基于BP神经网络模型的全球森林土壤异养硝化过程N2O排放通量估算

N₂O作为重要的温室气体之一，对地球和人类都有很大的影响。为了深入探究对有机氮异养硝化作用及其产生N₂O过程的影响机制，完善全球N₂O通量估算模型，本研究采用Pearson相关性分析与广义可加模型(GAM)对全球135个样点有机氮异养硝化速率及其产生N₂O速率的影响因子进行分析，然后将主要影响因子作为BP神经网络的输入层来模拟全球森林土壤有机氮异养硝化速率及其产生N₂O速率的空间分布。结果显示，土壤pH和土壤C/N是影响有机氮异养硝化速率的主要因素，土壤C/N、土壤孔隙含水量(WFPS)以及土壤温度是影响有机氮异养硝化产生N₂O速率的主要因素。全球森林土壤异养硝化速率平均为0.4241(0.0014～0.689)μg N·g^-1·d^-1,异养硝化产生N₂O速率平均为0.2936(0.21～1.103)μg N₂O·kg^-1·d^-1

Estimation of N2O emission flux from heterotrophic nitrification process in global forest soils based on BP neural network model

As one of the main greenhouse gases,N₂O has a significant impact on the Earth and human beings.To explore the influence mechanisms of heterotrophic nitrification of organic N and N₂O emission process and improve global N₂O flux estimation model,Pearson correlation analysis and generalized additive model(GAM)were used to analyze the influencing factors of heterotrophic nitrification rates of organic N and N₂O emission rates in 135 sam-pling sites worldwide.The major influencing factors were included into BP neural network model to estimate the spa-tial distribution of heterotrophic nitrification rates of organic N and N₂O emission rates in global forest soils.The results showed that soil pH and C/N were the main factors affecting heterotrophic nitrification rate of organic N.Soil C/N,water-filled pore space(WFPS),and temperature are the main factors affecting N₂O emission rate during heterotrophic nitrification process.The average heterotrophic nitrification rate was 0.4241(0.0014-0.689)μg N·g^-1·d^-1,and the average N₂O emission rate in the heterotrophic nitrification process was 0.2936(0.21-1.103)μg N₂O·kg^-1·d^-1 in global forest soils.The heterotrophic nitrification rate and N₂O emission rate in the hetero-trophic nitrification process were higher in forest soils around 50°N.In contrast,the two rates were lower in forest soils from 30°S to 30°N.Although heterotrophic nitrification rate was high,N₂O emission rate in the heterotrophic nitrification process was low in forest soils in Northeast Asia.N₂O emission flux from the heterotrophic nitrification of organic N was(1.4584±0.3791)Tg N·a^-1in global forest soils,accounting for 26.04%of N₂O emission from natural soils and 8.58%of global N₂O emission.