Individual plant and population biomass of dominant shrubs in Patagonian grazed fields.

OÑATIBIA, G.; AGUIAR, M.R.; CIPRIOTTI, P.A.; TROIANO, F.

ECOLOGÍA AUSTRAL

ASOCIACIÓN ARGENTINA DE ECOLOGÍA

Lugar: Buenos Aires; Año: 2010 vol. 20 p. 269 - 279

0327-5477

Estimating aboveground biomass of vegetation is essential for population, community and ecosystem studies. In systems dominated or co-dominated by woody species, biomass estimation is difficult, and rapid and non-destructive methods are needed. In this study, wedescribe biomass distribution in different components (i.e., wood, leaves) and how this changeswith shrub size for the three dominant species of shrubs in the Occidental District of the Patagoniansteppe. We also describe the population size structure of the three species in grazed fields andestimate their contribution to total abundance and biomass through a non-destructive method.We developed allometric equations to estimate aboveground biomass components of individualshrubs from structural descriptors (i.e., diameter and height of the crown), sampling individualplants of different sizes. The variable that best predicted biomass of the three species was the sumof the height and the average diameter of the crown (calculated with the largest diameter and itsperpendicular). Allometric models for each species explained more than 83% of the variabilityof individual aboveground biomass. At the individual level, species had different proportions ofwood, leaves and specific wood weight. Increasing shrub size was accompanied by changes in theproportion of leaves to wood, and in some cases, the percentage of dead crown. At the populationlevel, the three species differed in size distribution in moderately grazed fields. Development ofallometric models from a population perspective is important to study demographic processesthat drive community and ecosystem responses to environmental and land-use changes.