Deciduous Woodlands

Deciduous Woodland: Vegetation and Fauna

The distinctive feature of deciduous woodland is deciduous trees.

Deciduous plants shed their leaves in autumn, before the cold winter months. Low temperatures would reduce photosynthesis, and make water uptake from frozen soil difficult. Deciduous trees don't just lose their leaves – they can slow down their metabolism to conserve energy throughout winter.

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Plants end their dormancy period at the beginning of spring, when temperatures begin to rise and organisms begin to bud.

Layered Vegetation

Deciduous woodlands have three distinctive vertical layers.

The Canopy

The canopy is the upper layer of the woodland, formed by mature tree crowns. Light availability is high, enabling rapid photosynthesis. As a result, the canopy supports the majority of the woodland's primary productivity. The canopy also provides protection from strong winds, harsh sunlight, and heavy precipitation.

The Understorey

The middle layer of the woodland is known as the understorey, usually comprised of shrubs, herbs, and seedlings of canopy trees. The understorey receives much less sunlight, so plants need to be shade-tolerant. Humidity levels are higher than in the canopy.

The Forest Floor

The lowest layer of the woodland is the forest floor. It's made of soil, decaying plants, and epiphytes.

Sunlight levels are low, and humidity is high. The forest floor plays an important role in nutrient transfer between the vegetation and the soil.

Fauna of Deciduous Woodland

Deciduous woodlands are home to a wide variety of fauna, including mammals, birds, snakes, and invertebrates. Animals can be found within all three vertical layers.

Animal populations in deciduous woodlands change throughout the year. Many mammals hibernate during colder winter months, while bird species migrate to warmer climates.

Deciduous Woodland: Locations

Deciduous woodlands are found around the world, but are mostly concentrated in mid-latitude areas of the Northern Hemisphere, such as:

• Europe (excluding northern Scandinavia and the Mediterranean)

• US

• Canada

• Japan

• China

• Russia

Locations in the Southern Hemisphere include:

• Chile

• South Africa

• Australia

• New Zealand

These ecosystems thrive in mountainous areas, and regions with a range of soil types.

Deciduous Woodland: Climate

To support deciduous woodlands, a region needs seasonal temperature variation and year-round rainfall.

Temperature

Deciduous forests experience seasonal temperature changes. Winters average 0ºC, while summers can reach up to 35ºC. The difference between summer and winter temperatures is significant, but not as extreme as some ecosystems.

Precipitation

Deciduous woodlands don't have dry and wet seasons. Instead, significant amounts of rain fall throughout the year, including summer rain and some winter snow. Precipitation levels range from 70-200 cm annually.

As a result, deciduous woodlands have a regular water supply.

Fig. 2 - a deciduous woodland ecosystem in the UK, experiencing cold winter temperatures and snowfall. Unsplash

Deciduous Woodland: Characteristics and Importance

Woodland ecosystems are characterised by a high biodiversity. They are home to a wide range of animals, plants, and fungi.

Deciduous woodlands are considered biodiversity hotspots, giving them a range of important functions.

Resources

Deciduous woodlands provide resources to humans in the form of ecosystem services.

Let's focus on two particular regulating services of deciduous woodlands – climate regulation and control of soil erosion.

Climate Regulation

Woodlands play a critical role in carbon storage. When trees photosynthesise, they extract carbon dioxide from the atmosphere. Carbon dioxide acts as a greenhouse gas, trapping heat in the Earth's atmosphere and leading to increased temperatures.

Furthermore, forests affect atmospheric moisture and rainfall patterns by evapotranspiration.

It's estimated that 40% of rain over land originates from evapotranspiration processes.

Control of Soil Erosion

Trees prevent soil erosion in multiple ways:

• Intercepting heavy rainfall to stop 'splash erosion'

• Acting as a windbreak

• Roots binding soil to sloping ground

• Reducing the amount of water in the soil through transpiration

Threats to Deciduous Woodland

These diverse and important ecosystems are under threat.

Deforestation

A rapidly increasing human population has led to widespread deforestation to provide land area, resources, and opportunities for agriculture.

Deforestation leads to habitat damage and biodiversity loss. It also impacts climate regulation and soil erosion.

Fragmentation of Remaining Woodland

Destructive activities, such as deforestation, can result in habitat fragmentation.

The main problem associated with habitat fragmentation is species loss. Smaller habitats result in smaller populations, which face a higher risk of extinction. Furthermore, disconnected habitats negatively impact dispersion and migration. Fragmented habitats also have a higher edge area, making them subject to edge effects.

Biodiversity is lower at the edge of a habitat than at its centre.

Poor Management

Poorly managed woodlands face a higher risk of wildfires.

Wildfires are common after hot summers; the heat has dried out vegetation, making it easy to ignite.

A lack of woodland management leads to thick, overgrown forests, where fire can spread quickly. Furthermore, unmanaged forest often lacks regulation on campfires and barbecues – common causes of accidental wildfires.

Conservation of Deciduous Woodland

How are deciduous woodlands conserved to prevent further degradation of these threatened ecosystems?

Protected Areas

Protected areas are locations that receive protection because of recognised ecological or cultural value.

Protected areas limit deforestation, habitat damage, and unsustainable exploitation of natural resources.

Legal Protection of UK Ancient Woodland

The UK's ancient woodlands are protected by law. Any developments near a site of ancient woodland require planning permission, where the developer must:

1. avoid damage

2. mitigate against any damage

3. compensate for loss or damage

These legal requirements help protect over 600,000 hectares of ancient woodland in the UK.

Conservation Management

Deciduous woodland ecosystems can be conserved using coppicing and pollarding management strategies.

Coppicing

It may sound counterintuitive, but coppicing actually promotes woodland biodiversity. Regular coppicing lets light reach the ground, enabling other species to grow. Furthermore, coppicing promotes a varied age structure. This provides diverse habitat and cover.

Pollarding

Regular pollarding leads to the rapid formation of tree hollows, a habitat associated with ancient woodlands. It restores saproxylic (related to dead and decaying wood) habitats, and conserves hollow-dependent fauna.

I hope that this article has explained Deciduous Woodlands for you. Remember that they are temperature forests dominated by deciduous trees (that lose their leaves every year). Deciduous woodlands experience seasonal temperature variation and large amounts of precipitation throughout the year.

^{1. British Trust for Ornithology, Swallow guide: migration, nesting and where to see, 2020}

^{2. Climate Change Post, More than carbon storage - The role of forests in climate change, 2017}

^{3. Michael E. Ritter, Midlatitude Steppe, The Physical Environment: an Introduction to Physical Geography, 2022}

^{4. Neil Campbell, Biology: A Global Approach, Eleventh Edition, 2018}

^{5. The Woodland Trust, Ancient Woodland, 2022}