Notes from the National Botanic Gardens, Dublin

Strelitzia reginae. Source: Jon Fern, 2009

The National Botanic Gardens are situated in Glasnevin, Dublin, and were established in 1795 by the Royal Dublin Society. The Gardens specialise in botany, science, horticulture and education. Glasnevin saw the introduction of many exotic plants from foreign countries, and a number of cultivars were created. Since 1878, the National Botanic Gardens has been a public institution. As such, it is now managed by the Office of Public Works. With partners all over the world, The Gardens work in key areas of conservation. Plants are tended and in some cases rescued. The Herbarium now holds more than 17 000 species from around the globe.

The National Herbarium is a comprehensive catalogue of all the species of flora in Ireland. In total, there are 750 000 species of indigenous plants on file. Non-native species, including invasive aliens, are being recorded all the time, so the National Herbarium is continually growing. The worldwlide collection preserved at Glasnevin covers species from areas as diverse as rainforests, deserts, marshlands, mountains and grasslands. Many of the scientists stationed at the National Botanic Gardens are involved in overseas work and have their own personal projects.

The dried plants are kept in the herbarium, which has two main sections: a series of compactors hold the world herbarium, while  the Irish collection is housed in a series of cabinets. There are 75 million specimens in total at the herbarium, of which 80,000 are Irish specimens. The Irish herbarium is the most important collection at the National Botanic Gardens since it is a record of all Irish flora. The world herbarium is incomplete and consists of collections of interest to various botanists who made studies in different locations around the globe. The Irish collection is considered to be complete, however, in that all species currently known to exist in Ireland are represented. Naturalised plants are being added, however, and so the collection is continuing to grow. There have been no major new species found in recent years, but it is believed by the curators that they exist. Numerous collectors have made donations to the museum and these are kept in their own section.

Two Genera of Note

The genus Platycerium contains around eighteen fern species in Family Polypodiaceae. These ferns are known a Stagshorn or Elkhorn ferns due to their antler-like appearance. The genus is epiphytic and native to temperate and tropical regions of South America, Australia, Southeast Asia, Africa and New Guinea. Platycerium sporophytes have tufted roots growing from a short rhizome bearing basal and fertile fronds. Basal fronds are sterile; shield (or kidney) shaped and laminate against the host tree, protecting the roots of the fern from desiccation or mechanical damage.

The uppermost margin of most Platycerium species resembles an open crown of lobes adapted to catching falling forest detritus and water. Fertile fronds have spores on their underside, projecting from the rhizome. The spores are clustered in sporangia positioned either on the lobes or between frond lobes.

Some species of the Platycerium genus have one rhizome. Other species grow in colonies with rhizomes branching or new rhizomes forming from root tips. In some conditions spores will germinate on neighbouring trees. Platycerium gametophytes are a small chordate thallus. 
Platycerium have evolved into four groups. Some Platycerium are adapted to arid conditions; the drought-tolerating mechanism Crassulacean Acid Metabolism has been reported particularly for P. veitchii.

Platycerium superbum can be found in cultivation, especially in tropical gardens. Stagshorns are propagated by spores on the underside of fertile fronds. A mature Stagshorn can grow more than a meter wide.

Sarracenia is another interesting genus that may be observed at the National Botanic Gardens. Otherwise known as Pitcher plants, species of this genus come from North America. All eight species of this genus are threatened in the wild. They require good light and tend to sit in 2 – 3 cm of water during the growing season. Like the Venus Fly Trap, the Pitcher plants are carnivorous. A trail of nectar lures insects within the ‘pitcher’ where the insect then falls in and is digested. Its presence in Ireland for over 100 years may qualify the Pitcher plant for naturalised status. It is not considered to be invasive. (Daragh Lupton, pers. comm.)

References

Botany: Basic Concepts in Plant Biology, Hufford, 1978

Trees of Britain and Europe, Aas and Riedmiller, 1994

Brief Geological and Biological Histories of the Killarney Valley

Ilex aquifolium woodland in the Killarney Valley © Jon Fern 2011

Part One: A Brief Geological History, Incorporating the Most Recent Period of Glaciation, and its Impact on the Killarney Valley and Environs

The Killarney Valley is one of the Republic of Ireland's greatest natural assets. It also has a fascinating geological history. The main contributing rock types in the geology of the Killarney Valley are Old Red Sandstone from the Devonian Age (395-345 million years old) in the south and west of the Park, and Carboniferous Limestone (345-295 million years old) in the north. These two rock types meet at an ancient geological boundary within the Park, part of which runs beneath Lough Leane (Carruthers, 1998).

Beginning with the Pleistocene Age, which began around 2 million years ago, and lasting until around 16,000 years ago, the last major period of glaciation helped to shape the bedrock of the Killarney Valley. Ice eroded the bedrock and deposited eroded material as glacial tills, forming moraines or mounds of mixed gravel and stones, which would later become hills. The massive Templenoe glacier carved out many of the mountain features we see today, including Moll’s Gap (Quirke, 2001). The Gap of Dunloe was formed when an area of ice moved across a ridge, carving out the valley beyond (Mitchell et al., 2007). Mitchell et al. (2007) also point to the striated rocks around the Upper Lake as evidence of the erosion from the ice.

Carruthers (1998) identifies several cold stages affecting Kerry, interspersed with warmer interglacial periods. During the Pleistocene Epoch, massive ice sheets formed which caused the earth’s crust to sag; during the interglacial periods, the resultant upwarping of the ground sometimes left beaches higher than sea level; an example of this is found at Ballydavid on the Dingle peninsula. These interglacial periods deposited organic material as well as inorganic tills; peat and semi-organic silts may be found within the low cliffs around Spa, near Tralee bay. Pollen from these deposits included grains from species including fir and rhododendron. Uranium-thorium disequilibrium dating determined the age of these deposits to be between 123 000 and 114 000 years BP (Carruthers, T., 1990).

Since each of the glaciers that affected Killarney likely removed the traces of those previous, the most noticeable effects of glaciation in the area come from the most recent glaciation event (Quirke, 2001). This lasted from 115 000 years ago to 10 000 years ago. Freeze-thaw action shattered mountain peaks almost continuously. Mountains of Old Red Sandstone particularly were eroded by layers of shattered rock. Snow accumulated as temperatures plummeted, and masses of ice formed. They thickened and became glaciers.

Quirke (2001) describes the Templenoe glacier as being instrumental to the formation of the Killarney landscape. More so than the mountain ice on the Macgillycuddys Reeks, the ice cap carved the Earth into now-familiar formations: north-moving tongues of ice split from the ice cap and met the Reeks – the ice split further, with some deepening Ballaghbeama Pass, down the Caragh River valley, around Caragh Lake and on towards Dingle Bay (with Cromane Point being part of the terminal moraine from this ice flow). More ice moved east past Mangerton. It also forced its way through what is now Moll’s Gap and the Gap of Dunloe. These are called glacial breaches. The ice moved through Owenreagh and Gearhameen in the lowlands, but it also flowed over higher ground as it thickened. These effects can be seen in the smoothness and width of the valley. Glacially scoured lakes such as Upper Lake are evident, as are smoothed outcrops called roch moutonnées, such as Eagle’s Nest overlooking Glaisín na Marbh.

The ice flowed north of Torc and spread in all directions, over the area containing Lough Leane, Killarney town and River Laune. It met here the glacier pushing through the Gap of Dunloe. Debris carried by the ice was deposited in moraines, the Old Red Sandstone erratic deposited on the limestone bedrock of the Park can be used to determine the direction the ice flowed in (Quirke, 2001). Different types of moraine were created as the ice began to retreat. Terminal moraines were left in corries among the Reeks as the last re-advancing of the ice subsided. As the ice melted, precipitation increased and the limestone dissolved forming cliffs and caves along the Lower and Upper Lakes, and leaving limestone islands. The cracks in the limestone pavement formed. Soil became waterlogged and peat began to build up, and blanket bog accumulated.

Part Two: A Biological History of the Killarney Valley, From the Last Period of Glaciation Onwards

As the warming trend took hold at the end of the last period of glaciation, grasslands appeared (Larner, 1992) and those trees that had survived the ice age began to flourish. These included birch, willow and hazel, and they formed the first new forests (Quirke, 2001; Mitchell et al., 2007), following the juniper that colonised the area immediately after the retreat of the ice (Larner, 1992). Pine spread widely around 9 000 years ago (Mitchell et al., 2007), and oak grew in Killarney 8 000 years ago.

Elm also moved in alongside oak on nutrient-rich soils, leaving the poorer soils for the pines, until a continual cover of trees between 8 500 years ago to 7 000 years ago. Following this period, the climate became conducive to alder colonisation, and with these wetter conditions fen-woods appeared. At around 5 000 years ago, elms declined, possibly due to a disease event (Larner, 1992).

The red deer for which the Killarney National Park is notable can be traced back to 26 000 years ago in Ireland (Ryan, 1998). The earliest evidence for the red deer in Kerry is 4 000 years ago on Ventry Beach. It was the only deer species that co-existed with humans in Ireland until the Normans later introduced the fallow deer, according to Ryan (1998). The other deer species once native (the giant Irish deer, the European elk and the reindeer) had apparently been wiped out before humans arrived. Roe deer were briefly introduced in the 1800s, only to be killed off a few decades later, and sika deer were introduced to Killarney in 1865. The Great Famine served to reduce the herd of red deer significantly (Viney, 2003).

Humans may have been living in Killarney before the last period of glaciation (Quirke, 2001), but it was not until 7 000 years ago that evidence for Mesolithic people living in Ireland exists. Evidence for human habitation in Killarney during the Bronze Age 4 000 years ago has been found at Ross Island, where copper mining took place, and a stone circle can be seen at Lissivigeen. The woodland within the park were cleared several times from the Iron Age onwards, as agriculture increased (Mitchell et al., 2007).

After 4 000 BC, there is evidence that woodland is disturbed in the Killarney National Park area (Quirke, 2001). It is around this time that the Arbutus appears in the pollen data (Viney, 2003), although this may have been from seed migration via birds. Farming increased from 3 000 BC onwards, as shown by pollen data from this period, displaying tree clearance increasing. Some hill bogs still show enclosures from this period, which would have been used to protect livestock from wolves, bears, foxes and other people. Around 2 500 BC, tribal territories were formed and there are mountain cairns in Killarney from this era.

As food supply became steadier, the local population increased, and around 2 000 BC, Killarney saw the beginning of metal working (O’Brien, 2000). This metal working continued throughout the Bronze Age. In the Late Bronze Age, tribal conflicts became common, possibly due to pressure on food sources, when soil fertility began to be problematic. Many hill forts date from this period (Clinton, 2001).

Conflict continued after the Iron Age brought new technologies related to war (Quirke, 2001). There was a resurgence in agriculture around 500 BC, when ploughing became popular (Mitchell et al., 2007). Elm and ash, previously having suffered locally, recovered when arable land declined in the area. Around 400 BC, Roman influence lead to widespread clearing of woodland for intensive farming, despite the fact that the Romans themselves did not invade the country.

According to Mitchell et al. (2007), soils that would have been well-drained with woodland now became increasingly degraded to peaty podzols, a process that had been going on wherever trees were cleared. This now became more widespread, particularly in the uplands. Ploughing practices acted to leach more nutrients from the soil, as sods were continually broken and re-broken. This may have led to the expansion of heathers. Increases in annual rainfall at this time increased the leaching process. Cattle, pigs and sheep were raised for meat, with cattle grazing on grassland that had by now been developed over hundreds of years. Soil degradation and the clearance of woodland led to a decline in plant biodiversity which is borne out by the pollen record. These areas of farmland were never again significantly colonised by woodland.

The pines disappeared around this time (Viney, 2003), and oaks became the prevalent species. A pocket of yew exists, which probably became established around 5 000 years ago (Mitchell, 1990), and similarly shows signs of having been cleared and occupied. The oak woods remained in large part untouched until the 1500s, being exploited for firewood and construction in a more or less manageable way (Larner, 1992). However, during the Elizabethan times, much of this woodland was destroyed to facilitate the passage of English troops through the country. But more so than military destruction, the onslaught of industrialisation denuded Killarney of much of the oak woodland, mainly for timber, charcoal production for iron smelting, barrel-making and boat-building.

The introduction of Rhododendron ponticum in the late 1700s (Viney, 2003), or early 1800s depending on the source, decimated the natural flora of Killarney. By 1969, half the natural woodland had been colonised by the shrub, which is not eaten by anything in the Park, and outshades and outcompetes other plants for light and nutrients. Due to the steady rain that characterises the local climate, most gaps in the woodland become waterlogged, filled with tussocky grass, and cannot nurture acorns. The deer (sika and red) graze continually on saplings, which does little for the regeneration process.

As a result of this denudation, Viney (2003) recognises that the birdlife in Killarney is missing species that are present in Britain, despite being annual passage migrants in Ireland. The loss of habitat may account for the lack of biodiversity, such as the four tits native to Ireland, compared to the seven of Britain, although this could also be due to the differences in climate. For instance, the increased rain (an effect of the retreat of the ice age), may have reduced ground invertebrates upon which small birds such as the chaffinch, wren and goldcrest feed. Heavy grazing by sika deer on brambles and ivy also serves to remove part of their habitat.

However, Killarney is notable for being home to several rare species of butterfly, such as the purple hairstreak, as well as dragonflies, including the downy emerald and the northern emerald. Another invertebrate of note in Killarney is the Kerry slug (Carruthers, 1998). It is conjectured (Viney, 2003) that it was an open-country species that became adapted to tree-cover following the postglacial warming.

The red squirrel thrived in postglacial Scots pine woodland. When this declined, the squirrels adapted to stands of hazel and oak. In medieval times, an export levy was placed on their skins, which suggests it was in abundance (Viney, 2003). However, it was considered extinct in Ireland by the end of the 1700s. It was reintroduced from England in at least ten sites between 1815 and 1876 by early ecologists. However, in 1911, the grey squirrel was introduced. Grey squirrels are better able to digest unripe acorns than the red, which explains their ability to compete so successfully. The red squirrels are more at home in Scots pine, and can feed on the kernels of their cones throughout winter, so the Park is a stronghold for them, with its stands of naturalised conifers.

In conclusion, the trend following the end of glaciation has been towards a warmer, wetter climate, with human pressure on the landscape leading to deforestation and degradation of soil. The denudation of the landscape has been at times amended, such as with the replanting of Tomies and Derricunnihy woods in the 1800s (Quirke, 2001), but more often exacerbated, as with the introduction of R. ponticum. How much of the effect on the biodiversity is due to recolonisation by plants and animals following glaciation, and how much is due to human intervention is debatable; no doubt the special climate of Ireland has a large effect, as does its being an island.

The greatest threat to the biodiversity in Killarney National Park is the spread of Rhododendron ponticum. It remains to be seen whether humans can undo the error they made in encouraging its growth here; however, it looks as though reversing the exponential spread of this shrub will take efforts beyond the economic scope of the Park as it presently stands.

If you are interested in helping to eradicate Rhododendron ponticum from the Killarney National Park, please contact Groundwork at info@groundwork.ie, or visit their website.

References

Bolton, J., (2008). Antiquities of the Ring of Kerry, Bray, Wordwell.

Carruthers, T., (1998). Kerry: A Natural History, Cork, Collins Press.

Clinton, M., (2001). The Souterrains of Ireland, Wicklow, Wordwell.

Feehan, J., O’Donovan, G., (1996). The Bogs of Ireland, Dublin, UCD Environmental Institute.

Larner, J., (1992). The Oakwoods of Killarney, Dublin, The Stationery Office.

Larner, J., (2004). The Ross Island Mining Trail, NPWS.

Mitchell, F., (1990). The history and vegetation dynamics of a yew wood (Taxus baccata L.) in S.W. Ireland. New Phytologist, 115: 573-577.

Mitchell, F., Ryan, M., (2007). Reading the Irish Landscape, Dublin, TownHouse.

O’Brien, W., (2000). Ross Island and the Mining Heritage of Killarney, Galway, National University of Ireland, Galway.

Ryan, S., (1998). The Wild Red Deer of Killarney, Kerry, Mount Eagle Publications.

Quirke, B., (2001). Killarney National Park, A Place to Treasure, Cork, Collins Press.

Viney, M., (2003). Ireland, Belfast, Blackstaff Press.

Comparisons of Irish River Water Quality Indices

Niger Delta. Source: NASA

River and stream quality may be measured by assessing the diversity of macroinvertebrates supported by the water body being surveyed (Sutherland et al., 2006). For this purpose, different biotic indices have been devised. These assign values to different biological parameters, and can sometimes take abiotic factors into account, such as siltation and dissolved oxygen. The main component of aquatic biotic indices is the identification of macroinvertebrates collected from the surveyed water body. These invertebrates act as indicator species, in that their presence and abundance indicate the quality of the water, usually due to the varying sensitivity of individual families, and sometimes individual species, with differences in tolerance to environmental impacts (Dufrene et al., 1997). By assessing the number of families present, each of which are usually assigned a value, and their abundance, the quality of the water body is given a score, indicating its quality.

The Q-value system used by the Irish Environmental Protection Agency was designed by Dr Paul Toner of An Foras Forbartha (later superseded by the EPA) in the early 1970s (Flanagan et al., 1972). An overview of the system is included in the appendices of several annual EPA reports entitled ‘Biological Survey of River Water Quality’, for example Clabby et al. (2004) and Lucey (2009). Since its development, the Q-value system has been the standard biotic index system used by the EPA to monitor the ecological quality of Irish sreams and rivers (Lucey, 2009). The Q-value system was intercalibrated with the European Union’s Ecological Quality Ratios (EQRs) as per the Water Framework Directive (Lucey, 2009). The WFD requires that biotic indices calculated by each Member State with their own systems be converted to a standardised ecological quality ratio (EQR). EQRs are the ratio between the observed and the reference conditions for the water body being surveyed and are expressed as a number between zero and one, with values close to one representing high ecological status values close to zero representing bad ecological status (McGarrigle et al., 2009).

The Biological Monitoring Working Party (BMWP) system is the main biotic index used in the UK and was first devised in 1976 (Hawkes, 1997), and has been updated a number of times, most recently in 2010 (Paisley et al., 2010).

Other indices that exist include the Trent Biotic Index, the Chandler Biotic Index, the Saprobic Index and the Hilsenhoff Biotic Index.

            Both the BMWP and the Q-value system score stream and river quality based on macroinvertebrate identification and weight families by both presence and abundance; both require habitat information, although in the BMWP system this is limited to river microhabitat type: riffles, pools and glides. The main differences between the systems are the numbers of macroinvertebrate families to which scores are assigned (more in the BMWP system), and the scoring scales themselves (narrower in the Q-value system).

Overall, while the Q-value system has the advantage of including more non-invertebrate parameters in its scoring calculations, the range of assessed invertebrates (the main function of both biotic indices) is much narrower in the Q-value system than in the BMWP system. The small number of bands (Q1-Q5) and the room for overlap between them also mean that this system is less accurate than the BMWP system.

A disadvantage of both biotic indices is the effect that sampling effort has on the final scores of surveyed water bodies. For instance, a higher score may be assigned if the sampling period is extended, and a lower score will be the result of reduced sampling times. However, the BMWP system has the advantage that it incorporates the Average Score Per Taxa (ASPT) which may be calculated by dividing the final BMWP score by the number of taxa (Hawkes, 1997).

           Good or moderate water quality may exist where faunal requirements are not met, for instance in cases where the water is either oligotrophic, very hard and calcareous, or where there is significant groundwater input (Lucey, 2009). In these cases, both biotic indices would fail to assign good quality status to water bodies which are of good physic-chemical quality, but that do not support diverse macroinvertebrate communities. Biotic indices that record macroinvertebrates also exclude some keystone species, with Margaritifera margaritifera being an example of an indicator of good water quality.

            Both the BMWP and the Q-value system test the sensitivity of a range of invertebrate species to changes in their environment. However, this is not the only measure of good water quality, since physico-chemical parameters must also be assessed, and biotic indices should not be relied upon as the sole method to test stream and river quality.

References

Ausden, M., Drake, M., (2006). Invertebrates. In: Sutherland, W., ed., (2006). Ecological Census Techniques, 2^nd Edition. Cambridge University Press, Cambridge, pp 214- 249.

Clabby, K., Lucey, J., McGarrigle, M., (2004). Interim Report on the Biological Survey of River Quality, Results of the 2003 Investigations. EPA, Wexford.

Clabby, K., Bradley, C., Lucey, J., McGarrigle, M., (2008). Water Quality in Ireland 2004- 2006. EPA, Wexford.

Chadd, R., (2010). Assessment of Aquatic Invertebrates. Springer, London.

Chalmers, N., Parker, P., (1989). The OU Project Guide: Fieldwork and Statistics for Ecological Projects. Field Studies Council, Shrewsbury.

Dufrene, M., Legendre, P., (1997). Species Assemblages and Indicator Species: the Need for a Flexible Asymmetrical Approach. Ecological Monographs, 67 (3): 345-366.

Flanagan P., Toner P., (1972). The National Survey of Irish Rivers. A Report on Water Quality. An Foras Forbartha, Dublin.

Hawkes, H., (1997). Origin and Development of the Biological Monitoring Working Party score system. Water Research, 32: 964-968.

Kerry County Council, (2010). Killarney Electoral Area Meeting Minutes, 14 April 2010. Kerry County Council, Tralee.

Luby, (2006). Guidelines on Procedures for Assessment and Treatment of Geology, Hydrology and Hydrogeology for National Road Schemes. National Roads Authority, Dublin.

Lucey, J., (2009). Water Quality In Ireland 2007-2008. Key Indicators of the Aquatic Environment. EPA, Dublin.

Mason, C., (2002). Biology of freshwater pollution. Prentice Hall, London.

McCarthy, T., (2007). Regulatory Impact Analysis of the proposed Surface Water Classification Systems including Environmental Quality Standards . EPA, Dublin.

McGarrigle, M., Lucey, J., (2009). Intercalibration Of Ecological Status Of Rivers In Ireland For The Purpose Of The Water Framework Directive. The Royal Irish Academy, 109 (3): 237-246.

Office of the Attorney General, (1998). S.I. No. 258/1998 - Local Government (Water Pollution) Act, 1977 (Water Quality Standards For Phosphorus) Regulations, 1998. The Oireachtas, Dublin.

Paisley, M., Trigg, D., Walley, W., (2010). Revision of the BMWP Score System: Derivation of Present-only and Abundance-related WHPT Scores from Field Data. Environment Agency, Bristol.

Paisley, M., Trigg, D., Walley, W., (2010). Revision of the BMWP Score System: Site Type Variations and Scores for New Taxa. Environment Agency, Bristol.

Quirke, B., (2012). Subject matter expert.

Ross, E., (2011). Subject matter expert.

Schowalter, T., (2006). Insect Ecology, 2^nd Edition. Elsevier, London.

Sutherland, W., ed., (2006). Ecological Census Techniques, 2^nd Edition. Cambridge University Press, Cambridge.