Characteristics of deadwood and implications for biodiversity in Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) planted forests in Italy

Abstract

The aim of the present study is to define a set of indicators to measure the stand diversity of Douglas fir planted forests with special regard to deadwood attributes related to biodiversity conservation. The set of quantitative and qualitative indicators was implemented in a Douglas fir stand in Central Italy (Rincine forest, Tuscany region) realized on degraded Sweet chestnut stands and abandoned agricultural lands from late ‘60s to first ‘80s. The identified indicators include two stand indicators (trees species composition and horizontal stand structure) and five deadwood indicators (total deadwood volume divided in coarse woody debris and fine woody debris, deadwood diversity by species and decay class, and number of habitat trees). The results show that the Douglas fir stand in the Rincine forest is characterized by a high number of Douglas fir trees (88.6% of stem density, 94.0% of basal area) with some young broadleaved trees and ancient Sweet chestnut trees prior to reforestation (Shannon index of 0.2 ± 0.34 and Diameter differentiation index of 0.20 ± 0.09). The deadwood indicators highlight a total volume of 62.0 m3 ha−1 mainly consisting of coarse woody debris (86.4% of total volume) and a diversified distribution by species (Shannon index of 0.29 ± 0.33) and decay class (Shannon index of 1.30 ± 0.10). The set of indicators proposed in this study can be implemented in other planted forests with the aim to monitor changes in stand diversity over time by forest managers.