Ecological field experiments initiate successional and evolutionary changes amongst resident species, yet effect sizes are often reported as if they were constants. Few ecological studies have addressed their questions through long-term, experimental approaches, and many questions remain unanswered regarding temporal patterns in ecological effect sizes. We document temporal variation in effect sizes in response to pulse and press manipulations in a long-term factorial field experiment at Nash's Field, England. The experiment comprises seven treatments applied in a split-plot design to test the single and interactive effects of herbivory by insects, molluscs and rabbits, liming, nutrient limitation (applied as press experiments), competition (exclusion of grasses or herbs with specific herbicides), and seed limitation (pulse experiments) on plant community dynamics. The response of all vascular plant species was followed for two decades. High species richness was positively related to the minus-grass herbicide in the first decade and negatively related to both nitrogen addition and the abundance of dominant species in both decades. Many significant effects appeared quickly, but some large effects were not detected until year 15. Press experiments produced some long-lasting effects, but effect sizes changed due to both idiosyncratic 'year effects' and secular trends. For pulse experiments, most effects -including positive and negative responses to herbicide application and the invasion of most of the sown species- disappeared quickly. However, some endured or grew monotonically, such as the invasion of two sown species that benefited from particular combinations of the press treatments. The fastest effects to appear were the responses from established species. Many of these responses were negative, likely resulting from reduced niche dimensionality and competitive exclusion by new dominant species. Contrarily, one of the largest community-level effects took well over a decade to appear: the natural invasion by one species, which responded to a four-way interaction between experimental treatments. The insights gained from individual effects increased with the duration of the lag before their first appearance, drawing attention to the importance of long-term, manipulative field experiments. This experiment also reinforces the point that factorial experiments are the most insightful way to explore ecological interactions.

中文翻译：

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长期裂区田间试验中效应大小的时间变化

生态田间试验启动了常驻物种之间的演替和进化变化，但通常报告的效应大小就好像它们是常数一样。很少有生态研究通过长期的实验方法解决了他们的问题，而且许多关于生态效应大小的时间模式的问题仍未得到解答。我们在英格兰 Nash's Field 的长期因子现场实验中记录了响应于脉冲和压力操作的效应大小的时间变化。该实验包括在裂区设计中应用的七种处理方法，以测试昆虫、软体动物和兔子、石灰、营养限制（用作压榨实验）、竞争（排除具有特定除草剂的草或草本植物）的单一和交互作用, 和种子限制（脉冲实验）对植物群落动态的影响。所有维管植物物种的反应被跟踪了二十年。高物种丰富度与第一个十年的负草除草剂呈正相关，与两个十年的氮添加和优势物种的丰度均呈负相关。许多显着的影响很快就出现了，但一些大的影响直到 15 年才被发现。新闻实验产生了一些长期的影响，但由于特殊的“年份效应”和长期趋势，影响大小发生了变化。对于脉冲实验，大多数影响 - 包括对除草剂施用的积极和消极反应以及大多数播种物种的入侵 - 很快消失。然而，有些忍受或单调地增长，例如受益于压榨处理的特定组合的两种播种物种的入侵。出现最快的影响是来自已建立物种的反应。其中许多反应都是负面的，可能是由于生态位维度减少和新优势物种的竞争排斥所致。相反，最大的社区影响之一在十多年后才出现：一个物种的自然入侵，它对实验处理之间的四向相互作用做出反应。从个体效应中获得的见解随着它们第一次出现之前的滞后时间而增加，引起人们对长期、操纵性现场实验的重要性的关注。该实验还强调了析因实验是探索生态相互作用的最有洞察力的方式的观点。