Inhaltszusammenfassung

Chronosequences can provide valuable insights into carbon (C) and nitrogen (N) dynamics across natural gradients with C and N stable isotopes serving as powerful tool investigating these dynamics. We studied changes in delta C-13 and delta N-15 values in litter, organic layer and mineral soil on dunes across the Haast chronosequence (New Zealand), which spans 120 to 2870 years of pedogenesis beneath a temperate rainforest. Decomposition was approximated from linear regression slopes between C...Chronosequences can provide valuable insights into carbon (C) and nitrogen (N) dynamics across natural gradients with C and N stable isotopes serving as powerful tool investigating these dynamics. We studied changes in delta C-13 and delta N-15 values in litter, organic layer and mineral soil on dunes across the Haast chronosequence (New Zealand), which spans 120 to 2870 years of pedogenesis beneath a temperate rainforest. Decomposition was approximated from linear regression slopes between C concentrations and delta C-13 values and termed beta(C). Similarly we calculated beta(N) values to test the relationship between vertical N decrease and delta N-15 increase. Decreasing delta C-13 values of litter with age suggests a physiological response of plants to decreased litter N concentrations. A decrease of litter delta N-15 in the early succession stages and a second decline after 1300 years indicates reduced N-2 fixation. Beta(C) values increased during early ecosystem development and at old sites, and were lowest at the intermediate stages (1500 years), which suggests decomposition did not decrease constantly with time. Beta(N) values were lowest at the youngest site and increased within the first 200 years, likely because litter as the uppermost part of the vertical depth profile reflected an increased supply of N depleted in N-15 provided by fungi. We found relations between beta(C) and beta(N) values suggesting that there might be shared processes shaping delta C-13 and delta N-15 vertical depth profiles, e.g. microbial cycling, transport or sorption.» weiterlesen» einklappen

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DDC Sachgruppe:
Naturwissenschaften