Aquatic Planting Project

Introduction

Selection of Planting Sites

Planting Sites

Water crowfoot growth in the Bevern Stream

2009

The introduction of Ranunculus sp. into the middle reaches of the Bevern Stream was commenced in 2000. This has proved to be one of the most successful sites in the project, to such an extent that we have periodically thinned the plants. The harvested material is used for planting at new locations, or allowed to drift down stream to take root where it will.

New growths have been noted in some sections of the stream where we have not intervened, showing that natural propagation is now taking place.

Water crowfoot introduced to the River Uck

Ranunculus has also been successfully introduced to the River Uck at Uckfield and is now well established.

Introducing submerged flora to lotic waters is not an easy exercise, particularly in the Ouse catchment where we experience severe spates in wet weather due to a sudden influx of water from urban run off and land drains. Probably only about one in ten of our introduced plants survive long enough to become well established and despite our efforts to plant other species such as Callitriche, Ranunculus seems to be the only plant tolerant to the conditions encountered. However, other species such as Callitriche and

Demoiselle ovipositing on water crowfoot – Bevern Stream.

Sparganium emersum are naturally abundant in some locations where the conditions are more benign. We will continue to experiment with increasing the biodiversity. Where Ranunculus has been successfully introduced, it has the effect of stabilising the stream bed, which in due course may provide more suitable conditions for successful establishment of such species as Callitriche. We will continue with our endeavours.

There is no doubt that our project has been beneficial to the invertebrate population. Our monitoring of the planted sites has shown a steady improvement in the BMWP and ASPT scores over the last few years, despite the occasional dips due to poor water quality at times.

Ranunculus Fluitan flourishing after the drought of 2003

Fig.3

2004

The damage to the submerged vegetation in the stream caused by the prolonged drought conditions of the 2003 summer was not as devastating as it appeared. In the late spring of 2004 most of the species were seen to regenerate with the maintained rate of flow. There is now no doubt that Ranunculus fluitans is permanently established in the watercourse and scattered colonies of Callitriche and Sparganium emersum are also present.

The project has proved successful in adding to the biodiversity of the stream and this work will be continued on other streams in the catchment.
(See Fig.3)

Fig.2

2003

2003 was not a good year for this project. With very high summer temperatures and prolonged drought conditions from the beginning of May to the end of September, water levels in the stream were extremely low. Many riffle areas supporting growths of Ranunculus became almost stagnant pools. Without agitation from a robust flow, algal deposits covered the vegetation with a slimy brown film, inhibiting photosynthesis and growth mechanisms. (See fig.2).

Some planting of Ranunculus at other sites was undertaken in the spring, but few if any of these survived. The situation will be reviewed in the spring of 2004.

Fig.1

2002

Shortly after this planting there was a moderate spell of rain with consequent increase in current volume and velocity. An inspection of the site indicated that none of the planted material had survived. Experience has shown that establishing new plant communities in this stream is difficult with the exception of Ranunculus fluitans. This plant takes root quickly and having done so grows rapidly. It is resistant to fragmentation from increased current velocity and turbulence and even if the emergent growth is denuded, new growth takes place from the rootstock. The roots of this plant appear to stabilize the streambed creating areas resistant to erosion.

The original plantings in 2000 were now large enough to divide and provide samples for further distribution, with likelihood of successful establishment. A comprehensive programme of distribution has been undertaken throughout the section of the stream from its confluence with Plumpton Mill Stream to Clapper's Bridge. There is now no doubt that this species should survive and flourish.

During the spring and summer of 2002 further attempts have been made to introduce Callitriche spp. This plant can be found in certain places on the River Ouse and is often abundant in adjacent ditches. However, it is relatively fragile and susceptible to fragmentation. It appears to take longer to root than R. fluitans, does not grow as quickly and its root systems do not significantly contribute to the stability of the substrate. Heavy rainfall during the spring and early summer of 2002 contributed to many failures. Experience has shown that selected sites in proximity to established Ranunculus fluitans are more likely to succeed. (See fig. 1). It remains to be seen if these survive the winter spates of 2002/03.

2001

Attention was now turned to obtaining more diverse species to continue the project. In the previous year (2000), growths of Myriophyllum and other species were identified in a tributary of the Ouse at Walstead, and the riparian owner was willing to donate some samples. However, an inspection of the stream in July 2001 showed it to be completely devoid of sub–aquatic vegetation. A substantial amount of housing development has taken place at the headwaters of this stream near Haywards Heath, and the riparian owner said that there were now more frequent and severe spates due to surface water runoff which were scouring the bed of the stream on a regular basis, denuding it of resident vegetation.