organic carbon content and rates of sequestration in soils of albania
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Organic Carbon Content and Rates of Sequestration in Soils of AlbaniaPandi Zdruli, Hari Eswaran,* and John Kimble
ABSTRACTSoil organic carbon (SOC) was measured in 17 pedons, representing
major agricultural soils in Albania. The soils studied were Inceptisols,Vertisols, Mollisols, and Alfisols. Within each order, the wet members(aquic suborders) had 10 times or more SOC than their well-drainedcounterparts. Radiocarbon dates were determined on wood fragmentsfound in a few of the soils. The steady-state rates of accumulationrange from 20 to 60 g m"1 m"2 yr"1 in the wet soils. Only onewell-drained soil was available for comparison and this had an accumu-lation rate of SOC of
ZDRULI ET AL.: ORGANIC CARBON CONTENT AND SEQUESTRATION RATE 1685
Table 1. Organic C content of some soils of Albania.
Vertic HalaqueptUdifluventic UstochreptUdic UstochreptFluventic Xerochrept
Typic EndoaquertAquic HaploxerertUdic HaploxerertChromic-Udic Haplustert
Pachic CalciustollVertic ArgiaquollPachic CalcixerollFluventic HaplustollUdic CalciustollTypic Argiudoll
Aquic HaplustalfUdic HaplustalfUdic Rhodustalf
Total organic C
t STR is soil temperature regime; M = mesic; T = thermic.
The soils of the central and southwestern coastal plainshave a xeric SMR, which changes to ustic northward.The eastern part of the country and the mountainousareas have a udic soil moisture regime. In the well-drained soils, the soil composition and environment,including SMR and STR, determine the rate and amountof SOC production. The net accumulation is also deter-mined by the extent of losses or gains through erosion.In the wetter soils, in comparison, the accumulation ratesand thus the net amounts are accentuated by the prevalentanaerobic conditions. Most of the poorly drained soilsoccur in basin or depression landscape situations with ahigh input of SOC through erosion products. Micromor-phological analysis (Zdruli, 1995, unpublished data)showed microstrata of partially decomposed SOC in thesesoils of sedimentary origin.
Wetness also influences the depth of SOC accumulation(Table 1). In well-drained soils, most SOC accumulationoccurs in the top 30 cm of the soil. In the poorly drainedsoils, more than 50% of SOC is present at depths >50cm. This is due to stratification in the soils, as shownin the micromorphological study (Zdruli, 1995, unpub-lished data).
Table 2 provides the radiocarbon age of wood frag-
Table 2. Rate of organic C (OC) accumulation in Albanian soils.
ments hand picked at the depths shown. The amount ofSOC in the layers above this depth was computed andfrom this, rates of SOC accumulation were calculated(Table 2). The rates are expressed both on a 1-m soildepth over an area of 1 m2 and also on a hectare basis.In the soils with high water table, the steady-state rateof accumulation ranges from 20 to 60 g m"1 m~2 yr"1(or 0.2-0.6 kg irT1 ha~' yr"1). The only pedon (Pedon005) of a well-drained soil (from which wood fragmentswere available for dating) snowed a value
1686 SOIL SCI. SOC. AM. J., VOL. 59, NOVEMBER-DECEMBER 1995
Table 3. Changes in soil organic C (SOC) due to drainage inPedon 16.
90.338.6 (57.2)t17.5 (80.6)
0-50 cm. _, _ 2
141.152.7 (62.7)30.3 (78.5)
221.487.5 (60.5)65.6 (70.4)
t Percentage loss from 1956 (year of drainage) in parentheses.
of the surface soil material in Pedon 16 was too low toclassify as a histic material, so the soil was classified asa Vertisol. Prior to 1956, the area was a swamp butwas drained and reclaimed for agricultural use in 1956.Bajraktari and Xinxo (1972) studied the soils beforeand after reclamation and showed a marked decrease inorganic C content. Table 3 and Fig. 1 show this decline(the 1994 data coming from our study). In the 1-mcontrol section, there was a 60% decrease in total SOCduring the period 1956 to 1972 and, for the period1956 to 1994, the decrease was about 70%. The rate ofdecrease is about 0.026 kg m~' m~2 yr~ ' . Part of thedecrease is due to oxidation of the SOC and part is dueto subsidence. As the organic component of even thetopsoil is not high, subsidence was not expected to con-tribute significantly to the SOC decrease.
The rate of SOC decrease resulting from drainage ismuch smaller (26 g m~' m~2 yr~ ' during the 38-yrperiod) than the SOC accumulation rate, which was about210 g m~' nT2 yr~ ' (during 2000 yr) in the one pedonstudied. For the accumulation rate, the SOC contentprior to drainage of the soil (Table 2) was used forcomparison. Most of the decrease was probably due tooxidation and mineralization of the non- or partiallydecomposed woody tissue materials.