Regeneration Under Partial Cutting for Prognosis BC, MSdk, Cranbrook Forest District: Field Sampling

Transcription

1 Regeneration Under Partial Cutting for Prognosis BC, MSdk, Cranbrook Forest District: Field Sampling Badre Tameme Hassani, M.Sc, Valerie LeMay, Ph.D., RPF, Peter Marshall, Ph.D., RPF, and Abdel-Azim Zumrawi, Ph.D., RPF Forest Resources Management Department University of British Columbia October 9, 2002 Report prepared for: Forestry Innovation Investment, Reference No: R02-07

2 Executive Summary A summary of the field sampling procedures and breakdown of the regeneration data for the Dry Mild Montane Spruce Montane Spruce biogeoclimatic subzone (MSdk) within the Cranbrook Forest District is provided in this report. Field collection was initiated in June 2002 and continued until the end of August A total of 122 plots were sampled from 52 polygons. About 20 % of sampling was carried out on undisturbed and clear-cut sites and the remaining 80% on harvest sites with different retention levels. The plots provide different ranges of residual basal area, number of residual trees, and site factors such as aspect, elevation, geographic locations, and site series. The data are now being used to obtain estimates of regeneration under partially cut stands. The data and results will be linked to Prognosis BC. ii

3 Acknowledgements Funding for this research was provided by Forestry Innovative Investment. In-kind support was provided by the BC Ministry of Forests, Research and Forest Practices Branches, UBC Faculty of Forestry, Tembec Industries, Riverside Forest Products, and Slocan Forest Products. We gratefully acknowledge the support of all collaborators and partners. iii

4 Table of Contents Executive Summary...ii Acknowledgements...iii Table of Contents...iv List of Tables... v List of Figures... v Introduction... 1 Methods... 2 Site Description... 2 Data Collection... 3 Sampling Frame and Site Selection... 3 Selection of Plot Locations and Sample Measurements... 4 Results... 7 Distribution and Number of Plots... 7 Planned Analyses...8 References Cited... 9 iv

5 List of Tables Table 1. Local name, scientific name, and species code for trees of the MSdk... 3 Table 2. Number of available openings in the MSdk, Cranbrook Forest District, by silvicultural system and time-since-disturbance groups... 4 Table 3. Number of plots summarized by variable class List of Figures Figure 1. Plot layout for sampling regeneration, small and large trees... 5 v

6 Introduction Pacific Northwest forests of the US are among the most complicated mixture of tree species (Smith et al. 1996). Mixed-species and/or unven-aged stands, referred to as complex stands, are common in southeast British Columbia. Understanding the dynamics of these complex stands has become a priority since it allows forest managers to predict, compare alternative silvicultural prescriptions, and control outcomes of their actions. Complex stands are created by minor disturbances (Oliver and Larson 1996) and partial cutting is assumed to mimic small-scale natural disturbances. Partial cutting generally involves the manipulation of stands mainly through harvests, regeneration, site preparation, and other silvicultural treatments. These actions increase the structural complexity of the stands and complicate the prediction of the future stands development. The time scale involved in forest dynamics is long and modelling constitutes the unique viable means to forecast and quantify the changes that result from anthropogenic disturbances such as harvesting. The province of British Columbia (BC) has adopted the growth and yield model Prognosis (Stage 1973) as a tool for forecasting future stand conditions based on the expected growth and mortality of individual trees within a stand of the southern interior of BC (Prognosis BC ). Prognosis BC is a growth and yield model for simple and complex forest stands. Many of the submodels of Prognosis BC have been calibrated by the BC Ministry of Forests (MOF) using data from BC. Regeneration and height growth models of Prognosis BC have been calibrated for the following Biogeoclimatic Ecosystem Classification (BEC) subzone variants: 1. ICHmw2 (Boisvenue 1999, Hassani and Marshall 2001; Hassani et al. 2002), 2. IDFdk1, IDFdk2, IDFdk3 (Lencar and Marshall 2000; Martin et al. 2002), and 3. IDFdm2 (Froese et al. 2002). In the summer of 2002, regeneration and height growth data were collected for partially cut stands in the Dry Cool Montane Spruce biogeoclimatic (MSdk) subzone, in the Cranbrook Forest District, Nelson Forest Region in BC. A description of the field collection procedures and a summary of the data gathered are presented in this report. These data are now being used to predict regeneration under partial cutting for MSdk. If funding becomes available, the data will also be used to calibrate the small tree height growth models of Prognosis BC. 1

7 Methods Site Description The Montane Spruce (MS) biogeoclimatic zone occupies the dry climatic region that occurs on the mid-slopes of the Rocky Mountain Trench and the Rockies south of Golden and the eastern Purcell Mountains south of the Spillimacheen River (Braumandel et al. 1992). This zone is found at mid-elevations; it occurs at elevations of about m in wetter climatic areas, and at about 1250 to 1650 m in drier areas (Meidinger and Pojar 1999). MS is bounded by lower elevation forests of the Interior Douglas-fir Zone and high-elevation forests of Engelmann Spruce-Subalpine Fir Zone. The climate is continental characterized by cold winters, moderately short and warm summers (Meidinger and Pojar 1999). The snowpack in winter usually averages between 60 and 100 cm, and the long period of drought in summer often leads to wild forest fires (Meidinger and Pojar 1999). Subalpine fir (Abies lasiocarpa (Hook.) Nutt.) and hybrid (also called interior) spruce (Picea glauca x engelmannii) are the main climax species, whereas lodgepole pine (Pinus contorta Dougl.) dominates the extensive seral stands of the zone. MSdk and the MSdm1 (Okanagan Dry Mild Montane Spruce) are the two MS subzones/variants found in the Nelson Forest Region. However, the MSdk occurs more in the East Kootenay (Braumandel and Curran 1992). Within the Cranbrook Forest District vicinity, the MSdk areas are located on mid-elevation slopes in the Rocky Mountain Trench south of Spillimacheen River, on the valley bottoms and lower slopes of valleys on the eastern flanks of the Purcell Mountains south of the Spillimacheen River; and on valley bottoms and lower slopes in the Rocky Mountains south of the Kichinghorse River (Braumandel and Curran 1992). Elevation of the MSdk ranges from 1200 to 1650 m on south aspects, and from 1100 to 1550 m on north aspects. Summers are warm and dry, and winters are cold with light snowfall. Frost and lack of moisture are major growth limiting factors. Lower to level slopes support fluvial soils with silty, loamy, or clayey surface texture, whereas morainal and glaciofluvial soils with loamy or silty textures occur on level slopes in valley bottoms. Level and depressional sites are covered by organic soils (Braumandel and Curran 1992). Subalpine fir and hybrid spruce with minor amount of Douglas-fir (Pseudotsuga menziesii var. glauca (Mirb.) Franco) are found on climax sites. Frequent standreplacing fires have favoured the extension of seral species such as lodgepole pine and 2

8 western larch (Larix occidentalis Nutt.) throughout the landscape of the zone. Other common species found are western larch, western redcedar (Thuja plicata Donn), trembling aspen (Populus tremuloides Michx.) and cottonwood (Populus trichocarpa Torr. & Gray) (see Table 1 for a full species list). Table 1. Local name, scientific name, and species code for trees of the MSdk. Local Name Scientific Name Code Subalpine fir Abies lasiocarpa (Doug.) Lindl Bl Hybrid spruce Picea glauca (Moench) Voss x Engelmannii Parry Sxw Lodgepole pine Pinus contorta var. latifolia Dougl. Pl Western redcedar Thuja plicata Donn Cw Douglas-fir Pseudotsuga menziesii var. glauca (Mirb.) Franco Fd Western larch Larix occidentalis Nutt. Lw Trembling aspen Populus tremuloides Michx. At Black cottonwood Populus trichocarpa Torr. & Gray Act Paper birch Betula papyrifera Marsh. Ep Data Collection Sampling was based on the sampling and measurement protocols employed in the development of small tree and regeneration component of the Prognosis model (Ferguson and Crookston 1991), and modified by Boisvenue (1999). Similar protocol was used by Lencar and Marshall (2000), Hassani and Marshall (2001), and Froese et al. 2002). Sampling Frame and Site Selection All areas located within the MSdk biogeoclimatic subzone of the Cranbrook Forest District constituted the sampling frame for this project. As Prognosis BC will be mainly used to project future harvesting scenarios, a high proportion of partially harvested sites were targeted for sampling. Regardless of ownership status, all harvested sites that were disturbed (harvested) within the last 5-25 years, accessible, and located within less than a two-hour drive from the forest district office were considered. Sampling effort focused on selecting 80% partially cut (selection, shelterwood, and seed tree silvicultural systems), 10% clearcut stands, and 10% undisturbed sites. The undisturbed sites were selected purposively based on similarities in site characteristics to those in partially cut 3

9 stands, spread geographically across the area, and presenting different ranges of topographical characteristics such as altitude, aspect, and slope. A sample matrix of potential stands was set up using the Ministry of Forests silvicultural ISIS (Integrated Silviculture Information System) and the inventory databases. A total of 583 openings from 40 mapsheets were identified and classified into different combinations of silvicultural systems and time-since-disturbance classes (Table 2). Five openings that had missing information were discarded from the sampling frame. Table 2. Number of available openings in the MSdk, Cranbrook Forest District, by silvicultural system and time-since-disturbance groups. Group (yrs) Clearcut with residuals Clearcut Patch cut Seed tree Shelterwood Selection Missing* 1 (1-5) (6-10) (11-15) (16-20) (21-25) * missing information on the silvicultural system. The polygons of the remaining 578 openings constituted the potential sampling frame for data collection. Priority was given to the polygons that were geographically spread over the whole subzone and to those presenting different ranges of site preparation, regeneration methods, aspect, slope, elevation and the identified site series taken from the ISIS data. Polygons were selected and subsequently located using topographical maps of Cranbrook Forest District. Selection of Plot Locations and Sample Measurements Once polygons were selected, plots were established using systematic sampling with a random start. The number of plots established by polygon and the distance between plots within the same polygon depended on the size of the polygon and the degree of structural variability present. Sites with high degree of structural variability were sampled more heavily. On most sites, plots were established 100 m apart within the polygon and at a minimum distance of 50 m from the road or any other openings to avoid edge effect. For each plot, the BEC sites series was identified and recorded, along with other site factors. These included elevation, slope (percent), slope position, aspect (degrees), and site preparation whenever it was possible. Other information deemed important, such as evidence of grazing or damage, was also noted. 4

10 Trees in each plot were categorized as regeneration, small trees, and large trees. Established regeneration was defined as being at least 15 and 30 cm tall for shade tolerant and shade intolerant species, respectively, and less than 2.0 cm diameter outside bark at breast height of 1.3 m above ground (dbh) (Ferguson et al. 1986; Ferguson and Carlson 1993). Small trees had a dbh between 2.0 and 7.5 cm, and large trees were greater than 7.5 cm dbh. Concentric plots were used to sample the three tree types (Figure 1). Large trees were measured within an m radius plot (0.04 ha). Information on species and dbh was recorded. This allowed the identification of overstory species composition required to estimate retention level and residual basal area, and to study the impact of residual cover on regeneration establishment and growth. When available, two trees from each species were randomly selected and measured for height. Tree health information (pests, pathogens, crooks) was also recorded. Large tree plot radius= 11.28m Small tree plot radius = 3.99m Regeneration plot radius = 2.07m Satellite plot radius=2.07m Figure 1. Plot layout for sampling regeneration, small and large trees. Small trees were measured within the 3.99 m radius plot (0.005 ha). For all small trees tallied, species and dbh values were recorded. Small trees were sub-sampled for total height and five-year height growth. Two trees of each determinant species, when more than two were present, were selected randomly and felled for measurement when whorls could not be confidently counted. For non-determinant species, trees were felled, sectioned and checked until the 5-year height increment was precisely found. The 5

11 previous 5-years height growth was measured as of the end of the previous growing season to ensure that all trees sampled reflected the same growing period. As with the large trees, additional tree health information was recorded when observed. Regeneration was sampled using a 2.07 m radius ( ha) plot. All established and viable regeneration was counted and tallied into height classes as follows: Class 1: cm for shade tolerant species or cm for intolerant species Class 2: cm Class 3: cm Class 4: > cm Regeneration greater than 2 cm dbh, tallied also as small trees, was recorded to avoid double counting on plot summaries. Regeneration was sub-sampled for height and total age both randomly and purposively for some of the best trees on each plot. Two regeneration of each species, if there are more than one species, or four regeneration trees, when only one species was present, were randomly selected and measured for the age and total height. For the consistency with the sampling used by Ferguson et al. (1986) and Ferguson and Carlson (1993) to develop the regeneration component of the Northern Idaho variant of the growth and yield model Prognosis, the same criteria to subsample the best trees were considered. The selection criteria were: (1) the two tallest trees, regardless of species, (2) the one tallest tree of each additional species present, and (3) the tallest of the remaining trees until at least four were sampled. If only one species was present on the plot, height and total age measurements were taken on the four tallest trees. According to Wellner (1940), often more trees occupy a stocking plot than will survive to rotation and best trees are more likely to survive than others. For determinant species, where whorls could be confidently counted, the measurements were made on standing trees whenever possible, whereas non-determinant species were destructively sub-sampled for total age and height. Tree condition, such as any evidence of damage, disease, or insects, was noted as well. Sampling randomly the regeneration will possibly allow the prediction and assignment of ages to non-sampled trees. This helps classifying the seedlings into advance (age >3 years) and subsequent regeneration (age <3 years) (Ferguson and Carlson 1993) and better predict regeneration establishment and growth following disturbance. To provide information about stocking probability, four regeneration satellite plots were established at m from the central plot, along cardinal directions (Figure 1). Within each satellite regeneration plot, regeneration was tallied by species and height class. Also, whether regeneration was advance or subsequent to the most recent disturbance was estimated. 6

12 Results Distribution and Number of Plots A total of 122 plots from 52 polygons were sampled during July and August Twelve undisturbed plots from six polygons and 13 clearcut plots from 6 polygons were sampled. The remaining plots included different silvicultural systems (clearcut with residual, patch, seed tree, shelterwood, selection). Table 3 provides ranges of data for the selected variables. Table 3. Number of plots summarized by variable class. Years Since Last No. Plots Site Preparation No. Plots Residual Basal No. Plots Disturbance Method Area (m 2 /ha) 5 6 None Burning Site Series > Slope Position 20 2 Elevation (100 m) Crest <=900 0 Lower Ridge Middle 76 0 (undisturbed) Plateau Terrace Flat Upper Silvicultural system Aspect Clearcut 13 E 19 Slope Percent Clearcut with residual trees 15 Flat 15 Light shelterwood 2 N Seedtree 42 NE Selection 23 NW Shelter/selection 3 S Shelter/seedtree 1 SE Shelterwood 11 SW Undisturbed 12 W 21 >

13 All data collected were entered into Excel spreadsheets, separated into plot information, large tree, small tree, and regeneration components. Planned Analyses Data are now being compiled to provide data summary tables. Modelling of regeneration under partially cut stands is also proceeding using SAS programs (Statistical Analysis Systems Institute (SAS) 1991, Version 8.2). Analysis will be similar to Hassani et al. 2002) and Martin et al. (2002). These data can also be used to model early height growth and stocking, if funding becomes available, as in Lencar and Marshall (2000) and Froese et al. (2002). 8

14 References Cited Boisvenue, C Early height growth and regeneration: applicability of Prognosis components to the southern interior of British Columbia. M.Sc. Thesis, University of British Columbia, Vancouver, BC, Canada. Braumandl, T.F. and M.P. Curran A field guide for site identification in the Nelson Forest Region. Ministry of Forests, Nelson. 311 pp. Ferguson, D.E. and C.E. Carlson Predicting regeneration establishment with the Prognosis Model. USDA Forest Service. Intermountain Research Station Research Paper INT-467. Ferguson, D.E. and N. Crookston User s Guide to Version 2 of the Regeneration Establishment Model: Part of the Prognosis Model. USDA Forest Service, Intermountain Research Station, Ogden, Utah. 34 pp. Ferguson, D.E., A.R. Stage, and R.J. Boyd Predicting regeneration in the grand fir-cedar-hemlock ecosystem of the northern Rocky Mountains. For. Sci. Monogr p. Froese, K., V. LeMay, P.L. Marshall, and A. Zumrawi Prognosis BC calibration in the IDFdm2, Invermere Forest District: Field sampling and preliminary results. Unpublished Report to Forest Renewal BC, PAR02002, Activity location BC Ministry of Forests. 24 pp. Froese, K., V. LeMay, P. Marshall, and A-A. Zumrawi Small tree height increment models for PrognosisBC: IDFdm2 subzone variant, Invermere Forest District. Report for Forestry Innovative Investment, Ref. No. R02-07 Hassani, B.T. and P.L. Marshall Development of regeneration imputation models for the ICHmw2 in the vicinity of Nelson: progress report. Unpublished report to the BC Ministry of Forests, Contract #BDS pp. Hassani, B.T., P.L. Marshall, V. LeMay, H. Temesgen, and A-A Zumrawi Development of regeneration imputation models for the ICHmw2 in the vicinity of Nelson. Report prepared for Forest Renewal BC. PAR02002, Activity Location , 41 pp plus Appendices. ( Lencar, C. and P.L. Marshall Small tree height growth and stocking in the IDF dk1, dk2, and dk3 subzones, Kamloops and Cariboo Forest Regions. Unpublished Report to the Forest Practices and Research Branches, BC Ministry of Forests. 26 pp. Martin, R.A., B. Hassani, V.LeMay, P.Marshall, H. Temesgen, and C.Lencar Development of regeneration imputation models for the IDF dk2, dk2, and dk3 subzone variants of the Kamloops and Cariboo Forest Regions. Report prepared for Forest Renewal BC. PAR02002, Activity Location , 20 pp plus Appendices. ( Meidinger, D. and J. Pojar Ecosystems of British Columbia. Special Report Series #6. B.C. Ministry of Forests Research Branch, Victoria. B.C. Oliver, C.D. and B.C. Larson Forest Stand Dynamics. John Wiley & Sons, Toronto. 520 pp. 9

15 Smith, D.M., B.C. Larson, M.J. Kelty and P.M.S. Ashton The practice of silviculture. John Wiley & Sons, Toronto. 537 pp. Stage, A.R Prognosis model for stand development. Res. Pap. Int 137. USDA Forest Service, Intermt. For. And Range Exp. Stn., Ogden, UT. 32 pp. Statistical Analysis Systems Institute, Inc., SAS Language: Reference, Version 6.2, second edition. SAS Institute, INC., Cary, NC. 10