Long tem measurement along chronosequence of post mining sites, a good tool to explore ecosystem transition.

Jan Frouz1, Martin Bartuska1
1 Institute for environmental studies, Charles University

O 1.1 in Long term trends in the functioning of ecosystems

14.07.2014, 11:15-11:35, H18

Using chronosequences us a useful tool how to study ecosystem development over prolonged period of time (decades or centuries).  However, chronosequence approach suffers from many pitfalls. Here we show how long term study of the same chronosequence can improve our understanding of ecosystem development over time. We used two chronosequences of post mining sites both covering sites 1-50 year old at the begging of observation, ether reclaimed by planting alder or left to spontaneous development. Spontaneous vegetation in these sites starting by her band grasses, 15-20 year old sites are typically covered by shrubs namely Salix caprea and sites older than 30-40 years by pioneer forest dominated by Betula pendula and Populus tremula. The aboveground and belowground biomass and content of major biogenic element in biomass and soil was studied in these chronosequences and resurveyed repeatedly on the same sites after 10 or in some parameter for 20 years.  Both chronosequence approach as well as rate of increase observed by repeated measuring of the same plots shows that primary production, soil organic matter accumulation and C and N stock in soil rapidly increase in reclamation sites during first 20 years after tree planting but then development stops.  In contrary, changes in these parameters in unreclaimed sites were slow at the young sites but become more dramatic in 20 years old or older sites.  Transferring soil block between sites show that when the soil from different succession stages are exposed on the same sites then the rate of  C storage is about the same, although more recalcitrant pool of  C become more pronounced in  older soils.  This suggest that observed decrease of  C storage in older reclaimed sites is more likely due to differences in production then by soil saturation by soil organic matter.  P stock in soil show slight decrees over time corresponding with transfer of P in to plant biomass. 

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Letzte Änderung 26.03.2014