Models for estimating biomass and carbon in biomass and soils in Pinus radiata (D. Don), Eucalyptus globulus (Labill) and Eucalyptus nitens (Deane & Maiden) Maiden plantations established in former agricultural lands in northwestern Spain

The aim of this work is to discuss modelling and estimation of C evolution in forest plantations. The study focused on the three levels at which C can be estimated: tree, stand and landscape level. The study involved evaluation of a dynamic process, i.e. the afforestation of former pasture land

Characterisation of Woody Necromass in Beech Forests with Different Anthropic Accessibility: The Case of La Rioja (Spain)

In this study, a comprehensive analysis of deadwood was conducted in four macro-areas located in two beech forests of public utility in Enciso (La Rioja, Spain). Dendrometric data, as well as qualitative and quantitative characteristics of deadwood, were collected and analysed with respect to the degree of accessibility to the forest to determine the effect of different levels of forest accessibility on deadwood volume and carbon stocks. All decomposition classes were present except the first, highlighting the development of natural degradation dynamics. Deadwood stored 6.9 t/ha of C in the easy accessibility class, 5.7 t/ha of C in the medium accessibility class and 2.2 t/ha of C in the difficult accessibility class. The average volume of deadwood and carbon stored calculated in this study were higher than the values reported in the Spanish and Italian national forest inventories, including one developed for Riojan beech forests. Deadwood volume was on average 22.5 m3/ha, showing an unequal distribution, with the lowest values found far from the access roads, despite forest accessibility generally being considered a factor that facilitates the human collection of deadwood. The distribution patterns of deadwood in beech forests of La Rioja, apparently counterintuitive, were due to a combination of different factors, including slope, cattle grazing, and weather conditions which might have favoured downward movement of the deadwoodThis research was funded by the Spanish Ministry of Science, Innovation and Universities, AGL2016-76769-C2-2-RS

Spatial distribution of soil organic carbon stock in Moso bamboo forests in subtropical China

Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) is an important timber substitute in China. Site specific stand management requires an accurate estimate of soil organic carbon (SOC) stock for maintaining stand productivity and understanding global carbon cycling. This study compared ordinary kriging (OK) and inverse distance weighting (IDW) approaches to study the spatial distribution of SOC stock within 0–60cm using 111 soil samples in Moso bamboo forests in subtropical China. Similar spatial patterns but different spatial distribution ranges of SOC stock from OK and IDW highlighted the necessity to apply different approaches to obtain accurate and consistent results of SOC stock distribution. Different spatial patterns of SOC stock suggested the use of different fertilization treatments in Moso bamboo forests across the study area. SOC pool within 0–60cm was 6.46 and 6.22 Tg for OK and IDW; results which were lower than that of conventional approach (CA, 7.41 Tg). CA is not recommended unless coordinates of the sampling locations are missing and the spatial patterns of SOC stock are not required. OK is recommended for the uneven distribution of sampling locations. Our results can improve methodology selection for investigating spatial distribution of SOC stock in Moso bamboo forestsThis study was funded by Demonstration Project of Bamboo Forest of State Forest Administration ([2015]13), National Scientific Plan for Rural Area (Grant No. 2015BAD04B0203)S

Thermodynamic characterization of LF, H, and mineral soil layers from oak forest ecosystems: exploring the role of proximate analysis

Studying the thermodynamic properties of soil organic matter is a developing field that involves the measurement of the energy stored by the soil. Quantifying soil energy content is still challenging despite different methodological approaches are available to calculate that value. One of the options is the proximate analysis following the guidelines for the energetic characterization of biomass. However, proximate analyses are still unexplored for soils. In this paper, we investigate the potential of this analysis to contribute to study soil from a thermodynamic perspective. With that goal, 31 soil samples collected in mature oak forests following a depth transect were used for elemental, thermal and proximate analysis. Proximate analyses and energetic characterization were performed by simultaneous thermogravimetry and differential scanning calorimetryThe authors thank Verónica Piñeiro and Montse Gómez of the RIAIDT analytical services at the University of Santiago de Compostela (Spain) for elemental and thermal analysis. Authors also thank Ken Byrne from the department of Biological Sciences, University of Limerick (Ireland), Eva Vanguelova from the Alice Holt Forest Research Station (UK) and Ander Arias González from Neiker-Tecnalia Basque Institute for Agricultural Research and Development (Spain) for the soil samples supply. This work has been developed under the project CONGESTION, funded by the by the Spanish Ministery of Science and Innovation (PID 2022-119204RB-C22)S

Poplar Short Rotation Coppice Plantations under Mediterranean Conditions: The Case of Spain

Developing a circular bioeconomy based on the sustainable use of biological resources, such as biomass, seems to be the best way of responding to the challenges associated with global change. Among the many sources, short rotation forest crops are an essential instrument for obtaining quality biomass with a predictable periodicity and yield, according to the areas of cultivation. This review aims to provide an overview of available knowledge on short rotation coppice Populus spp. plantations under Mediterranean conditions and specifically in Spain, in order to identify not only the status, but also the future prospects, for this type of biomass production. The analysis of available information was conducted by taking into consideration the following aspects: Genetic plant material; plantation design, including densities, rotation lengths and the number of rotations, and mixtures; management activities, including irrigation, fertilization, and weed control; yield prediction; biomass characterization; and finally, an evaluation of the sustainability of the plantation and ecosystem services provided. Despite advances, there is still much to be done if these plantations are to become a commercial reality in some Mediterranean areas. To achieve this aim, different aspects need to be reconsidered, such as irrigation, bearing in mind that water restrictions represent a real threat; the specific adaptation of genetic material to these conditions, in order to obtain a greater efficiency in resource use, as well as a greater resistance to pests and diseases or tolerance to abiotic stresses such as drought and salinity; rationalizing fertilization; quantifying and valuing the ecosystem services; the advance of more reliable predictive models based on ecophysiology; the specific characterization of biomass for its final use (bioenergy/bioproducts); technological improvements in management and harvesting; and finally, improving the critical aspects detected in environmental, energy, and economic analyses to achieve profitable and sustainable plantations under Mediterranean conditionsThis research was funded by the Ministry of Science and Innovation (Spain) through the framework of the INIA projects RTA2017-00015-CO2, co-financed with funds from FEDERS

Evaluating the potential of ALS data to increase the efficiency of aboveground biomass estimates in tropical peat–swamp forests

Estimates of aboveground biomass (AGB) in forests are critically required by many actors including forest managers, forest services and policy makers. Because the AGB of a forest cannot be observed directly, models need to be employed. Allometric models that predict the AGB of a single tree as a function of diameter at breast height (DBH) are commonly used in forest inventories that use a probability selection scheme to estimate total AGB. However, for forest areas with limited accessibility, implementing such a field-based survey can be challenging. In such cases, models that use remotely sensed information may support the biomass assessment if useful predictor variables are available and statistically sound estimators can be derived. Airborne laser scanning (ALS) has become a prominent auxiliary data source for forest biomass assessments and is even considered to be one of the most promising technologies for AGB assessments in forests. In this study, we combined ALS and forest inventory data from a logged-over tropical peat swamp forest in Central Kalimantan, Indonesia to estimate total AGB. Our objective was to compare the precision of AGB estimates from two approaches: (i) from a field-based inventory only and, (ii) from an ALS-assisted approach where ALS and field inventory data were combined. We were particularly interested in analyzing whether the precision of AGB estimates can be improved by integrating ALS data under the particular conditions. For the inventory, we used a standard approach based on a systematic square sample grid. For building a biomass-link model that relates the field based AGB estimates to ALS derived metrics, we used a parametric nonlinear model. From the field-based approach, the estimated mean AGB was 241.38 Mgha −1 with a standard error of 11.17 Mgha −1 (SE% = 4.63%). Using the ALS-assisted approach, we estimated a similar mean AGB of 245.08 Mgha −1 with a slightly smaller standard error of 10.57 Mgha −1 (SE% = 4.30%). Altogether, this is an improvement of precision of estimation, even though the biomass-link model we found showed a large Root Mean Square Error (RMSE) of 47.43 Mgha −1 . We conclude that ALS data can support the estimation of AGB in logged-over tropical peat swamp forests even if the model quality is relatively low. A modest increase in precision of estimation (from 4.6% to 4.3%), as we found it in our study area, will be welcomed by all forest inventory planners as long as ALS data and analysis expertise are available at low or no cost. Otherwise, it gives rise to a challenging economic question, namely whether the cost of the acquisition of ALS data is reasonable in light of the actual increase in precisionWe are grateful to the Galician Government and European Social Fund (Official Journal of Galicia DOG n 52, 17 March 2014, p. 11343, exp: POS-A/2013/049) for financing the postdoctoral research stays of Eduardo González-Ferreiro at different institutionsS

The Horizontal Distribution of Branch Biomass in European Beech: A Model Based on Measurements and TLS Based Proxies

Forest biomass is currently among the most important and most researched target variables in forest monitoring. The common approach of observing individual tree biomass in forest inventory is to assign the total tree biomass to the dimensionless point of the tree position. However, the tree biomass, in particular in the crown, is horizontally distributed above the crown projection area. This horizontal distribution of individual tree biomass (HBD) has not attracted much attention—but if quantified, it can improve biomass estimation and help to better represent the spatial distribution of forest fuel. In this study, we derive a first empirical model of the branch HBD for individual trees of European beech (Fagus sylvatica L.). We destructively measured 23 beech trees to derive an empirical model for the branch HBD. We then applied Terrestrial Laser Scanning (TLS) to a subset of 17 trees to test a simple point cloud metric predicting the branch HBD. We observed similarities between a branch HBD and commonly applied taper functions, which inspired our HBD model formulations. The models performed well in representing the HBD both for the measured biomass, and the TLS-based metric. Our models may be used as first approximations to the HBD of individual trees—while our methodological approach may extend to trees of different sizes and speciesThis research was funded by the Forest Research Institute of the German Federal State of Rheinland-Pfalz (FAWF) in Trippstadt. We also thank the Marie Sklodowska-Curie Action fellow QUAFORD and the Ramón y Cajal Tenure Track awarded to C.P.-CS

Assessing site form as an indicator of site quality in even-aged Pinus radiata D. Don stands in north-western Spain

[EN] Key message: Site form and site index have shown similar precision for estimating site quality in even-agedPinus radiataD. Don stands in north-western Spain. Additionally, SF presents the advantage that it does not require stand age information and can therefore be used in a wider set of situations in the forestry practice. Context: Estimation of site quality is essential for characterizing, monitoring and predicting forest resources. Site index (i.e. the dominant height of the stand at a reference age) is ordinarily used to estimate site quality; however, this index is only useful for even-aged stands of known age. By contrast, SF is age-independent as it uses the dominant height of the stand at a reference dominant diameter. Aims: The aim of this study was to compare the performance of SF and SI for site quality estimation in even-aged P. radiata stands. Methods: Dynamic equations derived with the Generalized Algebraic Difference Approach (GADA) from the Hossfeld IV base model were fitted to predict site quality with both SI and SF. SF predictions were compared with SI regarding variability within the same plot and consistency in site quality predictions, using the observed maximum mean annual volume increment (MAI) as a direct measure of site quality. Results: Both approaches showed good performance in model fitting and provided similar goodness-of-fit statistics and variability in the predictions. However, SI performed slightly stronger when related to MAISIThis study was funded by the Spanish Ministry of Science, Innovation and Universities (AGL2016-76769-C2-2-R). JAMV was funded by Ministry of Education through the FPU program (FPU16/03057). CPC was funded by the Spanish Secretariat of State for Research, Development and Innovation through the JdC-I fellowship and by the European Commission thorough the MSCA-EF QUAFOR

Assessing site form as an indicator of site quality in even-aged Pinus radiata D. Don stands in north-western Spain

Key message: Site form and site index have shown similar precision for estimating site quality in even-aged Pinus radiata D. Don stands in north-western Spain. Additionally, SF presents the advantage that it does not require stand age information and can therefore be used in a wider set of situations in the forestry practice. Context: Estimation of site quality is essential for characterizing, monitoring and predicting forest resources. Site index (i.e. the dominant height of the stand at a reference age) is ordinarily used to estimate site quality; however, this index is only useful for even-aged stands of known age. By contrast, SF is age-independent as it uses the dominant height of the stand at a reference dominant diameter. Aims: The aim of this study was to compare the performance of SF and SI for site quality estimation in even-aged P. radiata stands. Methods: Dynamic equations derived with the Generalized Algebraic Difference Approach (GADA) from the Hossfeld IV base model were fitted to predict site quality with both SI and SF. SF predictions were compared with SI regarding variability within the same plot and consistency in site quality predictions, using the observed maximum mean annual volume increment (MAI) as a direct measure of site quality. Results: Both approaches showed good performance in model fitting and provided similar goodness-of-fit statistics and variability in the predictions. However, SI performed slightly stronger when related to MAI. Conclusion: SF performed adequately in estimating site quality for even-aged P. radiata stands, with results comparable to those obtained using traditional SIThis study was funded by the Spanish Ministry of Science, Innovation and Universities (AGL2016-76769-C2-2-R). JAMV was funded by Ministry of Education through the FPU program (FPU16/03057). CPC was funded by the Spanish Secretariat of State for Research, Development and Innovation through the JdC-I fellowship and by the European Commission thorough the MSCA-EF QUAFORDS

Diseño de inventarios forestales en poblaciones muy fragmentadas: un caso de estudiosobre el uso de información catastral en Galicia

[ES] Los inventarios forestales (IFs) permiten conocer y evaluar el estado de los sistemas forestales, lo que los convierte en una herramienta de apoyo fundamental para los procesos de toma de decisiones y planificación de una gestión forestal sostenible. La fase de diseño y planificación de un IF es clave a la hora de garantizar la calidad y fiabilidad de los resultados que de él se deriven. Dos de las principales cuestiones a establecer durante el diseño de un IF son (i) la población objetivo y el diseño muestral, y (ii) el diseño de parcela. Los diseños demuestra y parcela más habituales en IF pueden presentar ciertas limitaciones cuando las masas forestales objetivo están muy fragmentadas, como ocurre en el caso de Galicia, debido a la alta probabilidad de que las áreas de medición seleccionadas intersequen parcelas con distintos usos, especies o edades. En este trabajo se ha estudiado, desde el punto de vista teórico, el efecto sobre la variabilidad de la muestra de la utilización de información catastral en el proceso de optimización del diseño de un IF para Galicia, cuya población forestal se caracteriza por presentar un alto nivel de fragmentació