Key words Environmental factors, Organic carbon decomposition, Agricultural soils, Incubation experiment, Climate change.

Transcription

1 CHIN ESE JOURNAL OF APPL IED ECOLO GY,J un. 2002,13 (6) (, ) C,,,, C., C ;,C., C., C. 300g kg g kg - 1, C, 200g kg - 1,., C (2002) S A Influence of environmental factors on the decomposition of organic carbon in agricultural soils. HUAN G Yao, L IU Shiliang,SHEN Qirong and ZON G Lianggang ( College of Resource and Environmental Sciences, N anjing A gricultural U niversity, N anjing ). 2Chin. J. A ppl. Ecol.,2002,13 (6) : To quantitatively investigate the effects of environmental factors on organic carbon decomposition, CO 2 2C was measured from the incubation of wheat and rice straw as well as their roots mixed with a paddy soil over a 902day period. Results showed that decomposition of the straw carbon was faster than that of the roots. Amount of CO 2 2C released from the organic matter decomposition was quantitatively related to its properties of C/ N ratio. Increase of temperature within a lower temperature range enhanced greatly the decomposition while such an enhancement weakened within a higher temperature range. Under the moist condition, the temperature coefficient of organic carbon decomposition declined exponentially with the incubation time. The temperature coefficient did not significantly decrease with the time for the submerged condition after one2week incubation. The effect of water status showed that the decomposition at the water contents of 300g kg - 1 and 500g kg - 1 was faster than that under the treatments of 200g kg - 1 and the submerged. Within the first month period of incubation,carbon released from the incubation of wheat straw was negatively related to the clay fraction of the soils. Key words Environmental factors, Organic carbon decomposition, Agricultural soils, Incubation experiment, Climate change. 1, CO kg C, [2,16,21 ], CO 2 CO 2 [17 ]. CO 2 ( ). CO 2 [5,10,14 ],, CO 2., [8 ],. C [7 ] [4,6 ] [3,19 ] [12 ].. C., C [8,13,14,20 ],C. C CO 2, C , 20, 1. 3 ( ) ,

2 C, C.,2. 1 Table 1 Physical and chemical properties of soils used Sampling location p H ( H 2 O) C N Total C Total N (g kg - 1 ) (g kg - 1 ) C/ N < 01005mm clay content Hongta, Yixing Dapu Yangwei Yangxi Xindu Mingling Ganli Xinzhuang Tangjiao Fenshui Honghu Youtang Lidu d,.,C. [11 ], C, ( ) ( ). C,. 2,,. 2 Table 2 Properties of organic materials used( g kg - 1 ) Organic materials C N C/ N Lignin Wheat straw Wheat root Rice straw Rice root Bartha [1 ], 650ml, NaOH C CO 2. NaOH,CO 2 2C., 100g. 3 6mm, 70, 1g., , 3. 4 ( ) g kg - 1, 3 50 % 60 % 70 % 80 %.,. C MPa,., C 4 300g kg CO 2 1, C 2. 1,CO 2,, > > >. 2, ( 0 30d), C,,, 1 CO 2 Fig. 1 Cumulative of carbon mineralized from different organic materials in paddy soil. 1 Rice straw, 1 Rice root, 1 Wheat straw, 1 Wheat root. The same below. 2 C Fig. 2 Decomposition rate of carbon from different organic materials., C C. 3 4 C, C. 3, 90d, C C 50 %, C 30 %. 30d, C C 30 %, C 20 %.,C/ N C,. C ( Y ) C/ N ( L ) :

3 6 : C ( C %) 3 Table 3 Amount of CO 2 2C released from the decomposition of different organic materials ( % of added C) Organic materials C 0 30 rate C Incubation periods (d) rate C rate C 0 90 decomposed Wheat straw Wheat root Rice straw Rice root , 300g kg - 1. Incubated at 24 and water content of 300g kg - 1. Y = a + b[c/ N ]/ L (1), a b,. ( 4),, C,. 90d, (1). 4 Y = a + b[ ( C/ N) / L] Table 4 Parameters and statistical testing for the equation of Y = a + b [ ( C/ N) / L] Incubation periods(d) a (mg C ) b (mg C ) , N C/ N.,. (C / C ) [22 ],,C/ N ; C/ N,. (C/ N 5110, 132g kg - 1 ) ( C/ N 1118, 135g kg - 1 ) ( C/ N 1112, 202g kg - 1 ) N C/ N. 312 C (300g kg - 1 ) CO ,12 C,, 90d , ( 15d) C, ,4, r C C ,30d C ;24 36, C ,, C ;,C. [6,9 ]. 3 CO 2 Fig. 3 Cumulative of carbon mineralized from wheat straw in paddy soil at different temperatures. 5, (0 30d) C,, C. C, ( ) 4 Q 10.,,C 2, , 90d,. Q 10, 215,, Q 10, 30d, Q 10 1.,,, C ( Q 10 1). 4

4 C 3 Table 5 Amount of CO 2 2C released from incubation experiments at three temperature levels Organic materials Incubation temperature ( ) C 0 30 increment Incubation periods (d) C increment C increment Wheat straw Wheat root C The decomposed implies the of CO 2 2C released from the organic materials and the soil.., C Q 10 t (d) : Q 10 = 0192exp (616/ t) (0 < t 90) ( r = , n = 11) (2) 4 Fig. 4 Change of temperature coefficient with incubation time. Submerged,. Moist, Exponential fit., C [6,9 ], 5., C. ( Substrate sources),,,,( ).,,,, C. 313 C (24 ) C 5. 5, 90d, g kg - 1, C,, 200g kg - 1.,. 5 CO 2 Fig. 5 Cumulative of carbon mineralized from wheat straw in paddy soil with different water content. 1) 200g1kg - 1,2) 300g kg - 1,3) 500g kg - 1,4) Submerged. The same below. C. 6 24, C. 6,,C, g kg - 1 : C 34 %,C 17 %. 200g kg - 1, C 20 %, C 10 %., C, C. 90d, 4 ( g kg - 1 ) C %, C % [3 ], 2 15g kg - 1,C

5 6 : C ( C %) 3 Table 6 Amount of CO 2 2C released from the decomposition of organic materials at different water status ( % of added C) Organic materials Water content (g kg - 1 ) C 0 30 rate C Incubation periods (d) rate C rate C 0 90 rate Wheat straw Submerged Wheat root Submerged Rice straw Submerged Rice root Submerged Incubated at 24. (70 %WHC).,., C,> 500g kg - 1 > 300g kg - 1 > 200g kg - 1 ( 6) C, 8 3 (0 30d 31 60d 61 90d) C. 8, 90d, C,. Y = X ( r = , n = 6) (3), Y ( mgc), X 6 C Fig. 6 Cumulative of carbon mineralized from paddy soil with different water content. 314 C,,., C, ( ) [15,18 ].,,. ( 1) (10g kg - 1,36, MPa ),, C, 7 CO 2 Fig. 7 Cumulative of carbon mineralized from wheat straw in paddy soils with different clay contents. 1) 165g kg - 1,2) 313g kg - 1,3) 463g kg C Fig. 8 Relationship between carbon mineralized from wheat straw in paddy soils and soil clay content. 1) 0 30d,2) 31 60d,3) 61 90d.

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