MOUNTAIN MEDITERRANEAN LANDSCAPE EVOLUTION CAUSED BY THE
ABANDONMENT OF TRADITIONAL PRIMARY ACTIVITIES: A STUDY OF
THE SPANISH CENTRAL PYRENEES.
Teodoro Lasanta-Martínez*, Sergio M. Vicente-Serrano** and José Mª Cuadrat-Prats***
* Instituto Pirenaico de Ecología (CSIC). Campus de Aula Dei. Apdo. 202. 50015. Zaragoza. Spain e-mail: fm@ipe.csic.es
** Centre d'Etudes Spatiales de la Biosphère (CESBIO). 18 avenue. Edouard Belin, bpi 2801,
31401 Toulouse cedex 9, France
*** Departamento de Geografía y Ordenación del Territorio. Universidad de Zaragoza. C/ Pedro
Cerbuna 12. Ciudad Universitaria. 50009. Zaragoza. Spain. e-mail: svicen@posta.unizar.es and jmcuadra@posta.unizar.es
Abstract:
This paper analyses changes in plant cover in a valley of the Spanish Central Pyrenees during the second half of the 20 th
C. The role played by the extensification of farming activities in this process has been examined. The method used was based on evolutionary mapping of the plant cover, application of landscape indices and spatial analysis of livestock pressure. Throughout the century the stocking rate in the valley has decreased dramatically and sheep have been replaced by cattle. Most crop areas have been abandoned, and these areas have gone through a revegetation process (involving both natural vegetation and forest plantation). Nowadays the forest is the most abundant element. The study shows that both agricultural set-aside and the stocking rate decrease have led to a more natural landscape. Finally, the positive and negative effects of extensification and the changes in vegetation patterns associated with it are debated.
24

Key words: Landscape evolution, extensification, land use changes, stocking density,
Pyrenees, Spain.
1.
INTRODUCTION
Since the middle of the 20 th century the Spanish Mediterranean highlands have gone through profound changes on their demographic structure, social organisation and usage of space by humans. Literature distinguishes clearly between two systems of land management: the traditional system and the recent type (Anglada et al., 1980; Lasanta,
1990; Frutos et al., 1996). The first one is characterised by great complexity in its organisational schemes, in order to use all resources and so, be able to support a large human population and a large herd of livestock. This is framed within a system of very restricted relationships with other space. The recent system, on the other hand, sets up very dynamic interactions with the outside world, but greatly simplifies the relationships within the areas forming its territory. That is, it intensifies the most fertile and better-connected areas, while it leaves aside those less profitable, which are used very extensively (García-
Ruiz, 1990; García-Ruiz and Lasanta, 1990).
The change in land management has resulted in very important transformations in the landscape, characterised by the spread of natural vegetation, both forest and bushland
(Ubalde et al., 1999; Gallart and Llorens, 2003; Poyatos et al., 2003; Vicente-Serrano et al.,
2004). Knowledge of the spatial and temporal patterns of such process has great socioeconomic interest; related to potential and the quality patterns of grazing and forest resources. It has also environmental interest; related to location and access to the streambeds of sediment sources, runoff production and quality, risk of fires. And finally, it has interest from the landscape perspective related to; diversity, patchiness and structure of
25

the plant landscape, aesthetic quality and tourist attractiveness (Wickham et al., 2000;
Nagendra et al., 2004).
This paper studies the changes on the plant cover during the second half of the 20 th
century in a valley of the Spanish Central Pyrenees. The Borau valley is a representative example of the twenty-century changes in the Pyrenees: depopulation, abandonment of agriculture and decrease of livestock number. Moreover, the tourist activities are scarce in this valley, and the landscape transformations are only related to internal management changes. It attempts to explain the way in what management affects landscape dynamics when there is a change from an intensive land use, based on farming activities, to the extensive use of larger areas.
The plant cover or the plant-land use mosaic is the landscape component most sensitive to changes in the environmental conditions or due to man’s actions; consequently, it is the key variable usually studied on landscape analysis (Bernáldez, 1981; Forman, 1995; Perry,
2002).
2. STUDY AREA
The study was conducted in the Borau valley, Spanish Central Pyrenees (Fig. 1), where a significant process of abandonment of the traditional land use practices has occurred. It is a small valley (4,186.2 ha.) crossed by the river Lubierre. It has a northerly-southerly direction, like the rest of the Pyrenean valleys. The altitudinal gradient is considerable, the lowest point being 840 m. and the highest one 2,566 m. There are two large relief units: the calcareous inner ranges and the flysch ranges (alternating marls and sandstones), rising closely in the south. The latter sector occupies a larger extent, a homogeneous area with rounded hilltops and smooth hillsides with slopes ranging from 20% to 60% (Soler-
Sampere and Puigdefábregas, 1972). In the flysch area active geomorphological processes
26

continue, mainly in the forms of overland flow runoff and rills; and landslides develop on steeper slopes (García-Ruiz and Puigdefábregas, 1982).
The area has a Mediterranean mountain climate with certain continental influence.
Precipitation reaches 800-1000 mm p.a. on the valley bottoms and immediate hillslopes, and more than 2,000 mm on the highest areas. Rainfall is concentrate in spring and winter, with relatively dry summers. Average annual temperature is 10º C, but differences between months are important. In January the mean temperature is 2.3 ° C and in July is 19.1° C.
The 0º C isotherm during the cold season (November – April) is located at 1,650 m.
(Rijckborst, 1967; García-Ruiz et al., 1986).
The potential vegetation establishes two communities: the montane community, between
800 and 1,800 m. high, where Quercus pubescens prevails on the sunny slopes and Pinus sylvestris on the shaded ones between 1,200-1,800 m. of altitude. Above 1,800 m. there is a subalpine community with a prevalence of Pinus uncinata (Rivas-Martínez, 1987;
Chauvelier, 1987). Both plant communities were very much affected by human actions, that deforested both the sunny hillsides to be put into cultivation and the upper forestland to expand summer pasture lands. Scrublands with Echinospartum horridum and small forests of Pinus sylvestris prevail in the montane community nowadays, while summer pasturelands develop on the subalpine community. The most representative species being:
Trifolium alpinum, Festuca rubra, Nardus stricta, Carex montana and Festuca eskia ,
(Remón, 1997).
3. METHOD
The cartographic analysis of the plant cover was produced for four different dates: 1957 – this was the date when the first aerial photographs was available –, 1978, 1990 and 2000.
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Analysis was based on fieldwork and aerial photographs interpretation from 1957 (scale
1:32,000), 1978 (scale 1:18,000), 1990 (scale 1:20,000). The year 2000 cartography was based on field work and redrawing 1990 cartography. Twelve categories can be distinguished: 1- pasture above timberline, 2- pastures above timberline with scrub, 3- dense forest, 4- open forest, 5- reafforested areas, 6-open scrub, 7- dense scrub, 8- abandoned fields with open scrub, 9-abandoned fields with dense scrub, 10- cultivated plots
(cereal and grassland), 11- bare rock, 12- populated areas.
Map production involved the use of Geographical Information System (ArcInfo, 7.04), which allowed depiction of plant cover evolution between 1957 and 2000. A database for every year was developed to estimate various landscape indices: partial and global stability, dominance and landscape geometry. The landscape indices are used to quantify landscape pattern to reflect the ability of landscape to support certain ecosystems and under such point of view, landscape pattern is an integrative measure of an ecosystems ability to provide habitat, prevent environmental degradation and support other natural processes functions
(Geoghegan et al. 1997). The formulation of landscape indices used is:

Landscape stability : The index is used to distinguish between landscape categories that have gone through important changes and those other categories with minor transformations. This index has been produced for every category (Rosenfield and
Fitzpatrick-Lius, 1986; Duguy, 1998) and for the whole territory. It is estimated by the following equation:
E

( a i

( b i
 c i
))
( b i

( b i
 c i
))
E = stability index a i
= area where category i coincides in 1957 and 2000
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b i
= category i area in 1957 c i
= category i area in the year 2000
The estimation of the Landscape Global Stability was based on the stability of each particular category:
Et =
( A BC )
1 BC )
Et = Total stability
A
 i c  a i

1
BC = i c 

1 b c i
This index ranges between 1 and –1, which allows comparing different spaces. If E = 1, both covers overlap totally, both for each category and the global. If E = -1 there is no overlapping between both covers. If E = 0 all changes may be due to chance.

Landscape dominance : An index based on Shanon-Weaver’s information theory has been used for each time period (Shanon and Weaver, 1962):
D

H max
 m  i

1 p i p m = number of land use categories in the study area. p i
= proportion of category i in the study area.
H max = 1n (m) = maximum diversity when all uses are present on the same proportion.
The higher the indicator values are, the greater its role in the landscape.
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
Landscape geometry index (fractal dimension = F), assesses landscape complexity in relation to the complexity of the patch set perimeter (Mandelbrot, 1983; Kienast, 1993).
To conduct this analysis the perimeter-area method has been used. The fractal dimension is estimated by the regression of 1n (A) against 1n (P/4), for each landscape type on the map.
The fractal dimension is calculated according F = 2m, where m is the slope of the regression adjustment equation between ln (A) against ln (P/4), (Lovejoy 1982). A is the area and P the perimeter of the patches.
Anthropogenic management in the valley during the second half of the 20 th
century has been based on livestock activities. In order to know the stocking rate in each area, information about livestock censuses (livestock type and number of heads) was collected from state offices, and both cattle and sheep grazing areas and the stocking rate in each area were determined (View details in Vicente-Serrano, 2001).
Figure 2 gives an average annual summary of the stocking rate of cattle and sheep in the period 1957-2000. The values have been estimated by the product of the stocking rate and the number of days the animals have been grazing for: ((cattle equivalent/ha) x days on pasture).
The impact of livestock activities on the plant cover was estimated by a Predictive
Discriminant Analysis (PDA), where changes on the plant cover were also related to topographical variables.
PDA is used to explain the value of a dependent categorical variable based on its relationship to one or more predictors (Huberty, 1994). Given a set of independent variables, PDA attempts to find linear combinations of those variables (topographic and livestock variables) that best separate the groups of cases of the dependent variable. These combinations are called discriminant functions (Hair et al. 1998). The procedure
30

automatically chooses a first function that separates the groups as much as possible. It then chooses a second function that is both uncorrelated with the first function and provides as much further separation as possible. The procedure continues adding functions in this way until reaching the maximum number of functions as determined by the number of predictors and categories in the dependent variable. The PDA allows the determination of which predictor variables contribute to most of the inter-category differences of the dependent variable. The SPSS software was used to carry out the PDA. The dependent variables were selected according to temporal evolution of vegetation cover between 1957 and 2000.
4.
RESULTS
4.1 - ABANDONMENT OF TRADITIONAL LAND USE
In this area the traditional organisation of space was based on the maximum use of all resources available in the framework of a management system that was very dependent on local resources. Most of the roads that joined Pyrenean valleys with the local settlement centres were built at the beginning of the century –between 1905 and 1920- (Pujadas and
Comas, 1975). The arrival of new products and new ideas from the lowlands was the cause for the initial change of the Pyrenean rural society and the transformation of traditional land use. After the 1950’s and 1960’s the definite incorporation of the highlands in the national market was much more obvious, and this increased the exchange of products and promoted the specialised production in the valleys. It was at this time that it became clear that there were lesser possibilities for highlands to enter a dynamic and wide market. Evidence of this is shown by a sharp population decline, shrinkage of the farming area and a drop in livestock numbers.
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In 1910 the population of the Borau valley was 460 people, while in 1991 there were just
73 people, a population loss of 84.1%. Along the 20 th
century the population density dropped from 11 inhabitants/km
2 in 1910 to 1.7 inhabitants/km
2
in 1991.
Reduction of the farming area was simultaneous to the population decline. From analysis of
1957 aerial photographs, we estimate that crop fields could have occupied 43% of the land, stretching over most low and medium hillslopes in the valley. This number was estimated from the surface of abandoned lands and cultivated areas in the aerial photographs of 1957.
The first statistical sources are of 1944. In this year only the 14.4% of the whole valley area was cultivated (CSIC, 1944). Set-aside continued on later decades: 9.4% of the land was under cultivation in 1957, 4.9% in 1978 and 1.7% in 1990 –the same as in 2000–.
Consequently, more than 38% of the initially cultivated area has been abandoned. The farming land still under cultivation, all of it grassland, is concentrated on the valley bottom of the river Lubierre and on the nearby hillslopes, while the abandoned fields are located on steeper hillslopes and far from the centres of population.
Traditional animal husbandry relied upon sheep breeding, based on a trashumance system.
The flocks were in the Borau valley in June, July, August and September, while they grazed in the uncultivated and fallow fields in the Ebro Basin, about 150 km. far from the Borau valley (Pallaruelo, 1993; Pinilla, 1995). This system allowed very high sheep numbers, managed in flocks of 2,000-3,000 heads. In the middle of the 19 th century, there were around 21,000 sheep in the Borau valley (Remón, 1997). However the crisis of the migratory system started at the end of the 19 th
century due to decline in the wool trade. It was due also to the promotion of agricultural activities in the Ebro Basin (cultivation of bare fields and expansion of irrigated farming), in contrast to animal husbandry, and finally, to the drop of the number of shepherds. The result was that the sheep census in 1911
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showed less than 7000 head and this number continued dropping through later years. Figure
3 shows clearly the decreasing trend during the 20 th
century. Only in the mid-eighties, there was a slight rise in these migrating flocks thanks to the EU subsidies to this activity (Errea,
1995).
The decline in sheep stock was partially offset by the increase of cattle after 1950 (Fig. 4), as these ones require less labour force and adapt better to their housing than sheep. The increase of cattle, however, did not make up for the losses of sheep, so livestock pressure on the land has had large fluctuations over the 20 th
century from 817.3 livestock units
(cattle equivalent) in 1911 to 337.3 in 1950, 183 in 1980 and 219.3 in 2000.
Livestock pressure decline and the replacement of sheep by cattle have occurred together with changes in the grazing system. Initially pastures above timberline were used in summer while intermediate hillsides (abandoned fields, bushlands and forests) were grazed in spring and autumn. The cultivated area provided cattle and sheep with little food. After the sixties, grazing has been concentrating in richer pasture areas or those ones with easier access for cattle, particularly the lower pastures above timberline and in the cultivated meadows. Medium hillslopes and some sectors in the pastures above timberline are barely grazed, following a similar pattern as in all the Pyrenean valleys (García-Ruiz and Lasanta,
1993). Cattle graze on mountain passes and meadows, while sheep are concentrated on mountain passes and intermediate hillsides, though with a very low stocking rate.
4.2 - LANDSCAPE EVOLUTION ANALYSIS
As a result of the decline of man's pressure on the land, remarkable changes have occurred on land use (Fig. 5).
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In 1957 the abandoned fields occupied 1402.1 ha. (33.4% of the valley area), and was the most extensive land use. Natural forest occupied 1031.8 ha (24.6%). Pastures above timberline ranked third with 805.9 ha. (19.2%). Cultivated areas and bushlands occupied also extensive areas. In the year 2000 the natural forest was the most extensive use with
1948.5 ha (46.5% of the valley area), besides, 322.9 ha. of Pinus sylvestris reafforested after the 1950's must be added to that area. Forestland increased in areas formerly occupied by dense scrub or abandoned fields, whose areas have been decreasing progressively, and, to a lesser extent, in areas formerly occupied by pasture above timberline. Cultivated areas have also been reduced and replaced by abandoned fields, while pastures above the timberline have not changed much (Lasanta et al ., 2001).
Landscape global stability between 1957 and 2000 has been very low, as only 46.3% of the valley area has not changed its coverage between these two dates. Table 1 includes stability values of the different landscape categories. Apart from 'population centre' and 'bare rock' categories, which have not changed their size, dense forest, reafforested forest and pastures above the timberline have been the most stable categories. The rest of the categories have been characterised by their instability: open forest has been a transitional visual category, as the areas occupied by open forest in 1957 generally corresponded to dense forest in 2000, while open forest is found now in abandoned fields. Abandoned fields and bushlands show a high instability level as plant succession tends progressively towards open forest first and to then dense forest.
Table 2 indicates the evolution of landscape structure between 1957 and 2000 according to the number of patches and their total surface in the different categories. Landscape structure in 1957 showed large patches (37.3 ha. as average) but important spatial differences were recorded. It was in the highest elevation areas, where the topography is homogeneous and
34

there are continuous pastures above timberline, and in the abandoned fields with open scrub were the largest landscape patches were recorded (87.3 ha and 67.9 ha. respectively). The smallest corresponded to pastures above timberline with scrub (10.7 ha.) and open scrub
(14.5 ha.).
In 1978 landscape structure was more highly fragmented and heterogeneous than in 1957, patch size going down to 27.2 ha. Open forest, dense scrub and abandoned fields with open scrub are the land uses that have gone through the most significant changes manifest in an increase in the number of patches and reduction in their average size.
After 1978 the trend changes there is a decrease the number of patches and increase in their average size. The most meaningful change is the decline of scrubland (scrubland and abandoned fields) and the expansion of dense forest patches and patches of abandoned fields with dense scrub. In 2000 there are 17 patches of dense forest with an average size of
70.5 ha., while in 1957 there were 16 patches of dense forest with an average size of 34.7 ha. Abandoned fields with dense scrub had values of 4 patches with 113.3 ha. and 19 patches of 23.8 ha. respectively, on the same dates.
The dominance index (Figure 5) confirms what has been pointed out when analysing the landscape structure: it starts from a maximum in 1957 and decreases between 1957 and
1978. There is a change in the trend after 1978, which is weak between 1978 and 1990 but more marked after 1990. However, the value in 2000 is not as high as in 1957, in contrast to the landscape structure. This is because no category beyond the most prevalent category of dense forest stands out for its area. In 1957, however, there was greater balance among the land uses in relation to their area. This space was shared amongst abandoned fields, forests and pastures above timberline.
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Table 3 shows the values of the fractal dimension for the different landscape categories.
The patterns of total values follows the general trend of landscape structure and landscape dominance. The index values have their highest value in 1957 as the landscape units were larger and had a wider perimeter at that time. During the transitional period, when the plant succession process advances (1978 and 1990), the number of patches increases and their size decreases. In the year 2000, as patch size increases, larger perimeters and lower complexity are attained.
Along the second half of the 20 th
century, an important process of plant regeneration occurred, which involved firstly scrub, and then, forest colonisation. Table 4 summarises the changes in plant area between 1957 and 2000. Areas, which have maintained the same land-use between 1957-2000, may be considered as lands that have not experienced any changes. Areas in which the forest has been changed by scrublands or pastures, have been identified as areas with plant cover decrease. Spaces identified as areas with moderate coverage increment are open scrublands and pastures above timberline in 1957 that have been changed to dense scrublands or open forest in 2000; and open forest that have been substituted by dense forests. Lastly, areas with important increments in plant cover are on the one hand, open scrublands or pastures above the timberline substituted by open or dense forests, and on the other hand, dense scrubland by dense forests.
A total of 48.2 % of the land has experienced no changes: the plant cover in 1957 remaining similar in 2000. These areas were mainly pastures above the forest limits, dense forests and pastures. Natural vegetation increased in 45.7% of the land; this includes scrub, abandoned fields and open forests mainly. Plant cover decreased in 6% of the valley. This process took place in very specific sectors such as areas of convex landforms where erosion
36

processes were more prevalent (González et al., 1997) or in areas where the plant cover has been reduced by man, such as small scrub or undergrowth clearing and tree felling.
4.3 - THE EFFECT OF MANAGEMENT ON LANDSCAPE CHANGES
In order to evaluate the role played by man's management, which mainly related to animal husbandry, a discriminant analysis was carried out. This analysis included livestock-type variables (sheep stocking rate and cattle stocking rate). These factors affect pressure due to livestock, such as distance to stables and water points, and topographic variables (slope, altitude and aspect) obtained from a Digital Elevation Model (DEM) of the area, produced by GIS.
Table 5 shows the results of the discriminant analysis, including the first three functions.
The first function accounts for 91.4% of the variance.
Table 6 shows the centroids of each plant cover evolution group. The first function establishes a clear separation between the regenerated areas and those with no changes or those that lost plant cover. This is reinforced by function 2, which shows the same discrimination between evolutionary groups.
Table 7 and figure 6 indicate the role played by each variable on the three functions. The importance of livestock pressure, both by cattle and sheep, in the evolution of the plant cover in the valley must be emphasised. The stocking rate is the main factor that accounts for the plant cover recession as the most heavily grazed areas have been the most affected by this process. The role of cattle is remarkable. It had more effect than sheep in the last half of the century and has put high pressure on pastures above the forest limits and pastures over relatively short time periods (Chocarro et al., 1987; Remón and Alvera,
1987). The analysis corroborates the key roles of extensification and the abandonment of
37

animal husbandry accounting for the plant recolonisation process in the Borau valley. The concentration of grazing in a few highly-intensive areas (pastures above timberline) resulted in livestock controlling the increase of vegetation in those sectors, while the rest of the land has been subjected to little pressure, being left to a natural process of plant succession. Distance to stables and water points had barely any effect in the plant evolution process. As it is a small valley with plenty of water points and streams, cattle need not travel long distances and thus do not concentrate their grazing areas as a result of these factors.
Within the topographic variables, altitude is more important, as it is a valley with a strong altitudinal gradient, resulting in climatic differences between the valley bottom and the high mountaintops. This indirectly affects plant colonisation in the area. Aspect has less influence, as eastern and western aspects prevail and these result in less contrast than southern and northern exposures. Slope has barely any impact, the valley has homogeneous hillslopes.
5. DISCUSSION AND CONCLUSIONS
Along the 20 th
century, the Spanish Mediterranean highlands have gone through changes in their management system. The self-sufficiency system has been replaced by a system characterised by the integration of these highlands into wider and more dynamic territorial, political and economic spaces. Substituting one system by another has changed the socioeconomic function fulfilled by each land unit and, consequently, the land uses and the dynamics of the natural vegetation and landscape.
The need to reach self-sufficiency under the traditional system led to use of all land resources. This involved deforestation and scrub clearing on many hillsides to expand cropping areas and pasture lands. This led to a less natural landscape that showed many
38

features of a highly humanised space. Replacing the traditional management system has been accompanied by the productive intensification of the most fertile areas. These have become enmeshed in a matrix with under-utilised-spaces (García-Ruiz and Lasanta, 1990).
Land use has changed in 52.5% of the area between 1957 and 2000, with a trend towards plant regeneration, shown by an increase of scrubland and woodland. This means that the stability of traditional land use was artificial. It was only sustained by high labour investment. The cessation of this investment of human energy led to fast and important changes in the landscape, thus, harmonising the natural conditions with the plant cover
(Petch and Kolejka, 1993). The process is similar to other European regions in which regevetation is the consequence of land abandonment (Kozak, 2003; Taillefumier and
Piégay, 2003; Torta, 2004).
Intensively used areas, such as cropland and pastures above timberline with easier access and those with a more mature landscape, such as dense forests have not changed. However, very extensively used areas, such as abandoned fields, scrublands and open woodlands have changed.
Some features of the traditional landscape could still be noticed in 1957, in spite of the fact that very important changes had already taken place since the beginning of the 20 th
century, following the abandonment of crop fields and the decrease of livestock censuses.
The largest patches still corresponded to croplands and abandoned fields with open scrub.
Landscape presented a very homogeneous structure, with high dominance and fractal dimension indices. Man has simplified landscape to extract the maximum energy with the least labour investment (Margalef, 1984). In the traditional system, there was no close relationship between the physical conditions and the plant mosaic, but quite the opposite.
This is striking for a mountain area, where great natural diversity is presumed to exist, as a
39

primary vertical gradient overlaps with others related to topography (solar radiation, topoclimate, water and nutrient flows) that shape the conditions of the environment (Barry,
1981; Barrio, 1990). This result contrasts with the traditional trend of classifying mountain landscapes as natural systems, which may overlook that they are areas that have been transformed by society for centuries by farming and forest usage (Bertrang, 1978).
Similarly, the deep transformation of the natural landscape by man helps to break with the idealised view, which so abundant in literature, about how well mountain societies adapt to the environmental conditions (Bernáldez, 1991; McNeill, 1992).
The recent evolution of landscape indices (1990 and 2000) seems to point out a trend towards simplification and homogenisation; manifest in a decrease in fragmentation, with a smaller number of patches and an increase of their average size, and a slight increase of dominance index. Land set-aside and the decline of livestock pressure produces an acceleration in the process of plant succession, initially with herbaceous plants and finally with bushes and forests (Montalvo et al., 1993; Ortega et al., 1997; Molinillo et al., 1997).
The landscape structure has gone through various stages in the temporal dynamics of change. The landscape was more fragmented in 1978 than in 1957. The number of patches had increased at the same time as their size had been reduced. The dominance index and the fractal dimension were lower. The greater landscape complexity is probably due to anthropogenic and environmental factors acting together (Fernández Alés et al., 1992;
Gutiérrez Teira, 1997).
Plant colonisation induces plant homogenisation and invasion by generalist species that lead to a decrease in biological diversity after a few decades (Naveh, 1974; Bernáldez,
1991).
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The expansion of plant cover due to the increase of scrubland and woodland areas (natural and reafforested) contributed to a more natural landscape. This has positive and negative effects from the global perspective of ecological diversity and sustainable development. In relation to the former, we have to consider that reafforested pine forests and natural forests, with no silvicultural practices, tend to have a close and simplified structure. This results in high stand mortality and a local reduction of biodiversity (Perry, 1988). On the other hand, the risk of fire has increased simultaneously with landscape homogenisation. Scrub prevails on the hillsides and in the undergrowth of pine and oak forests, increasing fire risk
(Vicente-Serrano et al., 2001). Likewise, livestock potential in the valley has been reduced, due to the decrease in the number of patches of herbaceous vegetation. This has mainly occurred in abandoned fields (Molinillo et al., 1997). Among the positive effects the decrease of sediment transport in the farming area as compared with the traditional farming related to a better natural regulation of runoff has been significant (García-Ruiz et al., 1996;
Lorente et al., 2000)
ACKNOWLEDGEMENTS
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SPATIAL-TEMPORAL VARIABILITY OF THE PLANT LANDSCAPE IN THE
MEDITERRANEAN HIGHLANDS DUE TO THE ABANDONMENT OF
TRADITIONAL LAND USES: A STUDY OF THE SPANISH CENTRAL PYRENEES.
Figure 1: Location of the study area
Figure 2: Stocking rate (1957-2000)
Figure 3: Evolution of the sheep population (1911-1998)
Figure 4: Evolution of the cattle population (1911-1998)
Figure 5: Land use evolution.
Table 1: Stability index of each landscape category (1957-2000)
Table 2: Evolution of landscape structure (total and particular categories)
Figure 5: Evolution of landscape dominance index in Borau (1957-2000)
Table 3: Evolution of the fractal dimension in Borau (1957-2000)
Table 4: Changes in plant cover (1957-2000)
Table 5: Results of the discriminant analysis
Table 6: Functions of centroids in the plant cover evolution groups (1957-2000)
Table 7: Standarized coefficients of canonical functions of the plant cover evolution
48

Figure 6: Centroids of the evolution groups and the discriminant analysis variables
682500 690000 697500 705000
FRANCE
712500
ATLANTIC
SPAIN
ME
DI
TE
RR
AN
EA
N
ANS O
VALLE DE HEC HO
CAN FR ANC
V
E
R
A
L
N
A
D
R
O
B
U
S
JAS A
AIS A
BORAU
VILLAN UA
L
U
B
IE
R
R
E
G
A
R
A
N
O
JAC A
U
A
IN
R
SAN TA CR UZ DE LA SER OS
682500 690000 697500 705000 712500
5
UTM-30N COORDINATES
0 5 Kilometers
49

Figure 2: Stocking rate (1957-2000)
2
5 15 25 35
0 2 Kilometers
50

Figure 3: Evolution of the sheep population (1911-1998)
0
51

0
Figure 4: Evolution of the cattle population (1911-1998)
52

Figure 5: Land use evolution. 1: Pastures above timberline, 2: Pastures above timberline with scrub, 3: Dense forest, 4: Open forest, 5: Reaforested forest, 6: Open scrubland, 7: Dense scrubland, 8: Abandoned fields with open scrub, 9: Abandoned fields with dense scrub, 10: Crop land and pasture land, 11: Bare rock, 12: Population centre.
0
1 2 3 4 5 6 7 8 9 1 1 1
53

Table 1: Stability index of each landscape category (1957-2000)
LANDSCAPE CATEGORY
1:Pastures above timberline
2:Pastures above timberline with scrub
3:Dense forest
4:Open forest
5:Reafforested forest
6:Open scrubland
7:Dense scrubland
8:Abandoned fields with open scrub
9:Abandoned fields with dense scrub
10:Crop land and pasture land
11:Bare rock
12:Population centre
TOTAL
STABILITY INDEX
0.81
0.32
0.85
0.12
1.00
0.01
0.00
0.15
0.10
0.43
1.00
1.00
0.39
54

Table 2: Evolution of landscape structure (total and particular categories)
LANDSCAPE CATEGORY
Nº. of
1957
Patch patches average size (ha)
8
10
87.34
10.71
Nº. Of
1978
Patch patches average size (ha)
8
8
85.38
13.24
Nº. of patches
1990
Patch average size (ha)
8
15
78.87
9.07
Nº. of
2000
Patch patches average size (ha)
8
15
79.40
9.10
1:Pastures above timberline
2:Pastures above timberline with scrub
3:Dense forest
4:Open forest
5:Reafforested forest
6:Open scrubland
7:Dense scrubland
8:Abandoned fields with open scrub
9:Abandoned fields with dense scrub
10:Crop land and pasture land
11:Bare rock
12:Population centre
Total
16
15
1
8
5
14
19
9
6
1
112
34.66
31.82
27.21
14.56
43.95
67.89
23.77
43.54
31.05
4.88
37.30
7
6
1
151
14
40
2
4
19
17
25
52.03
14.92
158.98
3.13
4.54
33.97
26.45
31.86
31.20
6.43
27.70
17
43
2
10
11
18
9
3
5
1
142
56.27
14.00
162.03
1.03
8.83
23.97
65.22
71.55
37.97
6.37
29.80
17
34
2
3
5
13
4
3
5
1
110
70.52
18.85
162.03
0.69
4.07
28.38
113.28
71.55
37.06
6.37
38.06
55

Figure 5: Evolution of landscape dominance index in Borau (1957-2000)
56

Table 3: Evolution of the fractal dimension in Borau (1957-2000)
Landscape category
F
1957 r 2
1978 1990 2000 r 2 F r 2 F r 2
F
1:Pastures above timberline 1.25 0.99 1.22 0.99 1.28 0.99 1.29 0.99
2:Pastures above timberline 1.42 0.90 1.57 0.83 1.20 0.95 1.19 0.95 with scrub
3:Dense forest
4:Open forest
5:Reafforested forest
6:Open scrubland
7:Dense scrubland
8:Abandoned fields with open
1.15 0.98 1.30 0.98 1.30 0.97 1.32 0.98
1.16 0.97 1.21 0.95 1.24 0.97 1.19 0.96
---- ---- ---- ----
1.04 0.88 0.00 0.00 1.15 0.88 0.00 0.00
1.06 0.96 0.00 0.00 1.17 0.95 1.03 0.94
1.23 0.97 1.21 0.98 1.01 0.94 1.00 0.95 scrub
9:Abandoned fields with dense scrub
10:Crop land and pasture land
11:Bare rock
12:Population centre
TOTAL
1.02 0.94 1.10 0.94 1.17 0.94 1.01 0.96
1.49 0.99 1.59 0.99 1.55 0.98 1.55 0.98
1.16 0.97 1.26 0.99 1.23 0.99 1.27 0.99
---- ---- ---- ----
1.20 0.96 1.08 0.94 1.13 0.94 1.15 0.95
57

Table 4: Changes in plant cover (1957-2000)
EVOLUTION
Important coverage loss
Moderate coverage loss
No changes
Moderate coverage increase
Important coverage increase
TOTAL
COVERAGE IN HA COVERAGE IN PERCENTAGE
27.9 0.60%
224.5
2019.1
942.8
971.3
4186.2
5.30%
48.20%
22.50%
23.20%
100%
58

FUNCTIONS VARIANCE % ACCUMULATE % CANONICAL CORRELATION SIGNIFICANCE
1
2
3
91.4
5.8
1.7
91.4
97.3
99
0.57
0.17
0.09
< 0.0001
<0.0001
<0.0001
59

Table 6: Functions of centroids in the plant cover evolution groups (1957-2000)
Important coverage loss
Moderate coverage loss
No changes
Moderate coverage increase
Important coverage increase
FUNCTION 1 FUNCTION 2 FUNCTION 3
0.38
0.41
0.64
-0.52
-0.94
0.53
0.25
0
-0.27
-0.18
-0.48
-0.31
0.42
-0.56
0.53
60

Altitude
Distance to stables
Aspect
Slope
Distance to water points
Stocking rate (sheep)
Stocking rate (cattle)
FUNCTION 1 FUNCTION 2 FUNCTION 3
0.66
-0.03
0.23
0.13
0
0.53
0.74
0.44
0.55
0.44
-0.07
0.21
-0.55
0.15
0.66
0.31
0.38
0.31
-0.07
-0.07
-0.6
61

1
0
S g s c s l s c w p s s t
S g c e
E t n d t
S g g d e o a d t a g i
0
U O
1
62