Summary of Timber Mesa-­‐Vernon WUI Field Work Prepared by Mark R. Sensibaugh and Dave Brewer Ecological Restoration Institute Northern Arizona University PO Box 15017 Flagstaff AZ 86001 [email protected] (928) 523-­‐6651 History – Background The Timber Mesa-­‐Vernon WUI Project (TMP) is located on the Lakeside Ranger District, Apache-­‐
Sitgreaves (A-­‐S) National Forest. This project is located within the boundaries of the Four Forest Restoration Initiative (4FRI) project area, and is part of the 4FRI planning effort. The TMP is in the early stages of planning; as such the specific desired conditions are being developed. This project is approximately 39,500 acres in size with vegetation consisting of a mixture of ponderosa pine/Gambel oak (Pipo/Quga) ponderosa pine/pinyon pine/juniper species, and pinyon pine/ juniper species (PJ) at the lower elevations. The main objective of the project is to improve conditions in these ecosystems so that they are more sustainable (and resilient). District Ranger Edward W. Collins asked the Outreach Unit of the Ecological Restoration Institute (ERI) to help the interdisciplinary (ID) team for the project develop information about the historic “reference conditions” for the different vegetation types within the project area. The ERI would also help the ID team develop management strategies to meet the restoration objectives of the project for the different vegetation types. This paper is a summary of the protocol used by the ERI and the associated information collected from the assessment work. Methods The individual plots were permanently established with GPS points and steel stakes and photos were taken at most plots. To capture data across the entire project area, a series of transects and/or plots were established (see Plot Location Map, Figure 1) in the major forest structural types within the project area. Plot locations were arbitrary, designed to capture as much variation found within the landscape as possible. Information collected included historical tree evidence, existing vegetation, slope, aspect, elevation, estimated fuel loading, current canopy closure, and general soil type Plots established were either 1/10th-­‐acre or 1 acre in size. Plot size depended on time constraints and the need to collect different data. While determining the historical stand structure (presettlement tree density and species) was the focus for all plots, we did capture current stand conditions as they related to changes in forest structure (i.e., information about understory vegetation, tree growth, and tree densities). To reconstruct presettlement stand densities, we located and mapped physical remains of old trees (snags, stumps, downed logs, and stump holes). We also examined living trees in the plots to determine if they germinated prior to European settlement. The process for determining live, pre-­‐settlement trees involved establishing a minimum age for pre-­‐settlement trees, which we decided was 130 years based on a review of the likely settlement activity that would have influenced fire frequency and behavior. This would take into account any trees that began growing in 1881 or earlier. We then cored trees to establish a diameter size that we estimated would represent that minimum age. To account for diameter variation that might occur due to elevation, aspect or other site conditions, we cored a few trees at each plot to validate a diameter at each plot to arrive at the appropriate DBH for a 130-­‐year-­‐old tree, by species. We took borings of trees at each plot-­‐-­‐at breast height (DBH) for ponderosa pine and pinyon pine, and at root collar (DRC) for juniper species. We counted all live trees that had old-­‐tree characteristics (see Table 1) above that diameter within a plot as pre-­‐settlement trees. Presettlement trees and tree evidences were tallied by species and density. In some plots, the physical location of pre-­‐
settlement trees was recorded and a stem map was generated to display the historical stand configuration. We also reviewed the forest inventory data and determined the number of large-­‐diameter trees recorded in that data set. Using the concept that those larger diameter trees were likely pre-­‐settlement trees, we made an additional evaluation of historical densities. In general, this assessment agreed with our plot data. The plot record sheets and photos for each plot are attached in Appendix B. The number of plots established was based on the scope of the evaluation, which was “a rapid assessment,” designed to get a quick overview of the historical reference conditions across the project area. The numbers of pre-­‐
settlement trees by plot are summarized in Appendix A, which also shows the plots by stand type. Results Tree Densities The historical tree densities were lower than the current stand conditions (Appendix A, Table – 1). The historical tree densities we recorded in the rapid assessment plots varied from six trees per acre (TPA) to 80 TPA in the PJ woodland. The average density was about 10-­‐20 trees per acre in the Pipo/Quga. This density was relatively consistent even when the tree species shifted from ponderosa pine/Gambel oak to pinyon/ juniper. However, in a lot of places where the current evergreen woodland now dominates, it appears historically there was an open savanna with perhaps five to seven large alligator juniper (Juniperus deppeana) per acre. Current stand conditions can be summarized from the forest inventory data. In general, current stands conditions were estimated to contain from 100 to more than 400 TPA, with all diameter classes represented. There were also areas that historically were grasslands with no trees as well as juniper savannas where tree densities were 6-­‐12 trees per acre. Pinyon–juniper during the last 130 years has now invaded these areas resulting in some densely stocked stands. These historic conditions were most likely the result of a more frequent fire regime that limited tree establishment. We did not do any fire scar research in this project area, but we did investigate published fire histories conducted near the project area. From other research conducted in this area, we know frequent surface fires were a historic component of this landscape (Swetnam et. al., 1992). There is very little knowledge of fire regime patterns in PJ and Pipo/Quga woodlands or in their ecotones with grasslands below and pine forests above for this area. Using the data we have for this project area, our best estimate of the fire return interval within the project was likely 5-­‐10 years. We also suspect based on the historic information we researched, that this historic regime has been disrupted during the last 100-­‐130 years and fire frequency has been drastically reduced, resulting in the increased densities of trees within the project area. Forest Tree Composition Historically, the project was split into several distinct vegetation types: Pipo/Quga, PJ, juniper savanna, and grasslands. There was very little ”pure” ponderosa pine (PP) within the project, but the ponderosa pine was found across the higher elevations and in the cooler and wetter sites within the project (draws, drainages and north-­‐facing slopes). Historically, the PP extended out into the PJ in small uneven-­‐aged groups, in places as individual trees and in stringers along the drainages, so there are extensive transition zones and it is common to find historic PP, PJ, and oak stumps collectively across a large portion of the landscape. On the north side of Porter Mountain there is currently some mixed conifer, but the historical evidence gathered from a walk through indicates this was a stand of PP and Douglas fir. Historical tree evidence suggested that within the lower elevation portions of the project there were extensive areas that were treeless grasslands or savannas with scattered juniper trees. Some of the rocky areas and cinder cones had low density PJ and some of these places had juniper only. We found little evidence that large areas of PJ woodland existed, again likely the result of relatively frequent fire across the entire landscape. Alligator juniper was the most frequently encountered juniper species, but we did record some Utah and a few one-­‐seed junipers. Historical evidence of juniper was found across the majority of the landscape, being more prevalent on the drier sites. The pinyon was Pinus edulis. We found a wide range of tree ages in the pinyon-­‐juniper stands, but the majority of these trees fell into a younger average age class (<80 years old). We did not generate a historic vegetation map because we feel that the work done by the District Silviculturist to map the areas of base cover types serves as a good starting point from which to incorporate desired conditions. By looking locally at the historic vegetation composition and structure, and comparing that with the current conditions and project objectives and desired conditions it is possible to develop project treatments that will meet the restoration goals of this project. The map in figure 1 can be used to reference historic tree data across the landscape. In addition the District can collect additional reference conditions across the project area using the methods described in this paper to fine tune restoration treatments. Spatial Arrangement GPS locations were plotted for pre-­‐settlement trees within the 1-­‐acre plots. These stem maps are located within the plot write ups in Appendix B. In the PP, we found clumps and small groups of trees (3-­‐
8 trees per group) scattered with large (up to ¾ of an acre in size) generally treeless interspaces. There were a few individual PP trees scattered within some of the openings. In the PJ woodland many of the areas were a large grassland savanna historically. They have now filled in with numerous postsettlement pinyon pine, one-­‐seed juniper, and alligator juniper. The juniper trees were historically more dispersed across the landscape, with some trees in smaller clumps (2-­‐3 trees). We found oaks as single, dispersed trees or small clumps. Understory Understory grass species, although limited, did include a mix of cool-­‐season (C3) and warm-­‐season (C4) grasses. The C3 species included mutton bluegrass, squirreltail, and western wheatgrass whereas the C4 were comprised of predominately mountain muhly, blue grama, and side-­‐oats grama. The low (less than 100 pounds per acre, professionally estimated) understory plant production is likely the direct result of the expansion of the tree species and the competitive edge the woody species have for limited water and nutrient resources. Historically, production in the interspaces between the groups, natural openings, and within the savanna type probably was in excess of 2,000 pounds per acre (from USFS TES inventory data). Another effect of the high density of trees is the development of a 0.5 to 1-­‐inch litter layer that virtually eliminates any current problems with soil erosion; however, it also precludes the development of robust ground vegetation. Summary The most significant condition of the project area is the current tree densities, which if left untreated, will promote conditions conducive to a high-­‐intensity wildfire. There are 10 to 40 times as many trees across the landscape as there were in the historic, frequent-­‐fire regime period. Within the PJ zone the evidence suggests much of the area was an open savanna/grassland with scattered pockets of juniper and occasional pinyon pine in the rocky areas and cinder cones. Most of this vegetation type is currently invaded by PJ, with high tree densities, with the notable exception being areas of past juniper treatments. Some of the lower and mid-­‐elevations were historically juniper savannas with scattered alligator junipers and a variety of age classes dispersed across grassy openings. Historic tree densities were about 10-­‐20 TPA. The former structure can be observed in the project area where treatments left the historic tree structure in place. On some of the mid-­‐elevation benches we encountered PJ stands with historic tree densities of less than 20 TPA. The trees were dispersed with grassy openings. Today these stands have significantly higher densities and the openings are fully occupied with trees. We believe there may have been some areas where woodlands did develop, although it appears that frequent fires were common across the majority of the project area probably limiting these woodlands to shallow rocky sites. In the higher elevations, the historic forest type was a blend of ponderosa pine interspersed with other species. There are only a few parts of the project where pure pine stands existed. Most higher elevations sites were either Pipo/Quga or a mixture of pine, oak, pinyon and alligator juniper as the Pipo/Quga transitioned into the lower, drier environments. The historic tree densities were also much lower (5-­‐30 TPA in total for all species). There is evidence that the PP occupied lower elevations of the project area in the drainages and on sites with favorable conditions (i.e., north-­‐facing slopes and wetter drainages). Today there is extensive coverage of PP across more than half of the project area, as identified by the district map of basic cover type. There is still a blend of oak, pinyon and alligator juniper, with the pine, and total tree densities are 10-­‐20 times what they were under pre-­‐settlement conditions. The second most significant condition is the disruption of the past frequent fire regime during the last 100-­‐130 years. This has likely resulted in the dramatic increase in the number of trees per acre, a substantial decrease in the number and types of understory, ground vegetation species, and a loss of plant vigor and structure. Much of the project area likely historically had a higher percentage of cover dedicated to grasses along with other understory species, including legumes and shrubs. As the overstory densities increased, understory species richness declined. There has been a similar magnitude of decline in larger oak trees. Considerations and Possible Treatments The intent of this assessment is not to provide specific management direction but rather to identify historic conditions as an informational tool to consider in the strategic analysis of the TMP. Some points of consideration, based on the historical conditions, that we would recommend are: 1. The option of returning to pre-­‐settlement conditions across the entire landscape is unrealistic. However, to address current fire and forest health concerns, it would be reasonable to consider restoring a significant amount of the historical composition, spatial structure, and age distribution within the tree-­‐dominated landscape and savannas. Some of the PJ encroachment into the historic grasslands has been initially addressed with past PJ eradication projects. However, it would be good to maintain these treatments and initiate some new treatments where evidence of presettlement woodlands is lacking to re-­‐establish additional grasslands as wildlife, range, and watershed improvement objectives allow. The prescriptions identified in the Community Wildfire Protection Plan (CWPP) for PP restoration and PJ WUI seems appropriate. 2. Consider reducing tree density closer to historical conditions in order to reduce fire, insect and disease risks, and to improve overall ecosystem health. If the historical density of 10-­‐20 trees per acre is too open for other project objectives, then adjust accordingly (e.g., adjust to 2-­‐3 times the historical density), but keep in mind the historical conditions as they relate to climate change (developing resiliency), re-­‐establishing a more frequent fire regime and allowing fire to play a more natural role in the ecosystem. The creation of adequate openings and interspaces will be critical to the establishment of understory vegetation that will; allow managers to use fire as a maintenance/management tool, and expand ecological benefits of the sites by improving habitats, food webs, nutrient cycling, etc. 3. Consider the re-­‐introduction of frequent fire as a management tool for the project area. It will be essential to develop a strategy for using fire as a management tool to meet project objectives across the project area. If openings are created and tree densities are reduced, there will be rapid re-­‐establishment and growth of PP, juniper, oak, and other shrub species. Fire or some other form of treatment (mechanical) will be needed on a frequent basis to eliminate a return to current conditions and to allow grasses and forbs to become established. There will also be a need to monitor noxious weed invasion and then utilize fire treatments accordingly. 4. Consider the possible adverse effects of incorporating a diameter cap on the ability to meet restoration goals given the current stand conditions. The need to re-­‐establish groups and openings restore seeps, springs and riparian areas and to manage encroached grasslands, are critical goals that might not be adequately met with a diameter cap. Table 1 – Old Tree Characteristics In addition to DBH, we used the following characteristics to help us establish the pre-­‐settlement trees in each plot. We used the “Photographic Guide to Pinyon and Juniper Tree Maturity Classes” by Scott E. Sink to determine pre-­‐settlement PJ trees. Crown Shape: Transitional trees have an ovoid shape, flattened top, full and rounded crowns. Old trees (>200 years) are flattened on the top, “bonsai” shape, sparse and open, maybe lopsided. Live Crown Ratio: Transitional trees have moderate live crown ratio; perhaps half the trunk, beginning to self-­‐prune. Old trees have small live crown ratio; often fire-­‐pruned. Branches: Transitional trees have dying fine branches in the interior of the crown, longer branches thickening. Old trees have few, but large branches. Trunk shape: Transitional trees are beginning to loose taper. Old trees are columnar. Bark: Transitional trees have orange or gray flakes with dark edges, shallow fissures, becoming smoother. Old trees have smooth, small flakes, pale orange or gray. Likely Injuries: Transitional trees have relatively few injuries; possibly healed or mostly healed fire scars, lightning scars, and mistletoe. Old trees have fire scars, dead tops, broken branches, lightning scars, rot, burls, and exposed roots. Figure One This is a map showing the location of the rapid assessment plots installed across the landscape. These plot points can be referenced in the summary table of plot data; Appendix A. REFERENCES In addition to the information in this report, we have added some reference material that would be good information for possible future management activities. Articles, papers, and reports: Dieterich, J.H. 1983. Fire history of southwestern mixed conifer: A case study. Forest Ecology and Management 6:13-­‐31. Dieterich, J.H. and A.R. Hibbert. 1990. Fire history in a small ponderosa pine stand surrounded by chaparral. Pages 168-­‐173 in Krammes, J.S., tech. coord, Proceedings, Effects of fire management of southwestern natural resources. Gen. Tech. Rep. RM-­‐191. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. Friederici, P., ed. 2003. Ecological restoration of southwestern ponderosa pine forests. Washington, D.C.: Island Press. Swetnam, T.W., C.H. Baisan, A.C. Caprio, and P.M. Brown. 1992. Fire history in a Mexican pine-­‐
oak woodland and adjacent montane conifer gallery forest in southeastern Arizona. Pages 165-­‐
173 in P.F. Ffolliott, D.A. Bennett, G.J. Gottfried, V.M.C. Hernandez, and A.H. Ortega-­‐Rubio, technical coordinators, Ecology and management of oak and associated woodlands: perspectives in the southwestern United States and northern Mexico. USDA Forest Service. Gen. Tech. Rep. GTR-­‐RM-­‐218. Ft. Collins, CO: Rocky Mountain Forest and Range Experiment Station.
Swetnam T.W. and C.H. Baisan. 1994. Historical fire regime patterns in the southwestern United States since AD 1700. Pages 11-­‐32 in C.D. Allen, ed., Fire effects in southwestern forest: Proceedings of the 2nd La Mesa Fire Symposium. USDA Forest Service, Rocky Mountain Research Station, General Technical Report RM-­‐GTR-­‐286. Ponderosa Pine Restoration The following references are good information sources for restoration management. ERI Working Papers, which can be located at www.eri.nau.edu: ERI Working Paper 7: Establishing Reference Conditions for Southwestern Ponderosa Pine Forests, April 2004. ERI Working Paper 9: Restoration of Ponderosa Pine Forests to Presettlement Conditions, February 2005. ERI Working Paper 22: Restoring Spatial Pattern to Southwestern Ponderosa Pine Forests, June 2008. Restoration of Pinyon-­‐Juniper Huffman, D.W. 2011. http://www.eri.nau.edu/files/General/Huffman_2011_Structural_Dynamics_PJ.pdf Romme, W., C. Allen, et.al. 2007. Historical and modern disturbance regimes of pinon-­‐juniper vegetation in the Western U.S. http://library.eri.nau.edu/gsdl/collect/erilibra/index/assoc/HASHdf01.dir/doc.pdf Huffman D.W. Desired Future Condition Considerations for Pinyon-­‐Juniper. This is attached separately with the appendix material. Region 3 Desired Conditions (Draft) for Pinyon-­‐Juniper; http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5181238.pdf Management of Gambel Oak Abella, S.R. 2008. Gambel oak growth forms: Management opportunities for increasing ecosystem diversity. Research Note. RMRS-­‐RN-­‐37. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Abella, S.R. and P.Z. Fule. 2008. Fire effects on Gambel oak in southwestern ponderosa pine-­‐oak Forests. Research Note. RMRS-­‐RN-­‐34. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Management of Aspen www.Aspensite.org is a great place to get information. Climate Change Region 3 Climate Change Paper http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5181242.pdf Appendix A This appendix is a summary of the rapid assessment plot data. It is attached as a separate document. Appendix B This appendix is a write up of each plot that was put in as part of the rapid assessment. It is attached as a separate document.