Background:Solar radiation(SR)plays critical roles in plant physiological processes and ecosystems functions.However,the exploration of SR influences on the biogeochemical cycles of forest ecosystems is still in a slo...Background:Solar radiation(SR)plays critical roles in plant physiological processes and ecosystems functions.However,the exploration of SR influences on the biogeochemical cycles of forest ecosystems is still in a slow progress,and has important implications for the understanding of plant adaption strategy under future environmental changes.Herein,this research was aimed to explore the influences of SR on plant nutrient characteristics,and provided theoretical basis for introducing SR into the establishment of biochemical models of forest ecosystems in the future researches.Methods:We measured leaf nitrogen(N)and phosphorus(P)stoichiometry in 19 Chinese fir plantations across subtropical China by a field investigation.The direct and indirect effects of SR,including global radiation(Global R),direct radiation(Direct R)and diffuse radiation(Diffuse R)on the leaf N and P stoichiometry were investigated.Results:The linear regression analysis showed that leaf N concentration had no association with SR,while leaf P concentration and N:P ratio were negatively and positively related to SR,respectively.Partial least squares path model(PLS-PM)demonstrated that SR(e.g.Direct R and Diffuse R),as a latent variable,exhibited direct correlations with leaf N and P stoichiometry as well as the indirect correlation mediated by soil P content.The direct associations(path coefficient=−0.518)were markedly greater than indirect associations(path coefficient=−0.087).The covariance-based structural equation modeling(CB-SEM)indicated that SR had direct effects on leaf P concentration(path coefficient=−0.481),and weak effects on leaf N concentration.The high SR level elevated two temperature indexes(mean annual temperature,MAT;≥10°C annual accumulated temperature,≥10℃ AAT)and one hydrological index(mean annual evapotranspiration,MAE),but lowered the soil P content.MAT,MAE and soil P content could affect the leaf P concentration,which cause the indirect effect of SR on leaf P concentration(path coefficient=0.004).Soil N content had positive effect on the leaf N concentration,which was positively and negatively regulated by MAP and≥10℃ AAT,respectively.Conclusions:These results confirmed that SR had negatively direct and indirect impacts on plant nutrient status of Chinese fir based on a regional investigation,and the direct associations were greater than the indirect associations.Such findings shed light on the guideline of taking SR into account for the establishment of global biogeochemical models of forest ecosystems in the future studies.展开更多
在气候变化背景下,干旱频率和强度的增加将对森林生态系统的碳循环过程产生重要影响,掌握土壤呼吸及其敏感性对干旱的响应规律有助于评价土壤在碳收支过程中的源汇角色.本研究用顶棚法野外模拟毛竹林干旱下凋落物不变(LU)、添加(LA)、移...在气候变化背景下,干旱频率和强度的增加将对森林生态系统的碳循环过程产生重要影响,掌握土壤呼吸及其敏感性对干旱的响应规律有助于评价土壤在碳收支过程中的源汇角色.本研究用顶棚法野外模拟毛竹林干旱下凋落物不变(LU)、添加(LA)、移除(LR)处理对土壤呼吸动态及其温度敏感性的影响和滞留效应.结果表明:对照(自然降雨)和干旱条件下凋落物不变处理年均土壤呼吸速率分别为3.15和2.34μmol·m^(-2)·s^(-1).凋落物移除处理较凋落物添加处理对土壤呼吸的影响大,对照和干旱条件下凋落物移除处理较不变处理分别下降21.0%和20.9%,仅干旱条件下凋落物添加处理较不变处理增加5.3%;说明干旱条件下凋落物添加和移除处理对土壤呼吸的影响均较不变处理明显.干旱条件下土壤呼吸的温度敏感性较对照降低8.4%,凋落物添加处理和凋落物移除处理温度敏感性分别下降15.4%和7.6%.对照和干旱条件下18个月土壤碳累积排放量分别为7.35和5.40 kg CO_2·m^(-2),对照和干旱条件下凋落物添加处理较不变处理分别增加1.8%和10.7%,凋落物移除处理分别下降19.9%和18.0%.凋落物添加处理或移除处理对毛竹林土壤呼吸速率的影响呈非线性,因土壤水分的减少直接影响根系生长和微生物活性致使滞留效应明显,干旱条件下凋落物量对土壤碳排放的影响更明显,凋落物量的变化是气候变化背景下土壤碳排放不可忽视的影响因素.展开更多
基金funded by the National Key Research and Development Program of China(No.2016YFD0600202-4)the Fundamental Research Funds for the Central Non-profit Research Institution of Chinese fir Academy of Forestry(Nos.CAFYBB2017ZX002-2 and CAFYBB2020ZE001).
文摘Background:Solar radiation(SR)plays critical roles in plant physiological processes and ecosystems functions.However,the exploration of SR influences on the biogeochemical cycles of forest ecosystems is still in a slow progress,and has important implications for the understanding of plant adaption strategy under future environmental changes.Herein,this research was aimed to explore the influences of SR on plant nutrient characteristics,and provided theoretical basis for introducing SR into the establishment of biochemical models of forest ecosystems in the future researches.Methods:We measured leaf nitrogen(N)and phosphorus(P)stoichiometry in 19 Chinese fir plantations across subtropical China by a field investigation.The direct and indirect effects of SR,including global radiation(Global R),direct radiation(Direct R)and diffuse radiation(Diffuse R)on the leaf N and P stoichiometry were investigated.Results:The linear regression analysis showed that leaf N concentration had no association with SR,while leaf P concentration and N:P ratio were negatively and positively related to SR,respectively.Partial least squares path model(PLS-PM)demonstrated that SR(e.g.Direct R and Diffuse R),as a latent variable,exhibited direct correlations with leaf N and P stoichiometry as well as the indirect correlation mediated by soil P content.The direct associations(path coefficient=−0.518)were markedly greater than indirect associations(path coefficient=−0.087).The covariance-based structural equation modeling(CB-SEM)indicated that SR had direct effects on leaf P concentration(path coefficient=−0.481),and weak effects on leaf N concentration.The high SR level elevated two temperature indexes(mean annual temperature,MAT;≥10°C annual accumulated temperature,≥10℃ AAT)and one hydrological index(mean annual evapotranspiration,MAE),but lowered the soil P content.MAT,MAE and soil P content could affect the leaf P concentration,which cause the indirect effect of SR on leaf P concentration(path coefficient=0.004).Soil N content had positive effect on the leaf N concentration,which was positively and negatively regulated by MAP and≥10℃ AAT,respectively.Conclusions:These results confirmed that SR had negatively direct and indirect impacts on plant nutrient status of Chinese fir based on a regional investigation,and the direct associations were greater than the indirect associations.Such findings shed light on the guideline of taking SR into account for the establishment of global biogeochemical models of forest ecosystems in the future studies.
文摘在气候变化背景下,干旱频率和强度的增加将对森林生态系统的碳循环过程产生重要影响,掌握土壤呼吸及其敏感性对干旱的响应规律有助于评价土壤在碳收支过程中的源汇角色.本研究用顶棚法野外模拟毛竹林干旱下凋落物不变(LU)、添加(LA)、移除(LR)处理对土壤呼吸动态及其温度敏感性的影响和滞留效应.结果表明:对照(自然降雨)和干旱条件下凋落物不变处理年均土壤呼吸速率分别为3.15和2.34μmol·m^(-2)·s^(-1).凋落物移除处理较凋落物添加处理对土壤呼吸的影响大,对照和干旱条件下凋落物移除处理较不变处理分别下降21.0%和20.9%,仅干旱条件下凋落物添加处理较不变处理增加5.3%;说明干旱条件下凋落物添加和移除处理对土壤呼吸的影响均较不变处理明显.干旱条件下土壤呼吸的温度敏感性较对照降低8.4%,凋落物添加处理和凋落物移除处理温度敏感性分别下降15.4%和7.6%.对照和干旱条件下18个月土壤碳累积排放量分别为7.35和5.40 kg CO_2·m^(-2),对照和干旱条件下凋落物添加处理较不变处理分别增加1.8%和10.7%,凋落物移除处理分别下降19.9%和18.0%.凋落物添加处理或移除处理对毛竹林土壤呼吸速率的影响呈非线性,因土壤水分的减少直接影响根系生长和微生物活性致使滞留效应明显,干旱条件下凋落物量对土壤碳排放的影响更明显,凋落物量的变化是气候变化背景下土壤碳排放不可忽视的影响因素.
