Removing harvest residues from hardwood stands affects tree growth, wood density and stem wood nutrient concentration in European beech (Fagus sylvatica) and oak (Quercus spp.)

Background: Higher exportation of harvest residues from forests due to increased demand for woody biomass, has reportedly diminished soil mineral resources and may lead to degraded tree nutrition as well as growth. However, as nutrients become less available in the soil, the remobilization of nutrients in biomass tissues (plant internal cycling) helps sustain tree nutrition. Our study aims to quantify the impact of Removing Harvest Residues and Litter (RHRL) during five years on tree growth, wood density, and stem wood nutrient concentrations in young beech and oak forest stands. Result: Our study found that, RHRL significantly decreased tree growth ring width by 14%, and wood density by 3%, in beech trees, in near bark rings. RHRL also significantly reduced nutrient concentration in near bark and near pith areas of both studied species. Mg, Na and S were found lower by 44%, 76%, and 56%, respectively, in near bark area of beech trees. In near bark area of oak trees, K, Ca, Mg, Na, S, and Fe were lower by 20%, 25%, 41%, 48%, 41%, and 16%, respectively. K and Mg concentrations decreased more strongly in near pith area compared to near bark area suggesting internal translocation of these two elements. Conclusion: In beech trees, wood density proved to be an important factor while quantifying the effect of removing harvest residuals on tree growth and biomass. Soil nutrient loss intensified the remobilization of nutrients con-tained in older tree rings (close to the pith) towards newly formed rings (close to bark). In our study, in beech trees, K was found to be the most recycled major nutrient. These results demonstrate the potential of such analysis for providing valuable insight into the effect of RHRL in premature stands on the physiological adaptive strategies of trees and an indication of soil fertility status.

Automated summary

Increased exportation of forest harvest residues due to higher demand for woody biomass has led to soil mineral resource depletion and negative effects on tree nutrition and growth. Removing harvest residues and litter significantly reduces tree growth and wood density in young beech and oak forest stands.