Decay rate and substrate quality of fine roots and foliage of two tropical tree species in the Luquillo Experimental Forest, Puerto Rico

Abstract

Decomposition rates, initial chemical composition, and the relationship between initial chemistry and mass loss of fine roots and foliage were determined for two woody tropical species, Prestoea montana and Dacryodes excelsa, over a gradient of sites in two watersheds in the Luquillo Experimental Forest, Puerto Rico. At all locations, fine roots decayed significantly more slowly than foliage during the initial 6 months.Substrate quality of the initial tissue showed marked differences between roots and foliage when using cell wall chemistry, secondary chemistry and total elemental analysis as indices. Quantity of acid detergent fiber (ADF) (non-digestible cell wall fiber) and lignin content were higher for roots than leaves: D. excelsa roots had 55.3% ADF and 28.7% lignin while leaves had 36.2% ADF and 11.8% lignin; P. montana roots had 68.0% ADF and 26.8% lignin while leaves had 48.5% ADF and 16.1% lignin. Aluminum concentrations were higher in fine roots (843 mg kg -x in D. excelsa, 1500 mg kg -x in P. montana) than leaves (244mg kg -x in D. excelsa, 422mgkg -1 in P. montana), while calcium concentrations were higher in foliage (5.5 mg g-1 in D. excelsa, 7.8 mg g-X in P. montana) than roots (3.4mgg -1 in D. excelsa, 3.1 mgg -x in P. montana). Nitrogen did not show any trend with tissue or species type. A linear model between mass remaining after 6 months and initial tissue chemistry could be developed only for calcium (r 2= 0.64).

Decomposition dynamic of fine roots in a mixed forest of Cunninghamia lanceolata and Tsoongiodendron odorum in mid-subtropics

“…The values of annual decay constant (k, year-based) for the fine roots of the Chinese fir and the Tsoong's tree (Tab. I) fall in the range of the values reported for the forests of the world (0.03-1.74) [2,8,11,15,23,26,29], and were comparable with the values for the subtropical forest ecosystems (0.6-1.74) [2,8,15].…”

“…Compared with other studies, there only occurred for N in the fine roots of Chinese fir an initial microbiological immobilization with a low magnitude and a short duration, and release of P began from the outset for both species without a period of net immobilization (Fig. 3), indicating that the N and P availability for microorganisms in the site were relatively high [2,5,8]. Of the initial amount of P in fine roots of Tsoong's tree, 30.9-41.5% was lost from decomposing root litter during the first 60 days compared with a weight loss of 22.9-30.2% (Figs.…”

The Biogeochemistry of Carbon at Hubbard Brook

“…The extent to which fine roots are protected biochemically from consumption by soil fauna remains unclear because the causes of root mortality are poorly understood (Eissenstat and Yanai 1997). Applying fungicide and insecticide to soils significantly reduced the mortality of fine roots of Prunus persica (Wells et al 2002) which suggests that soil invertebrates may consume significant amounts of fine-root C. Although it seems likely that fine-root chemistry would influence the rate of decomposition of dead roots (Bloomfield et al 1993), the lack of reliable measurements of in situ fine root decay rates has precluded the empirical demonstration of such relationships.…”

Fine litter input to terrestrial humus forms in Colombian Amazonia

“…This suggests that the much higher necromass of the ectorganic horizons in plot 4 compared to that in plot 3 (Table 1) is possibly not related to lower decomposition rates of above-ground fine litter, but to the larger input of dead fine roots. Corrections for nutrient residence times in all ectorganic horizons, based on nutrient input by dead fine roots were not attempted, because too little information is available on nutrient concentrations in fine roots, in comparison to those in fine litter (Bloomfield et al 1993). The mobility sequence and relative turnover rates in the plots 1 and 2, where effects of fine root input are small, stem with results obtained by Burghouts (1993) in a rain forest of Borneo.…”