Vegetables are key to nutrition and economic security, especially for developing societies. Research in vegetables has been historically key. From early domestication efforts to modern-day breeding and value addition,...Vegetables are key to nutrition and economic security, especially for developing societies. Research in vegetables has been historically key. From early domestication efforts to modern-day breeding and value addition, research has enabled vegetable productivity to support the nutritional and economic needs of societies. Impactful research, however, requires competent research capacity and a guiding framework, in a continuously changing socio-climatic world. Vegetable research appraisal in Malawi, especially regarding capacity, focus, and a guiding framework, is lacking. By using 5 search engines and 506 analyzed publications, this review sought to first examine the existing research capacity in Malawi and assess the vegetable research focus in terms of both value chain analysis themes and specific vegetable tax. This approach allowed for the isolation and flagging out of key emerging issues from existing research that positively contextualize future vegetable research direction in Malawi. It has been found that Malawi has adequate institutional and expertise capacity to further vegetable research. The identified challenges include local funding and infrastructural capacity to leverage donor funding. Three key emerging issues of climate change, modeling, and biofortification in vegetable crops have been identified. It is suggested that, with Malawi facing the climate change challenge, research focus in these areas, will enhance not only nutritional and economic security, but also overall climate change readiness. Key to climate change readiness is the involvement of indigenous vegetable production. As a package, vegetable cultivation can play a critical role in contributing to the achievement of pillar 1 of the Malawi vision 2063, which seeks to leverage agricultural productivity and commercialization with a focus on climate change resilience.展开更多
Many riparian（Tugai） forests growing along rivers in arid and hyper-arid regions of Central Asia are dominated by the Euphrates poplar（Populus euphratica）. Besides generative reproduction, which is only possible u...Many riparian（Tugai） forests growing along rivers in arid and hyper-arid regions of Central Asia are dominated by the Euphrates poplar（Populus euphratica）. Besides generative reproduction, which is only possible upon flooding events and at a distance to the groundwater of less than 2 m, this phreatophytic tree species also reproduces vegetatively by forming clones that can cover land surface areas of several hectares. Along a gradient of groundwater distances, we investigated whether the fraction of clones in P. euphratica stands（1） increases with increasing distance to the water table;（2） is higher if supplied with water via river cut-offs; and（3） approaches 100% at a short distance to the groundwater, but at high salt concentrations in the upper soil layers, which would prevent germination and establishment of seedlings. AFLP（Amplified Fragment Length Polymorphism） analyses were conducted on leaf samples taken from mature P. euphratica trees growing at the fringes of the Taklimakan Desert in stands with different distances（2–12 m） to the groundwater at two plots at the middle and the lower reaches of the Tarim River and in a stand close to Ebinur Lake, Xinjiang, China. Genetic diversity was large among plots, but considerably smaller within plots. We found the highest genetic diversity（caused by regeneration from seeds） at plots that have a short distance to the groundwater or are supplied with additional water. There was no significant relationship between groundwater distance and clonal fraction. All investigated trees at the saline Ebinur Lake site belonged to one single clone. Our results demonstrate that the genetic pattern of this widespread species is not easily predictable even over small distances as it is a result of a complex interplay of stand history and dispersal of propagules（pollen, seeds, and vegetative diaspores） by wind and water. In conservation and restoration schemes, P. euphratica stands with a high genetic diversity and stands that grow at short distances to the water table and are regularly subjected to flooding（which favors generative over clonal reproduction） should be prioritized.展开更多
AIM: To summarize the evidence from randomized controlled trials(RCTs) on the rehabilitation effects of recreational activities.METHODS: Studies were eligible if they were RCTs. Studies included one treatment group in...AIM: To summarize the evidence from randomized controlled trials(RCTs) on the rehabilitation effects of recreational activities.METHODS: Studies were eligible if they were RCTs. Studies included one treatment group in which recreational activity was applied. We searched the following databases from 1990 to May 31, 2012: MEDLINE via Pub Med, CINAHL, Web of Science, and Ichushi-Web. We also searched all Cochrane Databases and Campbell Systematic Reviews up to May 31, 2012. RESULTS: Eleven RCTs were identified, which included many kinds of target diseases and/or symptoms such as stroke, dementia, Parkinson's disease, acquired brain injury,chronic non-malignant pain, adolescent obesity, high-risk pregnancy, and the frail elderly. Various intervention methods included gaming technology, music, dance, easy rider wheelchair biking, leisure education programs, and leisure tasks. The RCTs conducted have been of relatively low quality. A meta-analysis(pooled sample; n = 44, two RCTs) for balance ability using tests such as "Berg Balance Scale" and "Timed Up and Go Test" based on game intervention revealed no significant difference between interventions and controls. In all other interventions, there were one or more effects on psychological status, balance or motor function, and adherence as primary or secondary outcomes.CONCLUSION: There is a potential for recreational activities to improve rehabilitation-related outcomes, particularly in psychological status, balance or motor function, and adherence.展开更多
Cimicifuga simplex Wormsk. (Ranunculaceae) is a perennial herb distributed in eastern and northeastern Asia for which at least three different pollination morphs have been reported. It is classified as endangered or n...Cimicifuga simplex Wormsk. (Ranunculaceae) is a perennial herb distributed in eastern and northeastern Asia for which at least three different pollination morphs have been reported. It is classified as endangered or near threatened in some Japanese regions, and its rhizome is commercially used as a crude drug. To examine genetic differentiation and gene flow among the three morphs, we developed eight microsatellite markers by using next-generation sequencing and estimated the genetic structure of C. simplex. We tested eight primer pairs on 93 individuals from six populations of C. simplex in Nagano, central Japan, and found that heterozygosity in morphs I and III was low compared to expected heterozygosity. Bayesian clustering performed with the STRUCTURE program clearly distinguished the three morphs of C. simplex, and only a little gene flow was detected among the morphs. These eight microsatellite markers are expected to be useful in conservation genetic studies of this species and for future conservation planning.展开更多
Erythronium japonicum is a representative species of spring ephemeral, forest floor plants in substitution forests in Japan. Seed germination tests were conducted to observe the effects of temperature, light, and mois...Erythronium japonicum is a representative species of spring ephemeral, forest floor plants in substitution forests in Japan. Seed germination tests were conducted to observe the effects of temperature, light, and moisture content on the germination of E. japonicum. E. japonicum seeds did not germinate at constant temperatures of 5°C, 10°C, 15°C, 20°C, or 25°C. Seeds germinated at 5°C and 10°C after storage at 20°C for 1 or 2 months. Seed germinability was affected by desiccation to only 40% moisture content. Seeds germinated well in both light and dark conditions. Conditions under the leaf litter layer showed unique characteristics of temperature, light, and moisture content. The temperature was around 20°C under the leaf litter layer, even though it was 30°C above. The moisture content under the leaf litter layer was higher than that above. The leaf litter blocked out the sunlight. The temperature of 20°C necessary for E. japonicum germination occurred below, but not above, the leaf litter layer. The avoidance of decreasing in germinability from reduced seed moisture content in a short time is consistent with the high moisture conditions under the leaf litter layer. The leaf litter layer plays an important role in providing optimal conditions of temperature, light, and moisture content for the germination of E. japonicum seeds.展开更多
The increasing production and use of engineered silver nanoparticles（AgNP） in industry and private households are leading to increased concentrations of AgNP in the environment. An ecological risk assessment of AgNP...The increasing production and use of engineered silver nanoparticles（AgNP） in industry and private households are leading to increased concentrations of AgNP in the environment. An ecological risk assessment of AgNP is needed, but it requires understanding the long term effects of environmentally relevant concentrations of AgNP on the soil microbiome. Hence, the aim of this study was to reveal the long-term effects of AgNP on soil microorganisms. The study was conducted as a laboratory incubation experiment over a period of one year using a loamy soil and AgNP concentrations ranging from 0.01 to 1 mg AgNP/kg soil. The short term effects of AgNP were, in general, limited.However, after one year of exposure to 0.01 mg AgNP/kg, there were significant negative effects on soil microbial biomass（quantified by extractable DNA; p = 0.000） and bacterial ammonia oxidizers（quantified by amo A gene copy numbers; p = 0.009）. Furthermore, the tested AgNP concentrations significantly decreased the soil microbial biomass, the leucine aminopeptidase activity（quantified by substrate turnover; p = 0.014）, and the abundance of nitrogen fixing microorganisms（quantified by nif H gene copy numbers; p = 0.001）. The results of the positive control with Ag NO3 revealed predominantly stronger effects due to Ag＋ion release. Thus, the increasing toxicity of AgNP during the test period may reflect the long-term release of Ag^＋ions. Nevertheless, even very low concentrations of AgNP caused disadvantages for the microbial soil community, especially for nitrogen cycling, and our results confirmed the risks of releasing AgNP into the environment.展开更多
Aims Along central-Asian rivers in arid regions,lowering of the ground-water level constitutes a major threat to the riparian forests,whose tree layers are dominated by Euphrates poplar(Populus euphratica).Some of the...Aims Along central-Asian rivers in arid regions,lowering of the ground-water level constitutes a major threat to the riparian forests,whose tree layers are dominated by Euphrates poplar(Populus euphratica).Some of these fragile ecosystems are supplied with additional(‘eco-logical’)water for protection and conservation.We investigated interrelationships among groundwater distance,stand structure and above-ground wood production(at the tree and the stand level)in P.euphratica stands along a groundwater gradient(distances of 2.0-12.0 m)that also included a plot supplied with‘ecological water’.Methods We measured the height,diameter at breast height and basal area of poplar trees and determined the annual above-ground wood production for the three most recent years on the basis of tree-ring analyses and allometric regressions at three sites at the upper,mid-dle and lower reaches of the tarim River,Xinjiang,NW china.Important Findingsthe distribution of age classes differed significantly among the plots:in accordance with their life histories,stands growing at a larger distance to the groundwater harboured a larger fraction of old trees(>80 years)and,in most cases,a smaller fraction of young trees(≤20 years).the annual above-ground wood production per ha was highest on a plot with a short groundwater distance(2.0 m;maxi-mum of the 3-year investigation period:3.0 t ha−1 a−1)and lowest,at a plot with a large distance to the water table(6.6 m;minimum:0.23 t ha^(−1)a^(−1)).However,the plot located close to the groundwater(and to the river)at the middle reaches exhibited a relatively large interannual variation in above-ground wood production,which can be attributed to interannual variations in the river discharge.At the middle and the lower reaches,these interannual variations on plots with the most favourable water supply were even more obvious at the tree level.For the fraction of mature trees(60-99 years old),no significant differences in above-ground wood production were found between the plots with the most and the least favourable water supply.Overall,the productivity at the stand level was most closely correlated with the stand density(number of trees per ha,tree cover percentage).Productivity was negatively related to tree age,whereas groundwater distance alone was not a good predictor of above-ground wood production.In conclusion,vigorous growth of P.euphratica is possible at sites with groundwater distances of up to 12 m.Supply with‘ecological water’may be beneficial to trees growing at groundwater distances not larger than~6 m.However,allocation of water should focus on stands with a short distance to the groundwater because only under these conditions,natural gen-erative reproduction of the poplars is possible.展开更多
Aims We tested whether—in addition to weather conditions—the concentrations of nitrogen and phosphorus in the substrate have an effect on the radial stem increment of Nothofagus dombeyi trees in old-growth forest st...Aims We tested whether—in addition to weather conditions—the concentrations of nitrogen and phosphorus in the substrate have an effect on the radial stem increment of Nothofagus dombeyi trees in old-growth forest stands on volcanic soil at the western slopes of the Andes in South-Central Chile.Methods We took soil samples and tree increment cores from five proximate sites(1000-1300 m a.s.l.)that are located in the volcanic region of the Conguillío National Park and differ in the age of the substrate(Miocene—3500 years B.P.)and in its concentrations of nitrogen(N)and phosphorus(P).The soil samples were also analysed on their concentrations of other plant mineral nutrients,carbon(C)and nitrogen isotope ratios(δ^(15)N).Tree-ring widths and the stem basal area increment(BAI)were related to climate parameters.In selected tree rings,the stable isotope ratios of carbon(δ^(13)C)and oxygen(δ^(18)O)were determined and related to growth and climate parameters.Important FindingsConsistent with theory,the soils on the oldest substrate showed the highest(least negative)δ^(15)N values,but mineral N was the only nutrient whose concentration exhibited a straightforward(increasing)relationship with increasing substrate age.The BAI was largest on the soil with the highest concentration of plant-available P.In contrast to BAI,tree-ring chronologies did not differ among the study sites.However,tree-ring chronologies and BAI exhibited significantly positive correlations with summer precipitation,and negative correlations,with summer(December)temperature.A negative correlation was found betweenδ^(13)C and precipitation anomalies in the growing season(November-March).We interpret the negative correlations between growth and temperature,and betweenδ^(13)C andδ^(18)O in the tree rings,as an impairment of net carbon assimilation by anomalously warm weather conditions during the growing season.We conclude that the growth of N.dombeyi is mainly affected by high temperature and low precipitation in spring and summer irrespective of the substrate’s age,and enhanced by higher concentrations of plant-available P in the soil.Our results may be representative of N.dombeyi stands on volcanic substrate within their principal distribution range along the Andes of South America.展开更多
Aims Nothofagus species are constitutive elements of the temperate forests along the Southern Andes Mountains.The deciduous Nothofagus alpina is a fast-growing,but long-lived opportunistic pioneer spe-cies(‘pioneer-c...Aims Nothofagus species are constitutive elements of the temperate forests along the Southern Andes Mountains.The deciduous Nothofagus alpina is a fast-growing,but long-lived opportunistic pioneer spe-cies(‘pioneer-climax species’)and co-occurs with the evergreen N.dombeyi.We tested whether N.alpina is competitively superior to N.dombeyi in mature stands and whether intra-specific competition in N.alpina is stronger than inter-specific competition with N.dombeyi.Methods In a pristine old-growth forest in South-Central Chile,we compared the growth of N.alpina trees in pure stands and in mixture with N.dombeyi to the growth of N.dombeyi and calculated compe-tition indices.We related growth variables to climate data and weather extremes.Important Findings In N.alpina,juvenile basal area increment was signifi-cantly higher in pure than in mixed stands.Contrary to our hypothesis,N.dombeyi exhibited larger radial stem increments than N.alpina in the most recent 40 years.In the most recent two decades,this was caused by high growth rates of large N.dombeyi trees.In both Nothofagus species,stem growth was negatively related to temperature,but N.dombeyi responded more sensitively to weather conditions than N.alpina.In N.alpina,stem increment was negatively related to the intensity of competition,but the size of the competition effects on this species was similar in pure and mixed stands.Thus,compared to N.alpina,the‘pioneer-climax species’concept is even more appropriate for N.dombeyi with its relatively high growth rates even in the early stages of its life.展开更多
文摘Vegetables are key to nutrition and economic security, especially for developing societies. Research in vegetables has been historically key. From early domestication efforts to modern-day breeding and value addition, research has enabled vegetable productivity to support the nutritional and economic needs of societies. Impactful research, however, requires competent research capacity and a guiding framework, in a continuously changing socio-climatic world. Vegetable research appraisal in Malawi, especially regarding capacity, focus, and a guiding framework, is lacking. By using 5 search engines and 506 analyzed publications, this review sought to first examine the existing research capacity in Malawi and assess the vegetable research focus in terms of both value chain analysis themes and specific vegetable tax. This approach allowed for the isolation and flagging out of key emerging issues from existing research that positively contextualize future vegetable research direction in Malawi. It has been found that Malawi has adequate institutional and expertise capacity to further vegetable research. The identified challenges include local funding and infrastructural capacity to leverage donor funding. Three key emerging issues of climate change, modeling, and biofortification in vegetable crops have been identified. It is suggested that, with Malawi facing the climate change challenge, research focus in these areas, will enhance not only nutritional and economic security, but also overall climate change readiness. Key to climate change readiness is the involvement of indigenous vegetable production. As a package, vegetable cultivation can play a critical role in contributing to the achievement of pillar 1 of the Malawi vision 2063, which seeks to leverage agricultural productivity and commercialization with a focus on climate change resilience.
基金funded by the German Federal Ministry of Education and Research(01LL0918K)
文摘Many riparian（Tugai） forests growing along rivers in arid and hyper-arid regions of Central Asia are dominated by the Euphrates poplar（Populus euphratica）. Besides generative reproduction, which is only possible upon flooding events and at a distance to the groundwater of less than 2 m, this phreatophytic tree species also reproduces vegetatively by forming clones that can cover land surface areas of several hectares. Along a gradient of groundwater distances, we investigated whether the fraction of clones in P. euphratica stands（1） increases with increasing distance to the water table;（2） is higher if supplied with water via river cut-offs; and（3） approaches 100% at a short distance to the groundwater, but at high salt concentrations in the upper soil layers, which would prevent germination and establishment of seedlings. AFLP（Amplified Fragment Length Polymorphism） analyses were conducted on leaf samples taken from mature P. euphratica trees growing at the fringes of the Taklimakan Desert in stands with different distances（2–12 m） to the groundwater at two plots at the middle and the lower reaches of the Tarim River and in a stand close to Ebinur Lake, Xinjiang, China. Genetic diversity was large among plots, but considerably smaller within plots. We found the highest genetic diversity（caused by regeneration from seeds） at plots that have a short distance to the groundwater or are supplied with additional water. There was no significant relationship between groundwater distance and clonal fraction. All investigated trees at the saline Ebinur Lake site belonged to one single clone. Our results demonstrate that the genetic pattern of this widespread species is not easily predictable even over small distances as it is a result of a complex interplay of stand history and dispersal of propagules（pollen, seeds, and vegetative diaspores） by wind and water. In conservation and restoration schemes, P. euphratica stands with a high genetic diversity and stands that grow at short distances to the water table and are regularly subjected to flooding（which favors generative over clonal reproduction） should be prioritized.
基金Supported by Grant-in-Aid for Scientific Research(C)from the Ministry of Education,Culture,Sports,Science and Technology(MEXT),Japan,No.23500817
文摘AIM: To summarize the evidence from randomized controlled trials(RCTs) on the rehabilitation effects of recreational activities.METHODS: Studies were eligible if they were RCTs. Studies included one treatment group in which recreational activity was applied. We searched the following databases from 1990 to May 31, 2012: MEDLINE via Pub Med, CINAHL, Web of Science, and Ichushi-Web. We also searched all Cochrane Databases and Campbell Systematic Reviews up to May 31, 2012. RESULTS: Eleven RCTs were identified, which included many kinds of target diseases and/or symptoms such as stroke, dementia, Parkinson's disease, acquired brain injury,chronic non-malignant pain, adolescent obesity, high-risk pregnancy, and the frail elderly. Various intervention methods included gaming technology, music, dance, easy rider wheelchair biking, leisure education programs, and leisure tasks. The RCTs conducted have been of relatively low quality. A meta-analysis(pooled sample; n = 44, two RCTs) for balance ability using tests such as "Berg Balance Scale" and "Timed Up and Go Test" based on game intervention revealed no significant difference between interventions and controls. In all other interventions, there were one or more effects on psychological status, balance or motor function, and adherence as primary or secondary outcomes.CONCLUSION: There is a potential for recreational activities to improve rehabilitation-related outcomes, particularly in psychological status, balance or motor function, and adherence.
文摘Cimicifuga simplex Wormsk. (Ranunculaceae) is a perennial herb distributed in eastern and northeastern Asia for which at least three different pollination morphs have been reported. It is classified as endangered or near threatened in some Japanese regions, and its rhizome is commercially used as a crude drug. To examine genetic differentiation and gene flow among the three morphs, we developed eight microsatellite markers by using next-generation sequencing and estimated the genetic structure of C. simplex. We tested eight primer pairs on 93 individuals from six populations of C. simplex in Nagano, central Japan, and found that heterozygosity in morphs I and III was low compared to expected heterozygosity. Bayesian clustering performed with the STRUCTURE program clearly distinguished the three morphs of C. simplex, and only a little gene flow was detected among the morphs. These eight microsatellite markers are expected to be useful in conservation genetic studies of this species and for future conservation planning.
文摘Erythronium japonicum is a representative species of spring ephemeral, forest floor plants in substitution forests in Japan. Seed germination tests were conducted to observe the effects of temperature, light, and moisture content on the germination of E. japonicum. E. japonicum seeds did not germinate at constant temperatures of 5°C, 10°C, 15°C, 20°C, or 25°C. Seeds germinated at 5°C and 10°C after storage at 20°C for 1 or 2 months. Seed germinability was affected by desiccation to only 40% moisture content. Seeds germinated well in both light and dark conditions. Conditions under the leaf litter layer showed unique characteristics of temperature, light, and moisture content. The temperature was around 20°C under the leaf litter layer, even though it was 30°C above. The moisture content under the leaf litter layer was higher than that above. The leaf litter blocked out the sunlight. The temperature of 20°C necessary for E. japonicum germination occurred below, but not above, the leaf litter layer. The avoidance of decreasing in germinability from reduced seed moisture content in a short time is consistent with the high moisture conditions under the leaf litter layer. The leaf litter layer plays an important role in providing optimal conditions of temperature, light, and moisture content for the germination of E. japonicum seeds.
基金supported by the Federal Ministry of Education and Research of Germany(Research unit Nano Umwelt,funding code 03X0150C)
文摘The increasing production and use of engineered silver nanoparticles（AgNP） in industry and private households are leading to increased concentrations of AgNP in the environment. An ecological risk assessment of AgNP is needed, but it requires understanding the long term effects of environmentally relevant concentrations of AgNP on the soil microbiome. Hence, the aim of this study was to reveal the long-term effects of AgNP on soil microorganisms. The study was conducted as a laboratory incubation experiment over a period of one year using a loamy soil and AgNP concentrations ranging from 0.01 to 1 mg AgNP/kg soil. The short term effects of AgNP were, in general, limited.However, after one year of exposure to 0.01 mg AgNP/kg, there were significant negative effects on soil microbial biomass（quantified by extractable DNA; p = 0.000） and bacterial ammonia oxidizers（quantified by amo A gene copy numbers; p = 0.009）. Furthermore, the tested AgNP concentrations significantly decreased the soil microbial biomass, the leucine aminopeptidase activity（quantified by substrate turnover; p = 0.014）, and the abundance of nitrogen fixing microorganisms（quantified by nif H gene copy numbers; p = 0.001）. The results of the positive control with Ag NO3 revealed predominantly stronger effects due to Ag＋ion release. Thus, the increasing toxicity of AgNP during the test period may reflect the long-term release of Ag^＋ions. Nevertheless, even very low concentrations of AgNP caused disadvantages for the microbial soil community, especially for nitrogen cycling, and our results confirmed the risks of releasing AgNP into the environment.
基金German Federal Ministry of Education and Research(BMBF),Funding Measure‘Sustainable Land Management’(project number:01LL0918K).
文摘Aims Along central-Asian rivers in arid regions,lowering of the ground-water level constitutes a major threat to the riparian forests,whose tree layers are dominated by Euphrates poplar(Populus euphratica).Some of these fragile ecosystems are supplied with additional(‘eco-logical’)water for protection and conservation.We investigated interrelationships among groundwater distance,stand structure and above-ground wood production(at the tree and the stand level)in P.euphratica stands along a groundwater gradient(distances of 2.0-12.0 m)that also included a plot supplied with‘ecological water’.Methods We measured the height,diameter at breast height and basal area of poplar trees and determined the annual above-ground wood production for the three most recent years on the basis of tree-ring analyses and allometric regressions at three sites at the upper,mid-dle and lower reaches of the tarim River,Xinjiang,NW china.Important Findingsthe distribution of age classes differed significantly among the plots:in accordance with their life histories,stands growing at a larger distance to the groundwater harboured a larger fraction of old trees(>80 years)and,in most cases,a smaller fraction of young trees(≤20 years).the annual above-ground wood production per ha was highest on a plot with a short groundwater distance(2.0 m;maxi-mum of the 3-year investigation period:3.0 t ha−1 a−1)and lowest,at a plot with a large distance to the water table(6.6 m;minimum:0.23 t ha^(−1)a^(−1)).However,the plot located close to the groundwater(and to the river)at the middle reaches exhibited a relatively large interannual variation in above-ground wood production,which can be attributed to interannual variations in the river discharge.At the middle and the lower reaches,these interannual variations on plots with the most favourable water supply were even more obvious at the tree level.For the fraction of mature trees(60-99 years old),no significant differences in above-ground wood production were found between the plots with the most and the least favourable water supply.Overall,the productivity at the stand level was most closely correlated with the stand density(number of trees per ha,tree cover percentage).Productivity was negatively related to tree age,whereas groundwater distance alone was not a good predictor of above-ground wood production.In conclusion,vigorous growth of P.euphratica is possible at sites with groundwater distances of up to 12 m.Supply with‘ecological water’may be beneficial to trees growing at groundwater distances not larger than~6 m.However,allocation of water should focus on stands with a short distance to the groundwater because only under these conditions,natural gen-erative reproduction of the poplars is possible.
基金supported by the State of Vietnam through a PhD grant to L.T.H.(Grant No.4358/QĐ-BGDĐT)by the Deutscher Akadamischer Austauschdienst(DAADProject No.57163751)through covering travel costs of R.S.and F.M.T.
基金Fondo Nacional de Desarrollo Científico y Tecnológico(Fondecyt),Chile(Fondecyt Regular 1090135).
文摘Aims We tested whether—in addition to weather conditions—the concentrations of nitrogen and phosphorus in the substrate have an effect on the radial stem increment of Nothofagus dombeyi trees in old-growth forest stands on volcanic soil at the western slopes of the Andes in South-Central Chile.Methods We took soil samples and tree increment cores from five proximate sites(1000-1300 m a.s.l.)that are located in the volcanic region of the Conguillío National Park and differ in the age of the substrate(Miocene—3500 years B.P.)and in its concentrations of nitrogen(N)and phosphorus(P).The soil samples were also analysed on their concentrations of other plant mineral nutrients,carbon(C)and nitrogen isotope ratios(δ^(15)N).Tree-ring widths and the stem basal area increment(BAI)were related to climate parameters.In selected tree rings,the stable isotope ratios of carbon(δ^(13)C)and oxygen(δ^(18)O)were determined and related to growth and climate parameters.Important FindingsConsistent with theory,the soils on the oldest substrate showed the highest(least negative)δ^(15)N values,but mineral N was the only nutrient whose concentration exhibited a straightforward(increasing)relationship with increasing substrate age.The BAI was largest on the soil with the highest concentration of plant-available P.In contrast to BAI,tree-ring chronologies did not differ among the study sites.However,tree-ring chronologies and BAI exhibited significantly positive correlations with summer precipitation,and negative correlations,with summer(December)temperature.A negative correlation was found betweenδ^(13)C and precipitation anomalies in the growing season(November-March).We interpret the negative correlations between growth and temperature,and betweenδ^(13)C andδ^(18)O in the tree rings,as an impairment of net carbon assimilation by anomalously warm weather conditions during the growing season.We conclude that the growth of N.dombeyi is mainly affected by high temperature and low precipitation in spring and summer irrespective of the substrate’s age,and enhanced by higher concentrations of plant-available P in the soil.Our results may be representative of N.dombeyi stands on volcanic substrate within their principal distribution range along the Andes of South America.
基金This work was supported by Fondo Nacional de Desarrollo Científico y Tecnológico(Fondecyt http://www.conicyt.cl/fon-decyt/)Chile Fondecyt Regular 1130353 and the International Collaboration Program DFG-Conicyt PCCI12040 http://www.conicyt.cl/pci/program-of-international-relations/.
文摘Aims Nothofagus species are constitutive elements of the temperate forests along the Southern Andes Mountains.The deciduous Nothofagus alpina is a fast-growing,but long-lived opportunistic pioneer spe-cies(‘pioneer-climax species’)and co-occurs with the evergreen N.dombeyi.We tested whether N.alpina is competitively superior to N.dombeyi in mature stands and whether intra-specific competition in N.alpina is stronger than inter-specific competition with N.dombeyi.Methods In a pristine old-growth forest in South-Central Chile,we compared the growth of N.alpina trees in pure stands and in mixture with N.dombeyi to the growth of N.dombeyi and calculated compe-tition indices.We related growth variables to climate data and weather extremes.Important Findings In N.alpina,juvenile basal area increment was signifi-cantly higher in pure than in mixed stands.Contrary to our hypothesis,N.dombeyi exhibited larger radial stem increments than N.alpina in the most recent 40 years.In the most recent two decades,this was caused by high growth rates of large N.dombeyi trees.In both Nothofagus species,stem growth was negatively related to temperature,but N.dombeyi responded more sensitively to weather conditions than N.alpina.In N.alpina,stem increment was negatively related to the intensity of competition,but the size of the competition effects on this species was similar in pure and mixed stands.Thus,compared to N.alpina,the‘pioneer-climax species’concept is even more appropriate for N.dombeyi with its relatively high growth rates even in the early stages of its life.
