Pr�diction de la biomasse a�rienne d'Acacia cyanophylla Lindl. (Syn. A. saligna (Labill.) H. Wendl) � partir de mensurations dimensionnelles

Abstract

Acacia cyanophylla Lindl. / modèles de régression / prédiction de biomasseAbstract -Above ground biomass prediction of Acacia cyanophylla Lindl. (Syn. A. saligna (Labill.) H. Wendl). Dimensional measurements were made on 45 four-year-old Acacia cyanophylla Lindl. shrubs which were cut at 20 cm above ground to predict biomass production. These shrubs planted at a density of 1100 plants/ha were located at the following sites: El Krib (high semi-arid), El Hojjaj (high semi-arid) and El Araïbia (humid) in the North West of Tunisia. In order to validate the regression models obtained, a subsample of 5 shrubs (not included in the total sample), representing 11% of the total sample was chosen at random. Linear regressions (simple and multiple) allowed to satisfactorly estimate the above ground biomass production of Acacia cyanophylla Lindl. using its volume or its basal diameter (R 2 = 0.76 to 0.96). However, the multiple regression involving simultaneously the volume and the basal diameter led to a better precision of the model (R 2 = 0.90 to 0.98).Acacia cyanophylla Lindl / regression models / biomass prediction Ann. For. Sci. 59 (2002) 335-340 335

Productivité en biomasse du chêne liège dans une séquence de dégradation de la suberaie à Cytise de Kroumirie (Tunisie)

“…L'analyse des résidus d'ajustement et le test de signification des coefficients de régression ont été effectués à l'aide du logiciel « SPSS 10,0 for Windows ». Le choix du modèle d'ajustement le mieux adapté aux données a été basé sur plusieurs critères : un meilleur coefficient de détermination (R 2 ), des coefficients de régression significatifs au seuil de 95 %, une signification biologique du résultat, un écart type résiduel (s) minimal et un meilleur coefficient de corrélation (r') entre la valeur mesurée et la valeur prédite [33,49]. Les données dendrométriques des 12 arbres échantillons et les biomasses des différents compartiments du tronc sont pré-sentées au tableau I.…”

Acacia salignaPlantation Impact on Soil Surface Properties and Vascular Plant Species Composition in Central Tunisia

“…Then we surveyed A. saligna recruitment by counting all spontaneously established individuals within each plot. Above-ground biomass of planted A. saligna trees was estimated using the data provided by Laamouri, Chtourou, and Ben Salem (2002). In this study A. saligna individuals were smaller than those measured in our study site.…”

“…Thus, we reanalyzed the data in Laamouri et al study to obtain an allometric relationship and thus reduce the error resulting from extrapolating the linear relationship found by these authors. We estimated the values in Figure 1a in Laamouri et al (2002) study by using image analyzer software (GIMP 2.2.3; Kimball and Mattis, 1997), and adjusted them to an allometric relationship above-ground biomass (kg) ¼ 0.298 basal diameter (cm) (1.9219) , N ¼ 29, R 2 ¼ 0.9561).…”

Reproductive and productivity traits of goats grazing Acacia cyanophylla Lindl. with and without daily PEG supplementation

“…The volume (V) of each plant assumed as parallelepiped was calculated as: V (m 3 ) = H  Dv  Dh. Foliage biomass (Fb) was estimated using the equation developed for A. cyanophylla by Laamouri et al (2002): Fb (kg) = 0.17 V + 1.23. Barley hay and concentrate (mixture of processed barley grain, soybean meal and a commercial mineral and vitamins supplement, 80 : 17.5 : 2.5) were also used in this experiment.…”