Site Condition Monitoring of river habitats, 2013: River Tweed LEAFPACS vegetation data
NatureScot
Description
LEAFPACS analysis showed that the Teviot, Ettrick and Yarrow were generally at High or Good status throughout and certainly at the ECS (Evaluated Corridor Section) scale. The upper to middle reaches of the Tweed mainstem and Whiteadder also were of High-Good quality but the middle and lower reaches of these rivers and the Blackadder were mostly of only Moderate status.
Due to prolonged low flow conditions in 2013 filamentous algal growth may have been greater than normal. This affects classifications quite significantly, often lowering the status of a site by one class. The same effect applies at the ECS scale. A total of 25 sites out of 80 surveyed were classified at Moderate or (rarely) Poor status, mainly due to high algal cover.If the Algal metric used in the LEAFPACS classification is excluded from the analysis, the classification then relies only on the RMNI metric and the number of taxa or functional groups recorded. Under this scenario, all ECSs were classed at Good or High status and only 5 out of the 80 survey sites were classified below Good status. These 5 sites were distributed widely across the Tweed mainstem, Teviot and Blackadder.
The 2004 and 1981 survey data were integrated and compared against the 2013 data for the closest equivalent sites. Based on a subset of 21 sites on the Tweed mainstem (surveyed on all three occasions), there is no clear evidence that the Tweed itself has become significantly better or worse in terms of quality over the 32-year period.
Geographic Description
River Tweed SAC (including River Tweed Mainstream - Scotland only; Blackadder Water; Ettrick Water; River Teviot; Whiteadder Water; Yarrow Water including Little Yarrow)
Purpose
Site Condition Monitoring is a six-year rolling programme of assessment, against quality standards, of the state of notified features on designated sites. The River Tweed is a designated SAC with the Annex I habitat H3260 ëWater courses of plain to montane levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetationí (otherwise known as ëRivers with Ranunculusí) a primary reason for site selection. The River Tweed represents sub-type 2 in the north-eastern part of its range. It is the most species-rich example, by far, of a river with Ranunculus in Scotland, and is the only site selected for this habitat in Scotland. The river has a high ecological diversity which reflects the mixed geology of the catchment. Stream water-crowfoot (Ranunculus penicillatus ssp. pseudofluitans), a species of southern rivers and streams, here occurs at its most northerly location as does fan-leaved water-crowfoot (R. circinatus), along with river water-crowfoot (R. fluitans), common water-crowfoot (R. aquatilis), pond water-crowfoot (R. peltatus) and a range of hybrids. The Tweed is also the most northerly site for flowering-rush (Butomus umbellatus) (JNCC 2014)
Methods
The monitoring was based upon a common standard method that is used across the four UK country conservation agencies (JNCC, 2016). Field surveys, data analysis and assessments were therefore set against a standard set of attributes, targets and reporting procedures. Aquatic macrophytes were surveyed using the standard LEAFPACS2 methodology (WFD UKTAG, 2014 www.wfduk.org/resources/rivers-macrophytes).
Citation
ECUS 2014. Site Condition Monitoring for Rivers and Streams: River Tweed report. Unpublished report to Scottish Natural Heritage, Edinburgh
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Digitised records
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