Decomposition rate-constants

Coefficients and SE's (in parenthesis) of the regressions of percent mass remaining over decomposition time used to estimate decomposition rate constants for species studied in four regions of Russia from west to east

		Regression coefficients ^a
		Snags					Logs
Species	Regions	Y₀(%)	k (year^-1)	p-value^*	N	Adj. r²	Y₀ (%)	k (year^-1)	N	Adj. r²
Betula pendula Betula costata Picea abies P. obovata P. ajanensis Pinus sylvestris Larix siberica Larix dahurica Pinus siberica P. koraiensis	St.-Petersburg Krasnoyarsk Irkutsk Khabarovsk Khabarovsk St.-Petersburg Krasnoyarsk Khabarovsk St.-Petersburg Krasnoyarsk Irkutsk Krasnoyarsk Irkutsk Khabarovsk Irkutsk Khabarovsk	92.68 106.53 108.11 130.92 108.63 118.35 98.53 125.24 103.85 97.13 103.25 101.45 102.49 93.56 88.02 86.66	-0.027 (0.008) -0.056 (0.009) -0.052 (0.009) -0.077 (0.022) -0.071 (0.003) -0.044 (0.018) +0.0006 (0.0043) -0.035 (0.003) -0.037 (0.009) +0.020 (0.011) -0.004 (0.003) -0.004 (0.005) -0.010 (0.001) -0.009 (0.012) -0.003 (0.001) -0.003 (0.002)	0.0185 0.0001 0.0001 0.0185 0.0001 0.0710 0.8957 0.0001 0.0012 0.1121 0.2383 0.4168 0.0001 0.4801 0.0092 0.3030	7 13 17 7 7 6 8 14 14 8 19 8 28 10 17 12	0.64 0.78 0.67 0.64 0.99 0.50 -0.16 0.92 0.56 0.26 0.03 -0.04 0.64 -0.05 0.33 0.02	100.00 107.08 86.56 118.73 79.13 82.48 110.58 96.59 81.76 120.60 111.20 90.23 99.72 80.70 88.55 86.79	-0.054 (0.013) -0.061 (0.006) -0.042 (0.004) -0.078 (0.008) -0.030 (0.003) -0.026 (0.003) -0.049 (0.006) -0.028 (0.002) -0.027 (0.005) -0.044 (0.003) -0.036 (0.003) -0.023 (0.002) -0.031 (0.002) -0.015 (0.002) -0.019 (0.002) -0.015 (0.001)	11 28 41 20 23 20 31 39 42 31 35 30 42 26 33 35	0.62 0.81 0.75 0.82 0.81 0.78 0.68 0.83 0.46 0.85 0.84 0.85 0.83 0.66 0.66 0.87

^a The regression was of the form Y_t = Y₀ * e ^-kt where Y_t is the percentage of the mass remaining at time t (years), Y₀ is the initial mass in percent dry weight, and k is the decomposition rate constant
^* P-value for the comparison of decomposition-rate constants to zero

The decomposition rate-constants ranged from -0.015 to -0.078 for logs and from -0.077 to +0.020 for snags. Some differences and some similarities were observed among decomposition rates within each species among the regions as well as within each region among the species. The differences between decomposition rates of logs and snags were fairly high for some species. In general, decomposition rates of logs were higher than those of snags. The most similar rates were in the white pine group. The log decomposition rate of Pinus siberica was not different from the log decomposition rate of Pinus koraiensis (p-value of 0.1355), as snag decomposition rate of Pinus siberica was not different from snag decomposition rate of Pinus koraiensis (p-value of 0.837).

The decomposition rates of logs were in general higher than those of snags for larch and white pine, whereas for birch the decomposition rates of logs and snags were similar. Comparison between decomposition rates of logs and snags of Picea ajanensis in Khabarovsk region, and Pinus siberica and Larix siberica in Irkutsk region indicates that while decomposition rates of logs and snags are not significantly different for Picea ajanensis (p-value of comparison 0.121), they are different for Pinus siberica and Larix siberica (p-values of 0.002 and 0.001, respectively).

Decomposition time range of sampled logs and snags in different regions

Species	Regions	Snags	Logs
Betula pendula Betula costata Picea abies P. obovata P. ajanensis Pinus sylvestris Larix siberica Larix dahurica Pinus siberica P. koraiensis	St.-Petersburg Krasnoyarsk Irkutsk Khabarovsk Khabarovsk St.-Petersburg Krasnoyarsk Khabarovsk St.-Petersburg Krasnoyarsk Irkutsk Krasnoyarsk Irkutsk Khabarovsk Irkutsk Khabarovsk	0 - 12 0 - 15 1 - 8 2 - 15 1 - 13 2 - 7 2 - 15 1 - 71 1 - 13 0 - 4 1 - 19 0 - 15 1 - 65 8 - 19 2 - 65 1 - 31	0 - 30 0 - 29 1 - 33 0 - 27 2 - 77 2 - 73 0 - 33 2 - 77 0 - 70 0 - 45 1 - 42 0 - 110 1 - 90 0 - 104 0 - 65 0 - 160

Time periods (years) required for a given percent of mass to decompose

Regions	Species	50% mass	95% mass	99% mass
St.-Petersburg Krasnoyarsk Irkutsk Khabarovsk	Betula pendula Pinus sylvestris Picea abies Betula pendula Picea obovata Pinus sylvestris Larix siberica Betula pendula Pinus sylvestris Larix siberica Pinus siberica Betula pendula Betula costata Picea ajanensis Larix dahurica Pinus koraiensis	13 18 19 12 16 20 26 13 22 22 30 11 15 24 32 37	55 103 108 50 63 72 126 68 86 97 151 41 92 106 185 190	85 163 170 77 96 109 196 106 131 148 236 61 146 163 293 298

The species ranking by their decay resistance indicate that birch is the fastest decaying species, usually followed by spruce and pine, with larch and white pine being the most decay resistant species. This pattern holds for all species and regions sampled as indicated by CWD half-life, and time required for 95 and 99% of the mass to decompose.

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Questions? Email Dr. Mark Harmon at mark.harmon@orst.edu or Dr. Olga Krankina at olga.krankina@orst.edu

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