State 1
Reference

The 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.

The Ponderosa pine forest is comprised of pure, self-replacing stands that function under the ecological parameters that were described in the section entitled “Ecological Dynamics of the Site.”

Fire is the most important disturbance agent in the Reference State.

The fire regime of the Historic Reference Community phase is summarized as follows:

Fire Regime Group Fire Interval (years)
I 6 – 15

Replacement Mixed Low
Fire Severity (%—probability of occurrence) 15 18 77
Mean Fire Return Interval (MFRI- years) 125 35 15

Primary Source: BpS model 910531
Also referenced by FEIS “Fire Regime/Blue Mountains” publication, Fire Ecology of N. Idaho Habitat types, and FEIS Fire Regimes of N. Rocky Mountain Ponderosa pine communities.

Fire Regime Groups: I: 0-35 year frequency, surface severity; II: 0-35 year frequency, replacement severity; III: 35-100+ year frequency, mixed severity; IV: 35-100+ year frequency, replacement frequency; V: 200+ year frequency, replacement severity
Fire Severity Classes: Replacement, >75% kill or top kill of the upper canopy layer; Mixed 26-75%, and low severity, < 25%

Across the overall landscape stand structure was expressed by a combination of small patch openings, clumpy (overstocked) tree groups in the younger size classes, 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 disturbance event that eliminated or significantly reduced the number of established Ponderosa pine within a given forest stand, the key to re-establishing and sustaining the reference state was dependent on the successful recruitment of Ponderosa pine seedlings from adjacent sources, or from remnant surviving seed trees. Larger sized patches, isolated from seed sources and devoid of remnant Ponderosa pine of any size class, may tend to revert to long-term grass/shrub with very sparse pine occupancy.

The Reference Plant Community was a relatively low-density mature Ponderosa pine stand. The various common successional stages are shown on the state and transition diagram. Those conditions occur in shifting locations across the overall larger landscape over long periods of time.

Characteristics and indicators. Production Interpretations of the Ponderosa pine/snowberry and Ponderosa pine/ninebark Reference State ESD: 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 codominant trees, usually referenced to 50 or 100 years of age. Site index is an indicator of site quality with implications of forest productivity. Additional information on SI and CMAI are provided in the table shown immediately below. Ponderosa pine is the only conifer, and therefore the only commercial tree species in this ESD. Site index value ranges depend on local soil-site characteristics. The combination of these soil-site characteristics is recognized within the defined attributes of established NRCS forested soil series and phases. The NRCS site index interpretations is summarized as follows: Site Quality & Productivity Plant Association Conifer Symbol Site Index-Low Site Index-High CMAI* CMAI Age of CMAI SI ADP Code Curve Basis Low High Ponderosa Pine PIPO/SYAL PIPO 60 122** 53 134 50/40 600 100TA Ponderosa Pine PIPO/PHMA PIPO 85 90 54 89 100/78 600 100TA * cubic foot per acre per year (ft3/ac/yr.) ** a wide span of values in the SYAL phase: the lower values were on Gibbs, Stutler, Speigle, Northstar and Formound soils,and the higher values are represented by Larkin, Driscoll and Jacket soils.

Community 1.1
Reference - Mature Ponderosa Pine

This mid to late-seral phase is the dominant representation of the historical plant community and is sustained by plant adaptations to naturally occurring non-lethal fires. It is typically un-even in age.

Forest understory. Herbage and Forage Estimations:<br /> <br /> Information collected during the development of the “Plant Associations of the Wallowa-Snake Province” (Wallowa-Whitman NF, 1987), indicate that the PIPO/SYAL plant association produced an average of 600 pounds/acre, air dried annual herbage in the study area. Two thirds of the annual herbage amount came from bunchgrass (forage) production, according to that publication. The ninebark phase is limited in available forage data, but likely was more productive than the modal snowberry plant association.<br /> <br /> Total herbage production, and especially forage production, will vary significantly depending on canopy coverage and the recent fire occurrence(s) on any given site, in addition to the annual variance attributed primarily to precipitation and temperature.

Community 1.2
Post Disturbance Regeneration Phase

Figure 7. Scattered natural regeneration of Ponderosa pine seedlings.

Pine seedlings/saplings establish in small-size patch openings created from disturbance events that reduced or eliminated portions of the overstory canopy layer. Seedling recruitment commonly comes from seed production in the years following the event, but also from viable seed banks that were on the ground before the disturbance occurred or from surviving regeneration that pre-dated the disturbance. Favorable weather conditions are necessary for seedlings to establish and develop. Limitations of seed dispersion, distance from seed trees, seriously hinder Ponderosa pine re-establishment in larger patch sizes.

(Note that Ponderosa pine seedlings will become established underneath overstory Ponderosa pine canopy layers, but their development pathway will be impacted by the competition and shade relationships of the overstory stand.)

Ground fires eliminate the majority of young reproduction, setting back the development of the stand to the regeneration phase. The process of seedling establishment is once again dependent on sporadic cone production, coupled with favorable weather until an ecologic threshold stocking level of Ponderosa pine seedlings is achieved.

This can be a short-term and repetitive process until the sapling/pole stage is reached.

Community 1.3
Mid –Development, Closed Phase

Figure 8. Dense or “clumpy” patch of Ponderosa pine poles and small sawtimber sized stems.

The stand reaches the size class(s) of poles to small sawtimber size individuals (5 to 20 inch DBH). At this stage, Ponderosa pine is well suited to survive low intensity surface fire. In the transition phase between the sapling and pole-size class, understory surface fires begin to facilitate a beneficial “thinning” effect in dense stocking conditions (i.e., some trees succumb to the fire while others survive). In other instances, without beneficial surface fire, the stand will exhibit clumpy attributes and experience increased “intraspecific” stand stress as the stand grows. This is the beginning of stem exclusion.

Reoccurring ground fire near the middle and later stages of this phase can provide beneficial self-pruning of the lower limbs of individual trees, which reduces the subsequent ladder fuel risk for those trees into the future.

Community 1.4
Late –Development, Closed Phase

Over a longer period of time an older stand has developed as described in Community Pathway 1.1B. Along the way, large individual Ponderosa pine has succumbed to various disturbance agents such as western pine beetle, lightning strikes, and wind breakage, leading to mortality. The density of trees has continuously been reduced. At the same time, tree diameter(s) have continued to expand as stocking/density stressors continue to influence the stand. Persistent snags and the development of down wood is at an optimum level. Beneath the dominant and co-dominant overstory layer, a limited expression of younger cohorts of Ponderosa pine can exist. This phase may exhibit the characteristics of an “old growth” stand if it progresses and remains intact over time, but this old growth community type is relatively rare in the ecological site.

Pathway 1.1A
Community 1.1 to 1.2

Reference - Mature Ponderosa Pine

Post Disturbance Regeneration Phase

Fine scale patch openings develop from disturbance events. Causes of overstory mortality include “mixed” stand replacement fire events, and from single tree to cluster mortality of mature pine trees that have succumbed to incidences such as beetle kill, mistletoe, windthrow, and storm damage.

Pathway 1.1B
Community 1.1 to 1.4

With time and the absence of major disturbance events, the stand develops into a mature/ over-mature cohort. The threat of mountain pine beetle increases, and individual trees within the canopy are at greater risk of insect and disease mortality which in turn create gaps in the overstory. Additional sunlight will reach the surface and impact the vegetation at that location.

Pathway 1.2B
Community 1.2 to 1.3

Post Disturbance Regeneration Phase

Mid –Development, Closed Phase

The stand develops relatively intact and grows from seedling/sapling to pole/small sawtimer size classes.

Pathway 1.3B
Community 1.3 to 1.1

Mid –Development, Closed Phase

Reference - Mature Ponderosa Pine

The stand develops to the mature phase. Stands have thinned as size classes increased, primarily from the natural exclusion processes as well as from stress induced bark beetle mortality (chiefly mountain pine beetle).

Pathway 1.3A
Community 1.3 to 1.2

Mid –Development, Closed Phase

Post Disturbance Regeneration Phase

Fires occur which are severe enough to eliminate the majority of all Ponderosa pine size classes, and again sets back the development of the site to the regeneration phase.

Pathway 1.4A
Community 1.4 to 1.2

A fire event severe enough to eliminate the majority of the overstory, or less severe but “mixed” in nature in order to create random patch structures, occurs. The stand or impacted areas within the overall stand are set back to the conditions in plant community phase 1.2, in which necessary seed source/seed establishment components must be present in order to achieve adequate Ponderosa pine regeneration.

State 2
Fire Exclusion

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.

Fire exclusion for over 50 years allows Ponderosa pine stands to dominate cover, and form multi-aged medium to dense woodlands. In most cases mixed severity to stand replacing fires will not revert site back to a pine/savanna condition (State 1).

Community 2.1
Long-term Fire Exclusion

Condition 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 fire, especially frequently occurring and beneficial fire episodes. 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 stand replacement fire episodes.

State 3
Invaded

The plant composition in this state is variable with cool-season introduced grasses encroaching from adjacent homesteads and pastures. One annual species of special note that can cause a drastic shift in grass species is cheatgrass (Bromus tectorum). It invades from overgrazed or heavily disturbed pastures and can out compete the native bunchgrasses changing to a shrub/cheatgrass site.

Community 3.1
Introduced Grasses and Weeds

This state developed with the introduction and invasion of introduced grasses and noxious weeds, most notably Kentucky and Canada bluegrasses which migrate from adjacent areas due to excessive grazing pressure. These conditions were more likely to develop on areas which were in close proximity to developed farm and pasture lands, and to other converted or abused lands. Shrub species declined.

State 4
Converted

This ecological site over time has had human settlement encroachment, and some of the site extent was converted to homesteads, pastures and cropland.

Community 4.1
Conversion to Agriculture

Some areas on less steep slopes have been converted to cropland, or to pasture or hayland uses.

Note: Significant urban conversion of this forest type has occurred, but this impact is not specifically addressed in this ecologic site. Urban conversion is a permanent loss of the extent of this ecologic site, and not a true state/transition ecologic process. Additionally, there are limited restoration opportunities for land converted to urban uses.

Transition T1A
State 1 to 2

Long term fire exclusion (75-100+) years.

Transition T1B
State 1 to 3

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.

Transition T1C
State 1 to 4

Site converted to annual cropland or pasture/hayland.

Restoration pathway R2A
State 2 to 1

Treatment practices commonly used to rehabilitate forest lands and reduce fuels is applied. Restoration practices that reduce excessive fuel loads and reduce overstory crown bulk density, as well as treatment of overstocked clumpy areas, are beneficial. 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.

Restoration pathway R3A
State 3 to 1

Site preparation and re-seeding with native forest vegetation is applied, followed by grazing protection. Afforestation practices applied as necessary. Practices that enable the site to revert to native understory species, for example tree and/or native grass planting in properly prepared seedbed conditions, have the potential to restore the function of native Ponderosa pine communities in this ESD. Tree planting efforts taken to reestablish the natural forest attributes of the site are referred to as “afforestation.” Proper grazing management must be established.

Transition T3A
State 3 to 4

Site converted to annual cropland or pasture/hayland.

Restoration pathway R4A
State 4 to 1

Site preparation and re-seeding with native forest vegetation is applied, followed by grazing protection. Afforestation practices applied as necessary. Practices that enable the site to revert to native understory species, for example tree and/or native grass planting in properly prepared seedbed conditions, have the potential to restore the function of native Ponderosa pine communities in this ESD. Tree planting efforts taken to reestablish the natural forest attributes of the site are referred to as “afforestation.” Proper grazing management must be established.

Restoration pathway R4B
State 4 to 3

Re-seeding, grazing protection. Afforestation practices applied as necessary.