Open Access
Coarse woody debris' invertebrate community is affected directly by canopy type and indirectly by thinning in mixed scots pine-European beech forests
(MDPI, 2020) Herrera Álvarez, Ximena; Blanco Vaca, Juan Antonio; Imbert Rodríguez, Bosco; Álvarez, Willin; Rivadeneira Barba, Gabriela; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias
Research Highlights: Thinning and tree species alter the forest floor microclimate by modifying canopy cover, radiation, wind, and humidity. Thus, forest management can directly influence the edaphic mesofauna responsible for decomposing coarse woody debris (CWD). Background and Objectives: This research was carried out in the Southwestern Pyrenees Mountains (Northern Spain) and aimed to determine the influence of forest thinning and canopy type (pure Pinus sylvestris L. or a mix of P. sylvestris and Fagus sylvatica L.) on CWD colonization by edaphic fauna. Materials and Methods: CWD samples were collected belonging to intermediate and advanced decomposition stages, approximately 10 cm long and 5 cm in diameter. Using a design of three thinning intensities (0%, 20%, and 40% of basal area removed), with three replications per treatment (nine plots in total), four samples were taken per plot (two per canopy type) to reach 36 samples in total. Meso- and macrofauna were extracted from CWD samples with Berlese-Tullgren funnels, and individuals were counted and identified. Results: 19 taxonomic groups were recorded, the most abundant being the mesofauna (mites and Collembola). Mixed canopy type had a significant positive influence on richness, whereas advanced decay class had a positive significant influence on total abundance and richness. In addition, there were non-significant decreasing trends in richness and abundance with increasing thinning intensity. However, interactions among thinning intensity, canopy type, and decay class significantly affected mesofauna. Furthermore, some taxonomic groups showed differential responses to canopy type. CWD water content was positively correlated with total invertebrate abundance and some taxonomic groups. Our results suggest that stand composition has the potential to directly affect invertebrate communities in CWD, whereas stand density influence is indirect and mostly realized through changes in CWD moisture. As mesofauna is related to CWD decomposition rates, these effects should be accounted for when planning forest management transition from pure to mixed forests.
Open Access
Sensitivity of long-term productivity estimations in mixed forests to uncertain parameters related to fine roots.
(Elsevier, 2024) Yeste Yeste, Antonio; Seely, Brad; Imbert Rodríguez, Bosco; Blanco Vaca, Juan Antonio; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB
Forest growth models are increasingly being used in forestry and ecology research as predictive tools to help developing practical guidelines and to improve understanding of the drivers of forest ecosystem functioning. Models are usually calibrated using parameters directly obtained or estimated from empirical field observation, and hence are subject to uncertainty. Thus, output accuracy depends on input parameters precision and on how influential is each parameter on model behaviour. Hence, it is important to analyse parameter-related uncertainty and its effects on model outputs. This can be done by performing sensitivity analyses, which allow to explore the influence of one or several calibration parameters on model outputs. As studies on tree root parameters are particularly scarce, the aim of the present work was to evaluate the influence of parameters related to fine roots on estimations of long-term forest growth patterns in pure and mixed forests, using FORECAST (a hybrid forest growth model) as a virtual lab. The fine root parameters assessed were biomass, turnover rate, and nitrogen content. The analysis was performed by simulating monospecific stands of two contrasting species (Pinus sylvestris L. and Fagus sylvatica L.), and mixed stands formed by both species. In all cases, FORECAST showed good capability to contain uncertainty propagation during the first and middle stages of stand development (<40 years). After that moment, model output uncertainty steadily increased, but it reached different maximum uncertainty levels depending on stand type. Simulations of the less nutrient demanding P. sylvestris manifested very little sensitivity when growing in monospecific stands. However, F. sylvatica monospecific stands showed intermediate sensitivity, but significant species interactions occurred in mixed stands that determined the biggest impact detected of uncertainty related to fine root parameters over model outputs. All things considered, FORECAST displayed an interesting capability to capture some of the interspecific interactions that are key in mixed forests functioning. Our results suggest an acceptable model performance under uncertain parameterization but also caution against expecting accurate quantitative estimations of forest growth, especially when considering long-term scenarios in complex mixed stands.

Imbert Rodríguez, Bosco

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