Tree Species Richness and Stand Productivity in Low-Density Cluster Plantings with Oaks (Quercus robur L. and Q. petraea (Mattuschka) Liebl.)

Somidh Saha,Jürgen Bauhus,Christian Kuehne

doi:10.3390/f4030650

Abstract

Low density plantings complemented by natural regeneration is an increasingly common reforestation technique to ensure growth of a sufficient number of trees from desired species while maintaining natural processes such as succession. One such form of low density planting that aims at lowering establishment costs—oak clusters—has been developed as an alternative to row planting since the 1980s in central Europe. However, whether cluster planting provides higher species richness and productivity than high density row planting has not previously been analyzed. Here, we compare tree species richness and productivity (measured as stand basal area) between oak cluster plantings and conventional row planting in young (10–26 years old) forest stands at seven study sites in Germany. Tree species richness was significantly higher in cluster plantings than in row plantings, whereas total basal areas were comparable. Naturally regenerated trees contributed on average to 43% of total stand basal area in cluster plantings, which was significantly higher than in row plantings. Total stand basal area in cluster planting was significantly related to the density of naturally regenerated trees. In turn, tree species diversity, density and basal area of naturally regenerated trees were increased with the size of unplanted area between clusters. Our results demonstrate that the admixture of naturally regenerated, early and mid-successional tree species compensates for a possible loss in productivity from planting fewer oaks. Low density cluster plantings can offer significant environmental benefits, at least for the first few decades of stand development, without compromising productivity.

Highlights

Traditional reforestation methods following disturbances or clear felling have aimed to assert fast control of forest sites through planting of desired tree species [1]
This higher species richness in cluster plantings compared to row plantings was more prominent in nest than in group plantings (Figure 3)
Our study provides the first assessment of tree species diversity and stand productivity in low-density cluster plantings established in wind-thrown and clear-felled areas across a number of sites

Summary

Introduction

Traditional reforestation methods following disturbances or clear felling have aimed to assert fast control of forest sites through planting of desired tree species [1]. This approach comprises a number of disadvantages such as high costs for site preparation, planting stock and planting [2,3]. A third way for the reforestation of disturbed or harvested sites consists of a combination of the two approaches; low-density planting with natural regeneration in the remaining area [1] This approach ensures a certain proportion of desired species in the future stand while maintaining natural processes and new species combinations at reduced costs, compared to conventional planting. Given the increasingly important production of biomass from forests for energy and solid-wood products, silvicultural systems must use the available net production area most efficiently

Methods

Results

Discussion

Conclusion