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Titel |
Climate and root proximity as dominant drivers of enzyme activity and C and N isotopic signature in soil |
VerfasserIn |
Svenja Stock, Moritz Köster, Michaela Dippold, Jens Boy, Francisco Matus, Carolina Merino, Francisco Nájera, Sandra Spielvogel, Anna Gorbushina, Yakov Kuzyakov |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250145635
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Publikation (Nr.) |
EGU/EGU2017-9597.pdf |
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Zusammenfassung |
The Chilean ecosystems provide a unique study area to investigate biotic controls on soil
organic matter (SOM) decomposition and mineral weathering depending on climate (from
hyper arid to temperate humid). Microorganisms play a crucial role in the SOM
decomposition, nutrient release and cycling. By means of extracellular enzymes
microorganisms break down organic compounds and provide nutrients for plants. Soil
moisture (abiotic factor) and root carbon (biotic factor providing easily available energy
source for microorganisms), are important factors for microbial decomposition of SOM and
show strong gradients along the investigated climatic gradient. A high input of root carbon
increases microbial activity and enzyme production, and facilitates SOM breakdown and
nutrient release
The aim of this study was to determine the potential enzymatic SOM decomposition and
nutrient release depending on root proximity and precipitation. C and N contents, δ13C and
δ15N values, and kinetics (Vmax, Km) of six extracellular enzymes, responsible for C, N, and
P cycles, were quantified in vertical (soil depth) and horizontal (from roots to bulk soil)
gradients in two climatic regions: within a humid temperate forest and a semiarid open
forest.
The greater productivity of the temperate forest was reflected by higher C and N contents
compared to the semiarid forest. Regression lines between δ13C and -[ln(%C)] showed a
stronger isotopic fractionation from top- to subsoil at the semiarid open forest, indicating a
faster SOM turnover compared to the humid temperate forest. This is the result of more
favorable soil conditions (esp. temperature and smaller C/N ratios) in the semiarid forest.
Depth trends of δ15N values indicated N limitation in both soils, though the limitation at
the temperate site was stronger. The activity of enzymes degrading cellulose and
hemicellulose increased with C content. Activity of enzymes involved in C, N and P
cycles decreased from top- to subsoil and with distance to roots. Chitinase and acid
phosphatase activities increased with increasing C contents and indicated a faster
substrate turnover in soil under the temperate forest compared to the semiarid forest. In
contrast, Tyrosin-aminopeptidase activities indicated a faster substrate turnover under
semiarid forest than the temperate forest, and strongly increased with increasing N
content.
We conclude that the N availability and SOM turnover under semiarid open forest is
higher than under humid temperate forest. The enzyme activities are depending on depth only
indirectly and are driven mainly by soil C content, which is directly affected by root carbon
input. |
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