全球变化中氮沉降日益严重,已对森林生态系统的各个过程产生了重要影响。因此,通过研究氮添加对森林生态系统土壤碳输出的影响,对分析全球变化背景下土壤碳吸存具有重要意义。对黑龙江省帽儿山实验林场白桦(Betula platyphylla)次生林,...全球变化中氮沉降日益严重,已对森林生态系统的各个过程产生了重要影响。因此,通过研究氮添加对森林生态系统土壤碳输出的影响,对分析全球变化背景下土壤碳吸存具有重要意义。对黑龙江省帽儿山实验林场白桦(Betula platyphylla)次生林,以及水曲柳(Fraxinus mandschurica)、红松(Pinus koraiensis)、长白落叶松(Larix olgensis)人工林通过2年氮添加(对照(0 kg N hm^-2 a^-1),低氮(50 kg N hm^-2 a^-1),中氮(100 kg N hm^-2 a^-1)和高氮(150 kg N hm^-2 a^-1))试验,测定根生物量密度、土壤微生物量碳浓度、土壤呼吸速率及温、湿度敏感性等指标,旨在探讨森林生态系统土壤呼吸对氮添加的短期响应。结果表明:(1)低氮处理对白桦和水曲柳林土壤呼吸速率影响不显著,但显著提高了红松和长白落叶松林土壤呼吸速率;水曲柳林分中高氮处理土壤呼吸速率显著降低于低氮和中氮处理,而其他林分高氮处理土壤呼吸速率仅显著低于低氮处理。(2)氮添加处理下,4种林分中林分土壤呼吸速率与根生物量密度呈极显著正相关,Pearson相关系数为0.81。(3)低氮处理下5 cm和10 cm处土壤呼吸温度敏感性系数Q10值较CK处理分别提高了2.65%和3.12%,高氮处理较CK处理分别降低了6.29%和5.46%。但氮添加处理对土壤呼吸和土壤湿度间的相关性无影响。综上所述,阔叶林与针叶林土壤呼吸速率对氮添加的响应存在差异。根生物量密度是影响不同林分土壤呼吸对短期氮添加响应的主要因素,同时氮添加处理显著改变了土壤温度敏感性系数。展开更多
This paper revealed the climatic change characteristics of fog and haze of different levels over North China and Huang-Huai area(NCHH).It was found that the haze-prone period has changed from winter into a whole year,...This paper revealed the climatic change characteristics of fog and haze of different levels over North China and Huang-Huai area(NCHH).It was found that the haze-prone period has changed from winter into a whole year,and the haze days(HD)in winter have increased significantly.The foggy days(FD)are half of HD.There are little difference on the number of days and trends of fog at various levels.The HD and FD show no obvious positive correlation until the 1980s.Fog has larger spatial scale,showing more in the south than in the north.Haze occurs mainly around large cities with a discrete distribution.In the background of weakened East Asian Winter Monsoon(EAWM)and sufficient particulate matter,the negative correlation between haze and wind speed is weakened,but the positive correlation between haze and moisture conditions(precipitation and humidity)is significantly strengthened.In recent years,small wind and variability appear frequently.Meanwhile,as the stable source and strong moisture absorption of the aerosol particles,the moisture condition becomes one key control factor in the haze,especially wet haze with less visibility.In contrast,the FD presents a stable positive correlation with precipitation and relative humidity,but has no obvious negative correlation with wind speed.展开更多
Organic thin film transistors(OTFTs)are normally sensitive to ambient conditions and show performance degradation in air.On the contrary,the performance of flexible 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene(C8...Organic thin film transistors(OTFTs)are normally sensitive to ambient conditions and show performance degradation in air.On the contrary,the performance of flexible 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene(C8-BTBT)OTFTs using cross-linked polymer layer,poly(4-vinyl-phenol)-4,4’-(hexafluoroisopropylidene)diphthalic anhydride(PVP-HDA),as the dielectric layer can be improved in air conditions with 40%relative humidity.Under soaking in air with 40%relative humidity,the electrical behavior,surface morphology,and contact angle of the flexible C8-BTBT OTFTs using PVP-HAD as dielectric layer with three different thicknesses were investigated.It is found that,when the devices with 375 nm-thick PVP-HDA films are placed in 40%relative humidity air conditions for 6 h,the corrected average mobility(μ)can increase from 3.2 to 5.1 cm^2 V^-1 s^-1.Furthermore,the average threshold voltage(Vth)changes from-12.4 to-9.3 V while keeping a constant ratio of I on/Ioff=10^4.These results indicate that the flexible C8-BTBT OTFTs with PVP-HDA dielectric layer exhibit interesting application prospects.展开更多
文摘全球变化中氮沉降日益严重,已对森林生态系统的各个过程产生了重要影响。因此,通过研究氮添加对森林生态系统土壤碳输出的影响,对分析全球变化背景下土壤碳吸存具有重要意义。对黑龙江省帽儿山实验林场白桦(Betula platyphylla)次生林,以及水曲柳(Fraxinus mandschurica)、红松(Pinus koraiensis)、长白落叶松(Larix olgensis)人工林通过2年氮添加(对照(0 kg N hm^-2 a^-1),低氮(50 kg N hm^-2 a^-1),中氮(100 kg N hm^-2 a^-1)和高氮(150 kg N hm^-2 a^-1))试验,测定根生物量密度、土壤微生物量碳浓度、土壤呼吸速率及温、湿度敏感性等指标,旨在探讨森林生态系统土壤呼吸对氮添加的短期响应。结果表明:(1)低氮处理对白桦和水曲柳林土壤呼吸速率影响不显著,但显著提高了红松和长白落叶松林土壤呼吸速率;水曲柳林分中高氮处理土壤呼吸速率显著降低于低氮和中氮处理,而其他林分高氮处理土壤呼吸速率仅显著低于低氮处理。(2)氮添加处理下,4种林分中林分土壤呼吸速率与根生物量密度呈极显著正相关,Pearson相关系数为0.81。(3)低氮处理下5 cm和10 cm处土壤呼吸温度敏感性系数Q10值较CK处理分别提高了2.65%和3.12%,高氮处理较CK处理分别降低了6.29%和5.46%。但氮添加处理对土壤呼吸和土壤湿度间的相关性无影响。综上所述,阔叶林与针叶林土壤呼吸速率对氮添加的响应存在差异。根生物量密度是影响不同林分土壤呼吸对短期氮添加响应的主要因素,同时氮添加处理显著改变了土壤温度敏感性系数。
基金supported by the National Natural Science Foundation of China (Grant Nos. 41130103, 41210007)
文摘This paper revealed the climatic change characteristics of fog and haze of different levels over North China and Huang-Huai area(NCHH).It was found that the haze-prone period has changed from winter into a whole year,and the haze days(HD)in winter have increased significantly.The foggy days(FD)are half of HD.There are little difference on the number of days and trends of fog at various levels.The HD and FD show no obvious positive correlation until the 1980s.Fog has larger spatial scale,showing more in the south than in the north.Haze occurs mainly around large cities with a discrete distribution.In the background of weakened East Asian Winter Monsoon(EAWM)and sufficient particulate matter,the negative correlation between haze and wind speed is weakened,but the positive correlation between haze and moisture conditions(precipitation and humidity)is significantly strengthened.In recent years,small wind and variability appear frequently.Meanwhile,as the stable source and strong moisture absorption of the aerosol particles,the moisture condition becomes one key control factor in the haze,especially wet haze with less visibility.In contrast,the FD presents a stable positive correlation with precipitation and relative humidity,but has no obvious negative correlation with wind speed.
基金supported by the National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China(51673214)。
文摘Organic thin film transistors(OTFTs)are normally sensitive to ambient conditions and show performance degradation in air.On the contrary,the performance of flexible 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene(C8-BTBT)OTFTs using cross-linked polymer layer,poly(4-vinyl-phenol)-4,4’-(hexafluoroisopropylidene)diphthalic anhydride(PVP-HDA),as the dielectric layer can be improved in air conditions with 40%relative humidity.Under soaking in air with 40%relative humidity,the electrical behavior,surface morphology,and contact angle of the flexible C8-BTBT OTFTs using PVP-HAD as dielectric layer with three different thicknesses were investigated.It is found that,when the devices with 375 nm-thick PVP-HDA films are placed in 40%relative humidity air conditions for 6 h,the corrected average mobility(μ)can increase from 3.2 to 5.1 cm^2 V^-1 s^-1.Furthermore,the average threshold voltage(Vth)changes from-12.4 to-9.3 V while keeping a constant ratio of I on/Ioff=10^4.These results indicate that the flexible C8-BTBT OTFTs with PVP-HDA dielectric layer exhibit interesting application prospects.
