Modelling Mixing Effects in Forest Stands

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Inventory, Modeling and Remote Sensing".

Deadline for manuscript submissions: closed (29 February 2020) | Viewed by 20942

Special Issue Editor


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Guest Editor
Department of Forest and Soil Sciences, Institute of Forest Growth, BOKU University of Natural Resources and Life Sciences, Peter-Jordan-Straße 82, 1190 Vienna, Austria.
Interests: growth and yield; forest inventory; growth modelling; mixed forests; grwoth efficiency; forest structure

Special Issue Information

Dear Colleagues,

Complementarity, i.e., the mixing effects in mixed species forests are increasingly being investigated. Not only growth, but also tree form, foliar distribution, carbon allocation, mortality, resilience, resistance and recovery, crown features and foliar distribution exhibit mixing effects. They are found to depend on species traits, species proportions, stand characteristics like stand density and developmental stage, as well as site quality characteristics.

Growth models of different types and different complexities, whole stand models, distance-dependent and distance-independent individual tree models, statistical and mechanistic models are frequently used to evaluate and study the mixing effects. They have to go beyond case studies and therefore it is interesting to see if, and if yes then how complementarity can be modelled or could be considered in models. Therefore, this Special Issue will concentrate on the possibilities of generalizing relationships that finally lead to complementarity effects on any features of mixed species forest stands.

Prof. Dr. Em. Hubert Sterba
Guest Editor

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Keywords

  • mixed forests
  • growth models
  • complementarity
  • mixing effects
  • species traits
  • competition
  • plasticity

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Published Papers (6 papers)

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Research

21 pages, 5883 KiB  
Article
Assessing Differences in Competitive Effects Among Tree Species in Central British Columbia, Canada
by Stella Britwum Acquah and Peter L. Marshall
Forests 2020, 11(2), 167; https://doi.org/10.3390/f11020167 - 1 Feb 2020
Cited by 5 | Viewed by 2542
Abstract
Research Highlights: We investigated the competitive interactions among three tree species (interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), interior spruce (Picea glauca [Moench] Voss × Picea engelmannii Engelm.), and lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Englem.)) [...] Read more.
Research Highlights: We investigated the competitive interactions among three tree species (interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), interior spruce (Picea glauca [Moench] Voss × Picea engelmannii Engelm.), and lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Englem.)) in multi-aged stands in central British Columbia, Canada. Background and Objectives: Understanding competitive interactions among tree species in mixed-species stands is fundamental to supporting silvicultural decision-making in such stands. Using the periodic annual basal area increment for single trees as our dependent variable, we investigated whether neighboring trees competed with subject trees independently of species identity. We also examined the differences in single-tree basal area growth among the three conifer species over time under different levels of competition. Materials and Methods: We developed several spatially explicit, single-tree basal area growth models for interior Douglas-fir, interior spruce, and lodgepole pine using data from 16 plots in two blocks of a long-term study (five measurements over a 21-year period) on the response to pre-commercial thinning. We compared these equations to assess whether intraspecific or interspecific competition predominated. We also examined the differences in basal area growth among the three conifer species over time under different levels of competition. Results: We found asymmetrical relationships between the conifer trees and their neighbors for all species, indicating that the main driver limiting growth in these stands is aboveground competition for light. There was evidence of higher intraspecific competition for small (<10.0 cm DBH) interior Douglas-fir in one block. However, there was no general pattern among larger subject trees with respect to the identity of neighborhood competitive effects and the equivalence of neighbors. We observed a higher level of basal area growth over time for interior Douglas-fir than for lodgepole pine and interior spruce, irrespective of the competition intensity and, not surprisingly, the growth rate declined with increasing competition levels for the three species. Conclusions: Our results provide an understanding of how interior Douglas-fir stands will develop over time and information on species interactions that could help forest managers explore different silvicultural options and their effects on individual tree growth in these complex stands. Full article
(This article belongs to the Special Issue Modelling Mixing Effects in Forest Stands)
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17 pages, 1942 KiB  
Article
Interregional Crown Width Models for Individual Trees Growing in Pure and Mixed Stands in Austria
by Rafael Buchacher and Thomas Ledermann
Forests 2020, 11(1), 114; https://doi.org/10.3390/f11010114 - 16 Jan 2020
Cited by 19 | Viewed by 3682
Abstract
Crown width is a functional trait that is commonly used to improve the estimation of above-ground biomass of forests and is often included as a predictor variable in forest growth models. Most of the existing crown width models reflect the relationship between crown [...] Read more.
Crown width is a functional trait that is commonly used to improve the estimation of above-ground biomass of forests and is often included as a predictor variable in forest growth models. Most of the existing crown width models reflect the relationship between crown width, tree size and competition variables, but do not consider the effect of species mixture. In this study, we developed crown width models for individual-tree of the major tree species growing in Austria. Because these models should be applicable for mixed and pure stands and should also take into account the characteristics of different sites, the relationship between crown width, site variables and species composition was investigated. For that purpose, we used data from a sub-sample of the Austrian National Forest Inventory, which comprises crown width measurements of about 8900 trees from 1508 sample plots. Because of the hierarchical structure of the data set (i.e., trees nested within the plot) which destroys the independencies between observations, linear mixed-effects models were used. The species composition of the stand was included via the species-specific relative proportions of basal area. To describe the interregional variability of crown width, dummy variables were introduced, which account for region-specific differences. Site characteristics were incorporated through the altitude, slope and aspect of the site. For Norway spruce, silver fir, Scots pine, European larch, European beech, oak species and ash/maple species it was possible to develop crown width models, which reflect the effects of site characteristics and species composition of the stand. The crown widths of shade-tolerant species reacted mainly positively to admixture, whereas light-demanding species reacted with decreasing crown widths. Coniferous species were not as strongly affected by mixture as broadleaf species. Full article
(This article belongs to the Special Issue Modelling Mixing Effects in Forest Stands)
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33 pages, 5421 KiB  
Article
The Effect of Tree Crown Allometry on Community Dynamics in Mixed-Species Stands versus Monocultures. A Review and Perspectives for Modeling and Silvicultural Regulation
by Hans Pretzsch
Forests 2019, 10(9), 810; https://doi.org/10.3390/f10090810 - 17 Sep 2019
Cited by 54 | Viewed by 5332
Abstract
Many recent studies have shown that the structure, density, and productivity of mixed-species stands can differ from the weighted mean of monospecific stands of the respective species. The tree and stand properties emerging by inter-specific neighborhood should be considered in models for understanding [...] Read more.
Many recent studies have shown that the structure, density, and productivity of mixed-species stands can differ from the weighted mean of monospecific stands of the respective species. The tree and stand properties emerging by inter-specific neighborhood should be considered in models for understanding and practical management. A promising approach for this is a more realistic representation of the individual tree allometry in models and management concepts, as tree allometry determines many structural and functional aspects at the tree and stand level. Therefore, this paper is focused on the crown allometry in mixed and mono-specific stands. Firstly, we review species-specific differences in the crown allometry in monospecific stands. Secondly, we show how species-specific differences and complementarities in crown allometry can emerge in mixed-species stands. Thirdly, the consequences of allometric complementarity for the canopy packing density will be analyzed. Fourthly, we trace the crown allometry from the tree level to the stand density and show the relevance for the self-thinning in mixed versus monospecific stands. Fifth, the consequence of the findings for modeling and regulating tree and stand growth will be discussed. The review deals mainly with widespread even-aged, mono-layered stands, but the main results apply for more heterogeneous stands analogously. Full article
(This article belongs to the Special Issue Modelling Mixing Effects in Forest Stands)
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16 pages, 3707 KiB  
Article
Vertical Distribution of Leaf Area of European Larch (Larix decidua Mill.) and Norway Spruce (Picea abies (L.) Karst.) in Pure and Mixed Stands
by Hubert Sterba, Gerald Dirnberger and Tim Ritter
Forests 2019, 10(7), 570; https://doi.org/10.3390/f10070570 - 9 Jul 2019
Cited by 4 | Viewed by 3326
Abstract
The growth effects of mixtures are generally assumed to be a result of canopy structure and crown plasticity. Thus, the distribution of leaf area at tree and stand level helps to explain these mixing effects. Therefore, we investigated the leaf area distribution in [...] Read more.
The growth effects of mixtures are generally assumed to be a result of canopy structure and crown plasticity. Thus, the distribution of leaf area at tree and stand level helps to explain these mixing effects. Therefore, we investigated the leaf area distribution in 12 stands with a continuum of proportions of European larch (Larix decidua Mill.) and Norway spruce (Picea abies (L.) Karst.). The stands were between 40 and 170 years old and located in the northern part of the Eastern Intermediate Alps in Austria at elevations between 900 and 1300 m asl A total of 200 sample trees were felled and the leaf area distribution within their crowns was evaluated. Fitting beta distributions to the individual empirical leaf area distributions, the parameters of the beta distributions were shown to depend on the leaf area of the individual trees and, for spruce, on the proportion of spruce in the stands. With the equations determined, the leaf area distribution of all trees in the stand, and thus its distribution in the stands, was calculated by species and in 2 m height classes. For the individual trees, we found that the leaf area distribution of larch is more symmetric, and its peak is located higher in the crown than it is the case for spruce. Furthermore, the leaf area distribution of both species becomes more peaked and skewed when the leaf area of the trees increases. The mixture only influences the leaf area distribution of spruce in such a way that the higher the spruce proportion of the stand, the higher the leaf area is located within the crown. At the stand level, a strong relationship was found between the proportion of spruce and the distance between the peaks of the leaf area distributions of larch and spruce. Full article
(This article belongs to the Special Issue Modelling Mixing Effects in Forest Stands)
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21 pages, 2874 KiB  
Article
Productivity Estimations for Monospecific and Mixed Pine Forests along the Iberian Peninsula Aridity Gradient
by Ana Aguirre, Miren del Río and Sonia Condés
Forests 2019, 10(5), 430; https://doi.org/10.3390/f10050430 - 18 May 2019
Cited by 16 | Viewed by 2907
Abstract
National Forest Inventories (NFIs) are the primary source of information to fulfill international requirements, such as growing stock volume. However, NFI cycles may be “out of phase” in terms of the information required, so prediction techniques are needed. To disentangle the effects of [...] Read more.
National Forest Inventories (NFIs) are the primary source of information to fulfill international requirements, such as growing stock volume. However, NFI cycles may be “out of phase” in terms of the information required, so prediction techniques are needed. To disentangle the effects of climate and competition on stand productivity and to estimate the volume of stocks at national scale, it is important to recognize that growth and competition are species-specific and vary along climatic gradients. In this study, we estimate the productivity of five pine species (Pinus sylvestris, Pinus pinea, Pinus halepensis, Pinus nigra and Pinus pinaster), growing in monospecific stands or in mixtures along an aridity gradient in the Iberian Peninsula, based on Spanish NFI data. We study the stand volume growth efficiency (VGE), since it allows the comparison of volume growth in monospecific and mixed stands. The results reveal the importance of considering the aridity when assessing VGE. Moreover, it was found that, in general, admixture among pine species leads to modifications in the VGE, which can vary from negative to positive effects depending on species composition, and that this is always influenced by the aridity. Finally, we provide simple growth efficiency models for the studied pines species which are valid for both monospecific and mixed stands along the aridity gradient of the Iberian Peninsula. Full article
(This article belongs to the Special Issue Modelling Mixing Effects in Forest Stands)
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12 pages, 2286 KiB  
Article
Mortality of Different Populus Genotypes in Recently Established Mixed Short Rotation Coppice with Robinia pseudoacacia L.
by Jessica Rebola-Lichtenberg, Peter Schall, Peter Annighöfer, Christian Ammer, Ludger Leinemann, Andrea Polle and Dejuan Euring
Forests 2019, 10(5), 410; https://doi.org/10.3390/f10050410 - 12 May 2019
Cited by 8 | Viewed by 2612
Abstract
Short rotation coppices play an increasing role in providing wooden biomass for energy. Mixing fast-growing tree species in short rotation coppices may result in complementary effects and increased yield. The aim of this study was to analyze the effect on mortality of eight [...] Read more.
Short rotation coppices play an increasing role in providing wooden biomass for energy. Mixing fast-growing tree species in short rotation coppices may result in complementary effects and increased yield. The aim of this study was to analyze the effect on mortality of eight different poplar genotypes (Populus sp.) in mixed short rotation coppices with three different provenances of the N-fixing tree species black locust (Robinia pseudoacacia L.). Pure and mixed stands were established at two sites of contrasting fertility. Survival of poplar was assessed for each tree two times a year, for a period of three years. In the first two years, high variation in mortality was observed between the genotypes, but no significant differences between pure and mixed stands were identified. However, three years after planting, higher mortality rates were observed in the mixtures across all poplar genotypes in comparison to pure stands. The expected advantage on growth of combining an N-fixing tree with an N-demanding tree species, such as poplar, was overshadowed by the Robinia’s dominance and competitiveness. Full article
(This article belongs to the Special Issue Modelling Mixing Effects in Forest Stands)
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