SUCCESSION PATTERNS ON MOUNTAIN PASTURES*

G. SPATZ

Lehrstuhl ffir Griinland lehre, Technische Universitfit Mfinchen D 8050 Weihenstephan, W. Germany

Keywords: Gradient, Mountain, Pasture, Pattern, Succession

Introduction

Land use is troublesome and seldom pays in mountain

regions. Large areas of formerly grazed grasslands were abandoned in the past. Pasture vegetation changes rapidly as soon as cattle, the acting agent, had disappeared.

Material and methods

The influence of management changes on the vegetation of alpine pastures was studied in the Valley of 'Gastein'

in the Austrian Alps. Four subdistricts within the central alpine mountains 'Hohe Tauern' were investigated. Suc- cession was studied from an altitude of 1700 meters up to 2500 m above sea level. 'Stand-structure analysis' (Mueller-Dombois & Ellenberg 1974); 'point quadrar method (Levy & Madden 1933) and direct gradient

analysis (Whittaker 1967, Spatz 1975) were applied.

Results

How much the vegetation of the studied area was in-

fluenced by man in the past can be shown by analyzing the vegetation along a soil nutrition gradient.

Fig. 1 reflects the situation of a gradient beginning immediately below a stable, where soil nutrition is plentiful, and ending in a dwarf shrub heath covering a very poor and highly leached soil. The gradient extends no more than 90 meters.

Fig. 1. Above ground phytomass of species along a

* Nomenclature follows: F. Ehrendorfer. 1973. Liste der Gefaszpflanzen Mitteleuropas. 2. erw. Aufl.

nutrition gradient (Zitterauer-Alm, elevation 2000 m). Below the hut Rumex alp&us forms a highly productive

and dense thicket suppressing almost any other plant species. In the still eutrophic oortion some 20 m away from the source of nutrients Deschampsia cespitosa and

Ranunculus aconitifolius achieve a high biomass. At a distance of 60 m Nardus stricta and Festuca rubra,adapted to poor soil conditions, occur and soon dominate. Finally at a distance of some 80 m, nutrient intake has stopped, and

according to very poor soil conditions a dwarf shrub heath developes. The species diversity is very low at the

eutrophic side of the gradient, it increases at the middle

part, and declines again at the distrophic end. It is obvious that the patterns of succession are highly dependent on the kind of existing vegetation. Some possibilities are being illustrated in the following text.

a) Succession on a formerly mown meadow with 9ood soil nutrition (1900 m a.s.1.)

The mowing of a meadow is an anthropogenic factor which keeps the vegetation in a labile balance. As soon as mowing is abandoned, the species composition of the meadow rapidly changes. The situation .was analysed in a

meadow dominated by tall grasses and Alnus .viridis saplings. This meadow was mown for the last time about four years ago . The AInus saplings were counted and measured on an area of 250 m2. The result of the structural analysis is shown in. Fig. 4. An almost even aged stand of alders has been growing up.

Fig. 2. A stand of Alnus viridis of almost the same age has grown up and will form a dense shrub within a few years (Zitterauer-Alm 1900 m a.s.l.)

Forest trees are not able to invade the place before the

alder stand, which consists of trees of the same age, will

Vegetatio vol. 43: 39~,1, 1980 39

100- ~o

go"

80- )0

70.

60-

S0-zo

40.

30" t0

20"

10"

0

o.

RUMEX ALPINUS

o ~, ~ g e C ~ j ~ ' " ~ ~

oo o%.i \ ~ , DESCHAMPSIA CESPITOSA RANUNCULUS ~ . o ~ . ~ \ ~ . ~

~ VACCIN[UM

. . i • i • i • t • i . i . i . i

3 s 10 Is 20 zs 30 3e 40 ~6 50 ss 60 63 70 7z 80 e6

distance from the hut [m]

Fig. 1. Above ground phytomass of species along a nutrition gradient (Zitterbauer-Alm. elevation 2000m)

become senile and breaks down. K6rner and Hilscher

found out in the same area, that alders become senile at an

age of 60 years an then suddenly die.

b) Succession on a secondary dwarf shrub heath below the

tree line (1900 m a.s.1.)

A secondary dwarf shrub heath which was grazed only occasionally in the past was analysed too. This vegetation

type has developed from a Pieeetum subalpinum during

6 O

o so

_~ '°

~ 2o. o l Z

~ ~o

1-10 11-20 21-30 31-t.O ~ I - S 0 51-60 61-90 "/1-80 81-90 gl-lO0 SIZE CLASSES [CM]

Fig, 2. A stand ofAlnus viridis of almost the same age has grown up and will form a dense shrub within a few years.

the years of extensive grazing. At the time of analysis it was obvious that succession towards a forest, had already

started (Fig. 3). Fig. 3. Results of a structural analysis of a formerly

extensive grazed secondary dwarf shrub heath (1760 m

a.s.1.) Picea abies, the main climax tree, and Sorbus aucuparia

are represented mainly, in the lower size classes. They obviously invade this instabile vegetation type. Alnus

vMdis has become senilein this stage of succession.

Only a few specimens in the higher size classes are still

alive.

c) Succession in a dwarf shrub heath with Rhododendron

ferrugineum near the timber-line (2200 m a.s.1,)

Near the tree line dwarf shrubs with Rhododendron

ferruoineum and Pinus mugo form the climax vegetation together with the trees Pinus cerebra and Larix decidua.

Picea abies is close to the boundary of the area where it can survive. Pinus cerebra and Larix decidua trees were suppressed in the past by anthropogenic factors like grazing and burning. As grazing was only occasional in the past, this vegetation type was little modified. Since pasturage was given up little has changed. As structural

40

301z0 PICEA ABIES %

,~ . . . . . . ,~-~... ~

<~ 3°1 SORBUS AUCUPARIA ?~. z 0 ~ ~ lo

30 t ..Nus v,.,o,s 20 10

7 7 7 " T - , . • .

2030 tl0 PINUS MUGO

t DIAMETER AT JUNIPERU5 SIBIRICA

1°1" 1 M HEIGHT / (0 ;o ~o Lo so 7o mo ,s0=o~0 ,o zo 30 so tCMl

HEIGHT CM

I MM -'- INDIVIDUAL ~ ALIVE ,.._..:f--'! DEAD Fig. 3. Results of a structural analysis of a formerly extensive grazed secondary dwarf shrub heath (elevation 1760 m)

3dodendrGn ferrugineum

10~

5 10 15

Z t,0

O,S O,S" p

0,1.

11,6,

11,5,

o , 3

11,2 II, I

20 25 30 35 t0 /,5 50 AREA [M 2]

Pinus mugo

Lar ix decidua : 2 INDIVIDUALS O, Irn AND I,Sm HIGH

Piceo ab ies : 2 INDIVIDUALS GF

0,1m AND 3m HEIGHT

SGrbus oueupar io ; I PLANT OF 0,3m HEIGHT

5 10 IS 20 AREA (M2|

Fig. 4. Dwarf shrub heath near the treeline (2200 m elevation). Rhododendron ferrugineum and Pinus mugo are distributed normally over the size classes

analysis (Fig. 4) shows, Pinus mugo and Rhododendron ferrugineum are normally distributed over the size classes. It may be expected that Larix decidua will spread in the future but very slowly. In the investigated area of 500 m 2

only two small trees were found. Succession is quite slow in this relatively stable vegetation and no problem at all.

Above the tree line in the alpine region grasslands were modified only a little by grazing in the past. They redevelop to natural grasslands after cattle has gone.

Summary

Some successional patterns on mountain pastures in the Hohe Tauern mountains, Austria, are described. A close relation with former pasture management is shown. Very clear gradients in the nutritional status of the soil exist from stables towards more remote areas where no nutrients are added. Dwarf shrub or Alnus viridis wood- land vegetation will develop after abandoning pastures, depending on elevation and nutrient status. Above the tree line culturally influenced pastures will rapidly develop to natural grasslands.

References

K6rner, Ch. & H. Hilscher. 1978. Wachstumsdynamik von Gfiinerlen auf ehemaligen Almfl~chen an der Zentralalpinen Waldgrenze der Hohen Tavern. In: Ver6ff. des Osterreichi- schen Masz-Hochgeb. Progr. Hohe Tavern 2, Innsbruck.

Levy, E.E. & E.A. Madden. 1933. The point method of pasture analysis. New Zealand Agric. J. 46: 267-279.

Mueller-Dombois, D. & H. Ellenberg. 1974. Aims and methods of vegetation ecology. I. Willey & Sons, New York, London, Sydney, Toronto, XX + 547 pp.

Spatz, G. 1975. Die direkte Gradientenanalyse in der Vegeta- tionskunde. Angew. Botanik 49: 209-221.

Whittaker, R.H. 1967. Gradient analysis of vegetation. Biol. Rev. 42: 207-264.

Accepted 6 November 1979

41