CTE Soil Biogeochemistry 2014



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Climate change is increasing the intensity of severe tropical storms and cyclones (also referred to as hurricanes or typhoons), with major implications for tropical Forest structure and function. These changes in disturbance regime are likely to play an important role in regulating ecosystem carbon (C) and nutrient dynamics in tropical and subtropical forests. Canopy opening and debris deposition resulting from severe storms have complex and interacting effects on ecosystem biogeochemistry. Disentangling these complex effects will be critical to better understand the long-term implications of climate change on ecosystem C and nutrient dynamics. In this study, we used a well-replicated, long-term (10 years) canopy and debris manipulation experiment in a wet tropical forest to determine the separate and combined effects of canopy opening and debris deposition on soil C and nutrients throughout the soil profile (1 m). Debris deposition alone resulted in higher soil C and N concentrations, both at the surface (0–10 cm) and at depth (50–80 cm). Concentrations of NaOHorganic P also increased significantly in the debris deposition only treatment (20–90 cm depth), as did NaOH-total P (20–50 cm depth). Canopy opening, both with and without debris deposition, significantly increased NaOH-inorganic P concentrations from 70 to 90 cm depth. Soil iron concentrations were a strong predictor of both C and P patterns throughout the soil profile. Our results demonstrate that both surface- and subsoils have the potential to significantly increase C and nutrient storage a decade after the sudden deposition of disturbance-related organic debris. Our results also show that these effects may be partially offset by rapid decomposition and decreases in litterfall associated with canopy opening. The significant effects of debris deposition on soil C and nutrient concentrations at depth (>50 cm), suggest that deep soils are more dynamic than previously believed, and can serve as sinks of C and nutrients derived from disturbance-induced pulses of organic matter inputs.

Date Range: 
2014-09-01 00:00:00 to 2014-11-30 00:00:00

Publication Date: 

2018-04-05 00:00:00


We measured soil pH in a 1:1 soil to water slurry, as well as gravimetric soil moisture by oven-drying subsamples at 105°C to a constant weight. Total soil C and N content were measured on a CE Instruments NC 2100 Elemental Analyzer (Rodano, Milano, Italy) on soils that were air-dried and ground. To measure labile (i.e., soluble phosphate) and recalcitrant (i.e., bound to Fe or Al) P pools, we used a modified Hedley fractionation with NaHCO3 and NaOH extractions respectively (Tiessen & Moir, 1993). Briefly, we sequentially extracted approximately 1.5 g fresh soil with 0.5 M NaHCO3 and 0.1 M NaOH. Both extracts were analyzed colorimetrically for inorganic P and total P after digestion with acid ammonium persulfate, while organic P was calculated as the difference between total and inorganic P (Murphy & Riley, 1962). We measured Fe species as these have been shown to be an important predictor of both C (Hall & Silver, 2015) and P (Chacon, Silver, Dubinsky, & Cusack, 2006) cycling in this ecosystem. Concentrations of reduced and oxidized iron (Fe(II) + Fe(III)) were measured with a 0.5 M HCl extraction and analyzed colorimetrically. Soils were extracted with 0.2 M sodium citrate/0.05 M sodium ascorbate solution and analyzed on an inductively coupled plasma atomic emission spectrometer (Perkin-Elmer, USA) for poorly crystalline Fe. We were only able to analyze two treatments for citrate ascorbate-extractable Fe due to limited resources, and thus chose the controls and the opening+debris treatments as being most representative of a natural event.



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