[Objective] The study aimed to identify Alternaria Nees from some areas of China at molecular level by analyzing the rDNA ITS sequence. [ Method ] The DNA sequences coding for the 5.8S rDNA and the flanking internal t...[Objective] The study aimed to identify Alternaria Nees from some areas of China at molecular level by analyzing the rDNA ITS sequence. [ Method ] The DNA sequences coding for the 5.8S rDNA and the flanking internal transcribed spacers （ ITS1 and ITS2） were amplified by PCR with universal primers ITS4 and ITS5 and subsequently sequenced for 34 Alternaria isolates from different areas of China. [Result] Sequences analysis showed that 5.8S rDNA was 159 bp and no variation in tested 34 isolates. There had variables sites in ITS. The isolates that had same sequences as A. tenuissima or A. alternata all put up eurytopicity to area and host. The variables sites of the isolates showed the diver- sity of Alternaria in the hosts of Oleaceae, Rosaceae and Solanaceae. At the same time that ITS could not clearly separated the isolates was indicated. The results indicated that the phylogenetic relationship were not closely related to the geographical origin and hosts of these isolates. [ Conclusion] The sequence analysis of ITS region could provide theory basis for the identification of Alternaria Nees..展开更多
[Objective] This study aimed to compare the microstructure between I. in- digotica Fort. and B. cusia （Nees） Bremek. [Method] Microstructure of I. indigotica Fort. and B. cusia （Nees） Bremek. with different source...[Objective] This study aimed to compare the microstructure between I. in- digotica Fort. and B. cusia （Nees） Bremek. [Method] Microstructure of I. indigotica Fort. and B. cusia （Nees） Bremek. with different sources were compared and analyzed by using digital microscopy. [Result] Comparison result of the microstructure shows that reticulate vessels, single starch granules, multiple starch granules and stone cells are mostly observed in I. indigotica Fort.; pitted vessels, parenchyma cells with small pits, single starch granules and cystolith are mostly observed in B. cusia （Nees） Bremek., which indicated that microstructure of L indigotica Fort. and B. cusia （Nees） Bremek. are significantly different. [Conclusion] Microstructure char- acteristics of I. indigotica Fort. and B. cusia （Nees） Bremek. established in this study can be used to evaluate the quality of these two kinds of Chinese herbal medicines, which also provide scientific basis and methods for comprehensively studying the quality standard of /. indigotica Fort. and B. cusia （Nees） Bremek. Key words Isatis indigotica Fort.; Baphicacanthus cusia （Nees） Bremek.; Microstruc- ture; Quality展开更多
A new isocoumarin,tenuissimasatin（1）,was isolated from metabolites of the endophytic fungus Alternaria tenuissima（Nees ＆ T.Nees：Fr.） Wiltshire,which was isolated from the bark of Erythrophleum fordii Oliver,toge...A new isocoumarin,tenuissimasatin（1）,was isolated from metabolites of the endophytic fungus Alternaria tenuissima（Nees ＆ T.Nees：Fr.） Wiltshire,which was isolated from the bark of Erythrophleum fordii Oliver,together with 11 known compounds（2- 12）.The structure and absolute configuration of 1 was determined by means of NMR and CD analysis.Compound 3 shows selective cytotoxic activity on human colon cancer cell HCT-8（IC_（50） = 1.78μmol/L） by MTT test in vitro.Other compounds show no such activities（IC_（50）〉10μmol/L）.展开更多
Protein extraction is a critical step for two-dimensional electrophoresis （2-DE）. Different plant samples require different and adaptive protein extraction protocols. The leaves of medicinal plant, Baphicacanthus cu...Protein extraction is a critical step for two-dimensional electrophoresis （2-DE）. Different plant samples require different and adaptive protein extraction protocols. The leaves of medicinal plant, Baphicacanthus cusia （Nees） Bremek are notoriously recalcitrant to common protein extraction methods due to high levels of interfering compounds （especially the secondary metabolites and pigments）. This study was aimed to establish a routine procedure for the proteomic analysis ofB. cusia leaves, and a new protocol for the protein extraction was developed by optimizing trichloroacetic acid （TCA）/ acetone extraction method. The efficiency of this protocol was demonstrated by comparison with 3 published protein extraction methods （chloroform/acetone, Mg/NP-40, Tris-base/acetone）. The results showed that the optimized TCA/ acetone precipitation extraction method gave a relatively high protein yield （9.263 mg g^-1 fresh weight）, high-resolution separation, clear protein profiles, the highest proteins spots （1 31 t protein spots）, and displayed less contamination in 2- DE gels. Therefore, the results suggested that the optimized TCA/acetone method was the most effective among the 4 methods for B. cusia leaves.展开更多
The aim of this experiment is to study the mechanism of APN in alleviating the Ca2+-overloading in dog model during the process of ischemic reperfusion. In comparison with the sustained ischemic group, the parameters ...The aim of this experiment is to study the mechanism of APN in alleviating the Ca2+-overloading in dog model during the process of ischemic reperfusion. In comparison with the sustained ischemic group, the parameters in the ischemic reperfusion group demonstrated: Ca2+ of ischemic region of myocardial cell increased (P<0.05) , Na+ increased remarkably(P<0. 01), the activity of Ca2+-ATPase dropped remarkably(P<0. 01),and MDA increased significantly(P<0. 01). Whereas in the group pretreated with APN, the Ca2+ in the relevant area reduced (P<0.05), Na+ decreased significantly(P<0. 01), the activity of Ca2+-ATPase and Na+-K+ ATPase increased remarkably(P<0.01) ,and MDA decreased significantly (P<0. 01). These findings indicate that APN may improve the activity of sarcolemma ATPase in alleviating the Ca2+ and Na+-overloading by decreasing the harmful effect of oxygen free radicals.展开更多
Machilus spp.are mostly valuable timber and economic tree species,widely used in many fields such as artificial afforestation,landscaping,furniture and building materials,chemicals and medicine.In this article,the dis...Machilus spp.are mostly valuable timber and economic tree species,widely used in many fields such as artificial afforestation,landscaping,furniture and building materials,chemicals and medicine.In this article,the distribution,uses and domestic resources of Machilus Nees are summarized.Focus is placed on the analysis of propagation methods,including seed propagation,cutting propagation and tissue culture propagation.The research status and existing problems are summarized,and the future research focus on the propagation technology of Machilus Nees is prospected,with a view to provide theoretical references for the efficient breeding of high-quality seedlings and comprehensive promotion and application of Machilus spp.and contribute to the conservation and sustainable use of wild resources.展开更多
[Objectives]To observe the effects of polysaccharides from Dicliptera chinensis(L.)Nees.on the expression of TLR/NF-κB pathway related proteins in HepG2 cells induced by oleic acid,and to explore the possible mechani...[Objectives]To observe the effects of polysaccharides from Dicliptera chinensis(L.)Nees.on the expression of TLR/NF-κB pathway related proteins in HepG2 cells induced by oleic acid,and to explore the possible mechanism of polysaccharides from D.chinensis(L.)Nees.in the treatment of non-alcoholic fatty liver disease(NAFLD).[Methods]HepG2 cells were induced with oleic acid to establish a non-alcoholic fatty liver cell model.After intervention with 0.25 and 0.5 mg/mL of D.chinensis(L.)Nees.polysaccharides,the ALT and AST activity and TG and TC contents were detected with kits,and the changes in the expression of CDK5,TLR4,p-NF-κB and NF-κB were analyzed using Western-blotting.[Results]In the HepG2 cells induced with oleic acid,the ALT and AST activity increased significantly,the TG and TC contents increased significantly,and the expression levels of CDK5,TLR4 and p-NF-κB proteins up-regulated significantly.In the HepG2 cells intervened with D.chinensis(L.)Nees.polysaccharides,the activity of ALT and AST,the contents of TG and TC,and the expression levels of CDK5,TLR4 and p-NF-κB proteins all reduced significantly.[Conclusions]Polysaccharides from D.chinensis(L.)Nees.may interfere with NAFLD by inhibiting the TLR4/NF-κB pathway.展开更多
In experimental dogs,the effect of APN in alleviating the ischemiareperfusion injury was prominent.Compared with the sustained isthmian group,superoxide dismutast(SOD)in the ischemic region of myocardial tissue in the...In experimental dogs,the effect of APN in alleviating the ischemiareperfusion injury was prominent.Compared with the sustained isthmian group,superoxide dismutast(SOD)in the ischemic region of myocardial tissue in the ischemiareperfusion group was significantly decreased and malondialdehyde(MDA)marktdly increased Ca2+in myocardial cells was increased. and ultrastructural changes of myocardial tisstes were severe in the APN-pretreated ischemia-reperfusion group ,on the contrary,all the above parameters showed reversely,i,e.,SOD increased ,MDA and intracellular Ca2+ decreased.the ultrastructure changes were less distorted.展开更多
The aim of this project is to explore the mechanism of the treatment of alcoholic liver by means of network pharmacology and molecular docking.In this study,the chemical components of the extract of Callistephus chine...The aim of this project is to explore the mechanism of the treatment of alcoholic liver by means of network pharmacology and molecular docking.In this study,the chemical components of the extract of Callistephus chinensis(L.)Nees.were characterized by LC-MS/MS,identifying 6 compounds by positive and negative total ion flow maps.The target of chrysanthemum was derived from SwissTargetPrediction database,and the target related to alcoholic liver was derived from GeneCards and OMIM database.Add the target to the String database to build the protein interaction platform Microbiology software was used for GO bioprocess enrichment analysis and KEGG pathway enrichment analysis,and the target pathway network was constructed.In Discovery Studio 2016 Client software verified molecular docking,China aster flavonoids compounds and the adhesion strength of the key targets.Five potential active components were screened from the flavonoid monomer compounds of the chrysanthemum Cupressus.546 Bioprocess(BP),75 cell composition(CC)and 185·molecular function(MF)were obtained by GO enrichment analysis.KEGG enrichment analysis for each cross target involved a pathway.Network analysis showed that it was the main active component of flavonoids in the treatment of alcoholic liver,and other related signals were related to the treatment of alcoholic liver.This study showed that the flavonoids of Callistephus chinensis(L.)Nees were involved in the treatment of alcoholic liver by regulating multi-target and multi-pathway.展开更多
机器学习已经广泛用于生态系统研究。基于2014年1月1日至2018年12月31日兴安落叶松生态系统碳通量(NEE)观测数据,分析了其动态变化特征,并采用多种机器学习方法进行模拟。结果表明:(1)生长季兴安落叶松生态系统NEE日动态呈“U”变化,整...机器学习已经广泛用于生态系统研究。基于2014年1月1日至2018年12月31日兴安落叶松生态系统碳通量(NEE)观测数据,分析了其动态变化特征,并采用多种机器学习方法进行模拟。结果表明:(1)生长季兴安落叶松生态系统NEE日动态呈“U”变化,整体表现为碳汇,7月份碳汇能力最强,达67.57 g C m^(-2)月^(-1),9月至次年5月表现为碳源。(2)结构方程模型分析表明,兴安落叶松生态系统NEE的主要影响因子为潜热通量(LE)、净辐射(Rn)、叶面积指数(LAI)、空气温度(Ta)、相对湿度(RH)、饱和水汽压差(VPD)和土壤含水量(SWC),其中潜热通量和净辐射是影响NEE变化的最主导因素。(3)四种机器学习方法(RF、XGBoost、SVM、ANN)均能较准确地模拟兴安落叶松生态系统NEE,其中XGBoost和RF的模拟结果最为相近,但XGBoost在模拟精度和计算效率方面优于RF。研究结果为应用机器学习方法估算生态系统碳通量提供了依据。展开更多
弄清碳收支变化是促进区域可持续发展的重要方面。研究结合光合能力模型(Photosynthetic Capacity Model,PCM)和呼吸遥感模型(Remote Sensing Model for Ecosystem respiration,Re-RSM)提出了一个完全基于遥感数据的陆地碳收支动态评估...弄清碳收支变化是促进区域可持续发展的重要方面。研究结合光合能力模型(Photosynthetic Capacity Model,PCM)和呼吸遥感模型(Remote Sensing Model for Ecosystem respiration,Re-RSM)提出了一个完全基于遥感数据的陆地碳收支动态评估模型(Remote Sensing Land Carbon Budget Dynamic Assessment Model,RS-CBM),引入中国三北地区(东北、华北和西北地区)7种植被类型(玉米农田、针阔混交林、落叶针叶林、高寒草地、灌丛草甸、荒漠草原和芦苇湿地)的多年碳通量观测数据对RS-CBM模型进行参数化和验证,并应用此模型定量评估了2001—2020年三北地区植被NEE的时空特征与规律。结果表明,RS-CBM模型的模型精度高达0.75,均方根误差为0.07 mol·m^(-2)·d^(-1),RS-CBM模型的NEE模拟值与通量观测值具有较好的一致性,在不同植被类型的生长季旺盛期均出现较明显的碳吸收峰值,但存在不同程度的峰值低估现象。2001—2020年三北地区的NEE变化呈波动上升趋势,年平均值为82.01 g·m^(-2)·a^(-1),年平均增长量为5.843 g·m^(-2)·a^(-1),总体表现为碳汇。三北地区NEE在空间上呈现南高北低,东高西低的空间分异性。综上,RS-CBM模型能较好地模拟出三北地区碳收支变化和空间分布,具有在区域尺度模拟NEE时空变化的潜力。展开更多
针对不同陆地生态系统中净生态系统CO_(2)交换量(Net ecosystem exchange,NEE)数据的长期连续测量中存在的数据差异问题,以中国气象局青海高寒生态气象野外科学试验基地野牛沟试验站为研究对象,利用涡动协方差技术获取高寒湿地生态系统...针对不同陆地生态系统中净生态系统CO_(2)交换量(Net ecosystem exchange,NEE)数据的长期连续测量中存在的数据差异问题,以中国气象局青海高寒生态气象野外科学试验基地野牛沟试验站为研究对象,利用涡动协方差技术获取高寒湿地生态系统水平上的NEE数据。通过对比机器学习算法和通量数据后处理算法(Reddyproc)两种数据填充方法,提出了一种结合机器学习与时序异常检测(Time series anomaly detection,TAD)的新框架,用于NEE数据的空白填补。研究结果表明:1)Reddyproc算法在剔除异常值后,NEE插补决定系数(R^(2))达到0.67,数据离散度显著降低,数据质量提升;2)八种机器学习模型中,随机森林(Random Forest,RF)模型表现最优,其决定系数(Coefficient of determination,R^(2))为0.63,均方根误差(Root mean square error,RMSE)为2.17μmol s^(-1)m^(-2),且经过时序异常检测后,估算精度提升了17%;3)Reddyproc和RF估算的CO_(2)通量存在季节性差异,冷季(1—3月和10—12月)Reddyproc估算值低于RF,而暖季(4—9月)则高于RF,表明冬季Reddyproc低估了CO_(2)释放,夏季则低估了CO_(2)吸收。该新框架有效解决了数据采集不确定性和缺失导致的二氧化碳通量计算准确率问题,为研究高寒湿地生态系统的碳固持能力、对气候变化的响应以及极端事件的影响提供了关键数据支持。未来研究应进一步探索新方法的适用性、改进和优化方向,以实现更准确、可靠且适用于不同生态系统的填补模型,为生态系统建模和预测提供强大工具。展开更多
基金Supported by National Natural Science Foundation of China(3046003)~~
文摘[Objective] The study aimed to identify Alternaria Nees from some areas of China at molecular level by analyzing the rDNA ITS sequence. [ Method ] The DNA sequences coding for the 5.8S rDNA and the flanking internal transcribed spacers （ ITS1 and ITS2） were amplified by PCR with universal primers ITS4 and ITS5 and subsequently sequenced for 34 Alternaria isolates from different areas of China. [Result] Sequences analysis showed that 5.8S rDNA was 159 bp and no variation in tested 34 isolates. There had variables sites in ITS. The isolates that had same sequences as A. tenuissima or A. alternata all put up eurytopicity to area and host. The variables sites of the isolates showed the diver- sity of Alternaria in the hosts of Oleaceae, Rosaceae and Solanaceae. At the same time that ITS could not clearly separated the isolates was indicated. The results indicated that the phylogenetic relationship were not closely related to the geographical origin and hosts of these isolates. [ Conclusion] The sequence analysis of ITS region could provide theory basis for the identification of Alternaria Nees..
文摘[Objective] This study aimed to compare the microstructure between I. in- digotica Fort. and B. cusia （Nees） Bremek. [Method] Microstructure of I. indigotica Fort. and B. cusia （Nees） Bremek. with different sources were compared and analyzed by using digital microscopy. [Result] Comparison result of the microstructure shows that reticulate vessels, single starch granules, multiple starch granules and stone cells are mostly observed in I. indigotica Fort.; pitted vessels, parenchyma cells with small pits, single starch granules and cystolith are mostly observed in B. cusia （Nees） Bremek., which indicated that microstructure of L indigotica Fort. and B. cusia （Nees） Bremek. are significantly different. [Conclusion] Microstructure char- acteristics of I. indigotica Fort. and B. cusia （Nees） Bremek. established in this study can be used to evaluate the quality of these two kinds of Chinese herbal medicines, which also provide scientific basis and methods for comprehensively studying the quality standard of /. indigotica Fort. and B. cusia （Nees） Bremek. Key words Isatis indigotica Fort.; Baphicacanthus cusia （Nees） Bremek.; Microstruc- ture; Quality
基金Financial support from the National Science and Technology Project of China(No2009ZX09311-004)the Natural Science Foundation of China(No201072234)
文摘A new isocoumarin,tenuissimasatin（1）,was isolated from metabolites of the endophytic fungus Alternaria tenuissima（Nees ＆ T.Nees：Fr.） Wiltshire,which was isolated from the bark of Erythrophleum fordii Oliver,together with 11 known compounds（2- 12）.The structure and absolute configuration of 1 was determined by means of NMR and CD analysis.Compound 3 shows selective cytotoxic activity on human colon cancer cell HCT-8（IC_（50） = 1.78μmol/L） by MTT test in vitro.Other compounds show no such activities（IC_（50）〉10μmol/L）.
基金supported by the Department of Edu-cation(JA05238)the Key Project on Ecology of Fujian Province,China(0608537)
文摘Protein extraction is a critical step for two-dimensional electrophoresis （2-DE）. Different plant samples require different and adaptive protein extraction protocols. The leaves of medicinal plant, Baphicacanthus cusia （Nees） Bremek are notoriously recalcitrant to common protein extraction methods due to high levels of interfering compounds （especially the secondary metabolites and pigments）. This study was aimed to establish a routine procedure for the proteomic analysis ofB. cusia leaves, and a new protocol for the protein extraction was developed by optimizing trichloroacetic acid （TCA）/ acetone extraction method. The efficiency of this protocol was demonstrated by comparison with 3 published protein extraction methods （chloroform/acetone, Mg/NP-40, Tris-base/acetone）. The results showed that the optimized TCA/ acetone precipitation extraction method gave a relatively high protein yield （9.263 mg g^-1 fresh weight）, high-resolution separation, clear protein profiles, the highest proteins spots （1 31 t protein spots）, and displayed less contamination in 2- DE gels. Therefore, the results suggested that the optimized TCA/acetone method was the most effective among the 4 methods for B. cusia leaves.
文摘The aim of this experiment is to study the mechanism of APN in alleviating the Ca2+-overloading in dog model during the process of ischemic reperfusion. In comparison with the sustained ischemic group, the parameters in the ischemic reperfusion group demonstrated: Ca2+ of ischemic region of myocardial cell increased (P<0.05) , Na+ increased remarkably(P<0. 01), the activity of Ca2+-ATPase dropped remarkably(P<0. 01),and MDA increased significantly(P<0. 01). Whereas in the group pretreated with APN, the Ca2+ in the relevant area reduced (P<0.05), Na+ decreased significantly(P<0. 01), the activity of Ca2+-ATPase and Na+-K+ ATPase increased remarkably(P<0.01) ,and MDA decreased significantly (P<0. 01). These findings indicate that APN may improve the activity of sarcolemma ATPase in alleviating the Ca2+ and Na+-overloading by decreasing the harmful effect of oxygen free radicals.
基金Forestry Science and Technology Innovation Project of Guangdong Province(14KJCX005-02).
文摘Machilus spp.are mostly valuable timber and economic tree species,widely used in many fields such as artificial afforestation,landscaping,furniture and building materials,chemicals and medicine.In this article,the distribution,uses and domestic resources of Machilus Nees are summarized.Focus is placed on the analysis of propagation methods,including seed propagation,cutting propagation and tissue culture propagation.The research status and existing problems are summarized,and the future research focus on the propagation technology of Machilus Nees is prospected,with a view to provide theoretical references for the efficient breeding of high-quality seedlings and comprehensive promotion and application of Machilus spp.and contribute to the conservation and sustainable use of wild resources.
基金National Natural Science Foundation of China(81960779,81760114,81660104,81860673)Natural Science Foundation of Guangxi Zhuang Autonomous Region(2017GXNSFAA198218,2017GXNSFAA198326,2018GXNSFAA281040)。
文摘[Objectives]To observe the effects of polysaccharides from Dicliptera chinensis(L.)Nees.on the expression of TLR/NF-κB pathway related proteins in HepG2 cells induced by oleic acid,and to explore the possible mechanism of polysaccharides from D.chinensis(L.)Nees.in the treatment of non-alcoholic fatty liver disease(NAFLD).[Methods]HepG2 cells were induced with oleic acid to establish a non-alcoholic fatty liver cell model.After intervention with 0.25 and 0.5 mg/mL of D.chinensis(L.)Nees.polysaccharides,the ALT and AST activity and TG and TC contents were detected with kits,and the changes in the expression of CDK5,TLR4,p-NF-κB and NF-κB were analyzed using Western-blotting.[Results]In the HepG2 cells induced with oleic acid,the ALT and AST activity increased significantly,the TG and TC contents increased significantly,and the expression levels of CDK5,TLR4 and p-NF-κB proteins up-regulated significantly.In the HepG2 cells intervened with D.chinensis(L.)Nees.polysaccharides,the activity of ALT and AST,the contents of TG and TC,and the expression levels of CDK5,TLR4 and p-NF-κB proteins all reduced significantly.[Conclusions]Polysaccharides from D.chinensis(L.)Nees.may interfere with NAFLD by inhibiting the TLR4/NF-κB pathway.
文摘In experimental dogs,the effect of APN in alleviating the ischemiareperfusion injury was prominent.Compared with the sustained isthmian group,superoxide dismutast(SOD)in the ischemic region of myocardial tissue in the ischemiareperfusion group was significantly decreased and malondialdehyde(MDA)marktdly increased Ca2+in myocardial cells was increased. and ultrastructural changes of myocardial tisstes were severe in the APN-pretreated ischemia-reperfusion group ,on the contrary,all the above parameters showed reversely,i,e.,SOD increased ,MDA and intracellular Ca2+ decreased.the ultrastructure changes were less distorted.
文摘The aim of this project is to explore the mechanism of the treatment of alcoholic liver by means of network pharmacology and molecular docking.In this study,the chemical components of the extract of Callistephus chinensis(L.)Nees.were characterized by LC-MS/MS,identifying 6 compounds by positive and negative total ion flow maps.The target of chrysanthemum was derived from SwissTargetPrediction database,and the target related to alcoholic liver was derived from GeneCards and OMIM database.Add the target to the String database to build the protein interaction platform Microbiology software was used for GO bioprocess enrichment analysis and KEGG pathway enrichment analysis,and the target pathway network was constructed.In Discovery Studio 2016 Client software verified molecular docking,China aster flavonoids compounds and the adhesion strength of the key targets.Five potential active components were screened from the flavonoid monomer compounds of the chrysanthemum Cupressus.546 Bioprocess(BP),75 cell composition(CC)and 185·molecular function(MF)were obtained by GO enrichment analysis.KEGG enrichment analysis for each cross target involved a pathway.Network analysis showed that it was the main active component of flavonoids in the treatment of alcoholic liver,and other related signals were related to the treatment of alcoholic liver.This study showed that the flavonoids of Callistephus chinensis(L.)Nees were involved in the treatment of alcoholic liver by regulating multi-target and multi-pathway.
文摘机器学习已经广泛用于生态系统研究。基于2014年1月1日至2018年12月31日兴安落叶松生态系统碳通量(NEE)观测数据,分析了其动态变化特征,并采用多种机器学习方法进行模拟。结果表明:(1)生长季兴安落叶松生态系统NEE日动态呈“U”变化,整体表现为碳汇,7月份碳汇能力最强,达67.57 g C m^(-2)月^(-1),9月至次年5月表现为碳源。(2)结构方程模型分析表明,兴安落叶松生态系统NEE的主要影响因子为潜热通量(LE)、净辐射(Rn)、叶面积指数(LAI)、空气温度(Ta)、相对湿度(RH)、饱和水汽压差(VPD)和土壤含水量(SWC),其中潜热通量和净辐射是影响NEE变化的最主导因素。(3)四种机器学习方法(RF、XGBoost、SVM、ANN)均能较准确地模拟兴安落叶松生态系统NEE,其中XGBoost和RF的模拟结果最为相近,但XGBoost在模拟精度和计算效率方面优于RF。研究结果为应用机器学习方法估算生态系统碳通量提供了依据。
文摘针对不同陆地生态系统中净生态系统CO_(2)交换量(Net ecosystem exchange,NEE)数据的长期连续测量中存在的数据差异问题,以中国气象局青海高寒生态气象野外科学试验基地野牛沟试验站为研究对象,利用涡动协方差技术获取高寒湿地生态系统水平上的NEE数据。通过对比机器学习算法和通量数据后处理算法(Reddyproc)两种数据填充方法,提出了一种结合机器学习与时序异常检测(Time series anomaly detection,TAD)的新框架,用于NEE数据的空白填补。研究结果表明:1)Reddyproc算法在剔除异常值后,NEE插补决定系数(R^(2))达到0.67,数据离散度显著降低,数据质量提升;2)八种机器学习模型中,随机森林(Random Forest,RF)模型表现最优,其决定系数(Coefficient of determination,R^(2))为0.63,均方根误差(Root mean square error,RMSE)为2.17μmol s^(-1)m^(-2),且经过时序异常检测后,估算精度提升了17%;3)Reddyproc和RF估算的CO_(2)通量存在季节性差异,冷季(1—3月和10—12月)Reddyproc估算值低于RF,而暖季(4—9月)则高于RF,表明冬季Reddyproc低估了CO_(2)释放,夏季则低估了CO_(2)吸收。该新框架有效解决了数据采集不确定性和缺失导致的二氧化碳通量计算准确率问题,为研究高寒湿地生态系统的碳固持能力、对气候变化的响应以及极端事件的影响提供了关键数据支持。未来研究应进一步探索新方法的适用性、改进和优化方向,以实现更准确、可靠且适用于不同生态系统的填补模型,为生态系统建模和预测提供强大工具。
