放牧强度对高寒草地产草量及羊体质量增加的影响

以托云牧场高寒草地为研究对象,通过设置3个放牧样地,一个对照样地,研究不同强度放牧对草地地上生物量的影响以及在不同放牧压力下羊体质量增加的效果。结果表明,1）托云牧场是以银穗草（Leucopoa albida）、羊茅（Festuca arioides）、点地梅（Androsace umbellata）和棘豆（Oxytropis falcatae）为优势种的高山草地;2）高寒草地地上生物量较低,禁牧区7月地上生物量（干物质）仅830 kg·hm-2;3）放牧活动对地上生物量有较大影响,重度放牧能显著降低牧场地上生物量;4）以羊体质量增加值为评价指标,该高寒牧场在载畜量为1.05羊单位·hm-2时能获得较好的体质量增加效果。     

不同载畜率下短花针茅草原土壤水分空间异质性的分析

以短花针茅(Stipa breviflora)草原为研究对象,采用经典统计学和地统计学的方法对不同载畜率样地(不放牧、轻度放牧、中度放牧和重度放牧)的土壤水分进行描述性统计、半变异函数及空间插值分析,旨在研究载畜率对荒漠草原土壤水分空间异质性的影响。结果表明,01)各处理的土壤含水量均随载畜率的增大而逐渐升高,各处理的变异系数(CV)在7.29%~9.79%,均呈弱变异性。2)半变异函数分析显示各处理的土壤水分含量均呈指数模型,不放牧的结构比为74.4%,属于中等程度变异。轻度、中度、重度放牧处理的结构比分别为94.4%、91.2%和96.0%,具有强烈的空间自相关性;3)利用克里格插值法对各样地的未知采样点进行插值分析,发现重度放牧处理土壤水分的空间变异程度最大,不放牧处理土壤水分的空间变异程度最低。所以,载畜率对土壤水分的空间分布有明显的影响。     

Exploratory trials on reinforcement of veld with legumes in the south‐eastern transvaal highveld

Abstract

The feasibility and potential of reinforcing veld with legumes in the south‐eastern Transvaal highveld was assessed in a number of trials during the period 1974–84. Experience was gained with regard to methods of establishment, adaptation of legumes to the local environment, responses to fertilization, especially with lime and superphosphate, and the reaction of legumes to fire and grazing. In all, 17 legumes were involved, including the genera Coronilla, Desmodium, Glycine, Lespedeza, Lotus, Macroptilium, Medicago, Neoto‐nonia, Trifolium and Vigna. Only Coronilla varia (crownvetch) showed a satisfactory degree of persistence. However, crownvetch is slow to establish, is intolerant of waterlogging and has a relatively high requirement for lime and phosphate. Considering these features, and the probability of undesirable changes in grass species composition in reinforced veld, it is recommended that intensification be achieved through development of improved pastures for use in conjunction with veld, rather than by means of veld reinforcement.     

Effects of three short-term pasture allocation methods on milk production,methane emission and grazing behaviour by dairy cows

Two short-term grazing experiments were conducted with Norwegian Red cows. In Exp 1, 24 cows were randomly assigned to one of the following three pasture allocation methods (PAM): weekly pasture allowance (7RG), grazing 1/7 of 7RG each day (1SG), or grazing as 1SG but had access to grazed part of the paddock within one week (1FG). In Exp 2, 7RG was shortened to 5 days (5RG). We hypothesized that PAM will affect sward quality, quantity, intake and production differently. Pasture chemical composition changed with advancing grazing days but were not different between treatments. Pasture intake, milk yield, and methane emission were not affected by PAM. In Exp 1, 7RG cows spent less time on grazing, whereas in Exp 2, 1FG cows spent longer on grazing than others. Patterns observed in sward quality, and behavioural and physiological adaptations of cows to short-term changes in nutrient supply may explain the observed effects.     

高寒草甸优势物种饲用品质对短期放牧的响应

为了解放牧强度对高寒草甸牧草饲用品质的影响,以青藏高原东北边缘高寒草甸为对象,研究了轻度(0.75牦牛单位·hm-2)、中度(1.00牦牛单位·hm-2)和重度(1.25牦牛单位·hm-2)放牧下优势植物珠芽蓼(Polygonum viviparum)和线叶嵩草(Kobresia capillifolia)的全氮、酸性洗涤纤维、中性洗涤纤维含量以及牧草的可吸收营养物质总量和相对饲喂价值等的变化。在放牧末期,中度放牧下牧草的植株高度显著高于其他放牧强度(P0.05)。在整个放牧期,中度放牧下牧草的全氮含量高于其他放牧强度,其中珠芽蓼的全氮含量在放牧末期显著高于重度放牧(P0.05);各放牧强度间植物的酸性和中性洗涤纤维含量在放牧末期无显著差异;中度放牧下牧草的营养价值指数整体呈上升趋势或保持稳定。在青藏高原东北边缘,3年的短期中度放牧利用有利于高寒草甸主要优势物种珠芽蓼和线叶嵩草保持较高而稳定的饲用品质。     

Rotational and continuous grazing of sheep in the Inner Mongolian steppe of China

The aim of this study was to compare the effects of rotational and continuous grazing on herbage mass (HM), organic matter digestibility (dOM) and intake (OMI) and live weight gain (LWG) of sheep grazing on the inner Mongolian steppe, China at a stocking rate of 4.5 sheep/ha during the growing season. In the years 2005 and 2006, four 2-ha plots were used of which two were divided into four 0.5 ha paddocks each for rotational grazing, where sheep were moved each 10 days to the next paddock. The dOM was estimated from faecal crude protein concentration and OMI by oral administration of titanium dioxide. Herbage mass was similar in both grazing systems and dOM and OMI were higher (p < 0.05) at continuous grazing than at rotational grazing, but LWG did not differ probably because of extra energy expenditure for grazing and walking in a larger area. The dOM and OMI decreased (p < 0.05) with progress of the growing season and differed between years. Since precipitation during the growing season in both years was lower than the 30 years average which was probably the reason that positive effects of non-grazing periods on herbage regrowth and quality at rotational grazing could not occur, further studies are required in years with average precipitations before a final evaluation of these grazing systems can be made. Moreover, it seems necessary to quantify energy expenditure for physical activity of animals in grazing studies.     

放牧强度对高寒草甸群落碳氮磷化学计量特征的影响

植被生态化学计量特征是高寒草甸生态系统稳定性的基础,但其对放牧管理的响应仍不清楚。为此,以2011年在青海海北高寒矮嵩草(Kobresia humilis)草甸建立的不同放牧强度试验地为研究对象,于2014年植物生长季的5月-9月,通过测定禁牧(对照,CK)、轻度放牧(light grazing,LG)、中度放牧(moderate grazing,MG)和重度放牧(heavy grazing,HG)样地的地上植被生产力和植被群落结构及群落叶片碳(carbon,C)、氮(nitrogen,N)、磷(phosphorus,P)含量,研究放牧强度对高寒草甸群落生态化学计量的影响。结果表明,MG能显著提高地上生物量和优良牧草禾草类植物的生物量比例,C含量的变异均在MG处理下最大,此结果支持了中度干扰理论;重牧能显著提高群落叶片的N含量(P0.05);放牧管理对叶片P含量的影响无明显规律;禁牧有利于系统N和P的周转。本研究结果显示,适度的放牧强度有利于高寒草甸生产力的提高,而禁牧可能通过改变群落优势种增强系统的N、P循环强度。     

新时期黄土高原退耕还林(草)有关问题探讨

[目的]总结黄土高原退耕还林(草)工程实施20 a来取得的成效,旨在为新时期黄河流域生态保护和高质量发展提供参考。[方法]根据多年研究结果,结合近期调研和相关资料,归纳了新时期黄土高原退耕还林(草)工程实施过程中出现的问题。[结果]当前需要考虑的问题包括:①如何加速退耕还草;②是否实行严格的轮封轮牧;③如何处理好生态林和经济林的比例;④如何持续提高单位面积粮食产量等。[结论]新时期生态建设过程中需注重分析与研究出现的新问题,寻求切实的应对方案,以推动黄土高原地区生态文明建设和乡村振兴。     

祁连山东段高寒草甸模拟放牧下的坡面土壤水蚀特征

本研究在祁连山东段高寒草甸草原采用人工模拟降雨和模拟放牧测定其坡面产流产沙过程,旨在为高寒草甸的水源涵养功能评价及以防止水土流失为前提的草地合理利用提供基础资料。结果表明：从未放牧到重度放牧径流出现的时间逐渐缩短;相较于未放牧,从轻度放牧到重度放牧的高寒草甸平均径流量分别增加150.00%,600.00%,2 200.00%,平均产沙量分别增加170.59%,535.29%,694.12%,且降雨强度对径流量的影响高于对产沙量的影响;相较于重度放牧,未放牧、轻度放牧和中度放牧3种放牧强度的平均保水效益分别为67.06%,46.04%,28.08%;固土效益分别为88.54%,70.23%,38.73%;高寒草甸的减水减沙效益与雨型具有密切关系,相关系数分别为0.967和0.961,保水效益和固土效益间有极显著的相关性,相关系数为0.995。从维持水源涵养功能的角度来说,中度以下的放牧强度是相对安全的。     

Effect of defoliation by livestock on stem canker caused by Leptosphaeria maculans in Brassica napus

Brassica napus (canola, oilseed rape), an important break crop for cereals across the Australian wheat belt, is being rapidly adopted as a dual‐purpose (forage and grain) crop in mixed farming systems. Stem canker caused by the fungus Leptosphaeria maculans is the most important disease of B. napus in Australia. The primary source of inoculum is airborne ascospores released during autumn/winter which coincides with the grazing of dual‐purpose crops. Field experiments were defoliated by sheep to determine the effect of grazing on blackleg stem canker severity at plant maturity in B. napus cultivars differing in their resistance level and grazed at different times. One cultivar was sown on different dates to investigate the impact of grazing at the same time, but at different growth stages. Defoliation by mowing was compared to defoliation by livestock. Similar amounts of dry matter remained after defoliation by machinery (0·66 t ha^?1) or livestock (0·52 t ha^?1). However, stem canker severity was higher in the grazed (40% of crown cross‐section diseased) compared with the mown (25%) treatment, which was higher than the ungrazed control (9%). Stem canker severity generally increased with grazing, but the increase was eliminated or reduced in cultivars with good resistance. Grazing during vegetative plant growth minimized the increase in stem canker severity compared with grazing during reproductive growth. Currently, cultivars with good L. maculans resistance are recommended in high disease situations. To avoid excessive yield loss in dual‐purpose B. napus crops due to L. maculans it is recommended that such cultivars are grown even in low‐moderate disease situations.