Sampling forest tree regeneration with a transect approach

A new transect approach for sampling forest tree regeneration isdeveloped with the aim to minimize the amount of field measurements, and to produce an accurate estimation of tree species composition and density independent of tree height. This approach is based on the “probability proportional to size” (PPS) theory to assess heterogeneous vegetation. This new method is compared with other approaches to assess forest regeneration based on simulated and measured, real data. The main result is that the transect approach requires about 50% of the time to assess stand density as compared to the plot approach, due to the fact that only 25% of the tree individuals are measured. In addition, tall members of the regeneration are counted with equal probability as small members. This is not the case in the plot approach. The evenness is 0.1 to 0.2 units larger in the transect by PPS than in the plot approach, which means that the plot approach shows a more homogeneous regeneration layer than the PPS approach, even though the stand densities and height distributions are similar. The species diversity is variable in both approaches and needs further investigations

Die PPS-Transektenmethode zur Erfassung von Verjüngungen

Die Inventur der Verjüngungsschicht ist meist zeitintensiv und erfolgt auf der Grundlage von Probefl ächen mit einem festen Flächenbezug, innerhalb denen alle Bäume aufgenommen werden. In dieser Arbeit wird ein Transektenverfahren vorgestellt, mit dessen Hilfe der Zeitaufwand einer Verjüngungsinventur stark verringert werden kann

Scaling wood volume estimates from inventory plots to landscapes with airborne LiDAR in temperate deciduous forest

Background Monitoring and managing carbon stocks in forested ecosystems requires accurate and repeatable quantification of the spatial distribution of wood volume at landscape to regional scales. Grid-based forest inventory networks have provided valuable records of forest structure and dynamics at individual plot scales, but in isolation they may not represent the carbon dynamics of heterogeneous landscapes encompassing diverse land-management strategies and site conditions. Airborne LiDAR has greatly enhanced forest structural characterisation and, in conjunction with field-based inventories, it provides avenues for monitoring carbon over broader spatial scales. Here we aim to enhance the integration of airborne LiDAR surveying with field-based inventories by exploring the effect of inventory plot size and number on the relationship between field-estimated and LiDAR-predicted wood volume in deciduous broad-leafed forest in central Germany. Results Estimation of wood volume from airborne LiDAR was most robust (R2 = 0.92, RMSE = 50.57 m3 ha−1 ~14.13 Mg C ha−1) when trained and tested with 1 ha experimental plot data (n = 50). Predictions based on a more extensive (n = 1100) plot network with considerably smaller (0.05 ha) plots were inferior (R2 = 0.68, RMSE = 101.01 ~28.09 Mg C ha−1). Differences between the 1 and 0.05 ha volume models from LiDAR were negligible however at the scale of individual land-management units. Sample size permutation tests showed that increasing the number of inventory plots above 350 for the 0.05 ha plots returned no improvement in R2 and RMSE variability of the LiDAR-predicted wood volume model. Conclusions Our results from this study confirm the utility of LiDAR for estimating wood volume in deciduous broad-leafed forest, but highlight the challenges associated with field plot size and number in establishing robust relationships between airborne LiDAR and field derived wood volume. We are moving into a forest management era where field-inventory and airborne LiDAR are inextricably linked, and we encourage field inventory campaigns to strive for increased plot size and give greater attention to precise stem geolocation for better integration with remote sensing strategies

Externe ökologische Folgen von Flächenstilllegungen im Wald

ln der Nationalen Strategie zur Biologischen Vielfalt [2] wurde als Ziel festgelegt, 5 % der Waldfläche Deutschlands aus der Bewirtschaftung zu nehmen und einer natürlichen Entwicklung zu überlassen. Bei Zertifizierung werden gegebenenfalls zusätzliche Stilllegung und waldbauliche Maßnahmen gefordert, Zugleich soll mit Holz umweltschonend gebaut und Energie erzeugt werden, Wird mehr Holz benötigt als auf der nach der Stilllegung verbliebenen Fläche genutzt werden kann, muss es impoftiert werden. Die ökologischen Folgen dieser lmporte werden jedoch leicht unterschätzt oder gar ignoriert

Bestandsentwicklung und Kohlenstoffspeicherung des Naturwaldes ''Schönstedter Holz" im Nationalpark Hainich

The present publication describes the stand development and the carbon storage of the naturalforest "Schonstedter Holz" at the Nationalpark Hainich. An area of 109 ha was researched in a systematic sample point inventory with a net of 100 x 100 m. The Schonstedter Holz shows a natural tree species composition with dominate beech. The compact wood volume is 497 m(3) ha(-1), the volume of coarse woody debris is about 40 m(3) ha(-1). The number of steins decrease exponentially with increasing breast heigh diameter. On a large area there is a distinct horizontal distribution of it multi-layered forest. At the research area are 10 tree species. With increasing tree species diversity decrease the compact wood volume. The single-tree forest dynamic of natural beech forest is clarified through a single-tree oriented analyses of tree damages, vitality and tendency of development. Information of 25 sample points from the year 2000 arc available. The annual increment of compact wood volume is here 10,3 m(3) ha(-1) and 2,1% of the compact wood volume respectively. The C-storage in stern, branches and roots are 244 t ha(-1). The futural forest dynamic of the Schonstedter Holz is uncertain. As a result of distinct symptoms of old age in the mixed tree species there will be a homogenisation for the benefit of beech. The regeneration is also dominated by beech, and it is not clear how far this is a result of a high roe deer population or availability of light. [References: 40