Plants in the Porter Valley & Their Ecology (2003)

Overview This document discusses the ecology and plant diversity of Porter Valley, highlighting native and introduced species. ​

Abstract

• The report aims to identify, publicize, and protect the ecological capital of Porter Valley for Sheffield's inhabitants. ​
• It complements a 2001 ecological survey covering both plants and animals. ​
• The report includes 14 investigations divided into native and introduced plants. ​
• It highlights changes in land use since the Agricultural Act of 1945, noting a decline in farmland habitat quality. ​
• Special studies focus on characteristic or rare plant species, including gorse, wood barley, and orchids. ​

Native Plants

• The first section examines the impact of land-use changes on native plant habitats.
• Over the last 60 years, farmland has become poorer for wildlife. ​
• Remnants of earlier landscapes, such as holly haggs and older grasslands, provide rich habitats. ​
• Notable findings include 2.4 km of ancient hedgerows and a veteran oak tree.
• Special studies include two gorse species, wood barley, and four types of orchids. ​

Past Landuse

• Significant changes in farming practices since the 1945 Agricultural Act are discussed. ​
• In 1937, one-third of the area was under arable cultivation, primarily oats, barley, and potatoes.
• The current focus is on livestock rearing, with sheep, cattle, and alpacas. ​
• The intensification of agriculture has led to poorer habitats for wildlife. ​
• Historical weed flora may persist in soil seed banks, indicating potential for rare annuals. ​

Holly Haggs

• Farmers historically used holly leaves as winter fodder, leading to the establishment of holly haggs. ​
• The report identifies about a dozen possible holly haggs in Porter Valley. ​
• Most identified haggs are near stone walls and may be around 100 years old. ​
• Evidence of coppicing is unlikely, as modern trees derive from suckers of earlier trees. ​

Hedgerows

• Most hedgerows were planted following Enclosure Awards in the late 18th century. ​
• The survey identified 1.14 km of old species-rich mixed hedgerow, mostly unmanaged. ​
• The composition includes 12 woody species, with hawthorn being abundant. ​
• The presence of blackthorn is significant, as it is rare elsewhere in the valley. ​
• The report suggests no immediate threats to these hedgerows.

Gorse

• Two types of gorse are present: common gorse (Ulex europaeus) and western gorse (Ulex gallii). ​
• Common gorse flowers around Easter, while western gorse flowers in late summer. ​
• The report notes that spring gorse is rarer in the valley. ​
• Historically, gorse was used for winter fodder and other agricultural purposes. ​

Older Grassland

• Eight areas of older species-rich grassland were identified, with no new sites discovered.
• The report details the composition of these grasslands using quadrat sampling.
• Acid and neutral grasslands are present, with various characteristic species. ​
• The report emphasizes the importance of these grasslands for biodiversity.

Introduced Plants

• Introduced plants outnumber natives two to one, particularly in urban fringe areas. ​
• High-impact introductions include Japanese knotweed, giant knotweed, and Himalayan balsam. ​
• The current distribution of these species has been mapped for future monitoring. ​
• Other non-native species include horticultural escapes from gardens and contractors' activities. ​

Evaluation

• The report suggests methods for preserving and enhancing ecological treasures in Porter Valley. ​
• Awareness and sympathetic management are crucial for the conservation of these habitats.
• No financial investment is required for the suggested actions.
• A similar report on animal ecology is recommended to complete the understanding of the valley's ecology. ​