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1.
The influence of tree density on the grass layer of three semi-arid savanna types of southern Africa
《African Journal of Range and Forage Science》2013,30(2-3):103-109
The influence of bush density on the grass component of the herbaceous layer was investigated for three savanna veld types (Molopo Thornveld, Mixed Vaalbos Thornveld, and the Eastern Grass and Bushveld) in the Northern Cape and North-West Province of South Africa. Relationships between bush density and the density, species composition and phytomass production of the grass component were determined over a four-year period. Bush encroachment had an adverse influence on the density and production of the grass component, but not on the species composition. Fluctuations in seasonal rainfall appeared to be the most important factor governing changes in the species composition of the grass component. Bush enchroachment (2 500 tree equivalents ha?l) decreased the potential grazing capacity by as much as 331%, 149% and 58% in the Molopo Thornveld, the Mixed Vaalbos Thornveld and the Eastern Grass Bushveld, respectively, In comparison to sites with tree densities of less than 400 tree equivalents ha?1. In the encroached condition grazing capacities of 15, 13 and 10 ha LSU?1 are recommended for the Molopo Thornveld, the Mixed Vaalbos Thornveld and the Eastern Grass and Bushveld, respectively. The implementation of bush control measures in all problem areas is proposed in order to restore the productivity of these areas in the long term. 相似文献
2.
科尔沁沙地草甸草场退化的原因与植物多样性变化 总被引：20，自引：13，他引：20
对科尔沁沙地典型草甸植被主要群落的优势种群在22年间的消长和物种多样性的变化进行了研究,分析了造成草场退化的主要原因。结果表明,科尔沁沙地草甸植被已出现了严重退化现象,物种多样性和均匀度下降,生态优势度上升。牧草产量和质量显著下降,优良牧草数量减少,适口性较差和有毒有害植物增加。造成草甸草场退化的主要原因有气候的暖干化、生境干旱化、土壤盐渍化和过度放牧,其中过度放牧是造成草甸植被退化的直接原因。分析了过度放牧对群落组成、生物量、物种多样性以及对建群种根茎中营养物质含量的影响等。 相似文献
3.
H.A. Snyman 《Strength and Conditioning Journal》2013,66(2):143-156
The effect of plant and soil disturbances on seed density, species richness, and seed longevity of the soil seed bank was quantified for a semi-arid rangeland, over a 5-yr period (2002/2003–2006/2007 growing seasons). The different soil and plant treatments included fire, tillage (intended as a trampling surrogate), and blocked seed rain (simulating heavy grazing). These three experimental factors were combined in a factorial arrangement. Seed responses were evaluated in the soil seed bank before the new seed set, after the first seed production event, and after the second seed production event. Before disturbance (physical impact on the plant and soil), soil seed bank was dominated by early successional species: conversely, aboveground vegetation was mainly dominated by perennial grasses. After only 4 yr of blocked seed rain, seedling emergence of Decreaser grass species ceased totally both in the field and seed bank, with lower effect on Increaser grass species. Emergence of both Decreaser and Increaser grass species decreased in the seed bank with tillage, whereas the opposite occurred in the field. By contrast, tillage increased the emergence of weeds in the seed bank. The decrease in emergence of Decreaser grass species in both seed bank and field was still evident 4 yr after the rangeland was burnt. The grass species Themeda triandra was the most sensitive to fire in terms of seedling emergence. Blocked seed rain treatment significantly decreased (P < 0.05) species richness. Regardless of treatments applied, there was poor similarity between aboveground vegetation and the associated seed bank. Differences in the soil seed bank are likely to reflect manifested properties rather than short-term changes. Several characteristics of seed banks (species composition, seed abundance, and longevity) must be considered in order to understand the dynamics of plant communities following disturbances. 相似文献
4.
岷县草地牧草病害、有毒植物危害情况的调查 总被引：5，自引：1，他引：4
岷县天然草地总面积 2 1.9万hm2 ,通过抽样调查 ,牧草病害主要有褐斑病、白粉病、锈病、根腐病等 ,引起产草量下降 ,品质变劣 ,牧草损失 4 8.2万t/a ,经济损失达 1.2亿元。草地有毒植物共有 12科 19属 2 8种。调查了毒草分布及危害情况 ,其中小萱草和水杨梅对羊的危害极大。牲畜由于饥饿等原因误食毒草引起中毒死亡的大家畜 550 0匹 /a ,羊 750 0只 /a ,损失 1170万元 相似文献
5.
I.E. Danckwerts A.I. Aucamp H.I. Barnard 《African Journal of Range and Forage Science》2013,30(4):31-34
Abstract The most commonly occurring grass species in the False Thornveld (Acocks, 1953; veld type no. 21) were clipped before and after grazing on veld in good and poor condition at different times of the year. Herbage yield per species was expressed per unit basal tuft area, and the difference in yield before and after grazing was considered to reflect the production of available forage. Themeda triandra produced more forage than any other species at all times of the year. Sporobolus fimbriatus generally produced the second highest amount of available forage. Cymbopogon plurinodis, despite having the second highest herbage yield before grazing, was not grazed to a significant extent. On the basis of the results, Themeda triandra and Sporobolus fimbriatus were identified as key grass species in the False Thornveld of the Eastern Cape. 相似文献
6.
Abstract In a grazing trial conducted at the Dohne Agricultural Research Station, natural grassland was grazed continuously for 36 years with cattle. In a second investigation conducted on similar grassland, paddocks were grazed or rested, in all combinations of the four seasons of the year, over a ten year period. Changes in botanical composition and cover of the sward were monitored at regular intervals. The results of these investigations indicate that under a regime of non‐selective grazing the composition of Dohne Sourveld is remarkably stable. After 36 years of continuous grazing the species composition of the sward was largely maintained. Floristically Dohne Sourveld is dominated by a small number of grass species of which Andropogon appendiculatus, Elionurus muticus, Heteropogon contortus, Sporobolus africanus, Themeda triandra and Tristachya leucothrix are the most important. These species react differently to under‐utilization or increasingly severe defoliation, enabling them to be classified into decreaser or increaser categories. Severe defoliation resulted in a marked decrease in basal cover but only small changes in relative species composition. As the intensity of defoliation increases, decrease in grass cover is associated with an increase of forbs, such as Senecio retrorsus. 相似文献
7.
Many horse owners are concerned about sugar and fructosan levels in pastures and hay. While levels of these components have not changed in forages over the last century, the needs of horses have. Significant range in nonstructural carbohydrate contents of all grass species would allow for selection of varieties with lowered levels of these components. However, the grass seed industry must perceive a market for these types of grass before they would invest in the development of varieties and seed production and marketing of such types. Levels of these components currently vary with species, management, and the environment in which the plant is/has grown. Horse owners should be aware of these differences and use them to the benefit of their horses. Significantly lower levels of sugars and fructosans can be obtained by selecting grass species for low water soluble carbohydrate, then pastures can be managed or hay harvested with management practices favoring lowered nonfibrous carbohydrates. Forage can be analyzed for fructan or sugar, starch, and fructan can be estimated from nonfibrous carbohydrate analysis which is commonly determined in forage analysis. 相似文献
8.
祁连山区退化草地植被群落结构特征的研究 总被引：2，自引：0，他引：2
在以针茅和扁穗冰草为优势种的山地草原,由于放牧强度的加大,狼毒的个体数量及其在群落中的作用加强。伴随着狼毒分盖度的增加,针茅和扁穗冰草的地上生物量、密度、盖度和重要值明显下降,毒杂草呈上升趋势。草地的Shannon＿Wiener多样性指数和Pielou均匀度指数随狼毒生物量的增加呈现出由低到高再到低的变化趋势,Simpson优势度指数则呈现出相反的变化趋势;植物群落主要种的优势地位发生了明显的变化,狼毒由伴生种成为优势种,天然草原由禾本科牧草为优势种的顶级群落演替为狼毒为优势种的植被群落。初步提出了恢复该类退化草地生产力水平的对策。 相似文献
9.
Joaquín Aldabe Richard B. Lanctot Daniel Blanco Pablo Rocca Pablo Inchausti 《Strength and Conditioning Journal》2019,72(1):150-159
Grasslands are important to domestic and wild animals. Migratory shorebirds are important components of coastal rangeland ecosystems. Buff-breasted Sandpiper (BBSA, Calidris subruficollis) and American golden-plover (AMGP, Pluvialis dominica) are two insectivorous, migrant shorebirds that rely on livestock-grazed grasslands in the Southern Cone of South America during their nonbreeding season, as well as on migration in North America. We studied habitat selection of these species and contrasted their needs with livestock requirements needed to develop recommendations for grazing management that benefit wildlife and livestock production. Short grass height was positively related to BBSA and AMGP abundance, with ideal grass heights from 2 to 5 cm. However, maximum livestock production is associated with grass height over 6 cm. The amount of forest cover, which is used to provide shade to livestock, was negatively related to the occurrence of both shorebird species, likely due to higher risks of predation. Grassland improvement did not affect BBSA but negatively affected AMGP abundance. Short grass habitat was selected by both shorebird species in spite of the higher arthropod biomass in taller grasslands, suggesting that other factors besides food abundance, such as the ability to detect prey and predators, are driving habitat selection. To enhance shorebird (and other wildlife) conservation and livestock production, we recommend managers adjust grazing intensity so that grass height is > 6 cm from mid-February to September, when the Nearctic migrant shorebirds are absent, and from 2 to 5 cm from October to early February when shorebirds are present. These austral summer adjustments should be restricted to paddocks with low forest cover so that livestock production in paddocks with high forest cover remains maximized. All adjustments should be evaluated by each farmer to ensure adequate economic returns are met. 相似文献
10.
高原鼢鼠的采食造丘活动影响草地植被群落组成和结构,造成草地植被的空间异质性——土丘和植被斑块。本研究以冬季牧场中不同高原鼢鼠种群密度干扰下的植被性状为研究对象,探索植被群落组成结构对高原鼢鼠不同种群密度干扰的功能性响应。结果表明:植被高度随着鼢鼠种群密度的增加呈显著增加趋势(P<0.05),群落盖度和禾草丰富度呈显著下降趋势(P<0.05),而物种丰富度及杂类草丰富度随鼢鼠种群密度的增加表现出单峰曲线格局。地下总生物量随鼢鼠种群密度的增加呈显著下降趋势(P<0.05),杂类草生物量则表现出相反的趋势,而禾草类生物量表现出先降低后增加的趋势。由此可见,适宜密度的鼢鼠干扰有利于物种丰富度的提高,而低密度和高密度的鼢鼠干扰有利于草地中禾草生物量的提高。 相似文献
11.
皖西地区几种冷季型饲草适应性评价及营养成分比较 总被引：3，自引：0，他引：3
对引进的冷季型豆科饲草白三叶、紫花苜蓿和禾本科饲草多花黑麦草共9个品种在皖西地区进行生态适应性和营养成分比较试验,结果表明：各草种均能较好地适应当地的生态条件,能够正常完成生育期;各草种不同品种生态适应性和产草量有明显差异,营养成分含量也有显著不同. 相似文献
12.
13.
高寒牧区初建多年生禾草人工草地杂草群落特性的研究 总被引：7，自引：3，他引：4
对高寒牧区人工多年生禾草草地建植第一年杂草群落特性进行的研究结果表明 ,该区禾草人工草地杂草种类组成较为简单 (13种均为阔叶杂草 ) ,但危害很大 ,其中灰绿藜、萼果香薷、微孔草等不但生长旺盛 ,与禾草共生同期生长 ,且密度和盖度大 ,频度高 ,为该草地群落的优势杂草种。通过计算SDR4 值 ,该人工草地群落为 :灰绿藜 -萼果香薷 -禾草 ,即杂草为主的群落 ,故必须进行杂草的防除 ,否则人工草地建植失败。此外 ,通过分析还提出了杂草防除建议 相似文献
14.
初步统计，广东省共有禾草111属309种（包括27变种和亚种），大多数种类具有饲用价值，但优良牧草较少，约占总种数的32．4％。在属的组成上，单型属、单种属和寡种属占绝对优势，合计占总属数的83．8％。各草种的生活型以多年生为主，占63．1％；水分生态类型中，以中生植物为优势，所占比例为72．2％，水生或湿生禾草占7．2％，旱生禾草仅占10．7％；从光合途径来看，C4禾草占76.4％，是广东禾草的优势代谢途径。就属的区系成分而占，不同的分布区类型多达11个，其中泛热带分布型占总属数的43.2％；旧世界热带分布型占17．1％；热带亚洲至热带大洋洲分布型占10．8％；热带亚洲分布型占9．9％；再加上东亚及热带南美洲间断分布和热带亚洲至热带非洲分布类型，共95属，占总属数的85．6％，构成了广东禾草区系的主体，充分说明了广东禾草的热带性质。与邻近省区的比较结果说明，广东的禾草区系具有从温带到业热带再到热带的过渡性特点，是华夏禾草区系的核心地区之一，同时也显示了热带区系与亚热带区系有着不可分割的统一性。 相似文献
15.
典型果园生草模式及果草系统资源调控研究进展 总被引：2，自引：0，他引：2
果园生草是一种先进的果园土壤管理方式,能促进果品的优质可持续生产。我国引入果园生草措施已近40年,对生草果园小气候、土壤的物理、化学和生物学特性,以及果实产量和品质的变化等开展了较多研究,但对果园生草模式及其调控果园光热水土资源机制的系统研究还较少。本文综述了我国现有的典型果园生草模式及其运行机制,重点分析了果园生草对果园土壤水分、肥力、光照的调控机制,以及生草对果园害虫与杂草的调节作用。1)根据果园组分、系统水分和养分、草类植物种来源等的不同,果园生草有多种模式。2)适宜的果园生草可增加水分入渗,减小地表蒸发,减少水土流失;提高土壤肥力,增强土壤有益微生物活性;增加系统的光能捕获能力,改善果园光环境;增强系统抵抗杂草、病虫害能力,提高果园生产多样性和品质。3)不适宜的果草搭配和生草措施会导致果树和草类植物的水肥资源竞争,加剧土壤的水肥匮缺,影响系统生产性能。可为我国果园生草技术的深入研究与进一步推广应用提供参考。 相似文献
16.
Ombabi A Südekum KH Taube F 《Journal of animal physiology and animal nutrition》2001,85(11-12):385-405
Dynamics of changes in digestibility and feed intake by sheep of two ryegrass species during primary growth Environmental impacts can cause short-term variations in chemical composition and feeding value of grass swards during growth and maturation and induce concomitant changes of intake of these grasses by animals. Continuous digestion trials are effective in observing the dynamics of these variations. Therefore this study was conducted to evaluate the effects of maturity-related alterations in the chemical composition of two ryegrass swards during primary growth on nutrient digestibilities and feed intake by sheep. Pure swards of perennial ryegrass (Lolium perenne L., variety Gremie) and Italian ryegrass (Lolium multiflorum Lam., variety Lema) were harvested daily during primary spring growth between 23 April and 19 June 1991 and each grass was offered to a group of five sheep for ad libitum intake. A continuous digestion trial design was employed to measure daily intakes and faecal outputs of organic matter (OM) and OM constituents. Digestibility values were calculated with the assumption that faecal output of day 2 represented the undigested nutrients of the grass eaten at day 0. Based on results of a preliminary study, daily intakes and digestibilities were expressed as rolling 3-day averages. The chemical composition of the grasses varied considerably with growth. Crude protein concentrations declined from 18.3 to 5.9% of dry matter (DM) for perennial ryegrass and from 17.0 to 5.4% of DM for Italian ryegrass, whereas concentrations of some cell-wall fractions markedly increased and partly more than doubled. Fibre content was slightly greater for perennial ryegrass than for Italian ryegrass over the whole growth period. The decline of feeding value with maturity was closely related to increasing concentrations of fibre components and their declining digestibility. Intake by sheep of Italian ryegrass was higher by 3 g/kg of body weight at the beginning and at the end of the primary growth period. Digestibility of the OM was greater than 80% at the start of the experiment and still around 70% after 2 months of grass growth. The decline in DM and metabolizable energy intake was much more pronounced than the decrease of OM digestibility. This could be attributed in part to a decline in feed intake capacity of non-lactating sheep caused by increasing body fat mass. Short-term fluctuations in OM digestibilities were related to alterations of chemical composition of the grasses caused by growth and maturation, in particular variations in water-soluble carbohydrate concentrations. The two ryegrass species differed with regard to nitrogen associated with the cell-wall (NDF) and lignocellulose (ADF). Continuous digestion trials were effective in observing the dynamics of alterations in feeding value and feed intake by sheep as related to growth and maturation of two ryegrass species during primary spring growth. 相似文献
17.
混播草地竞争和促进关系是影响生产力和稳定性的重要因素,最终都通过牧草干物质产量以及草地物种的组成变化等指标表现出来。研究选择当地生产最常用的4种牧草无芒雀麦、鸭茅、红豆草、红三叶,以单播为对照,通过对2种豆/禾和3种牧草组合的混播草地牧草产量及物种组成变化进行长期监测,分析混播草地生产力的变化以及影响其稳定性的因素。结果表明:不论是单播还是混播,刈割干物质产量在年际间均表现为2017年高于2018年。放牧干物质产量在年际间均表现为2018年显著高于2017和2016年,鸭茅/红三叶混播草地除外。对2种牧草混播草地各物种干物质产量、密度及粗蛋白贡献的比例分析,从2016年到2018年,无芒雀麦干物质产量和密度所占比例均显著增加,鸭茅和红三叶干物质产量和密度所占比例均显著下降。红豆草与无芒雀麦混播时逐步降低,而与鸭茅混播时显著增加。3种牧草混播草地中,无芒雀麦和红豆草干物质产量和密度所占的比例显著增加,红三叶和鸭茅干物质产量和密度所占比例显著降低。综上所述,干旱区混播草地年际间干物质产量的消长变化主要取决于年均降水量和牧草的适应性。从混播草地干物质产量和密度的变化来看,随着年限增加,无芒雀麦和红豆草在混播草地中逐渐占据优势,鸭茅和红三叶在混播草地中逐渐处于劣势,且有消退的趋势。 相似文献
18.
黄土高原人工灌草系统不同立地条件土壤种子库特征 总被引：2，自引：0，他引：2
本研究通过野外调查取样与室内试验相结合，连续两年对黄土高原人工灌草系统不同坡向、坡位进行取样，以期对该区土壤种子库的物种组成、密度特征及其物种多样性进行初步了解。研究结果表明：该人工灌草生态系统土壤种子库共有9科，15种，其组成因坡位、坡向以及年份而异；坡向、坡位均显著影响土壤种子库物种多样性指数、丰富度指数与土壤种子库密度（P<0.05），土壤种子库密度为3 218～5 492粒·m-2，总体呈现为阴坡显著高于阳坡（P<0.05），下坡位显著高于上坡位（P<0.05）；坡位和坡向均对物种均匀性系数无显著影响；年份对土壤种子库无显著影响。上述研究可为黄土高原人工灌草系统的可持续利用与恢复提供参考依据。 相似文献
19.
水分胁迫对6种禾草叶绿体、线粒体超微结构及光合作用的影响 总被引：11，自引：2，他引：9
利用透射电镜技术,研究了水分胁迫下柳枝稷(Panicum virgatum L.)、巴哈雀稗(Paspalum notatum Flugge)、毛花雀稗(Paspalum dilatatum Poir)、羊茅黑麦草(×Festulolium Asch.et Graebn.)、草芦(Phalaris arundinnacea L.)及多年生黑麦草(Lolium perenne L.)6种禾本科牧草叶肉细胞叶绿体和线粒体超微结构的变化,并结合对叶绿素含量和光合速率的测定,分析了其生理功能对水分胁迫的响应,旨在为耐旱草种的选择、引种和选育提供形态学和生理学依据。结果表明,经过8 d水分胁迫后,6种牧草的叶绿体均膨大变圆并向细胞中央移动;叶绿体内分布有一定数量的嗜锇颗粒和少量淀粉粒,受伤害严重的叶绿体中的基粒和被膜破损;线粒体数目均增加,且对水分胁迫的耐受性强于叶绿体;光合速率的高低与叶绿体的结构变化相关。可将6种牧草分为3个不同的抗旱等级:柳枝稷和巴哈雀稗抗旱性较强,羊茅黑麦草和草芦抗旱性中等,多年生黑麦草和毛花雀稗抗旱性较弱。 相似文献
20.
B. McKenzie 《African Journal of Range and Forage Science》2013,30(4):135-138
Abstract Species composition, pattern and diversity of selected grassland communities were determined by using point samples, transects and quadrats. The continuously grazed grasslands of Dohne Sourveld generally had the richer species composition, the highest diversity and the most variable intra‐community pattern. Forb species were mainly responsible for the higher diversity in these grasslands compared with more severely disturbed sites (e.g. old fields). The intra‐community pattern was, however, determined by the relative proportions and distribution of the grass species. 相似文献