ECOLOGICAL RESTORATION AND BIOLOGICAL INVASIONS

Grasslands National Park (in southwestern Saskatchewan near the Saskatchewan-Montana border) is the only national park in Canada within the mixed-grass prairie region. Our study site is a former agricultural field within the park that was abandoned about 10 years before the study began. Between 1994 and 1997, we tested several seeding methods and neighbor control treatments to determine how best to establish native grasses (C4 grass Bouteloua gracilis, and C3 grasses Hesperostipa comata, Koeleria macrantha, Elymus lanceolatus, Pascopyrum smithii) in this old field. Results indicated that year-to-year climatic variation was more important than neighbor control, and that no one seeding method was best in all years (Wilson et al. 2004).

During this time, Agropyron cristatum, an introduced C3 grass, spread into the old field from a nearby roadside. In 2002, we resampled the vegetation to investigate the effects of restoration on invasion by A. cristatum. The results from this study (Bakker & Wilson 2004; abstract below) suggest that pro- active management (ecological restoration) can reduce the rate of invasion by introduced species. Agropyron cristatum cover declined as cover of planted C3 grasses or a planted C4 grass increased (i.e., it was negatively correlated with both groups). However, A. cristatum cover declined more rapidly with increasing C3 grass cover (i.e., the strength of the correlation was stronger) than with increasing C4 grass cover. Therefore, this study also suggests that invasion by introduced species might be slowed by seeding areas with species with similar phenology and physiology as the introduced species of concern.

Abstract

1. Biological invasion can permanently alter ecosystem structure and function. Invasive species are difficult to eradicate, so methods for constraining invasions would be ecologically valuable. We examined the potential of ecological restoration to constrain invasion of an old field by Agropyron cristatum, an introduced C3 grass.
2. A field experiment was conducted in the northern Great Plains of North America. One-hundred and forty restored plots were planted in 1994-96 with a mixture of C3 and C4 native grass seed, while 100 unrestored plots were not. Vegetation on the plots was measured periodically between 1994 and 2002.
3. Agropyron cristatum invaded the old field between 1994 and 2002, occurring in 5% of plots in 1994 and 66% of plots in 2002, and increasing in mean cover from 0.2% in 1994 to 17.1% in 2002. However, A. cristatum invaded one-third fewer restored than unrestored plots between 1997 and 2002, suggesting that restoration constrained invasion. Further, A. cristatum cover in restored plots decreased with increasing planted grass cover. Stepwise regression indicated that A. cristatum cover was more strongly correlated with planted grass cover than with distance from the A. cristatum source, species richness, percentage bare ground or percentage litter.
4. The strength of the negative relationship between Agropyron cristatum and planted native grasses varied among functional groups: the correlation was stronger with species with phenology and physiology similar to A. cristatum (i.e. C3 grasses) than with dissimilar species (C4 grass).
5. Richness and cover of naturally establishing native species decreased with increasing Agropyron cristatum cover. In contrast, restoration had little effect on the establishment and colonization of naturally establishing native species. Thus, A. cristatum hindered colonization by native species while planted native grasses did not.
6. Synthesis and applications. To our knowledge, this study provides the first indication that restoration can act as a filter, constraining invasive species while allowing colonization by native species. These results suggest that resistance to invasion depends on the identity of species in the community and that restoration seed mixes might be tailored to constrain selected invaders. Restoring areas before invasive species become established can reduce the magnitude of biological invasion.

References

Bakker, J.D., & S.D. Wilson. 2004.

Using ecological restoration to constrain biological invasion. Journal of Applied Ecology 41:1058-1064.

Wilson, S.D., J.D. Bakker, J.M. Christian, X. Li, L.G. Ambrose, & J. Waddington. 2004.

Semiarid old-field restoration: is neighbor control needed? Ecological Applications 14:476- 484.

CHAMAECYPARIS NOOTKATENSIS IS NOW CALLITROPSIS NOOTKATENSIS: YELLOW CEDAR BY ANY OTHER NAME WOULD STILL SMELL AS YELLOW CEDAR

Recently, a new species of conifer was found among the remnants of moist karst forest in northern Vietnam (Averyanov et al. 2002; Farjon et al. 2002) and a new genus - Xanthocyparis - was described to accomodate this species that was described as Xanthocyparis vietnamensis Farjon & Hiep. See also BEN # 284 & # 296.

Farjon et al. (2002) analyzed 54 morphological characters that placed Xanthocyparis vietnamensis sister to Chamaecyparis nootkatensis within a paraphyletic subfamily Cupressoideae. The result of this analysis prompted nomenclatural transfer of C. nootkatensis to the genus Xanthocyparis as well as the renaming of three intergeneric hybrids.

In this study (Little et al. 2004), analysis of ITS (nrDNA), matK, and rbcL sequence data in combination with 58 morphological characters confirmed monophyly of Xanthocyperis as it was dsecribed by Farjon et al. 2002).

However, based on the International Code of Botanical Nomenclature, this new genus name cannot stand. The genus Callitropsis Oersted (non Callitropsis sensu Compton 1922) with Callitropsis nootkatensis (D. Don) Oerst. was described in 1865 and has the priority over the recent name Xanthocyparis. Because Xanthocyparis vietnamensis and Callitropsis nootkatensis are sister taxa and appear to be relatively closely allied, Little (in Little et al. 2004, p. 1879) tranferred X. vietnamensis to the genus Callitropsis and made the following new combination: Callitropsis vietnamensis (Farjon & Hiep) D.P. Little.

As now circumscribed, Callitropsis contains the following two species with disjunct distribution: Callitropsis nootkatensis (native to western North America), and Callitropsis vietnamensis (native to moist karst forest in northern Vietnam).

References:

Averyanov, L.V., N.T. Hiep, D.K. Harder, & P.K. Loc. 2002.

The history of discovery and natural habitats of Xanthocyparis vietnamensis (Cupressaceae). Turczaninowia 5: 31-39.

Farjon, A, N.T. Hiep, D.K. Harder, P.K. Loc, & L. Averyanov. 2002.

A new genus and species in the Cupresaceae (Coniferales) from northern Vietnam, Xanthocyparis vietnamensis. Novon 12: 179-189.

Little, D.P., A.E. Schwarzbach, R.P. Adams, & C.-F. Hsieh. 2004.

The circumscription and phylogenetic relationships of Callitropsis and the newly described genus Xanthocyparis (Cupressaceae). Amer. J. Bot. 9(11): 1872-1881.

NEW BOOK: LICHEN HUNTERS

Gilbert, Oliver. 2004.

The lichen hunters. The Book Guild Ltd, Lewes, UK. 192 p. ISBN 1 85776 930 9 [hard cover] Price: GBP 16.90 Postage (in GBP): UK 2.00, Europe 3.50, rest of the world 6.00

Order from:

The Book Guild Ltd., Temple House, 25 High Street, Lewes, BN7 2LU, UK. Credit card orders +44(0)1825 723 398

'The author's pursuit of lichens has taken him and his friends from the Highlands of Scotland to the remotest Hebrides islands, and on to the churchyards, disused airfields and saltwater lagoons in lowland England. Willing to travel huge distances, investigate inaccessible and dangerous terrain, and endure every form of extreme climate these lichen enthusiasts retain an almost childlike delight at the discovery of a rare species.

Part travelogue and part a social history of the British Lichen Society The Lichen Hunters is an engrossing read. The Lichen Hunters has been written to put on record what it was like to be a member of that heady, first generation of lichenologists following on from a long period of neglect of the subject. The author relates with affection his adventures in long forgotten forests, the rewards of employing expedition tactics to investigate remote areas, and the delights of surveying lake margins. Changes to field work over the last fifty years are described and anecdotes about leading personalities recounted.

From: http://www.bookguild.co.uk/preview.htm :

The Lichen Hunters is an enthusiastic account of the recent years of a burgeoning ecological movement - The British Lichen Society. Formed in 1958 the society created a complete listing of all British lichens. Lichens are like a multitude of small watchmen recording the progress of pollution across the countryside. They are indicators of air-quality, traffic pollution, fertilizers and acid rain. The Lichen Hunters will charm readers and be a valuable addition to the ecological canon.

Oliver Gilbert gained a degree in Botany from Exeter University. He worked as Deputy Warden at Malham Tarn Field Centre in North West Yorkshire and then at the Botany Department of the University of Newcastle. He has been President of the British Lichen Society and in 2004 was the recipient of the Ursula Duncan award for his outstanding contribution to British lichenology.

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