Jessen Maria-Theresa, Roeder Anna, Roscher Christiane
Department of Physiological Diversity, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, D-04318 Leipzig, Germany.
German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig (iDiv), Puschstraße 4, D-04103 Leipzig, Germany.
Ann Bot. 2025 Jul 18. doi: 10.1093/aob/mcaf158.
Current grassland management including fertilization, mowing and livestock grazing, substantially influences plant communities, however it is not fully understood how management can affect plant growth at the individual level. Most herbaceous dicotyledonous plant species form distinct annual rings in the xylem that reveal age but their annual width may also respond to changes in environmental conditions. Further is unclear at what scale, from the local plot level to the regional level, such secondary growth varies most.
Using cross sections of the oldest well-preserved detectable part of the rhizome of Galium mollugo agg., we determined the response of secondary growth to the intensity, timing, and type of grassland management for 1220 individuals across 60 populations in three different regions in Germany. In addition, we used environmental variables to examine the effects of climatic, soil, and diversity-related characteristics on ring width variation.
The age of the studied G. mollugo individuals ranged between one and 17 years (average age six years). Secondary growth varied most among individuals within sites and only slightly among sites within regions and among regions, indicating a strong influence of local plant-plant interactions. Increasing overall management and land-use intensity decreased secondary growth while a late start of annual land use increased it. In addition, summer soil moisture was positively related while neighbour species richness was negatively related to secondary growth.
Our results indicate that annual secondary growth of a widespread herbaceous grassland species is sensitive to timing and intensity of land use and season water regimes. The results imply that trends of increasing land-use intensity along with prolonged summer heat waves will further hamper growth of G. mollugo which may translate to reduced performance and subsequently affect the overall plant community.
当前的草地管理措施，包括施肥、割草和放牧，对植物群落有重大影响，但管理措施如何在个体层面影响植物生长尚不完全清楚。大多数草本双子叶植物物种在木质部形成明显的年轮，可揭示其年龄，但其年轮宽度也可能对环境条件的变化作出反应。此外，尚不清楚从局部地块水平到区域水平，这种次生生长在何种尺度上变化最大。
我们利用猪殃殃复合体保存最完好、可检测到的最老根茎部分的横截面，确定了德国三个不同地区60个种群中1220个个体的次生生长对草地管理强度、时间和类型的反应。此外，我们使用环境变量来研究气候、土壤和与多样性相关的特征对年轮宽度变化的影响。
所研究的猪殃殃个体年龄在1至17岁之间（平均年龄6岁）。次生生长在各地点内的个体间变化最大，而在区域内各地点间以及区域间变化较小，这表明当地植物间相互作用的强烈影响。总体管理和土地利用强度的增加会降低次生生长，而年度土地利用的较晚开始则会增加次生生长。此外，夏季土壤湿度与次生生长呈正相关，而邻体物种丰富度与次生生长呈负相关。
我们的结果表明，一种广泛分布的草本草地物种的年度次生生长对土地利用的时间和强度以及季节水分状况敏感。结果表明，土地利用强度增加以及夏季热浪持续时间延长的趋势将进一步阻碍猪殃殃的生长，这可能导致其表现下降，并随后影响整个植物群落。
