Towards better estimates of carbon stocks in Borneo's logged-over Dipterocarp forests

Tropical forests are a major reservoir of biodiversity and carbon (C), playing a pivotal role in global ecosystem function and climate regulation. However, most tropical forests, especially Borneo's forests in Southeast Asia, are under intense pressure and threatened by human activities such as logging, mining, agriculture and conversion to industrial plantations. Selective logging is known to reduce both above- and below-ground biomass by removing selected large trees, while increasing deadwood stocks through collateral logging damage and creating large gaps in the canopy. The extent of incidental damage, canopy opening and the rate of C recovery were shown to be primarily related to logging intensity. This thesis assesses the long-term effects of logging intensity on five main C pools in Dipterocarp forests in northern Borneo (Malinau District, North Kalimantan) along a logging intensity gradient ranging from 0 to 57% of initial biomass removed in 1999/2000. Our results showed that total C stocks 16 years after logging ranged from 218-554 Mg C/ha with an average of 314 Mg C/ha. A difference of 95 Mg C/ha was found between low logging intensity (< 2.1% of initial biomass lost) and high logging intensity (> 19%). Most C (approx. 77%) was found in living trees, followed by soil (15%), deadwood (6%) and a small fraction in litter (1%). The imprint of logging intensity was still detectable 16 years after logging. Logging intensity was thus shown to be the main driver explaining the reduction of AGC>20, BGC>20, in deadwood and total C stocks and an increase in deadwood. Our results quantify the long-term effects of logging on forest C stocks, especially in AGC and deadwood. High logging intensity (50% reduction of initial biomass) reduced total C stocks by 27%. AGC recovery was lower in high logging intensity plots, suggesting lowered forest resilience to logging. Our study showed that keeping logging intensity below 20% of the initial biomass can limit the long-term effects of logging on AGC and deadwood stocks.

Logging damage to residual trees during sustainable harvesting of uneven-age stands in the Hyrcanian forests of Iran

Background: The frequency of wounded trees and intensity of wounds during logging operations can have serious impacts on stand growth and forest sustainability. The aims of the study were to evaluate and compare stand (tree and regeneration) damage level, wound characteristics, and damage types occurring when using a cable skidder in salvage logging and selection cutting. Methods: This study was conducted on four sites of mixed uneven-aged hardwood stands in the Hyrcanian forests of Iran. At two sites, salvage logging was applied (SL1 and SL2), and low-intensity selection cutting (SC1 and SC2) was applied at the other two. A systematic plot sampling design was used on the study area for damage assessment. Results: The percentage of regenerating trees damaged was 2.8, 2.1, 4.3, 1.4 %, in SL1, SL2, SC1, and SC2, respectively. The corresponding percentage of damaged trees was 4.3, 3.7, 4.9, 1.7 %. Most of the damage (48–79%) to the stand occurred during the winching stage at all the sites. Most of the wounds were located on the bole (51–78%). The average wound height and wound size at selection cutting sites were significantly higher than at the salvage logging sites. The incidence of high-intensity wounds at the salvage logging sites (55% at SL1 and 57% at SL2) was higher than at the selection cutting sites (24% in SC1 and 30% in SC2). Regenerating beech (Fagus orienalis Lipsky) and alder (Alnus subcordata C.A.Mey) had the highest incidence of damage. The number of damaged trees increased with increasing winching distance. Conclusion: Damage levels in stands during salvage logging and low-intensity selection cutting are lower (about a quarter) than the damage level to residual trees (12–23%) and regeneration (5–11%) from conventional selection cutting in uneven-aged mixed hardwood stands in the Hyrcanian forests. Because of the ecological and conservation value of deadwood, if the incidence of wind-fallen trees is low, the wood should be left in forest stands due to the high cost of salvage logging and the damage caused to residual and regenerating trees.

A Comparative Study of Carbon Stock Changes from Different Logging Techniques in Ulu Jelai Forest Reserve, Kuala Lipis, Pahang

Conventional logging practices are often highly destructive to forest ecosystems. Heavy machinery can compact the soil and destroy vegetation. Previous research by others have demonstrated that environmental damage can be minimized through the use of site- sensitive harvesting techniques. Forest harvesting in the inland forest in Malaysia is generally carried out by a combination of crawler tractor and winch lorry, which we defined as the current logging technique. Under the current logging technique, crawler tractors are used to skid logs from felling sites to skid trails and winch lorries continue the transportation to the roadside landings. In the early nineties, a Low Impact Logging (LIL) practice using an improved logging system was carried out in some forest areas in Peninsular Malaysia. The technology, called logfisher was mainly deployed to retrieve logs from rocky and deep, narrow ravine which was deemed uneconomical, difficult and dangerous for the crawler tractor to operate. In certain logging areas in Pahang, a combination of crawler tractor and logfisher is being used which we defined in this study as LIL. The study focuses on quantifying the carbon stock changes from the different logging techniques in Lipis, Pahang. Based on preliminary results, the LIL technique showed less carbon loss if the carbon stocks before and after logging were compared. This study indicates that different logging techniques results in different impact on the total residual forest carbon stocks. The introduction of LIL systems and practices have indeed reduced the logging damage and improved stand conditions. Improvement to the current practice, enhance the productivity of the residual stand and reduce forest degradation in terms of carbon stocks as well as other ecological co-benefits.

Felling and skidding damage to residual trees following selection cutting in Caspian forests of Iran

The felling and skidding damage to residual trees was investigated in a selectively cutting operation in the Caspian forest of Iran. The logging operation was performed by chainsaw and cable skidder. Prelogging, after felling and skidding operations residual tree injuries (species, DBH and damage) were inventoried by systematic plot sampling. Two types of tree damage were observed: destroyed and injured. In this study felling operations mainly injured trees whereas skidding was the main cause of destruction. The percentage of destroyed and injured residual trees by felling operations was 1.4% and 3.4%, whereas the percentage of destroyed and injured residual trees by skid&shy;ding operations was 5.2% and 11.1%. About 87% of destroyed trees were found in the DBH class smaller than 22.5 cm. Maple and Alder were the most damaged trees among the other trees species. Damage to the lower bole and wood damaged intensity were the most common type of injury. To reduce the stand damage, skid trails should be planned before felling and felling directions should be predetermined. In the selection cutting management, limiting logging damage to residual trees must therefore remain a major objective. &nbsp; &nbsp;