Developing allometric equations to estimate forest biomass for tree species categories based on phylogenetic relationships

The development of allometric biomass models is important process in biomass estimation because the reliability of forest biomass and carbon estimations largely depends on the accuracy and precision of such models.National Forest Inventories(NFI)are detailed assessments of forest resources at national and regional levels that provide valuable data for forest biomass estimation.However,the lack of biomass allometric equations for each tree species in the NFI currently hampers the estimation of national-scale forest biomass.The main objective of this study was to develop allometric biomass regression equations for each tree species in the NFI of China based on limited biomass observations.These equations optimally grouped NFI and biomass observation species according to their phylogenetic relationships.Significant phylogenetic signals demonstrated phylogenetic conservation of the crown-to-stem biomass ratio.Based on phylogenetic relationships,we grouped and matched NFI and biomass observation species into 22 categories.Allometric biomass regression models were developed for each of these 22 species categories,and the models performed successfully(R^(2)=0.97,root mean square error(RMSE)=12.9​t·ha^(–1),relative RMSE=11.5%).Furthermore,we found that phylogeny-based models performed more effectively than wood density-based models.The results suggest that grouping species based on their phylogenetic relationships is a reliable approach for the development and selection of accurate allometric equations.

Insights into the selective catalytic reduction of NO by NH_3 over Mn_3O_4(110):a DFT study coupled with microkinetic analysis

Nitric oxide(NO_x), as one of the main pollutants, can contribute to a series of environmental problems, and to date the selective catalytic reduction(SCR) of NO_x with NH_3 in the presence of excess of O_2 over the catalysts has served as one of the most effective methods, in which Mn-based catalysts have been widely studied owing to their excellent low-temperature activity toward NH3-SCR. However, the related structure-activity relation was not satisfactorily explored at the atomic level. By virtue of DFT+U calculations together with microkinetic analysis, we systemically investigate the selective catalytic reduction process of NO with NH_3 over Mn_3 O_4(110), and identify the crucial thermodynamic and kinetic factors that limit the catalytic activity and selectivity.It is found that NH3 prefers to adsorb on the Lewis acid site and then dehydrogenates into NH_2~* assisted by either the two-or three-fold lattice oxygen; NH_2~* would then react with the gaseous NO to form an important intermediate NH_2 NO that prefers to convert into N_2 O rather than N_2 after the sequential dehydrogenation, while the residual H atoms interact with O_2 and left the surface in the form of H_2 O. The rate-determining step is proposed to be the coupling reaction between NH_2~* and gaseous NO.Regarding the complex surface structure of Mn_3 O_4(110),the main active sites are quantitatively revealed to be O_(3 c) and Mn_(4 c).