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Forest Ecotone (forest + ecotone)
Selected AbstractsThe Deciduous Forest , Boreal Forest EcotoneGEOGRAPHY COMPASS (ELECTRONIC), Issue 7 2010David Goldblum Ecotones have been subject to significant attention over the past 25 years as a consensus emerged that they might be uniquely sensitive to the effects of climate change. Most ecotone field studies and modeling efforts have focused on transitions between forest and non-forest biomes (e.g. boreal forest to Arctic tundra, forest to prairie, subalpine forests to alpine tundra) while little effort has been made to evaluate or simply understand forest,forest ecotones, specifically the deciduous forest , boreal forest ecotone. Geographical shifts and changes at this ecotone because of anthropogenic factors are tied to the broader survival of both the boreal and deciduous forest communities as well as global factors such as biodiversity loss and dynamics of the carbon cycle. This review summarizes what is known about the location, controlling mechanisms, disturbance regimes, anthropogenic impacts, and sensitivity to climate change of the deciduous forest , boreal forest ecotone. [source] Late-glacial and Holocene climatic effects on fire and vegetation dynamics at the prairie,forest ecotone in south-central MinnesotaJOURNAL OF ECOLOGY, Issue 5 2003Philip Camill Summary 1Treeline ecotones, such as the prairie,forest boundary, represent climatically sensitive regions where the relative abundance of vegetation types is controlled by complex interactions between climate and local factors. Responses of vegetation and fire to climate change may be tightly linked as a result of strong feedbacks among fuel production, vegetation structure and fire frequency/severity, but the importance of these feedbacks for controlling the stability of this ecotone is unclear. 2In this study, we examined the prairie,forest ecotone in south-central Minnesota using two lake sediment cores to reconstruct independent records of climate, vegetation and fire over the past 12 500 years. Using pollen, charcoal, sediment magnetic analyses and LOI properties, we investigated whether fires were controlled directly by climate or indirectly by fuel production. 3Sediment magnetic and LOI data suggest four broad climatic periods occurring c. 11 350,8250 BP (cool/humid), c. 8250,4250 BP (warm/dry), c. 4250,2450 BP (warm/humid), and c. 2450,0 BP (cool/humid), indicating that, since the mid-Holocene, climate has shifted towards wetter conditions favouring greater in-lake production and fuel production on the landscape. 4The area surrounding both lakes was characterized by boreal forest c. 12 500,10 000 BP, changing to an Ulmus-Ostrya forest c. 10 000,9000 BP, changing to a community dominated by prairie (Poaceae-Ambrosia-Artemisia) and deciduous forest taxa c. 8000,4250 BP, and finally shifting to a Quercus -dominated woodland/savanna beginning c. 4250,3000 BP. 5Charcoal influx increased from an average of 0.11,0.62 mm2 cm,2 year,1 during the early Holocene forest period (c. 11 350,8250 BP) to 1.71,3.36 mm2 cm,2 year,1 during the period of prairie expansion (c. 8250,4250 BP) and again increased to 4.18,4.90 mm2 cm,2 year,1 at the start of the woodland/savanna period (c. 4250 BP). 6As a result of the influence of climate on community composition and fuel productivity, changes in fire severity may be the result and not the cause of shifts in vegetation. [source] Testing alternative mechanisms of evolutionary divergence in an African rain forest passerine birdJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2005T. B. Smith Abstract Models of speciation in African rain forests have stressed either the role of isolation or ecological gradients. Here we contrast patterns of morphological and genetic divergence in parapatric and allopatric populations of the Little Greenbul, Andropadus virens, within different and similar habitats. We sampled 263 individuals from 18 sites and four different habitat types in Upper and Lower Guinea. We show that despite relatively high rates of gene flow among populations, A. virens has undergone significant morphological divergence across the savanna,forest ecotone and mountain,forest boundaries. These data support a central component of the divergence-with-gene-flow model of speciation by suggesting that despite large amounts of gene flow, selection is sufficiently intense to cause morphological divergence. Despite evidence of isolation based on neutral genetic markers, we find little evidence of morphological divergence in fitness-related traits between hypothesized refugial areas. Although genetic evidence suggests populations in Upper and Lower Guinea have been isolated for over 2 million years, morphological divergence appears to be driven more by habitat differences than geographic isolation and suggests that selection in parapatry may be more important than geographic isolation in causing adaptive divergence in morphology. [source] Alternatives for Reintroducing a Rare Ecotone Species: Manually Thinned Forest Edge versus Restored Habitat RemnantRESTORATION ECOLOGY, Issue 5 2009Jennifer Possley Abstract Species native to ecotones are often overlooked in restoration efforts despite the increasing rarity of ecotone habitat. In fragmented, fire-suppressed landscapes, true ecotone may no longer exist. Restoration biologists interested in reintroducing ecotone species must decide whether to plant them in historic ecotones maintained by manual thinning or whether to opt for discrete restoration areas that are easier to maintain. We investigated these two alternatives with Lantana canescens, a rare tropical shrub native to the ecotone between pine and hardwood forests of Miami-Dade County, Florida, U.S.A. Our short-term findings show that after 15 and 18 months, survival of transplants was 69% in a restored site and 65% and 84% in two historic ecotone sites. The restored site had significantly higher photosynthetically active radiation (PAR) (75%) than the historic ecotones (25,39%). Correspondingly, 267 seedlings have recruited at the restored site, whereas only 8 have emerged at both historic ecotone sites. Seedling establishment was associated with higher PAR at the restored site. We found that overall population sustainability was higher at the restored site where there is the additional benefit of less maintenance. Our work suggests that, by reducing succession, a discrete restoration area can approach the historic conditions of hardwood/pine forest ecotone more closely than degraded historic ecotones themselves. We present a viable solution for conserving rare ecotone species when their natural habitat and the processes that maintained it no longer exist. [source] The Deciduous Forest , Boreal Forest EcotoneGEOGRAPHY COMPASS (ELECTRONIC), Issue 7 2010David Goldblum Ecotones have been subject to significant attention over the past 25 years as a consensus emerged that they might be uniquely sensitive to the effects of climate change. Most ecotone field studies and modeling efforts have focused on transitions between forest and non-forest biomes (e.g. boreal forest to Arctic tundra, forest to prairie, subalpine forests to alpine tundra) while little effort has been made to evaluate or simply understand forest,forest ecotones, specifically the deciduous forest , boreal forest ecotone. Geographical shifts and changes at this ecotone because of anthropogenic factors are tied to the broader survival of both the boreal and deciduous forest communities as well as global factors such as biodiversity loss and dynamics of the carbon cycle. This review summarizes what is known about the location, controlling mechanisms, disturbance regimes, anthropogenic impacts, and sensitivity to climate change of the deciduous forest , boreal forest ecotone. [source] | ||||||||||