【作者】 万里强；

【导师】 苏加楷；

【作者基本信息】 中国农业科学院 ， 动物营养与饲料科学， 2001， 博士

【摘要】 本研究于1999年5月—9月和2000年6月—9月在湖北省长阳县贺家坪天然灌丛草地上进行。试验分为三个处理：对照、轻牧和重牧，并在此基础上选用9只当地羯山羊，较系统地研究了灌丛草地在不同山羊放牧率下的群落结构、生产力和营养价值动态以及在不同放牧强度下山羊对灌丛草地植物的喜食性变化。 试验结果表明：（1）试验地区灌木植物的冠幅（D）与当年生枝叶产量和地上生物量（Y）均呈显著正相关（p＜0.01）：Y=a·D，a为常数，因灌木种的不同而不同。（2）本试验中，灌丛草地植物粗蛋白含量最高的是灌木植物黄檀，其次是宜昌木蓝和美丽胡枝子，它们嫩枝叶干物质的粗蛋白含量分别为17%、16%和15.7%，而草本植物芒的粗蛋白含量最低，仅为4.6%。（3）试验结果表明，轻牧条件下灌木在山羊日粮中的比例均高于重牧：1999年7月轻牧为62%，重牧为55%，9月轻牧为78%，重牧为51%，2000年6月轻牧为61.2%，重牧为44.4%，8月轻牧为36.2%，重牧为23.2%；1999年试验中，山羊对灌木植物的喜食性指数为33%，且极显著高于草本植物（p＜0.01），而禾草和杂类草的喜食性指数分别仅为9%和4%，2000年的试验中，灌木、禾草和杂类草的喜食性指数分别为21.3%、13%和11.6%，且三者的喜食性指数间没有显著差异（p＞0.05）。（4）试验发现，在对照、轻牧和重牧处理下，三峡地区灌丛草地禾草、灌木和杂类草的产量组成依次分别为：3.7：1.5∶1、5.3∶1.6∶1、1.5∶1.2∶1，故灌丛草地植物的产量主要取决于禾草的季节消长，其产量动态变化趋势与总产草量的变化基本一致；9月份（9月23日测定）产草量最高，对照、轻牧和重牧三个处理的总产草量分别为3042.8DM kg/ha、2518.4 DM kg/ha和1180.3 DM kg/ha，总体来看，随放牧强度的增加，灌丛草地中禾草的月平均地上生物量依次递减；充足的降雨量为植物在一定程度内补偿生长或超补偿生长提供了保障，从而补充了被家畜采食掉的生物量。6月份生长季降雨量是8月份的1倍。8月份降雨严重不足，故8月份轻度和重度放牧下，灌丛草地植物的净初级生长量都低于对照，都表现出欠补偿生长的特性。6月份轻牧处理下灌丛草地植物的净生长量最高，分别比对照和重牧高出99DM kg/ha和61 DM kg/ha，这说明6月份灌丛草地在轻度利用下，表现超补偿生长，而在重牧利用下，逐渐表现出欠补偿生长趋势；从6月的平均放牧利用率来看，山羊对灌丛草地三类植物的放牧利用程度由大到小依次分别为：禾草、杂类草和灌木，它们的平均放牧利用率分别为53.4％、40.4％和9.1％；从8月的平均放牧利用率来看，山羊对灌丛草地三类植物的放牧利用程度由大到小依次分别为：杂类草、禾草和灌木，它们的平均放牧利用率分别为73％、47.4％和39％。（5）试验结果表明：对照区灌木群落的物种多样性和均匀度指数随季节的推移变化不大，两者的平均值分别为2.0873和0.8715，轻牧区灌木群落的物种多样性和均匀度指数总体上呈下降趋势，其下降幅度分别为 10二2％和 16．07％，重牧区灌木群落的物种多样性和均匀度指数总体上呈上升趋势，其上升幅度均为 5．85％。总的看来，放牧状态下灌木群落的物种多样性和均匀度指数的相对变化趋势一致：轻牧态下灌木群落的物种多样性和均匀度指数均为下降趋势，重牧态下灌木群落的物种多样性和均匀度指数均为上升趋势。放牧状态下草本群落的物种多样性和均匀度指数均为下降趋势，说明只要存在外界干扰（放牧），就能使草本群落的物种多样性和均匀度指数下降，尤其是重牧处理能使草本群落的物种多样性指数大幅下降，平均下降幅度为 门．42％。试验结果表明，放牧尤其是重牧能使美丽胡枝子在灌木群落中的优势地位下降，这与其粗蛋白质含量较高、适口性较好有关，而较长时间的再生又能恢复或提高其在灌木群落中的优势地位。1999年的试验结果发现，放牧期间，宜昌木蓝在灌木群落中的重要值下降，说明放牧能影响其再生，导致宜昌木蓝在灌木群落中的优势性下降。2000年的试验结果说明：轻牧能刺激宜昌木蓝的再生，但由于其牧后的再生要比其它灌木植物缓慢，故宜昌木蓝的优势性下降。因此，应该严格控制其放牧强度，才不致于使宜昌木蓝从灌木群落中衰减甚至消失。（6）试验结果表明，不同放牧强度对山羊的日增重有明显的影响，轻牧区日增重高于重牧区。不同放牧时间对山羊的日增重影响极显著，5月份放牧山羊的平均日增重极显著高于（p＜0．of）7月和 9月放牧的山羊。5月、7月和 9月放牧山羊的平均日增重轻牧和重牧分别为 190和 120g、38．46和 15．389、22．2和 11．ig。灌木中可利用营养物质的含量对山羊的体重会产生明显的影响，当灌木中可利用的粗蛋白含量较高，而粗纤维含量较低时，有利于提高山羊的生产性能。在本试验中，禾草、杂类草、灌木以及灌丛草地植物群落的总体保护指标分别为 786．8、360．3、394．6和 1541．6DM kg／ha。如以生物量作为灌丛草地保护指标的衡量标准，优势灌木植物白烁、麻株、美丽胡枝子和盐肤木的更多还原

【Abstract】 A study was conducted on a naturely shrubland of Hejiaping on the county of Changyang inHubei Province from May to September in 1999 and from June to September in 2000.The studywith 9 local wethers was designed as three treatments including the control, the light- and heavy-grazing. The changes of community structure, yield, nutrition of shrubland and acceptability indexof shrubland plant under the different grazing intensities were systematically studied.The results were showed as follows: (1) The extremely significant (p<0.01)positivecorrelation between the fresh weight (Y) of new branches and leaves and up-ground and crownwidth (D) could be expressed by a function as Y=a D in the study. (2) The content of crudeprotein of Dacbergia hupeana Hance. was the highest, those of Jndigofrra ic/zangensis Craib andLespedezaformosaLes were in the second places, and their contents of crude protein in the drymatter were 17%, 16% and 15.7% respectively. The content of crude protein of Miscanthussinensis was the lowest (4.6%). (3) The dietary composition of shrub was higher under the light-grazing treatment than under the heavy-grazing treatment (1999 and 2000). The dietarycomposition of shrub (1999) under the light- and heavy-grazing treatments were 62% and 55%respectively in July, and were 78% and 51% respectively in September. The dietary compositionof shrub (2000) under the light- and heavy-grazing treatments were 6 1.2% and 44.4% respectivelyin June, and were 36.2% and 23.2% respectively in August. The acceptability index of shrubbyplants in 1999 was 33% and extremely significant (p<O.Ol) higher than that of herbage plants, andthose of grasses and forb were 9% and 4% respectively. There were no significant differences(p>O.O5) in the acceptability index of shrubs, grasses and forb in 2000 (21.3%, 13% and 11.6%respectively). (4) The yield composition and seasonal change on shrubland in the Three GorgesRegion of Yangtz river mainly depended on the seasonal growth and decline of grasses, and thechanging trends of production of grasses and total yield of shrubland were consistent. The yieldsof the control, the light- and heavy-grazing treatments in September were the highest and were3042.8, 2518.4 and 1180.3DM kg/ha respectively. A lot of rainfall could play a role in a certaindegree in the compensatory growth of plants that were consumed by animals. The net primarygrowth of plant on shrubland was lower under the light- and heavy-grazing treatment than underthe control treatment in August because of the severe lack of rainfall. The net growth of plant wasover-compensatory under the light-grazing treatment and low-compensatory under the heavy-grazing treatment. The average utilization efficiencies of grasses, forb and shrubs were 53.4%,40.4% and 9.1% respectively in June and were 47.4%, 73% and 39% respectively in August. (5)The species diversity and even index of shrubby community almost kept constant under thecontrol treatment and their average values were 2.0876 and 0.8715 respectively. The speciesdiversity and even index of shrubby community declined under the light-grazing treatment andincreased under the heavy-grazing treatment. The species diversity and even index of herbagecommunity declined under the light- and heavy-grazing treatments.The superiority of Lespedezaformosa/es in shrubby community declined under the grazing treatment especially the heavy-grazing treatment because of its relatively high content of crude protein and good preference, andsequential regrowth would improve its superiority in shrubby community. The regrowth ofIndigofera ic/langensis Craib was stimulated under the light-grazing treatment and was affectedunder the heavy-grazing treatment, so the stocking rate should be control lest Indigoferaichangensis Craib decline. (6) The daily gains of grazi更多还原