Roque Rodríguez-Soalleiro

Influence of edaphic factors and tree nutritive status on the productivity of Pinus radiata D. Don plantations in northwestern Spain

Relationships among soil parameters, tree nutrition and site index (SI) were examined in Pinus radiata plantations growing on soils developed from different parent materials (acid schist, granitic rocks and basic rocks) in a climatically homogeneous areas of NW Spain. Soil depth, in association with soil water balance and nutrient store, had the greatest influence on the productivity of these plantations. Although foliar N and K were sufficient in every stand studied, widespread deficiencies of P, Mg and, to a lesser extent, Ca were diagnosed. Foliar concentrations of Ca and Mg were positively correlated with soil nutrient concentrations. The main factors affecting site quality were identified with principal component analysis. The SI was positively correlated with foliar P concentrations, soil depth and pH, and negatively correlated with soil total N. Approximately 60% of the observed SI variation was accounted for by these soil properties. The results suggest the importance of site selection and fertilizer treatments in reforestation programmes.

Modelling mortality of Scots pine (Pinus sylvestris L.) plantations in the northwest of Spain

Mortality is an important element of growth and yield models, especially if only low intensity silvicultural treatments are carried out. The objective of the present study was to develop a model for predicting tree number decline in planted even-aged stands of Scots pine (Pinus sylvestris L.) in Galicia (northwestern Spain). The model was constructed using data from two inventories of a trial network involving 68 permanent plots located in unthinned stands, or stands thinned lightly from below. Two alternatives were tested. In one alternative, a two-step modelling strategy was applied. First, a binary response function predicting the survival probability of all the trees in the stand was constructed, and an equation for reduction in tree number was developed, using only data where death had occurred over the period analyzed. Three different approaches were then used to compare the application of the above-mentioned functions together. In the other alternative, a mortality function for directly predicting the reduction in tree number was fitted, including all plots (with and without occurrence of mortality). Both alternatives provided similar results, showed logical behavior, and performed satisfactorily in evaluation tests. However, in choosing the best strategy for inclusion in a stand-level simulator, the use of the second alternative is recommended because it possesses the path invariance property required in a mortality model.

Biomasa arbórea y acumulación de nutrientes en plantaciones de Pinus radiata D. Don en Galicia

Above ground tree biomass and accumulation of nutrients in Pinus radiata plantations from northern Spain In this work the amount of nutrients accumulated in the above ground biomass of nine representative Pinus radiata plantations from NW Spain were studied. From the data of 54 trees, models to estimate the mass of the different tree fractions were developed. The logging residues accumulate the most part of N (60%), as well as substantial amounts of P, K, Ca and Mg (36 to 47%). The accumulations in tree biomass of P, Mg, K and, in some cases, Ca are considerably higher than the available amounts in the soil. The data confirm that the frequent deficiencies of these elements in this type of forest plantations are due to the low nutrient storage in the soils. They also suggest that the nutritional stability of these systems is dependent on the nutrient supply by the decomposition of logging residues. These results, along with those of previous studies, show the need to carry out an appropriate management of logging residues, as well as fertilisation programmes to compensate the nutrient extractions by the clear cutting, especially if whole-tree harvesting is carried out.

Biomass production assessment from Populus spp. short‐rotation irrigated crops in Spain

The aim of this study was to evaluate the biomass production potential for the Spanish Iberian Peninsula using the Populus spp. ‘I‐214’ clone under several management regimes and land availability scenarios, and to determine its future contribution to Spanish energy demands.

Carbon balance for different management practices for fast growing tree species planted on former pastureland in southern Europe: a case study using the CO2Fix model

Although it is known that forestry mitigates carbon emissions to some degree, there is still a need to investigate the extent to which changes in forest management regimes affect the carbon cycle. In a climate-change scenario, forest management schemes must be optimized to maximize product supply and minimize environmental impacts. It is difficult to predict the mitigating effects of different silvicultural regimes because of differences in the growth characteristics of each species, destination of products, and industrial efficiencies. The objective of the present study was to use a modeling approach to evaluate the effects of different management regimes for fast growing species in southern temperate Europe in relation to mitigating climate change. A comprehensive study was carried out considering the C sink effect in biomass, soil and wood products, the substitutive effect of bioenergy, and particular conditions of the forest industry in southern Europe. The mechanistic CO2Fix model was parameterized for three species used in fast growing plantations in southern Europe: Eucalyptus globulus, Eucalyptus nitens, and Pinus radiata. Data from 120 plots covering the complete age range observed for each species were used to calculate changes in C stocks in aboveground biomass and organic and mineral soil and to validate the parameterized model for these conditions. Additional information about the efficiency of forest industry processes in the region was also considered. A strong bias in soil organic carbon estimation was observed and attributed to overestimations in the decomposition rates of soil compartments. Slight bias was also observed in the carbon biomass estimation when forest-specific yield models were used to simulate afforestation over former pastureland. As regards the model sensitivity, the Yasso model was strongly robust to turnover of leaves, roots, and branches. The chip wood production alternative yielded higher carbon stock in biomass and products, as well as in bioenergy substitution effect, than the sawn wood production alternative. Nevertheless, the sawn wood alternative was the most effective as regards the C stock in the soil. Site index had an important effect for all species, alternatives, and compartments, and mitigating effects increased with site index. Harvesting of clearcutting and thinning slash for bioenergy use led to a slight decrease in the soil carbon equilibrium but significantly increased the mitigation effect through bioenergy use.

A Density Management Diagram Including Stand Stability and Crown Fire Risk for Pseudotsuga Menziesii (Mirb.) Franco in Spain

Abstract A static stand density management diagram was constructed for Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) plantations in Spain on the basis of 3 equations that were fitted simultaneously by the full information maximum likelihood procedure to data derived from 172 plots measured across the Cantabrian and pre-Pyrenean ranges. The first equation relates quadratic mean diameter to the number of stems per hectare and dominant height. The other 2 equations relate stand volume and stand aboveground biomass to quadratic mean diameter, number of stems per hectare, and dominant height. An estimation of the average slenderness coefficient for the 250 largest trees per hectare and the canopy bulk density were included. The stand density management diagram outlined here enables rapid, straightforward comparisons among different thinning schedules for forest plantations in mountain regions, in which timber production, risk of crown fire, and the risk of damage from wind or snow are considered.

Respuesta inicial del aporte de cenizas de biomasa arbórea en el estado nutricional de una plantación joven de Pinus radiata D. Don

El objetivo del presente ensayo fue evaluar la respuesta del empleo de cenizas de corteza de madera como enmendante y fertilizante de una plantacion joven de Pinus radiata que se desarrolla sobre un suelo forestal acido. El trabajo consistio en un ensayo de campo, con aporte de dos dosis de cenizas en cobertera (5.000 kg ha-1 y 10.000 kg ha-1) y una dosis de fertilizante mineral NPK 8:24:16 (200 g en hoyo) en el momento del establecimiento de la plantacion. Durante 28 meses se evaluo la respuesta de la fraccion solida del suelo y de la composicion quimica de las aciculas. El aporte de cenizas derivo en aumentos temporales del pH y de la concentracion de Ca, Mg, P y K disponible en el suelo. Esta mejora de las propiedades quimicas del suelo se tradujo en incrementos temporales en la concentracion de Ca y, en menor medida, de Mg en las aciculas. Como posible diagnostico, el analisis de vectores de los contenidos y concentraciones de nutrientes foliares mostro que estos dos elementos limitaban el crecimiento de la especie.

On the Genetic Affinity of Individual Tree Biomass Allometry in Poplar Short Rotation Coppice

Woody biomass is one of our main resources available to enhance the bio-economy, but its production varies considerably depending on the species, the environment and crop management. The variability associated with these crops complicates the estimation of biomass through prediction models. The specificity of environment or genotype level limits the application of many of the models, which are often developed for use at local geographical levels. Although generalizations involve some loss of accuracy, the inclusion of a wide range of data for a wide range of environments and genotypes can improve model applicability. A total of 11,265 data from short-rotation, high-density poplar plantations (from 22 sites in Spain, covering 29 genotypes belonging to 7 different taxonomic groups) were used to develop biomass prediction models under Mediterranean conditions and to test whether similarities in individual tree biomass allometry occur within the taxonomic group level. A general model and both taxonomic group- and genotype-level models were fitted using weighted nonlinear regression. The simplified model, in which only the basal diameter is included, presented the best model performance, explaining 87% of the variability. The allometric similarities among different genotypes were evaluated in order to explore the relationship between the most frequently used poplar genotypes in the Mediterranean area, and although certain groups were identified, it was not possible to relate these similarities among different genotypes to their taxonomic group affinity. This was also confirmed by comparing the performance of the general models with the taxonomic group-level models when predicting at the genotype level. Although estimates made using the general models are relatively precise, the use of genotype-level models is recommended for more accurate predictions.

Modelling dominant height growth in plantations of Pseudotsuga menziesii (Mirb.) Franco in Spain

A model for predicting dominant height growth and site index of Pseudotsuga menziesii (Mirb.) Franco in Spain was constructed. Data from stem analysis of 117 site trees were used. Four dynamic equations using the algebraic difference approach (ADA) and its generalisation (GADA), which have provided good results in previous studies, were evaluated. The model parameters were estimated with the base‑age‑invariant method of dummy variables, which considers both global (common to all sites) and local parameters (specific to each site). A GADA equation based on the Bertalanffy–Richards base model yielded the best results. The model provides polymorphic curves with multiple asymptotes. A base age of 20 years is proposed to reference site index.

MIXED AND MONOSPECIFIC STANDS OF EUCALYPTUS AND BLACK-WATTLE. II - FINE ROOT BIOMASS DENSITY

The aim of this study was to evaluate fine root biomass density (FRBD) in mixed and monospecific stands of Eucalyptus grandis x E. urophylla and Acacia mearnsii(black wattle) in Bage-RS (Southern Brazil). An experimental trial was installed with three treatments: 100% Eucalyptus (100E); 100% Acacia mearnsii (100A); 50% Eucalyptus + 50% Acacia mearnsii (50E:50A). The trial was carried using a randomized block design with three replicates. The fine root (l 2.0mm) biomass density was determined 8 and 18 months after planting the trees. Soil samples were collected, with a cylindrical extractor auger (d = 7.0 cm), from four depths (0 - 5, 5 - 10, 10 - 20 and 20 - 30 cm) at each sampling point. After 8 months, the FRBD distribution was the same in both species and in all soil layers, reaching the maximum projection at 125 cm from the tree trunk. After 18 months, the root biomass density was higher in the monospecific black wattle stand than in the monospecific eucalyptus stand and the mixed stand. The fine root biomass density was highest in the 5 - 10 cm layer close to the trunk, for the planting row spacing, the planting line and the diagonals between two planting lines. Knowledge about fine root growth and distribution in soil at initial stages of stand development may help in decision-making for intensive forestry, thus ensuring more efficient use of soil resources.