短期围封对辽西北退化草地群落牧草品质的影响

围封对退化草地牧草品质的影响是评价围封效果的重要方面。以辽西北退化草地为研究对象，研究3年间（2017-2019年）围封和自由放牧处理下群落特征和牧草品质各项指标的变化。结果表明：围封区群落高度、盖度、地上生物量、枯落物量以及牧草粗蛋白、非纤维性碳水化合物、产奶净能、奶吨指数显著高于放牧区（P<0.05），具有较高的营养成分以及饲喂价值，而放牧区牧草粗灰分、粗脂肪、木质素、酸性洗涤纤维、体外干物质消化率、中性洗涤纤维消化率、可消化中性洗涤纤维、钙、镁以及磷元素含量极显著高于围封区（P<0.01），具有较高的消化率和更为丰富的矿质元素，但适口性较差。2019年牧草粗蛋白、非纤维性碳水化合物、钾元素、维持净能以及总可消化养分含量相比围封初年（2017年）均得到显著提高（P<0.05），且中性洗涤纤维含量最低（P<0.05）。结果表明退化草地经短期围封后群落特征指标和牧草品质均得以提高，这为退化草地短期围封提供理论参考，对草原管理和利用具有重要意义。

Effect of short-term fencing on the forage quality of plant communities in degraded grassland in Northwestern Liaoning

The impact of fencing on the forage quality of degraded grassland is an important aspect of evaluation of fencing effectiveness. This research studied the changes in community characteristics and forage quality indicators from 2017 to 2019 under fencing and free grazing treatments in degraded grassland in northwestern Liaoning Province. It was found that plant community height， vegetation cover， aboveground biomass， plant litter and the levels of crude protein （CP）， non-fibrous carbohydrate （NFC）， net energy for lactation， milk perton index （MT） in the fencing treatment were significantly higher than corresponding values for the grazing treatment （P<0.05）， thus it was deduced the forage in the fencing treatment had higher nutrient content and feeding value. The forage crude ash， ether extract， lignin， acid detergent fiber， in vitro dry matter digestibility， neutral detergent fiber digestibility， digestible neutral detergent fiber， and elemental calcium， magnesium and phosphorus contents in the grazing treatment were all significantly higher than those in the fencing treatment （P<0.01）， so the forage in the grazing treatment had high digestibility and was rich in mineral elements， but had poor palatability. In 2019， the levels of CP， NFC， elemental potassium， net energy for maintenance and total digestible nutrients in forage were significantly higher than those in the first year of fencing （2017） （P<0.05）， and the neutral detergent fiber concentration was the lowest among the three years （P<0.05）. Hence， the results show that the indexes describing community characteristics and forage quality of degraded grassland were improved after three years fencing. These results provide theoretical reference data for short-term fencing of degraded grassland and show the importance of fencing for grassland management and utilization.