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DTSTART:20081026T030000
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RDATE:20091025T030000
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DTSTAMP:20260819T101716Z
DESCRIPTION:Eingeladen durch Prof. Zech. We studied 15N natural abundance i
 n different soil N pools (total N\, NH4+–N\, NO3––N\, DON) and plant leave
 s in the toposequence of alpine ecosystems in the Northern Caucasus. The t
 oposequence was represented by (1) low-productive alpine lichen heath of w
 ind-exposed ridge and upper slope\; (2) more productive Festuca varia gras
 sland of middle slope\; (3) most productive Geranium gymnocaulon/Hedusarum
  caucasicum meadow of lower slope\; (4) low-productive snow-bed community 
 of the slope bottom. We found that &#948\;15N of soil N pools correlate wi
 th N mineralization and nitrification\, and concluded that these values of
  soil N are useful to evaluate the relative N transformation activity in a
 lpine soils of the Northern Caucasus. To study the role of different mycor
 rhizal symbionts in control N isotopes composition of alpine plants we stu
 died 25 plant species from 8 functional/mycorrhizal groups from a multi-sp
 ecies N-limited alpine lichen heath. Different groups were represented by 
 ericoid mycorrhizal species\, ectomycorrhizal species\, arbuscular mycorrh
 izal forbs\, arbuscular mycorrhizal grasses\, arbuscular mycorrhizal nodul
 ated legumes\, non-mycorrhizal graminoids (sedges and rushes)\, non-mycorr
 hizal hemiparasites\, and orchids. Investigated functional groups of alpin
 e plants can be combined into two groups: (1) ericoid mycorrhizal and ecto
 mycorrhizal species\, arbuscular mycorrhizal forbs and grasses\, and non-m
 ycorrhizal hemiparasites were characterized by relatively low 15N enrichme
 nt\, while (2) non-mycorrhizal sedges\, N2-fixing legumes and orchids were
  more enriched with heavy N isotope. Nitrogen isotopic composition of 22 p
 lant species from all investigated communities demonstrated significant re
 sponse to input of different N sources with different &#948\;15N into the 
 soil. All investigated species showed increase of foliar &#948\;15N when 1
 5N-enriched NO3––N (&#948\;15N = +9.5‰) was added. Using isotopic mass bal
 ance we quantified NO3––N contribution to mixed plant nutrition from natur
 al soil and artificial NO3– sources. All grasses and sedges (with exceptio
 n of Festuca varia) demonstrated lower NO3––N uptake (20–40%) relative to 
 all other species of corresponding community (40–60%). Decrease of leaf &#
 948\;15N following treatment with 15N depleted NH4+–N (&#948\;15N = –8.0‰)
  was less pronounced. Significant &#948\;15N decrease was observed for gra
 sses and sedges only\, indicating the preference of grass and sedge alpine
  species to NH4+–N uptake. However\, the experiment with simultaneous NH4+
  and NO3– addition confirmed these results only partially. Our results dem
 onstrate that &#948\;15N of alpine plants may reflect the &#948\;15N of so
 il N sources to some degree.
DTSTART;TZID=Europe/Berlin:20090423T161500
DTEND;TZID=Europe/Berlin:20090423T174500
SUMMARY:Prof. Dr. Mikhail Makarov\, Soil Science Department\, Moscow State 
 University: 15N natural abundance in soil-plant systems of the alpine comm
 unities in the Northern Caucasus
TRANSP:TRANSPARENT
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