黄土高原丘陵区地形和土地利用对土壤有机碳的影响   总被引：3，自引：0，他引：3  

张祎  李鹏  肖列  赵宾华  时鹏 《土壤学报》2019,56(5):1140-1150

土壤有机碳(SOC)作为土壤中重要的组成部分及植物生长的主要元素,在地球生态系统中起着举足轻重的作用,是全球环境尤其是气候变化的重要影响因素。以黄土高原王茂沟小流域为研究对象,通过间隔为150m经纬网格分5层采集0～100cm土壤样品,采集土壤样品包括4种地形(坡顶、坡上、坡中、坡下)和5种土地利用类型(坡耕地、林地、草地、灌木、梯田),共采集土壤样品1 540个,探讨地形和土地利用方式对黄土丘陵沟壑区小流域SOC含量和分布影响,并通过Kriging插值计算流域内SOC空间分布。结果表明,黄土丘陵第一副区王茂沟小流域在0～100cm土层中,SOC平均含量坡上(4.49g·kg~(-1))和坡中(4.30 g·kg~(-1))含量最高,其次为坡下(3.97 g·kg~(-1)),坡顶SOC含量最低(3.34g·kg~(-1));坡耕地SOC含量最低。林地(4.31 g·kg~(-1))、梯田(4.25 g·kg~(-1))、草地(4.12 g·kg~(-1))和灌木(3.82 g·kg~(-1))分别较坡耕地(3.47 g·kg~(-1))SOC含量增加24.2%、22.4%、18.7%和10.1%。表层SOC更易受到环境因子的影响,梯田等水土保持措施可明显固存深层(20cm)SOC。方差成分估计表明,土地利用、地形、深度以及土地利用与地形的交互作用对流域剖面SOC含量空间分布有着极显著的影响(P0.01),其中地形对SOC含量的贡献率最高(32.50%)。土地利用与地形的交互作用在各因子的交互作用中表现出对SOC含量变异解释度最高(7.4%)。流域SOC在空间上呈斑块分布,随着深度的增加,流域SOC的空间分布向均一性发展。研究结果为黄土区水土保持措施规划及退耕还林的固碳效益评价提供了科学依据。  相似文献   

Direct and indirect effects of elevated CO2 and nitrogen addition on soil microbial communities in the rhizosphere of Bothriochloa ischaemum     

Xiao  Lie  Liu  Guobin  Li  Peng  Xue  Sha 《Journal of Soils and Sediments》2019,19(11):3679-3687

Purpose

Elevated CO₂ and nitrogen (N) addition both affect soil microbial communities, which significantly influence soil processes and plant growth. Here, we evaluated the combined effects of elevated CO₂ and N addition on the soil–microbe–plant system of the Chinese Loess Plateau.

Materials and methods

A pot cultivation experiment with two CO₂ treatment levels (400 and 800 μmol mol^?1) and three N addition levels (0, 2.5, and 5 g N m^?2 year^?1) was conducted in climate-controlled chambers to evaluate the effects of elevated CO₂ and N addition on microbial community structure in the rhizosphere of Bothriochloa ischaemum using phospholipid fatty acid (PLFA) profiles and associated soil and plant properties. Structural equation modeling (SEM) was used to identify the direct and indirect effects of the experimental treatments on the structure of microbial communities.

Results and discussion

Elevated CO₂ and N addition both increased total and fungal PLFAs. N addition alone increased bacterial, Gram-positive, and Gram-negative PLFAs. However, elevated CO₂ interacting with N addition had no significant effects on the microbial community. The SEM indicated that N addition directly affected the soil microbial community structure. Elevated CO₂ and N addition both indirectly affected the microbial communities by affecting plant and soil variables. N addition exerted a stronger total effect than elevated CO₂.

Conclusions

The results highlighted the importance of comprehensively studying soil–microbe–plant systems to deeply reveal how characteristics of terrestrial ecosystems may respond under global change.

  相似文献   

夏玉米交替灌溉施肥的水氮耦合效应研究(简报)   总被引：4，自引：0，他引：4  

薛亮  周春菊  雷杨莉  邱临静  李志军  王林权 《农业工程学报》2008,24(3):91-94

以夏玉米为研究对象进行大田试验,采用二因素四水平完全方案,随机排列,3次重复,根据玉米产量建立回归模型并对其进行解析,确定隔沟交替灌溉施肥条件下的最佳水肥配比.研究结果表明:在供试条件下水、氮对产量有明显的促进作用,而且氮素作用大于灌水作用;两因素交互作用对玉米产量的影响为正效应.供试条件下的最高产量以及相应水、氮最佳配比为:最高产量4076 kg/hm2,生育期灌水量为972m3/hm2,施氮量为230 kg/hm2.与常规灌溉相比,节水施肥模式中的水肥耦合效应对于减少水资源浪费,提高肥料利用率具有重要的理论与实践意义.  相似文献   

Repellency of insecticides and the effect of thiacloprid on bumble bee colony development in red clover (Trifolium pratense L.) seed crops     

Lars T. Havstad  John I. Øverland  Silja Valand  Trygve S. Aamlid 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2019,69(5):439-451

The study intended to compare repellency of three insecticides on bumble bees and honey bees in Norwegian red clover (Trifolium pratense L.) seed crops, and to examine effects of thiacloprid on bumble bee colony development in the field. The repellency study was carried out in a large-scale field trial in SE Norway in 2013. On average for observations during the first week after spraying, 17 and 40% less honey bees (P?=?.03) and 26 and 20% less bumble bees (P?=?.36) were observed on plots sprayed with the pyrethroids lambda-cyhalothrin and alpha-cypermethrin, respectively, than on unsprayed control plots. No pollinator repellency was found on plots sprayed with the neonicotinoid thiacloprid. Compared with unsprayed control the seed yield increases were 22% on plots sprayed with thiacloprid vs. 12–13% on plots sprayed with pyrethroids (P?=?.10). Follow-up studies in 2014–2016 focused on the effect of thiacloprid on bumble bee colony development in commercially reared nests of Bombus terrestris placed into red clover seed crops at the start of flowering. Unsprayed control crops were compared with crops sprayed either at the bud stage or when 18–44% of flower heads were in full bloom. Chemical analyses of adult bumble bees showed that thiacloprid was taken up in bees when crops were sprayed during flowering, but not detected when crops were sprayed at the bud stage. The bumble bees in late-sprayed crops also developed weaker colonies than in unsprayed crops. Dead bees with a high internal concentration of thiacloprid were found in one crop sprayed during the night at 35% flowering. This shows that thiacloprid is not bee-safe if sprayed after anthesis and that spraying has to be conducted at the bud stage to reduce its contamination of nectar and pollen.  相似文献   

Temperature Before Cold Acclimation Affects Cold Tolerance and Photoacclimation in Timothy (Phleum pratense L.), Perennial Ryegrass (Lolium perenne L.) and Red Clover (Trifolium pratense L.)          下载免费PDF全文

S. Dalmannsdottir  M. Rapacz  M. Jørgensen  L. Østrem  A. Larsen  R. Rødven  O. A. Rognli 《Journal of Agronomy and Crop Science》2016,202(4):320-330

The expected temperature rise in late summer/early autumn can change the conditions for acclimation and affect the winter survival of perennial crops. This study examined the effect of the temperature just before the onset of cold acclimation (pre‐acclimation) on freezing tolerance of timothy (Phleum pratense L.), perennial ryegrass (Lolium perenne L.) and red clover (Trifolium pratense L.) populations (both cultivars and breeding populations) adapted to either northern or southern parts of Norway. Using phytotron experiments, we studied whether increasing pre‐acclimation temperature delays growth cessation, affects photoacclimation and reduces freezing tolerance. Furthermore, we assessed whether these effects were related to the latitudinal adaptation of the plant material. The results showed that a rise in pre‐acclimation temperature decreased both cold acclimation capacity and photoacclimation in these species. This affected the freezing tolerance, which was reduced significantly more in northern‐adapted population of timothy and perennial ryegrass compared with southern‐adapted populations. Red clover was less affected by temperature changes than the grasses.  相似文献   

The genetic organisation of the capsule biosynthesis region of Actinobacillus pleuropneumoniae serotypes 1, 6, 7, and 12     

Jessing SG  Ahrens P  Inzana TJ  Angen Ø 《Veterinary microbiology》2008,129(3-4):350-359

The aim of the present study was to investigate the organisation of the genes (cps) involved in biosynthesis the capsular polysaccharide (CPS) of Actinobacillus pleuropneumoniae serotypes 6, 7, and 12 and to compare these to the corresponding genes previously described in other A. pleuropneumoniae serotypes. In serotypes 6 and 7 the sequenced DNA regions comprised five and four open reading frames, respectively, designated cps6ABCDE and cps7ABCD, whereas the sequenced DNA region in serotype 12 comprised only two open reading frames designated cps12AB. At the amino acid level, CpsA, CpsB, and CpsC of A. pleuropneumoniae serotypes 2, 6, 7, and 8 contained a high degree of homology. At the amino acid level Cps6D revealed a high degree of homology to Cps8D, whereas Cps7D contained a high degree of homology to the Cps2D. The deduced gene product of the partially sequenced cps6E gene showed no homology to any deduced gene products of any cps genes of A. pleuropneumoniae investigated so far. None of the deduced gene products of the cps genes involved in encapsulation of A. pleuropneumoniae serotypes 2, 6, 7, and 8 revealed homology to the deduced gene products of the cps genes of serotypes 1, 5A, and 12. For some genes, a local homology was found to genes probably involved in teichoic acid synthesis in other bacteria. The results obtained revealed a high degree of homology among the genes involved in CPS biosynthesis for serotypes 2, 6, 7, and 8 and a different group of homologous cps genes for serotypes 1 and 12. In some serotype 7 strains, including the serotype 7 reference strain, WF83, the cps genes were not located adjacent to the genes responsible for CPS export (cpx), probably due to genetic rearrangements.  相似文献   

Standardized gene nomenclature for the Brassica genus     

Lars Østergaard  Graham J King 《Plant methods》2008,4(1):1-4

  相似文献   

Preliminary study on the molecular mechanism of photoinhibition of rice photosynthesis Chinese Rice Research Newsletter     

ZHANG Deyu  JIAO Demao  Wu Ningyi  DI Lie  Wu Rongsheng  Maurice S.B. KU  XU Xianxiu 《水稻科学》1994,2(3):5

  相似文献   

种间杂交狗牙根足球场草坪的建植与管理技术研究   总被引：5，自引：0，他引：5  

吴彦奇  胥晓刚 《四川草原》1999,(3):40-43

本文系统地总结了 Ｔｉｆｗａｙ 足球场草坪的建植和日常养护管理技术。证明种间杂交狗牙根品种 Ｔｉｆｗａｙ 是成都地区建植足球场的理想品种,值得大力推广。  相似文献   

提高会计信息真实性的对策研究   总被引：1，自引：0，他引：1  

李瑞芬  王艳霞 《北京农学院学报》1999,14(1):68-70

本文针对目前影响会计信息真实性的主要因素,研究提高会计信息真实性的对策．影响会计信息真实性的主要因素有：会计信息本身的客观因素;考核企业、行业干部政绩、业绩机制不完善;会计人员和注册会计师的主观因素;监督机制不健全．其中,第一个因素造成会计信息的相对不真实,后三个因素造成会计信息的绝对失真．相应地有四个方面的对策：一是减少会计信息本身对会计信息的消极影响;二是完善对企业（行业、地区）干部政绩、业绩的考核机制;三是实行会计信息商品化、社会化;四是加强会计法规建设,建立健全社会监督体系  相似文献