Experimental design

The information here explains the experimental design from which we will assess the impacts of different management regimes on key ES (carbon, water and biodiversity).
Schematic experimental layout at each site

The overall purpose of the project is to assess the impact of different management techniques on areas with predominant heather coverage. The project will monitor changes in peatland variables in response to different management (i.e. treatments). The main treatment is to mow/cut a plot area in-line with current mowing management techniques and then compare that to a control plot that has undergone the ‘business as usual’ burning regime; we will also consider other potential treamtents (see Todd et al., 2000 for comparable MoIinia issues). However, herbicide useage seems an unlikely option (see Milligan et al., 1999; Rogers, 1996), mainly due to the possible impacts on water quality. The project will consider one large catchment-scale mowing treatment (across the treatment sub-catchment) and three small plot-scale treatments at small experimental plots within the treatment and control sub-catchments. The main mowing treatment will reflect the current mosaic nature of burn strips and maintain a succession of heather ages. One cut every other year (1/3rd) is proposed to reflect a more usual burn management. There was no burning inside the sub-catchments in the 2012/13 season (ie. pre-treatment period). The small plot-scale treatments are:
'do nothing', leaving or removing brash, and either with or without Sphagnum addition (see below list).

The following parameters will be monitored: meteorological variables, carbon fluxes, carbon stocks, GHG emissionspeat pipes, vegetation dynamics, water balance and water quality and empirical and process models will allow up-scaling of the findings in space and time, thus making them more policy relevant.

Overall we propose a combination of two statistical approaches (designed in consultation with an experienced statistician, Dr. Calvin Dytham) within this project allowing large catchment-scale (most policy ‘relevant’) and small plot-scale (most scientifically ‘relevant’) manipulations. For this, the Before-After Control-Impact (BACI) approach (i.e. comparing the time series behaviour of pre-treatment versus post-treatment; Stewart-Oaten et al., 1986) will allow us to establish a robust, replicated experimental study (with one major catchment-scale treatment and several additional restoration plot-level treatments being applied across three sites). We propose that this experimental structure will allow sound statistical analyses of both within and between sites as true replicates exist at both levels.

Burning at Whitendale and Mossdale - ready to put out unwanted patches at the edges. Good quick and cool burn at all sites ... but most carbon gone up in smoke.

Mowing at Mossdale (Tom Iveson) - in effect leaving most carbon on the peat but relying on fossil fuel. Horrible weather but that's one of the advantages of mowing - can be done in nearly all weather.

We established, at each of the three field sites, two adjacent sub-catchment scale experimental sites: the ‘control sub-catchment’ and the ‘treatment sub-catchment’ (see Figure). Within the treatment sub-catchment, mowing of heather and other alternatives will replace the 'business as usual' burning still to be continued in the control sub-catchment; mowing and burning - see movie clip below - will happen on equal areas in each catchment. Four main monitoring areas are set up within each of the two sub-catchments at each of the three field sites. These areas are treated as ‘blocks’ when data for all three field sites are considered together for treatment effects.

Plot level treatments replicated across four blocks are (based on a stakeholder workshop held in Yo
rk in February 2013):

Burning at Mossdale 2015

Control (burn)

Control (burn) + Sphagnum


T1 mowing + brash

T2 mowing - brash

T3 mowing frequency + brash + Sphagnum

T4 mowing frequency - brash + Sphagnum

T5 ‘do nothing’ no management control treatment (no burn, no mow)

Mowing at Mossdale 2015

The Sphagnum addition will address which of the three (particularly) peat forming species (i.e. S. pallustre, capillifolium, papillosum) will be performing best, on either burnt or mown plots with or without brash removal. In Spring 2014, we applied a mix of the three species across half the mown 5 x 5 m plots (i.e. with or without brash) at a rate of 1 pellet per cm2. In addition we also applied increasing levels of Sphagnum within three 1 x 1 m plots alongside four burnt and mown plots (at Whitendale only) to assess density effects on establishing new Sphagnum on burnt vs. mown plots (with brash); levels were 200, 400 and 600 pellets per 1 m2.

Sphagnum (BeadaMoss) addition at Whitendale: 1 x 1 m plot additions (left: for the 5 x 5 m plot; right: three levels of pellet density additions - from low [200 per 1 m2] to high [600 per 1 m2]).      

Blocks will also be matched across field sites so that monitoring plots for a particular block will be over peat of a similar depth at all three field sites.  On the ‘control sub-catchment’, each of the four monitoring areas (blocks) will contain only one monitoring plot (giving four control plots – controls in the treatment area were considered but deemed impossible to accommodate due to the burn risk) whilst on the ‘treatment sub-catchment’, five monitoring plots (one for each planned treatment) will be set up in each of the four monitoring areas. The five treatment plots will be allocated randomly among the five GPR transect matched 5 m x 5 m monitoring plot positions identified within a block (i.e., in a stratified random design) and will be placed in areas of similar slope (~5-10°) and vegetation composition (i.e. heather coverage of ~40-60%). Each of these plots will contain a central (1 x 1 m) permanent monitoring plot (e.g. for vegetation monitoring). All treatments will start at the same time following the initial pre-treatment period of one growing season. The experimental design will enable data from all three field sites to be analysed either per site (i.e. four reps across the four blocks per treatment) or together (i.e. three reps in four blocks per treatment) using ANOVA (analysis of variance) or GLM (Generalized Linear Model) to compare the effect of different treatments, and post hoc tests, such as the Tukey’s HSD test, to identify any significant differences between factors. Whereas the latter is a true replication we acknowledge that the ‘per site’ approach does not strictly speaking represent independent replicates. However, the distance between monitoring plots and areas is large enough to limit any similarities as shown for other peatland .
Subpages (2): Catchment scale Plot scale