Positive impacts of Short Rotation Willow Coppice (SRWC) on the environment:

SRWC plantations require few agricultural inputs once they have been established. Thus, the risk of ground water contamination by agro-chemical is very low. The need to use insecticides to control pest and disease attacks in SRWC can be minimised by careful plantation design and varietal selection. Herbicide application is restricted to the establishment phase and once a good stand of crop cover is attained in the second or third year, weed interference is usually too minimal to warrant herbicide application. It may also be possible to reduce the amount of chemical weed control required for SRWC through use of mulch materials or cover crops (Lowthe-Thomas, 2003). Willow coppice requires low levels of nitrogen. However, upland soils in Wales are acidic and nutrient poor. Studies of growing willow in the uplands have shown the need for fertilisers in order to obtain economic yields at some sites.

SRC willows have well developed mechanisms to recycle mineral nutrients through deep root systems. It takes longer for nitrate to be leached out of this deeper root zone. Therefore, SRWC could be used effectively in reducing nitrate concentrations in rivers receiving drainage from agricultural land, particularly if they are located at the lower end of the slope in intensively managed fields. The willow roots also hold the soil together reducing the risks of soil erosion in adverse weather and during machinery use. These nutrient and structural improvements of the soil result in increased soil invertebrate fauna and fungi which add to the ecological value of a site.

Negative impacts of SRWC on the environment:

SRC willow may grow up to 8m in height, and their rootstocks stay in the ground for a number of years. Their rapid expansion in an area is likely to make a visual impact on the rural landscape. Site selection and planning for biomass crops should, therefore, take into account public foot path access, landscape aesthetics, local archaeology and hydrology. It is, therefore, important to incorporate forest design principles at the early stages of the planning as these may restrict the size of the area to be planted.

Although SRC willow generally require low-input agrochemicals, it is important that necessary precautions are taken when applying fertilisers in nutrient poor soils; or herbicides in the establishment phase; or pesticides during a pest outbreak. Nitrate leaching has been recorded after green cover removal in the land preparation phase; during the establishment year where nitrogen has been applied as fertiliser; and after final removal of the crop. It is, therefore, important that no fertiliser is applied during the establishment year, i.e. after planting and before cutback.

Positive impacts on the ecology:

Willow has been found to increase the biodiversity of an area over previous land uses, including sheep grazed pastures and arable crops where a low biodiversity predominates. Ecological studies of the large areas of SRWC planted in Yorkshire for the ARBRE project clearly demonstrated that willow plantations never displace species from an area and that the overall biodiversity, including ground vegetation, birds, butterflies and invertebrates, is improved (Rich and Sage, 2001).

Mammals: A minimum of 10 species have been observed in SRWC, including the Brown Hare, Stoat, Mice, Vole, Shrew, Fox and Rabbit. These include important food resources for larger carnivores.

Flora: 151 species of plant have been recorded growing in SRWC at sites across in England. These provide, both directly and indirectly, food for butterflies and many other insects and their predators. This diversity of ground flora is also important in regulating weed control by providing competition for resources and preventing domination of individual plant species. Floral diversity also increases the habitat complexity which will encourage a wider diversity of beneficial predatory invertebrates important for controlling pest species.

Birds: Due to the structural complexity of willow and the difference in morphology of the many varieties, at least 32 bird species have been recorded in SRWC. Arboreal species such as Tits and Warblers, ‘skulking’ species such as Wren and Robin, and migrant species also utilise the willow coppice. In west Wales, preliminary results from a study (by Llysdinam’s Wales Biomass Centre and IGER) using mist nets to evaluate the avian biodiversity of SRC recorded 14 species of birds within the cropped areas of first year SRC; and avifauna flocks of reed buntings (Emberiza schoeniclus) and finches were also observed.

Invertebrates: At least three times the number of plant-eating species spends part of their life cycle in the canopy of SRWC compared to conventionally grown barley and wheat (Sage & Tucker, 1998). Over 135 invertebrate species have been found in the canopies of willow, and almost as many ground dwelling and subterranean species have also been recorded. Between 70-80% of all of these species were found to be non-pest species and many of which were beneficial to the crop by predating on pests and therefore acting as a natural control.

Preliminary results from Welsh upland studies of SRWC have been encouraging and support the more general findings presented above. Evidence for upland Wales agrees with the lowland conclusions that the beneficial impacts of planting SRC greatly outweigh any negative ones and that these benefits can be enhanced through careful plantation design and sensitive management practices.

Negative impacts on the ecology:

The practice of growing SRC willow in monocultures, i.e. block planting of single varieties, poses high risk to rust as well as willow leaf beetle damage depending on the chosen variety. This could potentially lead to a dominance of a SRC willow habitat by a single pest species. Moreover, the spraying of crops with inappropriate insecticides can lead to non-target and beneficial insect damage, since most insecticides are not specific to their targets. However, in this case it is important to remember that planting guidelines recommend planting a thorough mixture of varieties and if done appropriately can prevent these problems.

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Lowthe-Thomas SC. Ground cover management for short rotation willow coppice in the uplands of mid-Wales. PhD Thesis. Cardiff: University of Wales (Cardiff University); 2003.

Rich TJ, Sage RB, Moore N, Robertson P, Aegerger J, Bishop J. ARBRE monitoring – ecology of short rotation coppice plantations. ETSU B/U1/00627/REP, DTI/Pub URN/ 01/768; 2001.

Sage R, Tucker K. Integrated crop management of SRC plantations to maximise crop value, wildlife benefits and other added value opportunities. ETSU B/W2/00400/REP; 1998.