Accessibility of the Swiss forest for economic wood extraction (2021)

Two raster maps (10m resolution) of: I) the most suitable extraction method for wood in the Swiss forest, and II) the overall suitability of the Swiss forest for economic wood extraction and transport.
A modern forest road system is important for the efficient management of forests. In order to assess the current forest accessibility in Switzerland on a comprehensive basis, the entire Swiss forest was investigated using a consistent methodology. In our model, wood extraction from the stand to the road and on-road transport are analysed in combination.
Suitable extraction methods for each forest parcel (10m x 10m) were determined using an approach in which ground-based, cable-based and air-based transport are distinguished. First, the areas for ground- and cable-based extraction were delineated. The trafficability of the forest areas was assessed based on the terrain and soil characteristics; trafficable areas also had to be connected to a forest road. To evaluate the suitability for cable-yarding (up to a maximum distance of 1500 m), terrain and possible obstacles (e.g., power lines) were considered. The remaining forest area, which was not suitable for either ground-based or cable-based methods, was assigned to the "helicopter" category. As a result of this analysis, a map of the most suitable skidding method for each plot could be created. When several methods were possible for a parcel, the priority was ground-based over cable-based over air-based.
Road transport was investigated using network analysis, based on the data set "Forest access roads 2013" from the Swiss National Forest Inventory (NFI), which contains information on width and weight limits of roads in the forest and up to the superordinate main road network. Thus, in addition to the distance, the largest type of vehicle allowed on the respective removal route could also be taken into account.
Based on the extraction method and the weight limits for on-road transport, the forest area was divided into three categories: 1) meets the requirements for efficient forest management (all forest parcels with ground-based extraction method or mobile cable-yarding, transport weight limit at least 28 tons); 2) limited suitability for efficient forest management; and 3) not suitable for efficient forest management (forest parcels in the "helicopter" category or transport with trucks under 26 tons).
The resulting maps cannot provide an accurate classification for each forest parcel. Missing or incorrect roads in the road dataset, insufficient information on ground trafficability or other local factors, the limitation to only three possible extraction systems, and failure to account for anchor trees, extraction methods changing over small distances, and unrealistically short cable-yarding distances can cause the model results to deviate from the assessment by an expert with knowledge of the local conditions. Also, protected areas were not excluded and harvesting intensity was not taken into account. The advantage of the method is that consistent criteria are used for the entire Swiss forest, making the results comparable throughout Switzerland.
The data are managed at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and are available to third parties on request. (NFI data policy: https://www.lfi.ch/dienstleist/daten.php)
Input data used:
- Forest road dataset of the NFI4 (only truck roads from 3.0 m width and 26 t carrying capacity) (2016).
- NFI forest mask, 10 m resolution (2015)
- Digital elevation model, 10m resolution (based on swissALTI3D 2016)
- Slope map, 10m resolution (based on swissALTI3D 2016)
- Soil suitability map, 10m resolution (based on soil suitability map BFS 2000)
- Obstacles for cable lines, 10m resolution (buildings, major roads, power lines, railroads, based on swissTLM3D 2016)

两张分辨率为10米的栅格地图，分别为：I）瑞士森林中木材最适宜的采伐方法；II）瑞士森林在经济木材采伐与运输方面的总体适宜性。
现代化的森林道路系统对森林的高效管理至关重要。为全面评估瑞士当前的森林可达性，研究人员采用统一方法对整个瑞士森林进行了调查。本模型综合分析了从林分至道路的木材采伐环节以及道路运输环节。
针对每个10米×10米的森林地块，研究通过区分地面、缆索及航空运输方式，确定了适宜的采伐方法。首先，划定了地面及缆索采伐的适用区域；基于地形与土壤特征评估森林区域的通行性，且通行区域需与森林道路相连。在评估缆索集材（最大距离1500米）的适宜性时，考虑了地形及潜在障碍（如电力线）。未被地面或缆索方法覆盖的剩余森林区域则归为“直升机”类别。通过该分析，生成了每个地块最适宜集材方法的地图；若某地块存在多种可选方法，则优先级依次为地面运输＞缆索运输＞航空运输。
道路运输研究基于瑞士国家森林资源清查（NFI）的“2013年森林通路数据集”，采用网络分析方法开展；该数据集包含森林道路及上级主干道网的宽度与载重限制信息。因此，除距离外，还可考虑各运输路线允许通行的最大车辆类型。
基于采伐方法与道路运输载重限制，森林区域被划分为三类：1）满足高效森林管理要求（采用地面采伐或移动缆索集材的地块，运输载重限制不低于28吨）；2）高效森林管理的适宜性有限；3）不适用于高效森林管理（归为“直升机”类别的地块，或使用载重低于26吨卡车运输的地块）。
生成的地图无法对每个森林地块进行精准分类。道路数据集缺失或错误的道路信息、地面通行性数据不足或其他局部因素、仅局限于三种采伐系统、未考虑锚树、小范围采伐方法变化及不切实际的短缆索集材距离等因素，均可能导致模型结果与熟悉当地情况的专家评估存在偏差。此外，研究未排除保护区，也未考虑采伐强度。该方法的优势在于，对整个瑞士森林采用统一标准，使结果在全国范围内具有可比性。
数据由瑞士联邦森林、雪和景观研究所（WSL）管理，第三方可按需获取。（NFI数据政策：https://www.lfi.ch/dienstleist/daten.php）
所用输入数据包括：
- NFI4森林道路数据集（仅包含宽度≥3.0米、载重≥26吨的卡车道路，2016年）
- NFI森林掩膜，分辨率10米（2015年）
- 数字高程模型，分辨率10米（基于swissALTI3D 2016）
- 坡度图，分辨率10米（基于swissALTI3D 2016）
- 土壤适宜性图，分辨率10米（基于瑞士联邦统计局2000年土壤适宜性图）
- 缆索障碍图，分辨率10米（包含建筑、主干道、电力线及铁路，基于swissTLM3D 2016）