Carbon storage and allocation in Cunninghamia lanceolata plantations with different stand ages.

Abstract

Based on survey of 45 plots (1000 m2 each) of five different stand ages, i.e., young, middle-aged, pre-mature, mature, and over-mature plantations, in the main production area of Cunninghamia lanceolata in the north of Guangxi, China, carbon (C) storage and its allocation in vegetation and soil were studied. The results showed that total carbon storage of C. lanceolata plantations changed in the order of over-mature plantation (345.59 t·hm-2) > mature plantation (331.14 t·hm-2) > pre-mature plantation (299.11 t·hm-2) > young plantation (187.60 t·hm-2) > middle-aged plantation (182.81 t·hm-2). For all the stand ages, soil stored the greatest amount of carbon, C pool in vegetation layer was the second, while C storage in the litter layer was lowest. On average, C storage in belowground layer was greater than that in aboveground layer. Carbon storage in aboveground vegetation layer ranged from 34.80 to 134.55 t·hm-2, which contributed 18.6% to 38.9% to the total ecosystem carbon storage and increased with ages. Carbon storage in the litter layer ranged from 1.26 to 2.07 t·hm-2, which only contributed 0.4%-1.1% to the total ecosystem carbon storage. Carbon storage in the soil layer ranged from 149.24 to 206.02 t·hm-2 and represented 61.9%-80.0% of ecosystem carbon storage. Canopy layer stored the highest amount of carbon (33.51-133.7 t·hm-2) and comprised 92.8%-98.9% of aboveground vegetation carbon storage. Within the canopy layer, carbon storage differed with compartments. Stems stored the highest amount of carbon (20.98-95.68 t·hm-2) by accounting for 62.6%-72.6% of carbon storage in the canopy layer, which increased with ages. The branches and leaves accounted for 4.8%-11.0% and 11.1%-14.2% of C stored in the canopy layer, respectively, which all decreased with ages, while increased to some extent in the over-mature plantation. Roots occupied 11.3%-12.3% of carbon storage in the canopy layer with small fluctuation with the stand age.