State Key Laboratory of Glassland and Agroecosystems, School of Life Sciences, Lanzhou University, Lanzhou, PR China.
PLoS One. 2013 Jul 24;8(7):e69364. doi: 10.1371/journal.pone.0069364. Print 2013.
Germination response to fluctuating temperatures is a mechanism by which seeds detect gaps in vegetation canopies and depth of burial in soil, and it is very important for plants. Thus, studies on the effect of fluctuating temperature on germination at the community level are valuable for understanding community structure and biodiversity maintenance. We determined the effects of two alternating temperatures (5/25°C and 10/20°C) and one constant temperature (15°C) on seed germination of 445 species in a grassland community on the eastern Tibet Plateau. Seed mass was determined for each species, and data on habitat, type of life cycle, altitudinal distribution and functional group (graminoids or forbs) were obtained from the literature. Taking all species into account, alternating temperatures increased germination percentages regardless of amplitude. Overall, species growing in disturbed ground showed a significant germination response to temperature fluctuation, but those living in Alpine/subalpine meadow, forest margin /scrub, marshland and dry sunny slope habitats did not. Species distributed only at high elevations (>2000m) did not show a significant germination response to temperature fluctuation, whereas those occurring at both high and low elevations had a significant positive response. Germination of annuals/biennials was significantly promoted by 5/25°C, but not by 10/20°C, whereas germination of perennials was significantly promoted by both 5/25°C and 10/20°C. Small-seeded species were more likely than large-seeded species to respond positively to fluctuating temperatures. Germination of forbs had a positive response to temperature fluctuation, but germination of graminoids did not. Regeneration ability by seeds for about 36% of the species studied in the grassland can be increased by temperature fluctuation. The differential response among species to alternating vs. constant temperatures helps maintain community structure and biodiversity. A positive germination response to temperature fluctuation can partly explain why there are more forbs in degraded meadows.
温度波动对萌发的响应是种子检测植被空隙和土壤埋藏深度的一种机制，对植物非常重要。因此，研究群落水平上温度波动对萌发的影响对于理解群落结构和生物多样性的维持具有重要意义。我们确定了两种交替温度（5/25°C 和 10/20°C）和一种恒定温度（15°C）对青藏高原东部草原群落中 445 种种子萌发的影响。为每个物种确定了种子质量，并从文献中获得了有关生境、生活史类型、海拔分布和功能群（禾本科或草本植物）的数据。考虑到所有物种，交替温度增加了萌发百分比，而不管幅度如何。总的来说，生长在受干扰地面上的物种对温度波动表现出显著的萌发响应，但生长在高山/亚高山草地、林缘/灌丛、沼泽地和干燥向阳坡生境中的物种则没有。仅分布在高海拔（>2000m）的物种对温度波动没有表现出显著的萌发响应，而分布在高海拔和低海拔的物种则表现出显著的正响应。一年生/二年生植物的萌发明显受到 5/25°C 的促进，但不受 10/20°C 的影响，而多年生植物的萌发则明显受到 5/25°C 和 10/20°C 的促进。小种子物种比大种子物种更有可能对波动温度做出积极响应。草本植物的萌发对温度波动有积极响应，但禾本科植物的萌发则没有。受研究草原中约 36%物种的种子再生能力可以通过温度波动得到提高。物种对交替温度和恒定温度的不同响应有助于维持群落结构和生物多样性。对温度波动的萌发有积极响应可以部分解释为什么退化草地中有更多的草本植物。
