Soil respiration across a disturbance gradient in sclerophyllous ecosystems in Central Chile

Published in Ciencia e Investigación Agraria, v. 41(1):89-106
Authors

Bown, H.E., Fuentes, J.P., Pérez-Quezada, J.F. and Franck, N.
Publication year 2014
DOI http://dx.doi.org/10.4067/S0718-16202014000100009
Affiliations
  • Facultad de Ciencias Forestales y Conservación de la Naturaleza, Universidad de Chile. Casilla 9206, Santiago, Chile.
  • Facultad de Ciencias Agronómicas, Universidad de Chile. Casilla 1004, Santiago, Chile.
  • Centro de Estudios de Zonas Áridas, Universidad de Chile. Casilla 129, Coquimbo, Chile.

 
IAI Program

CRN3
IAI Project CRN3005
Keywords
Acacia caven savanna
disturbance gradient
sclerophyllous forest
soil respiration
thorn scrub

Abstract

Sclerophyllous shrubs and forests are predominant in semiarid Central Chile and have a long history of degradation by fire, cultivation, firewood extraction and grazing. The aim of this study was to compare the amount and environmental drivers of soil respiration across a disturbance gradient in sclerophyllous ecosystems in the National Reserve Roblería del Cobre de Loncha in Central Chile. In a north-facing toe slope, four disturbance conditions were identified: slightly (D1) and moderately disturbed (D2)
sclerophyllous forest, (D3) strongly disturbed thorn scrub and (D4) most disturbed A. caven savanna. Twelve 25×25-m plots (625 m2) were distributed equally across D1, D2, D3 and D4. Soil respiration (Rs), soil temperature (Ts), volumetric water content (&thetav) and exchangeable nitrogen (Ns) were measured at six dates in each plot between August 2009 and May 2010. Additionally, Ts and &thetav were continuously recorded from July 2010 to August 2012 (30-minute intervals) in one plot per disturbance condition
(i.e., 4 out of 12 plots). The values of Rs increased linearly with &thetav with similar slopes but different intercepts, which increased as the disturbance receded. Once soil water content was taken into account, Rs increased with Ts with the same slope but with a disturbance-dependent intercept. Additionally, the response of Rs to Ts was more pronounced as &thetav increased. The values of Ns were uncorrelated with Rs.
The annual values of Rs were 4.4-fold greater in D1 (1,735 g C m-2 yr-1) compared with D4 (392 g C m-2 yr-1). Disturbance presumably decreased Rs by reducing the litter layer, soil organic matter, root biomass and soil water content, particularly in the hot-dry season. Under a predicted climate change scenario of a 40% decrease in rainfall and 4°C increase in air temperature by the year 2100, we found that annual Rs would be reduced on average by 28% compared with the current climate, with that reduction being more pronounced under more disturbed conditions, suggesting that less disturbed conditions would be more resistant to climate change, thus further justifying the restoration of these damaged ecosystems.