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.

Does climate change alter the nutrient trends of Cedrela fissilis Vell.trees in the southern Brazilian Amazon?

Background The increase in the frequency and intensity of droughts is pointed out as one of the main factors altering biogeochemical cycles in the Amazon basin.An eco-nutritional approach using X-ray fluorescence micro-analysis(μXRF)is proposed to verify the long-and short-term effects of droughts on the growth and xylem nutrient concentrations of Cedrela fissilis Vell.Methods Fourteen radii were selected from a tree-ring width chronology and X-rayed by Itrax Multiscanner.Profiles of ring width,wood density,and concentrations of aluminum(Al),phosphorus(P),sulfur(S),calcium(Ca),potassium(K),manganese(Mn),iron(Fe)and strontium(Sr)together with Al/Ca,Ca/Mn,K/Ca,Sr/Ca and Mn/S ratios were constructed and correlated with precipitation,temperature,the difference between precipitation and potential evapotranspiration(P-PET)and standardized precipitation-evapotranspiration index(SPEI).Results During dry years,C.fissilis showed narrower,less dense rings,lower Al,P,S and Ca,and higher K and Fe concentrations(the opposite was found in wet years).Ring width decreased(together with Al,P,S,K,Ca,Mn,Fe,Sr,Al/Ca,K/Ca and Sr/Ca)and wood density increased(together with Ca/Mn and Mn/S),which was associated with an increase in evapotranspiration and temperature over time,mainly since 1990.Cedrela fissilis showed a tendency to increase its capacity for resistance,and a recovery and resilience in growth over time associated with responses in Al,Ca,P and S.However,it showed a risk in the capacity for recovery of the pre-drought density values,associated with unsatisfactory responses in Al,Ca,K,Fe and P.Conclusions This study is the first attempt to analyze tree-ring nutritional evidences of C.fissilis trees to climate sensitivity and resilience to drought,based on long-term data from seasonal moist tropical forests of the Amazon.Our data suggested that C.fissilis is undergoing alterations in the concentration,use and redistribution of nutrients associated with increasing wood density and decreasing growth over time,due to the increase of drought frequency in the southern Amazon.