Fig. 1: BWI3 field working (Photo: W. Scholtes)
BWI is a joint task force of federal and state forest authorities and is implemented according to the Federal Forest Act in a 10-year cycle. The states are in charge of data collection. In Baden-Württemberg the Forest Research Institute, FVA, is responsible managing survey data. Data collection took place in 2011 and 2012. Altogether, ten field crews measured and recorded much data on 13,232 plots, which yielded a comprehensive pool of facts and figures about forest conditions.
In Baden-Württemberg, the three surveys cover a period of 25 years – from 1987 to 2012 – and provide an overview of forest development, which exhibits remarkable dynamics. Forest cover has increased slightly, which demonstrates that forest patrimony has been preserved – a success of forest protection by the Federal Forest Act in a densely populated country with continued high land use.
Forest conditions described in the 2012 inventory confirm trends at state and federal levels that already were noticed 10 years ago in the 2nd survey. The proportion of conifers continues to decline, especially Norway spruce and Scots pine, with a corresponding increase in the proportion of deciduous tree species, which now occupy 47 % of forest land area. Growing stock continues to rise and has reached 499 million m³ solid volume over bark, 377 m³ per hectare, and stocks of large dimension timber (trees with a minimum diameter at breast height of 50 cm over bark) also continue to increase. Simultaneously the ecological quality of the forest as a living environment has improved as indicated by increased species diversity leading to a tree species composition that is close to natural forest conditions. Deadwood stocking has increased as well, albeit moderately. Only mean volume increment over the period from 2003 to 2012 has decreased compared to the preceding period 1987 to 2002. Previously periodic volume increment reached 13.8 m³ per year per hectare, but now it has decreased to 12.3 m³ per hectare per year. Nonetheless, this lower increment is still the highest compared to the other federal states in Germany. The reason for this reduction is the decrease in the proportion of fast growing younger age classes of conifers (now stands are older, the proportion of conifers has decreased). Moreover there might have been a climatic influence at the beginning of the period; the very dry year 2003. Generally, we have been observing a long-term decrease of diameter growth in spruce and beech on experimental plots.
The most important results of the BWI were presented to the forest expert community in a colloquium held at FVA in Freiburg on October 29th, 2014.
One conclusion was that the results of the BWI substantiate the concept of close to nature forest management as practiced in Baden-Württemberg and demonstrates that foresters are on the right track. However, there were other differing views of the results. From a silvicultural point of view, the decrease of conifer proportions is an opportunity to rethink the future of conifer development and to reverse this downward trend by silvicultural means to ensure a long-term supply of raw material for the wood industry, which mainly depends on softwood.
Fig. 2: Uptake of probe points (Photo: F. Frech)
Fig. 3: Digital data entry (Photo: F. Frech)
A stakeholder of nature conservation and one from timber industry gave statements at this colloquium and it became evident from these statements that despite the general favorable development of forest conditions, not all desires may be satisfied. For instance, the result that as forests become older trees get larger can be interpreted in different ways. While the nature conservationist is satisfied with this consequence, wood industry representatives are not and are very skeptical about whether the supply of the needed variety of wood dimensions will be assured in the long run. Thus the same consequence is interpreted contrarily: for nature conservationists the forest should become even older and trees much larger, whereas wood consumers see a “demographic” problem because forests are too old and trees too large! Wood consumers are critical of decreasing softwood stocks because sawmills heavily depend on small and medium-sized softwoods, especially spruce wood.
These contrary viewpoints unveil conflicts of goals, which constitute a big challenge for forest policy makers and forest service managers to satisfy all forest functions while managing the forest in a way that maximizes the benefit of the forest to all of society. Given these partly opposed demands on forests it becomes obvious how important figures are which – despite contrary interpretation - contribute to objectification and thereby can form the basis for rationale decision making.
I need to close with a remark regarding possible misunderstandings and discrepancies when interpreting the results of the BWI. The data document favorable forest conditions as a result of forest management. However, to conclude that forests are doing well regarding their ecosystem state is not supported. Recently published results of the annual forest health survey suggest that there are still risks for vitality and stability of the forests, which is cause for concern in the face of imminent climate change since vitality is crucial for the forests’ ability to adapt to changing environmental conditions.