*Editorial* **The Diversity of Wood and Non-Wood Forest Products: Anatomical, Physical, and Chemical Properties, and Potential Applications**

**Vicelina Sousa \*, Isabel Miranda, Teresa Quilhó and Helena Pereira**

Centro de Estudos Florestais, Laboratório Associado TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal; imiranda@isa.ulisboa.pt (I.M.); terisantos@isa.ulisboa.pt (T.Q.); hpereira@isa.ulisboa.pt (H.P.)

**\*** Correspondence: vsousa@isa.ulisboa.pt

Forests are continuously changing, as is the related gap in our understanding. The resources diversity of forests is enormous because of the existence of temperate, boreal, and tropical forests. Before the implementation of any forest or agroforestry practices, the resources were mainly used based only on resource proximity and availability. Systematic forestry knowledge allows us to increase wood production and ensure species conservation. The present and urgent challenge is to follow the major guidelines set out for forest resources sustainability management in the context of both ecosystem-related global warming threats and green-economy needs. Yet, there are several forest resources that are not well known, and specific knowledge regarding the structure, anatomy, and properties is therefore an essential tool in assessing the potential and suitability of these different forest resources. Understanding and predicting effects on the growth and quality of each forest resource due to abiotic and biotic factors and conditions is complex and of crucial importance for sustainable forest resources management.

This Special Issue, "The Diversity of Wood and Non-Wood Forest Products: Anatomical, Physical, and Chemical Properties, and Potential Applications", features a collection of articles on diverse species ranging from temperate to tropical regions (endemic species, lesser-known timber species, invasive species, and non-woody species), highlighting their potential as wood and non-wood forest products. The research findings contained herein fulfill the Special Issue's proposed aim, i.e., to contribute to diversifying the lignocellulosic supply and to preserve species with the potential for high-quality end use, thereby increasing forest sustainability and diversity.

Rattan are monocotyledonous plants, also known as palms, mainly distributed in tropical forests in Southeast Asia and in West and Central Africa, with a high economic value due to their use in furniture production [1]. Rattan species are considered alternatives to timber species. However, studies on rattan species belonging to the *Calamus* genus, the most rich and traded genus, are still quite scarce [1]. Addressing this research gap, Ahmed et al. [1] studied the within-stem variability of two rattan species, *Calamus zollingeri* Beccari and *Calamus ornatus* Blume, growing in Indonesia, to analyse the potential of lignocellulosic material based on its biological durability and anatomical/physical properties.

Mediterranean oaks, and in particular the cork oak, *Quercus suber* L., even if welladapted to the adverse conditions of the Mediterranean climate, are considered to be under threat due to climate change and pests [2,3]. Simões et al. [2] studied the seasonal variation of the chemical composition of cuticular waxes in cork oak leaves due to their ability to control water loss during abiotic stresses such as drought and high temperatures in an effort to contribute to climate change adaptation measures. Moreover, the major biotic threats are related to the cork borer, *Coraebus undatus* Fabricius (Coleoptera, Buprestidae), named "cobrilha da cortiça" in Portugal and "culebrilla" in Spain, the impact of which on

**Citation:** Sousa, V.; Miranda, I.; Quilhó, T.; Pereira, H. The Diversity of Wood and Non-Wood Forest Products: Anatomical, Physical, and Chemical Properties, and Potential Applications. *Forests* **2023**, *14*, 1988. https://doi.org/10.3390/f14101988

Received: 28 September 2023 Accepted: 29 September 2023 Published: 3 October 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

cork quality was also studied by Simões et al. [3], analysing the cork chemical profile of secondary metabolites.

Another species considered a source of cork is the Chinese cork oak, *Quercus variabilis* Blume, also distributed in Korea, even if there is no reproduction cork from this species yet available for industrial use [4]. With the aim of exploring the further utilization of domestic cork resources in Korean cork industries, Prasetia et al. [4] presented and discussed the quantitative anatomical characteristics of virgin cork from *Quercus variabilis* growing in Korea and compared it to the reproductive cork from *Quercus suber* from Portugal. The authors suggest processing treatments and applications for the virgin cork based on its structural characteristics.

In the tropical forests of Gabon, a new morphospecies within the *Dialium* genus was introduced for the first time and studied by Doucet et al. [5], focusing on its discriminant leaf and wood composition traits. Since a limited number of timber species are presently used, the newly presented species, as well as other species such as *Dialium pachyphyllum* Harms and *Dialium lopense* Breteler, are important alternative species [5]. However, the authors mention the need to implement strategies for the sustainable wood production and conservation of these species.

The variability in the wood properties of several tropical species from India, East-Timor, and Mozambique, including important commercial species, such as *Tectona grandis* L. as well as lesser-known species have been studied by Bessa et al. [6], aiming to contribute to design targeted production and increase wood tropical resources diversity. Species with different geographical origins were grouped based on anatomical and physical similarities, describing the main wood characteristics and properties responsible for the wood variability, and referring to lesser-known species as alternatives for CITES-listed species such as *Cedrela odorata* and *Dalbergia melanoxylon*.

The eco-valorization of the renewable resources based on invasive species such as the Scotch broom, *Cytisus scoparius* (L.) Link, was addressed by Cruz-Lopes et al. [7], who studied the chemical composition of the branches from shrubs growing in Portugal to evaluate the potential for liquid mixture conversion and improvement regarding the further manufacture of valuable products, namely, as suggested by the authors, alternatives for petroleum-derived fuels. According to the authors, the results were promising for industry processing; they exclude the time-consuming and complex transformation of the shrubs to dust, in contrast to what is typically expected of these heterogenous lignocellulosic materials.

The chemical and anatomical characterization of stems from Asparagaceae species, comprising *Agave* spp., *Beaucarnea gracilis* Lem., *Furcraea longaeva* Karw. and Zucc., *Nolina excelsa* García-Mend. and E. Solano, and *Yucca* spp., widely distributed in Mexico, have not yet been studied, as indicated by Maceda et al. [8], despite the potential of these succulent species suggested by their resistance to drought and extreme temperatures. Structural heterogeneity was found between the different species but above all, the findings related to tissue distribution, fiber characteristics, and crystallinity indices suggest a potential for biofuel and lignocellulosic materials production [8].

Temperate species such as *Tilia amurensis* Rupr., *Tilia mandshurica* Rupr., and Maxim. have garnered significant commercial interest in China owing to their stemwood, while less interest has been given to their branchwood's potential, which could play a crucial role as sustainable forest resources in light of the current wood shortage in the country [9]. The authors found different degrees of suitability for each species, noting the high potential of branchwood from *Tilia amurensis* in mechanical pulp yield with specific requirements.

Four tropical timber wood species (*Daniellia oliveri*, *Isoberlinia doka*, *Khaya senegalensis*, and *Pterocarpus erinaceus*) from Mali, Africa, were studied by Traoré and Cortizas [10] in an effort to further our understanding of the effects of environmental factors on wood characteristics and chemical properties, including wood colour, which is less studied in comparison with tree growth markers. The results showed that tree species were not equally affected by the different local environmental conditions, and extractive compounds

potential as markers by which wood from different provenance areas may be differentiated [10].

The Chinese weeping cypress (*Cupressus funebris* Endl.) is one of the representative evergreen coniferous species in China's subtropics under wood production management [11]. The effects of different type of knots, live and dead, on the physical properties and colour of this wood were discussed by Lyu et al. [11], and different commercial applications were suggested for clear wood and for wood with different knot presences. Moreover, the use of colorimetry methods allowed for the differentiation of different knot presences in wood [11].

Our hope is that this Special Issue will be of interest not only to researchers but also to students, forest managers, industrial practitioners, and society in general.

The editors are grateful to the authors and reviewers for their patience, especially during our illness periods, as well as for their confidence and assistance in the significant improvements made to the manuscripts contained herein.

**Author Contributions:** Conceptualization, V.S.; writing—original draft preparation, V.S.; writing—review and editing, V.S., I.M., T.Q. and H.P.; funding acquisition, V.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by funding to Centro de Estudos Florestais (UIDB/00239/2020) from Fundação para a Ciência e a Tecnologia (FCT), Portugal. The first author also acknowledges a research contract (DL57/2016/CP1382/CT0004).

**Conflicts of Interest:** The authors declare no conflict of interest.

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