• Key message

Litter trap is considered the most effective method to quantify seed production, but it is expensive and time-consuming. Counting fallen seeds using a quadrat placed on the ground yields comparable estimates to the litter traps. Ground quadrat  estimates derived from either visual counting in the field or image counting from quadrat photographs are  comparable, with the latter being also robust in terms of user sensitivity.

• Context

Accurate estimates of forest seed production are central for a wide range of ecological studies. As reference methods such as litter traps (LT) are cost- and time-consuming, there is a need of fast, reliable, and low-cost tools to quantify this variable in the field.

• Aims

To test two indirect methods, which consist of counting the seeds fallen in quadrats.

• Methods

The trial was performed in three broadleaved (beech, chestnut, and Turkey oak) tree species. Seeds are either manually counted in quadrats placed at the ground (GQ) or from images acquired in the same quadrats (IQ) and then compared against LT measurements.

• Results

GQ and IQ provide fast and reliable estimates of seeds in both oak and chestnut. In particular, IQ is robust in terms of user sensitivity and potentially enables automation in the process of seed monitoring. A null-mast year in beech hindered validation of quadrats in beech.

• Conclusion

Quadrat counting is a powerful tool to estimate forest seed production. We recommend using quadrats and LT to cross-calibrate the two methods in case of estimating seed biomass. Quadrats could then be used more routinely on account of their faster and simpler procedure to obtain measurements at more spatially extensive scales.

中文翻译：

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定量计算温带阔叶树种种子产量的地面计数方法的比较

•关键信息

垃圾收集器被认为是量化种子产量的最有效方法，但它既昂贵又耗时。使用放在地上的四边形对落下的种子进行计数，得出的估计值与垃圾桶的估计值相当。 从实地视觉计数或从方形照片的图像计数得出的 地面方形 估计值是 可比的，后者在用户敏感性方面也很可靠。

•上下文

森林种子产量的准确估算对于广泛的生态研究至关重要。由于诸如垃圾收集器（LT）之类的参考方法既费钱又费时，因此需要一种快速，可靠且低成本的工具来在现场量化此变量。

•目的

测试两种间接方法，包括计算掉落在四方类动物中的种子。

•方法

该试验是在三种阔叶（山毛榉，栗树和土耳其橡木）树种中进行的。可以将种子手动放置在地面上的四边形（GQ）中，也可以从同一四边形中获取的图像（IQ）中手动计数，然后与LT测量值进行比较。

•结果

GQ和IQ可以快速，可靠地估算橡树和栗子中的种子。尤其是，IQ在用户敏感性方面很强大，并且有可能在种子监视过程中实现自动化。在山毛榉中无效的最后一年阻碍了山毛榉中四方动物的验证。

•结论

Quadrat计数是估算森林种子产量的有力工具。在估计种子生物量的情况下，我们建议使用Quadrats和LT交叉校准这两种方法。由于Quadrat更快，更简单的程序，因此可以更常规地使用它们，从而可以在更大的空间范围内获得测量结果。