SB3R POST-TREATMENT VEGETATION MEASUREMENTS OF STRUCTURE PLOTS ESTABLISHED IN 2003 FINAL REPORT

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1 SB3R POST-TREATMENT VEGETATION MEASUREMENTS OF STRUCTURE PLOTS ESTABLISHED IN 2003 FINAL REPORT Audrey F. Pearson, PhD Ecologia # W. 1 st Ave., Vancouver BC V6K 1G5 ecologia@telus.net and Warren Warttig, RPBio Planning Biologist International Forest Products Ltd A Ironwood Street Campbell River, BC V9W 6H5 Warren.Warttig@Interfor.com IS#COTSA Project # March 31, 2009

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3 3 Introduction In 1995, to ensure forest practices were ecologically sustainable, the Clayoquot Sound Scientific Panel recommended replacing clearcuts with variable retention (Science Panel 1995). At the time, there was very limited experience with variable retention systems, including any information on the most effective retention systems, their influence on regeneration, or the extent to which they emulate natural disturbance patterns. There is a now a growing body of literature on the effects of variable retention on biodiversity. However, we still we do not have a good understanding of how variable retention systems influence regeneration performance or longterm sustained yield or how to adapt our silvicultural standards which are based on clearcuts to variable retention systems, such as multi-storied stocking standards. We have some information on regeneration performance in Douglas-fir forests in the Pacific Northwest but not for coastal forests, with shade tolerant species and different natural disturbance regimes. We also need quantitative measures of variable retention overstory related to the understory regeneration environment and how those conditions change over time, especially in coastal forests where wind throw damage is common. Further we need information on how the understory responds to variable retention over time, both for their biodiversity and cultural value, and competition with regeneration. Variable retention is often categorized descriptively by level of retention (percent retained trees) and pattern (dispersed versus aggregate) (Franklin et al. 1997). However these qualitative descriptions do not necessarily quantify the physical regeneration environment nor are comparisons between different categories straightforward. Further, in coastal forests where wind is a major influence, the actual retention parameters may vary from the initial settings and not remain constant over the life of the stand due to wind damage. In a study of modelling windthrow risk of retained trees in variable retention systems in Clayoquot Sound, the authors found 16% of retained trees were wind-thrown (Scott and Mitchell 2005). Mean stand-level windthrow probability was 0.34 with a broad range from 0.17 to Twenty percent retention appeared to be the critical threshold. When greater than 20% of the original stand was retained, few retained trees were wind-thrown, but below 20% half the retained trees were wind-thrown. Therefore wind damage can be a significant influence that is not accounted for in descriptive variables. Furthermore in west coast ecosystems, removal of overstory increases the vigour of the understory shrub complex which competes with understory trees, a factor which may also change over time. A further consideration in Clayoquot Sound is mandates associated with First Nations. The Clayoquot Sound Scientific Panel Report lists 27 recommendations associated with First Nations perspectives. These include undertaking research to enhance the effectiveness of sustainable ecosystem management. Iisaak is a First Nations-led forest company committed to practicing conservation-based forestry in Clayoquot Sound. They are certified by the Forest Stewardship Council (FSC). In order to address their mandate of upholding FSC certification principles, specifically appropriate monitoring and assessment activities to assess the condition of the forest and the maintenance of the ecological functions and integrity of the forest, they need data, such as generated from this study. First Nations in the Central and North Coast area (Great Bear Rainforest) LRMP processes have similar concerns. Companies working within the Great Bear Rainforest are exploring the possibility of FSC certification as well, especially the Heiltsuk

4 4 Nation. Further, many understory species are culturally important (Clayoquot Sound Scientific Panel Report 3, Appendix V) and we do not know how well these species persist in variable retentions settings. Pre- harvest permanent plots were established in 2003 (under FIA Project Plan # ) for investigating changes in forest structure and composition with differing levels of variable retention (VR). One of the primary functions of VR is to retain some to the ecological attributes associated with the original forest, and is a requirement in large areas of coastal BC (Clayoquot Sound, South and North Central Coast). As structure is often seen as a surrogate for function, specific structural elements focusing mostly near the forest floor will be monitored periodically (non-specified time intervals, but likely in three to five year increments) to assess structural responses under different VR treatments as it compares to unaltered forest structure. The SB3R blocks were harvested in September 2007, and the permanent plots were remeasured in Fall 2008, after one growing season but before planting. The purpose of this project is to measure changes in understorey (regeneration and shrub, herb and moss species) and structural variables with harvest (live trees, snags and coarse woody debris) and monitor their changes over time. Study Area Methods The Kennedy Flats area of Clayoquot Sound is located on the West Coast of Vancouver Island (Fig. 1). There are two physiographic units in Clayoquot Sound, the Estevan Coastal Plain and the Vancouver Island Ranges (Holland 1976). Kennedy Flats is located on the Estevan Coastal Plain, a low-lying plain (< 100m in elevation) that occurs adjacent to the coast and is underlain by relatively soft sedimentary Tertiary rocks with outcrops of the harder rocks of the Vancouver Group. The majority of the Sound consists of the Vancouver Island Ranges, which are pre- Cretaceous sedimentary and volcanic rocks with abundant granite batholiths with a range relief from sea level to 1850 m. Clayoquot Sound is within the Coastal Western Hemlock (CWH) biogeoclimatic zone with Kennedy Flats within the vh1 variant, which is a common ecosystem throughout coastal BC. Kennedy Flats includes the traditional territory of the Tla-o-qui-aht, and Ucluelet First Nations. Tenure includes Parks Canada, BC Parks, Tree Farm License 54 held by Mamook-Coulsons and License 44 held by IISAAK. Clayoquot Sound has a maritime climate, with mild, moist conditions (Environment Canada 2003). Annual temperatures range between 5 to 13 o C with an average of 9 o C. Sub-zero temperatures are rare. Precipitation is abundant, 3200 mm annually, the majority of which falls as rain during the winter. The wettest quarter is November through January when the monthly precipitation ranges from 425 to 458 mm. June to August is typically the driest quarter, with precipitation ranging between 83 and 122 mm. Winds in coastal BC generally vary seasonally, although storms with accompanying strong winds can occur at any time of the year (Clague and Bornhold 1980; Cannings and Cannings 1996). Kennedy Flats is located in the Hydrological Zone 38 Windward Island Mountains (BC Ministry of Forests 1995).

5 5 Sampling design and plot layout There were three treatments; control (not to be harvested), 30% retention and 50% retention (Table 1; Figs. 2-5). Ten 50 m 2 plots (100m apart) per treatment were established in 2003 for a sampling intensity of approximately 1 plot/ha (consistent with standard methods). Plots were established on cardinal directions following standard methods, bouncing back within the treatment block when necessary to stay within appropriate site series and topography. They were remeasured in Plots were relocated using GPS coordinates and finding the rebar established at plot centre, flagging, bearing tree and/or plot corner flagging. In most cases, we were able to re-locate the original rebar. Where the original rebar was missing (such as it was likely crushed under wood), we relocated the plot centre based on the GPS, bearing tree information and remaining flagging. The following variables were measured: At each plot Percent substrate cover (organic, mineral, wood, rocks, bedrock, water) Vegetation species, percent cover Shrub height (see below) Tree regeneration stratified by species, substrate and height class (following methods of regeneration dynamics study (Pearson et al. 2003)) Basal Area (BA) sweep for live and dead standing trees (species and dbh) Photo north and south from plot centre To determine shrub height, the plot was divided into four quadrants along cardinal directions (NE, SE, SW and NW) (Fig. 6). The height of the first 10 individuals of each species encountered was recorded (to ensure random selection), walking a line from plot centre to the edge of the plot, then returning towards plot centre. Quadrants were measured in a clockwise direction. Shrub height was measured from the tallest point on the shrub down the plumb line to height of the base of the stem on the ground or wood (depending on the rooting substrate). In many cases, the shrubs were not growing vertically from the ground, but sideways, then up. Shrubs that were growing down were not measured. When a shrub appeared to be growing from an independent stem, it was considered an individual. Where a group of stems were closely grouped, they were considered one individual. Transects Coarse woody debris was measured following line intercept methods (Marshall et al. 2000) using the 100m distance between the plots as the transect lines. Transects were established between alternate plots, except in the case of SB3R-50 where subsequent transects were measured to avoid measuring the transect line which crossed the road. Transect lengths were less than 100m where the distance between plots was < 100m, as was necessary to avoid cliffs, road edges and second-growth forest. Total transect lengths by treatment were: 50% retention 470m; 30% retention 490m; and Control 475 m. For each transect, diameter, decay class and species of all

6 6 pieces of coarse woody debris > 10 cm in diameter and 2 m in length were measured for pieces whose diameter crossed the line, following standard line intercept methods. The diameter of each piece was measured at the point where it crossed the line. If a piece crossed the line more than once, it was measured each time it crossed the line. Analyses Changes between pre- and post-treatment values were evaluated by determining if there were any significant differences in mean values between years (2003 and 2008). If the variance was homogeneous, a t-test was used, although the majority of the comparisons were non-parametric so a non-parametric t-test, the Mann-Whitney U-test, was performed. The different blocks of the treatments (30-1 and 30-2 and Control-1 and Control-2) were analyzed separately where possible. If there were insufficient sample size (such as values summarized by site), the blocks were combined by treatment. For regeneration, only western redcedar and western hemlock were analyzed because other species (amabilis fir, Sitka spruce, yellow cedar) did not have sufficient sample sizes for analysis. Regeneration and understorey Results Cedar and hemlock regeneration showed a strong response between pre- and post-treatment, but predominantly only for the smallest size class (0-<.10m) (Table 2). However, that result was not consistent between treatments. There was no significant differences for hemlock regeneration for the 0-<.10m size class for Site 30-2 (30% retention) but there was for Site For Control- 1, there were no significant differences in regeneration abundance, including for the 0-<.10m size class. For Control 2, however, there were significant differences for both species and substrates for the 0-<.10m size class. Understorey and shrub response were highly variable, which was not necessarily captured in overall changes in percent cover. At the broad-scale analysis of percent cover by cover class (herb, moss and shrub), shrub percent cover declined for Site 50 and 30-1, but not for 30-2 or the Control sites (Table 3). Moss percent cover declined for Site 50 and 30-2, presumably from disturbance to the forest floor and slow growth recovery. There were no significant changes in herb abundance for any treatment. Changes in shrub height were more variable (Table 4). While average shrub height generally declined, in some cases by half, that decline was not consistent between species or even plots (Table 5). For Control 2, differences in shrub height were only significant for one or two plots within the site, with the exception of salal. For salal (the most abundant shrub species), height declined significantly for all plots in Sites 50 and 30-1, and half of the plots in sites 30-2, Control 1 and Control 2. Structure Basal area of live trees and snags and volume and mean diameter of coarse woody debris were used as structural variables. Basal area of live trees declined for treatment areas, as would be expected post-harvest, although the percent difference was approximately the same for both the

7 7 30% and 50% retention. Both sites are at or above their target retention thresholds. Tree basal area also declined in the controls. Snag basal area did not change for treatments or controls. The volume of coarse woody debris was not significantly different between 2003 and However the mean diameter of wood declined for 30 and 50% retention sites, but not for the Control site. Discussion Given there has already only been one growing season since harvest, the understorey has shown a strong response, although it is unknown the extent to which that initial response will continue. There was a strong response of the smallest seedlings to the open environment, including in Control 2. In contrast in a similar monitoring study, also in Kennedy Flats, natural cedar regeneration showed the strongest increase in abundance from (Pearson and Warttig 2009). The reduction in competing shrub understorey height may promote seedling germination. It is unknown the extent to which the germinants will be successful or whether the shrubs will respond to the increased light and reclaim the site. However, it does indicate that there is a planting window immediately after harvest when shrub competition is reduced. The control sites did show significant changes, especially for seedlings and shrub height, which is likely the result of the edge effects of increased light and reduced shrub competition from disturbance from logging. There was a less than expected response for larger size classes except (10+m). Larger understorey trees may be scarcer with the high shrub competition to begin with or may have protected in the reserve patches within the cutblocks. There were no changes in herb species abundance, which may indicate that the reserve patches in the variable retention, especially near the riparian reserves are sufficient refugia for those species to persist. Again, it is unknown if they will persist over time. The within-site variability needs to be more thoroughly investigated, especially in relation to distance from the edge and whether there are any significant spatial patterns within the individual sites. In a study of second-growth and old-growth vegetation in the North and Central Coasts, Banner and LePage (in press) concluded that vegetation succession following logging disturbance was determined by pre-disturbance species composition. Over the longer-time, we will be able to test their hypothesis. One of the key findings from this study is potentially the recruitment of cedar because of its importance to First Nations. Banner and LePage (in press) found that there was very little second-growth cedar regeneration, even for site series that were cedar/hemlock old-growth. Further, they focused their study on productive sites, which would have the highest probability of producing monumental cedars, large cedars of good form for canoes and poles. One key difference with our study is Banner and LePage used second-growth forests with <25 stems per ha, i.e. effectively no residual structure in contrast to variable retention settings. It is unknown if the differences in success of cedar regeneration are due to site conditions, regeneration conditions or time since harvest or other factors. Given the cultural importance of cedar for coastal First Nations, monitoring whether cedar continues to persist and successfully recruit is an extremely important question in order to determine its long term dynamics and persistence in second-growth stands and the ability of second-growth stands to be future sources of cedar of cultural value. The early regeneration environment cedar is not well understood and long-term studies of early regeneration such as this one may help find patterns in early growth that chronosequence studies cannot.

8 8 Basal area of live trees declined, as would be expected with harvest. However, the key question is how the basal area of the overstory will change over time. After one winter, the overstory retention is at or above the threshold set in the prescription (30% and 50%) retention and above the 20% critical threshold identified by Scott and Mitchell (2005). However, in an adjacent study in Kennedy Flats for VR sites years since harvest, the basal area of the overstorey retention declined by on average 50% from five years ago, with some plots losing all overstory trees (Pearson and Warttig Given the strong relationship between basal area overstory and understory light conditions (Drever and Lertzman 2003), it is important to understand the changes over time e.g. whether individual retention trees gradually fail over time or the majority of trees fail several years after harvest. Such an accessible site as SB3R would be an ideal candidate for annual monitoring of overstorey of basal area, and changes over time, both in terms of better understanding the regeneration environment and evaluating the success of retention systems and variations from initial settings in wind-prone forests. Further, overstory basal area also declined in the control sites either from the influence of windthrow at the edge from opening the site by harvesting or from the severe windstorm in 2006/2007. Again, this pattern has potential implications for the long-term success of variable retention, including the integrity of reserves or leave patches. The volume of snags was not significantly reduced, which may indicate that the harvest practice design was successful in retaining snags, such as adjacent to live retained trees. Again, it is unknown the extent to which these patterns will persist over time, especially with the influence of windthrow in the variable retention settings. Given the site is not planted yet, there is a valuable opportunity to monitor changes in seedling growth in a variable retention setting, with pre- and post-measurements of shrub understory, including prior to planting. The best method would be to measure actual seedling height on tagged trees and follow their progress over time, with remeasurements at a minimum of five year intervals. Again, such an accessible location would make such a monitoring program straightforward and would yield valuable data on the actual growth patterns. SB3R is located within the CWHvh1 variant, with is a common variant on coastal BC. Within the area known as the Great Bear Rainforest (Central Coast) the vh variant constitutes over 25% of the forested area. Due to this representation, it is hoped that the results of this continued study can be cautiously applied to broader areas of coastal BC. Finally, monitoring studies such as this one, especially in such assessable locations, are straightforward and can generate valuable information. We could easily locate the plots after harvest and there were already significant changes after one growing season. These data can be used for growth projection modelling as well as for developing standards for multistoried stands and will be applicable to the Coast Forest Region as well as Clayoquot Sound. This project will provide data for various growth and yield models, such as LLEMS, FORECAST, FORCEE etc., as well as provide data to assist Iisaak Forest Resources to fulfill their mandate of monitoring and assessment for their FSC certification. Further, there is an accompanying stream monitoring project (Warttig 2008), so an ideal opportunity to investigate long-term changes in all aspects ecosystem under variable retention.

9 9 Acknowledgements Thanks to Jessica Hutchinson and Lily McLean for their hard work in the bush, Jeni Christie for assistance in relocating the plots and Dave Edwards for retrieving the original GPS file.

10 10 Literature Cited Banner, A. and P. LePage. in press. Long-term recovery of vegetation communities after harvesting in coastal temperate rainforests of northern British Columbia. Canadian Journal of Forest Research. B.C. Ministry of Forests Watershed Assessment Procedure Guidebook. Forest Practices Branch, Ministry of Forests, Victoria, B.C. Forest Practices Code of British Columbia Guidebook. P. 61, 62 Cannings, R. and S. Cannings (1996). British Columbia: A Natural History. Vancouver, BC, Greystone Books. Clague, J. J. and B. D. Bornhold (1980). Morphological and littoral processes of the Pacific Coast of Canada. The Coastline of Canada. S. B. McCann, Geological Survey of Canada. Paper 80-10: Clayoquot Sound Scientific Panel (Science Panel) (1995). Sustainable Ecosystem Management in Clayoquot Sound. Victoria BC, Canada. Drever, C. R. and K. P. Lertzman (2003). "Effects of a wide gradient of retained tree structure on understory light in coastal Douglas-fir forests." Canadian Journal of Forest Research 33: Franklin, J. F., D. R. Berg, et al. (1997). Alternative silvicultural approaches to timber harvesting: Variable retention harvest systems. Creating a Forestry for the 21st Century: The Science of Ecosystem Management. K. A. Kohm and J. F. Franklin. Washington, DC, Island Press: Holland, S. S. (1976). Landforms of British Columbia: A Physiographic Outline. Victoria, BC, BC Department of Mines and Petroleum Resources. Marshall, P.L, G. David and V.M. LeMay Using line intersect sampling for coarse woody debris. Forest Research Technical Report TR-003 Ecology March BC Ministry of Forests. Pearson, A. F., L. D. Daniels and G. Butt Regeneration dynamics in clearcuts, variable retention and natural disturbance gaps in the forests of Clayoquot Sound, Vancouver Island. FII Final Report. May 15, Madrone Environmental Services Ltd. 35p Pearson, A.F. and W. Warttig Remeasurement of Kennedy Flats permanent regeneration plots established in Final report FIA project number Scott, R.E. and S.J. Mitchell (2005) Empirical modelling of windthrow risk in partially harvested stands using tree, neighbourhood and stand attributes. Forest Ecology and Management 218: Warttig, W Monitoring allochthonous input (leaf litter) on small streams in coastal British Columbia forests under different harvesting regimes and chronosequence and age classes. FIA Land-based programme. Year end report. Project Number

11 Fig 1. Location of Kennedy Flats study area. 11

12 Fig. 2 Map of treatments and plot locations for SB3R 12

13 Fig. 3 Control site.

14 Fig. 4 30% retention site. 14

15 Fig % retention. 15

16 16 Fig. 6. Plot layout for sampling of shrub heights Table 1. Plots and transects established for each treatment type. Site name Treatment type Number of plots per site Transect name Transect length (m) SB3R-50 50% retention SB3R % retention SB3R % retention SB3R-C-1 Control SB3R-C-2 Control Total length transect per site (m)

17 17 Table 2. Mean (M) and standard deviation (SD) of seedling abundance (number per ha) for seedlings by species, substrate and size class. Site Year Species Substrate Data Seedling abundance (number per ha) for size classes (in m) 0 - < < < < < Cw Organic M Cw Organic SD Cw Organic M Cw Organic SD Cw Wood M Cw Wood SD Cw Wood M Cw Wood SD Hw Organic M Hw Organic SD Hw Organic M Hw Organic SD Hw Wood M Hw Wood SD Hw Wood M Hw Wood SD Cw Organic M Cw Organic SD Cw Organic M Cw Organic SD Cw Wood M Cw Wood SD Cw Wood M Cw Wood SD Hw Organic M Hw Organic SD Hw Organic M Hw Organic SD Hw Wood M Hw Wood SD Hw Wood M Hw Wood SD Cw Organic M Cw Organic SD Cw Organic M Cw Organic SD Cw Wood M Cw Wood SD Cw Wood M

18 Cw Wood SD Seedling abundance (number per ha) for size classes (in m) Site Year Species Substrate Data 0 - < < < < < Hw Organic M Hw Organic SD Hw Organic M Hw Organic SD Hw Wood M Hw Wood SD Hw Wood M Hw Wood SD C Cw Organic M C Cw Organic SD C Cw Organic M C Cw Organic SD C Cw Wood M C Cw Wood SD C Cw Wood M C Cw Wood SD C Hw Organic M C Hw Organic SD C Hw Organic M C Hw Organic SD C Hw Wood M C Hw Wood SD C Hw Wood M C Hw Wood SD C Cw Organic M C Cw Organic SD C Cw Organic M C Cw Organic SD C Cw Wood M C Cw Wood SD C Cw Wood M C Cw Wood SD C Hw Organic M C Hw Organic SD C Hw Organic M C Hw Organic SD C Hw Wood M C Hw Wood SD C Hw Wood M C Hw Wood SD Values that were significantly different are in bold. p<0.05

19 19 Table 3. Mean and standard deviation of percent cover of understorey species by cover class Site Class Mean of % cover StdDev of % cover Mean of % cover StdDev of % cover 50 Herb Moss Shrub Herb Moss Shrub Herb Moss Shrub Control 1 Herb Moss Shrub Control 2 Herb Moss Shrub Values that were significantly different are in bold. p<0.05

20 20 Table 4. Mean, standard deviation and count of shrub height (cm) by site and species Site Species Average of StdDev of Count of Average of StdDev of Count of 50 GAULSHA MALUFUS MENZFER RUBUSPE VACCOVAL VACCOVAT VACCPAR GAULSHA MALUFUS MENZFER RUBUSPE VACCOVAL VACCOVAT VACCPAR GAULSHA MENZFER RUBUSPE VACCOVAL VACCOVAT VACCPAR Control 1 GAULSHA MENZFER RUBUSPE VACCOVAL VACCOVAT VACCPAR Control 2 GAULSHA MALUFUS MENZFER RUBUSPE VACCOVAL VACCOVAT VACCPAR Values that were significantly different are in bold. p<0.05

21 21 Table 5. Average, standard deviation and count of shrub height (cm) by species for Control 2 where species count > 3 and species were present in both 2003 and Species Plot Average of StdDev of Count of Average of StdDev of Count of GAULSHA MENZFER RUBUSPE VACCOVAL VACCOVAT VACCPAR Values that were significantly different are in bold. p<0.05

22 22 Table 6. Average, standard deviation and count of salal (GAULSHA) height (cm) for plots for all sites. Site Plot # Average of StdDev of Count of Average of StdDev of 50 Count of Control Control Values that were significantly different are in bold. p<0.05

23 23 Table 7. Average, standard deviation, count and percent difference for basal area (m2/ha) for trees and snags for each treatment Average of BA StdDev of BA Count of BA Average of BA StdDev of BA % difference Site Count 30% retention Tree Snag % retention Tree Snag Control Tree Snag Values that were significantly different are in bold. p<0.05 Table 8. Average and standard deviation of coarse woody debris volume (m 3 /ha) for each treatment Treatment Average of Volume (m 3 /ha) StdDev of Volume (m 3 /ha) Average of Volume (m 3 /ha) StdDev of Volume (m 3 /ha) Control Values that were significantly different are in bold. p<0.05 Table 9. Mean and standard deviation of diameter (cm) coarse woody debris for each treatment Treatment Mean diameter (cm) StdDev diameter(cm) Mean diameter (cm) StdDev diameter(cm) Control Values that were significantly different are in bold. p<0.05