Prized edible Asian mushrooms: ecology, conservation and sustainability
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- Mortimer, P.E., Karunarathna, S.C., Li, Q. et al. Fungal Diversity (2012) 56: 31. doi:10.1007/s13225-012-0196-3
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Mushrooms can be found in forests worldwide and have long been exploited as resources in developed economies because of their important agro-industrial, medicinal and commercial uses. For less developed countries, such as those within the Greater Mekong Subregion, wild harvesting and mushroom cultivation provides a much-needed alternative source of income for rural households. However, this has led to over-harvesting and ultimately environmental degradation in certain areas, thus management guidelines allowing for a more sustained approach to the use of wild mushrooms is required. This article addresses a selection of the most popular and highly sought after edible mushrooms from Greater Mekong Subregion: Astraeus hygrometricus, Boletus edulis, Morchella conica, Ophiocordyceps sinensis, Phlebopus portentosus, Pleurotus giganteus, Termitomyces eurhizus, Thelephora ganbajun, Tricholoma matsuake, and Tuber indicum in terms of value, ecology and conservation. The greatest threat to these and many other mushroom species is that of habitat loss and over-harvesting of wild stocks, thus, by creating awareness of these issues we wish to enable a more sustainable use of these natural products. Thus our paper provides baseline data for these fungi so that future monitoring can establish the effects of continued harvesting on mushroom populations and the related host species.
KeywordsMushroom speciesGreater Mekong Sub-regionMedicinal foodsNon-timber forest products
Mushrooms are highly prized for their value as nutritional (Chang and Buswell 1996; Chang and Miles 2004; Carlile and Watkinson 1994) and medicinal foods (Chang and Buswell 1996; Kendrick 2000; Moore et al. 2011), for their use in cosmetics (Hyde et al. 2010), as well as their unique flavors. Several edible mushrooms are cultivated and are available in local markets and shops all year round e.g. oyster mushrooms (Pleurotus ostreatus (Jacq.) P. Kumm.), ear mushrooms (Auricularia polytricha (Mont.) Sacc.), straw mushrooms (Volvariella volvacea (Bull.) Singer), Lentinula edodes (Berk.) Pegler and Flammulina velutipes (Curt.) Singer, while a large number of edible wild mushrooms are seasonally harvested. Because these wild harvested mushrooms usually have a short growing season and a high demand, they may suffer from over exploitation and usually fetch higher prices. As an example of what a resource these mushrooms can be to local communities, in Yunnan Province, China, up to 700 species of wild mushrooms are known to be edible and are utilized by local indigenous people as both a source of food and income.
Furthermore, local people consume a wide range of mushrooms for their medicinal properties. Many mushrooms are unique to an area, which would drive up the market price of these species, and in turn promote over harvesting. For example, in Laos and Thailand, Astraeus hygrometricus (Pers.) Morgan (hed torp) and Phlebopus portentosus (Berk. & Broome) Boedijn (hed ha) are uniquely consumed in the region, while another edible species, Pleurotus giganteus (Berk.) Karunarathna & K.D. Hyde occurs abundantly but is not consumed. Thus, education of local peoples may result in establishing new sources of foods and income for these people.
Because of uncontrolled picking and habitat loss, many species are being overexploited and their populations are in decline (Koune 2001). Management of wildlife habitats, including forests and plantations, is important in order to maintain wildlife populations, produce non-timber forest products as well as to support the lives of rural settlements. The management of habitats for mushroom production is one example where more effort is needed in order to conserve mushrooms and increase their productivity. This paper therefore reviews the status of ten highly prized edible wild mushrooms in the Greater Mekong Subregion (China, Thailand, Laos) and gives a background to their use, value, and ecology.
The mushrooms are dealt with in alphabetical order and no inference should be made to their order of importance.
For the purpose of this paper a descriptive chart has been adapted from the work of Cunningham and Yang (2011), which depicts the change in mushroom species composition with vegetative successional changes, see Chart 1. The chart is separated into ecological zones (1–6), depicting optimal habitats for the respective mushroom species. Zone 1 represents Alpine rangelands; zone 2 depicts grasslands, initial successional stages (0–5 years); zone 3 represents young forest stands, early successional stages (5–10 years); zone 4 shows the immature forest stands, early-mid successional (10–20 years); zone 5 is that of older forest stands, mid successional (20–30 years) and zone 6 depicts mature forests, in the late successional stages (30 years and older).
Astraeus hygrometricus (Pers.) Morgan
Common names: hed torp, hed phor (Thai & Laos)
Habitat and distribution
Habitat zone 3–6
Astraeus yields depend on the conservation of Dipterocarp forests, and the most sustainable manner for conserving and/or increasing wild production of Astraeus is to conserve the Dipterocarp forest systems. Astraeus fruit bodies are half-hidden in the soil and thus it is difficult to find them on the ground especially when litter is present, therefore special knives or metal implements are used to find the mushrooms. This has led to the local belief that burning should be carried out during March to April each year before the wet season to increase yields (Dell et al. 2000, 2005; Ruksawong et al. 2001). The burning not only affects the ecology of the forests and destroys wildlife, but has serious consequences on the health of the human population of northern Thailand, as air quality becomes extremely poor during this period. In addition, the number of people living in northern Thailand has also increased leading to an increased demand for Astraeus, thus putting further strain on the forest ecosystem (Dell et al. 2005). Yields of saprobic and other ectomycorrhizal mushrooms have been shown to decrease following burning, while sustained or naturally conserved forests produce a greater number of mushrooms (Sysouphanthong et al. 2010). However there is no specific data available on the effects of burning on Astraeus yields.
Boletus edulis Bull. ex Fr
Common names: porcini (Italian), cep and penny bun mushroom (English), zhutui mo and dajiao gu (Chinese)
Boletus mushrooms are ectomycorrhizal fungi known to form relationships with coniferous and deciduous tree species. Boletus edulis and related species are amongst the most highly traded mushroom species worldwide, reaching an annual consumption of up to100 000 tonnes/year (Hall et al. 1998a, b). Not only sought after for its culinary value, B. edulis is also known for its health and medicinal benefits. Containing a vast array of compounds used in anti-cancer treatments, as antioxidants, for blood fat reduction, as a source of ergosterol (a vitamin D precursor) and containing anti-viral compounds known to inhibit key enzymes of the HIV virus, B. edulis is well suited for many health related issues (Daba and Ezeronye 2003; Zheng et al. 2007).
Habitat and distribution
This mushroom is widely distributed in tropical and semi-tropical areas of North America and Mexico. In Europe it is found between the Scandinavian countries in the north and Greece and Italy in the south; the range then extends through Afghanistan, India, Nepal, Tibet and into China (Hall et al. 1998a, b). In China, the distribution of B. edulis lies between Jiling in the north and Hainan provinces in the south and usually between 300–2000 masl. During the growing season (June to September), the fruiting bodies can be easily found in broad-leaf or mixed forest (Fig. 3). The known host trees of Boletus edulis belong to Pinaceae, Taxodiaceae, Betulaceae, Fagaceae, Fabaceae, Dipterocarpaceae and Myrtaceae families (Zang 1997).
Boletus edulis is adaptable in its growing conditions, occurring in both saline and alkaline environments (Liang et al. 2004). Although fruit bodies may appear any time from summer to autumn, their growth is usually triggered by rainfall during warm periods of weather followed by frequent autumn rain with a drop in soil temperature (Hall et al. 1998a, b). Furthermore, a study conducted by Kasparavicius (2001) concluded that the maximal daily growth rate of the cap (about 21 mm) occurred when the relative air humidity was the greatest, and the fruit bodies ceased growing when the air humidity dropped below 40 %.
Habitat zone 5
Boletus edulis has the ability to grow under both young and mature stands of trees, for example, in Spain it is known to occur in conjunction with the pioneer species Cistus ladanifer, whereas it is also found in mature forests of Pinus, Betula and Quercus (Hall et al. 1998a, b; Li and Song 2003; Ponce et al. 2011). In China and the surrounding region it is known to occur mainly in older stands and is found in association with Pinus massoniana, P. tabulaeformis, P taiwanensis and Quercus mongolica (Li and Song 2003). Thus, in the Greater Mekong Subregion, the habitats for this mushroom species are generally older landscapes vegetated by forests in the late successional stages of development.
In 2010 a total of 10572 tonnes of B. edulis was exported from China worth US $71.83 m, showing a 15 % increase from 2009 (China customs report). This increased demand has led to overharvesting of natural stocks, as B. edulis cannot be artificially cultivated due to its mycorrhizal nature. The negative impacts of overharvesting, habitat fragmentation and human induced disturbances have further resulted in a decline of available stocks (Su et al. 2007; Wang et al. 2011). However, successful management practices, such as habitat protection, canopy management, and insect and disease prevention have led to increased B. edulis production in certain areas (Su et al. 2007; Wang et al. 2011). Thus, with actively applied management to the applicable forest systems, a sustainable approach to harvesting can be achieved.
Morchella conica Dill. ex Pers
Common names: yangdujun (Chinese), morel, sponge mushroom (English)
True morels (Morchella spp.), belonging to ascomycetous fungi, are highly prized for their edibility and appearance. Due to their unique flavor and rich nutritional value they have long being used as a food source. Morchella is also well known for its medicinal value, acting as immunostimulants and antitumor agents (Kanwal et al. 2010). Morels occur in different types of forests, with different mycelial dynamics, alternating between saprotrophic and symbiotic behaviors (Kanwal et al. 2010). There is some debate on how many Morchella species are there, with some estimates as long as 3–6 species and others as many as 50 different species (Stefani et al. 2010). In China morel mushrooms include M. esculenta, M. crassipes, M. spongiola, M. conica and M. elata (Zhao et al. 2010a). M. conica (Fig. 4) is the most marketable and widely distributed across China.
Habitat and distribution
Morels are found in a wide distribution range across the Northern Hemisphere, from North America, Canada, through Europe and into Asia. Furthermore, within China they are widely distributed, ranging from Beijing to Tibet (Mao 2000; Gui et al. 2002; Zhao et al. 2009), they are also found in Thailand and Laos and other parts of SE Asia.
Morels occur in a variety of habitats, including riverbanks, mountain slopes, pastures, and burnt forests. Linked with the numerous habitats is the fact that morels have no special requirement for soil type, occurring in sand, moist soil with abundant organic matter, and in mud (Goldway et al. 2000; Gui et al. 2002).
Two different types of environmental conditions are known to encourage Morchella ascocarp formation. Morels can first fructify as pioneers on recently disturbed soils. For example, they become visible in the first spring following mechanical disturbance of the soil, after application of certain herbicides, after a deposition of vegetative wastes, and after forest fires (Goldway et al. 2000; Zhao et al. 2010a). The second case is the production of ectomycorrhiza with higher plants. Morels are observed in association with trees in undisturbed habitats, where only a few ascocarps are produced each spring over a period of several years (Goldway et al. 2000).
In China, M. conica commonly grows at altitudes ranging from 2900–3100 m above sea level in several types of mixed forests, such as Picea likiangensis, Abies spp., Betula albo-sinensis, Sorbus sp., Salix sp., Acer sp., and Populus bonatii (Gui et al. 2002). Morels have two fruiting periods, from April to May, and from August to September after rain (Gui et al. 2002; Zhao et al. 2010a). Furthermore, morel fruit bodies require scattered light with an optimum temperature ranging between 6 and 11 °C and relative humidity ranging from 50 to 80 % (Gui et al. 2002; Zhao et al. 2010a).
Habitat zone 2
Over-harvesting of morels is a common problem across the morel production areas in Yunnan, China due to the fact that wild collection is unrestricted. Often forest fires are deliberately started in the spring to promote morel production for high harvest (Zhao et al. 2010a). The suggested harvesting management practices for morel should be as for that of Telephora ganbajun (He et al. 2011). Harvesting techniques include canopy pruning and removing the mushroom using a knife followed by watering the area around the mushroom upon harvesting (He et al. 2011).
After more than 100 years of trials, in 1982 the first indoor cultivation of morels was reported, with Morchella esculenta (Masaphy 2010). This was soon followed by other successful cases being published with regards to Morel bionic cultivation (Masaphy 2010; Cheng et al. 2009). In China there was some success in cultivating M. conica on timber from Populus bonatii (Cheng et al. 2009).
Ophiocordyceps sinensis (Berk.) G.H. Sung, J.M. Sung, Hywel-Jones & Spatafora (syn. Cordyceps sinensis)
Common names: Dong chong xia cao (Chinese); caterpillar fungus (English); yartsa gunbu (Tibetan)
The caterpillar fungus is among the most valuable mushroom species in the world, and plays a major role for the local economies on the Tibetan Plateau and adjacent regions (Fig. 5) (Winkler 2008). Indigenous peoples utilize this fungus for the treatment of different ailments, such as diarrhea, headache, coughing, rheumatism, liver disease, and it is also used as an aphrodisiac. Research has shown that Cordyceps usage increases both the cellular ATP levels (Namgyel and Tshitila 2003) and oxygen utilization by muscles (Zhu 2004) and has anticancer properties (Paterson 2008; Boonyanuphap 2011; De Silva et al. 2012).
The collection period starts at the end of April and runs into July. The tremendous increase in the price for O. sinensis in recent years turned this fungus into the most important cash income source in contemporary rural Tibet, making up 50–80 % of total household income in the areas where O. sinensis occurs (Winkler 2008). While it is possible to cultivate the mycelium of the fungus on artificial substrate, attempts to cultivate the fungus on infected caterpillars, which are perceived as most valuable and effective, have so far proven unsuccessful (Kim and Yun 2005).
Habitat and distribution
There are about 300–400 species of Cordyceps with a worldwide distribution (Kobayasi 1982; Sung 1996; Sung et al. 2007). About 68 species have been reported from China and 33 species have been recognized in the Tibetan Plateau and Himalayan region (Zang and Kinjo 1998). The caterpillar fungus is endemic to the Tibetan Plateau including the adjoining high altitude areas of the Central and Eastern Himalayas (Devkota 2009). In China, it is also known to occur in Sichuan, Yunnan, Qinghai, and Gansu provinces, which account for over 90 % production worldwide. It is usually found in the drier parts of the alpine region, where precipitation is below 300 mm per annum (Winkler 2008).
The fungus parasitizes the underground dwelling larvae of the ghost moth or swift moth. Hosts belong to the family Hepialidae (Chu et al. 2004), genus Thitarodes (mostly T. armoricanus), which live in the soil of grasslands and scrublands from an elevation of 3000 masl up to the snowline, however, the most common occurrence is between 3500 and 4500 masl. The fungus converts the caterpillar host into a sclerotium, from which the fruiting body of the fungus (Fig. 6) grows (Pegler et al. 1994; Wang 1995; Yao 2004). Wang and Yao (2011) identified 57 potential host species of O. sinensis distributed throughout the Tibetan Plateau. The potential habitat for hosts are the high elevation grasslands and alpine meadows, consisting predominantly of sedges (Kobresia spp.), which can cover up to 80–90 % of the subalpine grasslands (Wu 1997). Thitarodes moths prefer to feed on young roots of plant species of the families Polygonaceae, Fabaceae, Cyperaceae (including Kobresia), Poaceae, and Liliaceae (Chen et al. 2000).
Habitat zone 1
Several human practices are a major threat to the caterpillar fungus (Fig. 7). These include excessive livestock grazing; uncontrolled collection and trampling. Intentional burning with the purpose of getting fuel wood, obtaining better regeneration of O. sinensis and securing grass production for grazing in the following season is a major threat (Devkota 2006).
With the dramatic increase in value, there has been a sharp rise in demand for the caterpillar fungus, leading to unsustainable harvesting. Throughout its distribution range various management measures have been implemented (Weckerle 2010; Singh et al. 2010; Cannon et al. 2009; Devkota 2009). Examples of management measures implemented in China include the prohibition of tree cutting for fuel wood; prohibition of digging out living caterpillars; use of standardized digging tools; and an obligation to close up the digging holes. In addition, only trade with locally collected O. sinensis is allowed at the campsites and nature reserve staff inform collectors about market prices (Weckerle 2010)..
In India and Bhutan harvesting is controlled by local government, which issues letters of permission for local collectors, for a set price. Collectors are required to hand harvested materials to the government authority where they are sold to specific agencies (Singh et al. 2010; Cannon et al. 2009). For Nepal, management issues are related to habitat protection for O. sinensis and its hosts, aiming to protect pastures from over-grazing, and other kinds of human interference (Devkota 2009).
Phlebopus portentosus (Berk. & Broome) Boedijn
Common names: hed har, hed tub tao dum (Thai); tropical black bolete (English)
Phlebopus belongs to the family Boletinellaceae (suborder Sclerodermatineae of the Boletales) (Binder and Hibbett 2006) and this genus was originally described as a subgenus of Boletus by Heim (1936), and raised to generic status by Singer (1936). In 1944 Singer reclassified it as Phaeogyroporus braunii and this name was used until 1981 (Singer 1944, 1986). The taxon differs from other boletes as its hyphae produce clamp connections and this may be the reason why it can be grown in culture. Phlebopus portentosus is only eaten in southern China, Laos, northern Thailand and Myanmar, where it is considered a highly prized mushroom in local cuisines (Sanmee et al. 2010; Ji et al. 2011). The fungus is available from May through to September during the wet season, although occasional fruit bodies are produced after rains in November through to February.
Habitat and distribution
Phlebopus portentosus is known from northern Thailand (see Fig. 8), Laos and southern China (Sanmee et al. 2010; Ji et al. 2011) as well as Australia, New Zealand, Indonesia, Malaysia, Sri Lanka and Vietnam (Heinemann and Rammeloo 1982; Pegler 1986; Segedin 1987; Watling and Gregory 1988; Watling 2001; Bandala et al. 2004; Neves and Capelari 2007; Ji et al. 2009; Lei et al. 2009). In northern Thailand this mushroom grows in association with Artocarpus heterophyllus; Elaeocarpus hygrophilus, Syzygium cumini, Mangifera indica, Mimosa pigra, Salix tetrasperma, Coffea arabica, Citrus grandis and Dimocarpus longan (Bonmark et al. pers. comm.; Sanmee et al. 2010; Ji et al. 2011). It often grows in association with it hosts in mixed forests and orchards and is thought to be facultative mycorrhizal, although Ji et al. (2011) showed the fungus to be saprobic.
Habitat zone 4–5
Since the distribution and occurrence of Phlebopus is not well documented it is difficult to suggest ways to improve collecting management. However, Ji et al. (2011) state that the production of the mushroom has declined in Yunnan in recent years due to unrestricted commercial harvesting. Thus research is needed to establish the hosts with which it is associated, the forest types in which it occurs and the occurrence of fruiting bodies.
Evidence for the cultivation of Phloebopus is mixed, although it is clear that there is potential to produce inoculum for this fungus and thus inoculate host tree species with it (Sanmee et al. 2010; Ji et al. 2011). Sanmee et al. (2010) were also to produce low yields of basidiomes in culture and other groups are reportedly experimenting to increase yields (Thongklang et al. 2010; Ji et al. 2011). Furthermore, Kumla et al. (2012) have shown that this putatively ectomycorrhizal fungus has the ability to produce basidiomes without a host plant.
Pleurotus giganteus (Berk.) Karunarathna & K.D. Hyde
Common names: uru paha (Sri Lanka); judarensen, judaxianggu, dabeixianggu, daloudoujun, daloudougu (China); hed thoeng fon (Thai and Laos)
Pleurotus giganteus was originally described from Sri Lanka as Lentinus giganteus Berkeley (1847). It has been treated as a special food since ancient times and is mentioned in Buddhist literature (Udugama and Wickramaratna 1991; Berkeley 1847). When mature, the basidiome is typically infundibuliform measuring up to 35 cm in diameter and 28 cm high (Udugama and Wickramaratna 1991; Berkeley 1847). The mushroom may be solitary but often forms in groups on the ground (Fig. 1). This species has a thick, radicant stipe (Fig. 2) and subdistant broad lamellae which is typical of Lentinus (Pegler 1983). However, Pleurotus giganteus possesses many structures which are not characteristic of the genus Lentinus, and hence its taxonomic placement remains uncertain (Pegler 1983).
Habitat and distribution
Pleurotus giganteus is a saprobe, one of the largest edible mushrooms which grows on the ground, is mostly solitary, but can be found in groups, rooting often around stumps, from buried wood, dead roots, in the open and in lowland and mountain forest up to 3000 masl. It is mostly associated with Artocarpus heterophyllus but it can also be found in mixed vegetation (see Fig. 9) (Pegler 1983; Berkeley 1847; Udugama and Wickramaratna 1991). This species has been recorded in Australia, the Malay Peninsula, Sabah, Sri Lanka, Vietnam (Pegler 1983), Oceania (Zhishu et al. 1997), China (Yang and Zang 2003; Zhishu et al. 1997), and Thailand (Karunarathna et al. 2011a). It is a local delicacy in China, Taiwan, Thailand, Sri Lanka and Laos (Peng 2006; Udugama and Wickramaratna 1991; Karunarathna et al. 2011b; Chandrasrikul 2011; Tapingkae 2005).
Habitat zone 3–4
P. giganteus was successfully domesticated in the 1980’s, however it has only been cultivated commercially in china in recent years (Chen and Hu 2002; Huang 2005; Peng 2006). Despite the popularity of this mushroom in China it is not yet commercially cultivated in Thailand, Laos or Sri Lanka (Udugama and Wickramaratna 1991; Karunarathna et al. 2011b). There are no major threats to P. giganteus as this species is saprobic and can grow in mixed forest habitats (see Fig. 10).
Termitomyces eurhizus (Berk.) R. Heim
Common names: jizong, zhen gen yichaosan (China), Jirousigu (Taiwan), Baijigu (Japan)
Termitomyces eurhizus, also known as T. albuminosus, was first recorded in the Compendium of Material Medical (Ben Cao Gang Mu) 400 years ago in China (Tan and Miao 2009). It is a species of basidiomycetes fungi belonging to Tricholomataceae.
The color of pileus surface is usually grey with a diameter ranging from 5 to 20 cm (Fig. 11). There is usually no ring around the stipe (Shao-Yu 2006). T. eurhizus is renowned for its taste and high nutritional value, with a high protein, polysaccharide, and amino acid content (Chandra and Purkayastha 1977; Mondal et al. 2004). Past studies have shown that it has anti-oxidant and anti-tumor activities (Lin 2005). Due to its nutritional and medicinal properties T. eurhizus is a sought after mushroom species. To date, no cultivation has been possible due to its mycorrhizal nature (Wang et al. 2005; Lu et al. 2007; Sun 2006; Wang and Du 2005).
Habitat and distribution
Termitomyces eurhizus is known to grow in broad-leaved forests of tropical Africa and Asia (Mondal et al. 2004). In China, it is located in tropical and subtropical areas of Yunnan and Sichuan provinces (Kone et al. 2011). T. eurhizus is a symbiotic fungus, growing in association with termites of the subfamily Macrotermitinae and their nests. Fruiting bodies of T. eurhizus usually occur after rain or in high humility areas, and the fruit body matures rapidly (Shao-Yu 2006). The habitat of T. eurhizus is very diverse, ranging from low moisture forests in India to the humid and moist subtopic oceanic regions of China. The vegetation and soil type also varies greatly, most likely due to the wide range of habitats suitable for the termites (Batra 1979; Wei and Yao 2003).
Habitat zone 2–6
T. eurhizus has not been domestically cultured, so its management and conservation focuses on the preservation of natural habitats at present. Furthermore, it is difficult to advise on reforestation species as this mushroom is reliant on termite mounds and not just vegetative cover for production.
Currently several projects are attempting to cultivate T. eurhizus in China. Firstly via the use of wood decomposition to generate the fungal bodies and secondly by encouraging the production of termite mounds to house the fungal colonies, both approaches have yet to yield commercially viable production values (Chang and Miles 2004; Shao-Yu 2006; Yujin et al. 2010).
Thelephora ganbajun M. Zang
Common names: gangbajun, songmajun and xiuqiujun (China)
Habitat and distribution
Thelephora ganbajun is endemic to Yunnan Province, China, and grows primarily in association with pine forests, at altitudes between 800 and 2200 masl (Gui et al. 2005; He et al. 2010). Vegetation cover associated with the occurrence of T. ganbajun include pure stands of Pinus yunannensis and P. kesiya, and to a lesser extent Keteleeria evelyniana and Cunninghamia lanceolata as well as mixed broad leaf/conifer forests (Gui et al. 2005). This species is not commercially cultivated and hence only wild harvesting takes place. Thelephoras grow in Laos and Thailand but no reports are available regarding T. ganbajun. However Thelephora species are not generally eaten in these countries, which may indicate an unutilized opportunity for local people.
Habitat zone 3–4
The landscape of Yunnan Province has to a large extent, been altered by human influence, primarily due to agriculture, resulting in habitat loss for T. ganbajun. However, with new measures being taken in reforestation, new habitats for T. ganbajun are being created, though this is a lengthy process as T. ganbajun requires forest stands 10 years or older. Furthermore, many of the new trees being planted for reforestation are not species which host T. ganbajun on their roots, but rather trees of economic value.
Due to the fact that wild harvesting is the only option, certain management techniques have been suggested to improve production and allow for a more sustainable approach to wild harvesting (He et al. 2011). Harvesting techniques include canopy pruning and removing the mushroom using a knife followed by watering the area around the mushroom upon harvesting (He et al. 2011). In addition to harvesting techniques, management of the land users themselves was initiated; this included training in the correct harvesting techniques; ownership/harvesting rights being granted to user groups for a given area; and controlling the number and size of harvests per season (He et al. 2011). T. ganbajun is an economically important species for the region, with an annual harvest of 10 000 tonnes for Yunnan province, and can account for up to 37 % of household incomes in areas of high mushroom density (He et al. 2011; Zhao et al. 2009).
Tricholoma matsuake (S. Ito & S. Imai) Singer
Common names: matsu-take (Japanese), pine mushroom (English), songrong (Chinese)
Matsu-take literally means “pine mushroom” in Japanese; the equivalent Chinese name is songrong indicating the association of this mushroom with pine trees. It includes a group of edible species from the genus Tricholoma. They occur in Asia (with T. matsuake as principal species), North America (with T. magnivelare as principal species), Europe and North Africa (with T. caligatum as principal species) (Wang et al. 1997). Matsutake mushrooms are soil-borne and perennial mycorrhizal fungi. Favored by the Japanese as a delicacy, matsutake is one of the most expensive mushrooms in the world. Depending upon the quality, the wholesale price in Japan varies from US$ 27–560 per kilogram (Wang et al. 1997). On average, the total consumption in Japan is 3000 tonnes per year, of which one third comes from Yunnan Province, China, and rest from other parts of China and America, Europe, Japan and Korea. Export of matsutake from Yunnan to Japan increased from 20 t in 1985 to 1420 tonnes in 2005 (Menzies and Li 2010) with annual proximal value of US$ 44 million (Yang et al. 2008).
Habitat and distribution
In China, five species (and one variety) of Tricholoma are found in at least eight provinces (Liu et al. 1999), of which T. matsutake is the most valuable and intensively exploited. Tricholoma species are also distributed in China, Japan, Korea, and Russia (Amaranthus et al. 1996). In China, T. matsutake is listed as a protected species (Yang et al. 2006b). As a mycorrhizal fungus, the distribution and habitat of matsutake is highly dependent on host tree species. T. matsutake mainly grow under pine (Pinus) and oak (Quercus) forests, and occasionally under Picea and Castanopsis (Figs. 14 and 15) (Wang et al. 1997). Apart from host trees, forest structure (including canopy cover, stand age and stand vitality), understory coverage, litter cover, soil and topographic characteristics are important habitat factors (Amaranthus et al. 1998; Hosford et al. 1997; Yang et al. 2006b). In general, middle-aged host trees, slightly opened canopies, sparse understory coverage and moderate litter cover are good for fruiting.
Habitat zone 5–6
In Yunnan Province, China, forests producing T. matsutake generally range from 30 to 60 years, thus requiring mature stands of forest for production (Chen et al. 2011). Japanese researchers have focused on matsutake cultivation for more than a century, yet no successful method has been reported. The resource supply depends only on the natural system. A dramatic productivity decline occurred in Japan since the mid-twentieth century due to pinewood nematode blight outbreak of pine forests and forest structure and composition alteration due to shifting of management away from traditional practices (Wang et al. 1997; Hosford et al. 1997). In Japan, practices to modify the forest canopy structure, forest floor and soil drainage condition were used to enhance production. In China, governance policy and regulations were implemented at multiple levels (Menzies and Li 2010) and local communities crafted different strategies on managing resource use conflict and balancing equity needs (Yang et al. 2006a).
Tuber indicum Cooke & Massee
Common names: truffle (English), truffe (French), yidukuaijun (Chinese)
Habitat and distribution
There are more than 60 truffle species reported worldwide (Trappe 1979), with most being distributed in Spain, France and Italy (Wang et al. 2005). The natural habitat spans from the Northern to the Southern Hemisphere (Weden et al. 2004; Trappe et al. 2009; Bonito et al. 2011). In China, 35 truffle species have been described (Ren et al. 2005), and most of them have high economic value. Tuber indicum is one of the renowned commercial truffles in Yunnan Province, China and it has been exported to Japan, United States, Europe and Australia since the 1980’s (Tao and Liu 1990; Hall et al. 1998a, b; Chen et al. 2009). Chinese truffle host trees mainly belong to Betulaceae, Fagaceae, and Pinaceae. These ectomycorrhizal fungi occur in calcareous to non-calcareous soils at around 1200–3200 masl. Usually, the fruiting season lasts from August to November (García-Montero et al. 2010).
Habitat zone 3–5
The Chinese truffle species (see Fig. 16) are always associated with 10–40 years old secondary-growth coniferous forests, which develop from evergreen board-leaved forests (García-Montero et al. 2010). The most productive host trees are 10–20 years old (Zhang and Wang 1990). An another interesting phenomenon emerges from the allelopathic behaviour of truffle species, limiting the growth of surrounding vegetation with the aid of volatile organic compounds produced from truffle fruit bodies, mycelia and ectomycorrhizal roots (Zappa et al. 2004; Tarkka and Piechulla 2007). This is indicated from the appearance of a “burnt area” or brulé around the host species. Recent studies found that the brulé may also effect the dynamics of other ectomycorrhizal fungal populations (Napoli et al. 2009). Potential habitat maps were constructed for T. indicum using the weight of evidence method (Yang et al. 2012).
Cultivation and management
The first truffle plantations were established in Italy and then in France (Chevalier and Grente 1979), later introduced to New Zealand, United States and Hungary. In China, it is reported that the first plantation was planted in Taiwan in 1989 (Hu et al. 2005). The main cultivation method still depends on inoculating host tree seedlings with truffle spores, and then growing them in their natural environment (Samils et al. 2008; Bonito et al. 2011). The fruit bodies of truffle can be collected after about 5–8 years.
Wild edible mushrooms are one of the higher valued non-timber forest products in northern Thailand (Sysouphanthong et al. 2010; Karunarathna et al. 2011a), Laos, China, and most Asian countries (Boa 2007). They offer local people a source of seasonal food, medicine, and an alternative income, while maintaining forest health (Sysouphanthong et al. 2010). The abundance of wild mushrooms is also a bioindicator of ecosystem health (Dai et al. 2009; Du et al. 2011a, b; Sysouphanthong et al. 2010; Egli 2011). In Thailand and Laos, wild mushrooms are taxonomically poorly known and recent studies focusing on specific genera have resulted in a large number of new species (Zhao et al. 2008, 2010b, 2011a, b; Le et al. 2007a, b; Sanmee et al. 2008; Kerekes and Desjardin 2009; Wannathes et al. 2009a, b; Van de Putte et al. 2010; Karunarathna et al. 2011a, b), indicating how little we actually know about the organisms and the role they play. Even in Yunnan Province of China, relatively little is known, as apparent in recent publications (Ge et al. 2010; Zhang et al. 2010; Li et al. 2011; Yang 2011). There is a need to preserve these landscapes, before as yet unknown mushroom species and their related benefits are lost.
There has been a steady decline in mushroom productivity and the disappearance of certain species of mushrooms is an ongoing issue for much of the Greater Mekong Subregion (Arnolds 1995). The primary reasons for these issues are habitat loss and the impact of increased commercial picking and overharvesting (see Fig. 17) (Perini 1998). Mushroom collecting in developing countries frequently provides cash income to supplement a subsistence lifestyle, and edible fungi represent an important food resource. Controlling mushroom collection is not an easy task, and there are widely differing rules and policies on the collection of wild edible mushrooms in different countries (FAO 1995; Boa 2007). Overharvesting is a frequently expressed concern, both for economic and subsistence purposes (Hens and Boon 2003; Boa 2007; Amaranthus and Pilz 1996; Molina et al. 1997).
Even though the main focus of this paper is to address popular highly prized Asian edible mushrooms in terms of value, ecology, conservation, and sustainable management, it is worth noting how the introduction of regulations serves to protect wild mushrooms in different ways. The few case studies present, such as that of He et al. (2011), should lead the way in management guidelines for sustainable harvesting.
A high diversity of wild mushrooms is a vital requirement for a healthy forest ecosystem (Boa 2007), and a healthy forest is necessary to maintain a high diversity and productivity of wild mushrooms (Boa 2007; Moore and Chiu 2001; Pilz and Molina 1996).
We acknowledge and thank CGIAR Research Program 6 on Forests, Trees and Agroforestry-Mekong Sentinel Landscapes for funding this project. Also, value added products from basidiomycetes: Putting Thailand’s biodiversity to use (BRN049/2553), the French-Thai cooperation PHC SIAM 2011 (project 25587RA), the National Research Council of Thailand (NRCT), the project—Taxonomy, Phylogeny and cultivation of Lentinus species in northern Thailand (NRCT/55201020007), Thailand Research Fund (TRF) project number BRG5580009 and Mae Fah Luang University, the project—Taxonomy, Phylogeny and cultivation of Lentinus species in northern Thailand (MFU/54 1 01 02 00 48) are thanked for providing support to this study.