PROPOSAL FOR A ASPEN AND WHITE SPRUCE MIXEDWOOD MANAGEMENT

  CONCERNS REASONED OPINION (SUBSIDIARITY) ON THE PROPOSAL
18 Revised Proposal to the Isolde and
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Regeneration conditions for spruce can be improved by manipulating the forest canopy and ground surface

Proposal for a aspen and white spruce mixedwood management silvicultural study

(Second draft for reviewing)


Title: Planting white spruce under aspen stands and cluster planting -new approaches for managing spruce and aspen mixedwood stands


Project leader: Jian Wang

Red Rock Research Station

Ministry of Forests


Agency Contact: Dennis B. Sabourin

Silent Running Forestry Consultants Ltd. Chetwynd


Richard Kabzems, Prince George Region, Ministry of Forests


Daniel Lousier, UNBC


Principal Clients: Canfor, Chetwynd Division


Location: Rice Property, Dawson Creek Forest District


Rationale and literature review:


Canfor-Chetwynd operation has purchased the Rice Property with an area of about 6,000 ha. Within the area there are several types of aspen stands: young (about 20 years) and old (about 80-100 years) pure aspen stands. There is some ingress of white spruce in the old aspen stands. Some portions of the land were used as agriculture practices in the past. Canfor’s main management objective is to regenerate the land to conifer (mainly white spruce) forest. Two important considerations influence achievement of this objective. Young aspen stands (age class 2) are of limited extent relative to older age classes within the Dawson Creek District. Secondly it is difficult to regenerate white spruce on clearcuts because of vegetation competition (mainly blue-joint grass). In order to accommodate higher level plans (TSA and LRMP) and achieve the most efficient spruce regeneration, we propose this silviculture study funded by FRBC through Canfor to explore a new way of managing aspen-white spruce mixedwood forests in the BWBS zone. We propose to plant white spruce under aspen overstory to create an aspen and spruce mixedwood stand. This relatively extensive, low impact strategy will be compared to more intensive management approaches such as mechanical site preparation and herbicide methods as well as using sheep to control vegetation.


Regeneration conditions for spruce can be improved by manipulating the forest canopy and ground surface. In boreal mixedwood forests, mechanical site preparation treatments such as trenching, blading, ploughing, mixing or mounding, are commonly used to reduce competition, raise soil temperature and perhaps stimulate mineralization of nutrients (Lieffers and Beck 1994.). There have been several attempts to apply shelterwood systems and mechanical site preparation to regenerate white spruce in boreal mixedwood sites (Youngblood and Zasada 1991). The sheltwood cuts, however, relied on natural regeneration and lacked thorough investigations of the environmental conditions. It is not clear from these trials how residual density of aspen in combination with site preparation affects the regeneration conditions and establishment of white spruce.


Lieffers and Stadt (1994) report that height growth of white spruce seedlings growing under an aspen dominated canopy at 40% full sunlight was approximately equal to that of seedlings growing in full sunlight. However, they also indicate that total growth is best at full sunlight. They suggest that using a shelterwood system which permits 30 to 40% of full sunlight to penetrate the aspen canopy may provide favourable conditions for the establishment and growth of white spruce while avoiding rapid increases in the cover of understory vegetation that can occur following complete removal of the aspen canopy. In 12 year old aspen stands, light levels exceeding 40% of full sunlight are encountered at aspen densities below 10000 stems ha-1 (Iron Creek). In 30 and 40 year old stands (both spaced and unspaced), light levels exceeding 40% are encountered at densities below 3000 aspen/ha. However, it is important to note that these densities will have resulted from self-thinning of stands which initially established at much higher densities. If an aspen stand were maintained at 3000 or fewer stems per hectare from age 5, it is likely that individual trees would be substantially larger than those encountered in natural stands, and that light levels associated with these densities would be lower.


Grass cover will increase from dense to less dense aspen stands. The dominant perennial grass in this area is blue-joint grass (Calamagrostis canadensis (Michx.) Beauv.), a rhizomatous grass that can severely impact reforestation success (Eis 1981, Lieffers et al. 1993). Soil temperatures may also be lower in areas with heavy covers of blue-joint grass (Hogg and Lieffers 1991), limiting the potential for regeneration and growth of spruce.


One negative effect of vegetation control seems to be an increased probability of damage from frost. Sutton (1984) and LePage and Coates (1994) found that frost damage increased in areas where vegetation control was effective. In a study conducted near Fairbanks, Alaska, Cole et al. 1999 found greater susceptibility to early winter frost damage on plots with the greatest vegetation control. When considering a weed control application, it is important to consider the degree to which frost damage might occur on the site. At some point damage to seedlings from frost may outweigh any gain through vegetation control.


Man and Lieffers (1997) observed a significant decrease of net photosynthesis in white spruce seedlings planted on open sites compared to seedlings under canopy during frost periods in spring and fall. Seedlings under shelterwood canopies showed early bud break, reduced terminal bud and seedling mortality, increased capacity for photosynthesis, and improved growth. All of these suggest that the shelterwood system can be used as an alternative to improve the extreme conditions created by clearcutting and promote white spruce regeneration.


The short-term and long-term effects of different densities of aspen on the development of mixed species stands is a fundamental information need which has dramatic implications for management of boreal forests. Aspen and white spruce in a mixture may avoid competition through differential shade tolerance, physical separation of canopies, phenological differences, successional separation, and differences in soil resource utilisation. Aspen may also be able to positively affect the growth of white spruce by improving litter decomposition and nutrient cycling rates, controlling grass and shrub competition, ameliorating environmental extremes (Man and Lieffers 1999b). These positive relationships likely make mixed-species stands more productive than pure stands of the same species (Man and Lieffers 1999a).


Although there are some aspen and white spruce mixture studies such as planting white spruce under aspen canopy Delong (1997) and thinning young aspen stands and plant white spruce (Coopersmith and Hall 1999) in BC, additional empirical trials are needed to quantify spruce and aspen growth at aspen densities between 400 and 2000 stems ha-1 well spaced.


This study would build on the initial underplanting studies of DeLong (1997) and mixedwood studies described by Coopersmith and Hall (1999). In particular, it would quantify the light environments and spruce growth at aspen densities between 400 and 2,000 stems/ha, which have not been addressed by existing studies. Information is still needed to make informed decisions regarding appropriate amounts of aspen and white spruce that should be maintained at various stages of stand development in order to achieve different management objectives.


Objectives:


(1) To establish white spruce regeneration under an aspen overstory.

(2) To determine the relative efficacy of several mechanical and chemical site preparation methods for establishing spruce under aspen stands.

(3) To determine the impacts of aspen densities on survival rate and growth performance of under-planted spruce.

(4) To determine the impacts of aspen densities on herbaceous and shrub communities, and on aspen suckering success.

(5) To determine the optimum aspen densities required to maximise underplanted spruce survival rate and growth and yield.

(6) To select a suitable site preparation method for under-planting spruce in old (mature) aspen stands

  1. To compare several operational vegetation control methods in white spruce plantations

  2. To analyze the cost-benefits of various site preparation techniques on seedling survival and growth rates.



Proposed approach:


  1. For the young aspen stands


For the young aspen stands, because of high density of aspen there is not enough light in the understory for white spruce seedlings to grow. We are planning to manipulate aspen density through thinning in order to increase the understory light level. Thinning the 20-year-old aspen stand will reduce overstory density and site preparation will reduce the vegetation cover on forest floor, both of which can result in an increase of light received on the ground surface and raise soil temperature. However, we have to be careful about the mechanical site preparation because it may stimulate the ingress of grass like blue-joint grass. The following aspen densities: (1) 0 aspen (clearcut) just use what Canfor has already planted or are going to plant this coming summer, (2) 600 stems ha-1 aspen, (3) 1200 stem ha-1, (4) 2500 stems ha-1, (5) 5000 stems ha-1 and (6) a unthinned aspen stand (density should be higher than 5000 stems ha-1) will be created through thinning. White spruce seedlings will be planted (2500 seedlings ha-1) in all the treatments. In the high aspen density treatments (5000 stems ha-1 and unthinned) there may be not enough room for a small excavator to do the mechanical site preparation. In that case we can just raw plant these two treatments. The data will be analysed separately to compare spruce growth and survival under different aspen densities when they are raw planted.


The split-plot design will be used for this trial. The treatment plots will be 8080 m with a 4040 m permanent measuring plot in the centre leaving a 20m wide buffer zone around the measurement plot. The plot will be divided into 2 subplots for the site preparation treatments: raw planting and mechanical mounding. All the treatments will be replicated three times. A total of 18 plots will be established and 11.52 ha of land base needed.


  1. For the old aspen stands


Based on our field observations, understory light level may be adequate for spruce seedlings to grow under old (80-100 years) aspen canopy. However this remains to be decided after we have a field trip. Therefore in the old aspen stands we will plant spruce seedlings (2500 seedlings ha-1) under aspen overstory with different site preparation methods; raw plant, chemical site preparation, and mechanical site preparation. As in the young aspen stands, treatment plots will be 8080 m with a 4040 m permanent measuring plot in the centre leaving a 20m wide buffer zone around the measurement plot. The plots will be divided into two subplots to apply different site preparation methods: (1) raw planting and mechanical site preparation. The treatment will be replicated three times. Area of about 6 ha land base needed for this treatment.


In both young and old aspen stands white spruce will be planted to a density of 2500 seedlings ha-1. All seedlings will be measured for initial height and root collar diameter immediately after planting. At the end of each growing season, survival rate, total height and root collar diameter will be measured. Any damage or animal browsing will be recorded.


  1. Cluster planting (As Richard suggested, I added this part but it is very primitive.)

Cluster planting or strip treatments provide a potentially useful option for managing mixtures of white spruce and aspen where white spruce is a minor stand component (<50% Sw volume at rotation age). Short-term benefits of cluster planting include reduced planting and vegetation management costs, increased survival and faster green-up. Long-term benefits include increased biodiversity of juvenile and mature stands, aesthetically varied landscapes, and increased harvest yields. Cluster planting should be considered under old aspen stands because there may be some gaps larger enough to plant a cluster of 10 white spruce seedlings with a inter-tree distance of 1.0m. Cluster planting arrangements will be designed to produce 15%, 30%, and 45% spruce volumes at rotation. Three hectares of each cluster planting will be established. In total 9 ha of cluster planting will be established. Only one cluster planting (30%) will be monitored as part of the research study design. The other two cluster planting designs will be less intensively monitored, but analyzed and described for extension and demonstration purposes.


  1. Measurement of seedling environments

Photosynthetically active radiation (PAR) will be measured above selected seedlings between 10:00 and 14:00 solar time in the middle of growing season with a ceptometer AccuPAR (We have the equipment).


Daily mean, maximum and minimum air temperature at 0.5 m above the forest floor and 15 cm in the soil will be measured. All the temperature sensors will be suspended in the centre of a horizontal white PVC pipe to shield them from direct radiation. Sensors will be connected to a data logger (CR21, Campbell Scientific Inc. We have extra dataloggers and no need to purchase).


  1. Economic analysis of site preparation (I do not have more expertise in this respect)

This will be done as a directed study by a senior university student (may be not suitable for a graduate student) to collect local information from several site preparation studies in northern B.C., and identifying limiting factors (e.g. excess soil moisture) plant community (herbaceous vs. shrub, vs. hardwood trees), growth responses of white spruce seedlings after 10 or more years.


  1. Vegetation management (I think we may proposing too much)


The study on vegetation management will be conducted on clearcut sites in which Canfor has already planted white spruce using sheep grazing along, herbicide and manual vegetation control. The herbicide treatment will be monitored within the research study comparing underplanting and cluster planting. A replicated but less intensive monitoring design will be used for the sheep grazing and manual vegetation control treatments. This will provide quantitative comparisons between vegetation management treatments.




End Products







Proposed technology transfer:



Duration: 3 years (2000- 2003)



Approximate budget


Graduate student stipends $20,000

Technical assistance $20,000

Travel, accommodations $5,000

Consumable materials and supplies $5,000


Total for 2000/01 $50,000


The same total for 2001/02 and 2002/03 years


The operational costs such as site preparation, thinning, seedlings and planting etc. will be paid through Canfor’s operational budgets.


Approximate budget for the operational costs: (Dennis, please add more details here)

Thinning (14 ha) young aspen stand $14,000

Mechanical site preparation (7 ha) $3,500

Planting (14 ha) $7,000


Total $24,000


References


Coopersmith, D. and Hall E. 1999. Experimental Project 1077- the Siphon Creek mixedwood trial: The use of a simple height-diameter ratio to predict the growth success of planted white spruce seedlings beneath aspen canopies. Research Note #PG17, Prince George Forest Region, BC.


DeLong, C., R.M. Annas, and A.C. Stewart. 1991. Boreal White and Black Spruce Zone. IN: D. Meidinger and J. Pojar, Eds. Ecosystems of British Columbia. Special Report Series, No. 6. B.C. Ministry of Forests, Victoria.


DeLong, C. 1997. Operational considerations for underplanting hardwood stands with white spruce. Research Note #PG11. Prince George Forest Region, BC.


Eis, S. 1981. Effect of vegetative competition on regeneration of white spruce. Can. J. For. Res. 11:1-8.


Hogg, E.H., and Lieffers, V. J. 1991. The impact of Calamagrostis canadensis on soil thermal regimes after logging in northern Alberta. Can. J. For. Res. 21:387-394.


LePage, P. Coates, K. D. 1994. Growth of planted lodgepole pine and hybrid spruce following chemical and manual vegetation control on a frost prone site. Can J. For. Res. 24:208-216.


Lieffers, V. J., MacDonald, S. E., and Hogg, E. H. 1993. Ecology of and control strategies for Calamagrostis canadensis in boreal forest sites. Can. J. For. Res. 23:2070-2077.


Lieffers, V.J. and K.J. Stadt. 1994. Growth of understory Picea glauca, Calamagrostis canadensis, and Epilobium angustifolium in relation to overstory light transmission. Can. J. For. Res. 24: 1193-1198.


Lieffers, V.J., R.B. Macmillan, D. MacPherson, , K. Branter and J.D. Stewart. 1996. Semi-natural and intensive silvicultural systems for the boreal mixedwood forest. Forestry Chronicle 72: 286-292


Man R and Liffers, V. J. 1999a. Are mixtures of aspen and white spruce more productive than single species stands? Forestry Chronicle 75:505-513.


Man R and Liffers, V. J. 1999b. Effects of shelterwood and site preparation on microclimate and establishment of white spruce seedlings in a boreal mixedwood forest. Forestry Chronicle 75:837-844.


Man R and Liffers, V. J. 1997. Seasonal photosynthetic responses to light and temperature on white spruce (Picea glauca) seedlings planted under an aspen (Populus tremuloides) canopy and in the open. Tree Physiol. 17:437-444.


Sutton, R. F. 1984. Plantation establishment in the boreal forest: glyphosate, hexazinone, and mannual weed control. For. Chron. 60:283-287.




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