Comparing cork quality from Hafir-Zarieffet mountain forest (Tlemcen, Algeria) vs. Tagus basin Montado (Benavente, Portugal)

Abstract

In the southwestern Mediterranean Basin, cork oaks (Quercus suber L.) are periodically harvested for their cork. This natural product is valued by its homogeneity which heightens the importance of characterizing cork tissue discontinuities, or cork pores. Cork porosity profile in natural cork planks has been reported to be affected by forest management practices but, so far, has been scarcely addressed. We characterize the cork porosity profile in two contrasting cork oak woodland; at a mountain forest, in Western Algeria (absence of forest management) and at a peneplain “montado,” in southern Portugal (intensively managed toward the optimization of cork production). Image analysis techniques were applied on transverse sections of more than 40 cork samples from both woodland, and a stepwise discriminant analysis was used to discriminate between the cork pore features data-sets. Cork porosity profiles were similar between regions but; in the cork samples from Algeria, cork pores were having higher values for linear dimensions of pores (length and perimeter) and contrasting shape values (roundness) which depreciate cork quality, when compared to the cork samples from Portugal. However, improved woodland management strategies at Algeria should ensure adequate cork homogeneity and suitability for more valuable cork products.

Keywords:

• Quercus suber L.
• cork oak
• Mediterranean Basin
• cork porosity
• image analysis
• lenticular channels
• stepwise discriminant analysis

Public Interest Statement

Cork is the outer bark of cork oak trees; one natural product generating US $2 billion annually, and, currently, the sixth most valuable global non-timber forest product. Cork oaks are strictly distributed in the western Mediterranean Basin, between the southwestern Europe and northern Africa. An increasingly important challenge for the later region is to apply adequate forest management practices toward the optimization of high-quality cork production. In their research, authors assessed cork quality of two contrasting cork-producing regions: Portugal, the world leader in cork production; and Algeria, one potential cork-producing region. Results showed strong similarities between cork quality profiles, but higher cork quality heterogeneity at Algeria. Clearly, at this region, adequate forest management practices such as thinning (for selecting the best cork-producing trees) or pruning (for optimizing trees’ cork-harvesting surface), and appropriate cork-harvesting cycles should improve the cork yield and quality, at medium term.

Competing Interests

The authors declare no competing interest.

Acknowledgments

Authors acknowledge the collaboration of Beni Mester Cork Industry (Hafir-Zarieffet, Algeria) and of Companhia das Lezírias, S.A. (Benavente, Portugal) for the implementation of the study areas. Authors acknowledge the comments of two anonymous reviewers.

Additional information

Notes on contributors

Amina Ghalem

The authors were motivated by the spatial variability of cork oak woodland across Mediterranean environments, the implications in the cork yield, and cork quality and, consequently, in the economic and ecological sustainability of these sensitive forest ecosystems. Authors used image analysis techniques to study cork porosity in cork planks, in a similar way that cork industry detects cork porosity in cork products such as natural cork stoppers and disks, the most valuable cork product in the cork industrial processing.

This study will be one first original report from a young research group, integrating young MSc and PhD students from the Center for Environmental and Sustainability Research (NOVA University of Lisbon, Portugal) and Tlemcen University (Algeria) (http://www.augustacosta.net/people.html) addressing a comprehensive understanding on cork planks quality and cork oak woodland management, working at INIAV, I.P.