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Plant ecological field guide to a neophyte-“Eldorado”
near Locarno, Southern Switzerland
Andreas Gigon, Institute of Integrative Biology
Swiss Federal Institute of Technology ETH Zurich, Switzerland
Trachycarpus fortunei, Chinese Windmill Palm, Chinesische
Hanfpalme, Tessinerpalme, Arecaceae, grows in gardens and
spreads into native forests in Southern Switzerland.
Akebia quinata, Akebia, Schokoladenwein,
Blaugurkenrebe, an evergreen Lardizabalaceae from
East Asia, forms a jungle in a “novel ecosystem” near the confluence of Melezza and Maggia.
and Maggia in Southern Switzerland.
Prunus laurocerasus, Cherry Laurel, Kirschlorbeer, an evergreen Rosaceae from Western Asia and South Eastern Europe grows in gardens and spreads into native forests in Switzerland, here near Ascona.
2 1 Introduction: neophytes, invasives, and archaeophytes The flora of Switzerland (flowering plants and ferns) consists of approximately 3’200 species, of
which at least 550 are neophytes; 45 of them are invasive (Infoflora 2014a). For comparison:
10’000 plant species have been introduced to Switzerland for gardens, agriculture, forestry and aquariums (Weber 2013). For Canton Ticino (Southern Switzerland), Schoenenberger et al. (2014) mention 467 taxa (species and subspecies) of neophytes (in a broad sense), of which ≥ “17 cause damage to biodiversity, economy or health”.
Neophytes (= IAS, invasive alien species of plants, nicht-einheimische verwilderte Pflanzenarten) are plant species mostly from other continents that grow spontaneously outside their natural range after their deliberate or accidental introduction by man after the year 1500 (“discovery” of America in 1492). Approximately 70-80 % of the neophytes of Switzerland were introduced as ornamentals, and some for agricultural or forestry purposes. Accidental introductions occurred with seeds and packing or other imported material.
Invasive neophytes are neophytes that spread very effectively, are very competitive and often they affect or damage human health and/or the local biodiversity and/or agriculture, forestry or infrastructure (roads, buildings etc.). 40 invasive neophytes are on the Swiss Black List (Schwarze Liste 2014a of Infoflora.ch) of the species whose stands and spread should be controlled (= bekämpft), 17 are on the Watch List (Beobachtungsliste, Warnliste) of the species that might cause problems in the future and that thus must be kept an eye upon and, if necessary, must be controlled (Infoflora 2014a). NB: In this terminology not all IAS are invasive in the sense just described. Of course, there exist also invasive indigenous species, e.g. Phragmites australis (Reed, Schilf) in wetlands and Pteridium aquilinum (Bracken, Adlerfarn) in dry pastures in Southern Switzerland.
Neophytes often have ecological characteristics of weeds: large seed production, efficient dispersal (see pages 9-12) and establishment, vegetative propagation etc. Many are dispersed with garden waste.
The enemy release hypothesis (ERH) postulates that they can establish successfully because, in the new environment, there are no pests or diseases that “decimate” them. According to the EICA hypothesis (evolution of increased competitive ability), in some neophytes, there may even be an evolution of new characteristics that increase their competitivity.
Neophytes often establish in disturbed habitats like fallow land (Brachland), gravel pits, alluvial sites, roadsides etc. Some establish even in the natural vegetation! Climate change will probably favour many neophytes because they mostly originate from warmer climates.
In the future even more neophytes will occur because of the lag time in their (massive) spreading. Lag time is the phenomenon that several decades pass by between the first appearance of a neophyte (or neozoon) in a region and its (massive) spreading (Crooks and Soulé 1999).
Archaeophytes are plant species (in Switzerland mostly from the Mediterranean region) that were deliberately or accidentally introduced by man before the year 1500 and now grow spontaneously outside their natural range. Archaeophytes are considered members of the indigenous flora!
Many agricultural “weeds” like Papaver rhoeas (Corn poppy, Klatschmohn) and Matricaria chamomilla (Chamomile, Echte Kamille) as well several grasslands species (e.g. Symphytum officinale, Common Comfrey, Wallwurz) and even tree species belong to this group, e.g. Castanea sativa (Sweet Chestnut, Edelkastanie), introduced to Switzerland by the Romans.
The plant names in this guide are according to Lauber et al. (2012), ordered ±alphabetically in the lists; the their photographs are shown on pages 9-12.
3 2 The field trip to the neophyte species The region of Locarno was chosen for this field trip because here a very large number of neophytes occurs. Many of them belong to the interesting groups of laurophyllous trees and shrubs (see below and ch. 3).
The starting point (1) is the village of Solduno (225 m), 2 km west of Locarno. On a narrow path on the very steep south slope (2) we climb up 175 m to Monti della Trinità (3) and then descend on another path back to Solduno. We cross the river Maggia and continue 3 km upstream (4), then 1 km along the river Melezza, which we cross on a small bridge and reach a forest at Saleggi (5). We continue 1 km to Tegna or Ponte Brolla where we take the train back to Locarno.
The soils in Solduno are acidic, but in the village also calcareous and locally nutrient rich soils occur.
On the south slopes above the village we have acidic brown earths or bare acidic rock. Along the rivers acidic brown earths or mostly acidic alluvial material.
The climate is mild and relatively dry in winter, and warm and wet from May to October (details in ch. 3). This so called Insubrian climate occurs only in a small (insular) region around Lake Maggiore and Lake Lugano (up to 500-600 m). It differs from the (sub)mediterranean climate because the latter has dry hot summers and fires that occur every 15-30 years, as a natural ecological factor.
The Insubrians were a pre-roman celtic population in the region.
Stop 1: In the village of Solduno we find many neophytes “escaped” from gardens: forbs (Kräuter):
Artemisia verlotiorum, Conyza canadensis, C. sumatrensis, Erigeron annuus, E. karvinskianus, Mirabilis jalapa, Oxalis stricta O. articulata (pink) and Solidago gigantea, as well as Agave americana and Opuntia spec. Shrubs: Buddleja davidii and Hibiscus syriacus.
Stop 2: Forest above Solduno (Sentiero alle Coste), an “Eldorado” (see ch. 3) with many additional
Evergreen laurophyllous trees and shrubs: Cinnamomum glanduliferum, Eleagnus pungens, Laurus nobilis, Ligustrum lucidum, Prunus laurocerasus, Trachycarpus fortunei (= Chinese Windmill Palm, Chinesische Hanfpalme, “Tessinerpalme”), and the liana Lonicera japonica.
Deciduous trees and shrubs: Acacia dealbata, Ailanthus altissima, Buddleja davidii, Robinia pseudoacacia.
Perennial forbs (mehrjährige Stauden): Duchesnea indica, Erigeron karvinskianus, Phytolacca americana, Reynoutria japonica (= Fallopia japonica = Polygonum cuspidatum).
The evergreen East Asian fern Cyrtomium fortunei.
Annuals: Commelina communis (also perennial), Conyza canadensis, C. sumatrensis, Erigeron annuus, Impatiens balfourii, I. parviflora, etc.
On Castanea sativa, Sweet chestnut, Edelkastanie (an archaeophyte introduced by the Romans) the galls of the Chinese neozoon Dryocosmus kuriphilus (Chestnut Gall Wasp, Edelkastanien-Gallwespe) attract the attention. Many old trees show symptoms of the East-Asian neomycete Cryphonectria parasitica (Endothia p., Chestnut blight or cancer, Kastanien-Rindenkrebs). (Details see ch. 5) (Furthermore, some indigenous trees were planted for afforestation and erosion control.) Stop 3: On Monti delle Trinità (sentiero del Tuna) the following additional neophytes are found, e.g.
Cotoneaster horizontalis, Hemerocallis fulva, and the climbers/lianas Partenocissus spp, Pueraria lobata (Kudzu) and Wisteria sinensis (Glyzinie); they climb up to 15 m on Robinia, Trachycarpus and other trees. P. lobata, a deciduous ornamental Fabaceae from SE Asia, is one of the fastest growing species of Switzerland (≤ 26 cm/day and ≤ 11m/year). It can cover large areas (a stand of ≤ 3’600 m2 near Lugano) with a mat 2.5 m thick (Gigon et al. 2014). In the USA, Kudzuland covers 3 Mio. ha.
Five “reasons” for the enormous shoot growth of Pueraria lobata (Kudzu)?
Stop 4: Along the river Maggia not many additional neophytes except for Bambusa or Phyllostachys (a Bamboo) and the deciduous shrub Prunus serotina (Mountain Black Cherry, Amerikanische Traubenkirsche), Impatiens balfourii (Balfour's touch-me-not, Balfours Springkraut), Helianthus tuberosus (“Jerusalem” artichoke, Topinambur). Impressive spread of Reynoutria japonica!
A European invasive in the NE USA is Alliaria petiolata (Garlic Mustard, Knoblauchhederich). There is outcompetes the native spring wildflowers (≥ 5 spp) and is toxic for the larvae of three species of Pieridae-butterflies (Whites,Weisslinge). www.nps.gov/plants/alien/pubs/midatlantic/alpe.htm In Europe, 69 insect herbivores and 7 fungi are associated with the Alliaria, but not so in the USA.
In the Pinus sylvestris trees (Scots Pine, Waldföhre) the nests of Thaumetopoea pityocampa (Pine Processionary Moth, Pinien-Prozessionsspinner) attract our attention. The caterpillars of this small butterfly form these nests and migrate in processions of 5-30 individuals (each ≤ 5 cm long) in search of new food plants. The hairs of the caterpillars can cause allergies in humans and animals.
Stop 5: In the forest at Saleggi near the confluence of Maggia and Melezza one is impressed by the dominance of many now already well-known neophytes, so that this forest might be called a “novel ecosystem”. “New” neophytes are the evergreen jungle liana Akebia quinata (Lardizabalaceae) and the rare small tree Brussonetia papyrifera (Moraceae), both from East Asia, as well as Quercus rubra and Oenothera biennis (Evening Primrose, Nachtkerze), both from N America.
5 3 Why are the regions of Lake Maggiore (Locarno) and Lake Lugano an “Eldorado” for neophytes?
There are at least five partially interrelated factors leading to this “Eldorado” for neophytes. In fact, according to Infoflora (2014a) about 120 neophyte species occur near Locarno, 16 of which have become invasive (numbers without crop species and herbarium and literature data).
Factor nr 1: The early touristic history of the region Since the 18th century but particularly in the 1880ies the region around these Lakes became an important tourist resort for the wealthy classes of Northern Europe and Italy, because it can easily be reached, has a beautiful landscape, and a climate that is mild in winter (for the North-Europeans), and not very hot in summer (for the Italians). Details about the climate see below). Hotels and villas were built, and in the parks and gardens exotic plant species (particularly evergreens) from all over the world were planted (also as a status symbol) – the basis for the present-day neophytes.
Factor nr 2: The Insubrian climate The Insubrian climate is characterized by a warm and wet summer and a mild, relatively dry winter (details above in ch. 2, and below in ch. “Climate change”). It occurs in a ± insular region around Lakes Maggiore, Lugano and Como (up to 500-600 m) and is very suitable for exotic species.
Factor nr 3: The discrepancy between the present day natural vegetation and the vegetation of the Insubrian climate The natural vegetation on acidic well-drained soils near Lake Maggiore and Lake Lugano (up to 500m) consists of forests with Oak (Eiche, Quercus petraea and Q. robur), Birch (Birken, Betula pendula), Ash (Esche, Fraxinus excelsior), and other deciduous tree species. These forests are quite similar to forests in much colder regions, e.g. North of the Alps. (The widespread deciduous Sweet Chestnut, Edelkastanie Castanea sativa, was introduced in the 1st century A.D. by the Romans and is thus an archaeophyte).
On a worldwide scale the Insubrian (= wet subtropical) climate occurs e.g. in Southern Japan, Eastern China, Eastern USA, South Eastern coast of the Black Sea (Kolchis). There we find forests with evergreen broad, so called laurophyllous leaves (from Laurus nobilis, Laurel, Lorbeer). Thus, the present-day natural vegetation in the lake region of Southern Switzerland does not correspond to the climate in this very region!
Why are there almost no indigenous evergreen laurophyllous tree and shrub species in this lake region? During the warm interglacial periods some species of this kind, e.g. Laurus nobilis and Cinnamomum glanduliferum, lived in this region, but during the glaciations they had to migrate south.
Since the end of the ice age (10’000 years ago) the time was not long enough for most of the evergreen laurophyllous species to migrate back from their remote southern refugia to the relatively small (± insular) region around Lake Maggiore and Lake Lugano with their0z9b Insubrian climate suitable for them. Exceptions are Ilex aquifolium (Common Holly, Stechpalme), Hedera helix (Ivy, Efeu) and, according to Schröter (1936), possibly also Laurus nobilis (Laurel, Lorbeerbaum).
However, if evergreen laurophyllous species from other regions of the world are planted in parks and gardens in the lake regions of S Switzerland they grow very vigorously and spread easily into the surroundings because the climate is suitable for them. In Schoenenberger et al. (in press) 44 laurophyllous species are mentioned, e.g. Prunus laurocerasus from the Middle East and moist environments in the Mediterranean region; Cinnamomum glanduliferum, Ligustrum lucidum, Eleagnus pungens, Trachycarpus fortunei and Lonicera japonica from East Asia; Mahonia species from the Eastern USA (see pp 9-12). In Locarno, even the beautiful Camellia japonica reproduces spontaneously from seed.
Accompanying these species, many other neophytes have established: they show a great diversity in morphology and physiology enabling them to grow in very diverse micro-habitats.