Bluebells (Hyacinthoides non-scripta)

The Hallerbos is much more than only bluebells.

Yes, the millions of delicate purple flowers are world-famous, and the single reason why thousands of people flock together here every day at the height of the season. Yet there is a lot more to discover below the tall beech trees, if you know where to look.

The herb-paris (Paris quadrifolia), less common in the forest, but a surprisingly beautiful find

Every year in the middle of April, we release the students from our Bachelor’s in Biology in the Hallerbos for a day. To admire the fields of bluebells, yet more importantly to give them an impression of the ecological dynamics in a Belgian forest. Concerning the latter, the Hallerbos is exemplary. With its gentle slopes and little streams, the forest hosts interesting gradients: from wet to dry, from nutrient-rich to nutrient-poor, from basic to acid.

A little valley, showing how the understory in the Hallerbos is restricted to spots that are not too dry or nutrient-poor

The resulting understory vegetation neatly mirrors these gradients, revealing the power of the abiotic environment in defining what grows where. Bluebells? Yes, yet only where it is not too wet and not too dry, and where enough nutrients are available and the soil is not too acid. Typical water-related species close to the streams? Yes, yet notice the differences in species composition with the spring- and seepage-areas.

A little stream in the Hallerbos, surrounded by endless fields of wild garlic (Allium ursinum)

Looking at a forest from this ecological point of view also teaches you to appreciate the less eye-catching plants as well. The more you learn how to read a forest, the more you will appreciate the returning certainties, and the surprising encounters.

A really wet patch of forest, with giant horsetail (Equisetum telmateia) in a field of wild garlic (Allium ursinum).

The students also learn to disentangle the feedback effects of the vegetation on the abiotic conditions. How beech trees slowly acidify the soil, making it harder for understory plants (like the bluebells) to survive. How conifers do the same, yet significantly quicker, reducing the understory diversity to less than a handful of tough survivors. Or how understory species have to act fast, before leaves on the towering trees are fully grown and shade out all the light. Simple rules, but revealing how everything in ecology is connected.

Young beech leaves. As soon as they are fully grown, spring in the understory is over

Give it a try yourself next time you are out in the forest: try to search for signs of the underlying abiotic conditions in the vegetation, and look for species that are surprisingly often occurring together. You’ll see, playing nature’s detective is a lot of fun!

Want to know more? Discover the nice picture gallery with more stories on the right of this blog.

A young beech seedling (Fagus sylvatica), looking nothing like a beech, yet everything like a tiny dancer…