ALO docView - Availability of nitrogen and phosphorus in the nival zone of the Alps (1983)

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