Alternatively, field experiments allow for the manipulative control of a limited number of factors under realistic natural conditions. However, most environmental conditions are unaccounted for, making replication difficult, which often results in contradictory evidence. Hence, results may be unquestionably realistic but also unlikely to be consistently replicable, with results being contingent both on location and on time due to factors such as unaccounted variation in soil biota or differences in precipitation among years or between sites.

Plant physiology and ecology often delve into the study of trade-offs. For a scientist designing an experiment, the choice of field vs common garden poses a fundamental choice with its own intrinsic trade-offs. Many individual studies have illustrated the limitations of pot vs field experiments, but a recent study by Zhu et al. (2024; https://doi.org/10.1111/nph.20160), published in New Phytologist, showcases these trade-offs at a particularly large scale (64 different species) and interesting context (exotic vs native species). The authors grew plants of each of the 64 species individually in pots and compared the traits of the different native and exotic species with mixes of the same species planted in the field.

Zhu et al. found interesting results that generally confirmed expectations, but in the field study only, not the one in pots. The study was not without limitations: the comparison of plants grown in pots individually with plants grown in field mixes presented some caveats. It remains unclear whether any difference between native and exotic species - or the absence of a difference - could be due to the absence of competition in the pot experiment or to differences in other factors.

We know that exotic species tend to outperform natives in most scenarios (van Kleunen et al., 2010), but those advantages are sometimes evident only under certain conditions, typically under disturbance (Jauni et al., 2015; Xiao et al., 2016; Montesinos, 2022), when resources are abundant or increasing (Davis et al., 2000; Zhang et al., 2022; Arias et al., 2023) or, alternatively, only when resources are low, or plants experience stress (Funk & Vitousek, 2007; Santamarina et al., 2022). It is possible that the differences observed by Zhu et al. between both experiments were due to the more competitive conditions experienced by plants under field conditions. We cannot discard that a pot experiment involving a mix of species similar to that in the field experiment would not have resulted in similar results. However, at least some previous studies with similar experimental designs found that competition was a factor in reducing - not increasing - trait differences between natives and exotics (Blumenthaal & Hufbauer, 2007). This suggests that the problem might not be the absence of competition in Zhu et al.'s pot experiment, but rather the intrinsic limitations associated with pot experiments.

Perhaps the most insightful finding by Zhu et al. was that only field mixtures allowed for the identification of traits that were predictive of future species abundance and persistence (specific leaf area (SLA), plant height, aboveground biomass). Field mixtures also showed that exotics were overall more persistent than natives, and perennials more than annuals. These results agree with common expectations for native–exotic species interactions, and some previous studies have shown how field studies can detect native and exotic differences that pot experiments are not able to discern (Leffler et al., 2014). Still, previous studies are limited to one or a few species for such comparisons, and meta-analysis such as those by Leffler et al. (2014) provide an integrative view that cannot, however, provide direct evidence in the way that a single study comparing 64 species simultaneously can.

It is therefore comforting to see large scale experiments verifying our theoretical assumptions and yet it is concerning to recognize that pot experiments might be missing so much. Two rapid conclusions can be drawn: first, pot experiments are safe in that they are unlikely to unrealistically magnify or overrepresent existing differences, that is, they are unlikely to result in a type I statistical error (false positive); second, pot experiments might mislead us into ignoring factors and traits that would be highly informative if studied in the field. That is, they are highly likely to result in type II statistical errors (false negative).

This is a sobering insight, and the confirmation of it both by meta-analysis based on numerous, but small, studies (Leffler et al., 2014), and also by large scale experiments such as the one by Zhu et al., should make us reconsider the trade-offs involved. There will always be a need to run experiments in highly controlled pot experiments, but those experiments should focus on specific traits or treatments that have been broadly identified in the field beforehand. Exploring a broad range of traits in pot experiments to determine which ones will be meaningful predictors might appear as an efficient and attractive option, but it could end up being efficient in appearance only. It is likely that such an approach would erroneously lead us to ignore important predictive traits or factors that should have been identified previously via field studies.

或者，田间实验允许在现实自然条件下对有限数量的因子进行操纵控制。然而，大多数环境条件都未得到解释，这使得复制变得困难，这往往会导致相互矛盾的证据。因此，结果无疑是现实的，但也不太可能始终如一地复制，由于土壤生物群落的未解释变化或年份之间或地点之间降水的差异等因素，结果取决于地点和时间。

植物生理学和生态学经常深入研究权衡取舍。对于设计实验的科学家来说，选择田间花园还是普通花园是一个基本的选择，有其自身的内在权衡。许多单独的研究已经说明了罐子与田间实验的局限性，但 Zhu 等 人最近的一项研究。（2024 年;https://doi.org/10.1111/nph.20160 年）发表在《新植物学家》上，在特别大的规模（64 个不同的物种）和有趣的背景（外来物种与本地物种）下展示了这些权衡。作者在花盆中分别种植了 64 种植物，并将不同本地和外来物种的特性与田间种植的相同物种的混合物进行了比较。

Zhu 等 人。发现了有趣的结果，这些结果通常证实了预期，但仅在实地研究中，而不是 POTS 中的结果。这项研究并非没有局限性：将单独种植在花盆中的植物与在田间混合种植的植物进行比较提出了一些注意事项。目前尚不清楚本地物种和外来物种之间的任何差异 - 或没有差异 - 可能是由于盆栽实验中没有竞争还是由于其他因素的差异。

我们知道，在大多数情况下，外来物种往往优于本地物种（van Kleunen et al.， 2010），但这些优势有时仅在特定条件下才显现出来，通常是在干扰下（Jauni et al.， 2015;Xiao et al.， 2016;Montesinos，2022 年），当资源丰富或增加时（Davis 等 人，2000 年;Zhang et al.， 2022;Arias等 人，2023年），或者，只有在资源不足或植物经历压力时（Funk和Vitousek，2007年; Santamarina等 人，2022 年）。Zhu 等 人观察到的差异可能是。在这两个实验之间，是由于植物在田间条件下经历的更具竞争力的条件。我们不能否认，涉及与田间实验中相似的物种混合的盆栽实验不会产生类似的结果。然而，至少一些具有类似实验设计的先前研究发现，竞争是减少 - 而不是增加 - 本地人和外来物种之间性状差异的一个因素（Blumenthaal & Hufbauer，2007）。这表明问题可能不在于 Zhu 等 人缺乏竞争。S POT 实验，而是与 POT 实验相关的内在限制。

也许是 Zhu 等 人最有洞察力的发现。是只有田间混合物才能识别预测未来物种丰度和持久性的性状（比叶面积 （SLA）、植物高度、地上生物量）。田间混合物还表明，外来植物总体上比本地植物更持久，多年生植物比一年生植物更持久。这些结果与对本地-外来物种相互作用的普遍预期一致，并且之前的一些研究表明，田间研究如何检测罐装实验无法识别的本地和外来差异（Leffler 等 人，2014 年）。尽管如此，以前的研究仅限于一个或几个物种进行此类比较，以及 Leffler 等 人的荟萃分析。（2014 年）提供了一个综合观点，然而，它不能像同时比较 64 个物种的单一研究那样提供直接证据。

因此，看到大规模实验验证我们的理论假设是令人欣慰的，但认识到罐子实验可能缺失如此之多，这令人担忧。可以得出两个快速的结论：首先，罐子实验是安全的，因为它们不太可能不切实际地放大或过度表示现有的差异，也就是说，它们不太可能导致 I 型统计错误（假阳性）;其次，罐子实验可能会误导我们忽略如果在该领域进行研究将非常有用的因素和特征。也就是说，它们极有可能导致 II 型统计错误（假阴性）。

这是一个发人深省的见解，通过基于大量但较小的研究（Leffler et al.， 2014）的荟萃分析以及 Zhu 等 人的大规模实验来证实它，应该让我们重新考虑所涉及的权衡。总是需要在高度受控的罐子实验中运行实验，但这些实验应侧重于事先在该领域广泛确定的特定性状或处理。在罐子实验中探索广泛的性状以确定哪些性状将是有意义的预测因子，这可能看起来是一个有效且有吸引力的选项，但最终可能仅在外观上有效。这种方法很可能会错误地导致我们忽略之前应该通过实地研究确定的重要预测性状或因素。