4. MONITORING TECHNIQUES
4.3. Biota
4.3.1. Vegetation
4.3.1.1. Introduction
To monitor population changes it is not necessary (or usually possible) to have an absolute population estimate and a relative measure of abundance is sufficient (Sutherland, 1996). To determine if objectives are reached, the most important variables to consider are plant species, the proportion of the ground they cover (or similar ‘dominance’ or ‘abundance’ measure) and their development (or succession) through time. The recommended procedure describes vegetation at three levels: the site level, the permanent plot level and the ground level. These levels are complementary and allow a good assessment of the vegetation of an entire site (Quinty & Rochefort, 2003).
The vegetation might be monitored at different time periods after the implementation of restoration procedures to determine if the new plant cover develops toward a peat bog plant community. Quinty and Rochford (2003) recommend for cutover peatlands that vegetation monitoring is not carried out during the first growing season after restoration and that monitoring should start on the second year and be repeated after the third and the fifth growing seasons. However, there may be situations were monitoring within the first year of restoration is crucial such as re-seeding an area of upland bare blanket bog or to establish near baseline conditions in the absence of pre-restoration monitoring
At the NE workshop on monitoring peatland restoration, experts stressed that Sphagnum cover (e.g.
S. palustre) was an important proxy for both water level and quality as well as peat surface conditions in upland and lowland peat forming systems and thus has been used as an indicator of restoration success (Appendix 2). Joosten & Couwenberg (2009) discuss the use of plant communities as proxies for greenhouse gas emissions (see section 4.9.4). Also, NVC characterization was deemed of importance for judging the restorability of lowland peat with M17 Scirpus cespitosus –Eriophorum vaginatum blanket mire being less challenging to restore but that areas of M25 Molinia caerulea – Potentilla erecta mire could complicate restoration efforts. Monitoring at Thorne & Hatfield moors (http://www.thmcf.org/home.html) has shown that the vegetation changes following hydrological restoration. These were initially recorded using indicator species followed by more detailed NVC survey and CSM.
A list of suggested positive and negative indicators for the restoration of raised mire is provided in Tables 5 and 6 (Wheeler and Shaw, 1995). The positive indicators in the restoration of raised mire for instance would include the major peat forming species (Sphagnum papillosum, S. magellanicum, S.
capillifolium and Eriophorum angustifolium), in association with other species characteristic of peatlands such as Erica tetralix, Scirpus cespitosus1 and Calluna vulgaris. Sphagnum species indicate reestablishment of the water table depth or the hydrological regime (Wheeler & Shaw, 1995;
O’Reilly, 2008). Species selected as indicators will depend on the objectives of the restoration, and the stage of recolonisation at which recording begins. Certain plant species can also be clearly identified as ‘negative’ indicator species particularly where they for large, dense stands (Table 6).
Negative indicators in this context would include Juncus effusus, a range of Sphagnum (S. recurvum2, S. fimbriatum, S. squarrosum) and other moss species (Pleurozium schreberi, Dicranum scoparium, Hypnum cupressiforme), indicative of drier or more enriched conditions, also, Pteridium aquilinum
1 Also referred to as Trichophorum cespitosum
2 Also referred to as Sphagnum fallax
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(bracken), Molinia caerulea and Eriophorum angustifolium. Several studies focus on the control and management of such species, illustrating their status as important ‘negative’ indicator species (Todd et al., 2000; Milligan et al., 1997; Le Duc et al., 2003).
Table 5 Suggested plant indicator species for monitoring progress towards a raised-bog objective (from Wheeler & Shaw, 1995).
Species Notes
Sphagnum cuspidatum, S. recurvum Often colonise areas with open/standing water S. papillosum, S. magellanicum, S.
capillifolium
Indicate satisfactory development of bog species Eriophorum angustifolium May invade precursor floating Sphagnum carpets,
or root directly into peat Erica tetralix / Scirpus cespitosus / Calluna
vulgaris
These are only indicators of ‘success’ if associated with peat-forming Sphagna (e.g. S. papillosum) as they are also constant species of wet heath communities
Other ‘desirable’ species include:Vaccinium oxycoccos, Narthecium ossifragum, Drosera spp., Rhynchospora alba, Andromeda polifolia, Sphagnum subnitens, S. pulchrum, (S. fulcrum, S. imbricatum)
‘Weed’ species, including birch/pine/Molinia Reduction in vigour and spread of these species (through rise in water levels and vegetation management) would be generally regarded as indicative of ‘success’
Table 6 Vegetational indicators of potential problems with respect to revegetation with bog species.
Note that in many cases it should be possible to mitigate the effects of adverse conditions through management and it should not be assumed that these are necessarily irreversible (from Wheeler &
Shaw, 1995).
Species Potential problem
Juncus effusus May indicate a eutrophication problem and/or disturbance
Birch/pine/Calluna/Molinia/Rhododendron Extensive invasion probably indicates conditions are too dry
Sphagnum recurvum, S. fimbriatum, S.
squarrosum.
May indicate some base or nutrient enrichment (atmospheric deposition)
‘Heathy’ Sphagna (e.g. S. tenellum, S.
compactum, S. molle; plus other bryophytes (e.g. Pleurozium schreberi, Dicranum scoparium, Hypnum cupressiforme)
Although these species may be present in small quantities in M18a vegetation, their establishment and spread in the absence of the aquatic or main peat-building Sphagna would suggest that conditions are not generally sufficiently wet
Fen species (e.g. Typha, Phragmites, Salix, Alnus)
Indicates minerotrophic water source and nutrient enrichment
‘Weed’ species e.g. bracken, Rumex acetosella, Chamerion, angustifolium, Poaceae (e.g. Calamagrostis canescens)
Suggests that conditions are too dry and possibly disturbed
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Dargie (2003) reviewed the main methods of floristic assessment undertaken on three different lowland raised bog sites affected by peat cutting operations as summarised in Table 7. The approaches are similar but the study indicates a need for greater uniformity of methods, which the author indicates is in part addressed by Common Standards Monitoring methods, for designated sites at least. However, an important point noted by many authors (e.g. Dargie, 2003; Ross & Cowan, 2003; Mawby, 2003) is that although lowland raised bog sites may have the same overall restoration aims (to re-wet the surface, reduce hydrological fluctuation, increase the cover and diversity of wetland species, to reduce cover of bare peat) the combination of restoration techniques able to be used on any one site has to be selected on a site by site basis. This is because restoration is driven not only by ecological factors but also by budget, human resources, landowner agreement, adjacent land use, access difficulties, and many other non-ecological issues. In addition, as more funds are attracted as the interest in the site increases, as for example, seen at Glasson Moss (Mawby, 2003), the restoration and hence the monitoring regime is added to and can become complex over time.
The focus needs to stay on the improvement of the site, and this may mean altering goals, target and restoration approaches during the restoration period.
Table 7 Summary of the approaches to floristic monitoring on lowland raised bogs (Dargie 2003)
Method Example Details
Floristic monitoring of indicator species by subjective overall cover
Fenn’s, Whixall and Bettisfield mosses
% extent of peat forming indicator species
(Sphagnum and Eriophorum) in each management sub-section recording results in a set of classes.
5 year repeat.
Floristic monitoring of indicator species using belt transects
Humberhead peatlands
Indicators are defined as (1) likely peat forming species, (Sphagnum spp, Eriophorum spp), (2) Andromeda polifolia and Vaccinium oxycoccos as indicators of peat condition, and (3) Juncus effusus in early stages of succession.
Estimation of % cover of each species for 10m either side of the transect line.
% cover transformed to area estimates per sub- compartment , and data incorporated into GIS Floristic
monitoring of all species using belt transect and vegetation mapping.
Wedholme Flow The quadrat data set records all vascular plants, bryophytes and lichens along belt transects within each restoration sub-compartment, and these data are analyzed to provide area cover measurements for each plant species that can be compared across sub- compartments and over time. These data are
incorporated into GIS. For storage and manipulation.
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The National Vegetation Classification (NVC) can be used for surveying and mapping vegetation.
Phase 1 habitat survey can provide an initial “environmental audit”; this method is useful for broadscale habitat mapping, which enable a more targeted selection of areas of high conservation
value for NVC-level analysis. The Countryside Survey
(http://www.countrysidesurvey.org.uk/reports2007.html) is a unique study or ‘audit’ of the natural resources of the UK’s countryside and includes assessment of the UK’s lowland and upland peatlands. The countryside is sampled and studied using rigorous scientific methods, allowing comparison of the present year’s results with those from previous surveys. This allows detection of the gradual and subtle changes that occur in the UK’s countryside over time. Maskell et al. (2008) provides details from the Countryside Survey 2007, which includes assessment of the UK’s lowland and upland peatlands. Table 8 provides an overview over the methods available and their applicability to different plant types.
Table 8 Methods and their applicability to different types of plant (Bullock, 1996)
Key: * always applicable, ? sometimes applicable, no symbol indicates that the method is never applicable to that plant type.
Monitoring scales and techniques
Trees Shrubs Grasses Bryophytes Fungi and lichen
Total counts ? ? ?
Visual estimates * * * * *
Frame quadrats ? ? * * *
Transects * * * ? ?
Point quadrats * *
Harvesting ? ? * ? ?
Plotless sampling * ? ?
Marking and mapping
* * * ? ?
Vegetation mapping * * *