Accelerating oligotrophic habitat formation on slate waste Edwin Rowe, Julie Willamson, David Jones, Mark Nason and John Healey Institute of Environmental Science, University of Wales, Bangor LL57 2UW.

European Commission LIFE programme Alfred McAlpine Slate Ltd. (Penrhyn, Wales) Villar del Rey Slate Quarries Ltd. (Estremadura, Spain) Dan Morrissey Ltd. (Wicklow, Ireland) “Sustainable post-industrial land restoration and re-creation of high biodiversity habitats”

Slate waste Slate: metamorphic rocks which can be split thinly for roofing tiles and other building products. Extraction and processing produce a large proportion of waste. The extensive waste tips resulting from historic and current workings often have little vegetation cover.

Factors limiting plant establishment and growth on slate waste Low water holding capacity Lack of fines Small nutrient content (N, P) Surface instability Grazing Infrequent plant establishment

Restoration approaches 1. What should the target habitat(s) be? Who decides? 2. How can we determine which are the most important limitations to plant growth, and how to overcome them? Surveys Experiments Modelling 3. How can we make recommendations accessible to restoration practicioners?

Deciding on target habitats Processes: Defining stakeholders and finding out their priorities Weighing costs, and benefits to different stakeholder groups Evaluating progress towards target habitats Issues: Biodiversity definitions “Naturalness” - timescale? Weeds and aliens Conserving successions? Stakeholder definitions

Determining limitations: Surveys Geographical Information Systems GIS’s Combine spatial data in useful ways Produce stratifications by altitude, tip age, etc., including new stratifications e.g. aspect, exposure Outputs are accessible to field workers and the public

Detailed surveys Limiting factors can be inferred by examining the distribution of plants in relation to, for example, Substrate texture Tip age Position on tip Other plant species This approach is limited by Difficulty of ageing trees Confounding (e.g. tips formed at different times have different composition) Variability Feedbacks and circularity

Time Soil water holding capacity Organic fines Mineral fines Soil formation and plant growth = =

Plant establishment and growth: Key questions Does establishment of woody plants depend on prior establishment of plants or lichens ? (initial or relay floristics?) How much water-holding capacity is needed to support a given amount of biomass? What are the rates of accumulation and loss of organic and mineral fines? How is organic matter accumulation affected by nutrient supply, and plant species? How does the interaction between nutrient supply and water holding capacity affect plant community composition?

Plant establishment and growth: Working hypotheses The main limitation to plant growth on slate waste is episodic drought. The equilibrium leaf area index on a tip is a simple function of the water-holding cacpwhich canopy area which can be supported Does establishment of woody plants depend on prior establishment of plants or lichens ? (initial or relay floristics?) How much water-holding capacity is needed to support a given amount of biomass? What are the rates of accumulation and loss of organic and mineral fines? How is organic matter accumulation affected by nutrient supply, and plant species? How does the interaction between nutrient supply and water holding capacity affect plant community composition?

Experimental programme: Effects of different substrate amendments on tree establishment. Effects of transfer method, mulching and fencing on heathland establishment. Effects of fertilizer additions to natural successions on tree growth, tree herbivore assemblages and ground flora. Methods for establishing trees on very free-draining slopes

Experiment: Effects of different substrate amendments on tree establishment 6 species Alder (Alnus glutinosa) Birch (Betula pendula / pubescens) Gorse (Ulex europaeus) Oak (Quercus petraea) Rowan (Sorbus aucuparia) Willow(Salix caprea / cinerea) x 3 water-holding treatments None 0.5 m of clay subsoil Polyacrylamide 3.4 g / tree x 3 nutrient supply treatments None Sewage cake plus paper waste Slow release 15:9:10 NPK 8.3 g per tree

Early mortality of trees (Number of trees dead, out of 450 per treatment, in first 8-12 weeks after planting.) 1. Main effect of water-holding amendments None Clay Gel  2 : P < Main effect of nutrient amendments NoneNPK prillsSewage + Paper waste  2 : P < 0.01

Experiments: Effects of substrate, transfer method and grazing protection on heathland establishment Trials previously set up Effects of grazing protection on establishment of planted heather. Effects of grazing protection on heath topsoil transfer. New experiments Effects of substrate and of grazing protection on heath topsoil transfer Effects of brash application rate and mulching rate on heath brash transfer

Stands: HF = Target heathland (flat area) HS = Target heathland (sloping area) B1 = sheep and rabbit fenced; peat transfer; coir matting B2 = sheep and rabbit fenced; peat transfer B3 = not fenced; peat transfer; coir matting B4 = not fenced; peat transfer C1 = sheep fenced; heather planted C2 = sheep fenced; peat transfer; heather planted C3 = sheep fenced; peat transfer C4 = not fenced; heather planted C5 = not fenced; peat transfer Trajectories in DECORANA floristic ordination space of created heathland stands in the 1 year (B) or 2 years (C) after setup. Initial positions are marked by asterisks.

Publicising recommendations: Manual of best practice in slate waste restoration Introduction Scope: Hard rock quarries in Europe Who the manual is aimed at Identifying resources Site survey (GIS, EIA) Organisations (for support and expertise) Funding organisations Defining targets Biodiversity Landscape Amenity and recreation Industrial history Deciding on targets Who decides? Methods for consultation Costs and benefits Weighing requirements and preferences Techniques for accelerating formation of biodiverse habitats Landforming Soil amendments Seeding and planting Evaluating success Costs and benefits Biodiversity indicators Assessing public perceptions

Modelling effects of litter on hydrology If drought is the main limitation to plant growth on slate waste, the eventual plant cover will depend on the amount of water held within the soil, and the distribution of this available water in relation to plant roots. This hypothesis will be tested by examining the relationship between the size of naturally occurring soil pockets and the biomass they support (Figure 1). The contribution of litter to soil water holding capacity will be measured, and modelled using WaNuLCAS 1. Some preliminary model outputs, using WaNuLCAS default settings, are presented here for the purpose of illustration. Simulations Simulations of tree growth and litterfall illustrate how soil organic matter might develop over the first few years after tree planting (Figure 4). Soluble or “metabolic” litter C is completely depleted shortly after litterfall, but “structural” litter C accumulates over time.

Simulated tree growth and soil organic matter development in first 4 years after planting (WaNuLCAS default settings).