Late-Holocene climate changes linked to ecosystem shifts in the Northwest Wisconsin Sand Plain, USA

Records of century-scale climate variability in the Upper Midwest generally agree that moisture availability increased between 4000 and 3000 cal. yr BP (calendar years before present = 1950 CE), and that there were large, frequent droughts 1000–700 cal. yr BP followed by wetter/cooler conditions. Variability among regional sites, however, remains problematic. In this study we reconstruct climate on the Northwest Wisconsin Sand Plain (NWSP), USA, to identify potential climatic drivers of previously documented changes in vegetation and fire regimes. Oak pollen was replaced by pollen from xeric pine taxa at several sites on the NWSP ~1425 cal. yr BP, accompanied by a change to larger, less frequent charcoal peaks. Another major vegetation change occurred ~700 cal. yr BP, when pollen of the more mesic P. strobus L. (white pine) increased and charcoal influx decreased. We used a vegetation-independent lake-level record to determine whether long-term changes in moisture availability were associated with these ecosystem changes. Decreases in percent organic matter in shallow-water sediment cores from Cheney Lake indicate that the lake level decreased sharply ~1500 cal. yr BP, consistent with the interpretation that the changes in vegetation and fire regime were driven by a severe and previously undocumented drought. The lake level rose again, reaching approximately modern levels by 800–700 cal. yr BP, consistent with the hypothesis of cooler/wetter conditions in the Upper Midwest in the past ~700 years and with the expansion of mesic taxa on the NWSP 700 cal. yr BP.

Root xylem characteristics and hydraulic strategies of species co-occurring in semi-arid Australia

Xylem traits such as xylem vessel size can influence the efficiency and safety of water transport and thus plant growth and survival. Root xylem traits are much less frequently examined than those of branches despite such studies being critical to our understanding of plant hydraulics. In this study, we investigated primary lateral and sinker roots of six co-occurring species of semi-arid Australia. Two species are restricted to a floodplain, two were sampled only from the adjacent sand plain, and two species co-occur in both habitats. We assessed root wood density, xylem traits (i.e., vessel diameter, fibre and vessel wall thickness), outer pit aperture diameter and calculated theoretical hydraulic conductivity and vessel implosion resistance. We hypothesized that (1) roots have larger xylem vessel diameters and lower wood density than branches of the same species and that (2) there is an inverse correlation between theoretical sapwood hydraulic conductivity and vessel implosion resistance for roots. Variation in root wood density was explained by variations in xylem vessel lumen area across the different species (r2 = 0.73, p = 0.03), as hypothesized. We rejected our second hypothesis, finding instead that the relationship between theoretical hydraulic conductivity and vessel implosion resistance was not maintained in roots of all of our studied species, in contrast to our previous study of branches from the same species. Xylem traits were found to depend upon habitat and eco-hydrological niche, with the groupings including (i) arid-adapted shrubs and trees with shallow lateral roots (Acacia aneura and Psydrax latifolia), (ii) trees restricted to the floodplain habitat, both evergreen (Eucalyptus camaldulensis) and deciduous (Erythrina vespertilio) and (iii) evergreen trees co-occurring in both floodplain and adjacent sand plain habitats (Corymbia opaca and Hakea sp.).

“Tobacco has Blossomed like the Rose in the Desert”: Technology, Trees, and Tobacco in the Norfolk Sand Plain, c. 1920-1940

Drawing on rural, biotechnological, and environmental history, this article examines how farmers, corporations, and the state deployed developments in silviculture and agriculture to reshape Norfolk County, Ontario. It traces the emergence of a relatively vibrant flue-cured tobacco sector during the Great Depression, a sector that both broke from and drew on earlier reforestation efforts that had emerged at the start of the twentieth century. In this context, tobacco and trees can best be viewed as biotechnologies connected to a continental flow, rather than simply as natural products. The article also argues that raising both trees and tobacco drew on ideas of conservation and resource management that were tightly bound to the development of rural capitalism, but highlights how the soil and environment influenced the capitalist objective of profitable rural development in ways that frustrated the idea of nature being manageable. It ends by noting that despite the ascendency of capitalist-informed ideas about rural development in Norfolk, other ways of understanding soil and the environment persisted.

Rescuing Cattleya granulosa Lindley in the wild

The Orchid Society of Rio Grande do Norte State, Brazil, through its Group of Experimental Interactive Research (SORN/GEPI), has been study- ing the occurrence of Cattleya granulosa Lindley, 1842, specifically in the coastal sand plain and dune vegetation (“restinga”) and in remaining patches of Atlantic Rainforest in the state.

History of the northern silvery blue (Glaucopsyche lygdamus couperi) (Lepidoptera: Lycaenidae) in southern Ontario, Canada: separating range expansion from original populations and other subspecies

The historical distribution of Glaucopsyche lygdamus (Doubleday) (Lepidoptera: Lycaenidae) in southern Ontario, Canada was analysed using three major databases. In southern Ontario, G. lygdamus includes (1) subspecies G. lygdamus couperi Grote that has expanded its range from the north since the 1940s and 1950s reaching Hamilton, Ontario, Canada in 2012; (2) a non-expanding population on the Norfolk Sand Plain, Ontario, Canada that appears phenotypically closest to G. lygdamus couperi, but with some wing marking characters that are transitional to the more southern subspecies G. lygdamus lygdamus; and (3) rare and local pre-expansion populations referable to G. lygdamus couperi that occurred in the Ottawa Valley and Bruce Peninsula, Ontario, Canada in alvar woodlands, and possibly also on lakeshore dunes. The very rare and local occurrences of silvery blue in southern Ontario in the past is in direct contrast to its increasing abundance in the area in present times, but the genetic and phenotypic diversity of silvery blue may be declining due to genetic mixing with and/or to the effect of increasing parasitoids from the expanding race.