Density, extractives and decay resistance variabilities within branch wood from four agroforestry hardwood species F Terrasse, L Brancheriau, R Marchal, N Boutahar, S Lotte, D Guibal, L Pignolet, K Candelier To cite this version: F Terrasse, L Brancheriau, R Marchal, N Boutahar, S Lotte, et al.. Density, extractives and decay resistance variabilities within branch wood from four agroforestry hardwood species. iForest: Bio- geosciences and Forestry, Italian Society of Silviculture and Forest Ecology, 2021, 14 (3), pp.212-220. 10.3832/ifor3693-014. hal-03224030 HAL Id: hal-03224030 https://hal.archives-ouvertes.fr/hal-03224030 Submitted on 11 May 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Research Article ii FF o o r r e e s s t t doi: 10.3832/ifor3693-014 Biogeosciences and Forestry vol. 14, pp. 212-220 Density, extractives and decay resistance variabilities within branch wood from four agroforestry hardwood species Florence Terrasse (1-2), Agroforestry practices like pruning trees to control the light flux to crops pro- Loic Brancheriau (1-2), duce every year a large volume of branches which is valorized by farmers as mulching or energy fuel. However, according to the literature, the wood of (3) Remy Marchal , branches shows higher rates of polyphenols than stem wood and this can open Nabila Boutahar (1-2), some new perspectives for branch exploitation. In this study, the wood proper- Sylvain Lotte (1-2), ties (density, mechanical properties, extractive content and decay resistance) (1-2) were determined on branches of different sizes from oak, chestnut, poplar Daniel Guibal , and walnut trees collected in two agroforestry systems. These properties were Luc Pignolet (1-2), evaluated according to the wood age and the sampling position along the radial Kevin Candelier (1-2) and longitudinal axes of the branch. All samples were analyzed by NIR-Spec- troscopy and a predicting model aimed to assess the branch wood properties has been developed. Wood characteristics largely vary between species and do not exactly follow the same trends from one species to another. Overall, hard- wood density of branches is similar to that of trunks, the content in wood ex- tractives follows similar evolutions, and the decay resistance of branch wood does not seem to be really impacted by its position along the branch. Reliable NIRS models were built to easily predict the wood density and extractives con- tent of agroforestry branches. The extractives content and the decay resis- tance of branch hardwood appear to be substantially lower than those of trunks, which suggests a non-suitability of branch wood for developing high- valued green chemistry. Keywords: Agroforestry, Branches, NIR-Spectrometry, Wood Quality Introduction 1991), biodiversity conservation (Michon & large amounts of carbon, thereby contrib - In many tropical countries, agroforestry De Foresta 1992) and above all in climate uting to mitigate the effects of climate systems provide both services for agricul- change mitigation (Hamon et al. 2009). change and providing a highly valuable ture and for non-food economic sectors Agroforestry trees differ from forestry woody resource to be used for various pur- (housing and energy). Agroforestry is de- trees in two ways: their roots dig deeper poses. Since six decades, European coun- fined as any landscape use system associat- (Mulia & Dupraz 2006), and they also grow tries (including France) have massively ex- ing trees or any other ligneous perennial faster and produce more biomass, most cluded trees from the cropfields in order to plants with animal and/or vegetal produc- likely because there is less competition for intensify mechanized agriculture. However, tions on the same surface unit (Nair 1990). the light and other resources (Dupraz & the current agro-ecological transition is go- Such a system provide not only environ- Liagre 2008). In addition, agroforestry ing to reverse this trend through the de- mental but also economic and social bene- trees usually grow in more fertilized soils sign of new agroforestry systems. fits to farming communities (Nair 1993, than those of forest trees. In some cases, Besides agricultural products, the main Sanchez 1995). Agroforestry play an impor- an agroforestry tree will produce about product specific to agroforestry systems is tant role in pests and pathogens control three times more biomass than a tree of wood. Trunks, branches and twigs all (World Agroforestry Centre – Jamnadass et the same age in a forest (Gavaland & Bur- have different potential uses due to their al. 2013), food security (Guitton 1994), soil nel 2005). This increased biomass enables diverse characteristics (ADEME/Atlanbois protection and natural amendment (Young agroforestry trees to potentially stock 2016) which are summarized in Fig. S1 (Sup- plementary material). Throughout their life cycle, agroforestry trees mostly yield prun- (1) CIRAD, Research Unit BioWooEB, 34000, Montpellier (France); (2) BioWooEB, Université ing wood from branches, which has the de Montpellier, CIRAD, Montpellier (France); (3) “Arts et Metiers” Institute of Technology, same wood orthotropic cylindrical organi- LABOMAP, HESAM University, F-71250 Cluny (France) zation as trunks (Fig. S1) and currently is mostly used as Ramial Chipped Wood @ Kevin Candelier ([email protected]) (RCW) or animal litter (Malignier & Bala- guer 2017). Received: Nov 09, 2020 - Accepted: Mar 01, 2021 Branch wood has been poorly investi- gated compared to stem wood, and cur- Citation: Terrasse F, Brancheriau L, Marchal R, Boutahar N, Lotte S, Guibal D, Pignolet L, rently there is a lack of data which could Candelier K (2021). Density, extractives and decay resistance variabilities within branch support any potential added-value of the wood from four agroforestry hardwood species. iForest 14: 212-220. – doi: 10.3832/ifor3693- branches for any production path. 014 [online 2021-05-02] Regarding the physical aspects, some studies reported that the mechanical char- Communicated by: Luigi Todaro acteristics of branches’ wood are usually reduced compared to those of the trunks © SISEF https://iforest.sisef.org/ 212 iForest 14: 212-220 Terrasse F et al. - iForest 14: 212-220 y properties were then compared to those r Fig. 1 - Sam- t of wood from the trunk of the same trees. s pling, pro- e Additionally, all samples were analyzed by r cessing and o NIR-Spectroscopy with the aim of develop- F selection of ing a fast system to assess the branch d wood sam- wood properties directly in the field. n ples. a s e Material and methods c n e Tree selection i c The selected hardwoods species were s o sweet chestnut (Castanea Sativa Mill.), pe- e dunculate oak (Quercus robur), hybrid wal- g o i nut (Juglans × intermedia [C. DC.] Carrière, B hybrid Juglans nigra × Juglans regia) and hy- – brid poplar (Populus generosa Henry). t s Chestnuts and oaks were sampled near e r Fougères, France (48° 21′ 05.62″ N, 01° 12′ o 16.65″ W), while poplars and walnuts were F i sampled near Alès, France (44° 07′ 37.934″ N. 04° 05′ 0.067″ E). The sampled chestnuts and oaks were planted as grasslands’ hedges, whereas walnuts and poplars were planted within grasslands plots (intraplot). The selected trees were sampled in Feb- ruary 2019 to limit the seasonal impact on wood chemical composition (i.e., starch in sapwood). A total of 9 trees were sampled from which 15 branches were taken (one to three branches per tree). The details are summarized in Fig. 1. For each species, the harvested branches were split in three sectors according to their distance to the tree trunk. The three branch sectors were defined as follows: (Gurau et al. 2008). Other researchers in- These are non-structural wood cell compo- • Sector 1: 100% of the branch diameter at vestigated the density and anatomy of nents of low molecular weight which act as the knot’s level; branches in several species (Dadzie et al. natural chemical products mainly protect- • Sector 2: 70-90% ± 3% of the branch diam- 2016, Kiaei et al. 2014), finding that in most ing lignocellulose from fungal and micro- eter at the knot’s level; cases the wood density of branches seems bial attacks (Pecha & Garcia-Perez 2015). • Sector 3: 40-70% ± 5% of the branch diam- to be higher than that of the trunks. Yet, This study investigated the potential of eter at the knot’s level. this characteristic, as most of other wood branch wood from agroforestry practices A total of 45 branch sectors were sam- characteristics, seems to be highly variable as base material to develop green chem- pled. The age of the branch wood is re- depending on the tree species considered. istry and/or to manufacture biomaterials. ported in Tab. 1, according to the tree spe- Such differences also appear when consid- Farmers prune their trees every year to cies and the branch sector. Based on these ering wood chemical properties, which manage light reaching the ground, and the data, we supposed than the majority of strongly change moving from one tree or- harvested biomass can help improve the wood samples is mainly composed by sap- gan to another. Tree knots along the stem economic model of agroforestry plots. To wood portion or sometimes by transition have been particularly studied, resulting in test the suitability of such a woody bio- wood, as for example in sector 1 for chest- most cases richer in extractives than trunks mass to the above goals, wood physical nut.