**3. Mechanism of cultivation practice for Chinese medicinal herbs under forest**

Without chemical fertilizers and pesticides, *P. notoginseng* has been successfully cultivated in forest ecosystems. It was based on the principle of biodiversity for pest control. Most of *P. notoginseng* was cultivated in coniferous forest [*Pinus kesiya* var. *langbianensis*, *Pinus yunnanensis*, *Pinus armandii Franch*. and *Cunninghamia lanceolata* (Lamb.) Hook] (**Figure 1**). The cultivation of *P. notoginseng* under-forest conditions is successful due to the effective use of (i) native environment and biodiversity and (ii) stimulatory allelopathic interactions within the forest system (**Figure 2**).

**Forest environment:** *P. notoginseng* is shade-loving plant that thrives well under low light intensity and 18–25°C temperature. When the light intensity is >30% of sunlight and temperature is over 30°C, the growth environment becomes harsh for *P. notoginseng*. The environment in the lower layers of forests provides desirable shade and temperature for P*. notoginseng* growth. Compared with traditional cultivation model, this forest cultivation model does not use polyethylene net or straw to provide shade, which greatly reduces the cost. Besides, the leaf litter acts as cover, keeps the soil moist, and maintains suitable temperature for *P. notoginseng* growth.

**Soil rich in organic matter and microbes:** Long-term decomposition of forest residues improves the soil quality. We found that the physicochemical properties of coniferous forest soil meet the requirements of *P. notoginseng* (pH: 5.5–6.5; electrical conductivity: 60–120 μS cm−1; nutrient contents: 250–360 mg kg−1 available N, 10–25 mg kg−1 available P, 100–260 mg kg−1 available K, and 80–120 g kg−1 soil organic matter). Such soil provides adequate nutrients for *P. notoginseng* growth and development of strong root system (**Figure 1**).

Forest soils are generally rich in microorganisms, which reduces the root rot disease and promotes the plant growth by increasing the availability of nutrients. Our laboratory experiments showed that application of microbiome from the forest soil into sick soil improves the germination and growth of *P. notoginseng* and alleviates the soil-borne diseases. Bacteria with strong antifungal activity (*Bacillus* spp., *Pseudomonas* spp., *Streptomyces* spp., *Burkholderia* spp. etc.), against *P. notoginseng* root

*Cultivation Practice of Chinese Medicinal Herbs DOI: http://dx.doi.org/10.5772/intechopen.104859*

#### **Figure 1.**

*Cultivation of* P. notoginseng *under forest conditions. A.* Pinuskesiya var. langbianensis *forest; B.* Pinus yunnanensis *forest; C. C*unninghamia lanceolata *(Lamb.) Hook. forest; D.* Pinus armandii *Franch. forest; E. Broadleaf forest; F. The strong roots of* P. notoginseng *in forest soil.*

rot pathogens, have been isolated and identified from forest soil. Besides, the atmospheric nitrogen-fixing microbes (*Bradyrhizobium* spp., *Rhizobium* spp., *Frankia* spp. etc.) are also abundant in forest soils [42].

**Allelopathic interactions in forest.** Cultivation of *P. notoginseng* under natural forest conditions uses the allelopathy to stimulate the plant growth and prevents the pests and diseases infestation than in monoculture in farmland or greenhouses. The possible pathways for the release of allelochemicals into the environment are: (i) emission of volatile organic compounds (VOCs) from different plant tissue, (ii) leaching from leaves by rain or dew, (iii) decay of plant residues, and (iv) root exudation.

The VOCs of pine tree terpenes (including α-pinene, β-pinene, camphene, etc.) stimulated the growth and reduced the pests and diseases of *P. notoginseng*. Riedlmeier et al. [43] reported that monoterpenes, particularly pinenes, could enhance the systemic acquired resistance in *Arabidopsis thaliana* to the pathogen *Pseudomonas syringae*. Likewise, our results showed that some VOCs from pine needles induce the resistance of *P. notoginseng* to leaf black spot disease (caused by *Alternaria tenuis* Nees). In addition, α- terpineol and terpinen-4-ol are antifungal to growth of fungal pathogens (*Fusarium oxysporum*, *Fusarium solani*, *Cylindrocarpon destructans*, *Phytophthora cactorum*, and *A. tenuis* Nees) (unpublished). It is also observed that leachates from pine needles stimulated the growth and biomass of *P. notoginseng*. Terpenes are one kind of VOCs, from the herbivore damaged plants that attract the predators or parasitoids to attack herbivores [44]. Aldrich et al. [45] reported that an artificial pheromone containing α-terpineol and Terpinen-4-ol emitted from pine could attract the adult predaceous spined soldier bugs, *Podisus maculiventris* (Say).

#### **Figure 2.**

This confirms that the VOCs from coniferous forests play a positive allelopathic role in pest control.

Cao et al. [46] investigated the diversity of arthropods on *P. notoginseng*, planted in *P. kesiya* var. *langbianensis* forest. The data showed that there were a total of 40 species of arthropods from 33 families, of which the natural enemies were 40%. The Shannon-wiener diversity index of natural enemy subcommunity is significantly higher than the pest subcommunity. Obviously, a high biodiversity of arthropods significantly reduces the damage caused by pests in *P. notoginseng*.
