Frigid Xeric Loamy Basalt Mountains and Plateaus Douglas-fir Cool Dry Grass
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Long-term fire exclusion (50 to 100 plus) years (resulting in Alternative State 2).
More details -
Transition T1B
A widespread catastrophic (also referred to as “stand replacing”) fire event occurs as a natural (but relatively rare) event in any phase within the Reference State.
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Transition T1C
Introduced cool-season grasses invading sites near homesteads, pastureland, and other converted land.
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Transition T1D
Site converted to annual cropland, pasture, or hayland (leading to Alternative State 5).
More details - Restoration pathway R2A More details
- Transition T2A More details
- Restoration pathway R3A More details
- Restoration pathway R4A More details
- Transition T4B More details
- Restoration pathway R5A More details
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Restoration pathway R5B
Site preparation and reseeding with native forest vegetation is applied followed by grazing protection on sites that have been converted to non-forest land use(s) for a long period of time (this process is referred to as afforestation).
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Historical Reference State has a variable but predictable plant expression across the landscape. In the larger context, these forests tended to be heterogeneous and spatially complex. A wide array of wildlife species benefited from the edge effects created by the spatial intersections within the larger landscape, and by naturally occurring snags and large woody debris. Under a commonly occurring short-term (repetitive) historic surface fire regime, the mature ponderosa pine plant community (PC 1.1) was likely the most prevalent of the Reference State. Douglas-fir recruitment and establishment were held in check by surface fires.
These forests are comprised of pure, self-replacing stands that function under the ecological parameters that were described in the section entitled “Ecological Dynamics of the Site.”
As stated, fire was the most important disturbance agent in the reference state of the ecological site. The fire regime of the Historic Reference State is summarized as follows:
Fire Regime Group Fire Interval (years)
I 8
Replacement Mixed Low
Fire Severity (% of all fires) 15 18 67
Range of Fire Return Intervals (RFRI- years) 70-400 70-175 8-35
Average Fire Return Interval (AFRI-years) 135 110 30
Source: BpS model 910450
The historic regime average size of any given wildfire event was 1,000 acres.
Fire Severity Classes: Replacement, greater than 75 percent kill or top kill of the upper canopy layer; Mixed 26 to 75 percent, and low severity, less than 25 percent.
Across the overall landscape, stand structure was expressed by a combination of patch openings, clumpy (dense or overstocked) tree groups which were most often pole size or smaller, and as well-spaced mature overstory trees encompassing larger stand groups. These mosaic patterns could occur over the landscapes in a scale of upwards of tens of thousands of acres. Disturbances from fire and other biotic and abiotic sources impacted much smaller areas within the larger landscape, on the order of thousands of acres.
Following a fire or other widespread disturbance in which the vast majority of conifer species are eliminated in a stand replacement event, the key to re-establishing the reference state was dependent on the successful recruitment of early and mid-seral species by seed coming from adjacent sites, or from seed provided by the few remnant surviving seed bearing trees, or from viable soil banked seed. Larger sized patches or impacted areas approaching landscape level scales, isolated from seed sources and devoid of remnant conifer of any size class, tend to revert to long term grass/shrub conditions.
When the understory was impacted by wildfire (with or without overstory impacts), fire adapted species responded well following a light to moderately severe fire impact at the surface. Pine grass and elk sedge usually survived and are rejuvenated by the surface. Fireweed, scour willow, serviceberry and spirea, and lesser amounts of common snowberry, snowbrush ceanothus all increase following these events.
Production Interpretations of the PSME/CARU Reference State:
Site Index
Site index (SI) and the resulting derivation of the Culmination of Mean Annual Increment (CMAI) are different indicators of site quality, as well as an indicator of potential yield and of the general economic rotation age of a site. Site index is a common unit of measure for forest trees and stands. It is a simple measure of the age and height of dominant and co-dominant trees, usually referenced to 50 or 100 years of age. The Culmination of Mean Annual Increment, is expressed as the cubic foot volume at that point (age) where periodic and mean annual increment rates intersect—in other words, where the annual incremental volume growth is at a maximum over the lifespan of a (well managed) stand.
The NRCS (formerly the Soil Conservation Service) typically projects site index and corresponding CMAI values of the forested soils within a survey area, but older survey projects (such as this project) were often lacking in this sample data for this estimation.
A site index value of 83 was assigned to this ecologic site during the Asotin County soil survey process (using Meyer, NRCS ADP code 600—this is a 100-year curve based on total tree age). The CMAI value is 74 cubic feet per acre per year at 40 years. It is unknown how many field plots were taken by the survey crew during the soil survey process.
Stand Density Index (SDI)
Reineke’s Stand Density Index (SDI) is another indexed system which is commonly utilized as an indicator of site quality. SDI is often used to obtain productivity and stocking projections. NRCS does not include SDI interpretations for the forested soils identified in a soil survey area.
SDI expresses stand density (the number of trees per unit area) at a standard average dbh (the diameter at breast height, four and half feet above the ground surface). In the English system, the SDI is indexed at a dbh of 10 inches, as derived from the quadratic mean diameter (QMD: the diameter of the tree of arithmetic mean basal area). Maximum density (Max SDI) is the theoretical biological carrying capacity of the site. Stocking guides can be developed from density parameters in order to manage for future desired conditions, specific to defined management objectives. In most cases the objective is a sustainable production of wood products. Stocking guidelines are normally expressed at the “full stocking” or “normal density” SDI level, which is approximately 80 percent of the stocking density defined as the Max SDI for the site.
The plant association for the ecologic site (PSME/CARU) was derived from the Plant Associations of the Blue and Ochoco Mountains (USFS, Wallowa-Whitman NF, 1992), and a number of productivity projections that were subsequently developed by the Umatilla National Forest for these associations.
The following summary of SI/SDI and various growth parameters is from Umatilla NF publications, derived from PSME/CARU plant association plot data. This summary is based in the reference sources listed below the chart and fully detailed in the reference section.
Plant Association Site Index
GBA** CMAI*** Max SDI**** Full Stocking UZ LZ
PSME/CARU
(CDG112) Ponderosa Pine Meyer Barrett 106 ft2/ac 55 ft2/ac/yr. 329 263 197 132
75*
(see note) 83
Douglas-fir 83 133 ft2/ac 55 ft2/ac/yr. 330 264 198 132
Western Larch 55 no value 65 ft2/ac/yr. 55 no value
Grand fir 50 no value 40 ft2/ac/yr. 48 no value
Douglas-fir 53 90 ft2/ac 50 ft2/ac/yr. 229 183 137 92
50 yr. BH curves: DF (Cochran), WL (Cochran), GF (Cochran) Note: these are all unique, stand-alone references—see WP-SILV-39 for specific reference citations.
100 yr. BH curve: PP (Barrett, Meyer)
Umatilla National Forest Site Quality and Productivity Data, continued:
The site index for all conifer species is best represented in UNF White Paper F14-SO-WP-SIL-39 (2014 revision), on Table 3.
* Note that the Meyer PP SI value comes from Table 3 in Cochran (1984). Western larch and grand fir had limited sample sizes.
** Growth Basal Area (GBA) is originally from Hall (1989) Ecol. Tech Paper 007-88, then brought forward in Cochran et. al.(1994) in PNW-RN-513. GBA is included as a historically referenced productivity value.
*** A more recent production metric is the “Culmination of Mean Annual Increment” (CMAI) which is defined on page 7 of SIL-5. The CMAI yield capability estimations for various tree species measured within associated UNF plant associations is given in subsequent tables of this same reference. The NRCS will use CMAI to project yield estimations for forested soil series (by management level tree species) identified in a modern era soil survey. CMAI values are associated with NRCS calculated SI values from representative soil sample plots. NRCS identifies the year at which the CMAI occurs for any given soil series and tree species. Note again that this estimation is not provided in this MLRA in SE Washington.
**** Maximum SDI values are derived from Table 3 of SIL-39. Full stocking, and the Upper limit of the management zone (UZ) and the lower limit of the management zone (LZ) are calculated from Table 1 of the same publication. (shown on the next page)
* The site index of 75 given for Meyer is from Table 3 in the Umatilla NF Stocking Levels publication. **The SI value of 83 is also from that table, using a conversion factor of the SI for Meyer multiplied by 1.1 to derive a comparable Barrett SI. ***The SI for Douglas-fir is from site index curves used in R6-ECOL-TP-225A-86 and carried forward into Cochran (1994)
Stand Density Index (SDI), Max SD, Full Stocking, UZ and LZ are best defined by Powell in the referenced white papers.
Dominant and Indicator Species of the ESD:
PLANT LIST—Douglas-fir Warm Dry Grass
Source: R6-ERW-TP-036-92 and USFS FEIS
Trees:
Species Name Scientific Name ADP Code Ecological Interpretation
Western larch Larix occidentalis LAOC Early Seral
Douglas-fir Pseudotsuga menziesii PSME Mid Seral
Ponderosa pine Pinus ponderosa PIPO Early Seral, dominant fire-maintained conifer
Lodgepole pine Pinus contorta PICOL Early seral (minor seral)
Shrubs:
Species Name Scientific Name ADP Code Ecological Interpretation
Pinemat manzanita Arctostaphylos nevadensis ARNE Susceptible to fire kill, resprouts easily
Creeping Oregon grape Berberis repens BERE Sprouts from surviving rhizomes following fire
Oregon boxwood Pachistima Myrsinites PAMY Moderately resistant to fire-kill
Baldhip rose Rosa gymnocarpa ROGY Sprouts from surviving root crowns
Birchleaf spirea Spirea betulifolia SPBE Resistant to fire, increases
Common snowberry Symphoricarpos albus SYAL Maintains pre-fire frequency/coverage
PLANT LIST—Douglas-fir Warm Dry Grass
continued
Forbs:
Species Name Scientific Name ADP Code Ecological Interpretation
Common Yarrow Achillea millefolium lanulosa ACMIL Reduced by fires; sprouts from shallow rhizomes
Heartleaf Arnica Arnica cordifolia ARCO Susceptible to fire-kill
Broadpetal Strawberry Fragaria virginiana platypetals FRVIP Susceptible to fire-kill, may survive cool burns
Hawkweed Hieracium albiflorum HIAL2 Regenerates from seed, offsite colonizer
Tailcup Lupine Lupinus caudatus LUCA Little impact from most fires
Grasses:
Species Name Scientific Name ADP Code Ecological Interpretation
Pinegrass Carex rubescens CARU Moderately resistant to fire kill: rhizomatous, may invade
Northwestern sedge Carex concinnoides CACO Likely sprouts from rhizomes
Elk sedge Carex geyeri CAGE Seeds and rhizomes, may increase or invade
Western fescue Festuca occidentalis FEOC Usually decreases other than cool, wet burns
Wheeler’s Bluegrass Poa nervosa PONE Resistant, early maturation, little litter
Herbage and Forage Estimations:
The total herbage production for the modal PSME/CARU plant association (measured from sample plots used to support the “Plant Associations of the Blue and Ochoco Mountains” publication) ranged from 228 to 645 pounds/acre, air dried. The average value for the 18 samples plots is 382 pounds/acre, air dried.
Information collected during the development of the “Plant Associations of the Wallow-Snake Providence” indicate that the PSME/CARU plant association produced varying amounts of understory herbage/forage production depending on the seral stage of the site. Those production estimations are as follows:
Late Seral Mid Seral Early Seral
n=2 n=7 n=8
Herbage Production (lbs./acre dry weight)
TOTAL Herbage Range and mean 170-425 (300) 250-1,300 (705) 330-8,000 (475)
CARU Range and mean 60-200 (130) 200-1,100 (605) 100-600 (290)
Total herbage production, and especially forage production, varies significantly depending on canopy coverage, seral stage, forage condition, and the recent fire occurrence(s) on any given site. These factors are compounded by the annual production variance(s) attributed to precipitation and temperature fluctuations.
Submodel
Description
Since the arrival of Euro-American settlers to the region in the late 1880’s, the character and function of these forests have changed. Logging, grazing, conversion to other uses, and fire exclusion have impacted the natural processes of this fire-dependent ecosystem. Depending on the severity and degree of impact, alternative states (which function outside of the parameters of the reference state), have developed. These states include the following:
Conditions favorable to the development of this alternative state began to occur within the Reference State around the turn of the twentieth century. The impacts of fire exclusion, a management goal of post-European settlers, allowed many stands to progress without the natural occurrence of any fire, especially the frequent surface fires. The ecologic benefits of low intensity fires were lost. Fire suppression shifted the age expression and density of the younger stands, and changed the composition of understory vegetation, leading to reduced spatial variation. Fuel levels and fuel stratum layers increased, shifting the fire regime/condition class toward a greater likelihood of mixed and stand replacement fire events
Submodel
Description
This state represents conditions immediately following a catastrophic wildfire, the most severe impacts would be from those fires originating in Alternative State 2 due to the build-up of excessive levels of fuels. Long-term detrimental impacts to wildlife, hydrology and soil quality begin immediately due to the extremely severe intensity of the catastrophic burn. Microbial populations, organic matter levels, and other elements of the native soil resources are negatively impacted. Soil quality is slow to respond to pre-fire levels. Natural recovery of viable forest structure will be very long after these large-scale events. However, the number of wildlife snags may increase in the short-term following the fire.
Submodel
Description
This state developed with the introduction and invasion of introduced grasses and noxious weeds, most notably cheatgrass. These conditions were likely to develop on areas which were near developed farm and pasture lands, and other converted lands or abandoned agricultural land.
Submodel
Description
This state is the usual result of human intervention following a very intensive or total harvest, or outright conversion of the forest, followed by stump removal and the elimination of all other native forest vegetation. Cultivation followed. These sites were often referred to as “cut over farmlands”. In this state virtually all the natural forest functions were eliminated by the conversion to agricultural lands (this includes annually tilled crops as well as hay and pasture).
Submodel
Mechanism
Long-term fire exclusion (50 to 100 plus) years, resulting in Alternative State 2.
Mechanism
A widespread catastrophic (also referred to as “stand replacing”) fire event occurs as a natural (but relatively rare) event in any phase within the Reference State. Approximately three quarters or more of the cone producing age conifer species are virtually eliminated across all age and size classes, potentially leading to a long-term deficiency of seed source(s) necessary for the re-establishment of the early seral Ponderosa pine and mid and late seral species (resulting in the development of Alternative State 3).
Mechanism
Introduced cool-season grasses invading sites near homesteads, pastureland, and other converted land. This includes cheatgrass invasion of overgrazed sites, as well as other excessive disturbance(s) of the native vegetation resulting in Alternative State 4.
Mechanism
Site converted to annual cropland, pasture, or hayland leading to Alternative State 5.
Mechanism
Common fuel reduction practices (low thinning, pruning, etc.) is applied.
Restoration practices that reduce excessive fuels and reduce overstory crown bulk density, as well as the treatment of overstocked clumpy areas, restore this state to the reference condition. Tree planting in larger un-stocked areas where Ponderosa pine and other native seed sources are absent, as well as the introduction of prescribed burning, can contribute to increased resiliency and a return to natural ecologic integrity.
Mechanism
Wide spread catastrophic fire occurs, similar to that of T1B, but the likelihood, intensity and impact of the wildfire event is much greater in scope due to the unnatural buildup of fuels in Alternative State 2, this occurrence also results in the development of Alternative State 3, but with greater impact to the site than in T1B.
Mechanism
Reforestation (e.g. The planting of Ponderosa pine, Douglas-fir) is applied in the aftermath of a catastrophic, stand replacing fire. Native fire adapted understory species rebound naturally.
Ponderosa pine and lesser amounts of Douglas-fir are planted on extensive burned over areas (reforestation) to overcome the lack of adequate seed source from surviving Ponderosa pine, larch, or Douglas-fir of any size or age class. (It is likely that persistent brush or grass/brush cover could exist for an extended period of time years if left un-planted).
Mechanism
Site preparation and reseeding with native forest vegetation is applied followed by grazing protection on sites that have been converted to non-forest land use(s) for a long period of time (this process is referred to as afforestation).
Practices that enable the site to revert to native understory species, for example tree (and/or native species) plantings in properly prepared seedbed conditions, have the potential to restore the function of native Ponderosa pine communities on sites that were converted to agriculture uses in this ecological site (afforestation).
Mechanism
Practices are applied which eliminate unwanted weeds and invasive species, followed by the application of sound agronomic practices or by applying pasture/hayland management. Returns to Alternative State 5, and not to the Reference State.
Areas that were converted to cropland and other agricultural uses and have reverted to undesirable or noxious weeds or other invasive species, are properly treated in order to re-establish viable cropland, pasture or hayland.
Mechanism
Poor management or abandonment leads to weed invasion, often with noxious species resulting in Alternative State 4. This route is more common than T1C.
Mechanism
Site preparation and reseeding with native forest vegetation is applied followed by grazing protection on sites that have been converted to non-forest land use(s) for a long period of time (this process is referred to as afforestation).
Afforestation efforts like those described in Restoration Pathway 4A are needed in order to restore these areas to forest conditions described in the Reference State.
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