Sphagnum re-introduction to degraded peatland

Riggs, Joshua (2017) Sphagnum re-introduction to degraded peatland. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

Healthy functioning peatlands are of global and national importance as active carbon sequestering ecosystems. The Southern Pennines contains some of the most severely degraded Blanket Bog in the UK through historic air pollution, overgrazing and poor management has led to an actively eroding system. Current landscape restoration is focused on surface stabilisation and increasing biodiversity, ultimately Sphagnum reintroduction, a keystone species in functioning bog. To stabilise eroded peat and provide a nurse crop of amenity grass cover, it has been necessary to directly apply additions of Lime and NPK Fertiliser to the highly acidic nutrient poor peat surface. There has been concern over the potential effects that this nutrient application could have on the growth of Sphagnum which is specific nutrient poor acidic soil. Although previous studies have found application of Fertiliser to be directly toxic to Sphagnum (particularly greenhouse experiments), there has been little consideration of the mitigating effect of the typical climatic effects and high precipitation faced in the field. This project aims to investigate the effect of Lime and NPK Fertiliser effect on Sphagnum growth, and if this potentially negative effect is mitigated by field conditions. Field trials were setup in the Southern Pennines. Trials were undertaken on two distinct Sphagnum communities in different stages of development: Young establishing and Mature established. Additions of Lime and NPK Fertiliser were applied alongside a Control of no addition. Growth measurement data was collected to provide a comparison of treatments. Greenhouse experiments were also trialled to replicate the field experiments under controlled conditions. Applications of Lime and NPK Fertiliser were applied separately and in combination alongside a control to test Sphagnum growth response to specific nutrient application. The trial was also split by watering treatment to attempt to replicate the field precipitation conditions. Half the trial was subjected to watering similar to Southern Pennines rainfall levels, the other treatment was watered at ‘optimum’ greenhouse levels. Results from the greenhouse experiment showed there was a significant nutrient effect on Sphagnum growth. Fertiliser alone Lime and Fertiliser combined had a significant negative effect on growth and caused dieback of Sphagnum. This negative effect was mitigated by watering treatment. When watered at field precipitation levels it was found that the negative impact of Nutrient was reduced. There was a strong significant difference between the watering treatments. This result was replicated in the field, When Nutrient was applied to Young establishing Sphagnum there was no significant effect to Sphagnum area size (mm2) or total count. When nutrient was added to mature established Sphagnum there was an immediate negative effect on Sphagnum height increment (mm2), but this was short lived and followed by a period of recovery and re-growth. It was concluded that impacts of Lime and NPK Fertiliser on Sphagnum may be less than originally thought. Where possible Nutrient addition directly applied to Sphagnum should be avoided since there is a potential direct toxic effect and the potential for increased competition form vascular plants. However Sphagnum communities do not appear to be at risk of irreparable damage from Lime and NPK Fertiliser application.