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91.
Science China Earth Sciences - The Chinese government has made a strategic decision to reach ‘carbon neutrality’ before 2060. China’s terrestrial ecosystem carbon sink is... 相似文献
92.
Vicia villosa is an annual legume plant,and is mainly used for green manure by farmers in southwest China.Field growth experiments were performed on six plots.The concentrations of mineral nutrients and soluble sugar,and the changes of carbon and nitrogen isotopic composition within and among organs of Vicia were deter- mined.Significant differences in legume growth were found in response to soil type and its moisture conditions.The Vicia villosa was relatively well adapted to growth in limestone soils than sandstone soils.The distribution of sugar concentrations andδ1 3C-differences between roots and leaves indicate that the translocation of sugars from leaves to roots may be restricted by soil drought.Therefore,there was an inhibition of Pi distribution from roots to leaves, resulting in over optimum threshold of N/P ratio.Those may originate from the feedback regulation in the legume, where soluble sugar could not be distributed from leaves to roots.The results ofδ1 5N values in tissues suggest that there should be different preferential use of nitrogen resource by legume during the formation of nodules:before nodule formation the legume preferentially utilizes inorganic nitrogen from soils,but afterwards the nitrogen should be mainly from N2-fixation.Our results indicate that the lack of nodulation development,except for S2,should be ascribed to the factor controlling bi-direction nutrient transfer,which should be efficiency of establishment symbiosis with arbuscular mycorrhiza before nodulation formation.It is predicted that the species of Vicia villosa should be a legume associated with dual symbiosis with rhizobia and mycorrhiza. 相似文献
93.
我国的天文底片数字化工作已正式启动,选取高精度的扫描仪是该工作首要和基本的任务。对Epson公司的V750 Pro和10000XL,以及Phase One公司的PowerPhase FX+扫描仪开展了测试,结果表明,PowerPhase FX+具有较高的扫描精度,一方面,该扫描仪扫描方向的稳定性与线阵CCD方向相当,均优于0.5μm;另一方面,通过UCAC3参考星归算结果显示,尽管PowerPhase FX+的照相式扫描会带来像场畸变,但考虑3阶底片模型后,扫描星像的位置精度较高。对于上海天文台佘山40 cm折射望远镜1987年拍摄的M79底片,扫描星像的位置精度优于0.1″。 相似文献
94.
1IntroductionSoilorganicmatter (SOM)isakeysourceofnutrientsforplantgrowth ,itisessentialforthemaintenanceofsoilstructureanditcontributestotheabilityofsoiltoretainnutrientsandwater.AnimprovedunderstandingofSOMdynamicsiscentraltothedevelopmentofmoreenvironmentallysoundandsustainablepracticesofagriculturalmanagement (Collinsetal.,2 0 0 0 ) .Avarietyofcon ceptualmethodshavebeenusedtodescribetheprocessesofSOMaccumulationandturnover (Jen kinsonandRayner,1 977;Duxburyetal.1 989;Partonetal.,1 99… 相似文献
95.
On the basis of different photosynthetic pathways.there is an obvious difference in δ^13C values between C3 and C4 plants,In terms of this characteristic,we analyzed the organic carbon content (forestlands:1.81%-16.00%;farmland:0.45%-2.22%) and δ^13C values(forestlands:-23.86‰--27.12‰;farmland:-19.66‰--23.26‰)of three profile-soil samples either in farmland or in forestland near the Maolan Karst virgin forest,where there were developed plant C3 plants previously and now are C4 plants.Results showed that the deforestation has accelerated the decomposition rate of soil organic matter and reduced the proportion of active components in soil organic matter and thus soil fertility. 相似文献
96.
97.
TheMiddleandUpper~aninNorthCabhasbeenextenSiVelystudiedfor~yearSinbiostratigraphy(LuandDong,1953;Xiangatal.,1981;An,1982;Met,1993a,1993b).Ho~,thelithOStratigraphictntSwereunfortunatelydefinedbytrilobitezonesotherthanlithologitalcriteria,owingtothecomplicatedChangeSandt~itioninlithofades.CbnseqUentiy,thebio--,litho~andchronostrstigraphictntS~confuSed,asPOintedOuttosomeextentbyLuetal.(1994).Nevertheless,thezoningfossilsoftrilobiteSoCCUrredatthehorizonsSeparatedfromeachotherinseveralt… 相似文献
98.
SequencestratigraphyhashopaidmoreattentionforitSrelativelycompletetheoreticalsyStemandgreatsuchesinpracticesinceitwasadvancedinthe197ds.Integratingonthedataofbiostratiglaphy,lithostratigraphy,seismicstfstigraphy,geochendstryandsedirnentology,sequencestratigraphyattemptStoestablishachronostratigraphicframeworkandcormectsdepositionalsequencewithglobalsealevelchange,andhencemakeSitpossibletOpreciselycorrelatethestrataindifferentfactesareasoveraconsiderabledistance,evenovertheworld.TheUpperDevon… 相似文献
99.
乌拉山金矿主要赋存在太古宙乌拉山群变质地层中,不同类型矿脉的空间分布与华力西-印支期的大桦背花岗岩有密切的联系。Au、Ag、W等组分的正异常和Ba、Sr、Na_2O等组分的负异常的套合产出是寻找金矿脉的地球化学标志。Ti含量可作为评价矿化脉含金性的地球化学标志。根据原生异常特征和矿脉中元素的分布,推测M113矿脉在深部有尖灭再现。乌拉山群地层中金的初始富集和大桦背花岗岩的岩浆期后热液均提供了成矿物质。 相似文献
100.
混沌理论及其在地学中的应用前景 总被引:1,自引:0,他引:1
混沌理论作为一种普适性很强的新理论,在地球科学中的应用日前广泛,其意义已渐为人们所认识和关注。本文介绍了混沌在地球中的部分应用,认为混沌理论开阔了人们研究地学中复杂问题的思路;同时,地学中一些重大问题的解决也必将丰富和混沌理论。 相似文献