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111.
112.
Previous experiments have shown that mixed or conjoint grazing, when two or more animal species are grazed together, can lead to improved performance of one or more of the species and a higher total output per unit area. Sequential grazing systems, when different animal species graze an area in succession, also have the potential to improve productivity. This experiment directly compared these two approaches for integrating the grazing of cattle and sheep when pastured on improved permanent pasture. Four treatments were compared: 1) sheep only from May to October (S/S); 2) cattle only from May to July followed by sheep only from August to October (C/S); 3) cattle and sheep from May to July, sheep only for the rest of the growing season (C + S/S); and 4) cattle and sheep from May to October (C + S/C + S). Each treatment was replicated three times. From May until weaning at the end of July the plots were grazed by steers and ewes and lambs, and from weaning until October by steers and lambs. Sward heights were maintained at 6 cm using a “put and take” stocking system. Animal performance and sward composition data were collected during three growing seasons, 2001–2003. During the pre-weaning period lambs grazing plots which were grazed only by sheep had significantly poorer growth rates than those grazing plots where there was mixed grazing. Lambs grazing the sheep only plots also had lower liveweight gain during the post-weaning period, with the highest growth rates being recorded on the C + S/C + S treatment. Carrying capacity and total liveweight gain per unit area post-weaning were also consistently higher for the C + S/C + S treatment, while carrying capacity pre-weaning was highest for the C/S treatment. Measurements of clover content in the grazed horizon and botanical separation of material from quadrat cuts indicated that even under relatively controlled conditions choice of grazing system can influence sward composition. However, there was no clear link between any single sward change and the growth of the animals, indicating that the improved performance of cattle and sheep under mixed grazing is the result of a combination of factors, rather than a response to a particular sward parameter. 相似文献
113.
This paper focuses on understanding human impact on landscape. Both ecological and human practices are analysed as interacting
processes. An agent-based model integrating biological and historical knowledge is used to analyse the pattern of Scots Pine
encroachment in a French Mediterranean upland. In the STIPA model, pine trees are autonomous agents and a cellular automaton
simulates land-use. We test the effects of shifting cultivation on tree establishment at the landscape scale. This allows
us to understand how agropastoral practices patterned this area from the 17th to 19th century: simulations show the importance
of shifting cultivation in limiting woodland progression. Fallow duration linked to environmental heterogeneity is a significant
factor for explaining pine dynamics and landscape patterning at the scale of the study region. We put this result in perspective
with current rangeland management policies that often consider grazing as the most relevant tool for open landscape maintenance.
Our results also show the importance of taking into account time-scale effects when linking landscape patterns to agricultural
systems. 相似文献
114.
利用遥感技术监测锡林郭勒天然草原利用强度方法初探 总被引:1,自引:0,他引:1
利用多时相的遥感数据,对2005年锡林郭勒天然草原生长期放牧利用强度进行了信息提取、监测和制图。结果表明:在牧草生长季节,天然草原各旬度的利用强度与植被指数旬度变动系数成反比,并与降雨和植被长势时空分布格局相一致;放牧初期旬度变动系数下降4%左右,利用强度较轻,处于轻度过牧状态;6月中旬以后,旬度变动系数下降12%~20%之间,利用强度加重,处于中度超载过牧状态;8月下旬后植物生长停止,旬度变动系数下降27%左右,利用强度最重,处于重度超载过牧状态。遥感监测结果经过地面同步采集数据验证,监测精度达到79.6%。 相似文献
115.
We evaluated whether new information could be drawn from additional data collection and unconventional statistical analyses of an on-farm trial. First, we compared a conventional sampling method using a biomass estimate of weed abundance to repeated visual assessment of the percentage ground cover of weeds. The biomass was sampled once after the treatment, whereas the ground cover was repeatedly sampled once before weed control plus several occasions after weed control. Second, we contrasted the outcomes from analysis of variance ( anova ), taking samples from a single point in time with repeated measures (rm) anova and a multivariate method. As the outcomes and conclusions drawn were relatively similar, we conclude that the ground cover estimate of weed abundance was as reliable as the biomass estimate. The rm anova enabled us to follow the temporal trend in response to treatments in the most abundant species, including possible initial differences. Multivariate analysis went even further, by clearly displaying species-wise responses and treatment selectivity. 相似文献
116.
北方城市地被植物应用质量评价方法探讨 总被引:5,自引:0,他引:5
根据地被植物固有的特征和北方城市配置应用特点,将地被植物分为基础型地被、骨干型地被和点缀型地被3类。运用频数统计法选择株高、生育期、观赏价值、绿色期、覆盖力、生长势、适应性、养护频度8项指标,构建了地被植物外观质量、生态质量和使用质量3大指标体系。制定评价标准,采用综合指数评价法,验证地被植物的质量等级。通过实例分析验证,该质量评价指标体系和评价方法具有较强的科学性和可操作性,评价结果符合客观实际,对于北方城市地被植物的评价选择应用,具有普遍的适应性和推广价值。 相似文献
117.
Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long‐term mean. The experiment was initiated in a 4‐yr‐old grass‐clover sward in south Denmark. Three treatments were as follows grazing only (G), spring cut followed by grazing (CG) and both spring and autumn cuts with summer grazing (CGC). Nitrate leaching was calculated by extracting water isolates from 80 cm depth using ceramic suction cups. Because of considerable variation in measured nitrate concentrations, the 32 installed suction cups per treatment were insufficient to reveal differences between treatments. However, weighted nitrate leaching estimations for G, CG and CGC showed estimated mean nitrate N concentrations of 23, 19 and 13 mg/L for an estimated proportion area occupied by urine patches of 0.33, 0.26 and 0.16, respectively. Thus, N concentrations in G and CG exceeded the EU limit of 11.3 mg N/L. Under the prevailing conditions, the time of urination did not appear important. The estimated background leaching calculated from suction cups presumably not situated under urine patches resulted in mean nitrate N concentrations of 2.6 mg/L. 相似文献
118.
试验选取6只内蒙古细毛羊健康泌乳母羊,分别于泌乳前期(Ⅰ、Ⅱ期)、泌乳中期(Ⅲ期)和泌乳后期(Ⅳ期),采用消化代谢、气体能量代谢等试验方法,运用灰色关联度分析法,探讨放牧条件下主要气候因素(气温、气湿、风速)对母羊不同泌乳期营养物质消化代谢的影响。结果表明,在本试验条件下,试验羊产热量受风速影响最大,机体能量存留量受气温影响最明显,而来食量、消化率、N存留量及总能代谢率等项指标与空气湿度关系最密切。 相似文献
119.
ABSTRACT: Kawakawa Euthynnus affinis is the most abundant species among the small tuna in the coastal waters of Taiwan. The migration pattern of kawakawa to Taiwan was determined in the present study based on the species' feeding habits and reproductive biology and on temporal variation of catch for kawakawa and its prey fishes. Schools of this species successively migrate to Taiwan from September to May, and then move away in June. They travel to the waters off Taiwan with the warm Kuroshio current, migrate toward coastal waters for feeding and move away for spawning. It is suggested in the present study that the kawakawa spawning ground is in the waters of the northern Philippines. The migration of kawakawa exhibits size-segregating behavior. Schools of immature young fish first arrive in the coastal waters around Taiwan, followed by the adults. 相似文献
120.