Ecosystem Transition - Bat Park

Landscapes change (spot the difference over 130 years), but changes within a woodland such as Wilderness Wood can be relatively rapid, especially when given a helping hand.

Monday 9th October 2023

I've taken a break from the woods this last week, visiting my son in Hamburg. A pleasant enough city and a good reset for Wilderness Wood appreciation.

During my break my mind has wandered to Bat Park and what we have learned so far about this recently created ecosystem, which is still very much in transition.

Imagine an area subjected to glaciation, where a river of solid ice has slowly moved across the landscape bulldozing solid rock and soil out of a hillside. No ice sheets ever got this far south in the UK, but substitute a mechanical digger for ice and the end product is the same.

April 2018 - Bat Park’s ‘post glacial’ surface. Little more than bare rock and a thin mineral soil

Back in 2018 when I first looked out across the barren waste of this area there was barely any sign of life. Heavy rain had led to surface runoff carrying away what little soil remained. The flat nature of this newly sculptured landscape, with its impermeable bedrock, meant that it was pretty waterlogged for long periods, but as soon as the sun appeared, its southerly aspect quickly ensured an arid desert replaced it.

Periods of heavy rainfall leave the poorly drained surface waterlogged

Bat Park May 2018. An arid desert in the middle of Wilderness Wood (from North East Gate)

Close-up of the ‘desert’ - blue oblongs highlight areas washed by surface run-off

Nonetheless, nature provides species adapted to almost any conditions, but coping with fluctuating extremes of water availability is one of the most testing.

Sheep’s Fescue copes with minimal soil and the small amount of water from the occasional rain puddle (circled white)

On any given day a plant may struggle to find enough water to supply its leaves with the water required for transpiration. Leaves vital for photosynthesis quickly pass their wilting point and shrivel. Without evaporating water on their leaf surface, what little water roots do find is no longer drawn up through the plant. This means dissolved minerals from the soil are no longer available. Further, without evaporation at the leaf surface it quickly overheats causing leaves to turn brown - in much the same way as many tree leaves have this summer. No soil minerals and no photosynthesis means death will not be far behind.

A sedge turns brown from dessication

Fortunately some plant species are adapted to this, sending roots deep into the ground in search of water. Others, such as fescue grasses, roll their leaves into tubes to trap moist air within. Low growing, rosette forming sedges occupy the layer of slow moving air close to the ground reducing evaporation loss. Plantains have waxy cuticles to protect them.

A hawkbeard flower struggles to grow at Bat Park

Hawkbeard (daisy family) forms a low-growing rosette of leaves thereby reducing evapotranspiration due to wind exposure

Somehow a few species survive, only to have to cope with a period of water excess, when it rains and the surface is waterlogged. Waterlogged soils hold far less oxygen, yet another element vital for plant respiration to take place. The few species that survive this alternating water supply issue have yet other strictures to contend with eg. rabbit grazing.

Only the lowest growing species can evade the depredations of grazing rabbit (mind, the poo provides excellent fertilizer for those that do).

It is therefore no wonder that Bat Park currently only supports the lowest growing, toughest individuals in Wilderness Wood. Nonetheless, 5 years-on, life is returning.

There is one major benefit from this tough environment and that is none of the bigger nutrient demanding species such as Dock, Nettle and Thistle can survive. Bat Park is gradually developing a unique acid lowland grassland flora which will in time become a riot of colourful flowers found nowhere else in Wilderness Wood and thereby adding to its biodiversity.

Wakehurst Place’s acid lowland grassland - one day this could be Bat Park

David Horne - why not following my exploration on foot and by bike around the coast of the UK on www.leggingroundbritain.com