Objective  This paper aims to improve the utilization rate of tending residues of Larix principis-rupprechtii, explore the influence of different treatment methods on the decomposition rate of tending residues, accelerate the decomposition rate of tending residues, restore the land fertility of Larix principis-rupprechtii plantations, and maintain long-term high productivity.

  Method  In this study, tending and thinning residue of Larix principis-rupprechtii plantation was used as research subject. And 4 treatment methods, including smashing residue, adding urea, EM and wood vinegar, were used to design a 4 factor and 5 level orthogonal experiment.

  Result  The results show that the decomposition rate of No.9 treatment was the highest, and levels of each factor were: particle diameter (0.3−0.5 cm), urea solution (9 kg/m³), dilution times of EM bacteria (1 000) and dilution times of wood vinegar (0 times). The decomposition rate of No. 9 was 2.04 times of the lowest decomposition rate of No. 22. The effects on decomposition of Larix principis-rupprechtii tending residue through 25 treatments were studied and the optimum level of the 4 factors which is conducive to the decomposition of residues was obtained: particle diameter (0.3−0.5 cm), urea solution (3−9 kg/m³), dilution times of EM bacteria (500) and dilution times of wood vinegar (600 to 800 times). It can be seen from the optimal processing combination of No.9 that the level of each factor is not necessarily in the best level, and we could speculate that there might be an interactive effect, but it still needs to be proved.

  Conclusion  Through the study of using different treatment methods to deal with tending residues, particle diameter was the most influential factor on the decomposition rate of the residue, and the interaction of the 4 factors is generally greater than that of unitary urea solution, EM or wood vinegar. In order to accelerate the decomposition of tending residues and maintain the high productivity of plantation, the reference methods were put forward.