European Mixed Forests: definition and research perspectives

Aim of study: We aim at (i) developing a reference definition of mixed forests in order to harmonize comparative research in mixed forests and (ii) briefly review the research perspectives in mixed forests. Area of study: The definition is developed in Europe but can be tested worldwide. Material and methods: Review of existent definitions of mixed forests based and literature review encompassing dynamics, management and economic valuation of mixed forests. Main results: A mixed forest is defined as a forest unit, excluding linear formations, where at least two tree species coexist at any developmental stage, sharing common resources (light, water, and/or soil nutrients). The presence of each of the component species is normally quantified as a proportion of the number of stems or of basal area, although volume, biomass or canopy cover as well as proportions by occupied stand area may be used for specific objectives. A variety of structures and patterns of mixtures can occur, and the interactions between the component species and their relative proportions may change over time. The research perspectives identified are (i) species interactions and responses to hazards, (ii) the concept of maximum density in mixed forests, (iii) conversion of monocultures to mixed-species forest and (iv) economic valuation of ecosystem services provided by mixed forests. Research highlights: The definition is considered a high-level one which encompasses previous attempts to define mixed forests. Current fields of research indicate that gradient studies, experimental design approaches, and model simulations are key topics providing new research opportunities. Key words: COST Action; EuMIXFOR; mixed-species forests; admixtures of species.Instituto Universitario de Gestión Forestal Sostenibl

Carbon sequestration in Spanish Mediterranean forest under two management alternatives: A modeling approach

Management implications associated with two different silvicultural strategies in two Spanish pine forests (Scots pine stands in northern Spain and Mediterranean Maritime pine stands in Central Spain) were explored. Whole-stand yield, growth models and individual tree equations were used to estimate carbon stock in forests under different silvicultural alternatives and site indexes. Each alternative was evaluated on the basis of the land expectation value (LEV). Results reveal the appropriateness of implementing carbon payments, because it can clearly complement traditional management objectives in economic terms. Longer rotations on the poorest sites result in a positive economic return by introducing carbon output. The proportion of carbon stock in the final harvest relative to total fixed carbon is always higher in long rotation scenarios. However, short rotation systems produce the highest values of carbon MAI regardless of site index. The impact of carbon price is higher on the Maritime pine stands than on Scots pine stands. For both the species, changes in the discount rate have a minor impact on Carbon LEV. Notwithstanding, the proportion of total LEV due to carbon is greater when the discount rate increases.Instituto Universitario de Gestión Forestal Sostenibl

Soil and forest productivity: a case study from Stone pine (Pinus pinea L.) stands in Calabria (southern Italy)

The objective of this study was to determine whether edaphic and/or topographic variables may be used as predictors of site productivity in Stone pine stands in Calabria (southern Italy). To accomplish this goal, a linear discriminant rule was developed using data from 16 pure Stone pine stands, grouped into three different classes based on the mean dominant height annual growth. The discriminant rule was based on three linear models (one for each class) that jointly predicts site class for a given stand. To test the accuracy of the proposed method, cross-validation was carried out by developing 16 alternative discriminant rules (excluding the analyzed data). Predictors tested were edaphic (texture, pH, organic matter) and topographic (altitude and slope) variables. The model obtained allow to discriminate poorest sites accurately (100% of sites were correctly re-classified using the discriminant functions obtained). In more productive areas, sites were correctly re-classified in the 33.33% of cases, while in intermediate sites the correct classification was equal to 50%. Our discriminant rule classifies correctly the poorest stands, suggesting that site index in plain site soils strongly depends on clay percentage. Overall, the edaphic model obtained classifies plots into the correct site index class 61.11% of cases, which is considered an acceptable value for these kinds of studies.Instituto Universitario de Gestión Forestal Sostenibl

Mediterranean pine forests: management effects on carbon stocks

Carbon stored in forest systems is of great interest from a management point of view since, on the one hand,it is easily modified through silvilcultural practices (e.g.,rotation length,thinning, etc.), while,on the other hand, it affects the mean lifespan of wood products.In the Mediterranean area, the role of forest as carbon sinks is particularly significant since usually ecosystem services provided by forests are frequently of greater value than their direct productions.Therefore,quantifying the carbon balance in forests ís one of the main challenges if carbon fixation is to be considered amongst the objectives of forest management (Montero et al., 2005).Instituto Universitario de Gestión Forestal Sostenibl

Site index estimation in Scots pine (Pinus sylvestris L.) stands in the High Ebro Basin (northern Spain) using soil attributes

Site index curves and an edaphic discriminant rule for Scots pine stands in the High Ebro Basin (northern Spain) are presented to estimate site index under different silvicultural situations. High‐grading practices strongly modify the forestry structure by the means of bias in the dominant height and stand density. In order to achieve the silvicultural and site variability of Scots pine stands in the studied area, 75 plots from the National Forest Inventory of Spain (NFI) were selected. In these plots 46 dominant trees were cut down and 104 trees were bored at stump and at breast height (1.3 m). In each plot a soil sample from the first 10 cm of soil was taken and signs of dimensional cutting were recorded. Site index curves and the edaphic discriminant rule were developed. The site index curve model used is an extension of the Richards model. The site factors selected in the discriminant rule represent the most important edaphic parameters for forest productivity (texture and the assimilability of the nutrients). Site quality of the studied stands was medium‐low as compared with other site index curves for Scots pine around the world. The edaphic discriminant rule presented is useful for estimating site index classes in stands exposed to dimensional cutting and in young stands of Scots pine in the the High Ebro Basin (northern Spain). Site index curves were fitted to allow an estimate of the site index of undisturbed and stands which were not high‐graded.Instituto Universitario de Gestión Forestal Sostenibl

Environmental variability and its relationship to site index in Mediterranean maritine pine

Producción CientíficaEnvironmental variability and site productivity relationships, estimated by means of soil-site equations, are considered a milestone in decision making of forest management. The adequacy of silvicultural systems is related to tree response to environmental conditions. The objectives of this paper are to study climatic and edaphic variability in Mediterranean Maritime pine (Pinus pinaster) forests in Spain, and the practical use of such variability in determining forest productivity by means of site index estimation. Principal component analysis was used to describe environmental conditions and patterns. Site index predictive models were fitted using partial least squares and parsimoniously by ordinary least square. Climatic variables along with parent material defined an ecological regionalization from warm and humid to cold and dry sites. Results showed that temperature and precipitation in autumn and winter, along with longitudinal gradient define extreme site qualities. The best qualities are located in warm and humid sites whereas the poorest ones are found in cold and dry regions. Site index values are poorly explained by soil properties. However, clay content in the first mineral horizon improved the soil-site model considerably. Climate is the main driver of productivity of Mediterranean Maritime pine in a broad scale. Site index differences within a homogenous climatic region are associated to soil properties

Evaluation of new silvicultural alternatives for Scots pine stands in northern Spain

The new objectives which society is demanding of forest systems are leading to deep changes in their management. Aspects such as biodiversity preservation and recreation require forest management alternatives that are not based on the traditional management centered on the maximization of timber production. In this paper, we introduce five silvicultural alternatives different from those typically implemented. They are characterized by combining more intensive management practices in four cases, with the retention of a portion of the stand in the final cutting, and the extension of rotation to fulfill these non-timber producing objectives in the other case. The results for one stand of Pinus sylvestris L. in the north of Spain have been evaluated in physical terms (total volume, veneer volume), as well as in financial terms (L and Expectation Value, LEV), showing some of the alternatives its feasibility in comparison with traditional management.Instituto Universitario de Gestión Forestal Sostenibl

Plasticity in Pinus pinaster populations of diverse origins: Comparative seedling responses to light and Nitrogen availability

The effects of light and N availability, and population on seedling morphology and biomass allocation were assessed in eleven months seedlings from ten Pinus pinaster populations. We conducted a garden experiment using a light gradient (full sunlight, HL= 337.1 μmol m2 s-1; medium light, ML= 120.6 μmol m2 s-1; and low light, LL= 30 μmol m2 s-1) and two contrasting soil fertility regimes: low-N and high-N availability. Light availability was an important factor controlling phenotypic plasticity. However, differences between productivity environments were observed, especially in full sunlight and medium light conditions, which suggest that soil fertility may be very important at early successional stages at open and medium shaded microsites, but would exert low influence in deep shade conditions. Population-specific responses were observed for many traits, which suggest a genetic control of morphological plasticity. All populations produced more total dry weight with HL and high-N. When light and/or N richness varied, growth depended upon which resource was more limiting. Results indicated ontogenetic drift but when seedlings were compared at the same size, results fitted with optimal partitioning theory. Allocation to needles was higher in HL and ML/ high-N conditions, while allocation to root was higher in low-N seedlings in HL and ML conditions. With shade (ML and LL) all populations allocated more dry weight to stem, regardless N availability. A significant increment in stem height was observed with shade increase.Instituto Universitario de Gestión Forestal Sostenibl

Innovation in the value chain of wood products: data, equations and life-cycle analysis

This chapter represents a review of the state of the art of the techniques and methodologies described and used in Lizarralde et af., 2008. Several issues have been reviewed and updated, while the work area and most of data remain equal,as an exercise of methodology review. Assessment of C02 sequestration on wood products starts to raise importance when measuring the global sequestration in a forest. In this work, a more accurate estimation of C0.2 on wood products is proposed,taking into account not only the volume but the useful life of those products. In order to estímate this carbon uptake and sequestration, innovation in forestry reveals new technologies and methodologies such as forest inventory using LiDAR technology or advanced modelling techniques. Besides,a new accountability and legal framework is added to review the state of the art of this particular issue. With this new information and knowing yield data of transformation of these products in final commercial products, the sequestration rate of each product and its useful life, we will be able to calculate the global sequestration of annual cuttings in an important and well-known forest in Spain.Instituto Universitario de Gestión Forestal Sostenibl

Viability of thinning sessile oak stands by girdling

he effects of girdling were analysed in a sessile oak (Quercus petraea Matts. Leibl.) forest with an 80-year-old coppice with standard structure in northern Spain. The study evaluated the viability of girdling as an alternative to felling trees during crown thinning. Eighty-four direct competitors of selected future crop trees were girdled by double notching and peeling. Three years after girdling, 100 per cent of the treated trees had died. Approximately half of the girdled trees did not resprout. The occurrence of basal sprouting was very low, and more than 35 per cent of the sprouts had very low vigour. No correlation was found between sprouting and the diameter of the girdled trees or the distance to their nearest neighbour. A negative relationship between the diameter of the girdled tree and the stage of decline was recognized. Girdling is an economic alternative to non-commercial thinning in oak stands and can be seen as an effective structural enrichment treatment.Instituto Universitario de Gestión Forestal Sostenibl