils, or on soils with high rock fragment contents.

-Rock rippers have been effective in restoring hydrologic function to compacted roadbeds that contain high rock fragment content.

b. Residue Management: A research publication by Russ Graham (Intermountain Station in Moscow) provides recommendations for the amount of woody debris that should be left on-site to enhance long-term productivity. The recommendations, which are made by habitat type, are listed below and these are minimum requirements. The woody debris left should have a healthy component of material with heartwood or 6 inch+ diameter materials:

Douglas-fir/ninebark 5 - 10 tons/acre

grand fir/beargrass 10 - 15 tons/acre

western hemlock queencup beadlily 20 - 25 tons/acre

subalpine fir/beargrass 15 - 20 tons/acre

Maintenance of fine woody debris is also essential to long-term productivity. In North Idaho many of our soils are nutrient limiting, especially in relation to nitrigen and potassium. Over half of all nutrients contained in trees are tied up in the branches and foliage. Nitrogen tends to be limiting on all soils and potassium appears to be particularly deficient in very weakly weathered soils developing within the Prichard, St. Regis formations, the siltite portions of the Burke formation, and the argillite and carbonatic siltite portion of the Wallace formation. All of these geologic formations are part of the Precambrian metasedimentary Belts. Significant deficiencies of potassium appear to be a major factor in explaining some of our root rot problems. Whole tree yarding can remove up to 40 percent of the soil systems entire reservior of potassium. Research recommends that up to 12 tons per acre of fine woody debris be left on site to help maintain potassium levels. A balance between fire hazard risk and nutrient cycling needs to be evaluated on sites that are mechanically treated.

c. Burning: Prescribed burning during dry conditions creates a mosaic of microsites consisting of severely burned, moderately burned and slightly burned, along with some that remain unburned. This wide range of microsites is the result of differing fuel load and volume, soil and fuel moisture, weather factors and timing.

We have found that by limiting prescribed burning to those times when surface soil moisture is above 25 percent, we will reduce the potential of hot burns producing detrimental burn conditions.