Mutual effects between Pinus armandii and broadleaf litter during mixed decomposition

Xiaoxi Zhang,Zengwen Liu,Boya Wang

doi:10.5586/asbp.3629

Abstract

Mixed-decomposition effects are commonly observed in natural and planted forests and affect nutrient cycling in a forest ecosystem. However, how one litter type affects the decomposition of another is still poorly understood. In this study, Pinus armandii litter was mixed with Betula albosinensis, Catalpa fargesii, Populus purdomii, Eucommia ulmoides, and Acer tsinglingense litter. The mixtures were placed in litterbags and buried in soil with consistent moisture for a 180-day indoor simulated decomposition experiment. The litterbags were periodically harvested during decomposition; the litter residues of different species were separated, and the biomass dynamics of each litter type were simulated. In addition, the soil sucrase, cellulase and polyphenol oxidase activities were also detected three times. The mutual effects of needle and broadleaf litter during mixed decomposition and the possible underlying mechanisms were investigated. The results indicated that (i) during the decomposition experiment, P. armandii needles significantly inhibited the decomposition of broadleaf litter in the first 3 months, while the broadleaf litter accelerated the decomposition of P. armandii needles in only approximately 40% of the cases. However, the inhibitory effects of needles on broadleaf litter decomposition subsequently exhibited significant weakening, while the accelerating effects of broadleaf litter were significantly enhanced. The effects of mixed decomposition on the activities of three enzymes can only partially explain the interactions between different litter types; (ii) the prediction by the decomposition model showed that most of the broadleaf litter types could continuously accelerate the decomposition of P. armandii needles throughout the mixed decomposition process, while the decomposition of broadleaf litter would be significantly inhibited at least in the short term. In general, four of the five broadleaf litter types (excluding E. ulmoides) could accelerate the early decomposition of P. armandii needles and consequently accelerate nutrient cycling in P. armandii pure forests. These species could be used for the transformation of pure P. armandii pure forests to mixed forests.

Highlights

The Qinling Mountains are the climatic and biogeographic boundary between Northern and Southern China
Regarding the actual mutual effects, when synergistic effects were observed, the decomposition of P. armandii litter was usually significantly accelerated in the mixtures, while that of broadleaf litter was not affected (Fig. 2A,F and Fig. 2C,H)
Pinus armandii × P. purdomii mixing significantly accelerated the decomposition of the former species in the fourth–sixth months, while it significantly inhibited that of the latter species in the third month

Summary

Introduction

The Qinling Mountains are the climatic and biogeographic boundary between Northern and Southern China. Pinus armandii is one of the most widely disturbed species in the secondary and artificial forests in the Qinling region. This species exhibits considerable self-renewal ability; it is difficult for other species to expand into P. armandii forests, leading to low biodiversity of these pure forests [1]. Due to the long-term selective utilization of nutrients and the specific characteristics of litter decomposition and nutrient release, P. armandii forests have exhibited unique soil degradation patterns, such as the loss of available N, P, and microelements and remarkable decreases in urease, sucrase, phosphatase, and protease activities [2]

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Conclusion