TY - JOUR T1 - Early holocene openlands in southern New England JF - Ecology Y1 - 2006 A1 - Faison, E. K. A1 - Foster, D. R. A1 - Oswald, W. W. A1 - Hansen, B. C. A1 - Doughty, E. KW - *Ambrosia KW - *Pollen KW - Ecosystem KW - Geography KW - new england KW - Paleontology AB - The pre-historical vegetation structure in temperate forest regions is much debated among European and North American ecologists and conservationists. Frans Vera's recent hypothesis that large mammals created mosaics of forest and openland vegetation in both regions throughout the Holocene has been particularly controversial and has provoked new approaches to conservation management. Thirty years earlier, American paleoecologists Herb Wright and Margaret Davis debated whether abundant ragweed pollen at Rogers Lake, Connecticut at 9500 yr BP signified local forest openings or long-distance transport of pollen from Midwestern prairies. Using new pollen records from Harvard Forest and the North American Pollen Database, we address this question and offer insights to the openland discussion. Ragweed and other forbs exceed 3.5% at five sites in a restricted area of southern New England between 10,100 and 7700 yr BP. Strong evidence suggests this pollen originated from the landscapes surrounding these sites (supporting Davis), as ragweed pollen percentages do not increase with longitude from New England to the Midwest. Ragweed pollen percentages are also unrelated to basin size and therefore unrelated to the proportion of extraregional pollen in New England. High forbs values were associated with increases in oak, decreases in white pine, and relatively high charcoal values. Modern pollen records with similar forb and tree percentages occur along the Prairie Peninsula region of the Upper Midwest. However, the closest analogue to the southern New England early Holocene assemblages comes from Massachusetts' Walden Pond in the early 18th century. These results and the affiliation of ragweed for open, disturbed habitats suggest that oak-pine forests with large openings persisted for over 2000 years due to dry conditions and perhaps increased fire frequency. This conclusion is corroborated by independent lake level and climate reconstructions. Because these early Holocene openlands have no detectable analogue in New England for the past 7000 years before European settlement, we suggest that all important openlands today are almost exclusively a legacy of Colonial agriculture and should be managed accordingly. Nonetheless, our results may have implications for forest dynamics accompanying projected climate change to more arid conditions in New England over the next century. VL - 87 SN - 0012-9658 (Print)0012-9658 (Linking) IS - 10 N1 - Faison, E KFoster, D R Oswald, W W Hansen, B C S Doughty, E eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2006/11/09 09:00 Ecology. 2006 Oct;87(10):2537-47. ER - TY - JOUR T1 - Uncertainties and novel prospects in the study of the soil carbon dynamics JF - Chemosphere Y1 - 2002 A1 - Wang, Y. A1 - Hsieh, Y. P. KW - Carbon Dioxide/chemistry/metabolism KW - Carbon Radioisotopes/analysis KW - Carbon/*chemistry/metabolism KW - Ecosystem KW - Kinetics KW - Models, Chemical KW - Plants/metabolism KW - Seasons KW - Soil/*analysis AB - Establishment of the Kyoto Protocol has resulted in an effort to look towards living biomass and soils for carbon sequestration. In order for carbon credits to be meaningful, sustained carbon sequestration for decades or longer is required. It has been speculated that improved land management could result in sequestration of a substantial amount of carbon in soils within several decades and therefore can be an important option in reducing atmospheric CO2 concentration. However, evaluation of soil carbon sources and sinks is difficult because the dynamics of soil carbon storage and release is complex and still not well understood. There has been rapid development of quantitative techniques over the past two decades for measuring the component fluxes of the global carbon cycle and for studying the soil carbon cycle. Most significant development in the soil carbon cycle study is the application of accelerator mass spectrometry (AMS) in radiocarbon measurements. This has made it possible to unravel rates of carbon cycling in soils, by studying natural levels of radiocarbon in soil organic matter and soil CO2. Despite the advances in the study of the soil carbon cycle in the recent decades, tremendous uncertainties exist in the sizes and turnover times of soil carbon pools. The uncertainties result from lack of standard methods and incomplete understanding of soil organic carbon dynamics, compounded by natural variability in soil carbon and carbon isotopic content even within the same ecosystem. Many fundamental questions concerning the dynamics of the soil carbon cycle have yet to be answered. This paper reviews and synthesizes the isotopic approaches to the study of the soil carbon cycle. We will focus on uncertainties and limitations associated with these approaches and point out areas where more research is needed to improve our understanding of this important component of the global carbon cycle. VL - 49 SN - 0045-6535 (Print)0045-6535 (Linking) UR - https://www.ncbi.nlm.nih.gov/pubmed/12430658 IS - 8 N1 - Wang, YangHsieh, Yuch-Ping eng England 2002/11/15 04:00 Chemosphere. 2002 Dec;49(8):791-804. ER -