12/20/2023 0 Comments Ecotone fires![]() The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon-juniper woodland shifted extensively (2 km or more) and rapidly (<5 years) through mortality of ponderosa pines in response to a severe drought. However, current models do not adequately provide for such rapid effects-particularly those caused by mortality-largely because of the lack of data from field studies. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. The results point the fire caused by indigenous people as the principal controlling factor for forest and savanna dynamics during the past 1550 years.In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. The arrival of the European settler and the subsequent introduction of cattle, is suggested as the main reason for the decrease of fire in the study region. The relatively lower fire activity after 300 cal yr BP until present-day favored the increase of forested area at both TIA and FC sites. The high amount of charred particles found in the sediments, indicate fires with a marked increase between 1400 to 1000 cal yr BP (FC site) and 700 to 300 cal yr BP (TIA site), and probably caused the retreat of forest cover during these two time intervals. Between 700 and 300 cal yr BP savanna and Mauritia palm swamp increased and forest area decreased. From 1000 to 700 forest expanded while savanna and Mauritia palm swamp reduced. At the TIA site the savanna cover was dominant between 12 cal yr BP. Upper treeline environments have been hypothesized to be some of the most sensitive to. adjacent to PJ, but no PJ fire scars or PJ age structure Muldavin et al (2003) south-central, NM fire-scarred piñon at PJ/PIPO ecotone, but insufficient tree age data to assess severity in PJ woodland Huffman et al. We studied the effects of a shift in the fire regime of an ecosystem that is very sensitive to climate change: the ecotone from closed forest to open alpine. From 900 to 300 cal yr BP the savanna and palm swamp taxa became dominant and the forest area decreased. Impacts of disturbance and climate change on alpine treeline ecotones. ![]() The FC site was marked by savanna and Mauritia cover with a slight increase of forest between ca. From 1400 to 1050 cal yr BP, forest cover retreated while savanna, and the Mauritia palm swamp expanded considerably. flexuosa started to establish on the site indicating sufficient soil moisture. At the FC site was recorded a higher proportion of forest cover, suggesting local wetter climatic conditions favorable for forest expansion, especially by gallery forests, between 15 cal yr BP. Based on 5 radiocarbon dates, these records allow the reconstruction of the vegetation fire and climate dynamics during the past 1550 years. The cores Fazenda Cigana (FC) and Terra Indígena Aningal (TIA) were taken from a savanna-forest ecotone area in the Roraima State, northern Brazilian Amazon. Two sediment cores from Mauritia flexuosa palm swamps have been studied by pollen and charcoal analysis.
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