Modelling dead wood in Norway spruce stands subject to different mangement regimes
Department of Entomology, Swedish University of Agricultural Sciences, P.O. Box 7044, SE-750 07 Uppsala, Sweden Forest Ecology and Management
(Impact Factor: 2.66).
09/2003; 182(1):13-29. DOI: 10.1016/S0378-1127(03)00027-6
Strategies for preserving biodiversity in boreal forests should include the maintenance of coarse woody debris (CWD) because this substrate is a key feature for the preservation of many threatened species. Computer simulation programs are useful tools for predicting the amount of CWD that will arise if certain management practices are applied in the long term. We have constructed and used a simulation program based on stochastic equations, which aims at predicting the amount of CWD in homogenous stands of Norway spruce in central Scandinavia. Because the rate of tree mortality is a critical factor in such simulations, we present such data derived from spruce-dominated forests surveyed in the Swedish National Forest Inventory.A comparison between simulation outcomes and field data shows that the average quantity of CWD in today’s managed forest is possible to predict using the simulation model. If the forest is managed according to the Forest Certification Standard, the amount of CWD (diameter larger than 10 cm) will be almost three times higher as the amount in today’s managed forests. The amount of CWD was found to be highest in old stands and immediately after cutting. In stands of an intermediate age the amount of CWD was low, especially CWD in early decay stages and of larger sizes. High productivity and long rotation time tended, on average, to increase the amount of CWD in stands. Among the management practices recommended in the new biodiversity-oriented forestry, retention of small areas with living trees is the most efficient way to increase the average amount and continuous occurrence of CWD within a stand, at least if the retained areas are as productive as the main part of the stands.
Available from: Jürgen Bauhus
- "So far this knowledge is incomplete and mainly based on expert opinions (Meyer et al. 2003; Rock et al. 2008; Zell et al. 2009). In addition, information on residence times of CWD in different decay classes would be very helpful to forecast its dynamics and to calculate the input and output of different decay stages in order to conserve specific habitats of dead wood dependent species (Kruys et al. 2002; Ranius et al. 2003). "
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ABSTRACT: Background: Coarse woody debris (CWD) is an important element of forest structure that needs to be considered when managing forests for biodiversity, carbon storage or bioenergy. To manage it effectively, dynamics of CWD decomposition should be known. Methods: Using a chronosequence approach, we assessed the decomposition rates of downed CWD of Fagus sylvatica, Picea abies and Pinus sylvestris, which was sampled from three different years of tree fall and three different initial diameter classes (>10 – ≤ 20 cm, >20 – ≤40 cm, >40 cm). Samples originating from wind throws in 1999 were collected along a temperature and precipitation gradient. Based on the decay class and associated wood densities, log volumes were converted into CWD mass and C content. Log fragmentation was assessed over one year for log segments of intermediate diameters (>20 – 40 cm) after 8 and 18 years of decomposition.
Results: Significantly higher decomposition constants (k) were found in logs of F. sylvatica (0.054 year−1) than in P. abies (0.033 year−1) and P. sylvestris (0.032 year−1). However, mass loss of P. sylvestris occurred mainly in sapwood and hence k for the whole wood may be overestimated. Decomposition rates generally decreased with increasing log diameter class except for smaller dimensions in P. abies. About 74 % of the variation in mass remaining could be explained by decomposition time (27 %), tree species (11 %), diameter (17 %), the interactive effects between tree species and diameter (4 %) as well as between decomposition time and tree species (3 %) and a random factor (site and tree; 9.5 %), whereas temperature explained only 2 %. Wood fragmentation may play a more important role than previously thought. Here, between 14 % and 30 % of the decomposition rates (for the first 18 years) were attributable to this process. Carbon (C) density (mgC · cm−3), which was initially highest for F. sylvatica, followed by P. sylvestris and P. abies, decreased with increasing decay stage to similar values for all species.
Conclusions: The apparent lack of climate effects on decomposition of logs in the field indicates that regional decomposition models for CWD may be developed on the basis of information on decomposition time, tree speciesand dimension only. These can then be used to predict C dynamics in CWD as input for C accounting models and for habitat management.
Available from: S. J. Köhler
- "). ProdMod is a free software programme designed to simulate forest growth at five years interval, using empirical growth functions developed by Ekö (1985) and based on data from the Swedish National Forest Inventory. ProdMod has frequently been used as a tool for analysing forest management practices and/or climate change effects on dead wood accumulation , forest productivity, carbon sequestration and runoff quality (Blennow et al., 2010; Ranius et al., 2003; Thor et al., 2006; Weslien et al., 2009). Site index (SI) is a key parameter in ProdMod as it predicts future growth with high values indicating high potential production. "
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ABSTRACT: Forest biofuel is a main provider of energy in Sweden and the market is expected to grow even further in the future. Removal of logging residues via harvest can lead to short-term acidification but the long-term effects are largely unknown. The objectives of this study were to 1) model the long-term effect of whole-tree harvest (WTH) on soil and stream water acidity and 2) perform sensitivity analyses by varying the amounts of logging residues, calcium (Ca2 +) concentrations in tree biomass and site productivity in nine alternate scenarios. Data from three Swedish forested catchments and the Model of Acidification of Groundwater in Catchments (MAGIC) were used to simulate changes in forest soil exchangeable Ca2 + pools and stream water acid neutralizing capacity (ANC) at Gammtratten, Kindla and Aneboda. Large depletions in soil Ca2 + supply and a reversal of the positive trend in stream ANC were predicted for all three sites after WTH. However, the magnitude of impact on stream ANC varied depending on site and the concentration of mobile strong acid anions. Contrary to common beliefs, the largest decrease in modelled ANC was observed at the well-buffered site Gammtratten. The effects at Kindla and Aneboda were much more limited and not large enough to offset the general recovery from acidification. Varying the tree biomass Ca2 + concentrations exerted the largest impact on modelled outcome. Site productivity was the second most important variable whereas changing biomass amounts left on site only marginally affected the results. The outcome from the sensitivity analyses pointed in the same direction of change as in the base scenario, except for Kindla where soil Ca2 + pools were predicted to be replenished under a given set of input data. The reliability of modelled outcome would increase by using site-specific Ca2 + concentrations in tree biomass and field determined identification of site productivity.
- "Recently, applicable models have been developed for representing mortality of trees in natural and seminatural boreal Spruce forest (Peltoniemi and Mäkipää, 2011), for tree fall (Aakala, 2011; Mäkinen et al., 2006), and dead wood decomposition (Kruys et al., 2002; Ranius et al., 2003; Aakala, 2011; Mäkinen et al., 2006), which are useful for these purposes, and may be used to extend applicability of the stand simulation models from conventionally managed to more natural stands. Acknowledging the importance of dead wood for sustainable forest management, some studies have already investigated effective ways of managing dead-wood stocks in boreal forests of Northern Europe (Ranius et al., 2003; Tikkanen et al., 2012), and in North America where focus has been on fire return interval (Brown et al., 2003; Tinker and Knight, 2001). Some of the earlier model studies have analyzed sustainable harvest scenarios by including total number of polypore species as a criteria (as explained by the total volume of dead wood)(Hynynen et al., 2005), or by making cost-effective selection of conservation areas including measured polypore diversity of stands as one of the criteria (Juutinen et al., 2004). "
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ABSTRACT: Decline of dead wood in managed boreal forests has variously affected polypore species that use it as their substrate, some now being listed as threatened while some are still thriving. Management of polypore diversity requires species-specific information about their occurrence probabilities, which partially depend on stand dead wood availability and other properties. We implemented an ensemble of polypore habitat models to simulations of stand and dead wood availability estimated with a decomposition model we fitted to data. We asked how management of a boreal Norway spruce stand influences the dead wood availability and polypore occurrence probabilities and their diversity. Simulations of multiple polypore species with stand management scenarios provided insight to dead wood dynamics and polypore species management. In a managed stand, diversity thrived after final harvesting, but declined to low level by mid-rotation. Harvest residues and stumps, although low quality substrate for many species, were important for diversity in young managed stand due to their high quantities. High mixtures of naturalness in stand management were required to elevate diversity of managed spruce stands from the mid-rotation lows to levels in natural-like stands. Our study suggests that dead-wood supply of managed stands could be optimised to lift lowest species expectations towards levels in natural-like forests, but it seems that reaching these levels requires deadwood quantities much higher than provided by conventional management. Management of stand diversity can presumably be facilitated with wise landscape planning but more research is needed in order to incorporate polypores to spatio-temporal management simulation context.
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