Davidsonia

Davidsonia - A Journal of Botanical Garden Science

Editor, Iain Taylor writes about man-made and natural disturbances to ecosystems and the need to understand the impacts of these disturbances.

During over 15 years of plant ecological research in the Kluane region of southwestern Yukon, our studies required us to grow, propagate, and sometimes kill, native plants for experimental purposes. Here we present observations on germinating, growing, propagating and transplanting some of the common native plant species in the Kluane region.

The 1997 Red River flood afforded a valuable opportunity for studying the impact of an infrequent severe disturbance on gallery forests. In 1997 and 2002 we sampled two sites protected and two sites unprotected by a flood control structure near Winnipeg, Manitoba, Canada using three 150 m transects in the lower floodplain (n = 45 quadrats per site). The mature canopy of unprotected sites consisted of Fraxinus pennsylvanica Marsh. and Ulmus americana L. at low cover whereas protected sites contained five tree species. Regeneration data suggest F. pennsylvanica will continue to dominate in unprotected sites, with treefall providing opportunities for pioneer flood specialists like Salix amygdaloides Anderss. Fewer gap openings occurred in protected sites, in which Acer negundo L. and F. pennsylvanica will likely become co-dominants.

Understorey taxa normally able to survive the moderate disturbance associated with seasonal inundation of the lower floodplain of protected sites succumbed to the harsh conditions in the unprotected sites. Many were knocked back or eliminated by 2002, with greater reductions in richness and diversity in unprotected sites. Ruderals were promoted in unprotected sites but most were less prominent by 2002. Although several taxa, e.g., Vitis riparia Michx. and Bidens frondosa L. had significantly higher cover in protected sites by 2002, Xanthium strumarium L. and Polygonum amphibium L. were the only understorey species with significantly higher cover in the unprotected sites. Correspondence analysis indicated flood protection generated differing trajectories, with site differences contributing to variable successional outcomes.

Senescence processes in plants edited by Susheng Gan, Annual Plant Reviews 26 (2007) Blackwell Publishing
Ltd, Oxford, UK; Ames, Iowa: and Carlton, Australia; and The Physiology of Crop Yield, 2nd Ed. 2006, Robert KM Hay and John R Porter, Blackwell Publishing, Oxford, UK; Ames, IA; Carlton,Australia are reviewed.

Notes on papers (some technical and others less so) that may be of interest.

Davidsonia - A Journal of Botanical Garden Science

Editor, Iain Taylor writes on the need for environmental protection of endangered habits in the face of encroaching human development and a changing climate.

A series of maps compare the 1800, 1938 and 2005 ecosystems in the Okanagan and Lower Similkameen Valleys. Much of the gentle slope valley bottom ecosystems have been replaced by urban and agricultural development. Analysis of the areal extent of historical and remaining areas has been done for specific ecosystem types that are important for many species at risk and are themselves ecosystems at risk. These include: Douglas-fir – pine-grass gentle slope; Ponderosa pine – bluebunch wheatgrass gentle slope; water birch – red-osier dogwood wetland riparian shrub; black cottonwood – red-osier dogwood floodplain; the Okanagan River ecosystem; cattail marsh; Idaho fescue – bluebunch wheat-grass grassland; big sagebrush shrub-steppe and antelope-brush – needle-and-thread grass shrub-steppe. For two of these ecosystems, over 90 percent of the original ecosystem has been lost.

Uses of this mapping for conservation of species at risk are presented, including applications to status assessment, quantification of threats, informing restoration projects, and providing data on the importance of the remaining areas of ecosystems that have been severely depleted. The paper concludes that it is important to focus on conservation of ecosystems in order to maintain species at risk.

Notes on papers (some technical and others less so) that may be of interest.