Coarse Woody Debris Variability Due to Human Accessibility to Forest

Abstract

Coarse woody debris (CWD) plays an important role in supporting biodiversity and assisting ecological processes. Sometimes local people intervene modifying the expected distribution of CWD components, harvested as fuel wood. The effect of the human accessibility (HA) on the volume and characteristics of CWD (snag, downed log and stump) was investigated in the natural uneven-age mixed hardwood stands of the Hyrcanian forests of Iran to quantify the impact on CWD. The HA was classified into three classes (easy, medium and difficult) on the basis of slope class, slope direction to the nearest road and road type. As expected, a negative relationship between the degree of accessibility was found with respect to the main qualitative and quantitative indices referring to CWD. The results showed that the volume of CWD decreased with an increase in human accessibility class (HAC), thus the mean volume of CWD in the difficult, medium and easy accessibility classes were 14.87 m 3 ha −1 , 8.84 m 3 ha −1 and 4.03 m 3 ha −1 , respectively. The decrease in CWD volume was more associated with the decreasing volume of small diameter of low decayed downed logs. The ratio of snag volume to standing volume, the ratio of downed log volume to the volume of trees and the ratio of CWD volume to standing volume increased with a decrease in HAC, while the ratio of downed log volume to snag volume decreased with a decrease in HAC. No selective behaviour on the botanical species of CWD was recorded. For ecological forest management, the effect of HAC on CWD should be considered. A constant supply of snags and downed logs must be preserved to assure a high level of biodiversity. To balance social needs and biodiversity requirements, an increased level of CWD retention might be needed in areas with easy accessibility. The obtained results may be useful when ecological and socio-economical needs have to be taken into consideration in future policy-making decisions.

Structure and Dynamics of Deadwood in Pine and Oak Stands and their Role in CO2 Sequestration in Lowland Forests of Central Italy

“…The snag creation index (RSS) generally was higher in unmanaged or in low human pressure forest, as previously reported [4,24].…”

“…Decay state of snags and logs [12,24,40] was evaluated according to physical characteristics and bark coverage that was visually estimated by following the characters synthetised in Table 1 [24]. Each snag and log sampled was assigned to one of the five decay classes (DC).…”

“…In this Mediterranean area, the possibility of a continuous accumulation of deadwood over time is usually a result of the natural disturbance and the abandonment of the timber harvest [7,[46][47][48][49][50][51] or, better, of the choice to carry out minimal interventions since the removal of deadwood has been one of the most frequent operations in forest, favoured by the rights of use of local populations for the collection of deadwood as firewood [15,24,25] and the fear of forest fires by managers. Deadwood is mainly caused by tree mortality and the accumulation is due to the production coupled with the degradation and decay of biological agents [6,[52][53][54].…”

“…It also contributes to nutrient cycles and plays a role in forest carbon sequestration [20][21][22]. The potential benefits for wildlife from the retention of deadwood depend on several environmental factors such as size, species, and level of decay [4] but also forest management, timber harvest, and human accessibility level [23,24] of the site, which can have substantial effects on CWD and snag density [15,16,[23][24][25][26]. The fundamental pre-condition for protecting biodiversity and the sustainable functioning of forest types is to maintain snags and CWD in suitable relative abundance across all decay classes [27].…”

“…In fact, senescent, dying or standing dead trees are usually harvested to maximize the commercial value of a harvest [4]. Furthermore, the total amount of deadwood can be negatively influenced by the local population that collects wood freely or by following specific regulations [15,24].…”