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Scientia Silvae Sinicae ›› 2019, Vol. 55 ›› Issue (4): 1-12.doi: 10.11707/j.1001-7488.20190401

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Characterization of Soil Respiration after Conversion from Natural Forest to Plantations in Central-Subtropical Area

Liu Bao1, Wang Minhuang2, Yu Zaipeng2, Lin Sizu1, Lin Kaimin1   

  1. 1. College of Forestry, Fujian Agriculture and Forestry University Fuzhou 350002;
    2. College of Geographical Science, Fujian Normal University Fuzhou 350007
  • Received:2018-03-09 Revised:2019-01-23 Online:2019-04-25 Published:2019-04-30

Abstract: [Objective]The aim of this study was to explore the changes in soil carbon (C) fluxes after conversion from evergreen broad-leaved forest (natural forest) to plantations for 35 and 38 years in central-subtropical areas, the results will provide a theoretical basis for assessing soil C emissions.[Method]An evergreen broad-leaved forest and two plantations converted from the natural forest, i.e., a Phoebe bournei stand and a Cunninghamia lanceolata stand in Xiqin Forest Farm of Fujian Agriculture and Forestry University were monitored. Four plots (20 m×20 m) were established in each stand and soil carbon dioxide fluxes were measured using an Automated Soil CO2 Flux System (Li-8100) over 25 months (from September 2014 to September 2016). Soil temperature, soil water content, organic C content, microbial biomass C content, soluble C content, annual litter biomass, fine root biomass (0-20 cm soil layer) and litter C/N were measured.[Results]Results showed that stand conversion significantly reduced soil C fluxes. The annual soil C fluxes decreased from 16.22 tC·hm-2a-1 in natural forest to 12.71 and 4.83 tC·hm-2a-1 in a Phoebe bournei stand and a Cunninghamia lanceolata stand, reduced by 21.6% and 70.2% respectively. Stand conversion resulted in increased temperature sensitivity of soil respiration. The Q10 values were ordered as follows:evergreen broad-leaved forest (1.97) < P. bournei stand (2.03) < C. lanceolata stand (2.91). The Q10 value of C.lanceolata stand was significantly higher than that of the evergreen broad-leaved forest(P<0.05). Soil temperature explained 89.70%, 88.50%, and 87.90% of the variation in soil respiration rate in the evergreen broad-leaved forest, P. bournei stand and C. lanceolata stand, respectively. There were no significant relationships between soil water content and soil respiration rate (P>0.05). Correlations showed highly significant positive relationships between soil respiration rate and soil organic C content, dissolved organic C, microbial biomass C, annual litter biomass, fine root biomass (0-20 cm soil layer) (P<0.01). Accordingly, the Q10 values were significantly positively correlated with litter C/N ratios, whereas it significantly negatively correlated with annual C fluxes and microbial biomass C (P<0.01). Further analysis showed that soil organic C and microbial biomass C were two important factors for determining the changes in soil respiration rates. However, litter C/N ratios were the most important regulators of Q10 values.[Conclusion]In central-subtropical area, stands conversion from evergreen broad-leaved forest to plantations for 35 and 38 years resulting in significant decreases in soil C fluxes, which were associated by shifts in tree species composition and structure, decreased quantity and quality of litters, fine root biomass, soil organic C and microbial biomass C. Soil temperature drove the seasonal changes in soil respiration, soil organic C and soil microbial biomass C were the key factors determine soil respiration rates, while litter C/N ratio was the most important factor of Q10 values. Our study highlights that soil organic C, soluble C and substrate quality should be incorporated into future models when predicting stand conversion effect on accuracy of soil C emissions.

Key words: conversion of stand type, evergreen broad-leaved forest, plantation, soil respiration rate, soil carbon stock, temperature sensitivity

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