Abstract Aims Soil biotic communities can strongly impact plant performance. So far, most studies on plant-soil-interactions have estimated the effect of the soil microbial community on plant mass after a fixed duration of plant growth. However, these interactions may change over time and several studies have argued that plant-soil interactions are more important for young seedlings than for older plants. In this paper we ask the question: how long-lasting the effect of the soil microbial community on plant growth is. This is important as the growth rate of a plant is not only determined by the growing conditions but also by the size of the plant itself. Therefore, plant with a reduced growth rate early in life, due to negative effects of the soil microbial community, may increase less in biomass for a much longer period even though the relative growth rates do not differ any longer. Methods We examined the plant growth rates at three stages: early growth (0-21 days), mid growth (22 to 42 days) and late growth (43 to 63 days). We performed two growth experiments with Jacobaea vulgaris lasting 49 and 63 days. Plants were grown in sterilized soil or in sterilized soil inoculated with natural dune soil. In a third experiment, we examined the effect of the timing of soil inoculation prior to planting on the (relative-) growth rate of J. vulgaris plants with four different timing treatments. Important findings In all experiments, differences in biomass of plants grown in sterilized soil and inoculated soil (live soil) increased throughout the experiment. Interestingly, linear regression models with ln transformed dry weight against time for younger plants and for older plants in sterilized soil and live soil, respectively, showed that the relative growth rate of plants in the sterilized soil was only significantly higher than that of plants in the live soil in the first two to three weeks. After that period there was no longer a negative effect of the live soil on the relative growth rate of plants. In the third experiment, plant biomass decreased with increasing time between inoculation and planting. Overall, our results show that plants of J. vulgaris grew less well in live soil than in sterilized soil. The negative effects of soil inoculation on plant mass appeared to extend over the whole growth period but arise from the negative effects on relative growth rates that occurred in the first weeks after planting when plants have only less than 5% of the mass they obtained after 42 days. Our study highlights the importance of examining relative growth rates rather than final biomass to estimate the effects of soil microbial communities on plants.

中文翻译：

---

土壤微生物对植物生长的负面影响只延续到最初几周

摘要 目的 土壤生物群落可以强烈影响植物性能。到目前为止，大多数关于植物-土壤相互作用的研究都估计了植物生长一段时间后土壤微生物群落对植物质量的影响。然而，这些相互作用可能会随着时间而改变，一些研究认为植物与土壤的相互作用对幼苗比对老植物更重要。在本文中，我们提出一个问题：土壤微生物群落对植物生长的影响持续多久。这很重要，因为植物的生长速度不仅取决于生长条件，还取决于植物本身的大小。因此，由于土壤微生物群落的负面影响，生命早期生长速度降低的植物，即使相对增长率不再不同，生物量的增加可能会在更长的时间内减少。方法 我们检测了三个阶段的植物生长速率：早期生长（0-21 天）、中期生长（22 到 42 天）和晚期生长（43 到 63 天）。我们用 Jacobaea vulgaris 进行了两次生长实验，持续 49 天和 63 天。植物在无菌土壤或接种有天然沙丘土壤的无菌土壤中生长。在第三个实验中，我们用四种不同的时间处理检查了种植前土壤接种时间对 J. vulgaris 植物（相对）生长速率的影响。重要发现 在所有实验中，在整个实验过程中，在无菌土壤和接种土壤（活土壤）中生长的植物生物量的差异增加了。有趣的是，在灭菌土壤和活土壤中，用 ln 转换干重与时间的线性回归模型分别显示，灭菌土壤中植物的相对生长速率仅显着高于未灭菌土壤中植物的相对生长速率。前两到三周的活土。在那之后，活土不再对植物的相对生长速度产生负面影响。在第三个实验中，植物生物量随着接种和种植之间时间的增加而减少。总体而言，我们的结果表明，J. vulgaris 植物在活土壤中的生长不如在无菌土壤中好。土壤接种对植物质量的负面影响似乎延伸到整个生长期，但源于对相对生长速率的负面影响，这种负面影响发生在种植后的第一周，当时植物的质量只有不到 42 岁后获得的质量的 5%。天。我们的研究强调了检查相对生长速率而不是最终生物量来估计土壤微生物群落对植物的影响的重要性。