Research into Arable Flowers
The Northmoor Trust has been at the forefront of work with rare and declining wild flowers associated with arable fields since 1995.
Work was initiated following concern, raised by conservationists and botanists, that many once common flowers, such as Cornflower (Centaurea cyanus) and Corn Buttercup (Ranunculus arvensis), had declined dramatically during recent decades. It was apparent that published accounts of their distribution and abundance were woefully out of date and that little was known about the current situation. In an era when the BAP (Biodiversity Action Plan) process is working to restore many habitats and species, it is particularly important that we identify areas where key and declining species can still be found. In this way conservation resources can be targeted more efficiently. There was a clear need to assess the current status of arable plants across Oxfordshire and the rest of Britain. In response to this need for information a programme of research funded by the Northmoor Trust, English Nature and Buckinghamshire County Council has been running for several years.
In 1996, the Northmoor Trust began an on-going field-by-field survey of the arable flowers of the Oxford Heights and Chilterns, to determine their current status and distribution within these areas once renowned for the diversity of their arable flora. A second research project was undertaken in 1997 to assess the long term Changes in Arable Flora since the 1960s. A frequently asked question is whether organic farms provided suitable conditions for rare arable flowers that have largely disappeared from conventional farms. A third study, comparing the Arable Flora of Organic Farms with that of conventional farms ran during 1998 and 1999. The Northmoor Trust has also set up a field study to investigate the life history of Mousetail (Myosurus minimus), a tiny plant that grows naturally on our farmland.
The ultimate goal of all our arable plant work is to conserve Britain's rare arable flora. Farmers with rare arable plants on their land have been invited to consider the Countryside Stewardship Scheme, or to incorporate arable flower conservation into their FWAG Whole Farm Plans. An obvious next step for the project is to find out whether rare arable flowers are benefiting from these conservation initiatives. This is an area of research that the Trust is keen to be involved in.
Arable flowers of the Oxford Heights and the Chilterns
In 1995, the Rare Arable Flora Group identified a need to assess the current status and distribution of rare arable plants in Oxfordshire. A list of 51 'target rare arable flowers', known to have occurred in the county, including both nationally rare species and more widespread, but characteristic arable species, was compiled. It was decided to target areas that were known to have been rich in arable flowers in the past and to survey them thoroughly, field-by-field. The two areas chosen were the Oxford Heights, a low limestone ridge that stretches some miles east and west of Oxford city, and the Chiltern Hills.
With permission from farmers and landowners, 290 fields (13 parishes) on the Oxford Heights (1996-98) and 349 fields (12 parishes) on the Chilterns (1999-2000) have been surveyed. 26 target rare arable flowers have been recorded during the surveys. On the sandy soils of the Oxford Heights, Prickly Poppy (Papaver argemone), was found to be relatively common. In the Chilterns the Nationally Scarce Dense-flowered Fumitory (Fumaria densiflora), was frequent on chalky soils. Species widespread in both areas include the Fluellens (Kickxia spuria, K. elatine). However, the majority of the species were found at very few sites. For instance, both Weasel's-snout (Misopates orontium) and Red Hemp-nettle (Galeopsis angustifolia) were only recorded from single fields from the 640 fields surveyed. Surviving arable flowers were typically very much confined to field edges, often in low numbers, and only just holding on. Sadly, 25 species on the Target List were not found at all.
The survey found that soil type was the most important factor in determining the arable plant species composition. The well-drained sandy soils of the Oxford Heights and the chalky soils of the Chilterns supported the most rare species. Another very important factor was the sowing time - crops sown during the spring months were more flower-rich than the winter-sown fields. This is because some plants, like weasel's-snout (Misopates orontium), can only germinate in spring-sown fields.
Changes in arable flora since the 1960s
The field-by-field surveys of the Oxford Heights and Chilterns provide information on the current status and distribution of rare species, but it lacks long-term data with which to quantify any changes. To address this need, a second research project was undertaken to compare current arable weed communities with an existing baseline data set collected more than 30 years ago.
In the early 1960s, 156 arable fields were surveyed as part of a research project undertaken by Dr Quentin Kay at Oxford University. The sites were scattered from the Wessex Downs and Chilterns in the south, to the Greater Cotswolds in the north. In 1997 all fields which were still under arable cultivation were resurveyed. We found that one hundred fields (65% of the original sites) were still in arable. We looked at the presence or absence of individual weed species at each of these sites, to give us some idea of how the occurrence of weeds has changed between the two surveys.
Some species, such as Corn Chamomile (Anthemis arvensis), Red Hemp-nettle (Galeopsis angustifolia), and Night-flowering Catchfly (Silene noctiflora), had apparently disappeared. However, many rarer species were still persisting, although much reduced in abundance. Surprisingly, a few rare species, eg Shepherds Needle (Scandix pecten-veneris), were found on more sites in 1997 than in the 1960's.
Several problem weeds have apparently colonised new areas or increased markedly in abundance over the past 30 years. Good examples are Black Grass (Alopecurus myosuroides), Fool's Parsley (Aethusa cynapium), Barren Brome (Anisantha sterilis) and Prickly Lettuce (Lactuca serriola). Black Grass is currently the worst weed-enemy of many farmers. Our data show how this species has spread from the clay soils, where it was restricted to a few sites in the 1960s, to the chalky downland soils, where it was formerly unrecorded. Most of these problem weeds prosper because of the increased nitrogen input from modern, intensive farming techniques.
We had expected to see large changes in the abundance and distribution of arable plants because of the extent to which farming practices have changed over the past 30-40 years. Surprisingly, many of the rarer species were found in as many fields in 1997 as they were in the 1960s. However, it is apparent that the abundance of these species has decreased and instead of a healthy maintenance of populations, we may be actually witnessing a gradual depletion of the seed bank.
This study suggests that many of the rarer species are still present in the seed bank. Clearly, it is not too late for conservation measures, which would save them from extinction, to be implemented. Many economically viable alternatives exist to aid European farmers in the integration of wildlife conservation within a profitable farming business. Bearing in mind the likelihood that the seed-bank reserves of the rarer arable plant species have declined to critically low levels, conservation action should be rapid to protect biodiversity and prevent further extinctions.
The arable flora of organic farms
A third study, which ran during 1998 and 1999, was a comparison of the arable flora of organic and conventional farms. Organic farmers do not use synthetic pesticides but they do have other ways of controlling weeds such as incorporating grass leys into the rotations, using a wider range of crops and cultivation times, and uprooting weeds using spring-tine weeders or inter-row hoes. We aimed to record all the plant species in arable fields on organic and neighbouring conventional farm in order to find out how species richness, composition and abundance were affected by the two systems. Of particular interest was the question of whether organic farms provided suitable conditions for rare arable flower species which have declined so much in recent years in the countryside as a whole.
Over the two years we visited a total of 38 pairs of fields within eleven organic and eleven conventional farms throughout Oxfordshire, Berkshire, Wiltshire and Gloucestershire. Each organic and conventional field pair was matched to have the same crop type, and were of roughly the same size and soil type. Plant species and abundance in each field were recorded. The organic arable fields were found to provide a habitat for many rare and declining arable flowers which were not recorded from neighbouring conventional fields at all. These included four species listed on the UK Biodiversity Action Plan: Red Hemp-nettle (Galeopsis angustifolia), Corn Gromwell (Lithospermum arvense), Corn Buttercup (Ranunculus arvensis) and Narrow-fruited Cornsalad (Valerianella dentata). Other examples are Prickly Poppy (Papaver argemone) and Rough Poppy (Papaver hybridum). Many of these species are known to be sensitive to some of the commonly used herbicides. Therefore, the results of this study suggest that many rare or declining arable flowers that cannot tolerate herbicides are able to tolerate the weed control measures on organic farms.
Ecology of Mousetail (Myosurus minimus)
Recent work both in Britain and the Netherlands has suggested that some rare arable plants do not have the competitive ability to survive within conservation headlands sown with a well-fertilised modern cereal crop. The tiny annual Mousetail (Myosurus minimus) grows naturally on the Northmoor Trust's farmland, but seems to be faring no better under conservation headlands than under former conventional management.
In the autumn of 1998, we set up a field study to investigate the life history of Mousetail in one of our conservation headlands. We were interested in finding out when and how well Mousetail seeds germinated within the crop, and when individuals flowered and set seed.
Seeds were sown in the headland in October 1998, soon after the winter wheat crop had been drilled. There were a total of 125 seeds, 25 in each of five plots positioned randomly along the headland. The plots were re-visited regularly until the plants had completed their life-cycle. From the total of 125 seeds sown, 28 (23 %) germinated. Most seed germinated between mid December and mid February and the seedlings grew rapidly. About half of these (54 %) survived to flower and produce fruits. Over half of these plants were flowering by mid April and the rest continued through May before the crop became too dense. Most plants had begun to set fruit in May and most had ripe seed by mid July.
Most individuals were tiny (under 2 cm in height), even when flowering, and it was only with careful searching that we were able to relocate individuals within the plots. It seems likely that mousetail is under-recorded in farmland surveys, not only because it is so small and inconspicuous, but also because it flowers early in the season, before many surveys take place.
Further work into the ecology of Mousetail on our land is currently being undertaken by a Ph.D. student.
