Kang Xiaomei, Wu Xinyang, Liu Yanjun, Zhang Aoran, Duan Lijie, Zhou Jieyang, Zhan Zhixi, Qi Wei
State Key Laboratory of Herbage Improvement and Grassland Agro-Ecosystems, College of Ecology, Lanzhou University, Lanzhou, 730000, China.
Gansu Provincial Extension Station of Grassland Techniques, Lanzhou, 730000, China.
Oecologia. 2025 May 2;207(5):77. doi: 10.1007/s00442-025-05716-1.
An accurate assessment of shrub-herb interactions is challenging because shrubs can facilitate herb growth as nurse plants and negatively affect herbs as competitors. As responses to the effects of neighbors are often trait dependent, the impact of shrubs on grassland communities may differ with a variation in herb functional traits. In 2020, we surveyed the structure and functional pattern of 160 Qinghai-Tibet alpine grassland communities under the canopy of four dominant shrub species and their surrounding open areas. We found an overall negative effect of shrubs on grassland productivity, species diversity, and individual abundance, suggesting that interspecific resource competition, rather than facilitation, dominated the effect of shrubs on herb growth. The negative effect was weakest for small deciduous shrub species, implying that seasonal defoliation and low shading conditions could reduce the light competition of shrubs on herbs. Shrubs generally increased grassland functional diversity of vegetative traits, especially leaf economic traits, but decreased that of reproductive traits, especially seed traits, demonstrating that shrubs affected grassland community assembly by offering benign microhabitats to protect herbaceous species with stress-intolerant or fast-acquisition vegetative traits and setting physical barriers to prevent the entry of species with specific reproductive traits. Moreover, as canopy transmittance increased, positive shrub effects on leaf size diversity became more pronounced. However, an increase in canopy size intensified the negative effects of shrubs on the diversity of plant height and some reproductive traits. Results illustrated that the structuring of alpine grassland communities by shrubs depends on their type (semi-evergreen or deciduous) and size.
准确评估灌木与草本植物之间的相互作用具有挑战性，因为灌木既可以作为护株促进草本植物生长，也可以作为竞争者对草本植物产生负面影响。由于对邻体效应的响应通常取决于植物性状，灌木对草地群落的影响可能会因草本植物功能性状的变化而有所不同。2020年，我们调查了160个青藏高原高寒草地群落的结构和功能模式，这些群落位于四种优势灌木物种的冠层下及其周围的开阔区域。我们发现，灌木对草地生产力、物种多样性和个体丰度总体上具有负面影响，这表明种间资源竞争而非促进作用主导了灌木对草本植物生长的影响。小型落叶灌木物种的负面影响最弱，这意味着季节性落叶和低遮荫条件可以减少灌木对草本植物的光照竞争。灌木通常会增加草地营养性状的功能多样性，尤其是叶片经济性状，但会降低繁殖性状的功能多样性，尤其是种子性状，这表明灌木通过提供良性微生境来保护具有不耐胁迫或快速获取营养性状的草本物种，并设置物理障碍来阻止具有特定繁殖性状的物种进入，从而影响草地群落的组装。此外，随着冠层透光率的增加，灌木对叶片大小多样性的积极影响变得更加明显。然而，冠层大小的增加加剧了灌木对株高多样性和一些繁殖性状的负面影响。结果表明，灌木对高寒草地群落的构建作用取决于其类型（半常绿或落叶）和大小。
