Chin J Plant Ecol ›› 2008, Vol. 32 ›› Issue (6): 1227-1237.DOI: 10.3773/j.issn.1005-264x.2008.06.003

• Original article • Previous Articles     Next Articles

FINE-ROOT DECOMPOSITION OF FRAXINUS MANDSHURICA AND LARIX GMELINII PLANTATIONS

SONG Sen1, GU Jia-Cun1, QUAN Xian-Kui1, GUO Da-Li2, WANG Zheng-Quan1,*()   

  1. 1School of Forestry, Northeast Forestry University, Harbin 150040, China
    2Department of Ecology, Peking University, Beijing 100871, China
  • Received:2007-11-21 Accepted:2008-03-27 Online:2007-11-21 Published:2008-11-30
  • Contact: WANG Zheng-Quan

Abstract:

Aims Fine root decomposition is a major pathway of carbon and nutrient cycling in terrestrial ecosystems. Litterbag studies change the environmental conditions of root decay, so we employed a minirhizotron technique. Our objectives were to: 1) compare fine-root decomposition time and rate between ash (Fraxinus mandshurica) and larch (Larix gmelinii) in the same site, 2) analyze the effect of root diameter and root order on fine root decomposition and 3) investigate patterns of fine root decomposition in different soil depths.

Methods In October 2003, we established three 20 m × 30 m plots in each plantation, and randomly installed six minirhizotron tubes. From April 2004 to October 2006, video images were collected at approximately two-week intervals during the growing season. The interval from date of root death to disappearance was defined as decomposition time. Video images were digitized via RooTracker software (NC, USA). Kaplan-Meier method in survival analysis was used to generate cumulative remaining rate and median root decomposition time (MRDT), and factors of tree species, diameter, root order and soil depth were compared by logrank test.

Important findings Cumulative remaining rate of fine-roots in both species decreased gradually with time, with the decrease significantly faster for larch than ash (p<0.001).MRDT of larch was (82±7) d compared with (317±28) d for ash. TheMRDT of both species differed in three diameter classes (≤0.3, 0.3-0.6 and >0.6 mm). The finest roots (≤0.3 mm) of both ash and larch decayed slower than the other two diameter classes; however, only theMRDT of ash decreased systematically with increasing root diameter. With increasing root order, the cumulative remaining rate of both species increased significantly (p<0.05), resulting in a delay time of 82 d and 58 d ofMRDT for higher order compared with first order in larch and ash roots, respectively. The fine-root cumulative remaining rate of both species showed similar pattern among soil depths, which at 0-15 cm depth was significantly less than 15-30 and 30-45 cm (p<0.01). This study suggested that fine-root decomposition is a species-specific process, mutually controlled by internal factors (e.g., diameter) and external factors (i.e., soil depth). Decay of fine roots is faster than previous reported.

Key words: Fraxinus mandshurica, Larix gmelinii, fine-root decomposition, minirhizotron