Vertical Structure
The vertical structure of woodlands refers to the layers and zones of the area. Woodlands are not static and their composition and structures are always changing. The structure of woodland affects its biodiversity and as a general rule the more structures and layers woodlands have the greater the variety of life, as Chris Starr explains it is “diversity in structure” (Starr, Woodland Management, 2009, p26). The types of trees present also affect this structure. Some woodland is composed of many different species, while in others they are predominately one species, perhaps planted at the same time. The strata as Starr asserts is “much as a cityscape might be” (Starr, 2009, p26). Woodland is composed essentially in four different layers:
· The Tree or canopy layer-The crowns of mature trees
· The shrub layer- taller shrubs and smaller trees
· The field layer-taller flowering plants and bracken
· The ground layer-smaller plants including mosses and the soil.
The layers of woodland can give us clues to past and current management of the area and not every woodland contains each layer. It can be difficult to distinguish all the layers present and added to this, different types of woodland will exhibit different proportions of each layer.
Pioneer species such as traveller’s joy, birch and alder produce large numbers of wind pollinated seeds. These plants like a lot of light and grow quickly and they as Starr phrases it “literally pioneers the way for the next group of trees” (Starr, 2009, p23). Pioneer species are often found on the edge of woodlands or scrub land where the woods start or end and in glades which may be naturally made through fires or man-made through clearing.
I visited four very different local woodland sites to explore and discover more about these layers and features first hand. To present my findings I have put together a presentation which includes videos that capture my learning journey. I found this task really interesting and it was amazing to start seeing how all these levels and layers were interconnected and related. As I looked closely I began to see how the tallest trees related and affect the younger trees and the foliage growing below, how the trees were competing for sunlight and space and how the ground differed under different tree species. I also began to see how the conditions at the edge of the woodland differed to that of those in the middle of the woodland.
Horizontal Structure
The horizontal structure of woodland refers to the differences found at different points, or strands of woodland. These differences can be caused by a number of factors including land topography such as rocks, rivers, fire, disease and the depth and moisture level of the soil also play a part in the horizontal structure. Just like the vertical structure of the woodland the horizontal structure varies in every woodland. Humans have also influenced this structure through woodland management especially plantations and controlling the spacing and density of the trees within the woodland. There is a real difference between self-set and managed woods as it can have a huge impact on the varying ages and varieties of species as well as the density and spacing which will of course also alter the vertical structure.
The spacing and density of the woodland depends on the “types of trees and shrubs that grow there and also if the woodland has been managed by humans.” (learning in the leaves.co.uk, 2020, accessed 29/6/20). In coniferous (Evergreens) forests and plantations you often find that the trees are tightly packed together. This tight packing leads to the canopy (top layer of a forest) being so dense that little/no light hits the ground below. This means younger plants, the under-story, find it difficult to grow on the forest floor. The lack of younger/smaller plants reduces the food source for surface living animals. In these woodlands some insects/birds are unable to survive. These conditions lead to significantly reduced biodiversity in coniferous woodlands.
While in deciduous woodlands (shed leaves) there are significantly higher levels of biodiversity. As deciduous woodlands offer a variety of layers/structures/environments that lead to both plants and animals thriving because these are the best conditions to grow well. John Seymour in his book The Lore of the land, (2012) writes that:
“Let us therefore learn more from nature and making our planting diverse…..and selection forestry is much better for the soil.
Go into a mixed-age, mixed species woodland particularly one with a high proportion of broad-leaved trees….and you will be half deafened by the song of birds”
(Seymour, p105-108, 2012).
I have tried to document my learning through a series of video diary entries and while visiting four different woodland sites I looked and considered the horizontal structures of these different sites. I did notice how different coniferous areas were to deciduous ones and the variety of under-story plants that were present. I also noticed a difference between planted and self-set woodland areas and also the amount of biodiversity that was present in these sites.
I have found this task really interesting and exciting and it was great to get out and explore, observe and absorb the different woodlands on my door step. I have enjoyed exploring other ways of recording and documenting my learning journey and feel that I am learning so much as I wander and discover more.
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