Effects of fertilization and clipping of Phlomis fruticosa L. on a phryganic ecosystem: the case of Thesprotia, northwest Greece

INTRODUCTION

Plant communities dominated by Phlomis fruticosa L., a semi-deciduous drought-hardy and flammable dwarf shrub of about 150 cm tall (8), are a common vegetation type in western Greece. In Greece, such communities are known as phrygana and they are widespread in areas with long, dry and hot summers and mild and rainy winters (26). They usually grow on dry, rocky and friable soils without active calcium (6).

Physiognomically, phrygana can compare with the coastal sage in California and garrigue in France (18). In Mediterranean type ecosystems, the phrygana are adopted a drought semi-deciduous habit, thus avoiding excessive water loss during the dry period (22). These shrubs have been frequently called seasonally dimorphic (20), (38), (17), (18).

Phryganic communities of Phlomis fruticosa are an important component of livestock farming systems covering up to 47.5% (40,000 ha) of the total rangelands in Thesprotia Prefecture (1). They provide forage and bedding for sheep, primarily and they make productive use of rocky and marginal soils that are unsuitable for field and vegetable crops.

Phlomis fruticosa, however, is unpalatable to farm animals which they consume it tender stems rarely. In places where it gets dense, free movement of sheep becomes impossible and considerable area of valuable grazing land is thus lost (24).

To control this troublesome species and to, consequently, increase the grazing capacity of the phryganic rangelands, shepherds have been using fire for a long time. However, the fires set by those people are uncontrolled and usually have more harmful than desirable effects (23).

In Greece, application of fertilizer on mountainous rangelands was been taken place until 1980 decade in order to increase rangeland production. However, it results in unfavourable environmental impacts (mainly pollution of surface and underground waters) because of the high rainfall in combination with the calcaceous soil substrates of regions where it was applied.

Fertilizer application can improve productivity by affecting forage yield, botanical composition, earliness of spring growth and quality. The application of N and P generally alters species composition and increases dry matter and crude protein yields (25), (12), (3), (34), (2). Other studies, although, have reported that annual fertilization resulted in lower above-ground biomass and tiller density after 3 years (13).

On the other hand, the native pasture ability to sustain animal production is up to their production and nutritive value of pasture (34). Variations in rangeland production are reflected in animal performance (7). In the native phryganic pasturelands, it is important to find out alternative methods by which production can be economically increased without causing unfavorable environmental impacts.

The objective of this research was to study the effects of annual, low-level N and P fertilization and clipping of Phlomis fruticosa on above-ground biomass production, crude protein content of forage, seasonal rain use efficiency, nutrient use efficiency and grazing capacity in Thesprotia rangelands.

MATERIALS AND METHODS

This study was conducted at Karvounari (lat 39.3661[degrees], long 20.4926[degrees], elevation 380 m) Thesprotia Prefecture, north-west Greece between February 2004 and July 2006. The climate is temperate-warm. Mean monthly temperature range from 8.7[degrees]C in January to 26.4[degrees]C in July. Mean annual rainfall for 1951-2001 was 1.344,9 mm (SD = [+ or -]286, 6) with nearly 36.2% occurring during the growing season (February to June) (36). Soils are calcaceous with pH, 7.1-7.8, insufficiently provided in N, P and K. Geologically, the plain belongs to the Ionian geotectonic zone. The basic substrates are dolomites, Viglas limestones and flisch (27).

The botanical analysis of experimental area based on frequency of occurring in sixteen quadrates, each equals 1 [m.sup.2], in May 2004. The number of taxa was found to be 192: 33 legumes, 38 grasses and 121 of other families.

The most dominated legumes found in the area are the following: Anthyllis hermaniae, Medicago minima, Medicago lupulina, Trifolium arvense, Trifolium campestre, Trifolium purpureum, Trifolium subterraneum, Trifolium repens, Vicia cracca, Vicia villosa and Vicia pubescens; while the grasses are: Avena sterilis, Briza maxima, Bromus sp., Cynodon dactylon, Dactylis glomerata, Hordeum crinitum, Hordeum murinum, Melica ciliate, Phalaris sp., Phleum pretense and Stipa bromoides; and others species are: Cistus incanus, Crepis sp., Convolvulus arvensis, Knautia sp., Geranium molle, Teucrium polium, Stachys germanica, Micromeria Juliana, Phleum pratense, Asphodelus albus, Asparagus acutifolius, Plantago bellandii and Galium verum.

In February 2004 four 50x70 m study areas was selected and treatments randomly assigned to 4 plots within each of 4 blocks. Each treatment plot was 11.5x16.5 m with a distance between plots of 1 m. Treatments were repeated on the same plots for 3 years (2004, 2005 and 2006).