BLUNT FIRE INCREMENTAL SILVICULTURE PROJECT

Transcription

1 BLUNT FIRE INCREMENTAL SILVICULTURE PROJECT Results of 8yr. Re-Sampling of Permanent Sample Plots Response of Subalpine Fir (Abies lasiocarpa) to Thinning and Fertilization in the ESSFmc Prepared for: Pacific Inland Resources (A division of West Fraser Mills Ltd.) Forest Investment Account Land Based Investment Project Number: Prepared by: March

2 Table of Contents 1.0 Introduction Methodology Results Conclusion List of Figures Figure 1: Growth Response of Crown Figure 2: Fertilized 2000 Cookie Figure 3: Fertilized 2003 Cookie Figure 4: Control Cookie... 6 Figure 5: Height growth response over past two to three years... 8 Figure 6: Blunt Fire Incremental Silviculture Project Map List of Tables Table 1: History of Activities in the Blunt Fire Project Area... 2 Table 2: Comparison of Diameter and Height Means by Post Treatment Density (1997, 2001, 2006)... 3 Table 3: Comparison of Incremental Changes in Diameter & Height (1997 to 2001) & (2001 to 2006)... 4 Table 4: Comparison of Percent Live Crown and Percent Crown Volume Means (1997, 2001, 2006)... 7 Table 5: Comparison of Crown Volume Factors for 1997, 2001, Table 6: Mean Plot Volumes and Volume per Hectare by Treatment (1997 and 2006)... 9 Table 7: Incremental Increase in Volume per Hectare and Percent Increase (1997 to 2006)

3 Blunt Fire Incremental Silviculture Project 1.0 Introduction The lack of knowledge regarding the growth response of subalpine fir (Abies lasiocarpa) to incremental silviculture treatments was the catalyst for establishing the Blunt Fire Incremental Silviculture Project. The most recent Timber Supply Review for the Bulkley TSA (April, 2001) has projected a 37 percent decline in harvestable volume within the next twenty years. The Bulkley TSA Type 1 Silviculture Strategy (March 2000) has identified mitigation of the projected reduction in harvest levels as a key TSA issue and the application of incremental silviculture techniques has been identified as a key tactical priority. As subalpine fir occupies approximately 48% of the timber harvesting land base, expanding the knowledge regarding the response of subalpine fir to incremental silviculture treatments will provide useful information on the opportunities for their use in mitigating timber harvesting reductions. The Blunt Fire project area is located 65 kilometres north of Smithers at an elevation of 1000 metres. The 950 hectare project area is comprised of a naturally regenerated subalpine fir stand with a minor spruce component. Stand initiation occurred in the 1930 s following a wildfire. This project was established in 1996 through funding provided by Forest Renewal BC. Preliminary reconnaissance through pre-stand tending surveys and the preparation of Stand Management Prescriptions identified the project area in Permanent Sample Plots were established in 1997 to record pre and post treatment stand and site conditions. Re-measurement of the permanent sample plots occurred in the spring of 2001, three years after initial treatment and now in the fall of 2006, eight years after initial treatment. 2.0 Methodology Establishment of the permanent sample plots occurred in 1997 and was based on preliminary reconnaissance and pre stand tending survey information and the use of stereo photographs. Twenty four plots were established; twelve in each of two pre treatment densities (3000 and 8000 stems per hectare) selected as representative of the Blunt Fire project area. Twelve 100 square metre plots (10m x 10m square plots) we established in each of the two densities. In each of the two initial densities, three groups of four plots consisting of a control, and one each of and 1600 stems per hectare post treatment densities. At each of the six control plots, every tree was ribboned, tagged and measured for: species, diameter at breast height, height, percent live crown, percent crown volume and forest health or other unique feature. In each of the eighteen treatment plots, crop trees were pre selected based of the appropriate spacing densities and the crop tree selection criteria from the Schedule C of the spacing contracts. Further information regarding establishment of the permanent sample plots can be found in the report: 1

4 Blunt Fire Incremental Silviculture Project Establishment of Permanent Sample Plots, 1998, Laing and McCulloch Forest Management Services Ltd. All plots were spaced in the fall of These permanent sample plots were initially established to monitor the response of subalpine fir to spacing. In addition to spacing, fertilization of the area occurred over three years, 2000, 2002 and Foliar analysis of the fertilized stands was undertaken in Results indicated a 53 % uptake of nitrogen in the fertilized stands compared to the non-fertilized stands and a resulting increased needle biomass of 29 %. It was expected that this increased photosynthetic capacity would lead to an increased rate of stem growth in succeeding years. Re-measurement of all plot data (species, DBH, height, percent live crown, live crown volume) occurred in 2001 and now in The history of activities is presented in Table 1 Table 1: History of Activities in the Blunt Fire Project Area ACTIVITY SEASON YEAR Stand Reconnaissance and summer/fall 1996 Prescriptions Spacing summer/fall 1997 PSP Establishment summer/fall 1997 Fertilization fall 2000/2002/2003 PSP Re-measurement spring 2001 Foliar Analysis fall 2001 PSP Re-measurement fall 2006 PIR Fertilization Trial 1st year needle weight % 1st yr needle wt (g/100 needles) % Unfertilized Fertilized 0.0 Balsam Spruce Figure 1: Growth Response of Crown

5 3.0 Results The following Tables summarize stand data. Table 2 shows the mean values for diameter and height for each treatment. Table 2: Comparison of Diameter and Height Means by Post Treatment Density (1997, 2001, 2006) DBH (cm) Height (m) Control Control Table 3 shows the incremental change in diameter and height for each treatment for the two treatment periods; 97/01 and 01/06. Except for 8000/1600 height, the increase in diameter and height growth is greater in the treatments than in the associated control. The negative height increment value for the 8000/1600 treatment is a reflection of several wrong height measurements discovered during re-sampling. Increased diameter and height growth is also evident in the 01/06 period relative to the 97/01 period. While all treatments and the controls show a significant increase in growth in the 01/06 period compared to the 97/01 period, the absolute values in the treatments is significantly greater than those of the controls. For example, diameter: 0.6cm control versus 1.8 to 3.1cm for the treatments, height: 0.6m control versus 0.9 to 2.1m for the treatments. One explanation for the variation in results may be the timing of fertilization treatments. While some plots have had six growing seasons since fertilization, others have had as little as three. Variation due to the timing of fertilization is expected to decrease over time. 3

6 Table 3: Comparison of Incremental Changes in Diameter & Height (1997 to 2001) & (2001 to 2006) DBH (cm) Height (m) Control Control Figure 2: Fertilized 2000 Cookie. 4

7 Figure 3: Fertilized 2003 Cookie. 5

8 Figure 4: Control Cookie. 6

9 Table 4 shows mean values for percent live crown and percent crown volume for each treatment and control and by re-sampling year. As these measurements are ocular estimates, significant variation occurs in the values from one period to the next. Generally values increase over time for each of the treatments and the values for the treatments are significantly higher than values for the associated control. Table 4: Comparison of Percent Live Crown and Percent Crown Volume Means (1997, 2001, 2006) Live Crown (%) Crown Volume (%) Control Control

10 Table 5 shows similar trends for crown volume factor which is calculated using the formula; tree height X %live crown X %crown volume. Table 5: Comparison of Crown Volume Factors for 1997, 2001, 2006 Crown Volume Factor Control Control Figure 5: Height growth response over past two to three years. 8

11 Table 6 shows the mean volume per plot and volume per hectare for each treatment. The volumes calculated for the 1997 and 2006 data 2001 data were unavailable for this comparison. The Total Volume includes all trees in the plot. Utilization standard volume is the volume for all trees exceeding a DBH of 17.5 cm which is the current utilization standard for subalpine fir. Piece size volume includes all trees greater than 0.25 m3 in size which is a current operational constraint. Table 6: Mean Plot Volumes and Volume per Hectare by Treatment (1997 and 2006) Total Volume Utilization Standard Volume Piece Size Volume 1997 Volume /plot Volume/ha. Volume/plot Volume/ha. Volume/plot Volume/ha Control Control Control Control

12 Table 7 shows this incremental change in volume between 1997 and 2006 expressed as a volume per hectare and as a percent change in volume per hectare. Table 7: Incremental Increase in Volume per Hectare and Percent Increase (1997 to 2006) Total Volume Utilization Standard Volume Piece Size Volume Volume/ha. % Volume/ha. % Volume/ha. % 3000 Control Control The Tables illustrate three trends. First, the increase in volume is greater on all treatments compared to their associated control. Second, the greatest response to treatment as expressed by increased incremental volume between 1997 and 2006, appears to occur on the 8000sph treatments. Looking at the Utilization Standard Volumes, the 8000sph control volume has doubled whereas the volumes for the 8000sph treatments have increased by a magnitude of approximately five. Thirdly, treatments in the 3000sph stands appear to yield merchantable volumes sooner. Using a minimum volume per hectare of 200m3 as a criterion for determining operability; Table 6 shows that the 3000sph control and two of three of the treatments would be harvestable now using the Utilization Standard Volumes. Using the same criteria for the Piece Size Volume, Table 6 shows that the control would not be harvestable, however one of the treatments would be; and in two of the three treatments, the volumes exceed the control. 10

13 4.0 Conclusion One rationale for establishment of this trial was to obtain more knowledge regarding the response of subalpine fir to incremental silviculture treatments. The project area consists of a 65 year old subalpine fir stand located at an elevation of 1000 metres. Re-sampling of the permanent sample plots has shown significant growth response of diameter, height and crown volume relative to the established controls. Growth responses were found on all treatment densities for both the 3000sph and 8000sph initial densities. No one treatment density could be identified as exhibiting a significantly better response. The relatively short time since treatment and the variation in timing of fertilization are possible factors in explaining this. Identification of a preferred treatment density may become apparent with time and further re-samplings. Another rationale for establishment of this trial was to obtain further knowledge regarding the use of incremental silviculture to reduce the time required for stands to reach merchantability. Increases in volumes were identified for all treatment densities on both the 3000sph and the 8000sph initial densities. While the control sample of the 3000sph has already achieved merchantability, some of the 3000sph treatment samples already have volumes which significantly exceed the volume of the control. No treatment density or the control has achieved merchantability on the 8000sph samples, however, the merchantable volume of the treated plots exceed the control by between 25 and 100 per cent. It is expected that the treatment plots for the 8000sph initial density will achieve merchantability in another 30 to 40 years. Initial density is a factor to consider when identifying stands for treatment with higher density stands requiring more time to achieve merchantability. Although beyond the scope of this trial, a cost benefit analysis would be beneficial for decision making purposes. What are the differences in cost of treatment for a 3000sph stand versus an 8000sph stand and are the costs warranted given the growth responses observed. 11

14 Figure 6: Blunt Fire Incremental Silviculture Project Map. 12