ORIGINAL ARTICLE Species – area relationships and minimum area in citrus grove weed communities A. CRISTAUDO 1 , A. RESTUCCIA 2 , A. ONOFRI 3 , V. LO GIUDICE 4 , & F. GRESTA 5 1 Department of Biological, Geological and Environmental Sciences, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; 2 Department of Agricultural and Food Science (DISPA), University of Catania, Via Valdisavoia 5, 95123 Catania, Italy; 3 Department of Agricultural and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, 06121 Perugia, Italy; 4 Research Center for Citriculture and Mediterranean Crops, C.so Savoia 190, 95024 Acireale (CT), Italy and 5 Department of Food and Environmental Biotechnologies, Mediterranean University of Reggio Calabria, Feo di Vito, 89060 Reggio Calabria, Italy Abstract Field surveys were carried out in the Catania plain (eastern Sicily, Italy) on winter – spring weed communities in citrus groves, an economical and traditional crop of the Mediterranean area. The aim of this study was to define species – area relationships and to derive information on the minimum sampling area in citrus groves, taking into consideration the ecological, botanical and agronomical implications. Weed flora was composed of 63 taxa belonging to 25 botanical families (42% of taxa included in the families Poaceae, Asteraceae and Brassicaceae). The dominance of therophytes and species with a wide distribution was related to the high degree of artificiality induced by human pressure. The species richness per survey was rather low, ranging from 8 to 22 species, in a surface area of 256 m 2 . Species–area analyses showed that the minimum sampling area that fully expressed the specific characteristics of plant communities in these citrus groves ranged from 33 to 56 m 2 . As a result, this methodology can be an appropriate decision support system for sustainable weed management strategies, with a more rational use of herbicides. Keywords: Citrus grove, minimum area, nested-plot design, species – area relationships, weed community Introduction One of the key aspects of vegetation analysis is the representativeness of the survey; indeed, the size of the survey area in which the sampling is carried out should never be lower than the minimum area, in order to avoid spurious results due to the loss in floristic cortege data (Feoli et al. 2011; Pott 2011). This assumes much more importance in weed science, wherein the adoption of appropriate weed management strategies and the evaluation of their environmental impact should always be based on representative weed surveys. The concept of “minimum area” of the plant community has been studied by vegetation scien- tists since the late 1920s (Braun-Blanquet 1928, 1932; Pavillard 1935) and began to arouse the interest of researchers some years later. Braun- Blanquet (1928) defined the “minimum area” as the surface where the species–area curve becomes approximately horizontal. Later, the same author (1932) stated that “a community of plants requires for its normal development a minimal area and, also upon this area, a minimal number of plant species”. Subsequently, Pignatti (1959) stated that a minimum area is “the area within which an association can develop most completely”. Even more recently, Mu ¨ eller-Dombois and Ellenberg (1974) suggested that the minimum area is the smallest area in which the species composition of a plant community is adequately represented. There- fore, the minimum area represents an important structural value of the plant association, and also has a practical value to detect the significant minimal area for obtaining sufficiently indicative data of plant communities. q 2013 Societa ` Botanica Italiana Correspondence: A. Cristaudo, Department of Biological, Geological and Environmental Sciences, University of Catania, Via Valdisavoia 5, 95123 Catania, Italy. Tel: þ 39 95234353. Fax: þ 39 95234320. Email: acristau@unict.it Plant Biosystems, 2015 Vol. 149, No. 2, 337–345, http://dx.doi.org/10.1080/11263504.2013.825344 Downloaded by [University of Catania], [Antonia Cristaudo] at 03:29 06 March 2015