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Differences in the growth and ectomycorrhizal community of Dryobalanops lanceolata (Dipterocarpaceae) seedlings grown in ultramafic and non-ultramafic soils
Abstract
Ultramafic soils have naturally high concentrations of metals and are often low in major plant nutrients. Plant species of non-ultramafic origin, such as Dryobalanops lanceolata (Dipterocarpaceae), generally grow less well on these soils. I found minimal changes in growth, but a 17% reduction in foliar potassium, when seedlings of D. lanceolata were grown in a non-native ultramafic soil when compared with a ‘normal’ tropical ultisol. There were, however, marked changes in the ectomycorrhizal community structure on the roots of D. lanceolata. Cenococcum geophilum was at least 10 times more common and Inocybe sp. was one and a half times more common in non-ultramafic soils, whereas Boletales sp. was over 30 times more common in the non-ultramafic soil. These changes may have been brought about by a number of edaphic differences between the two soil types, including high metal concentrations and differences in organic matter content.
... For dipterocarps, positive correlations were found between ECM formation and seedling growth (Lee & Lim 1989, Sangwanit & Sangthian 1991. In several dipterocarp species, ECM fungal inoculation was found to improve phosphorus uptake and seedling growth (Brearley 2006, Lee et al. 2008, Turjaman et al. 2011. Thus, ECM fungi can be beneficial in dipterocarp plantations. ...
... The positive significant correlation between ECM formation and seedling growth suggested that the ECM formation on roots of D. alatus could enhance the growth of dipterocarp seedlings under the pot culture condition. Many studies also reported growth enhancement of dipterocarp seedlings by ECM fungi (Turjaman et al. 2005, Brearley 2006, Ogawa 2006, Lee et al. 2008, Turjaman et al. 2011. This is the first study to demonstrate the growth enhancement of dipterocarp seedlings by Astraeus species. ...
Astraeus odoratus is an edible
ectomycorrhizal (ECM) fungus found in natural dipterocarp forests. The effcacy of two different
inoculum types of this fungus, namely, spore suspension and cultured mycelium in inducing ECM
formation on pot-cultured seedlings of Dipterocarpus alatus was studied. Both types of inocula increased
ECM formation. A positive correlation was found between the ECM rate and seedling growth. Both
inoculation methods could be used to produce ECM seedlings of D. alatus.
... Subsequent eco-physiological work examined how EcM communities were affected by biotic and abiotic perturbations , 2007, Brearley 2006 and examined the role of EcMs in organic nitrogen acquisition ). The first molecular study of dipterocarp EcM communities appeared in 2003 (Sirikantaramas et al. 2003), and since then there have been a few more (Moyersoen 2006, Yuwa-Amornpitak et al. 2006, Tedersoo et al. 2007a, Peay et al. 2010) although until the comprehensive study by Peay et al. (2010) these had mostly focused on rare or outlying members of the Dipterocarpaceae. ...
... RESPONSES TO SOIL TYPES.-The EcM community on the roots of nursery-grown Dryobalanops lanceolata is considerably different when seedlings are grown on ultramafic (with high levels of metals such as Fe, Mg, Ni, Co, and Cr) as compared to a more typical non-ultramafic ultisol soil (Brearley 2006), notably in that Cenococcum geophilum and Inocybe spp. decreased and Boletales sp. ...
Dipterocarps are one of the most important tree families in the lowland forests of Southeast Asia and are somewhat unusual among tropical trees in that they form ectomycorrhizal (EcM) symbiotic root-inhabiting fungal associations. It has been hypothesized that dipterocarps have been partnered in this mutualistic association prior to the separation of Gondwana. Under many conditions EcMs form rapidly on dipterocarp seedlings through inocula present in the soil, although few studies have been conducted to provide evidence that they improve seedling establishment and performance. There are hundreds of EcM species associated with dipterocarps. Fungal fruit body surveys suggest that the most important families are Amanitaceae, Boletaceae, and Russulaceae, although Thelephoraceae also become numerically important when root tips are examined. EcM communities are affected by various biotic and abiotic factors, as well as anthropogenic perturbations, and the importance of these in structuring EcM communities is examined herein.
... Since then reforestation programs in Thailand with dipterocarps species have been attempted and resulted in a total of approximately 2,080 ha (Boontawee 2001). Members of the Dipterocarpaceae form symbiotic root-inhabiting fungal associations with hundreds of ectomycorrhizal (ECM) fungal species (Watling and Lee 1995, 1998, 2003Brearley et al. 2003, 2006, 2011, 2012. Such reports B I O D I V E R S I T A S 21 (1): 231-238, January 2020 232 fail to indicate that members of the genus Astraeus are frequent, hypogeous associates. ...
Suwannasai N, Dokmai P, Yamada A, Watling R, Phosri C. 2020. First ectomycorrhizal syntheses between Astraeus sirindhorniae and Dipterocarpus alatus (Dipterocarpaceae), pure culture characteristics, and molecular detection. Biodiversitas 21: 231-238. This study provides the first mycorrhization of Astraeus sirindhorniae and its cultural characteristics on nutrient media. An attempt has been made to introduce spore suspension and mycelial inocula of A. sirindhorniae onto seedlings of Dipterocarpus alatus. After 6 months seedlings were harvested, measured for growth and morphological descriptions of the ectomycorrhizas formed with D. alatus seedlings were made. The fungus has increased the growth of D. alatus seedlings. Further, it can be confirmed that the primers designed (GAPK126F/GAPK379R) have been successful when applied for the detection of ectomycorrhizal formation of A. sirindhorniae in vivo.
... Several nursery experiments have shown that the ECM fungi, such as Anisoptera thurifera, can improve the growth and nutrient uptake of dipterocarp seedlings (Aggangan et al., 2012), Dipterocarpus spp. (Kaewgrajang et al., 2013;Kaewgrajang et al., 2014;Tapwal et al., 2016), Dryobalanops lanceolata (Brearley, 2006), Hopea odoratus (Lee et al., 2008), and Shorea spp. (Turjaman et al., 2005;Turjaman et al., 2006;Turjaman et al., 2011;Lee et al., 2008). ...
In this study, we investigated the effects of the highly prized ectomycorrhizal (ECM) mushroom, Astraeus odoratus, on the growth of Dipterocarpus tuberculatus Roxb. and Shorea roxburghii G. Don seedlings. The two seedling species were inoculated using two methods: 1) spore suspension of 25 mL/seedling; and 2) hyphal suspension of 25 mL/seedling. On harvesting, it was found that 30-60% of the roots formed by the inoculated seedlings were ectomycorrhizal roots. Seedling development was influenced by the inoculation method and the host plant species. A higher growth response was observed in the S. roxburghii seedlings inoculated with A. odoratus compared to D. tuberculatus seedlings. Moreover, the non-inoculated S. roxburghii seedlings had a lower growth response than D. tuberculatus seedlings, but their growth response was significantly higher than D. tuberculatus seedlings inoculated with a spore or hyphal suspension of A. odoratus. However, there was no difference between the effects of the spore and hyphal suspension treatments. Therefore, both the inoculation methods can be used to enhance the growth of seedlings, especially that of S. roxburghii.
... Several ecological factors may also play a role in the diversity of a certain area. This could be affected by the presence of microorganisms like bacteria and some species of fungi (Brearley 1999). The absence of a fungus in association with plants roots somewhat contributes to the low diversity in areas with high concentrations of heavy metal such as nickel. ...
The study was conducted to determine the status of floral diversity and screen plant species that has the potential to accumulate nickel in the nickel-rich Kinalablaban Delta located in Claver, Surigao del Norte. Fifty-nine (59) species of plants belonging to thirty-seven (37) families were found. The most represented families were Poaceae, Moraceae, and Fabaceae. These were families generally encountered anywhere and can be found in areas undergoing ecological succession. Notable species observed were Imperata cylindrica and Saccharum spontaneum in which these species were widely distributed all throughout the delta. Rhizophora sp. was also found since they are intentionally planted by the adjacent mining firm as part their environmental protection and management plan. The diversity, dominance and evenness were low indicating a need to enhance the vegetation in the delta. Out of the 59 species identified, only four species tested positive as potential nickel hyperaccumulator including Ardisia elliptica, Premna odorata, Phyllantus securinegoides and Phyllantus sp. These plant species however, must be tested further if it is indeed a nickel hyperaccumulator.
... A number of the seedlings were raised in a nursery before being transplanted into the forest and, based on prior observations (Brearley 2003), we are confident that they were all colonised by EcM fungi, albeit those more common of nursery conditions (e.g. Brearley et al. 2003Brearley et al. , 2007bBrearley 2006;Saner et al. 2011). Whilst "priority effects" of EcM colonisation have often been found to affect subsequent competitive replacement by other EcM species (Kennedy et al. 2009), replacement of nursery EcMs with those present in forest soil has been seen within 6 months for studies in Peninsular Malaysia (Chang et al. , 1995 and, given that the length of all our studies was at least 11 months, we do not consider this to have affected our results. ...
Background: Connections between mature trees and seedlings via ectomycorrhizal (EcM) hyphal networks existing in dipterocarp-dominated tropical rain forests of South-east Asia could have strong implications for seedling growth and survival and the maintenance of high diversity in such forests.
Aim: To test whether EcM hyphal network connections are important for the growth and survival of dipterocarp seedlings. Methods: We conducted four independent experiments that prevented contact of experimental seedlings with an EcM network by using a series of fine meshes and/or plastic barriers. We measured the growth and survival (and foliar δ13C in one experiment) of seedlings of six dipterocarp species over intervals ranging from 11 to 29 months.
Results: Seedling growth (diameter, height or leaf number) was unaffected by exclusion from the EcM network in three experiments and there were no differences in foliar δ13C values in the fourth. Seedling survival was reduced following exclusion from the EcM network in one experiment. Our results give little support to the hypothesis that dipterocarp seedlings growing in the shaded forest understorey benefit from being connected, through a common EcM network, to surrounding trees.
Conclusions: We suggest that our negative results, in contrast to studies conducted in low diversity boreo-temperate or tropical forests, are due to these high diversity forests lacking host species-specific EcM fungi and therefore providing little opportunity for adaptive support of seedlings via hyphal networks.
Keywords: Borneo; dipterocarps; ectomycorrhizas; mycorrhizal networks; source-sink relationships
... Hutan alam yang telah dikonversi menjadi hutan tanaman atau bentuk konversi lain kondisinya akan menjadi tidak sesuai bagi banyak jenis jamur ektomikoriza, terutama karena perubahan iklim mikro di bawah tajuk dan inang yang tidak sesuai. Tumbuhan dengan asosiasi ektomikoriza mendominasi ekosistem hutan alam tropis campuran, sehingga tubuh buah jamur ektomikoriza dapat ditemukan di banyak jenis tanah (Brearley, 2006;Smits, 1992). Menurut Mardji, Matius, dan Budiyanto (2013), sedikitnya ada 60 jenis jamur ektomikoriza di wilayah Kalimantan Timur (Bukit Soeharto, Wanariset Samboja dan areal ITCI) yang sebagian hutannya berupa hutan sekunder yang didominasi jenis-jenis dipterokarpa berukuran besar. ...
Kawasan Hutan Dengan Tujuan Khusus (KHDTK) Labanan merupakan miniatur hutan hujan tropis dataran rendah dengan keanekaragaman biodiversitas yang sangat tinggi dan memiliki potensi mikoriza yang tinggi tetapi belum banyak diketahui. Penelitian ini bertujuan untuk mengetahui keanekaragaman jenis jamur ektomikoriza dan potensinya, baik yang bersimbiosis mutualismetis dengan inang kelompok jenis Dipterocarpaceae maupun Non Dipterocarpaceae di hutan alam KHDTK Labanan, Berau, Kalimantan Timur. Metode penelitian yang digunakan adalah mengidentifikasi karakteristik jamur ektomikoriza yang masih segar di lapangan, pengambilan foto secara langsung dan identifikasi lanjutan menggunakan beberapa literatur bergambar sebagai pembanding. Hasil yang diperoleh adalah jumlah jenis jamur ektomikoriza di KHDTK Labanan ditemukan sebanyak 31 jenis yang terdiri atas 15 marga, sedangkan 13 suku memiliki jumlah jenis yang sama. Suku yang memiliki jumlah jenis paling banyak adalah Russulaceae (7 jenis) dan suku yang memiliki jumlah jenis paling sedikit adalah Hydnaceae, Strophariaceae, Boletaceae, Marasmiaceae, Gomphaceae dan Agaricaceae masing-masing 1 jenis. Ada 22 jenis jamur ektomikoriza (79,22%) bersimbiosis dengan inang kelompok jenis Dipterocarpaceae dan 9 jenis (20,78%) bersimbiosis dengan inang kelompok jenis Non Dipterocarpaceae.
... Serpentinit mempunyai formula am Mg 3 Si 2 O 5 (OH) 4, di mana ia merupakan unsur penting bagi batuan ultrabes yang terluluhawa. Pada amnya, Serpentinit mengandungi Ni, Cr, Co, Mg dan Fe pada kepekatan yang tinggi sementara kepekatan makronutrien tumbuhan seperti K, N, P dan Ca adalah rendah (Brooks et al. 1988;Brearley 2006). Kehadiran Fe pada kepekatan yang tinggi memberikan warna perang kemerahan kepada tanih ultrabes (Trescase et al. 1981). ...
This study was carried out at an ultrabasic area, Selaru and Felda Rokan Barat, Kuala Pilah, Negeri Sembilan. Eighteen samples of plant and its substrates were collected for determination of heavy metal contents such as Ni, Co, Cr, Mn and Fe in soils and plants. The plants were separated into three different portions i. e. root, stem and leaf and extracted for their heavy metal content by wet digestion method whereas the soil's heavy metal available and total content were extracted by sequential extraction. Heavy metals content in soil and plant extract was determined using Flame Atomic Absorption Spectrophotometer The result showed that total content of heavy metals for Ni, Cr, Co, Mn and Fe was at 84.13-740.36 mg/kg, 23.51-135.53 mg/kg, 188.23-848.92 mg/kg, 245.00-545.33 mg/kg and 1176.77-1243.90 mg/kg, respectively. Bio-available heavy metals content in soil is at 0.09-6.32 mg/kg for Ni, 0-0.51 mg/kg for Co, 0 mg/kg for Cr, 7.78-21.07 mg/kg for Mn and 2.23-4.47 mg/kg for Fe. Based on BAC, Mn and Fe were detected to have a high concentration in plant parts compared to other heavy metals.
... mengandungi Co, Cr, Fe, Mg dan Ni pada kepekatan yang tinggi manakala kepekatan makronutrien tumbuhan iaitu Ca, K, N dan P adalah rendah (Brearley 2006;Brooks et al. 1988). ...
A study was carried out at an ultrabasic soil area in Felda Rokan Barat (FRB), Negeri Sembilan. Twenty plants of samples namely chili, turmeric, pandan and lemon grass were collected randomly for the determination of heavy metal contents such as Fe, Cd, Co, Cu, Mn, Ni, Pb, Cr and Zn. Heavy metals in plants were extracted by wet digestion method, whereas available and resistant heavy metals in soil were extracted by sequential extraction. Total heavy metals content in the soil were obtained by summation of resistant and available heavy metals. Heavy metals content in soil and plant extract were determined by using the Flame Atomic Absorption Spectrophotometer (FAAS). Results showed that Fe was the dominant composition in soil in the study area while Cd concentration was very low with values of < 10 mg/kg. The range of heavy metals concentration in soils were Fe (2618.4 to 4248 mg/kg), Mn (240.9 to 741.9 mg/kg), Zn (81.9 to 324.8 mg/kg), Cr (46.8 to 438.7 mg/kg), Cu (15.7 to 81.7 mg/kg), Pb (14.9 to 116.8 mg/kg), Ni (10.1 to 545.6 mg/kg), Cd (5.6 to 10.6 mg/kg) dan Co (0.8 to 126.1 mg/kg). Available Fe recorded the highest value in all of the plant substrates followed by Mn, Zn, Pb, Ni, Cr, Cu, Co and Cd. Based on percentage of availability Mn, Pb and Zn are considered most available by plant with availability percentage of 8 to 10%. Concentration of Fe, Mn, Ni and Zn were high in all parts of plants compared to the other metals. The value of biological absorption coefficient (BAC) in chili, turmeric, pandan and lemon grass were in the range of 0.02-0.36, 0.03-0.41, 0.03-0.63 and 0.03-1.15, respectively. It can be concluded that the uptake of heavy metals by plants were normal even though the heavy metals concentration in the ultrabasic soil was high.
... In addition, it was recently demonstrated that ultramafic soils do not limit and can even promote ectomycorrhizal fungal diversity (Moser et al., 2009;Branco and Ree, 2010). Comparisons of ECM fungal diversity between ultramafic and nonultramafic soils showed differences within the fungal population structure (Brearley, 2006), sometimes with the presence of unique species (Moser et al., 2005). The study of physiological behaviours such as metal tolerance within the same fungal species present on both ultramafic and non-ultramafic soils have suggested adaptive evolution, raising questions about the adaptation and evolution of fungal species on these soils (Gonç alves et al., 2007(Gonç alves et al., , 2009Jourand et al., 2010a,b). ...
... In nursery conditions, Ingleby et al. (2000) reported that Thelephoraceae species were common on seedlings grown with soil from Vietnamese forests. Brearley et al. (2003Brearley et al. ( , 2007b and Brearley (2006) also found that two Thelephoraceae species were common in nursery-grown dipterocarp seedlings in Malaysia. ...
We attempted to introduce ectomycorrhizal (ECM) fungi onto seedlings of Dipterocarpus alatus (Dipterocarpaceae) by soil inocula collected from tree stands of D. alatus. Top soils collected from beneath the trees of D. alatus in a dry evergreen forest and a 15-year-old plantation were inoculated onto germinating seeds of D. alatus. After 7 months of seedling cultivation, ECM fungal communities in the seedlings were investigated based on the sequences of ITS rDNA. The ECM fungi detected were divided into 19 phylotypes by molecular analysis. Most of the phylotypes were identified as ECM fungal taxa, i.e., Clavulina, Laccaria, Lactarius, Tomentella, Pyronemataceae, and Tricholomataceae. Accordingly, we can confirm that soil inoculation is a simple method to induce ECM formation with diverse fungi in pot cultured seedlings, which would be useful for introducing diverse ECM fungi to dipterocarp plantations.
... Serpentinit mempunyai formula am Mg 3 Si 2 O 5 (OH) 4, di mana ia merupakan unsur penting bagi batuan ultrabes yang terluluhawa. Pada amnya, Serpentinit mengandungi Ni, Cr, Co, Mg dan Fe pada kepekatan yang tinggi sementara kepekatan makronutrien tumbuhan seperti K, N, P dan Ca adalah rendah (Brooks et al. 1988;Brearley 2006). Kehadiran Fe pada kepekatan yang tinggi memberikan warna perang kemerahan kepada tanih ultrabes (Trescase et al. 1981). ...
ABSTRAK Kajian ini dijalankan di kawasan tanih ultrabes di Selaru dan Felda Rokan Barat, Kuala Pilah, Negeri Sembilan. Sebanyak lapan belas sampel tumbuhan dan substratnya telah diambil bagi menentukan kandungan logam berat Ni, Co, Cr, Mn dan Fe di dalam tanih dan tumbuhan. Tiga bahagian tumbuhan iaitu akar, batang dan daun telah dianalisis secara penghadaman basah manakala tanih pula telah dianalisis kandungan logam berat tersedia dan jumlah dengan kaedah pengekstrakan berjujukan. Kandungan logam berat di dalam larutan ekstrak tanih dan tumbuhan ditentukan menggunakan Spektrofotometer Serapan Atom Nyalaan. Hasil kajian menunjukkan kandungan jumlah logam berat Ni, Cr, Co, Mn and Fe dalam tanih masing-masing adalah 84.13-740.36 mg/kg bagi Ni, 23.51-135.53 mg/kg bagi Co, 188.23-848.92 mg/kg bagi Cr, 245.00-545.33 mg/kg bagi Co dan 1176.77-1243.90 mg/g bagi Fe. Kandungan kebiodapatan logam berat dalam tanih adalah 0.09-6.32 mg/kg bagi Ni, 0-0.51 mg/kg bagi Co, 0 mg/kg bagi Cr, 7.78-21.07 mg/kg bagi Mn dan 2.23-4.47 mg/kg bagi Fe. Berdasarkan BAC, Mn dan Fe adalah logam yang banyak dikesan di dalam bahagian tumbuhan berbanding dengan logam lain. Kata kunci: Logam berat; pengambilan tumbuhan; tanih ultrabes; terung pipit (Solanum torvum) ABSTRACT This study was carried out at an ultrabasic area, Selaru and Felda Rokan Barat, Kuala Pilah, Negeri Sembilan. Eighteen samples of plant and its substrates were collected for determination of heavy metal contents such as Ni, Co, Cr, Mn and Fe in soils and plants. The plants were separated into three different portions i.e. root, stem and leaf and extracted for their heavy metal content by wet digestion method whereas the soil's heavy metal available and total content were extracted by sequential extraction. Heavy metals content in soil and plant extract was determined using Flame Atomic Absorption Spectrophotometer. The result showed that total content of heavy metals for Ni, Cr, Co, Mn and Fe was at 84.13-740.36 mg/kg, 23.51-135.53 mg/kg, 188.23-848.92 mg/kg, 245.00-545.33 mg/kg and 1176.77-1243.90 mg/kg, respectively. Bio-available heavy metals content in soil is at 0.09-6.32 mg/kg for Ni, 0-0.51 mg/kg for Co, 0 mg/kg for Cr, 7.78-21.07 mg/kg for Mn and 2.23-4.47 mg/kg for Fe. Based on BAC, Mn and Fe were detected to have a high concentration in plant parts compared to other heavy metals. Keyword: Heavy metal; plant uptake; terung pipit (Solanum torvum); ultrabasic soil
... This pattern contrasts with many temperate zone forests where ECM fungal communities often exhibit marked spatial autocorrelation and the dominant ECM species can vary significantly in nearby stands of trees [7,50]. Furthermore, the importance of edaphic factors in shaping tropical ectomycorrhizal communities has been suggested by studies of paleotropical dipterocarps in Borneo [8,51]. ...
Ectomycorrhizal (ECM) plants and fungi can be diverse and abundant in certain tropical ecosystems. For example, the primarily paleotropical ECM plant family Dipterocarpaceae is one of the most speciose and ecologically important tree families in Southeast Asia. Pakaraimaea dipterocarpacea is one of two species of dipterocarp known from the Neotropics, and is also the only known member of the monotypic Dipterocarpaceae subfamily Pakaraimoideae. This Guiana Shield endemic is only known from the sandstone highlands of Guyana and Venezuela. Despite its unique phylogenetic position and unusual geographical distribution, the ECM fungal associations of P. dipterocarpacea are understudied throughout the tree's range. In December 2010 we sampled ECM fungi on roots of P. dipterocarpacea and the co-occurring ECM tree Dicymbe jenmanii (Fabaceae subfamily Caesalpinioideae) in the Upper Mazaruni River Basin of Guyana. Based on ITS rDNA sequencing we documented 52 ECM species from 11 independent fungal lineages. Due to the phylogenetic distance between the two host tree species, we hypothesized that P. dipterocarpacea would harbor unique ECM fungi not found on the roots of D. jenmanii. Although statistical tests suggested that several ECM fungal species did exhibit host preferences for either P. dipterocarpacea or D. jenmanii, most of the ECM fungi were multi-host generalists. We also detected several ECM fungi that have never been found in long-term studies of nearby rainforests dominated by other Dicymbe species. One particular mushroom-forming fungus appears to be unique and may represent a new ECM lineage of Agaricales that is endemic to the Neotropics.
... During the last decade, numerous studies have tried to unveil the role that natural factors, such as environmental conditions and host plant community composition, have on the assemblage of ECM communities (Conn and Dighton, 2000; Dickie and Reich, 2005; Buée et al., 2007). Soil abiotic conditions, namely, soil moisture, pH and nutrient availability, influence the performance and assemblage of fungal species (Brearley, 2006; Cavender-Bares et al., 2009). Host trees may directly affect the assemblage of their mycorrhizal community by exerting a selection for mycorrhizal species (Ishida et al., 2007; Tedersoo et al., 2008). ...
Host trees can modify their soil abiotic conditions through their leaf fall quality which in turn may influence the ectomycorrhizal (ECM) fungal community composition. We investigated this indirect interaction using a causal modelling approach. We identified ECM fungi on the roots of two coexisting oak species growing in two forests in southern Spain – Quercus suber (evergreen) and Quercus canariensis (winter deciduous)-using a PCR-based molecular method. We also analysed the leaf fall, litter and soil sampled beneath the tree canopies to determine the concentrations of key nutrients. The total mycorrhizal pool was comprised of 69 operational taxonomic units (OTUs). Tomentella and Russula were the most species-rich, frequent and abundant genera. ECM fungi with epigeous and resupinate fruiting bodies were found in 60% and 34% of the identified mycorrhizas, respectively. The calcium content of litter, which was significantly higher beneath the winter-deciduous oak species due to differences in leaf fall quality, was the most important variable for explaining ECM species distribution. The evaluation of alternative causal models by the d-sep method revealed that only those considering indirect leaf fall-mediated host effects statistically matched the observed covariation patterns between host, environment (litter, topsoil, subsoil) and fungal community variables.
... However, it is known that above-ground and below-ground views of the EcM community rarely show close concordance (Gardes and Bruns 1996;Yamada and Katsuya 2001), and it has recently been noted that fungi with cryptic fruiting bodies such as members of the Thelephoraceae, which appear to have been overlooked in fruiting body surveys, are also important EcM formers. For example, Ingleby et al. (2000) found a Thelephoraceae species to be common on seedlings planted in soil from Vietnamese forest and I have found two Thelephoraceae species common on nursery-grown seedlings in Malaysia (Brearley et al. , 2007Brearley 2006). Furthermore, sequences from this group dominated the molecular studies on dipterocarp EcM communities conducted by Sirikantaramas et al. (2003) and Yuwa-Amornpitak et al. (2006). ...
The Dipterocarpaceae, ecosystem dominants and source of forest products in South-east Asia, form ectomycorrhizas (EcMs). Important
fungal families involved in this symbiosis are Amanitaceae, Boletaceae, Pisolithaceae, Russulaceae, Sclerodermataceae and
Thelephoraceae. The presence of EcM fungi on the roots of dipterocarp seedlings has been shown to improve P nutrition most
notably but also N, Ca and Mg nutrition and to improve access to organic forms of N. In addition, EcMs have been shown to
improve seedling growth although mostly under nursery conditions. These results have led it to be suggested that seedlings
should be inoculated prior to being out-planted in reforestation programmes. Current and recent inoculation schemes have focussed
on the genera Pisolithus, Scleroderma and Tomentella. The most controlled method to inoculate seedlings is to apply a known amount of inoculum of an identified, aseptically cultured
EcM fungal species. In situations where this has not been feasible, tabletted EcM inoculum has been applied. The simplest
to inoculate seedlings is to use forest soil colonised with EcM hyphae, root fragments and spores; whilst this does not guarantee
the most beneficial fungus will be dominant on the roots of the seedlings it will allow EcM formation of some kind. Before
assuming that pre-inoculating seedlings will bring long-term benefits to seedlings planted in soils where EcM inoculum is
already present, a number of questions need to be asked. First, does inoculation actually improve growth and survival of out-planted
seedlings? If so, second, under what conditions and situations is inoculation of benefit? Finally, is colonised soil inoculum
just as good as single species inoculum? However, in soils lacking inoculum (such as burnt peat swamp forest and ex agricultural
land), inoculating seedlings is more likely to be of benefit to initial seedling growth and survival. Whilst EcMs have often
been shown to be beneficial for seedling performance, the warning raised over 40 years ago that “mycorrhizal infection should
not be taken as the ‘cure of all ills’ in the establishment of trees” still applies today.
... There is good evidence from field studies that soil environment affects ectomycorrhizal fungal community structure (Swaty et al., 1998; Toljander et al., 2006 ). Pot studies have also shown some differentiation of dipterocarp mycorrhizas based on particular soil types or nutrient sources (Brearley, 2006; Brearley et al., 2007 ). In relation to the plant community, while many ectomycorrhizal fungi are host generalists (Horton & Bruns, 1998; Kennedy et al., 2003), there is some evidence that host preferences or specificity can affect ectomycorrhizal fungal community structure (Ishida et al., 2007; Tedersoo et al., 2008). ...
*Relatively little is known about diversity or structure of tropical ectomycorrhizal communities or their roles in tropical ecosystem dynamics. In this study, we present one of the largest molecular studies to date of an ectomycorrhizal community in lowland dipterocarp rainforest. *We sampled roots from two 0.4 ha sites located across an ecotone within a 52 ha forest dynamics plot. Our plots contained > 500 tree species and > 40 species of ectomycorrhizal host plants. Fungi were identified by sequencing ribosomal RNA genes. *The community was dominated by the Russulales (30 species), Boletales (17), Agaricales (18), Thelephorales (13) and Cantharellales (12). Total species richness appeared comparable to molecular studies of temperate forests. Community structure changed across the ecotone, although it was not possible to separate the role of environmental factors vs host plant preferences. Phylogenetic analyses were consistent with a model of community assembly where habitat associations are influenced by evolutionary conservatism of functional traits within ectomycorrhizal lineages. *Because changes in the ectomycorrhizal fungal community parallel those of the tree community at this site, this study demonstrates the potential link between the distribution of tropical tree diversity and the distribution of tropical ectomycorrhizal diversity in relation to local-scale edaphic variation.
Ultramafic outcrops occupy less than 1% of the land surface of the Earth and are renowned as hotspots of plant diversity and endemism. With over 3500 km 2 of ultramafic outcrops in Sabah (4.6% of the total landmass of the state) on the island of Borneo and a total of 4252 plant species recorded occurring on this substrate, Malaysia has one of the most species-rich floras occupying these outcrops globally. Over 2542 plant species have been documented on ultramafic outcrops in Kinabalu Park alone, of which a large percentage is endemic to either Kinabalu Park or Borneo. Despite the existence of this species rich flora, the full plant diversity and ecology remains largely unknown because of a lack of focussed research. Furthermore, plant diversity in many areas of Sabah is severely threatened by land-use conversion and, because many plant species occur only in a single or a few ultramafic sites, impacts on the ecosystems that support them could eventually result in their extinction.
Interspecific interactions, such as competition, occur among members of ectomycorrhizal fungal communities and serve as structuring forces in the development and maintenance of such communities. Under a stable set of environmental conditions, competitive hierarchies (or, in the more general case, interaction hierarchies) become established, resulting in the expression of dominance hierarchies. However, interaction hierarchies are context-dependent; competitive rankings among species, for example, depend on environmental conditions. Context-dependency occurs because of species-specific tolerances to and preferences (traits) for environmental conditions. Therefore, dominance within communities shifts from one species to another as environmental conditions shift in time or space. Phenomena such as habitat partitioning and host specificity, as well as community responses to disturbance and shifts in community structure along environmental gradients, can be explained by the context-dependence of interaction hierarchies among ectomycorrhizal fungi. Understanding the context-dependence of interaction hierarchies in terms of the relationships between species traits and environmental heterogeneity can elucidate general principles involved in the structuring of biological communities.
This chapter focuses on the mutual relations between metal elements and the population biology, community composition and biodiversity of ectomycorrhizal fungi (ECMF) and on the contribution of ECMF to metal transfers in food webs. The ectomycorrhizal (ECM) association of trees and fungi is successful in recycling scarce essential metal elements and in colonizing soils with high levels of metal toxicity. Uptake and translocation of metal elements by ECMF may account for major deviations from simple models of soil metal budgets. Accumulation of certain essential and non-essential metals and metalloids (e.g. K, Rb, Cs, As, Se, Zn, Cd, Hg, Ag) is common in ECMF, while other elements tend to be excluded (e.g. Al, Pb). Bioconcentration factors (BCFs) are species, strain and metal specific. A negative correlation between environmental metal concentrations and BCFs appears to be the rule. The role of ECMF as a nutrient source of rare elements (e.g. Se) and as an important gateway of toxic metals to vertebrate foodwebs in polluted areas merits further study.
ECM communities in metalliferous soils can be surprisingly diverse. The potential to colonize metalliferous soils is widespread in various phylogenetic groups of ECMF. The microevolution of metal tolerance does not require populational differentiation.
Selection for metal-tolerant ecotypes of ectomycorrhizal (ECM) fungi has been reported in instances of metal contamination of soils as a result of human activities. However, no study has yet provided evidence that natural metalliferous soils, such as serpentine soils, can drive the evolution of metal tolerance in ECM fungi. We examined in vitro Ni tolerance in isolates of Cenococcum geophilum from serpentine and non-serpentine soils to assess whether isolates from serpentine soils exhibited patterns consistent with adaptation to elevated levels of Ni, a typical feature of serpentine. A second objective was to investigate the relationship between Ni tolerance and specific growth rates (micro) among isolates to increase our understanding of possible tolerance/growth trade-offs. Isolates from both soil types were screened for Ni tolerance by measuring biomass production in liquid media with increasing Ni concentrations, so that the effective concentration of Ni inhibiting fungal growth by 50% (EC(50)) could be determined. Isolates of C. geophilum from serpentine soils exhibited significantly higher tolerance to Ni than non-serpentine isolates. The mean Ni EC(50) value for serpentine isolates (23.4 microg ml(-1)) was approximately seven times higher than the estimated value for non-serpentine isolates (3.38 microg ml(-1)). Although there was still a considerable variation in Ni sensitivity among the isolates, none of the serpentine isolates had EC(50) values for Ni within the range found for non-serpentine isolates. We found a negative correlation between EC(50) and micro values among isolates (r = -0.555). This trend, albeit only marginally significant (P = 0.06), indicates a potential trade-off between tolerance and growth, in agreement with selection against Ni tolerance in "normal" habitats. Overall, these results suggest that Ni tolerance arose among serpentine isolates of C. geophilum as an adaptive response to Ni exposure in serpentine soils.
The community of ectomycorrhizal (ECM) and co-associated fungi from a serpentine site forested with Pinus sylvestris and Quercus petraea was explored, to improve the understanding of ECM diversity in naturally metalliferous soils. ECM fungi were identified by a combination of morphotyping and direct sequencing of the nuclear ribosomal internal transcribed spacer region 2 and of a part of the large-subunit region. Co-associated fungi from selected ECM were identified by restriction fragment length polymorphism and sequencing of representative clones from libraries. Polymerase chain reaction with species-specific primers was applied to assess patterns of association of ECM and co-associated fungi. Twenty ECM species were differentiated. Aphyllophoralean fungi representing several basidiomycete orders and Russulaceae were dominant. Phialocephala fortinii was the most frequently encountered taxon from the diverse assemblage of ECM co-associated fungi. A ribotype representing a deeply branching ascomycete lineage known from ribosomal deoxyribonucleic acid sequences only was detected in some ECM samples. A broad taxonomic range of fungi have the potential to successfully colonise tree roots under the extreme edaphic conditions of serpentine soils. Distribution patterns of ECM-co-associated fungi hint at the importance of specific inter-fungal interactions, which are hypothesised to be a relevant factor for the maintenance of ECM diversity.
To test the hypotheses that low nutrient levels and/or magnesium toxicity prevent the occurrence of Dryobalanops lanceolata (Dipterocarpaceae) on tropical ultramafic soils, a nutrient addition experiment was conducted. Dryobalanops lanceolata seedlings were planted in soil from Mount Tawai, an ultramafic mountain in central Sabah, Malaysia and subjected to four treatments: +P, +Ca, +NPK and +NPKCa. Addition of +P reduced the leaf mass per area but increased the leaf area ratio and foliar P concentrations. However, it did not increase the biomass or total leaf area of D. lanceolata. Additions of +NPK and +NPKCa increased the biomass, total leaf area, foliar P and K concentrations but not foliar N concentration. Calcium additions had no effect on seedling growth, indicating that magnesium toxicity was not important. The occurrence of D. lanceolata in this tropical ultramafic soil was limited by both potassium availability and low levels of soil phosphorus.
Metal toxicity (Al and heavy metals) is a major constraint affecting root growth in a number of natural or managed ecosystems. Fine roots of the majority of plant species are associated with mycorrhizal fungi, which may modify the sensitivity of roots to metal stress. In this review, we summarise the available evidence demonstrating beneficial effects of ectomycorrhizas in alleviation of metal toxicity in forest tree seedlings. We identify experimental shortcomings of past research (e.g. the use of shoot metal concentrations as a measure of metal uptake, use of microanalytical techniques biased by element redistribution) that may confound major conclusions drawn from these experiments. Although there is no doubt that in many cases ectomycorrhizal fungi indeed ameliorate metal stress in their host plants, the mechanism(s) involved remain(s) unclear. The role of metal sorption on fungal tissues thought to reduce metal exposure of the host plant is critically reviewed. As direct evidence (both under artificial and soil conditions) supporting a unique role of fungal immobilisation of metals is lacking so far, there is an urgent need to also test alternative tolerance mechanisms such as the release of metal chelating substances, or nutritional and hormonal effects mediated by mycorrhizal fungi.
Molecular tools have now been applied for the past 5 years to dissect ectomycorrhizal (EM) community structure, and they have propelled a resurgence in interest in the field. Results from these studies have revealed that: (i) EM communities are impressively diverse and are patchily distributed at a fine scale below ground; (ii) there is a poor correspondence between fungi that appear dominant as sporocarps vs. those that appear dominant on roots; (iii) members of Russulaceae, Thelephoraceae, and/or non-thelephoroid resupinates are among the most abundant EM taxa in ecosystems sampled to date; (iv) dissimilar plants are associated with many of the same EM species when their roots intermingle — this occurs on a small enough spatial scale that fungal individuals are likely to be shared by dissimilar plants; and (v) mycoheterotrophic plants have highly specific fungal associations. Although, these results have been impressive, they have been tempered by sampling difficulties and limited by the taxonomic resolution of restriction fragment length polymorphism methods. Minor modifications of the sampling schemes, and more use of direct sequencing, has the potential to solve these problems. Use of additional methods, such as in situ hybridization to ribosomal RNA or hybridization coupled to microarrays, are necessary to open up the analysis of the mycelial component of community structure.
In tropical rain forests the rate of litterfall is high, and is the most important nutrient cycling pathway in these ecosystems. We tested two hypotheses using seedlings of dipterocarp species: (1) addition of leaf litter improves growth; (2) and litter addition affects both ectomycorrhizal (ECM) colonization and community structure. Three dipterocarp species with contrasting ecologies (Parashorea tomentella, Hopea nervosa and Dryobalanops lanceolata) were grown in a nursery in forest soil with or without the addition of litter. Litter addition improved the growth of all three species. There was no effect of litter addition on total percentage ECM colonization but ECM diversity and percentage colonization by Cenococcum geophilum were lower with litter addition. Foliar delta(15)N was lower in two of the three species grown in the presence of litter, reflecting the lower delta(15)N of the litter compared with the soil. There was a negative correlation between delta(15)N and percentage ECM, suggesting a role for ECMs in accessing litter-derived N sources. This study shows that litter addition improved the growth of dipterocarp seedlings and that the ECM associations of dipterocarps facilitated access to this organic nutrient source. This has implications for the successful regeneration of seedlings in the rain forest understorey.
The large variability between soils classified as `serpentine' had been pointed out in the previous paper in this series. In this paper the ability of these soils to support plant growth is discussed. The growth of oats on serpentine soils is investigated and a range of response recorded. One soil from Kynance Cove, Cornwall, is quite fertile. Soils from the Keen of Hamar, Unst (see also Spence & Millar 1963) and the Hallival/Barkeval ridge, Rhum are demonstrated to be poor in available N, P and K. One soil, from Meikle Kilrannoch, Angus, is very toxic to oat plants, and a preliminary experiment suggests that high magnesium levels in the presence of low calcium are the cause of this. A number of species collected from on and off serpentine soils are compared when grown on serpentine and on John Innes Potting Compost. Serpentine ecotypes are demonstrated and the properties of these are discussed.
(1) Soil solutions were extracted by centrifugation from eleven soil samples from a toxic serpentine soil at Meikle Kilrannoch in Scotland. Analyses showed high concentrations of Mg2+ and NO- 3, low ones of Ca2+ and potentially toxic concentrations of Ni2+. (2) Nutrient solutions, with composition based on these analyses were prepared. In them were grown two clones of Festuca rubra; one from the Meikle Kilrannoch serpentine and the other from a non-serpentine acid brown earth. Four experiments with different combinations of Ca2+ and micronutrient concentrations were made. In each the effects of different concentrations of Mg2+ and Ni2+ on plant growth were measured. (3) The greatest growth of the Meikle Kilrannoch clone of F. rubra was in the water culture with concentrations most similar to soil solutions from the same site. The acid-soil clone plants grew very slowly in this solution. They grew fastest in solutions containing higher concentrations of micronutrients and lower ones of Mg2+, Ni2+ and Ca2+. (4) High Mg2+ concentration appeared to be the main cause of the slow growth of the acid-soil clone in Meikle Kilrannoch soils. However, Ni2+ was shown to be toxic also. (5) Both Mg2+ and Ni2+ toxicity were ameliorated by a higher concentration of Ca2+ and to some extent of micronutrients. The amelioration was associated with a reduction in tissue concentration of nearly all the elements analysed and may involve some restoration of membrane function.
This study aims to determine the influence of nutrient additions in the form
of nitrogen (N), phosphorus (P) and potassium (K) on the photosynthetic
physiology, morphology and growth of
Dryobalanops lanceolata Burck and
Shorea johorensis Foxw., two co-existing dipterocarp
species in the understorey of secondary forest. Analysis of the light
environment revealed that the total daily irradiance in the understorey was
4.57 ± 0.70 mol photons m–2
d–1, approximately 20% higher than that
which could be expected to occur in the primary forest understorey. Around
50% of total irradiance occurred at fluxes over 400 μmol photons
m–2 s–1, and this was
received over 7% of the daylight period. Both
D. lanceolata and S. johorensis
grew over the 16-month study, but only S. johorensis
increased growth in response to nutrient additions. Neither species altered
biomass partitioning in response to additional nutrients. Both species also
showed increased rates of photosynthetic induction
(T0.5Asat)
in response to nutrient additions, but only
S. johorensis showed an increase in light-saturated
rates of photosynthetic capacity
(Asat), and the chlorophyll
content of leaves. We argue that additional nutrients increased the capacity
of S. johorensis to utilise the sporadic burst of high
irradiance in sunflecks. Analysis of the nutrient composition of leaves from
age cohorts up to > 16 months showed that additional nutrients increased
the P and K concentration in D. lanceolata leaves, and
the P and N content of S. johorensis leaves. This
suggests that neither P nor K were limiting the growth of
D. lanceolata in this secondary forest environment, but
that P and/or N may limit growth of S. johorensis.
Our data highlights differences in the ecology of two co-existing dipterocarp
species. We argue that D. lanceolata shows
characteristics consistent with a low resource-demanding species that may have
a competitive advantage over S. johorensis in low
resource environments, while S. johorensis shows traits
better suited to higher resource availability. Thus, there are distinct
species-specific differences in the ability to respond to nutrients that
depend on the irradiance environment, and which may have a role in niche
partitioning among the dipterocarps.
S ummary
Details are presented of ectomycorrhizas in seventeen genera of tropical angiospermous trees from six families. Mycorrhizas of Intsia, Melaleuca, Monotes, Neea, Tristania and Vateria are figured for the first time. Overall, the tropical mycorrhizas are of a smaller diameter than is typical for those of temperate angiosperm trees but the sheaths are thicker and the fungus can form up to about 80% by weight of the dual organ. Our observations do not support the notion of a higher degree of host/fungus specificity in the tropics than in the temperate zones.
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Summary • The effects of Ni and Mg, two factors involved in the infertility of serpentine soils, were studied in the alpine plant Cerastium alpinum. Root growth of plants from adjacent serpentine and non-serpentine populations in Scandinavia, representing an eastern and western postglacial immigration lineage and the hybrid zone between them, were compared to study the adaptation of C. alpinum populations. • Seedlings were placed in solutions with low or high concentrations of Ni and Mg in a full factorial experiment according to a randomized block design. The growth of roots was analyzed and discussed in relation to the soil content. • The serpentine populations showed higher tolerance to Ni and Mg stress than non-serpentine populations. The degree of metal tolerance differed among the serpentine populations and was related to the effective concentrations of Ni and Mg in the soil at each site. • The results suggest that serpentine tolerance is locally evolved in C. alpinum and that tolerance has arisen in parallel during the postglacial colonization of Scandinavia on serpentine soils with similar composition.
• In tropical rain forests the rate of litterfall is high, and is the most important nutrient cycling pathway in these ecosystems. We tested two hypotheses using seedlings of dipterocarp species: (1) addition of leaf litter improves growth; (2) and litter addition affects both ectomycorrhizal (ECM) colonization and community structure.
• Three dipterocarp species with contrasting ecologies (Parashorea tomentella, Hopea nervosa and Dryobalanops lanceolata) were grown in a nursery in forest soil with or without the addition of litter.
• Litter addition improved the growth of all three species. There was no effect of litter addition on total percentage ECM colonization but ECM diversity and percentage colonization by Cenococcum geophilum were lower with litter addition. Foliar δ15N was lower in two of the three species grown in the presence of litter, reflecting the lower δ15N of the litter compared with the soil. There was a negative correlation between δ15N and percentage ECM, suggesting a role for ECMs in accessing litter-derived N sources.
• This study shows that litter addition improved the growth of dipterocarp seedlings and that the ECM associations of dipterocarps facilitated access to this organic nutrient source. This has implications for the successful regeneration of seedlings in the rain forest understorey.
High concentrations of heavy metals in soil have an adverse effect on micro-organisms and microbial processes. Among soil
microorganisms, mycorrhizal fungi are the only ones providing a direct link between soil and roots, and can therefore be of
great importance in heavy metal availability and toxicity to plants. This review discusses various aspects of the interactions
between heavy metals and mycorrhizal fungi, including the effects of heavy metals on the occurrence of mycorrhizal fungi,
heavy metal tolerance in these micro-organisms, and their effect on metal uptake and transfer to plants. Mechanisms involved
in metal tolerance, uptake and accumulation by mycorrhizal hyphae and by endo- or ectomycorrhizae are covered. The possible
use of mycorrhizal fungi as bioremediation agents in polluted soils or as bioindicators of pollution is also discussed.
Ectomycorrhizal fungi exhibit high diversity even in small monoculture forests. Roughly 20 to 35 species typically occupy such sites. Explanations for this diversity can be based on resource partitioning, disturbance, competition, or interaction with other organisms. Mycorrhizal fungi compete for two general classes of resources: host-derived carbon and soil or detritus derived mineral nutrients. Both types of resources are arrayed in space (e.g., soil depth, distance from tree) and time (e.g., season, host successional series). Some species seem to be partitioned in space and time at these scales, but the question of how widespread these patterns are remains largely unanswered. Mineral resources are distributed in discrete substrates in soil, litter, and within other soil microorganisms; the biochemical diversity exhibited by fungi may translate into differences in access to these resources among species. Small-scale natural disturbances that sever roots, mix soil horizons and litter layers, or change local pH and nutrient availability, are likely to create additional habitats for ectomycorrhizal fungi. Evidence from fruiting patterns and differences in colonization strategies suggest that such disturbances may be important for establishment of some species. Competitive replacement networks among species have the theoretical potential to increase diversity. The frequency of species replacements, observed co-infections of ectomycorrhizal fungi on single host roots, and high rates of rootlet turn-over all suggest that competition is important, but whether it plays a creative role in maintaining diversity remains to be demonstrated. Other organisms could be important in the maintenance of diversity, if they effect competition among mycorrhizal fungi. Bacteria and soil invertebrates are the most likely groups for such interactions. Technological advances in root observation and PCR methods for indentification of mycorrhizae make many of these theories testable.
The tropical Far East has many outcrops of ultramafic rock including very large areas in Sulawesi (c. 8000 km2) and New Caledonia (c. 5500 km2). The outcrops occur under several different climates, and give rise to a range of soils, the characteristics of which are reviewed. The vegetation on them is very varied. Under the same climate one can find grassland, scrub, and both short and tall rain forests. The variation in species richness on the ultramafics is difficult to explain. The degree of endemism varies too; it is probably less dependent on soil characteristics than on historical factors. The causes of the various unusual types of vegetation on ultramafic outcrops are discussed. It is possible that the somewhat dwarfed forests result from a shortage of one or more major nutrients or from very high soil Mg/Ca quotients or high Ni concentrations. The distinct ‘maquis’ vegetation of New Caledonia, and probably ultramafic scrub elsewhere, has evolved in relation to not only the soil chemical factors just listed but also periodic fire and varying degrees of drought. Fires are certainly more important than was once thought and the adverse soil factors may have a role in delaying recolonisation. The plant chemistry is notable for the presence of species which hyperaccumulate certain elements, notably Ni. This phenomenon is discussed in relation to its ecological importance, which may be protection of the hyperaccumulators against herbivores. The need for a conservation policy for the ultramafic areas is stressed, and mention is made of the restoration work on sites damaged by nickel mining in New Caledonia.
It has often been suggested that ectomycorrhizas ameliorate metal toxicity in forest trees. This pape will present a review of investigations carried out to assess amelioration of metal toxicity by ectomycorrhizas. These investigations have used a number of metals and a range of ectomycorrhizas. In a small number of cases amelioration of metal toxicity could be shown for specific metals by some fungi. In recent investigations on the ability of two species of ectomycorrhizas to improve Cd tolerance in Picea abies, a clear amelioration of Cd toxicity could be shown with Paxillus involutus. This improvement could not be related to decreased Cd uptake. However, in general, evidence suggests that ectomycorrhizas do not universally ameliorate metal toxicity. Amelioration is dependent upon the species and strain of the ectomycorrhiza and the metal being considered.
The diversity of ectomycorrhizal communities associated with Quercus garryana on and off serpentine soils was compared and related to landscape-level diversity. Serpentine soils are high in magnesium, iron, and heavy metals and low in fertility. In plant communities on serpentine soils, a high proportion of flowering plant species are endemic. At three sites with paired serpentine and nonserpentine soils in southwestern Oregon, we sampled Q. garryana roots and categorized ectomycorrhizas by morphotyping and by restriction fragment length patterns. Ectomycorrhizas were abundant at all sites; no single fungal species dominated in the ectomycorrhizas. Of 74 fungal species characterized by morphotype and pattern of restriction fragment length polymorphisms, 46 occurred on serpentine soils, and 32 were unique to serpentine soil. These species are potentially endemic to serpentine soil. Similarities in species composition between paired serpentine and nonserpentine soils were not significantly lower than among three serpentine sites or among three nonserpentine sites. We conclude that mycorrhizal communities associated with oaks on serpentine soil do not differ in species richness or species evenness from those on neighboring nonserpentine soil.
Scots pine seedlings were exposed to wet-deposited nickel (Ni) and removal of lichen cover in a dry heath Scots pine forest. Ni deposition affected the colonization of roots by indigenous ectomycorrhizal fungi in contrasting ways in intact and skimmed quadrats. Highest frequencies of tubercle morphotypes of ectomycorrhiza were found in quadrats exposed to 100 mg m(-2) year(-1) Ni in lichen covered treatment, while in skimmed quadrats these peaked after the treatment with 10 mg Ni m(-2) year(-1). Removal of the lichen layer increased the value of diversity index (H') of ectomycorrhizal fungal community, probably due to the increase in the evenness of the morphotype distribution. Lichen removal seemed also to improve the condition of the short roots, as the frequencies of poor and senescent short roots were decreased by the removal.
Mycorrhizal studies in dipterocarp forests in Indonesia
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Abundances of ectomycorrhizas on the slopes of Mount Kinabalu, Sabah, Malaysian Borneo
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