Architecture of Ulex europaeus: Changes in the vertical distribution of organs in relation to plant height and season

摘要

This paper is concerned with the vertical distribution of photosynthetic, woody, reproductive and dead organs of Ulex europaeus, the dominant pyrophytic species in most of the shrublands of Galicia (NW Spain). Frequency and weight data for the above-mentioned organs were collected each season for individual plants up to 150 cm tall, in order to quantitatively characterize the vertical organ distribution in this species. The study also deals with regression equations that would allow the prediction of phytomass from easier measurements. Frequency values were recorded using a grid of quadrats situated on the plant's vertical axis, and clipping each individual into vertical layers of 6 cm to obtain phytomass values. The abundance and location of photosynthetic, woody and dead organs varies in the three height classes studied, both regarding frequency and phytomass. A marked decrease in the ratio between photosynthetic and total phytomass is also observed as plant height increases. Significant seasonal differences were recorded only for reproductive organs. A good fit was obtained for several regression equations; total phytomass can be predicted from the largest diameter of the shrub, or organ phytomass from total weight.