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Ecosystem Properties and Forest Decline in Contrasting Long-Term Chronosequences
David A. Wardle,1,2*Lawrence R. Walker,3Richard D. Bardgett4
During succession, ecosystem development occurs; but in thelong-term absence of catastrophic disturbance, a decline phaseeventually follows. We studied six long-term chronosequences,in Australia, Sweden, Alaska, Hawaii, and New Zealand; for each,the decline phase was associated with a reduction in tree basalarea and an increase in the substrate nitrogen–to-phosphorusratio, indicating increasing phosphorus limitation over time.These changes were often associated with reductions in litterdecomposition rates, phosphorus release from litter, and biomassand activity of decomposer microbes. Our findings suggest thatthe maximal biomass phase reached during succession cannot bemaintained in the long-term absence of major disturbance, andthat similar patterns of decline occur in forested ecosystemsspanning the tropical, temperate, and boreal zones.
1 Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, SE901 83 Umeå, Sweden. 2 Landcare Research, Post Office Box 69, Lincoln, New Zealand. 3 Department of Biological Sciences, Box 454004, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154–4004, USA. 4 Institute of Environmental and Natural Sciences, Lancaster University, Lancaster LA1 4YQ, UK.
* To whom correspondence should be addressed. E-mail: david.wardle{at}svek.slu.se
