Abstract
In a silvi-medicinal system, the plant secondary metabolites (PSMs) released from medicinal herbs could affect tree litter decomposition and nutrient release. However, the specific effects of PSMs on arboreous litter decomposition are still not well understood. In this study, the extracts of nine types of medicinal herbs were used to treat Pinus armandii Franch. and Larix gmelinii (Rupr.) Kuzen. litter during a simulated half-year decomposition. The effects of the extracts on the decomposition and the N and P release of the conifer litter were investigated. The results indicated that most of the medicinal herb extracts significantly inhibited the late decomposition of P. armandii litter, whereas only two of them accelerated the entire decomposition process. Only a few significantly affected the decomposition of the L. gmelinii litter. Four of the nine types of extract significantly inhibited the N and P release of the P. armandii litter, while 3/9 and 6/9 inhibited the N and P release of the L. gmelinii litter, respectively. The accelerating effects of the extracts on the cellulase activity and the inhibitory effects on the polyphenol oxidase activity might be responsible for the early acceleration and late inhibition of litter decomposition, while the effects of the extracts on the activities of protease and phosphatase might not be the main reason for the inhibitory or accelerating effects on the N and P release. In general, the inhibitory effects of medicinal herbs on the nutrient cycling of ecosystems should be taken into consideration when building silvi-medicinal systems, especially in P. armandii forests.
Highlights
Herbal medicine is one of the foundations of traditional medicine in various regions worldwide and plays crucial roles in disease treatment and primary health care [1,2]
The decomposition of the L. gmelinii litter was affected by very few medicinal herb extracts (Table 4); only the Houttuynia cordata Thunb. (HC) extract significantly (p < 0.05) accelerated the first half of its decomposition, but the same extract exhibited a significant inhibition in the second half
The results indicated that all the medicinal herb extracts, apart from Taraxacum mongolicum Hand.-Mazz. (TM), significantly affected the decomposition of the P. armandii litter, and that generally (66.7%) the first half of its decomposition was accelerated while the second half was inhibited
Summary
Herbal medicine is one of the foundations of traditional medicine in various regions worldwide and plays crucial roles in disease treatment and primary health care [1,2]. Due to the identification of therapeutic effects, the plantation of herbal medicines has developed rapidly and extended to Europe and America from traditional producing areas such as East, Southeast or Central Asia [2,4,5,6]. Medicinal herb plantations require a relatively specific temperature, air humidity, illumination and soil conditions. These herbs usually need to be planted for several years to attain a favorable quality [7]. The plantation of medicinal herbs usually occupies agricultural land over the long term. The long-term plantation of some medicinal herbs causes serious soil degradation, hindering the subsequent use of farmland [7,8,9]. Developing new plantation patterns is one of the most urgent demands in the sustainable development of medicinal herb plantations
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