Weed Research, 1988, Volume 28, 175-180

Floristic composition and agricultural importance of weeds in southern Spain A. PUJADAS SALVA AND J. E. H E R N A N D E Z B E R M E J O Departamento de Ciencias y Recwsos Agricolas, ETS Ingenieros Agronomos de Cordoba, Apdo. 3048, 14080 Cordoba, Spain

Received 22 July 1987 Revised version accepted 4 December 1987

Summary: Resume: Zusammenfassung A survey was made of the agrestal and ruderal flora of southern Spain, mainly in the province of Cordoba, and a total of 941 weed species in 81 families were found in ecosystems showing severe human disturbance. The families with the highest numbers of species were Compositae, Leguminosae and Gramineae; other families like Amaranthaceae, Solanaceae and Oxalidaceae were also important because of their special behaviour as weeds. An assessment of the agricultural importance of the species in terms of the damage caused to crops showed that 36-3% could be considered rare or casual, 15-6% slightly harmful, 14-1% locally harmful, 7-3% harmful, and 26-6% very harmful. The richness of the flora in the different ecosystems is analysed and compared with that in other countries. Composition floristique et importance agronomique des adventices dans le Sud de I'Espagne Une enquete a ete conduitc sur la flore agreste et ruderale dans le Sud de I'Espagne, principalement dans la province de Cordoue, et un total de 941 especes d'adventices de 81 families ont ete trouvees dans des ecosystemes fortement influences par l'intervention des hommes. Les families les etaient les composees les

legumineuses et les graminees; d'autres families, comme les amaranthacees, les solanacees et les oxalidacees avaient egalement de l'importance en relation avec leur comportement particulier en tant qu'adventices. Une estimation de l'importance agricole des especes en terme de nuisances provoquees aux cultures, montre que 36,3% peuvent etre considerees comme rares ou occasionnelles, 15,6% comme faiblement dangereuses, 14,1% comme localement dangereuses, 7,3% comme dangereuses et 26,6% comme extremement dangereuses. La richesse de la flore dans differents ecosystemes est analysee et comparee a ce qui se passe dans d'autres pays. Floristische Zusammensetzung und landwirtschaftliche Bedeutung von Unkrautern in Siidspanien Die Segetal- und Ruderalvegetation in Siidspanien, vor allem in der Provinz Cordoba, wurde aufgenommen, wobei insgesamt 941 Unkrautarten aus 81 Familien in den am meisten vom Menschen beeinflussten Okosystemen gefunden wurden. Die artenreichsten Familien waren die Compositen, Leguminosen und Gramineen; wichtig waren auch die Amaranthaceen, Solanaceen und Oxalidaceen, weil zu ihnen besonders ausgepragte Unkrautarten gehoren. Im Hinblick auf die landwirtschaftliche Bedeutung, d.h. die Schadwirkung, welche die Arten in Kulturpflanzenbestanden haben, konnten 36,3% als selten oder gelegentlich und 15,6% als wenig schadlich eingestuft werden, 14,1% als lokal schadlich, 7,3% als schadlich und 26,6% als sehr schadlich. Der Florenreichtum in den verschiedenen Okosystemen wurde analysiert und mit dem anderer Lander verglichen. Introduction A survey was made of the weed flora of an area of 13 200 km2 in the province of Co

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ern Spain. This area is in the central part of the Guadalquivir Basin and has a continental mediterranean climate, thermal in the Guadalquivir Valley and temperate sub-humid in the Sierra Morena. The monthly average temperature is 5-9°C in January and 27-8°C in July, with extremes of 48 C in summer and — 9 C in winter. The average annual rainfall varies between 410 mm and 990 mm, depending on the area, with a seasonal distribution characterized by a dry summer period of 2-4 months. The typical Mediterranean vegetation has been greatly affected by man; the original plant communities have been replaced by croplands, and only some relict Quercus rotundifolia forests and shrublands remain in the northern part of the province. Although studies of the weed floras of irrigated crops (Hernandez Bermejo et al., 1984), orchards and horticultural crops (Pujadas Salva & Hernandez Bermejo, 1986), cereals (Montegut, 1974), rape (Garcia Torres & Vazquez, 1979) and olive groves (Garcia Torres et al., 1983) have been carried out in the last few years in southern Spain, there are no complete regional catalogues of any part of the area. This encouraged us in 1981 to start cataloguing and analysing the weed flora in the province of Cordoba, considering its geographical distribution and the different ecosystems in which it is found. An initial outline was published in 1984 (Pujadas Salva & Hernandez Bermejo, 1984) and the survey is now finished. The present paper summarizes the main results.

Materials and methods The survey was conducted between 1981 and 1984, using a stratified sampling method. The area was divided into 100 squares of 15x9 km each, and routes planned to establish sampling localities as equidistantly as possible (about 10 km) with at least one sample from each square. The number of sampling localities in each square varied according to its agricultural interest, and to ensure that the most important ecosystems were represented there were sometimes several samples from a single locality. The total number of samples was 439, from 261 localities. The sample size was 40 x 40 m for crops, 50 x 2 m for roadsides, slopes and crop edges, and lOOx 1 m for ditches and irrigation canal edges. The frequency of occurrence of each species, and its potential influence on crops, was assessed as: rare

or casual, slightly harmful, locally harmful, harmful or very harmful. The 14 habitats recognized, six of them ruderal and eight agrestal, together with the numbers of samples were: ruderal—roadsides (22), slopes (26), ditches (142), irrigation canal edges (4), uncultivated lands and dumps (23) and crop edges (33); agrestal—horticultural crops (20), orchards (14), olive groves (94), vineyards (6), annual non-irrigated winter-spring cycle crops (29) (wheat, barley, oats, sugarbeet, rape and beans), annual irrigated winter-spring cycle crops (7) (wheat), annual non-irrigated spring-summer cycle crops (6) (safflower and chickpea), annual irrigated spring-summer cycle crops (13) (cotton, tobacco and corn). Nomenclature basically follows Tutin et al. (1964-1980), although certain changes according to Jalas & Suominen (1972-1983), Greuter, Burdet & Long (1984, 1986) and Valdes, Talavera & Fernandez-Galiano (1987) were adopted. Results and discussion Floristic composition A total of 941 taxa distributed in 81 families was recorded. Table 1 shows the 34 families for which the highest number of species were recorded, in comparison with the numbers for the Iberian Peninsula as a whole. Table 1 provides an indication of the phytogeographical and ecological origin of the weed flora. Thus, the numbers of weeds in Cistaceae, Caryophyllaceae and Scrophulariaceae reflect the influence of the autochthonous flora; they are well represented in the local weed flora but their percentages are notably lower than in the Iberian flora. Likewise, families such as Amaranthaceae, Solanaceae, Malvaceae and Polygonaceae, in which a high proportion of the species behave as weeds, may be identified. Other families like Rosaceae, Campanulaceae, Ranunculaceae and Cyperaceae were poorly represented in spite of their importance in the Iberian flora. Out of the 81 families recorded, Compositae, Leguminosae and Gramineae, with more than 100 species each, comprise 37% of the weed flora,

Weeds of southern Spain Table 1 Distribution of weed species within families compared with the total number of wild species in the Iberian Peninsula Area stiudied Iberian Peni

Family Compositae Leguminosae Gramineae Umbelliferae Labiatae Cruciferae Caryophyllaceae Scrophulariaceae Liliaceae Euphorbiaceae Boraginaceae Ranunculaceae Polygonaceae Papaveraceae Chenopodiaceae Rubiaceae Amaranthaceae Geraniaceae Malvaceae Rosaceae Cistaceae Solanaceae Valerianaceae Convolvulaceae Plantaginaceae Iridaceae Cyperaceae Crassulaccae Gentianaceae Campanulaceae

No. species recorded

% of total recorded

136 114 103 44 43 41 36 35 24 21 20 19 18 18 16 13 12 12 12 10 10 10 9 8 8 8 8 6 6 6

14-5 12-1 10 9 4-7 4-6 4-4 3-8 3-7 2-6 2-2 21 20 1-9 1-9 1-7 1-4 1-3 1-3 1-3 11 1-1 11 10 0-9 0-9 0-9 0-9 0-6 0-6 0-6

%of No. species total 121 7-6 7-8 3-5 41 4-7 4-5 4-3 2-3 11 1-4 2-2 0-7 0-8 0-9 1-4 0-2 0-9 0-5 2-5 1-2 0-3 0-5 0-4 0-5 0-6 2-5 0-8 0-6 1-2

750 468 4S4 214 257 292 281 265 142 69 89 139 46 52 55 S4 13 54 30 154 77 16 32 27 29 37 158 51 38 77

] 77

and together with Umbelliferae, Labiatae and Cruciferae account for more than 50%. Others like Amaranthaceae, Solanaceae, Cucurbitaceae and Lythraceae with a high proportion of weedy species are strongly represented in Cordoba; more than one-third of the total for the Iberian Peninsula are found here. Other families have very few weed species, yet these may be among the most common and aggressive weeds. Examples are Verbenaceae with three species (mainly Verbena officinalis), Orobanchaceae with four (mainly Orobanche crenata), Dipsacaceae with three (mainly Scabiosa simplex ssp. dentata and 5". atropurpurea), or those with only one weed species like Portulacaceae (Portulaca oleracea), Zygophyllaceae (Tribulus terrestris), Simaroubaceae (Ailanthus altissimd), Violaceae {Viola kitaibeliana) and Asclepiadaceae (Cynanchum acutum). Of the 433 genera recorded, the 42 with the highest numbers of species are shown in Table 2 in decreasing order. These 42 genera all have five or more species, making a total of 330 different taxa; in other words, approximately 10% of the genera account for 33% of the flora found in the area studied. Genera like Trifolium, Euphorbia, Vicia, Silene, Ononis, Rumex, Amaranthus, Medicago, Bromus, Centaurea and Allium have 10 or more species each.

Floristic diversity The richness of the flora was not homogeneous in the 14 habitats analysed but varied considerably. The following numbers of weeds were recorded.

Table 2 Numbers of weed species within genera Genus Trifolium Euphorbia Vicia Silene Ononis Rumex Amaranthus Medicago Bromus Cent a urea A ilium Veronica Chenopodium Ranunculus Fumaria Plantago Lathvrus Galium Papaver Astragalus Geranium

No. species

Genus

No. species

22 18 16 14 12 11 11 1 1 11 10 10 9 8 8 8 8 7 7 6 6 6

Erodium Cislus Daucus Centaurium Linaria Hordeum Polygonum A triplex Spergularia Oxalis Malva Ly thrum Convolvulus Teucrium Salvia Solatium Verhascum Sonchus Vulpia A vena Phalaris

6 6 6 6 6 6 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

Olive groves—536 species. This is to be expected since olive groves occupy 41 % of the arable land in the province. They are mainly located in hilly and non-irrigated areas, making eradication by herbicides difficult and rare. Moreover, ploughing around the tree trunks is very difficult so that many weeds are able to survive. Vineyards—119 species. Vineyards are found on the better soils and farmers make more extensive use of herbicides and ploughing. Winter-spring cycle crops—334 species in nonirrigated fields where the use of herbicides is rare, and 79 species in the irrigated ones which are on the better soils, ecologically more uniform, grouped along the Guadalquivir Basin. These

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carry intensively cultivated crops with a high economic value, and the use of herbicides is common. Irrigated spring-summer cycle crops—113 species. Once again the use of herbicides and ploughing is extensive. However, in contrast to the species in the irrigated winter-spring cycle crops, a significant number are not of Mediterranean origin but are allocthonous, cosmopolitan or subtropical; e.g. Amaranthus retroflexus, A. albus, Conyza bonariensis, Cuscuta campestris, Datura stramonium, Paspalum paspaloides and Xanthium spinosum. Horticultural crops and orchards—179 and 162 species, respectively. These are also irrigated crops where the use of herbicides and tillage techniques to eradicate weeds is important. Ditches—612 species. Ditches seem to be an important refuge for the autocthonous flora, as human intervention is minimal (cleaning and burning from time to time), and for allocthonous species because of the high humidity found in some of them. Crop edges and uncultivated lands and dumps— 346 and 321 species, respectively. Human intervention in these habitats is constant (burning and herbicides, and especially in dumps, the presence of chemical products and rubbish). Irrigation canal edges—57 species. Characterized by the presence of hydrophytes (7%) like Phragmites australis, Typha dominguensis and Cyperus longus. The number of weed species recorded in an area of only 13 200 km2 (941, or 599 if casual and rare are omitted) is high considering that the total number of weeds in the world is slightly over 8000 (Holm et al., 1977). The different definitions of 'weeds' given, differences in research methods and even in the extent to which the weed flora is known, make comparison very difficult. However, the number is clearly high compared with those for other countries, which vary from 120 species for Finland and less than 300 for Austria (Holzner & Immonen, 1982) to 884 for South Africa (Wells & Stirton, 1982) and 941 for Canada (Alex, 1982). One reason for this is the richness of the wild flora in the south of Spain, with more than 1750 taxa in Cordoba province alone. As already noted, some of the ecosystems

examined, like olive groves and ditches, serve as refuges for representatives of this flora. The other crops grown in the region provide a range of habitats varying in temperature, rainfall, sun exposure, soil, slope and degree of disturbance, which ensures floristic diversity. Agricultural importance On the basis of frequency of occurrence (number of times recorded from different localities) and their potential influence on crop production, the species could be grouped as follows: Rare or casual. These were recorded in only one or two localities and make up 36-3% of the total number of species found. Examples are Vicia monantha, Digitalis thapsi and Valerianella pumila. These do not present any problem to the farmer. Slightly harmful. Species such as Parietaria judaica, Chenopodium ambrosioides and Glinus lotoides recorded in more than two localities and making up 15-6% of the total found. These occur mainly in ruderal habitats and rarely invade crops; they are easy to eradicate and so their agricultural significance is minimal. Locally harmful. This category comprises species found in less than seven localities but which at a local level or in particular crops can have serious effects. They account for 14T% of the total and examples are Fallopia convolvulus in horticultural crops, A triplex chenopodioides and Silene stricta in some sunflower crops, Euphorbia nutans in cotton crops, and Bromus scoparius in olive groves. Harmful. These are frequent species, found in more than seven localities, which usually occur in crops although they are not so abundant and persistent as the very harmful species. They represent only 7-3% of the total number. Some of the most important are Polycarpon tetraphyllum, Erodium botrys, Galium parisiense, Anthemis cotula and Aegilops neglecta. Very harmful. These are the species of most frequent occurrence, which are often abundant, and which are the most difficult to eradicate in crop lands. They represent 26-6% of the total. The 25 most common and aggressive weeds are

Table 3 Relative importance of the most harmful weeds

Horticultural crops Convolvulus arvensis Calendula arvensis Raphanus raphanistrum Diplotaxis virgata Sonchus oleraceus Fumaria officinalis Papaver rhoeas Lamium amplexicaule Anagallis arvensis Erodium malacoides Bromus madritensis Me die ago nigra Fumaria parviflora Eehium plantagineum Hordeum leporinum Hirschfeldia incana Eryngium campestre Fedia eornucopiae Andryala integrifolia Cynodon dactylon Sanguisorba minor ssp. magnolii Senecio vulgaris Crepis vesicaria ssp. haenseleri Rumex bucephalophorus Euphorbia helioscopia

4* 2 1 2 3 2 2 2 1 2

Orchards 5 3 2 2 5 2 1 2 2

2 2

2

2

Olive groves 2 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

Annual Annu irriga non-irrigated winter-spring winter-s cycle c cycle crops Vineyards 5 2 1 3 1 1 2 1 2 1 2 2 1 2 1 2 1 1 3 3 1 1 1 2 1

4 2 3 1 1 3 2 1 2 1 2 2 1 3 2 2 2 1 3 1 2 2 2 2 1

3 5 5 5 2 4 2 4 3 2 3 2 5 2 1 5 3 2 1 1 2 1 3 1 3

* Values denote % occurrence in samples from each habitat: 0-20% (1), 20-40% (2), 40-60% (3), 60-8

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shown in Table 3 and their relative importance (%) is indicated for the eight agrestal habitats. Thus the most common weed, Convolvulus arvensis, is very abundant in orchards, vineyards and annual non-irrigated spring-summer cycle crops. Most of the species in this table have a winterspring phenology, except for Cynodon dactylon, which mainly appears in the spring-summer crops. In short, nearly half (48%) of the weed species found are to some extent harmful to agriculture and the families represented to the greatest extent are Compositae (46 species), Leguminosae (31), Gramineae (28) and Cruciferae (20).

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