三江源高寒草地牧草营养时空分布

草地的产草量和牧草品质影响着草地载畜量和草食动物的营养状况、生命活动及生产性能。以三江源及其周边地区的天然草地不同生长期（返青期，盛草期，枯黄期）牧草为对象，分析草地产草量及牧草品质的时空格局。结果显示：从整个区域看，草地生产力、可食牧草产量以及粗蛋白产量(Crude Protein, CP)分布均具有较明显的地域差异性，三者的高值区大多分布在三江源东部及南部的高寒草甸区，三者的低值区主要在三江源中部和西部的草甸及高寒草原区；大部分地区总生产力和可食牧草产量盛草期显著高于枯黄期，枯黄期显著高于返青期。粗蛋白产量在大部分地区呈现出盛草期显著高于返青期和枯黄期，返青期和枯黄期差异不明显，少数地区返青期显著高于盛草期和枯黄期，盛草期显著高于枯黄期（如：可可西里）；CP含量及产量在三江源区空间上的分布，均为南部地区高于北部地区，东部农牧交错区高于西部无人区；所有区域CP含量的返青期为最高，枯黄期为最低，而其他养分含量在不同区域的季节波动并不一致；盛草期牧草CP含量随海拔升高先增加后减小，粗灰分随着海拔升高而显著增加，中性洗涤纤维、酸性洗涤纤维和酸性洗涤木质素含量随着海拔升高呈降低趋势。结论：三江源及周边地区牧草生产力、可食牧草产量以及CP产量较高，可食性较好；三江源多数地区高寒草地牧草营养质量相对较好，牧草在返青期营养价值最高（蛋白高，纤维低），到盛草期，牧草产量及营养物质输出量达到最高峰，进入枯黄期的牧草营养质量低劣，此时应进行补饲，以提高家畜生产性能。三江源区可利用草地主要集中在东部、南部和东南部，该区牧草品质较高、利用潜力（粗蛋白产量）较大，可适度利用开发。

Temporal and spatial distribution of herbage nutrition in alpine grassland of Sanjiangyuan

The standing herbage yield and quality affect the carrying capacity of grassland, the nutritional status and performance of herbivores. In this study, we chose the natural grasslands in Sanjiangyuan region and its surrounding areas, analyzed the temporal and spatial patterns of grassland primary productivity and herbage quality throughout one growing season (i.e. start, peak and end of the growing season). The results showed that aboveground herbage biomass, edible herbage and crude protein (CP) yields had apparent regional differences. Values of above three indexes were higher in the east and south parts than those in the middle and west parts of the Sanjiangyuan region. In most research areas, the gross primary productivity and edible herbage yields were the highest at the peak of growing season, and the lowest in the start of growing season. CP yield was the highest in the peak of growing season, and did not differ between the start and the end of growing season. While CP yield was the highest in the start of growing season, and was the lowest in the end of growing season in Kekexili district. In the whole Sanjiangyuan region, both CP content and CP yield were higher in the south part than those in the north part, and showed higher in the eastern agro-pastoral area than that in the western depopulated zone. Herbage CP content was the highest in the start of growing season, and the lowest in the end of growing season in all studied areas, while the seasonal fluctuations of other nutrient contents in different regions were not consistent. CP content of edible grass increased first and then decreased with the elevation increment. Crude ash content increased significantly, while neutral detergent fiber, acid detergent fiber and neutral detergent lignin decreased with elevation increment. In summary, standing herbage productivity, edible herbage yield and CP yield were higher in Sanjiangyuan region and its surrounding areas, and this kind of grass had better edibility. The herbage quality was relatively better in most areas of the Sanjiangyuan region, and the nutritional value of herbage was the highest (high protein, low fiber) in the end of growing season. The herbage yield and nutrient output peaked in the start of growing season. The nutrition quality of grass were poor during withering period, supplementary feeding should be carried out during this period to promote livestock performance. The available grassland was mainly distributed in the east, south and southeast parts of Sanjiangyuan region. The herbage quality and utilization potential (crude protein yield) are high in this region, where can be moderately utilized.