The impact of seed deficiency on productivity and on negative drought effect in semi-natural grassland,Journal of Vegetation Science

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The impact of seed deficiency on productivity and on negative drought effect in semi-natural grassland
Journal of Vegetation Science ( IF 2.2 ) Pub Date : 2020-06-08 , DOI: 10.1111/jvs.12889
Andreas Stampfli _{1,

2,

3} , Michaela Zeiter _{1,

2,

3}

Affiliation

Questions Vegetative re‐sprouting and recruitment from seed determine grassland recovery after severe drought, but the mechanisms determining vegetation composition are not fully understood. We ask how the timing of drought and seed availability modify the drought legacy effects on composition and function in a temperate, semi‐natural grassland. Location Negrentino, southern Alps, Switzerland. Methods Under automated rainout shelters, we simulated extreme seasonal drought events in a late summer and in the following spring, added rainwater to simulate normal conditions in no‐drought controls and maintained haymaking at times of normal practice. Towards the end of the summer drought, we added seeds of ten local species in a three‐factor split‐plot arrangement with seven blocks as the replicated unit. We measured fine‐scale variation in soil depth. We assessed the biomass of graminoids and forbs at regular harvesting dates and the species frequencies of established plants and recruits before treatment start, repeating these assessments for three years thereafter. We measured the biomass proportions of post‐drought annual recruit cohorts in year 4 after drought. Results One‐time seed addition augmented recruits, modified species composition and enhanced species diversity; these effects propagated to increased reproductive shoots of recruits and community biomass four years later. Single and repeated seasonal droughts only caused low adult plant mortality but clearly reduced recruitment from seed, while post‐drought establishment was slightly enhanced. Seed augmentation compensated the negative spring drought effect on forb recruits and in turn mitigated the negative impact of drought on species diversity after drought. Conclusions Our experiment shows that seed deficiency limits productivity and that seed deficiency compensation can help to stabilize diversity and productivity in semi‐natural grassland. Releasing the current constraints of management on seed supply in grassland would therefore assist in mitigating negative drought impacts.

中文翻译：

种子缺乏对半天然草地生产力和干旱负效应的影响

问题严重干旱后，植物重新发芽和补充种子决定了草地的恢复，但决定植被组成的机制尚不完全清楚。我们询问干旱的时间和种子可用性如何改变干旱对温带半天然草原的组成和功能的影响。地点内格伦蒂诺，瑞士南部阿尔卑斯山。方法在自动雨棚下，我们模拟了夏末和次年春季的极端季节性干旱事件，添加雨水以模拟无旱控制中的正常条件，并在正常实践时保持干草制作。在夏季干旱即将结束时，我们以 7 个区块为复制单位，以三因子裂地排列添加了 10 个当地物种的种子。我们测量了土壤深度的精细尺度变化。我们在常规收获日期评估了禾本科和杂草的生物量以及处理开始前已建立植物和新兵的物种频率，此后三年重复这些评估。我们测量了干旱后第 4 年干旱后年度招募队列的生物量比例。结果一次性种子添加增加了新兵，改变了物种组成并增强了物种多样性；四年后，这些影响传播到新兵和社区生物量的繁殖枝条增加。单次和重复的季节性干旱仅导致成株死亡率较低，但明显减少了种子的补充，而干旱后的建立略有增强。种子增加补偿了春季干旱对新兵的负面影响，反过来减轻了干旱对干旱后物种多样性的负面影响。结论我们的实验表明，种子缺乏限制了生产力，种子缺乏补偿有助于稳定半天然草地的多样性和生产力。因此，解除目前草原种子供应管理的限制将有助于减轻干旱的负面影响。

更新日期：2020-06-08

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