Exploring the role of nutrient in determining the water relations and carbon allocation of woody plants in Neotropical savannas and semi-deciduous Atlantic forests

BUCCI, SANDRA JANET; VILLAGRA, MARIANA; SCHOLZ, FABIAN; GOLDSTEIN, GUILLERMO

Bonito

Congreso; 49th Annual Meeting of the Association of Tropical Biology and Conservation; 2012

ATBC

The original areas of tropical savannas and Atlantic forests cover about of 4 million of square kilometers in South America. These ecosystems are controlled by the interactions among water and nutrient availability and frequency and type of disturbances. Although the role of water availability as a limiting factor, in particular of savanna dynamics, has been relatively well documented, the role of soil nutrients is much less understood. Here we will discuss the effects of long-term fertilizations on water relations, water consumption and growth in woody plants of Cerrado savannas in Central Brazil and in the Atlantic forest of North-Eastern Argentine. Typical isohydric behavior and similar rates of water consumption with respect to marked seasonal changes in precipitation in savannas are not maintained when Nitrogen availability is increased by fertilization. Apparently, alleviation of nutrient limitations affects physiological processes and patterns of carbon allocation in woody species in a manner that prevents homeostasis in plant water relations. Removal of nutrient limitations by fertilization modifies the pattern of resource allocation which maximizes carbon gain and enhances growth both in savannas and forest trees. In addition, it reduces the vulnerability to water stress induced embolisms, contrary to the general assumption that resistance to cavitation is not a plastic trait and that is mainly achieved at the expense of low growth rate. The result of our studies indicate that despite being adapted to chronic nutrient limitation (N and P), savanna and Atlantic forest trees apparently have the capacity to exploit increases in nutrient availability through architectural as well as physiological changes that allow to maximize the growth but at the same time minimize the risk of hydraulic failure.