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ScienceDaily_2013 17694.txt

#Spring may come earlier to North american forests, increasing uptake of carbon dioxidetrees in the con ti nen tal U s. could send out new spring leaves up to 17 days ear lier in the com ing cen tury than they did before global tem per a tures started to rise accord ing to a new study by Prince ton Uni ver sity researchers. These climate-driven changes could lead to changes in the com po si tion of north east ern forests and give a boost to their abil ity to take up car bon dioxide. Trees play an impor tant role in tak ing up car bon diox ide from the atmos phere so researchers led by David Med vigy assis tant pro fes sor in Princeton's depart ment of geo sciences wanted to eval u ate pre dic tions of spring bud burst --when decid u ous trees push out new growth after months of win ter dor mancy--from mod els that pre dict how car bon emis sions will impact global temperatures. The date of bud burst affects how much car bon diox ide is taken up each year yet most cli mate mod els have used overly sim plis tic schemes for rep re sent ing spring bud burst mod el ing for exam ple a sin gle species of tree to rep re sent all the trees in a geo graphic region. In 2012 the Prince ton team pub lished a new model that relied on warm ing tem per a tures and the wan ing num ber of cold days to pre dict spring bud burst. The model which was pub lished in the Jour nal of Geo phys i cal Research proved accu rate when com pared to data on actual bud burst in the north east ern United states. In the cur rent paper pub lished online in Geo phys i cal Research Let ters Med vigy and his col leagues tested the model against a broader set of obser va tions col lected by the USA National Phe nol ogy Net work a nationwide tree ecol ogy mon i tor ing net work con sist ing of fed eral agen cies edu ca tional insti tu tions and cit i zen sci en tists. The team incor po rated the 2012 model into pre dic tions of future bud burst based on four pos si ble cli mate sce nar ios used in plan ning exer cises by the Inter gov ern men tal Panel on Cli mate Change. The researchers included Su-Jong Jeong a post doc toral research asso ciate in Geo sciences along with Elena Shevli akova a senior cli mate mod eler and Sergey Maly shev a pro fes sional spe cial ist both in the Depart ment of Ecol ogy and Evo lu tion ary Biol ogy and asso ci ated with the U s. National Oceanic and Atmos pheric Administration's Geo phys i cal Fluid Dynam ics Laboratory. The team esti mated that com pared to the late 20th cen tury red maple bud burst will occur 8 to 40 days ear lier depend ing on the part of the coun try by the year 2100. They found that the north ern parts of the United states will have more pro nounced changes than the south ern parts with the largest changes occur ring in Maine New york Michi gan and Wisconsin. The researchers also eval u ated how warm ing tem per a tures could affect the bud burst date of dif fer ent species of tree. They found that bud burst shifted to ear lier in the year in both early-budding trees such as com mon aspen (Pop u lus tremu loides) and late-budding trees such as red maple (Acer rubrum) but that the effect was greater in the late-budding trees and that over time the dif fer ences in bud ding dates narrowed. The researchers noted that early bud burst may give decid u ous trees such as oaks and maples a com pet i tive advan tage over ever green trees such as pines and hem locks. With decid u ous trees grow ing for longer peri ods of the year they may begin to out strip growth of ever greens lead ing to last ing changes in for est make-up. The researchers fur ther pre dicted that warm ing will trig ger a speedup of the spring green wave or bud burst that moves from south to north across the con ti nent dur ing the spring. The find ing is also inter est ing from the stand point of future changes in spring time weather said Med vigy because bud burst causes an abrupt change in how quickly energy water and pol lu tants are exchanged between the land and the atmos phere. Once the leaves come out energy from the sun is used increas ingly to evap o rate water from the leaves rather than to heat up the sur face. This can lead to changes in daily tem per a ture ranges sur face humid ity stream flow and even nutri ent loss from ecosys tems accord ing to Medvigy. Story Source: The above story is provided based on materials by Princeton university. The original article was written by Cather ine Zan donella. Note: Materials may be edited for content and length. Journal References Â

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