首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 109 毫秒
1.
杨粮间作系统小气候研究   总被引：4，自引：0，他引：4  
4年农田杨粮间作系统小气候测定结果表明，杨粮间作条件下农田小气候发生了明显的变化，与对照相比，毛白杨幼林使间作农田平均气温下降1.0-1.2℃，湿度提高4.1%-12.2%,风速降低32.1%-59.8%，而毛白杨成林对间作农田的影响也有相似结果，且林木的不断生长对农田的遮荫度也逐步加大。为保让间作作物产量，林木行距20m左右时其间作应不超过6年，30m行距时其间作应不超过10年。为保证间作的稳定性和长期性，建议实行大行距（30m以上）间作方式。  相似文献   

2.
农林问间系统林木遮荫及其对产量的影响   总被引：2，自引：1，他引：2       下载免费PDF全文
试验研究华北平原农区杨粮间作系统毛白杨对农田遮荫结果表明,毛白杨幼林(株行距3m×2m×18m)1～7年生遮荫指数为1.3％～67.8％,遮荫程度为0.3％～16.5％。中龄林-成林(株行距4m×30m)10～14年生遮荫指数为51.3％～76.0％,遮荫程度为22.8％～28.1％,指出10％的遮荫程度是田间可接受的最大遮荫程度,且为保持作物产量,杨树成林后行距应保持在30m以上。  相似文献   

3.
秸秆覆盖与遮荫对生姜生长及理化特性的影响   总被引：2，自引：0，他引：2  
2年试验结果表明，秸秆覆盖与遮荫均可提高土壤含水量2．4％－4．0％，降低土壤温度2．1－3．3℃。与遮荫相比，秸秆覆盖后植株高度变矮，叶片繁茂，茎秆粗壮，分枝数多，产量增加5％－14％，气孔密度、叶片厚度、气孔开张度较大；遮荫后叶绿素含量增加，硝酸还原酶活性、琥珀酸还原酶活性及产量均下降。  相似文献   

4.
对杨粮间作条件下小麦生长结果研究表明，杨树间作行距与土壤水分呈反比关系，即3～15m的行距范围内林木行距每扩大1m，土壤季平均含水量则降低1.0%，证明间作可有效减少土壤水分损失；同时林木行距与小麦叶绿素含量呈反比，说明一定程度的林木遮荫可提高小麦叶绿素含量。试验表明，小麦光合作用速率和蒸腾速率与林木行距呈正比，林木行距每增加1m，小麦的光合速率和蒸腾速率分别提高1.3μmol/m2·s和0.2μmol/m2·s，说明林木行距过小，则影响作物的光合作用，进而影响小麦的生物量和产量。通过计算，在该杨树4年林龄条件下小麦取得最大产量的行距为21～22m。  相似文献   

5.
通过对杨农间作作物营养成分（淀粉含量、脂肪含量和蛋白质含量）的测定结果表明，过小的行距（如10m)使间作农作物的营养成分降低，如小麦与花生的蛋白质含量分别下降8．4％和2．1％，脂肪含量分别下降9．6％和11．3％；间作农作物营养成分指标淀粉含量和脂肪含量呈现行中央范围优于对照，靠近树行附近的劣于对照，而蛋白质含量则呈现相反特征。  相似文献   

6.
不同森林类型林冠截留效应研究   总被引：8，自引：0，他引：8  
本文研究了7种不同森林类型林冠截留的月动态变化情况及林冠截留的水文生态效应。在一个观测期内林冠截留量随季节的变化而出现相应的变化,在雨季林冠截留量明显增大,7种不同森林类型林冠截留量的变幅从大到小的排序为：麻竹〉马占相思〉桉树〉勃氏甜龙竹〉混交林〉毛竹〉红竹。林冠截留量最大的是麻竹,最小的是毛竹,从大到小的排序为：麻竹（100．5ram）〉马占相思（62．4mm）〉勃氏甜龙竹（48．4ram）〉混交林（48．3mm）〉红竹（26．4mm）〉桉树（23．Omm）〉毛竹（10．1mm）。林冠截留率从大到小依次排序为麻竹（18．70％）〉马占相思（11．80％）〉桉树（8．56％）〉勃氏甜龙竹（8．41％）〉混交林（8．07％）〉毛竹（7．42％）〉红竹（4．10％）。结果表明：林冠层作为截留降水的第一作用层,对阻挡雨水侵蚀,减小雨滴的溅蚀,发挥了巨大的作用。  相似文献   

7.
将从培养瓶中移出的冬季（12－1月）或春季（3－4月）的香蕉组培苗置于大棚内，并在4种蔗荫水平下进行假植炼苗，相以强分别为100％（S100），33％（S33），10％（S10），3（S3）的光照条件。结果表明，不同光照强度下，单株香蕉苗的鲜茎重、鲜叶重、鲜根重、总鲜重、干茎重、干叶重、干根重和总干重都存在显著差异，但不同的生物量性状对光照强度的反应程度不同，冬季或春季遮荫均不利于单株香蕉苗的物质生产，且随遮荫程度的加重，影响愈大，同时荫还改变物质运输分配到各器官的比例。此外，春季与冬季相比，春季地上部各器官物质积累大于冬季，而冬季地下部根系的物质积累又要大于春季地下部的物质积累。  相似文献   

8.
研究总结出玉米喷施硫酸锌最佳用量为3．00kg/hm^2，拌种最佳用量为25．4g/kg，其中拌种用量远远大于资料介绍的4－6g/kg的界限。硫酸锌的增产效果为：基施（10．5％－31．5％）＞拌种（17．7％）＞喷施(14．6％）。并应用模糊聚类法对4年28点次旱地覆盖栽培玉米基施硫酸锌试验资料进行分析，得到了各类区的肥料效应方程式，利用各方程计算得到硫酸锌基施的最佳用量为23．18－31．74kg/hm^2。  相似文献   

9.
玉米不同间作方式对坡耕地水土流失的影响   总被引：6，自引：3，他引：6  
针对云南山地种植措施不合理、水土资源流失严重的现状，进行了玉米间作蔬菜和草带等不同种植方式对坡耕地水土流失影响的研究。结果表明：8月份玉米间作马铃薯的径流量比玉米裸地单作减少37．4％；7月、8月份玉米间作白菜的土壤侵蚀量比玉米裸地单作分别减少46．7％和58．2％；7，8，9，10月份玉米间作混播草带（处理G）侵蚀量分别比玉米裸地单作显著减少68．9％，74．6％，84．5％和82．1％（P〈0．01）；玉米间作白菜、间作马铃薯、间作辣椒总侵蚀量分别比玉米裸地单作显著减少47．O％，43．8％和10．2％（P〈O．01）；玉米间作草带（处理D，G）总侵蚀量分别比玉米裸地单作显著减少60．8％和70．0％（P〈0．01），玉米间作马铃薯的总径流量比玉米盖膜单作减少21．0％；在低雨强、中雨强和高雨强下，玉米间作处理的平均侵蚀量分别比玉米裸地单作减少35．7％，61．4％和70．2％。说明玉米间作蔬菜和牧草能有效减轻坡耕地水土流失，在高强度降雨中，其水土保持效果更明显。  相似文献   

10.
与梨树单作相比，梨园间作旱稻并秸秆还田后土壤容重降低了16．1％，田间持水量升高了36．9％，孔隙度升高了11．4％，有机质含量平均提高为71．1％，全氮和全磷的平均增幅分别为31．3％和4．4％，而速效氮、速效磷、速效钾的平均增幅分别为23．1％、23．6％、73．4％。梨园间作旱稻还可有效地防治水土流失，防治效率达57％-76％。  相似文献   

11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响   总被引：2，自引：2，他引：0  
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。  相似文献   

12.
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.  相似文献   

13.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

14.
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.  相似文献   

15.
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.  相似文献   

16.
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.  相似文献   

17.
Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.  相似文献   

18.
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.  相似文献   

19.
Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.  相似文献   

20.
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号