不同人工草地对青藏高原温性草原群落生物量组成及物种多样性的影响

青藏高原天然草地生产力较低,草畜矛盾长期尖锐。人工草地逐渐在该区域发展,但不同种植模式人工草地的影响和应用适宜性尚未得到准确的量化评估。以青海省天然草地(NP)为对照,选取相互毗邻的3种不同人工草地:单播垂穗披碱草人工草地(A₁)、单播燕麦人工草地(A₂)和混播燕麦、青稞和油菜的人工草地(A₃)设置实验样地,通过群落调查、刈割称重、根钻采样等方法,测定分析4种群落物种组成、生物量及物种多样性,探讨燕麦和垂穗披碱草两种牧草及单播和混播两种种植方式的差异性影响。结果表明:3种不同人工草地均显著减少有毒植物生物量(P<0.05),显著提高优质牧草占比(P<0.05),改善牧草质量。A₂地上生物量最高(1263.21 g·m^-2),为NP的9.77倍,显著高于其他3种草地(P<0.05)。本研究草地地下生物量占比高(73.22%~95.79%),3种人工种草对地下生物量改变不显著,对总生物量的影响也不显著。A₂、A₃的物种组成与NP迥异,A₂的Pielou均匀度指数显著低于NP和A₃(P<0.05),A₃的Shannon-Wiener指数显著低于NP(P<0.05);而A₁的Gleason指数、Shannon-Wiener指数和Pielou均匀度指数均较高,与NP差异不显著。基于结果,认为相比于天然草地,单播燕麦人工草地可以获得更高的地上生物量,但强烈改变群落物种组成,降低群落物种多样性;而种植垂穗披碱草地上生物量增幅不显著,但其群落物种多样性、均匀度均较高,有利于群落在不利条件下维持相对稳定的生产力。

The impact of different introduced artificial grassland species combinations on community biomass and species diversity in temperate steppe of the Qinghai-Tibetan Plateau

The temperate steppe ecosystem on the Qinghai-Tibet Plateau has degenerated greatly in recent decades. Cultivating artificial grassland can alleviate the degradation of natural grassland and result in higher biomass yield. However, the influence and suitability of different species combinations when used to establish artificial grassland in this region remain unclear. Therefore, we selected one natural pasture (NP) as a comparison and three different adjacent artificial seeding regimes Elymus nutans monoculture (A₁), oat monoculture (A₂) and oat-highland barley-oilseed rape mixed-culture (A₃)] to establish artificial grasslands for experimental comparison in temperate steppe of Guinan county, Qinghai Province. The research aim was to evaluate the influence that different forages (oat and E. nutans; A₁ and A₂) and sowing methods (monoculture or mixed-culture; A₂ and A₃) would have on herbage yield and vegetation community stability. Results were obtained by community investigation and sampling in each plot. In this study, the three artificial grasslands under agricultural management significantly decreased the biomass of poisonous plants (P<0.05), and also significantly improved the proportion of high-quality forage (P<0.05). A₂ provided the highest aboveground biomass (1263.21 g·m^-2) and was 9.77 times more productive than NP and significantly higher than the other three grasslands (P<0.05). The three artificial grasslands did not significantly change the belowground biomass or the total biomass, and no significant difference of these two indices was found among artificial grasslands. Artificial grasslands in this study changed the species composition, especially A₂ and A₃, which were quite different from NP. The Pielou evenness index of A₂ was significantly lower than NP and A₃ (P<0.05), while the Shannon-Wiener index of A₃ was significantly lower than NP (P<0.05). In contrast, A₁ had a high species diversity index, by various measures, including Gleason index, Shannon-Wiener index and Pielou evenness index, was similar to NP. Our results demonstrate that the oat monoculture grassland (A₂) changed the species composition of the NP temperate steppe vegetation community more strongly than other treatments and produced higher aboveground biomass in comparison to E. nutans grassland. By contrast, E. nutans grassland did not greatly improve aboveground biomass, but maintained community species diversity and evenness, which was conducive to retention of a relatively stable community productivity under harsh conditions.