Dynamics of above- and below-ground biomass and nutrient accumulation in an age sequence of Nothofagus antarctica forest of southern Patagonia

PERI, PABLO LUIS; GARGAGLIONE, V.; MARTÍNEZ PASTUR, G.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2006 p. 85 - 99

0378-1127

AbstractNothofagus antarctica (Forster f.) Oersted is a deciduous tree species, which naturally grows on poorly drained or drier eastern sites in theAndes Mountain near Patagonian steppe. Above- and below-ground biomass and nutrients pools were measured in pure even-aged stands atdifferent ages (5?220 years) and crown classes. Functions were fitted for total biomass and nutrients accumulation, and root/shoot ratio ofindividual trees against age. Total biomass accumulated for mature dominant trees was eight times greater than mature suppressed trees. Biomassroot/shoot ratio decreased with age from 1.8 to a steady-state of 0.5. All nutrients concentration (except Ca) decreased with age and variedaccording to the degree of crown suppression classes. Nutrient concentrations varied between biomass pool components following the orderleaves > bark > small branches > fine roots > medium roots > rooten wood > coarse roots > sapwood > heartwood. Total nutrient accumulationfollowed the order dominant > codominant > intermediate > suppressed trees and its accumulation rate varied over time, e.g. P accumulationrate of dominant trees increased from 0.17 g tree1 year1 during regeneration to 1.39 g tree1 year1 in mature trees. Nutrients uptake reached apeak during the period of maximum biomass production, and root/shoot ratio of nutrients decreased from its maximum value at 5 years of age (0.6,4.0, 0.9, 1.5, 1.0 and 2.6 for N, P, K, Ca, S and Mg, respectively) to a steady-state asymptote beyond 50 years of age. Thus, accumulation of nutrientsin roots was greater during the regeneration phase of stand development, and nutrient accumulation increased in above-ground over time. Also,nutrient use efficiency increased in mature trees (111?220 years) and decreased in suppressed crown classes. The equations developed forindividual trees have been used to estimate stand biomass and nutrient accumulation from forest inventories data. Total stand biomass varied from62.5 to 133.4 t ha1 and total nutrients accumulation ranged from 3 kg Mg ha1 to 1235 kg Ca ha1. Proposed equations can be used for practicalpurposes such as to estimate pasture nutrients requirement in a silvopastoral system based on nutrients supply from leaf litter returns, or todetermine amelioration practices like debarking stems before harvesting.# 2006 Elsevier B.V. All rights reserved.