Forest Investment Account (FIA) - Forest Science Program
FIA Project M075001

    Density and Distribution of Advance Regeneration in the MS Biogeoclimatic Zone in Relation to Site Moisture and Overstorey Density
Project lead: Nigh, Gordon
Contributing Authors: Nigh, Gordon D.; Parish, Roberta; Antos, Joseph A.
Imprint: Victoria, BC : BC Ministry of Forests; University of Victoria, 2007
Subject: Forest Investment Account (FIA), Dendroctonus Ponderosae, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Forest managers must devise regeneration strategies for post-MPB attacked stands with very little information to guide their decisions. The MPB infestation is so extensive that there will be little hope of treating all stands. However, some stands will probably not require treatment because they will successfully regenerate in a reasonable timeframe without any intervention. Therefore, the question becomes 'Which stands do we treat (and how do we treat them), and which stands can be left to regenerate on their own?' Many factors have to be taken into consideration, such as access, but a key factor is whether the stand will successfully regenerate on its own, through seeding in or from advance regeneration. This project addresses the question of which stands can be left alone to regenerate by advance regeneration. To answer this question, we are proposing to develop equations that predict the amount and spatial distribution of advance regeneration and to relate this to the potential for successful development of stands following the MPB outbreak. Extensive stands of mature lodgepole pine occupy the plateaus in the Montane Spruce (MS) zone in the Merritt TSA. These types of stands are extremely susceptible to MPB and existing models predict that massive mortality will occur over the next few years. Some stands contain considerable advance regeneration of spruce, subalpine fir, and Douglas-fir, but specific information about advance regeneration is lacking. In the absence of subsequent fire, advance regeneration has the potential to form the new canopy after a MPB outbreak under natural conditions (Gara et al. 1985; Stuart et al. 1989). Advance regeneration is successful at forming new stands following mortality from bark beetles in a variety of situations. For example, in the Southern Rocky Mountains, new stands developed from advance regeneration after most of the canopy was killed by spruce bark beetles (Veblen et al. 1991). In BC, advance regeneration and the growth of new seedlings rapidly filled gaps created in spruce-fir forests by the spruce bark beetle (Parish et al. 1999). Surviving understory and subcanopy trees rapidly increased in growth such that stand productivity was not greatly reduced after outbreaks of MPB in lodgepole pine forests of Northwestern Wyoming (Romme et al. 1986). In some dry ecosystems in Colorado (Moir 1969) and Oregon (Stuart et al. 1989), lodgepole pine is self perpetuating after repeat MPB attacks. These ecosystems usually have a high proportion of non serotinous lodgepole pine (Muir and Lotan 1985; Stuart et al. 1989). Many factors affect the development of advance regeneration in the sub canopy; in particular light and site moisture regimes have a strong influence on viability and growth (e.g., Pacala et al. 1994; Kobe and Coates 1996; Wright et al. 1998). Overstory density is a key factor in the understory light regime and proximity of regeneration to mature trees affects survival and growth success (Gagnon et al. 2003). Site moisture may interact with overstory density. Site moisture is an indicator of productivity and we hypothesize that both overstory and understory vegetation, including advance regeneration, will be more abundant on more productive sites. However, some understory species can persist better under the more open canopies on dry sites (Chen et al. 1996; Williams et al. 1999) so that there may be trade-off between abundance and longevity. Dry sites may also favour survival of lodgepole pine and Douglas-fir regeneration over that of subalpine fir. Thus, interactions may impact not only the survival and growth of advance regeneration but also the species composition. Determining the relationship of site moisture and overstory density to the density and spatial distribution of advance regeneration in MPB-attacked stands will assist forest managers to predict whether the advance regeneration will be sufficient to stock a stand, or whether some remedial treatment, such as fill-planting, will be required to bring a post-MPB stand up to acceptable stocking standards. It will also give planners a tool for generating stand establishment scenarios, which can then be used as starting conditions for growth and yield models in timber supply analyses. We will focus our research in the Merritt TSA, where lodgepole pine occupies two-thirds of the productive landbase and the MPB outbreak is just becoming established. Our research will be conducted in the MS zone, where information is inadequate for assessing whether advance regeneration has the potential to form new stands of economically acceptable characteristics within an acceptable timeframe. To determine how this potential relates to pre-MPB stand characteristics, we will locate 24 stands undergoing MPB-attack. The selected stands will cover a range of moisture regimes. Forty quadrats will be established in each stand and various tree measurements will be taken. The spatial pattern of the advance regeneration will be characterized using quadrat-based spatial statistics. We will relate the density and spatial distribution of the advance regeneration to the overstory density and the site moisture. This will provide forest managers with a decision support tool to help them determine whether a stand can be left to its own devices, requires fill planting, or requires rehabilitation.

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Related projects:  FSP_M086001


Executive Summary (24Kb)
Report (84Kb)
Brochure (28Kb)

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Updated August 16, 2010 

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