Latitudinal characteristics of below- and above-ground biomass of Typha: a modelling approach.
OBJECTIVE
The latitudinal differences in the growth characteristics of Typha are largely unknown, although a number of studies have pointed out the effects of climate on the growth and productivity of Typha. Therefore, a dynamic growth model was developed for Typha to examine the effects of latitudinal changes in temperature and radiation on partitioning of the total biomass during the growing season into rhizomes, roots, flowering and vegetative shoots, and inflorescences.


METHODS
After validating the model with data from growth studies of Typha found in past literature, it was used to investigate the dynamics of above- and below-ground biomasses at three latitudes: 30 degrees, 40 degrees and 50 degrees.


RESULTS
Regardless of the initial rhizome biomass, both above- and below-ground biomass values converged to a latitude-specific equilibrium produced by the balance between the total production and respiration and mortality losses. Above-ground biomass was high from 10 degrees to 35 degrees latitude with sufficient radiation, despite high metabolic losses; however, it decreased markedly at higher latitudes due to a low photosynthetic rate. Below-ground biomass, on the other hand, increased with latitude up to 40 degrees due to decreasing metabolic losses, and then markedly decreased at higher latitudes. Above-ground biomass was enhanced with an increasing number of cohorts regardless of latitude. However, although more cohorts resulted in a larger below-ground biomass at low latitudes, the largest below-ground biomass was provided by a smaller number of cohorts at high latitudes. This difference is due to low production rates of late-season cohorts in high latitudes, compared with consumption for shooting and establishing foliage.


CONCLUSIONS
The model could be used to predict the potential growth of Typha in given conditions over a wide range of latitudes and is useful for practical applications such as wetland management or wastewater treatment systems using Typha.
Asaeda
Takashi
T
Department of Environmental Science and Human Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338, Japan. asaeda@post.saitama-u.ac.jp
Hai
Dinh Ngoc
DN
Manatunge
Jagath
J
Williams
David
D
Roberts
Jane
J
D018533:Biomass; D003198:Computer Simulation; D008954:Models, Biological; D010788:Photosynthesis; D018520:Plant Shoots / Q000254:growth & development / Q000502:physiology; D027343:Rhizome / Q000254:growth & development / Q000502:physiology; D012621:Seasons; D013696:Temperature; D032401:Typhaceae / Q000254:growth & development* / Q000502:physiology