Above-and belowground biomass allocation not only influences growth of individual plants,but also influences vegetation structures and functions,and consequently impacts soil carbon input as well as terrestrial ecosys...Above-and belowground biomass allocation not only influences growth of individual plants,but also influences vegetation structures and functions,and consequently impacts soil carbon input as well as terrestrial ecosystem carbon cycling.However,due to sampling difficulties,a considerable amount of uncertainty remains about the root:shoot ratio(R/S),a key parameter for models of terrestrial ecosystem carbon cycling.We investigated biomass allocation patterns across a broad spatial scale.We collected data on individual plant biomass and systematically sampled along a transect across the temperate grasslands in Inner Mongolia as well as in the alpine grasslands on the Tibetan Plateau.Our results indicated that the median of R/S for herbaceous species was 0.78 in China's grasslands as a whole.R/S was significantly higher in temperate grasslands than in alpine grasslands(0.84 vs.0.65).The slope of the allometric relationship between above-and belowground biomass was steeper for temperate grasslands than for alpine.Our results did not support the hypothesis that aboveground biomass scales isometrically with belowground biomass.The R/S in China's grasslands was not significantly correlated with mean annual temperature(MAT) or mean annual precipitation(MAP).Moreover,comparisons of our results with previous findings indicated a large difference between R/S data from individual plants and communities.This might be mainly caused by the underestimation of R/S at the individual level as a result of an inevitable loss of fine roots and the overestimation of R/S in community-level surveys due to grazing and difficulties in identifying dead roots.Our findings suggest that root biomass in grasslands tended to have been overestimated in previous reports of R/S.展开更多
Let E and F be Hilbert spaces with unit spheres S1(E) and S1(F). Suppose that V0 S1(E)→S1(F) is a Lipschitz mapping with Lipschitz constant k=1 such that -V0[S1(E)] V0[S1(E)]. Then V0 can be extended to a real linear...Let E and F be Hilbert spaces with unit spheres S1(E) and S1(F). Suppose that V0 S1(E)→S1(F) is a Lipschitz mapping with Lipschitz constant k=1 such that -V0[S1(E)] V0[S1(E)]. Then V0 can be extended to a real linear isometric mapping V from E into F. In particular, every isometric mapping from S1(E) onto S1(F) can be extended to a real linear isometric mapping from E onto F.展开更多
In this paper,we first derive the representation theorem of onto isometric mappings in theunit spheres of l~1(F) type spaces,and then conclude that such mappings can be extended to the wholespace as real linear isomet...In this paper,we first derive the representation theorem of onto isometric mappings in theunit spheres of l~1(F) type spaces,and then conclude that such mappings can be extended to the wholespace as real linear isometrics by using a previous result of the author.展开更多
In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of real l∞-type spaces, then we conclude that such mappings can be extended to the whole space as (real) linear...In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of real l∞-type spaces, then we conclude that such mappings can be extended to the whole space as (real) linear isometries.展开更多
In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of l p (Г) (@#@(p >) 1,p ≠ 2 type spaces, and then we conclude that such mappings can be extended to the wh...In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of l p (Г) (@#@(p >) 1,p ≠ 2 type spaces, and then we conclude that such mappings can be extended to the whole space as real linear isometries by using the previous result of the author.展开更多
In this paper, we study the extension of isometries between the unit spheres of normed space E and C（Ω）. We obtain that any surjective isometry between the unit spheres of normed space E and C（Ω） can be extended...In this paper, we study the extension of isometries between the unit spheres of normed space E and C（Ω）. We obtain that any surjective isometry between the unit spheres of normed space E and C（Ω） can be extended to be a linear isometry on the whole space E and give an affirmative answer to the corresponding Tingley＇s problem （where Ω be a compact metric space）.展开更多
AIM： To investigate the role of opioid p-receptor subtype in opiate-induced constipation （OIC）.METHODS： The effect of Ioperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-w...AIM： To investigate the role of opioid p-receptor subtype in opiate-induced constipation （OIC）.METHODS： The effect of Ioperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine （ACh）. Then, decrease in muscle tone （relaxation） was characterized after cumu- lative administration of 0.1-10μ~mol/L Ioperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreat- ment to compare the changes in Ioperamide-induced relaxation.RESULTS： In addition to the delay in intestinal transit, Ioperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime,a selective opioid p-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by Ioperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K^＋ （KATP） channels, and by protein kinase A （PKA） inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate （cAMP）.CONCLUSION： Loperamide induces intestinal relaxa- tion by activation of opioid μ-2 receptors via the cAMP- PKA pathway to open KATp channels, relates to OIC.展开更多
In this paper we introduce the isometric extension problem of isometric mappings between two unit spheres. Some important results of the related problems are outlined and the recent progress is mentioned.
In this paper,we obtain that every isometry from the unit sphere S(l p (Γ)) of l p (Γ) (1 【 p 【 ∞,p≠2) onto the unit sphere S(E) of a Banach space E can be extended to be a (real) linear isometry of l p (Γ) ont...In this paper,we obtain that every isometry from the unit sphere S(l p (Γ)) of l p (Γ) (1 【 p 【 ∞,p≠2) onto the unit sphere S(E) of a Banach space E can be extended to be a (real) linear isometry of l p (Γ) onto E,so,we give an affirmative answer to the corresponding Tingley’s problem.展开更多
Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we...Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action.Thirteen young males performed isometric actions with the upper limb at different force levels.sEMG activities of the biceps brachii were recorded during the actions.Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions.sEMG activities were analyzed using the one-third band octave method,and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale.The results showed that the relationship could be expressed by a conic curve,and could be used to evaluate muscle fatigue during machine operation.展开更多
This paper considers the isometric extension problem concerning the mapping from the unitsphere S(E)of the normed space E into the unit sphere S(l~∞(Γ)).We find a condition under whichan isometry from S,(E)into S1(l...This paper considers the isometric extension problem concerning the mapping from the unitsphere S(E)of the normed space E into the unit sphere S(l~∞(Γ)).We find a condition under whichan isometry from S,(E)into S1(l~∞(Γ))can be linearly and isometrically extended to the whole space.Since l~∞(Γ)is universal with respect to isometry for normed spaces,isometric extension problemson a class of normed spaces are solved.More precisely,if E and F are two normed spaces,and ifV:S(E)→S(F)is a surjective isometry,where c(Γ)■(Γ),then Vcan be extended tobe an isometric operator defined on the whole space.展开更多
In this paper, we show that if V0 is an isometric mapping from the unit sphere of an AL-space onto the unit sphere of a Banach space E, then V0 can be extended to a linear isometry defined on the whole space.
Background The medial patellofemoral ligament （MPFL） reconstruction is popular in clinical practice for chronic patellar dislocation; however, the combination with vastus medialis advancement is rare. The aim of thi...Background The medial patellofemoral ligament （MPFL） reconstruction is popular in clinical practice for chronic patellar dislocation; however, the combination with vastus medialis advancement is rare. The aim of this study was to evaluate the clinical outcome of the combination of MPFL reconstruction with vastus medialis advancement.Methods We retrospectively analyzed 69 patients with chronic patellar dislocation between July 2004 and October 2008： twenty eight cases with isolated MPFL reconstruction （group Ⅰ）, forty one cases with the combination of MPFL reconstruction with vastus medialis advancement （group C）. All patients had CT scans available for review with knee flexion at 30 degree, on which the congruence angle, patellar tilt angle and patellar lateral shift were measured. Physical apprehension tests were examined and the redislocation was recorded. In addition, knee function was evaluated using the Kujala score and subjective questionnaires.Results Patients were followed up for a mean of 42 months （12-65 months） without a recurrent dislocation reported.Postoperatively, all indexes on CT scan were within the normal range without a statistical difference between the two groups. Results from the apprehension test showed eight patients in group Ⅰ and three in group Chad patellar lateral shift exceeding 1.5 cm with a hard end point （P 〈0.05）. The Kujala score improved significantly from 51.3±4.5 to 79.9±6.2 in group Ⅰ and from 53.7±5.2 to 83.9±6.5 in group C （P 〉0.05）. However, the subjective questionnaire revealed a significant difference （P 〈0.05）, including 12 excellent, seven good and nine fair in group Ⅰ and 30 excellent, six good and five fair in group C.Conclusion The combination of MPFL reconstruction with vastus medialis advancement is better than isolated reconstruction to improve the subjective effects and decrease the patellar instability rate for chronic patellar dislocation.展开更多
In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on th...In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on the forearm muscles from four subjects,and recorded the sEMG signals of the flexor carpi ulnaris.sEMG's median frequency(MDF) and mean frequency(MF) were extracted by short term Fourier transform(STFT),and the root mean square(RMS) of wavelet coefficients in the frequency band of 5—45 Hz was obtained by continuous wavelet transform(CWT).The results demonstrate that both MDF and MF show downward trends within 1 min; however,RMS shows an upward trend within the same time.The three parameters are closely correlated with absolute values of mean correlation coefficients greater than 0.8.It is suggested that the three parameters above can be used as reliable indicators to evaluate the level of muscle fatigue during isometric contractions.展开更多
Aims Carbon(C)and nitrogen(N)stoichiometry contributes to under-standing elemental compositions and coupled biogeochemical cycles in ecosystems.However,we know little about the temporal patterns of C:N stoichiometry d...Aims Carbon(C)and nitrogen(N)stoichiometry contributes to under-standing elemental compositions and coupled biogeochemical cycles in ecosystems.However,we know little about the temporal patterns of C:N stoichiometry during forest development.The goal of this study is to explore the temporal patterns of intraspecific and ecosystem components’variations in C:N stoichiometry and the scaling relationships between C and N at different successional stages.Methods Along forest development in a natural temperate forest,northeastern China,four age gradients were categorized into ca.10-,30-,70-and 200-year old,respectively,and three 20 m×20 m plots were set up for each age class.Leaves,branches,fine roots and fresh litter of seven dominant species as well as mineral soil at depth of 0-10 cm were sampled.A Universal CHN Elemental Analyzer was used to determine the C and N concentrations in all samples.Important Findings Intraspecific leaf C,N and C:N ratios remained stable along forest development regardless of tree species;while C,N concentrations and C:N ratios changed significantly either in branches or in fine roots,and they varied with tree species except Populus davidiana(P<0.05).For ecosystem components,we discovered that leaf C:N ratios remained stable when stand age was below ca.70 years and dominant tree species were light-demanding pioneers such as Betula platyphylla and Populus davidiana,while increased signifi-cantly at the age of ca.200 years with Pinus koraiensis as the dom-inant species.C:N ratios in branches and fresh litter did not changed significantly along forest development stages.C concentrations scaled isometrically with respect to N concentrations in mineral soil but not in other ecosystem components.Our results indicate that,leaf has a higher intraspecific C:N stoichiometric stability compared to branch and fine root,whereas for ecosystem components,shifts in species composition mainly affect C:N ratios in leaves rather than other components.This study also demonstrated that C and N remain coupl展开更多
In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped ...In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped product manifold has no points with the same constant sectional curvature c as the Lorentzian ambient, we show that such isometric immersion splits into warped product of isometric immersions.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 30870381)the Key Project of Scientific and Technical Supporting Programs Funded by the Ministry of Science & Technology of China (Grant No. 2007BAC06B01)
文摘Above-and belowground biomass allocation not only influences growth of individual plants,but also influences vegetation structures and functions,and consequently impacts soil carbon input as well as terrestrial ecosystem carbon cycling.However,due to sampling difficulties,a considerable amount of uncertainty remains about the root:shoot ratio(R/S),a key parameter for models of terrestrial ecosystem carbon cycling.We investigated biomass allocation patterns across a broad spatial scale.We collected data on individual plant biomass and systematically sampled along a transect across the temperate grasslands in Inner Mongolia as well as in the alpine grasslands on the Tibetan Plateau.Our results indicated that the median of R/S for herbaceous species was 0.78 in China's grasslands as a whole.R/S was significantly higher in temperate grasslands than in alpine grasslands(0.84 vs.0.65).The slope of the allometric relationship between above-and belowground biomass was steeper for temperate grasslands than for alpine.Our results did not support the hypothesis that aboveground biomass scales isometrically with belowground biomass.The R/S in China's grasslands was not significantly correlated with mean annual temperature(MAT) or mean annual precipitation(MAP).Moreover,comparisons of our results with previous findings indicated a large difference between R/S data from individual plants and communities.This might be mainly caused by the underestimation of R/S at the individual level as a result of an inevitable loss of fine roots and the overestimation of R/S in community-level surveys due to grazing and difficulties in identifying dead roots.Our findings suggest that root biomass in grasslands tended to have been overestimated in previous reports of R/S.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 19971046).
文摘Let E and F be Hilbert spaces with unit spheres S1(E) and S1(F). Suppose that V0 S1(E)→S1(F) is a Lipschitz mapping with Lipschitz constant k=1 such that -V0[S1(E)] V0[S1(E)]. Then V0 can be extended to a real linear isometric mapping V from E into F. In particular, every isometric mapping from S1(E) onto S1(F) can be extended to a real linear isometric mapping from E onto F.
基金supported by National Science Foundation of China(19971046)the Doctoral Programme Foundation of Ministry of Education of China
文摘In this paper,we first derive the representation theorem of onto isometric mappings in theunit spheres of l~1(F) type spaces,and then conclude that such mappings can be extended to the wholespace as real linear isometrics by using a previous result of the author.
基金This work was supported by the National Natural Science Foundation of China(Grant No.10271060)the Research Fund for the Doctoral Program of Higher Education(Grant No.20010055013).
文摘In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of real l∞-type spaces, then we conclude that such mappings can be extended to the whole space as (real) linear isometries.
基金This work was supported by the National Natural Science Foundation of China(Grant No.10271060) the Doctoral Programme Foundation of Ministry of Education of China(No.2001005513).
文摘In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of l p (Г) (@#@(p >) 1,p ≠ 2 type spaces, and then we conclude that such mappings can be extended to the whole space as real linear isometries by using the previous result of the author.
文摘In this paper, we study the extension of isometries between the unit spheres of normed space E and C（Ω）. We obtain that any surjective isometry between the unit spheres of normed space E and C（Ω） can be extended to be a linear isometry on the whole space E and give an affirmative answer to the corresponding Tingley＇s problem （where Ω be a compact metric space）.
基金Supported by A grant from E-Da Hospital (in part)
文摘AIM： To investigate the role of opioid p-receptor subtype in opiate-induced constipation （OIC）.METHODS： The effect of Ioperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine （ACh）. Then, decrease in muscle tone （relaxation） was characterized after cumu- lative administration of 0.1-10μ~mol/L Ioperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreat- ment to compare the changes in Ioperamide-induced relaxation.RESULTS： In addition to the delay in intestinal transit, Ioperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime,a selective opioid p-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by Ioperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K^＋ （KATP） channels, and by protein kinase A （PKA） inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate （cAMP）.CONCLUSION： Loperamide induces intestinal relaxa- tion by activation of opioid μ-2 receptors via the cAMP- PKA pathway to open KATp channels, relates to OIC.
基金supported by Research Foundation for Doctor Programme (Grant No. 20060055010)National Natural Science Foundation of China (Grant No. 10871101)
文摘In this paper we introduce the isometric extension problem of isometric mappings between two unit spheres. Some important results of the related problems are outlined and the recent progress is mentioned.
基金supported by Natural Science Foundation of the Education Departmentof Jiangsu Province (Grant No.09KJD110003)
文摘In this paper,we obtain that every isometry from the unit sphere S(l p (Γ)) of l p (Γ) (1 【 p 【 ∞,p≠2) onto the unit sphere S(E) of a Banach space E can be extended to be a (real) linear isometry of l p (Γ) onto E,so,we give an affirmative answer to the corresponding Tingley’s problem.
文摘Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action.Thirteen young males performed isometric actions with the upper limb at different force levels.sEMG activities of the biceps brachii were recorded during the actions.Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions.sEMG activities were analyzed using the one-third band octave method,and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale.The results showed that the relationship could be expressed by a conic curve,and could be used to evaluate muscle fatigue during machine operation.
基金Natural Science Foundation of Guangdong Province,China (Grant No.7300614)
文摘This paper considers the isometric extension problem concerning the mapping from the unitsphere S(E)of the normed space E into the unit sphere S(l~∞(Γ)).We find a condition under whichan isometry from S,(E)into S1(l~∞(Γ))can be linearly and isometrically extended to the whole space.Since l~∞(Γ)is universal with respect to isometry for normed spaces,isometric extension problemson a class of normed spaces are solved.More precisely,if E and F are two normed spaces,and ifV:S(E)→S(F)is a surjective isometry,where c(Γ)■(Γ),then Vcan be extended tobe an isometric operator defined on the whole space.
基金the Research Foundation for Doctor Programme (Grant No. 20060055010) the National Natural Science Foundation of China (Grant No. 10571090)
文摘In this paper, we show that if V0 is an isometric mapping from the unit sphere of an AL-space onto the unit sphere of a Banach space E, then V0 can be extended to a linear isometry defined on the whole space.
文摘Background The medial patellofemoral ligament （MPFL） reconstruction is popular in clinical practice for chronic patellar dislocation; however, the combination with vastus medialis advancement is rare. The aim of this study was to evaluate the clinical outcome of the combination of MPFL reconstruction with vastus medialis advancement.Methods We retrospectively analyzed 69 patients with chronic patellar dislocation between July 2004 and October 2008： twenty eight cases with isolated MPFL reconstruction （group Ⅰ）, forty one cases with the combination of MPFL reconstruction with vastus medialis advancement （group C）. All patients had CT scans available for review with knee flexion at 30 degree, on which the congruence angle, patellar tilt angle and patellar lateral shift were measured. Physical apprehension tests were examined and the redislocation was recorded. In addition, knee function was evaluated using the Kujala score and subjective questionnaires.Results Patients were followed up for a mean of 42 months （12-65 months） without a recurrent dislocation reported.Postoperatively, all indexes on CT scan were within the normal range without a statistical difference between the two groups. Results from the apprehension test showed eight patients in group Ⅰ and three in group Chad patellar lateral shift exceeding 1.5 cm with a hard end point （P 〈0.05）. The Kujala score improved significantly from 51.3±4.5 to 79.9±6.2 in group Ⅰ and from 53.7±5.2 to 83.9±6.5 in group C （P 〉0.05）. However, the subjective questionnaire revealed a significant difference （P 〈0.05）, including 12 excellent, seven good and nine fair in group Ⅰ and 30 excellent, six good and five fair in group C.Conclusion The combination of MPFL reconstruction with vastus medialis advancement is better than isolated reconstruction to improve the subjective effects and decrease the patellar instability rate for chronic patellar dislocation.
基金Supported by the National Natural Science Foundation of China(No.81222021 and No.31011130042)the National Key Technology R&D Program of the Ministry of Science and Technology of China(No.2012BAI34B02)
文摘In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on the forearm muscles from four subjects,and recorded the sEMG signals of the flexor carpi ulnaris.sEMG's median frequency(MDF) and mean frequency(MF) were extracted by short term Fourier transform(STFT),and the root mean square(RMS) of wavelet coefficients in the frequency band of 5—45 Hz was obtained by continuous wavelet transform(CWT).The results demonstrate that both MDF and MF show downward trends within 1 min; however,RMS shows an upward trend within the same time.The three parameters are closely correlated with absolute values of mean correlation coefficients greater than 0.8.It is suggested that the three parameters above can be used as reliable indicators to evaluate the level of muscle fatigue during isometric contractions.
基金This work was supported by the National Natural Science Foundation of China(31290223)the Special Research Program for Public-welfare Forestry of China(201404201)+2 种基金the Ministry of Science and Technology(2015DFA31440,2012BAD22B01)the Lecture and Study Program for Outstanding Scholars from Home and Abroad(CAFYBB2011007)the State Key Laboratory of Forest and Soil Ecology(LFSE2014-01)and the CFERN&GENE Award Funds on Ecological Paper.
文摘Aims Carbon(C)and nitrogen(N)stoichiometry contributes to under-standing elemental compositions and coupled biogeochemical cycles in ecosystems.However,we know little about the temporal patterns of C:N stoichiometry during forest development.The goal of this study is to explore the temporal patterns of intraspecific and ecosystem components’variations in C:N stoichiometry and the scaling relationships between C and N at different successional stages.Methods Along forest development in a natural temperate forest,northeastern China,four age gradients were categorized into ca.10-,30-,70-and 200-year old,respectively,and three 20 m×20 m plots were set up for each age class.Leaves,branches,fine roots and fresh litter of seven dominant species as well as mineral soil at depth of 0-10 cm were sampled.A Universal CHN Elemental Analyzer was used to determine the C and N concentrations in all samples.Important Findings Intraspecific leaf C,N and C:N ratios remained stable along forest development regardless of tree species;while C,N concentrations and C:N ratios changed significantly either in branches or in fine roots,and they varied with tree species except Populus davidiana(P<0.05).For ecosystem components,we discovered that leaf C:N ratios remained stable when stand age was below ca.70 years and dominant tree species were light-demanding pioneers such as Betula platyphylla and Populus davidiana,while increased signifi-cantly at the age of ca.200 years with Pinus koraiensis as the dom-inant species.C:N ratios in branches and fresh litter did not changed significantly along forest development stages.C concentrations scaled isometrically with respect to N concentrations in mineral soil but not in other ecosystem components.Our results indicate that,leaf has a higher intraspecific C:N stoichiometric stability compared to branch and fine root,whereas for ecosystem components,shifts in species composition mainly affect C:N ratios in leaves rather than other components.This study also demonstrated that C and N remain coupl
文摘In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped product manifold has no points with the same constant sectional curvature c as the Lorentzian ambient, we show that such isometric immersion splits into warped product of isometric immersions.
