Spatiotemporal variability of soil respiration in a seasonal tropical forest

Abstract

We monitored soil CO 2 effluxes for over 3 years in a seasonally wet tropical forest in Central Panama using automated and manual measurements from 2013 to 2016. The measurements displayed a high degree of spatial and temporal variability. Temporal variability could be largely explained by surface soil water dynamics over a broad range of temporal scales. Soil moisture was responsible for seasonal cycles, diurnal cycles, intraseasonal variability such as rain‐induced pulses following dry spells, as well as suppression during near saturated conditions, and ultimately, interannual variability. Spatial variability, which remains largely unexplained, revealed an emergent role of forest structure in conjunction with physical drivers such as soil temperature and topography. Mean annual soil CO 2 effluxes (±SE) amounted to 1,613 (±59) gC m−2 year−1 with an increasing trend in phase with an El Niño/Southern Oscillation (ENSO) cycle which culminated with the strong 2015–2016 event. We attribute this trend to a relatively mild wet season during which soil saturated conditions were less persistent.

Significant Diel Variation of Soil Respiration Suggests Aboveground and Belowground Controls in a Tropical Moist Forest in Puerto Rico

“…For example, tropical moist forests, such as our site, might exhibit more frequent wetting and drying cycles as opposed to more seasonal tropical forests with marked dry seasons that result in prolonged periods of unfavorable conditions for biological activity in the soil. However, Rubio and Detto (2017) reported diel patterns were most evident during the dry season at their seasonal tropical wet forest suggesting the processes responsible for the diel variability remain active during dry periods. In addition, although small in magnitude, their observed diel patterns were apparently driven by fluctuations in soil moisture rather than temperature (Rubio & Detto, 2017).…”

“…In addition, although small in magnitude, their observed diel patterns were apparently driven by fluctuations in soil moisture rather than temperature (Rubio & Detto, 2017). Other studies have found relationships with soil temperature similar to ours (Meir et al, 1996; Raich, 2017; Zanchi et al, 2014), although hysteresis was also evident suggesting other potential controls in addition to temperature on diel variation of soil respiration (Raich, 2017; Rubio & Detto, 2017; Vargas & Allen, 2008a; Zanchi et al, 2014).…”

“…Our high frequency measurements using automated chambers revealed significant diel variation of soil respiration in this tropical moist forest throughout a 3-year period. Results from prior studies investigating soil respiration on this time scale in other tropical forests have been mixed, with some studies reporting significant diel variation of soil respiration Medina, 1969;Medina et al, 1980;Meir et al, 1996;Raich, 2017 ;Rubio & Detto, 2017 ;Vargas & Allen, 2008a ;Zanchi et al, 2014), and others reporting relatively consistent soil respiration values throughout the day (Davidson et al, 2000;Doughty & Goulden, 2008;Giardina & Ryan, 2002;Goulden et al, 2004;Litton et al, 2011;Salimon et al, 2004;Schwendenmann et al, 2003;Trumbore et al, 1995;Wood et al, 2013). The lack of significant variation of soil respiration at diel time scales in tropical forests could be a consequence of insufficient sampling frequency-a common limitation of soil respiration studies conducted in the tropics.…”

Medición continúa de flujo de CO2 en suelo en una parcela de bosque tropical en Isla Barro Colorado, Canal de Panamá.

“…El clima de la isla es típico de un bosque tropical de tierras bajas, la temperatura promedio es de 27°C, la temporada lluviosa se extiende de mayo a diciembre y durante la temporada seca de mediados de diciembre a abril, los vientos alisios prevén tormentas convectivas de esta manera dictando los ritmos estacionales. La precipitación media anual es de 2642 (± 566) mm [27,31].…”

“…Las cámaras se instalan sobre estos collares que tienen un diámetro exterior de 20 cm y están ubicados en los vértices de un cuadrado de 20 × 20 m centrados radial a una torre microclimática, donde hay disponibilidad de red eléctrica; las mediciones de flujo de CO 2 se toman cada segundo durante 2 minutos después de que la cámara cierra. Se realiza una prepurga de 30 segundos y postpurga de 45 segundos para asegurar que el sistema se limpie entre cada medición [25,31].…”