Zhang Chunhui, Ma Zhen, Zhou Huakun, Zhao Xinquan
State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, Qinghai, China.
Key Laboratory of Restoration Ecology for Cold Regions in Qinghai Province, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, China.
PeerJ. 2019 Jul 31;7:e7416. doi: 10.7717/peerj.7416. eCollection 2019.
Global warming can cause variation in plant functional traits due to phenotypic plasticity or rapid microevolutionary change. Seed mass represents a fundamental axis of trait variation in plants, from an individual to a community scale. Here, we hypothesize that long-term warming can shift the mean seed mass of species.
We tested our hypothesis in plots that had been warmed over 18 years in alpine meadow communities with a history of light grazing (LG) and heavy grazing (HG) on the Qinghai-Tibet plateau. In this study, seeds were collected during the growing season of 2015.
We found that warming increased the mean seed mass of 4 ( = 19) species in the LG meadow and 6 ( = 20) species in the HG meadow, while decreasing the mean seed mass of 6 species in the LG and HG meadows, respectively. For 7 species, grazing history modified the effect of warming on seed mass. Therefore, we concluded that long-term warming can shift the mean seed mass at the species level. However, the direction of this variation is species-specific. Our study suggests that mean seed mass of alpine plant species appears to decrease in warmer (less stressful) habitats based on life-history theory, but it also suggests there may be an underlying trade-off in which mean seed mass may increase due to greater thermal energy inputs into seed development. Furthermore, the physical and biotic environment modulating this trade-off result in complex patterns of variation in mean seed mass of alpine plant species facing global warming.
全球变暖可通过表型可塑性或快速的微进化变化导致植物功能性状发生变异。种子质量代表了从个体到群落尺度植物性状变异的一个基本轴。在此，我们假设长期变暖会改变物种的平均种子质量。
我们在青藏高原上具有轻度放牧（LG）和重度放牧（HG）历史的高山草甸群落中，对已进行了18年变暖处理的样地进行了假设检验。在本研究中，于2015年生长季收集种子。
我们发现，变暖使LG草甸中的4种（共调查19种）物种以及HG草甸中的6种（共调查20种）物种的平均种子质量增加，同时分别使LG和HG草甸中6种物种的平均种子质量降低。对于7种物种，放牧历史改变了变暖对种子质量的影响。因此，我们得出结论，长期变暖可在物种水平上改变平均种子质量。然而，这种变异的方向因物种而异。我们的研究表明，根据生活史理论，高山植物物种的平均种子质量在温暖（压力较小）的栖息地似乎会降低，但这也表明可能存在一种潜在的权衡，即由于种子发育过程中获得更多热能输入，平均种子质量可能会增加。此外，调节这种权衡的物理和生物环境导致了高山植物物种在面对全球变暖时平均种子质量的复杂变异模式。
