This study aimed to investigate the forage yield and quality and extract factors affecting them and provide scientific support for ecological protection of alpine grassland and sustainable development of animal husbandry in the Qinghai-Tibetan Plateau. Samples were collected in late August (peak of the growing season) 2014 in two mountain transects (Laji mountain, 36° 21′ N, 101° 27′ E, 3389–3876 m a.s.l. and Heitu mountain, 34° 22′ N, 100° 30′ E, 4121–4268 m a.s.l.) of Sanjiangyuan. Forage biomass and nutrients were measured by the national standard method, and influencing factors were extracted by RDA. Results showed that the forage yield decreased significantly with the increasing altitude, no matter in the mountain > 4000 m a.s.l. or 4000 m a.s.l., fiber and lignin were mainly affected by soil pH and SOC and crude protein (CP) by soil pH (p < 0.05) and total phosphorus (TP). Overall, with the increasing altitude, forage CP and fat (CF) increased, while neutral detergent fiber and acid detergent fiber decreased, implying that warming may lead to the decline of forage quality and then affect the safety of animal husbandry. Moreover, forage CP and CF were also affected by soil inorganic nitrogen and TP rather than SOC and soil total nitrogen.

中文翻译：

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三江源高寒草甸牧草产量和养分随海拔梯度变化及其影响因素

本研究旨在调查青藏高原牧草产量、品质及影响因素提取，为青藏高原高寒草地生态保护和畜牧业可持续发展提供科学依据。样品于 2014 年 8 月下旬（生长季节的高峰期）在两个山地横断面（拉济山，北纬 36°21′，东经 101°27′，3389-3876 m 和黑土山，北纬 34°22′，100 ° 30′ E, 4121–4268 m asl) 三江源。牧草生物量和养分采用国标法测定，影响因素采用RDA提取。结果表明，牧草产量随着海拔的升高而显着下降，无论是在＞4000 m asl还是4000 m asl的山区，纤维和木质素主要受土壤 pH 值和 SOC 的影响，粗蛋白（CP）受土壤 pH 值（p < 0.05）和总磷（TP）的影响。总体而言，随着海拔的升高，牧草CP和脂肪（CF）增加，而中性洗涤纤维和酸性洗涤纤维减少，表明气候变暖可能导致牧草质量下降，进而影响畜牧业安全。此外，牧草CP和CF也受土壤无机氮和TP的影响，而不是SOC和土壤全氮。