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This study was carried out in a steep and difficult terrain. Trees were logged downhill to the landing by a wheeled skidder Timberjack 450C. Selection cutting was performed on a 66-hectare tract with an average slope of 30%. The elemental time study method was applied to develop the skidding time predicting model. In this study 43 working cycles were included. The skidding cycle time was mainly affected by skidding distance, winching distance and interaction between skidding distance and slope. The gross and net production rate was 20.51 and 22.93 m³/h, respectively. The unit cost considering the gross and net production rate was 6.31 and 6.22 USD/m³, respectively.

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The importance of measuring biophysical properties of forest for ecosystem health monitoring and forest management encourages researchers to find precise, yet low-cost methods especially in mountainous and large area. In the present study Geoscience Laser Altimeter System (GLAS) on board ICESat was used to estimate three biophysical characteristics of forests located in north of Iran: 1) maximum canopy height (H max ), 2) Lorey's height (H Lorey ), and 3) Forest volume (V). A large number of Multiple Linear Regressions (MLR) and also Random Forest (RF) regressions were developed using different set of variables: waveform metrics, Principal Components (PCs) produced from Principal Component Analysis (PCA) andWavelet Coefficients (WCs) generated from wavelet transformation. To validate and compare different models, statistical criteria were calculated based on a five-fold cross validation. Best model concerning the maximum height was an MLR with an RMSE of 5.0m which combined two metrics extracted from waveforms (waveform extent "W ext " and height at 50% of waveform energy "H 50 "), and one from the Digital Elevation Model (Terrain Index: TI). The mean absolute error (MAPE) of maximum height estimates is about 16.4%. For Lorey's height, a simple MLR model including two metrics (W ext and TI) represents the highest performance (RMSE=5.1m, MAPE=24.0%). Totally, MLR models showed better performance rather than RF models, and accuracy of height estimations using waveform metrics was greater than those based on PCs or WCs. Concerning forest volume, employing regression models to estimate volume directly from GLAS data led to a better result (RMSE=128.8 m 3 /ha) rather than volume-H Lorey relationship (RMSE=167.8m 3 /ha).

A field production study was conducted for a manual harvesting system using a chainsaw in a Caspian hardwood forest site. A selective cut was performed on a 42-hectare tract with an average slope of 30 percent. Felling time per tree was most affected by diameter at breast height and by the distance among harvested trees. The gross and net production rate was 20.6 m 3 and 26.1 m 3 per hour/one person, respectively. The unit cost considering the gross and net production rate was 1.05 USD/m 3 and 0.81 USD/m 3 , respectively. The significant variables included diameter at breast height (D) and distance among harvested trees (L) for the time expenditure model. This regression function is statistically significant at α = 0.01.