青藏高原地区积雪变化及特征分析     

张旭 《现代农业科技》2021,8(8)

利用我国高原地区1963-2002年的逐月积雪日数资料,以及1972-2011年的格点积雪月频率资料,分析、对比了两种资料在该地区的时空演变特征。结果表明：同时段的(1972-2002)站点资料与格点资料相比,空间分布其高值区与积雪日数增值区均偏西北,偏北程度大致为3~4°,偏西程度大致为2~3°,且中心更为明显。在青藏高原西侧(85°E以西),积雪日数呈整体下降趋势。两种资料的积雪日数EOF分析存在一定的偏差,这与其对应的空间分布差异及气候趋势空间分布存在的偏差相吻合。  相似文献   

我国牧草种植成本收益变化与比较     

石自忠  王明利  胡向东  崔姹 《草业科学》2017,34(4)

本研究以牧草种植户牧草及粮食作物的调研数据为基础,计算出2010-2014年主要牧草和粮食作物的成本收益基本信息,对其变化进行统计分析,并对各作物的成本收益进行比较。分析发现,2014年苜蓿(Medicago sativa)的经济效益有所下降;黑麦草(Lolium perenne)和青贮玉米(Zea mays)的纯收益和收益率有所增长;苜蓿的纯收益和收益率要高于黑麦草和青贮玉米;马铃薯(Solanum tuberosum)和苜蓿的经济效益更具优势,种植小麦(Triticum aestivum)经济效益较差;黑麦草和青贮玉米人工和土地成本更高,苜蓿水电费最高。建议调整农业产业结构,推行"粮+经+饲+草"四元种植结构,全面扶持牧草产业发展,建立健全牧草生产资料补贴制度。  相似文献   

硝酸还原酶与氮素利用的关系及其在作物遗传育种中的应用(综述)     

孙宝启  李玉京 《中国农业大学学报》1993,(3):29-34

本文综述了硝酸还原酶与氮素利用的关系及其遗传特性和在作物育种中应用的某些最新进展。氮吸收、利用等性状的生理和遗传特性极其复杂,受环境影响很大,对其进行遗传改良需考虑多种指标。对硝酸还原酶活性(NRA)与品质性状和产量的关系的争论很多,有些研究表明 NRA 可作为品质、产量性状的选择指标,有些则相反。逆境条件下 NRA 的变化非常敏感,NRA 可能与抗逆性有关。  相似文献   

Demography of Abutilon theoprasti and Setaria faberi in three crop rotation systems     

A H HEGGENSTALLER  & M LIEBMAN 《Weed Research》2006,46(2):138-151

Field experiments were conducted to characterize the demography of Abutilon theophrasti and Setaria faberi in a conventionally managed 2‐year (maize/soya bean) rotation, and in 3‐year (maize/soya bean/triticale + red clover) and 4‐year (maize/soya bean/triticale + lucerne/lucerne) rotations managed with 72% and 79% lower herbicide inputs respectively. Rates of weed seedling recruitment, seedling survival and adult plant fecundity were determined for populations in each phase of each rotation and used to calculate annual rates of weed population change, Δ. In both years of the study, Δ for A. theophrasti populations declined or remained stable in all three rotation systems. Despite greater rates of seedling survival and fecundity in maize and soya bean in the 3‐ and 4‐year rotations, increases in Δ for A. theophrasti populations were prevented in these systems because of low fecundity in triticale and low seedling survival and fecundity in lucerne. For Setaria faberi populations, Δ remained stable in the 2‐year rotation, increased in the 3‐year rotation in both years, and increased in the 4‐year rotation in 1 year. The results of this study indicate that when herbicide use is reduced, rotations that include triticale and lucerne can facilitate the suppression of A. theophrasti. Rotations that include lucerne can contribute to restraining S. faberi population growth, given adequate levels of seedling mortality in this crop.  相似文献   

松嫩平原羊草草地水淹干扰恢复过程的群落动态   总被引：16，自引：6，他引：10  

张宝田  杨允菲 《草业学报》2003,12(2):30-35

根据随机取样的测定数据，经过幂函数和多元回归分析及相关检验，揭示了草地水淹干扰对羊草 寸草苔、羊草 杂类草群范数量性状的变化规律。水淹干扰对草地植被的物种组成及其比例有明显的影响。水淹后基本恢复到正常草地的种类数量和生产量配置大约需要6—7年。随着生境水分减少和土壤变干，羊草种群的数量和生物量均以幂函数形式增加，而寸草苔和杂类草的数量和生物量则呈先增后降的变化过程。  相似文献   

An investigation of uncertainty in field habitat mapping and the implications for detecting land cover change     

Andrew Cherrill  Colin McClean 《Landscape Ecology》1995,10(1):5-21

Land cover data for landscape ecological studies are frequently obtained by field survey. In the United Kingdom, temporally separated field surveys have been used to identify the locations and magnitudes of recent changes in land cover. However, such map data contain errors which may seriously hinder the identification of land cover change and the extent and locations of rare landscape features. This paper investigates the extent of the differences between two sets of maps derived from field surveys within the Northumberland National Park in 1991 and 1992. The method used in each survey was the Phase 1 approach of the Nature Conservancy Council of Great Britain. Differences between maps were greatest for the land cover types with the smallest areas. Overall spatial correspondence between maps was found to be only 44.4%. A maximum of 14.4% of the total area surveyed was found to have undergone genuine land cover change. The remaining discrepancies, equivalent to 41.2% of the total survey area, were attributed primarily to differences of land cover interpretation between surveyors (classification error). Differences in boundary locations (positional error) were also noted, but were found to be a relatively minor source of error. The implications for the detection of land cover change and habitat mapping are discussed.  相似文献   

水稻旱作对其生长量和经济产量的影响   总被引：11，自引：0，他引：11  

黄文江  黄义德  王纪华  李金才 《干旱地区农业研究》2003,21(4):15-19

1998～1999年，研究了水稻旱作条件下，不同生育时期受水分胁迫后对作物生长量的影响。结果表明：不同指标对水分胁迫时期的敏感性不一，植株高度对抽穗期水分胁迫最敏感；单株绿叶面积和单株地上部干重对幼穗分化后期水分胁迫最敏感；根系干重和根冠比对幼穗分化前期水分胁迫最敏感；幼穗分化后期水分胁迫对经济产量影响程度最大，无效分蘖期水分胁迫对产量影响程度最小。  相似文献   

作物害虫的猖獗与高毒农药的"倾泻"的治理对策   总被引：3，自引：0，他引：3  

韩新才  黄志农  边银丙 《农药科学与管理》2003,24(4):27-29

阐述了我国农作物害虫发生现状及化学农药防治的现状，分析了作物害虫猖獗与高毒农药“倾泻”的原因与发展，提出了防止作物害虫猖獗和高毒农药“倾泻”的5条对策，即做好高毒农药危害性的宣传工作，提高农民禁用、限用高毒农药的自觉性；调整农药产品结构，大力发展生物农药；生物农药与化学农药复配，促使高毒农药低毒化；推广转基因作物；推广使用高效、高选择性、低毒、低用量、安全农药。  相似文献   

A leakiness index for assessing landscape function using remote sensing   总被引：2，自引：0，他引：2  

Ludwig  John A.  Eager  Robert W.  Bastin  Gary N.  Chewings  Vanessa H.  Liedloff  Adam C. 《Landscape Ecology》2002,17(2):157-171

The cover, number, size, shape, spatial arrangement and orientation of vegetation patches are attributes that have been used to indicate how well landscapes function to retain, not ‘leak’, vital system resources such as rainwater and soil. We derived and tested a directional leakiness index (DLI) for this resource retention function. We used simulated landscape maps where resource flows over map surfaces were directional and where landscape patch attributes were known. Although DLI was most strongly related to patch cover, it also logically related to patch number, size, shape, arrangement and orientation. If the direction of resource flow is multi-directional, a variant of DLI, the multi-directional leakiness index (MDLI) can be used. The utility of DLI and MDLI was demonstrated by applying these indices to three Australian savanna landscapes differing in their remotely sensed vegetation patch attributes. These leakiness indices clearly positioned these three landscapes along a function-dysfunction continuum, where dysfunctional landscapes are leaky (poorly retain resources). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Weed:spring barley competition for applied nitrogen in pig slurry   总被引：2，自引：0，他引：2  

J Petersen 《Weed Research》2003,43(1):33-39

Summary The experiments were carried out in the two spring barley fields of the organic six-course cattle:crop rotation at Foulumgaard, Denmark. The weed density was 300 and 1800 plants m⁻² respectively. Pig slurry was applied by hand in microplots by four methods: broadcasting followed by incorporation, or injected in bands to depths of 5, 10 or 15 cm. Spring barley and weeds were sampled separately six times during the tillering and elongation phase of the spring barley. The effect of application method on dry-matter (d.m.) production, nitrogen uptake and recovery of applied nitrogen in the spring barley and the weeds is reported. Slurry banding halved the weed d.m. and weed N uptake compared with broadcasting, irrespective of weed density. Weeds recovered up to 12% of the applied nitrogen, which made them a significant competitor when the slurry was broadcast and incorporated. Banding by direct injection reduced the slurry:soil contact and the weed:crop competition balance for applied nitrogen moved in favour of the crop. Thus, the crop recovery of applied nitrogen at the end of the sampling period was increased from approximately 45% for broadcast and incorporated to approximately 50% for injected slurry, and coincidental weed recovery was reduced to a maximum of 5%. As the nitrogen supply normally affects plant d.m. production, banding of slurry might well improve crop competitiveness and its tolerance to mechanical weed control.  相似文献