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22 pages, 2734 KiB

Open AccessArticle

Species Mixing Effects on Height–Diameter and Basal Area Increment Models for Scots Pine and Maritime Pine

by José Riofrío, Miren del Río, Douglas A. Maguire and Felipe Bravo

Forests 2019, 10(3), 249; https://doi.org/10.3390/f10030249 - 12 Mar 2019

Cited by 25 | Viewed by 4023

Models that incorporate known species-mixing effects on tree growth are essential tools to properly design silvicultural guidelines for mixed-species stands. Here, we developed generalized height–diameter (h-d) and basal area growth models for mixed stands of two main forest species in Spain: [...] Read more.

Models that incorporate known species-mixing effects on tree growth are essential tools to properly design silvicultural guidelines for mixed-species stands. Here, we developed generalized height–diameter (h-d) and basal area growth models for mixed stands of two main forest species in Spain: Scots pine (Pinus sylvestris L.) and Maritime pine (Pinus pinaster Ait.). Mixed-effects models were fitted from plot measurement and tree rings data from 726 Scots pine and 693 Maritime pine trees from mixed and pure stands in the Northern Iberian Range in Spain, with the primary objective of representing interactions between the species where they are interspersed in mixtures of varying proportions. An independent dataset was used to test the performance of the h-d models against models previously fitted for monospecific stands of both species. Basal area increment models were evaluated using a 10-fold block cross-validation procedure. We found that species mixing had contrasting effects on the species in both models. In h-d models, the species-mixing proportion determined the effect of species interactions. Basal area growth models showed that interspecific competition was influential only for Maritime pine; however, these effects differed depending on the mode of competition. For Scots pine, tree growth was not restricted by interspecies competition. The combination of mixed-effect models and the inclusion of parameters expressing species-mixing enhanced estimates of tree height and basal area growth compared with the available models previously developed for pure stands. Although the species-mixing effects were successfully represented in the fitted models, additional model components for accurately simulating the stand dynamics of mixtures with Scots pine and Maritime pine and other species mixtures require similar model refinements. Upon the completion of analyses required for these model refinements, the degree of improvement in simulating growth in species mixtures, including the effects of different management options, can be evaluated. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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21 pages, 19762 KiB

Open AccessArticle

Species Mixing Effects on Forest Productivity: A Case Study at Stand-, Species- and Tree-Level in the Netherlands

by Huicui Lu, Godefridus M. J. Mohren, Miren Del Río, Mart-Jan Schelhaas, Meike Bouwman and Frank J. Sterck

Forests 2018, 9(11), 713; https://doi.org/10.3390/f9110713 - 17 Nov 2018

Cited by 11 | Viewed by 5904

Abstract

Many monoculture forests have been converted to mixed-species forests in Europe over the last decades. The main reasons for this conversion were probably to increase productivity, including timber production, and enhance other ecosystem services, such as conservation of biodiversity and other nature values. [...] Read more.

Many monoculture forests have been converted to mixed-species forests in Europe over the last decades. The main reasons for this conversion were probably to increase productivity, including timber production, and enhance other ecosystem services, such as conservation of biodiversity and other nature values. This study was done by synthesizing results from studies carried out in Dutch mixed forests compared with monoculture stands and evaluating them in the perspective of the current theory. Then we explored possible mechanisms of higher productivity in mixed stands, in relation to the combination of species, stand age and soil fertility, and discussed possible consequences of forest management. The study covered five two-species mixtures and their corresponding monoculture stands from using long-term permanent forest plots over multiple decades as well as two inventories (around 2003 and 2013) across the entire Netherlands. These forest plot data were used together with empirical models at total stand level, species level and tree level. Overyielding in Douglas-fir–beech and pine–oak mixtures was maintained over time, probably owing to the intensive thinning and was achieved on the poorer soils. However, this overyielding was not always driven by fast-growing light-demanding species. On individual tree level, intra-specific competition was not necessarily stronger than inter-specific competition and this competitive reduction was less seen at lower soil fertility and dependent on species mixtures. Moreover, size-asymmetric competition for light was more associated with tree basal area growth than size-symmetric competition for soil resources. Overall, this study suggests a substantial potential of species mixing for increasing productivity and implies developing forest management strategies to convert monospecific forests to mixed-species forests that consider the complementarity in resource acquisition of tree species. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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20 pages, 3502 KiB

Open AccessFeature PaperArticle

Effect of Species Complementarity on Financial Return in Mixed Stands of European Beech and Scots Pine in Northern Spain

by Fernando García-Robredo

Forests 2018, 9(9), 559; https://doi.org/10.3390/f9090559 - 12 Sep 2018

Cited by 11 | Viewed by 3527

Abstract

The research on mixed-species forestry has rapidly increased in recent decades because there is a growing interest in these types of stands for environmental reasons. Their positive influence on ecosystem biodiversity, stability and resilience, as well as their role in the new challenge [...] Read more.

The research on mixed-species forestry has rapidly increased in recent decades because there is a growing interest in these types of stands for environmental reasons. Their positive influence on ecosystem biodiversity, stability and resilience, as well as their role in the new challenge brought up by the adaptation to global change, have been the object of many research works. However, the economic implications of mixed-species forest management have not deserved the same attention. The objective of this work is to study the effect of species interactions on productivity, and to economically assess this effect. This research is focused on the analysis of financial return and risk in even aged mixed stands of Pinus sylvestris and Fagus sylvatica in Northern Spain. Growth and yield projections for monospecific and mixed stands of Scots pine and European beech were made by means of a previous model developed from a set of the Spanish National Forest Inventory plots in the region of Navarre. Data from yield tables for both species were used. The effect of species proportion on total stand yield was assessed and transgressive overyielding was found for some mixing ratios. A data series on average stumpage price for both species in Spain over a 29-year period was compiled and the joint probability distribution of price data was used to generate 500 price scenarios. Different management alternatives based on species proportion and rotation age were considered and evaluated in terms of profitability and risk. Some management recommendations can be derived from the results obtained, which point at an optimum mixing ratio from 30% to 40% Scots pine and 70% to 60% European beech. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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14 pages, 2772 KiB

Open AccessArticle

Ecological Interactions between Cork Oak (Quercus suber L.) and Stone Pine (Pinus pinea L.): Results from a Pot Experiment

by Alexandra C. Correia, António Galla, Alexandra Nunes and João S. Pereira

Forests 2018, 9(9), 534; https://doi.org/10.3390/f9090534 - 01 Sep 2018

Cited by 5 | Viewed by 5226

Abstract

Portuguese cork oak (Quercus suber L.) extended mortality and lack of regeneration have been the drivers of important changes in the traditional cork oak woodlands (savanna-like) montado. The decrease in tree cover fosters the mixture with stone pine (Pinus pinea [...] Read more.

Portuguese cork oak (Quercus suber L.) extended mortality and lack of regeneration have been the drivers of important changes in the traditional cork oak woodlands (savanna-like) montado. The decrease in tree cover fosters the mixture with stone pine (Pinus pinea L.) for pine-nut production providing shelter for oak regeneration. The use of nurse species, namely pines, to help Quercus spp. regeneration is known, but whether cork oak could be favoured by the mixture with stone pine remains a question. A pot experiment with cork oak (Qs) and stone pine (Pp) growing in inter-(Qs×Pp) and intraspecific mixtures (Qs×Qs, Pp×Pp) combinations and in monocultures, was installed in a greenhouse in Lisbon, Portugal. Morphological measurements of above- and belowground biomass components were carried out in 3 harvesting campaigns at 4, 8 and 11 months. Leaf nitrogen content and mycorrhizal symbiotic formations were quantified. During the seedling stage and under comfort water and nutrient conditions, the root growth and morphology of Qs and Pp showed contrasting patterns, suggesting complementary soil exploitation interactions in interspecific mixtures and potential competition in intraspecific mixtures. The mixture of Qs with Pp seems to be advantageous in the first stages of plant growth as Pp develop abundant mycorrhizae symbiosis formations which elicit mycorrhization of Qs plants coexisting in the same pot. This study suggests that stone pine can potentially help in establishing cork oak as seedlings, possibly facilitating nutrient uptake through mycorrhizae. However, complementary field studies are needed. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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17 pages, 3162 KiB

Open AccessArticle

Estimation and Uncertainty of the Mixing Effects on Scots Pine—European Beech Productivity from National Forest Inventories Data

by Sonia Condés, Hubert Sterba, Ana Aguirre, Kamil Bielak, Andrés Bravo-Oviedo, Lluís Coll, Maciej Pach, Hans Pretzsch, Patrick Vallet and Miren Del Río

Forests 2018, 9(9), 518; https://doi.org/10.3390/f9090518 - 28 Aug 2018

Cited by 15 | Viewed by 4265

Abstract

An increasing amount of research is focusing on comparing productivity in monospecific versus mixed stands, although it is difficult to reach a general consensus as mixing effects differ both in sign (over-yielding or under-yielding) and magnitude depending on species composition as well as [...] Read more.

An increasing amount of research is focusing on comparing productivity in monospecific versus mixed stands, although it is difficult to reach a general consensus as mixing effects differ both in sign (over-yielding or under-yielding) and magnitude depending on species composition as well as on site and stand conditions. While long-term experimental plots provide the best option for disentangling the mixing effects, these datasets are not available for all the existing mixtures nor do they cover large gradients of site factors. The objective of this study was to evaluate the effects and uncertainties of tree species mixing on the productivity of Scots pine–European beech stands along the gradient of site conditions in Europe, using models developed from National and Regional Forest Inventory data. We found a positive effect of pine on beech basal area growth, which was slightly greater for the more humid sites. In contrast, beech negatively affected pine basal area growth, although the effects switched to positive in the more humid sites. However, the uncertainty analysis revealed that the effect on pine at mid- and more humid sites was not-significant. Our results agree with studies developed from a European transect of temporal triplets in the same pine–beech mixtures, confirming the suitability of these datasets and methodology for evaluating mixing effects at large scale. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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18 pages, 2491 KiB

Open AccessArticle

Over- and Underyielding in Time and Space in Experiments with Mixed Stands of Scots Pine and Norway Spruce

by Lars Drössler, Eric Agestam, Kamil Bielak, Małgorzata Dudzinska, Julia Koricheva, Mateusz Liziniewicz, Magnus Löf, Bill Mason, Hans Pretzsch, Sauli Valkonen and Klaas Wellhausen

Forests 2018, 9(8), 495; https://doi.org/10.3390/f9080495 - 13 Aug 2018

Cited by 23 | Viewed by 4952

Abstract

Pine-spruce forests are one of the commonest mixed forest types in Europe and both tree species are very important for wood supply. This study summarized nine European studies with Scots pine and Norway spruce where a mixed-species stand and both monocultures were located [...] Read more.

Pine-spruce forests are one of the commonest mixed forest types in Europe and both tree species are very important for wood supply. This study summarized nine European studies with Scots pine and Norway spruce where a mixed-species stand and both monocultures were located in an experimental set-up. Overyielding (where growth of a mixed stand was greater than the average of both monocultures) was relatively common and often ranged between 0% and 30%, but could also be negative at individual study sites. Each individual site demonstrated consistent patterns of the mixing effect over different measurement periods. Transgressive overyielding (where the mixed-species stand was more productive than either of the monocultures) was found at three study sites, while a monoculture was more productive on the other sites. Large variation between study sites indicated that the existing experiments do not fully represent the extensive region where this mixed pine-spruce forest can occur. Pooled increment data displayed a negative influence of latitude and stand age on the mixing effect of those tree species in forests younger than 70 years. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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17 pages, 7167 KiB

Open AccessArticle

The Contribution of Forest Structure to Complementarity in Mixed Stands of Norway Spruce (Picea abies L. Karst) and European Larch (Larix decidua Mill.)

by Hubert Sterba, Gerald Dirnberger and Tim Ritter

Forests 2018, 9(7), 410; https://doi.org/10.3390/f9070410 - 07 Jul 2018

Cited by 4 | Viewed by 3216

Abstract

An increasing number of investigations into mixed forest stands shows clear interactions between complementarity and stand and site characteristics. One of the least-investigated mixture types are mixed stands of Norway spruce and European larch. We investigated pure and mixed stands of these species [...] Read more.

An increasing number of investigations into mixed forest stands shows clear interactions between complementarity and stand and site characteristics. One of the least-investigated mixture types are mixed stands of Norway spruce and European larch. We investigated pure and mixed stands of these species in the northern part of the eastern intermediate Alps in Austria, at altitudes between approximately 880 and 1330 m above sea level. In these stands, 12 plots sized between 0.25 ha and 1.6 ha, with varying ages and proportions of Norway spruce, were established. All trees were measured for their coordinates, diameter at breast height, tree height, crown height, and crown projection area. The trees were cored at breast height, and from about 200 felled sample trees, equations for leaf area and for the five-year volume increment were developed. Growth efficiency (volume increment of a species per its fraction of the stand area) exhibited a clear interaction with age: in young mixed stands, spruce as well as larch grew less than the reference from the pure stands, while in the older stands especially spruce grew much better in the mixed stands. When the Clark Evans index was entered into the growth efficiency equations, it could be seen that the spatial distribution of the trees (i) explained more variance than the species proportion and (ii) showed an additional influence of stand density on the complementarity of the species. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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14 pages, 2654 KiB

Open AccessArticle

Nearest Neighborhood Characteristics of a Tropical Mixed Broadleaved Forest Stand

by Hong Hai Nguyen, Yousef Erfanifard and Ion Catalin Petritan

Forests 2018, 9(1), 33; https://doi.org/10.3390/f9010033 - 14 Jan 2018

Cited by 11 | Viewed by 3915

Abstract

Structural complexity and local biodiversity of species-rich tropical forests can be characterized by their spatial patterns, which contribute to species intra- and interspecific interactions. Aiming to describe spatial patterns of species at fine spatial scales, we applied the quantitative analyses based on the [...] Read more.

Structural complexity and local biodiversity of species-rich tropical forests can be characterized by their spatial patterns, which contribute to species intra- and interspecific interactions. Aiming to describe spatial patterns of species at fine spatial scales, we applied the quantitative analyses based on the relationships of nearest neighbors of conspecific and heterospecific trees. In a two-hectare plot of a tropical broadleaved forest stand in central Vietnam with minimal human influence, all tree individuals with diameter at breast height ≥ 2.5 cm were mapped and their characteristics were recorded. We applied two different types of analyses: (1) Intraspecific structural characteristics using nearest neighbor statistics; (2) overall interspecific associations through a classification scheme based on bivariate nearest neighbor distribution function D₁₂(r) and Ripley’s K function K₁₂(r). The findings showed that: (1) Most of studied species in the forest were highly mixed with other species, while conspecifics were regular to aggregated distribution at small spatial scales. Tree individuals with different diameter values were surrounded by heterospecific trees; (2) The majority of 306 species-species pairs showed spatial independence (66.7%), whereas 29.8% of all species showed an overall positive association and negative association consisted only a small percentage (3.5%) up to spatial scales of 50 m. We found significant evidences of the main ecological theories such as dispersal limitation, Neutral theory, Janzen-Connell hypothesis, and other effects like the stochastic dilution. We suggest using both the bivariate distribution of the structural parameters and the spatial point pattern analysis based on nearest neighbor distance as advantageous approaches for further understanding of population structure, as well as discovering and protecting biodiversity in the future. Full article

(This article belongs to the Special Issue Competition and Facilitation in Mixed Species Forests)

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