Responses Of Soil Respiration To Soil Rewetting In Temperate Natural Forest And Larix Olgensis Plantation In Northeast China

Soil rewetting is an important ecological process that caused by the uneven distribution of precipitation. It strongly impacts on soil respiration (Rs).The effect of rewetting on Rs was measured every 10 days in each month in a natural forest and a Larix olgensis plantation in Maoershan Forest Research Station from May to September,2009. A simulate rainfall experiment was performed in field with different level (20 mm,40 mm,80 mm). At the same time we measured soil organic carbon mineralization (SOCM) under different temperature (5℃,15℃,25℃,35℃) and water addition (25%,50%,75%,100% mass water content) in lab. The results showed:(1) Under natural conditions, RS rate increased rapidly after soil rewetting. During June experimental period, with low soil water content, Rs rate after a rainfall was about 2-3 times than before. But during July experimental period, with high soil water content, Rs rate in natural forest reduced 17.96% after a strong rainfall. During period with several soil rewetting events, RS was positively related to soil water content (SWC). And the relationship between RS and SWC could described by Y=c+kW(P<0.05).(2) The contribution of heterotrophic respiration (RH) to Rs was 68.14%～98.31% in natural forest, and 54.43%～78.89% in Larix olgensis plantation. So with the similar dynamic between Rs and SH, the increase of Rs after rewetting was mainly contributed by RH. Except July and September, correlations between SWC and SH were not significant (P>0.05). However, responses of soil autotrophic respiration (RA) to rewetting were not similar among different seasons.(3) In the simulate rainfall experiment, except Rs of natural forest soil of 80 mm water treatment, both Rs and RH rate were increased by water addition. And except RH of Larix olgensis plantation of 80 mm water treatment, the increments of RS and RH rates declined with increase of water addition.(4) In the incubation experiment, soil organic carbon mineralization (SOCM) rates excited rapidly and reached the maximum in a few days (1-4 days) following rewetting treatment. With the increase of water addition, SOCM rates increased, both in natural forest and Larix olgensis plantation. But when temperature exceeded 5℃, SOCM rates of 100% water treatment were less than 75% water treatment in Larix olgensis plantation. Under high temperature (≥25℃) and moisture (50% to 100%) conditions, the rates of SOCM increased in natural forest were significantly larger than that in Larix olgensis plantation. In addition, moisture sensitivity coefficients (k) and temperature sensitivity coefficients (Q10) of SOCM in natural forest were greater than that in Larix olgensis plantation. In general, our study provides that soil rewetting could stimulate RS both in natural forest and Larix olgensis plantation. And the increase of Rs after rewetting is mainly contributed by RH. But the response of RS to rewetting is also influenced by soil temperature, soil moisture and forest type at the same time.