Mass, nutrient pool, and mineralization of litter and fine roots in a tropical mountain cloud forest

We used fine root and litter mass from a tropical mountain cloud forest to assess their relative contribution to nutrient content and to examine mineralization processes during a laboratory incubation experiment. Our results showed that average fine root mass density ranged from 2.86 kg m(-3) to 11.59 kg m(-3), while litter mass density ranged from 72.5 kg m(-3) to 177.3 kg m(-3). Onaverage, fine root mass density represented 4.7% of the mass density of the O horizon. Fine root mass density followed an exponentially declining trend with soil depth. On average, 83% of fine root mass density within the soil profile was concentrated in the O horizon. Mean element pools in litter decreased from 44.08 mg cm(-3) to 0.49 mu g cm(-3) in the following sequence: C > N > Fe > S > Ca > P > K > Mg > Na > Mn > Zn > Cu. For fine roots, a different mean element pool sequence (C > N > Ca > K > Fe > S > Mg > Na > P > Mn > Zn > Cu) in decreasing abundance (from 2.88 mg cm(-3) to 0.13 mu g cm(-3)) was observed with respect to litter. Regarding C, litter mineralized faster than fine roots, with a mean k value of 0.25 d(-1) for litter and 0.13 d(-1) for fine roots. Principal component analysis (PCA) combined with stepwise regression analysis revealed that the main mass density predictors were N, S, Zn, and Mn for litter (p < 0.0001, R-2 = 0.92), and S and C/N ratio for fine roots (p < 0.0001, R-2= 0.82). These results demonstrate the potential of chemical composition to influence the mineralization of fine root and litter mass and therefore the nutrient availability and C sequestration. (C) 2016 Elsevier B.V. All rights reserved.