Effects of Timber Harvesting Methods On The Nutrient Supply of Forest Soils and Recommendation Tools

Introduction Sustainability focuses more and more on cascade using of timber. In the last years especially, timber construction made big steps. Higher und bigger wooden houses are constructed. Besides, due to the transformation of the energy system in Germany the need of wood for combustion increased, too. On the other hand, the environmental requirements as nutrients and soil protection gains importance. It is often demanded to connect timber harvesting with nutrients sustainability. The effects on the nutrient balance should also be taken into account in situations that require rapid timber harvesting measures, such as windthrows and bark beetle outbreaks. To archive this the project “Nutrient saving Forestry” was conducted.

Methods and Material In the research project “Nutrient saving Forestry” a system to improve timber harvesting by focusing on nutrient protection was developed for Bavaria. It compares two different silvicultural systems, state-owned and large privately owned forests versus small privately owned forests. On top, different harvesting methods were considered. In the project course forest growth, nutrient requirements, site class, harvesting cycles (rotations period and frequency of thinning), deposition, water balance e.g., water regime, the equipment of soil with nutrients, soil chemistry and mineralogy, physical soil characteristics were included. These parameters were implied in modelling weathering rates and nutritional balances. Data were obtained from the “Bavarian Site Information System” (BaSIS) and for nutrient content of tree compartments all over Bavaria from different monitoring sources and projects. For modelling the weathering process the modelling program PROFILE 4.2. (Becker 1999, Sverdrup and Warfvinge 1993, Sverdrup et al. 1995) was used. The project focused on the supply with base, also on phosphorous.

Results Thus, for each region and each forest site in Bavaria, based on detailed high-resolution maps, the consequences of the different silvicultural systems, forest management and harvesting scenarios, their impact for the nutrient reservoir of the soil, the delivery of weathering is quantified. Alternative scenarios are shown, and recommendations for forest practitioners and decision makers are given.

Reference List Becker, R. (1999): Critical Load-PROFILE 4.2 Dokumentation (Deutsche Version). Sverdrup, H.; Warfvinge, P. (1993): Calculating field weathering rates using a mechanistic geo-chemical model PROFILE. In: Applied Geochemistry 8 (3), S. 273–283. DOI: 10.1016/0883-2927(93)90042-F. Sverdrup, H.; Warfvinge, P.; Blake, L.; Goulding, K. (1995): Modelling recent and historic soil data from the Rothamsted Experimental Station, UK using SAFE. In: Agriculture, Ecosystems & Environment 53 (2), S. 161–177. DOI: 10.1016/0167-8809(94)00558-V.