ENDINS, n.' 13.1987. Ciutat de Mallorca. |
ADAPTATION OF THE KARST LAND FOR
THE AGRARIAN USE IN THE MEDITERRANEAN.
PROBLEMS OF RESEARCH
AND OF CONSERVATION (A SURVEY)
by lvan GAMS *
En aquest article es revisen els següents rnetodes de recerca:
1. Analisi de la part superior dels aflorarnents rocosos. En esser tallats a nivell del sol, la terra
s'ernprava corn a prat. Quan els tallaven rnés arnunt, la terra s'ernprava corn a terreny de pastura o
corn a prat. En el darrer cas, empero, si la superficie rocosa és Ilisa, el nivell del sol ha estat rebai-
xat per I'erosió; aquest tipus de superficie nornés es pot formar en contacte arnb el sol. La superfi-
cie d'una calcaria compacta, exposada a la corrosió causada per les precipitacions i per la meteorit-
zació rnecanica per darnunt del sol, és cantelluda, clivellada i aspre.
2. Analisi de les pedres acurnulades per I'horne a parets, rnarges, a la vora inferior de les ter-
rasses a carnps rostos, o enterrades sota el sol en aquestes terrasses o sota els prats. La mesura de
llur volurn i pes, efectuada en algunes illes iugoslaves, ha rnostrat que centenars de quilograrns de
pedaes, en casos excepcionals rnés d'un tona, han estat excavats i trencats per cada rnetre quadrat
de terra (<netejada>>.
3. Les formes corn cocons (Kameniea), xaragalls de dissolució (Rundkarrenl, tubs de dissolu-
ció, solcs de dissolució (Korrosionskehle), i especialrnent els forats de parets Ilises (Kavernosen Ka-
rren), si són trobats a la superficie indiquen una erosió soterrada.
4. Els fragrnents de pedra arnb caires vius deixats en el sol després de metejar)) la superficie
rocosa en alguns carnps representa mes del 10 % del pes del sol. Aixo indica I'extensió de la mete-
jada)), fins i tot quan les pedres rnajors s'han retirat de la superficie.
Els ocasionals analisis professionals realitzats a algunes zones carstiques de la Mediterrania.
han rnostrat que les zones habilitades per ús agricola en epoques antigues eren rnés grans del que
sabiern per la bibliografia. L'epoca de la netejada no és segura i abarca des de I'epoca fenicia
(Malta) als ternps rnés recents.
A rnolts de paisos les rnodernes tecniques agricoles destrueixen les antigues formes de prepa-
ració de la terra per al conreu arnb aixada i cavec. L'article insisteix en la necessitat de I'estudi dels
valors ecologics i historics d'aquests anticc testirnonis de I'esforq dels nostres avantpassats pel pro-
veirnent de rnenjar per llurs vides, i de la conservació d'aquesta herencia natural i cultural.
The following rnethods of research are reviewed:
1. Analyses of the outcropping tops of stones. When cut off at the leve1 of the soil, the land
was used as rneadows. When the tops are cut off in higher position, the land was used as a pasture
ground or as a rneadow. In the latter case, however, the soil level has been lowered by erosion if
the stone surface is srnooth. This can develope only in contact with the soil. The surface of solid
lirnestone, exposed to corrosion caused by the precipitations and by the rnechanical weathering
above the soil, is sharply fissured and rough.
2. Analyses of the stones accurnulated by rnan into walls, side walls at the lower edge of the
slope field terraces, or buried under the soil in such terraces or under the rneadow. Measurernents
of their volurne and weight, rnade on sorne Yugoslav islands, have shown that several hundred of
kilograrns, in exceptional case even more than one ton of stones have been dug out and cut off for
one rn2 of the (<cleared» land.
3. Subsoil forrns, such as kamenitza, solution runnel (Rundkarren), solution pipe, solution not-
che (Korrosionskehle), and especially the rocky holes with srnooth walls (Kavernosen Karren) are,
when on surface, an indicator of the soil erosion too.
Prof., Departrnent of Geography, Universiiy of Ljubljana,
ASkerEeva 12, Yu~goslavia.
4. The stone fragments with sharp edges left in the soil after the .clearing)) of the stony sur-
face represent in come field more than 10 % of the soil weight. They indicate the extent of the
((clearing)) even when the bigger stones are removed from the surface.
The occassional professional analyses, rnade so fare in sorne Mediterranean karst areas. have
shown rnuch larger adapted areas for agrarian use in ancient times than this is known in the litera-
ture. The time of clearing is uncertain and reaches from the Phoenician (Malta) to the recent time.
In rnany countries the modern agricultura1 techniques, destroy the old forrns of land adaptation
for the cultivation by hoe and spade. The article stresses the need for the study of the ewlogical
and historical value of these old evidences of the ancient endevour of our ancestors to provide food
for their life and for the conse~ation
of this natural and cultural heritage.
Forrns of adaptation and research problerns
2. Smooth stone surface formed in contact
described here are not lirnited to the Mediterra-
with soil and rough one formed i n the open air.
nean karst countries only. The results reported
The surface of lirnestone, formed by corrosion
here are limited to this area because the author is
of the precipitated water and (or) by the mechani-
more acquainted with it.
cal weathering, is sharp and rough. On both sides
First a brief review of the research methods.
of the top ridge of some stones Reggenkarren oc-
1. Cutting off the tops of the stones sticking
cur. Contraty to that the surface of the compact li-
out frorn the land surface.
mestone below the soil cover is smooth. It is
Surface of the stone cut off is more rough than
smooth even in case the pebbles are thin and na-
the natural one and this difference ir: noticeable
rrow. This difference has becorne more obvious,
even after rnany hundred years. In the northwes-
especially when the soil around the same stone
tern part of the Dinaric Karst in Yugoslavia and on
sticking out from the surface has been recently re-
the Adriatic islands, where a larger part of the re-
moved in the lower level. The fresh surface that
sults reported here is derived frorn, the stones cut
has recently been unearthed is lighter because the
off appear mostly on the pastures. This kind of cut-
old one is darker due to the lichen and microorga-
ting presurnably occurred in the transition time
nisrns. The calcite inlayers are more resistant to
frorn goat and sheep grazing to cattle grazing. The
the corrosion and less to mechanical weathering.
stories cut off appear also in the forests that have
Therefore under the soil the salients, sticking out
occupied the abandoned pastures.
from the stone surface, are forrned, and in the
The stone tops cut off are usually higher than
open air the fissures appear in thern.
the soil surface around thern. But originally they
There are sorne exceptions in the mentioned
have been mostly cut off on the level o f t h e ground
rule. The surface of the homogeneous limestone
nearby. The present difference in the height can be
becornes smooth also under the snow cover if it
considered as an effect of later soil erosion. But
lasts until sumrner (in the alpine belt). In the dense
this rnethod is useful first of al1 when the stones
deciduous forest the dead leaves and from them
cut off appear in a larger area.
derived humus cover the larger massive stones
The big Karren prove with their srnooth stone surface
their subsoil forrnation. The top Regenkarren (solution
flutes) generated later after the soil was washed away
due to the agrarian land use (Trieste Karst near to the
Photo by l. Gams.
sticking out from the ground and form the smooth
stone top surface high above the ground.
3. Smoothness of the surface of the stone
has been diminishing in hundreds of years, but the
proper origin of the initial surface still can be re-
cognized after a long time. It is often accompanied
by special stony forms as solution pans from
which on the surface kamenitzas can be develo-
ped, as well as covered solution runnels (Rundka-
rren), solution pipes, solution notches (Korrosions-
kehlen), covered bogaz, filled funnel-like doline, fi-
lled pothole (Garns 1971, 1976, Jennings 1985). The
most important of them is the hole (Kavernosen
Karren) with smooth walls which can penetrate the
whole stone mass.
When estimating the soil erosion rate by
means of the two mentioned methods one has to
take into account that the sunshine after the defo-
restation reaches the ground and accelerates the
photochemical weathering of the top humus soil
horizon. This and leaching (eluviation) downward
after the decay of the roots cause the lowering of
the soil level, too.
4. Analyses of the anthropogenic stone accu-
Photo 2. Side-walls and cultural terraces in the Adriatic island
mulations on the karst surface.
LoSinj, near to the town Mali Loginj where in sorne
The stone accumulations typical of the proper
plots more than 1.000 kg/rn2 of cut off and accurnula-
Mediterranean karst are a by-product of the clea-
ted stones have been found.
ring of the land for different, mostly for agrarian
Photo by l. Gams.
land use. The karst is characterized by the thin inte-
rrupted soil cover with stones sticking out from the
put on the rocky base along the lower edge of the
surface and by deep soil pockets in the fissures. Ir1
terrace and with the rest of pebbles the vertical
the natural circumstances such a karst surface is
side-walls has been built. The new arable land in
suitable only for pastures of sheeps and goats. Cut-
the terraces has essentially less inclined surface.
ting off the stones on the surface makes possible
b) At the clearing of the karst surface the rocky
t o cut down grass with scythe. For tillage it was
trenches with thick soil have been unearthed. After
necessary the stones to be removed 15-25 cm be-
the pebbles had been deposited there the rocky
low the arable land surface.
surface was covered evenly with soil. c) The stones
Forms of the accumulated stones are different
cut off on the doline slopes have been thrown in
and typical of regions. Stones can form irregular
the trenches excavated in the bottom. Then al1 the
heaps or elongated rows. Systernatically so called
available soil stripped off from the slopes was
dry walls or karst walls are built. If the pebbles are
spread in the bottom to get a larger field (see
compounded of one serie, the width of wall is the
sketch). d) The fragments of broken stones derived
same as the length of pebble. Larger are the walls
from clearing were left in the soil. Their weight ta-
with two series of pebbles. Some of them have the
kes 10 or more percent of the soil weight. These
inner part between two series filled up by minor
fragments prove the clearing in case al1 accumula-
particles. The accumulations are seldom in form of
ted stones were removed from the surface.
quadrangular tower of pyramidal elevations. ln the
5. lnstead of cutting the stone there it was
past centuries the stone accumulation has been in
possible to make the soil thick enough with trans-
some places removed or concentrated in big for-
portation it from near places. Near to these plots
mations to get more cultivated land. The stones
the unearthed stones are today usually the highest.
cut off have also been used for buildings, roads,
Deep trenches and dolines have also provided the
lime-kiln, they have also been thrown in the potho-
soil for transportation. It is proved by their unnatu-
les, chasms etc. A part of them had been buried
ral forms. The soil was seldom stripped off from
under the soil what was proved by bore-holes and
the whole nearby slopes and thus made infertile
excavations (Gams 1973, 1974, 1977). The buried
(example NW of St. Julians on Malta). The differen-
pebbles have been found: a) In the lower belt of
ce in soil structure in the doline bottom and around
the so called cultural terraces. When constructing
it is also an indicator for transportation (Lovrenriak,
them on the inclined surface the rubble has been
Some forms of the alteration of karst surface due to cultivation:
Forms of accurnulated grave1 (pebbles) collected at the process of
a - natural surface, b - alterated and cultivated surface.
1 - Field terraces on slope in semicovered karst. 2 - Alteration
4 - Heap of stones. 5 - Heap of stones arranged in a series. 6 -
of the more funnel-shaped doline into the more bowl-like doline
Wall built in one series. 7 - Wall built in two series. 8 - Wall built in
to get a larger acre on its bonom. 3 - Alteration of the semicove-
two series with inner filling. 9 - Quadrangular tower (from: Gams,
red karst into the covered karst in a meadow.
Form of accumulated stones used for temporaty dwe-
lling of peasant on the field near Stari grad where come
side-walls still indicate the Greek field parcelling from
the 2th centuty b.Ch.
Photo by l. Gams.
6. Historical development of the adaptation
suring the weight of excavated stones. The rneasu-
of karst surface.
red volume of al1 the stones accumulated on the
The knowledge of it in single countries and in
surface can be diverted (specific weight 2,7-2,8, va-
the whole Mediterranean world is deficient, the
lue diminished by factor about 0,2 due to empty
historical sources scarce and human rnernory lost.
voids between the stones) into weight. This kind of
For example: The Polyglot guide-book entitled
measurements showed mainly less than one hun-
«Malta» reports that the Phoeniciens (there from
dred kg/m2 of land from where the stones had
14th-18th century b.ch.) ((brought the fertile soil to
been taken away. On the Yugoslav islands in the
Malta, covered the nacked rocky surface with it and
Adriatic sea this value rises to many hundreds
so acres, vineyards and cotton plants were introdu-
kg/m2 and in some exceptional cases (LoSinj, -
ced)) (p. 8). The preliminary research showed that
Gams 1974, 216) more than 1000 kg/m2. Invisible
in this limestone countty the soil had in reality
stones under the soil and those in the soil were
been derived from the local clearing of stony sur-
neglected. After deforestation the decay of tree
face. It was easy to be cleared due to the light and
roots has lowered the soil level for some centime-
soft limestone. lmportation of the soil could contri-
tres. In case of one thousand kilos of excavated
bute only a negligible share to it. The guide-book
stones the soil level has been equivalently to their
has probably right in cense that the Phoenicians
volume lowered for 21,6 cm. Both factors have
brought the culture of adaptation of karst surface
contributed to the general soil (cerosion)).
already. East of the small town Stari grad on the
The study of alteration of karst surface is im-
Yugoslav island Hvar the Greek parcelling of the
portant for many reasons. It is useful for pedology
field (4th-2nd cent, b.Ch.) still can be seen in the
since the natural soil horizons have been comple-
form of walls. The regular Greek parcelling in «Sta-
tely destroyed and mixed. It can be of great help to
dies)) and ((plethrones)) was possible only in a
the archeological excavations in establishing the
plain area without blocks sticking out from the
natural surface. The alterations have entirely chan-
ground. Today this field is dotted with stones.
ged the ecological conditions. The resilient rubble
Since the Phoenician and.Greek epoches the adap-
in the soil has a better heat conductivity than the
tation has been continued till the present time. The
soil particles. The altered soil is therefore warmer
new agricultural techniques brought also new
in summer. If the pebbles are lying below the soil it
adaptations and consequently the changes in culti-
is more arid and colder rain provokes a smaller re-
vation of land using hoe, spade, later plough, and
duction of the soil temperature. The inwalled plots
recently tractor. A deeper clearing of stones was
have a reduced wind speed and therefore a higher
necessary when the olive-trees replaced the fig-
daily maximal air temperatures. The walls hinder
trees and later vineyards. Therefore the stones had
the gliding of near-to-surface cool air layer on the
t o be cut off down to the depths of 80-100 cm.
slope. The karst depressions with the walls are the-
Every country has his own historical development.
refore warmer in winter. The walls hinder the soil
The walls in Pennins (England) were mainly built in
erosion and also spreading of forest and grass fi-
the transition from feudal to private land tenure - it
res. But in the same time the soil of cultivated land
was in the 17th and 18th century (Raistrick, 1969).
without any grass on the surface is more liable to
The amount of work for adaptation of the karst
soil wash and vertical leaching. Peasants often say
land for agricultural use can be elucidated by mea-
the stones «grow)).
Beside the ecological advances of cultivated
land also some difficulties are to be found there.
The walls hinder the traffic and cultivation of land
GAMS. 1. (1971): Podtalne kraSke oblike (Subsoil karst forms). Geo-
by means of al1 kinds of machines. They also hin-
grafski vestnik XLIII, Ljubljana.
GAMS. 1. (1973): A new method of determining of the karst soil
der the creation of larger fields to be possessed by
erosion. Proc. 6th Int. Congress of Speleology, Olornouc 1973,
one farmer only. For this and the other reasons the
CSSR Il.t., Praha.
agrarian use of the altered karst land is on the de-
GAMS. 1. (1974): Kras. Ljubljana.
crease in modern time. The intensive use is more
GAMS, 1. (1976): Forrns of subsoil karst. Proc. 6th Int. Congress of
and more limited to the vicinity of the settlements
Speleology, Olomouc 1973, CSSR, Il.t., Praha.
GAMS. 1. (1977): Einige Arten der Umwandlung des halbbedeckten
and to less inwalled and less inclined plots, that
Karstes durch die landwirtschaftliche Bebauung. Proc. 6th Int.
are mostly on the bottom of the depressions and in
Congress of Speleology, Olornouc 1973, CSSR, Praha.
the valleys. But the ancient agricultural land is
JENNINGS, J.N. (1985): Karst Geomorphology. Oxford.
being rapidly destroyed there by the traffic, roads,
LOVRENCAK, F. (1977): Odeja prsti v vrtawh Slovenije (Boden-
decke in den Dolinen Sloweniens). Zbornik X. jub. kongresa
railways, and by the other non-agrarian activities.
geografa Jugoslavije u Srbiji 1976. Beograd.
The inwalled plots seems to be incompatible with
MALTA: Polyglott-Reiseführer. München.
the modern agrarian techniques. But with the de-
RAISTRICK, A. (1969): Pennine Walls. Clapharn.
cay of nearly one thousand years old cultural karst
land the cultural heritage would be most affected.
Thus an evidence of the year-long endeavours of
our ancestors for their life and food should be lost.
At least some samples should be conserved for our
future generations. From this point of view we
have t o register the dying forms of cultivation, the
remnants of human knowledge, and the effects of
alterations before the agricultural land of new set-
tlements is utilized and new techniques with trac-
tor and harvester used.