Abstract
Allometric equations were developed to estimate aboveground dry phytomass (AGDP) in some coastal herbaceous halophytic species of Karachi viz. Atriplex griffithii Moq. Cressa cretica L., Phragmites karka (Retz.) Trin ex Steud., Limonium stocksii (Boiss.) O. Ktze, and Urochondra setulosa (Trin.) C.E. Hubb. Best fit least square regression models were developed using height and crown diameter to estimate AGDP of individual plants. In case of P. karka, culm height, culm basal diameter or culm volume were employed to estimate phytomass of an individual culm. The crown diameter was generally better predictor of phytomass than height. The inclusion of parameter of height as an independent variable along with crown diameter could not improve the estimation of phytomass significantly except in case of P. karka where substantial improvement in estimation of culm mass was recorded (24.3%) when height was included along with culm diameter in a natural log-log model of multiple correlation and regression. Quadratic (curvilinear) relationships between phytomass and crown diameter were significant in all plants. The quadratic equations were more or less as equally statistically efficient as multiple regression models in estimating phytomass in Atriplex, Cressa and Limonium. Culm phytomass in Phragmites and AGDP in Urochondra setulosa were, however, better estimated by multiple regression models with natural log-log transformed variables.
