In the present research,we describe a computer-aided detection(CAD)method aimed at automatic fetal head circumference(HC)measurement in 2D ultrasonography pictures during all trimesters of pregnancy.The HC might be ut...In the present research,we describe a computer-aided detection(CAD)method aimed at automatic fetal head circumference(HC)measurement in 2D ultrasonography pictures during all trimesters of pregnancy.The HC might be utilized toward determining gestational age and tracking fetal development.This automated approach is particularly valuable in low-resource settings where access to trained sonographers is limited.The CAD system is divided into two steps:to begin,Haar-like characteristics were extracted from ultrasound pictures in order to train a classifier using random forests to find the fetal skull.We identified the HC using dynamic programming,an elliptical fit,and a Hough transform.The computer-aided detection(CAD)program was well-trained on 999 pictures(HC18 challenge data source),and then verified on 335 photos from all trimesters in an independent test set.A skilled sonographer and an expert in medicine personally marked the test set.We used the crown-rump length(CRL)measurement to calculate the reference gestational age(GA).In the first,second,and third trimesters,the median difference between the standard GA and the GA calculated by the skilled sonographer stayed at 0.7±2.7,0.0±4.5,and 2.0±12.0 days,respectively.The regular duration variance between the baseline GA and the health investigator’s GA remained 1.5±3.0,1.9±5.0,and 4.0±14 a couple of days.The mean variance between the standard GA and the CAD system’s GA remained between 0.5 and 5.0,with an additional variation of 2.9 to 12.5 days.The outcomes reveal that the computer-aided detection(CAD)program outperforms an expert sonographer.When paired with the classifications reported in the literature,the provided system achieves results that are comparable or even better.We have assessed and scheduled this computerized approach for HC evaluation,which includes information from all trimesters of gestation.展开更多
The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UH...The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.展开更多
BACKGROUND The incidence and mortality rate of colorectal cancer progressively increase with age and become particularly prominent after the age of 50 years.Therefore,the population that is≥50 years in age requires l...BACKGROUND The incidence and mortality rate of colorectal cancer progressively increase with age and become particularly prominent after the age of 50 years.Therefore,the population that is≥50 years in age requires long-term and regular colonoscopies.Uncomfortable bowel preparation is the main reason preventing patients from undergoing regular colonoscopies.The standard bowel preparation regimen of 4-L polyethylene glycol(PEG)is effective but poorly tolerated.AIM To investigate an effective and comfortable bowel preparation regimen for hospitalized patients≥50 years in age.METHODS Patients were randomly assigned to group 1(2-L PEG+30-mL lactulose+a lowresidue diet)or group 2(4-L PEG).Adequate bowel preparation was defined as a Boston bowel preparation scale(BBPS)score of≥6,with a score of≥2 for each segment.Non-inferiority was prespecified with a margin of 10%.Additionally,the degree of comfort was assessed based on the comfort questionnaire.RESULTS The proportion of patients with a BBPS score of≥6 in group 1 was not significantly different from that in group 2,as demonstrated by intention-to-treat(91.2%vs 91.0%,P=0.953)and per-protocol(91.8%vs 91.0%,P=0.802)analyses.Furthermore,in patients≥75 years in age,the proportion of BBPS scores of≥6 in group 1 was not significantly different from that in group 2(90.9%vs 97.0%,P=0.716).Group 1 had higher comfort scores(8.85±1.162 vs 7.59±1.735,P<0.001),longer sleep duration(6.86±1.204 h vs 5.80±1.730 h,P<0.001),and fewer awakenings(1.42±1.183 vs 2.04±1.835,P=0.026)than group 2.CONCLUSION For hospitalized patients≥50 years in age,the bowel preparation regimen comprising 2-L PEG+30-mL lactulose+a low-residue diet produced a cleanse that was as effective as the 4-L PEG regimen and even provided better comfort.展开更多
BACKGROUND Hospice care plays an important role in improving the quality of life of advanced cancer patients,but controversy remains over whether age affects the attitudes of family members toward hospice care.AIM To ...BACKGROUND Hospice care plays an important role in improving the quality of life of advanced cancer patients,but controversy remains over whether age affects the attitudes of family members toward hospice care.AIM To investigate the attitudes of family members of advanced cancer patients of different ages toward hospice care.METHODS The study participants were 175 family members of patients with advanced cancer from January 2020 and October 2022.The participants were divided into youth(<40 years,n=65),middle-aged(40–60 years,n=59),and elderly(>60 years,n=51)groups.Researchers investigated and compared the degree of awareness regarding hospice care,attitudes,and whether the family members of patients would choose hospice care.RESULTS Among the family members of 175 patients,approximately 28%(49/175)were aware of hospice care.Awareness of hospice care,the proportion of hospice care acceptance and adaptation attitudes,and the proportion of those who chose hospice care in the youth group were higher in the middle-aged and elderly groups(P<0.05).No statistically significant difference was found in these three indicators between the middle-aged and elderly groups(P>0.05).Hospice care was chosen mainly to relieve pain and reduce unnecessary treatment,whereas the reasons for not choosing hospice care were mainly distrust and ethical concerns.CONCLUSION The family members of patients with advanced cancer had relatively low awareness of hospice care,while youth had a higher awareness of hospice care,acceptance,and adaptation attitudes,and were more willing to choose hospice care.展开更多
研究锌离子络合法快速分离纯化荞麦壳黄酮工艺,并评价纯化组分对晚期糖基化终末产物(AGEs)生成的抑制活性。根据络合转化率和络合强度,将荞麦壳黄酮提取物(BHF)经过二次锌离子络合,分别获得荞麦壳黄酮中间提取物(IBHF)和荞麦壳高黄酮组...研究锌离子络合法快速分离纯化荞麦壳黄酮工艺,并评价纯化组分对晚期糖基化终末产物(AGEs)生成的抑制活性。根据络合转化率和络合强度,将荞麦壳黄酮提取物(BHF)经过二次锌离子络合,分别获得荞麦壳黄酮中间提取物(IBHF)和荞麦壳高黄酮组分(HBHF)。采用Box-Behnken响应曲面分析法优化获得IBHF组分的最佳工艺参数:乙酸锌与样品质量比2∶1,乙醇体积分数30%,氨水体积分数0.05%,室温反应10 min。在该条件下络合转化率为97.44%。IBHF组分经过二次锌离子络合,分离获得HBHF组分,其总黄酮含量为57.08 g RE/100 g(三氯化铝-乙酸盐比色法),其纯度比分离纯化前提高了6.64倍。高效液相色谱分析(HPLC)表明,HBHF组分含有异荭草素、牡荆素、异牡荆素、芦丁、山奈酚-3-O芸香糖苷5种主要黄酮,其中芦丁占比62.34%。HBHF组分表现出良好的抗AGEs活性,在质量浓度为200μg/mL时,Glu-BSA体系的中的AGEs抑制率为63.16%,MGO-BSA体系中的AGEs抑制率为42.98%,抑制率均显著优于阳性对照氨基胍。展开更多
Aiming at the problem of long time-consuming and low accuracy of existing age estimation approaches,a new age estimation method using Gabor feature fusion,and an improved atomic search algorithm for feature selection ...Aiming at the problem of long time-consuming and low accuracy of existing age estimation approaches,a new age estimation method using Gabor feature fusion,and an improved atomic search algorithm for feature selection is proposed.Firstly,texture features of five scales and eight directions in the face region are extracted by Gabor wavelet transform.The statistical histogram is introduced to encode and fuse the directional index with the largest feature value on Gabor scales.Secondly,a new hybrid feature selection algorithm chaotic improved atom search optimisation with simulated annealing(CIASO-SA)is presented,which is based on an improved atomic search algorithm and the simulated annealing algorithm.Besides,the CIASO-SA algorithm introduces a chaos mechanism during atomic initialisation,significantly improving the convergence speed and accuracy of the algorithm.Finally,a support vector machine(SVM)is used to get classification results of the age group.To verify the performance of the proposed algorithm,face images with three resolutions in the Adience dataset are tested.Using the Gabor real part fusion feature at 48�48 resolution,the average accuracy and 1-off accuracy of age classification exhibit a maximum of 60.4%and 85.9%,respectively.Obtained results prove the superiority of the proposed algorithm over the state-of-the-art methods,which is of great referential value for application to the mobile terminals.展开更多
Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic...Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.展开更多
Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In ...Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In this study,carbon(C),nitrogen(N),and phosphorus(P)concentrations were evaluated in plant tissues(trees,shrubs,and herbs),litter,and soil of young(≤40-year-old),middle-aged(41–60-year-old),near-mature(61–80-year-old),and mature(81–120-year-old)Quercus secondary forests on the Loess Plateau,China.Vegetation composition,plant biomass,and C stock were determined to illustrate their interaction with stoichiometry.Only tree biomass C signifi cantly increased with stand development.Leaf N and trunk P concentrationsgenerally increased,but branch P decreased with growth stage.Fine roots had the highest C and P concentrations at the middle-aged stage.In contrast,shrubs,herbs,litter,and soil C:N:P stoichiometry did not change signifi cantly during stand development.Leaf N and P were positively correlated with soil C,N,P,and their ratios.However,there was no signifi cant correlation between litter and leaves in terms of C:N:P stoichiometry.A redundancy analysis showed that soil N best explained leaf N and P variance,and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass.Hierarchical partitioning analysis indicated that,compared with soil or litter variables,stand age only accounted for a relatively small proportion of leaf C,N,and P variation.Thus,secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging.The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development,provide novel insights into the adaptation strategies of plants in diff erent organs and growth stages,and could be used to guide fertilization programs and optimize forest structure.展开更多
Haloxylon ammodendron, with its tolerance of drought, high temperature, and salt alkali conditions, is one of the main sand-fixing plant species in the oasis-desert transition zone in China. This study used the TDP30(...Haloxylon ammodendron, with its tolerance of drought, high temperature, and salt alkali conditions, is one of the main sand-fixing plant species in the oasis-desert transition zone in China. This study used the TDP30(where TDP is the thermal dissipation probe) to measure hourly and daily variations in the stem sap flow velocity of H. ammodendron at three age-classes(10, 15, and 20 years old,which were denoted as H10, H15, and H20, respectively) in the Minqin oasis-desert transition zone,China, from May through October 2020. By simultaneously monitoring temperature, relative humidity,photosynthetically active radiation, wind speed, net radiation, rainfall, and soil moisture in this region, we comprehensively investigated the stem sap flow velocity of different-aged H. ammodendron plants(H10,H15, and H20) and revealed its response to physical factors. The results showed that, on sunny days, the hourly variation curves of the stem sap flow velocity of H. ammodendron plants at the three age-classes were mainly unimodal. In addition, the stem sap flow velocity of H. ammodendron plants decreased significantly from September to October, which also delayed its peak time of hourly variation. On rainy days, the stem sap flow velocity of H. ammodendron plants was multimodal and significantly lower than that on sunny days.Average daily water consumption of H. ammodendron plants at H10, H15, and H20 was 1.98, 2.82, and 1.91kg/d, respectively. Temperature was the key factor affecting the stem sap flow velocity of H. ammodendron at all age-classes. Net radiation was the critical factor influencing the stem sap flow velocity of H.ammodendron at H10 and H15;however, for that at H20, it was vapor pressure deficit. The stem sap flow velocity of H. ammodendron was highly significantly correlated with soil moisture at the soil depths of 50and 100 cm, and the correlation was strengthened with increasing stand age. Altogether, our results revealed the dynamic changes of the stem sap flow velocity in different-aged H. ammodendron forest stands and its response mechanism to local physical factors, which provided a theoretical basis for the construction of new protective forests as well as the restoration and protection of existing ones in this region and other similar arid regions in the world.展开更多
文摘In the present research,we describe a computer-aided detection(CAD)method aimed at automatic fetal head circumference(HC)measurement in 2D ultrasonography pictures during all trimesters of pregnancy.The HC might be utilized toward determining gestational age and tracking fetal development.This automated approach is particularly valuable in low-resource settings where access to trained sonographers is limited.The CAD system is divided into two steps:to begin,Haar-like characteristics were extracted from ultrasound pictures in order to train a classifier using random forests to find the fetal skull.We identified the HC using dynamic programming,an elliptical fit,and a Hough transform.The computer-aided detection(CAD)program was well-trained on 999 pictures(HC18 challenge data source),and then verified on 335 photos from all trimesters in an independent test set.A skilled sonographer and an expert in medicine personally marked the test set.We used the crown-rump length(CRL)measurement to calculate the reference gestational age(GA).In the first,second,and third trimesters,the median difference between the standard GA and the GA calculated by the skilled sonographer stayed at 0.7±2.7,0.0±4.5,and 2.0±12.0 days,respectively.The regular duration variance between the baseline GA and the health investigator’s GA remained 1.5±3.0,1.9±5.0,and 4.0±14 a couple of days.The mean variance between the standard GA and the CAD system’s GA remained between 0.5 and 5.0,with an additional variation of 2.9 to 12.5 days.The outcomes reveal that the computer-aided detection(CAD)program outperforms an expert sonographer.When paired with the classifications reported in the literature,the provided system achieves results that are comparable or even better.We have assessed and scheduled this computerized approach for HC evaluation,which includes information from all trimesters of gestation.
基金supported by the National Nature Science Foundation of China(Grant no.41972050).
文摘The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.
基金The study was approved by the Ethics Committee of Beijing Tongren Hospital Affiliated to Capital Medical University(Approval No.TRECKY2021-227).
文摘BACKGROUND The incidence and mortality rate of colorectal cancer progressively increase with age and become particularly prominent after the age of 50 years.Therefore,the population that is≥50 years in age requires long-term and regular colonoscopies.Uncomfortable bowel preparation is the main reason preventing patients from undergoing regular colonoscopies.The standard bowel preparation regimen of 4-L polyethylene glycol(PEG)is effective but poorly tolerated.AIM To investigate an effective and comfortable bowel preparation regimen for hospitalized patients≥50 years in age.METHODS Patients were randomly assigned to group 1(2-L PEG+30-mL lactulose+a lowresidue diet)or group 2(4-L PEG).Adequate bowel preparation was defined as a Boston bowel preparation scale(BBPS)score of≥6,with a score of≥2 for each segment.Non-inferiority was prespecified with a margin of 10%.Additionally,the degree of comfort was assessed based on the comfort questionnaire.RESULTS The proportion of patients with a BBPS score of≥6 in group 1 was not significantly different from that in group 2,as demonstrated by intention-to-treat(91.2%vs 91.0%,P=0.953)and per-protocol(91.8%vs 91.0%,P=0.802)analyses.Furthermore,in patients≥75 years in age,the proportion of BBPS scores of≥6 in group 1 was not significantly different from that in group 2(90.9%vs 97.0%,P=0.716).Group 1 had higher comfort scores(8.85±1.162 vs 7.59±1.735,P<0.001),longer sleep duration(6.86±1.204 h vs 5.80±1.730 h,P<0.001),and fewer awakenings(1.42±1.183 vs 2.04±1.835,P=0.026)than group 2.CONCLUSION For hospitalized patients≥50 years in age,the bowel preparation regimen comprising 2-L PEG+30-mL lactulose+a low-residue diet produced a cleanse that was as effective as the 4-L PEG regimen and even provided better comfort.
文摘BACKGROUND Hospice care plays an important role in improving the quality of life of advanced cancer patients,but controversy remains over whether age affects the attitudes of family members toward hospice care.AIM To investigate the attitudes of family members of advanced cancer patients of different ages toward hospice care.METHODS The study participants were 175 family members of patients with advanced cancer from January 2020 and October 2022.The participants were divided into youth(<40 years,n=65),middle-aged(40–60 years,n=59),and elderly(>60 years,n=51)groups.Researchers investigated and compared the degree of awareness regarding hospice care,attitudes,and whether the family members of patients would choose hospice care.RESULTS Among the family members of 175 patients,approximately 28%(49/175)were aware of hospice care.Awareness of hospice care,the proportion of hospice care acceptance and adaptation attitudes,and the proportion of those who chose hospice care in the youth group were higher in the middle-aged and elderly groups(P<0.05).No statistically significant difference was found in these three indicators between the middle-aged and elderly groups(P>0.05).Hospice care was chosen mainly to relieve pain and reduce unnecessary treatment,whereas the reasons for not choosing hospice care were mainly distrust and ethical concerns.CONCLUSION The family members of patients with advanced cancer had relatively low awareness of hospice care,while youth had a higher awareness of hospice care,acceptance,and adaptation attitudes,and were more willing to choose hospice care.
文摘研究锌离子络合法快速分离纯化荞麦壳黄酮工艺,并评价纯化组分对晚期糖基化终末产物(AGEs)生成的抑制活性。根据络合转化率和络合强度,将荞麦壳黄酮提取物(BHF)经过二次锌离子络合,分别获得荞麦壳黄酮中间提取物(IBHF)和荞麦壳高黄酮组分(HBHF)。采用Box-Behnken响应曲面分析法优化获得IBHF组分的最佳工艺参数:乙酸锌与样品质量比2∶1,乙醇体积分数30%,氨水体积分数0.05%,室温反应10 min。在该条件下络合转化率为97.44%。IBHF组分经过二次锌离子络合,分离获得HBHF组分,其总黄酮含量为57.08 g RE/100 g(三氯化铝-乙酸盐比色法),其纯度比分离纯化前提高了6.64倍。高效液相色谱分析(HPLC)表明,HBHF组分含有异荭草素、牡荆素、异牡荆素、芦丁、山奈酚-3-O芸香糖苷5种主要黄酮,其中芦丁占比62.34%。HBHF组分表现出良好的抗AGEs活性,在质量浓度为200μg/mL时,Glu-BSA体系的中的AGEs抑制率为63.16%,MGO-BSA体系中的AGEs抑制率为42.98%,抑制率均显著优于阳性对照氨基胍。
基金Scientific Research Project of Hebei Administration of Traditional Chinese Medicine(2020136)Science Research Project of Hebei Education Department(ZD2022043)。
文摘Aiming at the problem of long time-consuming and low accuracy of existing age estimation approaches,a new age estimation method using Gabor feature fusion,and an improved atomic search algorithm for feature selection is proposed.Firstly,texture features of five scales and eight directions in the face region are extracted by Gabor wavelet transform.The statistical histogram is introduced to encode and fuse the directional index with the largest feature value on Gabor scales.Secondly,a new hybrid feature selection algorithm chaotic improved atom search optimisation with simulated annealing(CIASO-SA)is presented,which is based on an improved atomic search algorithm and the simulated annealing algorithm.Besides,the CIASO-SA algorithm introduces a chaos mechanism during atomic initialisation,significantly improving the convergence speed and accuracy of the algorithm.Finally,a support vector machine(SVM)is used to get classification results of the age group.To verify the performance of the proposed algorithm,face images with three resolutions in the Adience dataset are tested.Using the Gabor real part fusion feature at 48�48 resolution,the average accuracy and 1-off accuracy of age classification exhibit a maximum of 60.4%and 85.9%,respectively.Obtained results prove the superiority of the proposed algorithm over the state-of-the-art methods,which is of great referential value for application to the mobile terminals.
基金funded by the National Nature Science Foundation of China (No.32171775,31770671)。
文摘Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.
基金supported by the National Nature Science Foundation of China(No.41977418 and 42130717)National Key R&D Program of China(2016YFC0501703 and 2017YFC0504605)CAS“Light of West China”Program(XAB201702).
文摘Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In this study,carbon(C),nitrogen(N),and phosphorus(P)concentrations were evaluated in plant tissues(trees,shrubs,and herbs),litter,and soil of young(≤40-year-old),middle-aged(41–60-year-old),near-mature(61–80-year-old),and mature(81–120-year-old)Quercus secondary forests on the Loess Plateau,China.Vegetation composition,plant biomass,and C stock were determined to illustrate their interaction with stoichiometry.Only tree biomass C signifi cantly increased with stand development.Leaf N and trunk P concentrationsgenerally increased,but branch P decreased with growth stage.Fine roots had the highest C and P concentrations at the middle-aged stage.In contrast,shrubs,herbs,litter,and soil C:N:P stoichiometry did not change signifi cantly during stand development.Leaf N and P were positively correlated with soil C,N,P,and their ratios.However,there was no signifi cant correlation between litter and leaves in terms of C:N:P stoichiometry.A redundancy analysis showed that soil N best explained leaf N and P variance,and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass.Hierarchical partitioning analysis indicated that,compared with soil or litter variables,stand age only accounted for a relatively small proportion of leaf C,N,and P variation.Thus,secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging.The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development,provide novel insights into the adaptation strategies of plants in diff erent organs and growth stages,and could be used to guide fertilization programs and optimize forest structure.
基金supported by the National Natural Science Foundation of China Subsidization Project (32260425, 31860238)the Natural Science Foundation of Gansu Province, China (32060246, 21JR7RA733)。
文摘Haloxylon ammodendron, with its tolerance of drought, high temperature, and salt alkali conditions, is one of the main sand-fixing plant species in the oasis-desert transition zone in China. This study used the TDP30(where TDP is the thermal dissipation probe) to measure hourly and daily variations in the stem sap flow velocity of H. ammodendron at three age-classes(10, 15, and 20 years old,which were denoted as H10, H15, and H20, respectively) in the Minqin oasis-desert transition zone,China, from May through October 2020. By simultaneously monitoring temperature, relative humidity,photosynthetically active radiation, wind speed, net radiation, rainfall, and soil moisture in this region, we comprehensively investigated the stem sap flow velocity of different-aged H. ammodendron plants(H10,H15, and H20) and revealed its response to physical factors. The results showed that, on sunny days, the hourly variation curves of the stem sap flow velocity of H. ammodendron plants at the three age-classes were mainly unimodal. In addition, the stem sap flow velocity of H. ammodendron plants decreased significantly from September to October, which also delayed its peak time of hourly variation. On rainy days, the stem sap flow velocity of H. ammodendron plants was multimodal and significantly lower than that on sunny days.Average daily water consumption of H. ammodendron plants at H10, H15, and H20 was 1.98, 2.82, and 1.91kg/d, respectively. Temperature was the key factor affecting the stem sap flow velocity of H. ammodendron at all age-classes. Net radiation was the critical factor influencing the stem sap flow velocity of H.ammodendron at H10 and H15;however, for that at H20, it was vapor pressure deficit. The stem sap flow velocity of H. ammodendron was highly significantly correlated with soil moisture at the soil depths of 50and 100 cm, and the correlation was strengthened with increasing stand age. Altogether, our results revealed the dynamic changes of the stem sap flow velocity in different-aged H. ammodendron forest stands and its response mechanism to local physical factors, which provided a theoretical basis for the construction of new protective forests as well as the restoration and protection of existing ones in this region and other similar arid regions in the world.
