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Oecologia (Berlin) (1983) 57:266-269
IC.
Availability of nitrogen and phosphorus in the nival zone of the Alps
K. Haselwandter
1
, A. Hofmann
1
, H.-P. Holzmann
1
, and DJ. Read
2
1
Institut für Mikrobiologie, Universität Innsbruck, Sternwartestraße 15, A-6020 Innsbruck, Austria
2
Department of Botany, University of Sheffield, Sheffield S10 2TN, England
Summary.
In high-alpine soils the maximum temperature
is low even during the growing season, and hence mineral-
isation of nutrients is reduced. The aim of this study was
to investigate what sources of nitrogen and phosphorus are
available for vascular plants in the alpine nival zone to
support growth. Using acetylene reduction assays levels of
nitrogenase activity were assessed in sealed pots containing
nival zone soil and plants at an altitude above 3000 m,
and in bacterial isolates of soil and rhizosphere in the labo-
ratory. Nitrogenase activity could not be detected in bacte¬
rial isolates or in the soil containing no plants. Small quanti-
ties of ethylene (<87 nmol-h"
1
per pot) were detected in
pots with
Cerastium unißorum
and
Poa la.xa.
This activity
must be attributable to rhizosphere bacteria since no evi-
dence for the presence of cyanobacteria could be obtained.
Other sources of nitrogen for the plants were detected
in the form of ammonium and nitrate in soil water and
in snow melt water. These Solutions also contained extract-
able phosphorus in quantities normally considered to be
sufficient for growth. Analyses of the internal concentration
of nitrogen and phosphorus also suggested that these ele-
ments were present in adequate amounts in these plants.
It was considered that soil and snow melt water together
may provide sufficient nitrogen and phosphorus to support
the extremely small annual growth increment of nival zone
plants.
Introduction
In the alpine nival zone only a few higher plant species
grow either as isolated individuals or as small patches of
Vegetation. While some workers (Franz 1979: Larcher
1980; 1983; Moser 1970; 1973) have emphasized the
extreme climatic conditions of the nival zone
little
attention
has been given to the nutritional and microbial interrela-
tionships. Studies of such factors have previously been
carried out only in the lower and hence less extreme alpine
and subalpine zones (e.g. Gökceoglu and Rehder 1977;
Labroue and Carles 1977; Rehder 1976a; 1976b; Rehder
and Schäfer 1978; Tosca and Labroue 1981). Analysis of
the nutrient relations of plants of the nival zone will help
to elucidate the relative importance of nutritional factors
in the limitation of productivity of this zone. In an earlier
study (Haselwandter and Read 1980) it was shown that
mycorrhizal infection in this habitat was poorly developed
Offprint requests to:
K. Haselwandter
relative to that found at lower altitudes but the relationship
between this observation and the nutrition of the host was
not investigated. Since the nival zone is characterised by
mean monthly maximum soil temperatures in the ränge
0.7-6.
V
C during the growing season from June to Sep¬
tember (Moser et al. 1977) it is likely that microbial miner-
alisation of nutrients will be slow. We have therefore exam-
ined the possibility that nitrogen fixing activity might occur
in the soil or rhizosphere of nival zone plants and deter-
mined the levels of the major nutrients nitrogen and phos¬
phorus in soil, snow and in tissues of some of the most
important species of the zone.
Materials and methods
The sampling site was situated at 'Hoher Nebelkogel* in
the Tyrolean Central Alps of Austria (46 59'N 11 4'E. ele-
vation 3100-3200 m) on Ötztal crystalline schist which is
mainly composed of paragneiss. This was the site of an
IBP project in which climatic and plant ecological informa-
tion relevant to the present study had been collected (Moser
et al. 1977).
In arcas of virgin soil recently exposed after snow melt
plants of
Rammculus glacialis, Leucanthemopsis a/pina, Cer¬
astium unißorum, Orcochloa disticha
and
Poa la.xa
grew ei¬
ther as isolated individuals or in patches. Soil, snow and
plants were sampled and in
situ
experimenls were carried
out during the growing season of the years 1978 to 1980.
Isolation of microorganisms and measurement
of nitrogen fixing activity
Vigorously growing plants of
Rammculus g/acialis, Leucan-
themopsis a/pina
and
Poa la.xa
were excavated from soil
at the end of the growing season, and healthy roots of
each species were excised aseptically, placed into sterile
tubes and transferred in a cool box to the laboratory where
they were washed in sterile Ringer' sah solution. Quantities
of appropriate dilutions of the solution were placed on soil
extract agar and a ränge of bacterial isolates were subse-
quently subcultured onto agar slopes of nitrogen-free
Norris" medium (Norris 1959) and maintained for 3 months
at 4' C without further subculturing. The vials were then
sealed for acetylene reduction assays which were carried
out using incubation periods of 4. 24 and 48 h, acetylene
concentrations of 10% and Standard gaschromatography
methods.
//;
situ
assays of nitrogen fixation were also carried out
using acetylene reduction assays in the summer of 1979
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