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 m3 ha−1, 8.84 m3 ha−1 and 4.03 m3 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.
Highlights
Coarse woody debris (CWD) plays an important role in supporting biodiversity [1] and assisting ecological processes [2]
The plots were associated with one of the three human accessibility classes (HAC) and the slightly lower stand volume was observed in the medium accessibility class (MAC) (Table 4)
The effect of human accessibility level on the volume and characteristics of CWD in the Hyrcanian forests of Iran was investigated, demonstrating that extraneous interventions in the forest management alter the characteristics of CWD
Summary
Coarse woody debris (CWD) plays an important role in supporting biodiversity [1] and assisting ecological processes [2]. CWD is produced by natural processes such as tree mortality and Forests 2018, 9, 509; doi:10.3390/f9090509 www.mdpi.com/journal/forests. Forests 2018, 9, 509 decomposition, depending on site productivity and in managed forests, even throughout silvicultural activities. Sometimes the involvement of local people intervenes modifying the expected distribution of CWD components. CWD was reported as an important environmental element and essential for maintaining biodiversity in forests [3,4,5]. CWD is used by local people as fuel wood, one of the primary energy source and the demand for fuel wood over the few years in these forests is certain to increase [6]. In the Hyrcanian forests of Iran, there are approximately 3400 villages for about 74,000 households, whose annual consumption of wood is between 1.44 and 2.22 million m3 , for heating, cooking and other uses [6]
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