Coinoculation of bioinoculants improve <Emphasis Type="Italic">Acacia auriculiformis</Emphasis> seedling growth and quality in a tropical Alfisol soil

We conducted a study to find out if arbuscular mycorrhizal (AM) fungi (Acaulospora scrobiculata, Scutellospora calospora) and phosphate solubilizing bacteria (PSB, Paenibacillus polymyxa) inoculation either individually or in combinations can improve Acacia auriculiformis seedling growth, uptake of nutrients and quality in a phosphorus deficient tropical Alfisol. The seedlings were assessed for various growth and nutrient uptake parameters after 60 days of treatment. Inoculation with P. polymyxa stimulated mycorrhizal formation. Seedling height, stem girth, taproot length, number of leaves and leaf area, plant dry matter production, nodulation, and nodular dry weight were significantly higher for seedlings that were either dual inoculated or triple inoculated compared to individual inoculation of AM fungi or PSB, and uninoculated seedlings. Dual and triple application of AM fungi and PSB also significantly improved the nutrient contents of shoots and roots and nutrient uptake efficiencies. The calculated seedling quality indexes of the AM fungi and PSB inoculated seedling were 25–208% higher than uninoculated seedlings. These findings show that A. auriculiformis seedlings when dual inoculated or triple inoculated performed better than seedlings inoculated with the microbes individually and compared with uninoculated control seedlings. We conclude that bioinoculation is important for the production of high-quality A. auriculiformis seedlings in tree nurseries for planting in nutrient deficient soils.     

Growth and nutrient uptake of ectomycorrhizal Pinus sylvestris seedlings in a natural substrate treated with elevated Al concentrations

Models of the effects of elevated concentrations of aluminum (Al) on growth and nutrient uptake of forest trees frequently ignore the effects of mycorrhizal fungi. In this study, we present novel data indicating that ectomycorrhizal mycelia may prevent leaching of base cations and Al. Mycorrhizal and non-mycorrhizal Pinus sylvestris L. seedlings were grown in sand obtained from the B-horizon of a local forest. In Experiment 1, non-mycorrhizal seedlings and seedlings inoculated with Hebeloma cf. longicaudum (Pers.: Fr.) Kumm. ss. Lange or Laccaria bicolor (Maire) Orton were provided with nutrient solution containing 2.5 mM Al. Aluminum did not affect growth of non-mycorrhizal seedlings or seedlings inoculated with L. bicolor. Seedlings colonized by H. cf. longicaudum had the highest biomass production of all seedlings grown without added Al, but the fungus did not tolerate Al. Shoots of seedlings colonized by L. bicolor had the lowest nitrogen (N) concentrations but the highest phosphorus (P) concentrations of all seedlings. The treatments had small but significant effects on shoot and root Al concentrations. In Experiment 2, inoculation with L. bicolor was factorially combined with the addition of a complete nutrient solution, or a solution lacking the base cations K, Ca and Mg, and solutions containing 0 or 0.74 mM Al. Seedling growth decreased in response to 0.74 mM Al, but the effect was significant only for non-mycorrhizal seedlings. Mycorrhizal seedlings generally had higher P concentrations than non-mycorrhizal seedlings. Aluminum reduced P uptake in non-mycorrhizal plants but had no effect on P uptake in mycorrhizal plants. Mycorrhizal colonization increased the pH of the soil solution by about 0.5 units and addition of Al decreased the pH by the same amount. We conclude that the presence of ectomycorrhizal mycelia decreased leaching of base cations and Al from the soil.     

Arbuscular mycorrhizal associations in Boswellia papyrifera (frankincense-tree) dominated dry deciduous woodlands of Northern Ethiopia

This study assessed the arbuscular mycorrhizal (AM) status of Boswellia papyrifera (frankincense-tree) dominated dry deciduous woodlands in relation to season, management and soil depth in Ethiopia. We studied 43 woody species in 52 plots in three areas. All woody species were colonized by AM fungi, with average root colonization being relatively low (16.6% – ranging from 0% to 95%). Mean spore abundance ranged from 8 to 69 spores 100 g⁻¹ of dry soil. Glomus was the dominant genus in all study sites. Season had a strong effect on root colonization and spore abundance. While spore abundance was higher (P < 0.001) in the dry season in all three study sites, root colonization showed a more variable response. Root colonization was reduced in the dry season in the site that was least subject to stress, but increased in the dry season in the harshest sites. Management in the form of exclosures (that exclude grazing) had a positive effect on spore abundance in one of the two sites considered. Spore abundance did not significantly differ (P = 0.17) between the two soil depths. Our results show that in this arid region all trees are mycorrhizal. This has profound consequences for rehabilitation efforts of such dry deciduous woodlands: underground processes are vital for understanding species adaptation to pulsed resource availability and deserve increasing attention.     

丛枝菌根真菌对牡丹根系构型的影响

本试验以分别接种AM真菌Glomus mosseae和G.versiforme的两年生盆栽‘凤丹’幼苗为材料,以不接种为对照,研究不同AM真菌对牡丹幼苗根系构型和生长的影响。结果表明:不同AM真菌的侵染率不同,G.mosseae的侵染率高于G.versiforme;接种G.mosseae的植株干重、根冠比和根系活力显著高于对照。接种不同AM真菌的牡丹幼苗的根系参数均比对照有不同程度的增加,其中对水平延伸根系所占比例和根系总体积的影响最为显著。相关性分析表明,水分饱和亏缺与植株干重、根冠比、根系活力等呈显著负相关;根系参数与牡丹生长呈显著正相关。不同AM真菌可通过影响牡丹幼苗的根系构型而影响其生长。G.mosseae是促进牡丹生长的高效菌种。     

Arbuscular mycorrhizal induced changes to plant growth and root system morphology in Prunus cerasifera

We compared root system morphogenesis of micropropogated transplants of Prunus cerasifera L. inoculated with either of the arbuscular mycorrhizal (AM) fungi Glomus mosseae or Glomus intraradices or with the ericoid mycorrhizal species Hymenoscyphus ericae. All plants were grown in sand culture, irrigated with a nutrient solution that included a soluble source of phosphorus, for 75 days after transplanting. Arbuscular mycorrhizal colonization increased both the survival and growth (by over 100%) of transplants compared with either uninoculated controls or transplants inoculated with H. ericae. Arbuscular mycorrhizal colonization increased root, stem and leaf weights, leaf area, root length and specific leaf area, and it decreased root length/leaf area ratio, root/shoot weight ratio and specific root length. Both uptake of phosphorus and its concentration in leaves were increased by AM infection, although the time course of the relationships between intensity of AM infection and P nutrition were complex and suggested a role for factors other than nutrition. The time course for the development of infection varied. It was most rapid with G. mosseae, but it was ultimately higher with G. intraradices. None of the treatments significantly affected the lengths of adventitious roots or the first-, second- or third-order laterals that developed from them. Arbuscular mycorrhizal colonization increased the intensity of branching in all root orders with the effect being most obvious on first-order lateral roots where the number of branches increased from under 100 to over 300 brances m(-1). As a result, although first-order laterals made up 55% of the root systems of control plants, the comparable value was 36% in AM-infected plants. In contrast, second-order laterals represented 25% of control root systems, but 50% of AM-colonized root systems. Glomus intraradices but not G. mosseae increased root diameter. Anatomical studies revealed no changes in the overall form of the root tip, although there were changes in the diameter of the root cap, cell numbers and cell size. Hymenoscyphus ericae increased the duration of the metaphase index. Both AM fungal treatments increased the concentrations of soluble proteins in root extracts and modified the protein profiles by the elimination and addition of protein bands detected by PAGE analysis. We conclude that AM fungal inoculation influenced processes in the root system at different levels, but not all effects were due to improved P nutrition or increased physiological age.     

Arbuscular mycorrhizas and performance of Polylepis australis trees in relation to livestock density

Polylepis australis trees endemic to Argentina dominate the canopy of subtropical high altitude forests. Here, livestock rearing is the main economic activity and is suspect of the low performance of P. australis trees through direct and indirect effects which could include the reduction in arbuscular mycorrhizal fungi (AMF) and their benefit to trees. To elucidate the role of AMF, we compare plant performance indicators, arbuscular mycorrhizal (AM) colonization and AMF communities in 20 trees distributed in two areas of central Argentina which differed in livestock grazing intensity. The area with high livestock density presented more soil degradation and trees with a lower overall plant performance than the area with reduced livestock density. The AM colonization values of P. australis were considerably higher than reported for other tree species and the area with high livestock density had a lower proportion of arbuscules and higher proportion of hyphae, while vesicles and AM colonization – all structure considered together – did not differ between areas. Overall AMF spore number and of most species when considered separately was significantly higher in the area with high livestock density, suggesting a high tolerance and adaptation of AMF to livestock. We conclude that a reduction in livestock improves the performance of P. australis, that this improvement could be mediated by an increase in the proportion of arbuscules, but there does not appear to be any limitation in AM colonization or AMF spore number which could otherwise be limiting forest restoration.     

Effects of arbuscular mycorrhizal fungi on leaf solutes and root absorption areas of trifoliate orange seedlings under water stress conditions

The effects of the arbuscular mycorrhizal (AM) fungus Glomus mosseae on plant growth, leaf solutes and root absorption area of trifoliate orange (Poncirus trifoliata (L.) Raf.) seedlings were studied in potted culture under water stress conditions. Inoculation with G. mosseae increased plant height, stem diameter, leaf area, shoot dry weight, root dry weight and plant dry weight, when the soil water content was 20%, 16% and 12%. AM inoculation also promoted the active and total absorption area of root system and absorption of phosphorus from the rhizosphere, enhanced the content of soluble sugar in leaves and roots, and reduced proline content in leaves. AM seedings had higher plant water use efficiency and higher drought tolerance than non-AM seedlings. Effects of G. mosseae inoculation on trifoliate orange seedlings under 20% and 16% soil water content were more significant than under 12% soil water content. AM infection was severely restrained by 12% soil water content. Thus, effects of AM fungi on plants were probably positively related to the extent of root colonization by AM fungi. The mechanism of AM fungi in enhancing drought resistance of host plants ascribed to greater osmotic adjustment and greater absorption area of root system by AM colonization. __________ Translated from Journal of Plant Physiology and Molecular Biology, 2005, 30(5): 583–588 [译自: 植物生理与分子生物学报, 2005, 30(5): 583–588]     

Effect of the arbuscular mycorrhizae <Emphasis Type="Italic">Glomus fasciculatum</Emphasis> and <Emphasis Type="Italic">G. macrocarpum</Emphasis> on the growth and nutrient content of <Emphasis Type="Italic">Cassia siamea</Emphasis> in a semi-arid Indian wasteland soil

The effect of two arbuscular mycorrhizal (AM) fungi, Glomus fasciculatum and G. macrocarpum on shoot and root dry weights and nutrient content of Cassia siamea in a semi-arid wasteland soil was evaluated. Under nursery conditions, mycorrhizal inoculation improved growth of seedlings. Root and shoot dry weights were higher in mycorrhizal than non-mycorrhizal plants. The concentration of P, K, Cu, Zn and Na was significantly higher in AM inoculated seedlings than in non-inoculated seedlings. Mycorrhization led to decrease in alkalinity of the rhizosphere soil from pH 8.5 to 7.4. Under nursery conditions, the degree of mycorrhizal dependency increased with age of C. siamea seedling. On transplantation to the field, the survival rate of mycorrhizal seedlings (75%–90%) was higher than that of non-mycorrhizal seedlings (40%). Besides better survival rate, AM inoculation improved the growth performance of seedlings in terms of height and stem diameter. Among the two AM fungi used, the efficiency of Glomus macrocarpum was higher than that of G. fasciculatum under both nursery and field conditions.This revised version was published online in May 2005 with corrected page numbers.     

Improvement of early growth of two tropical peat-swamp forest tree species Ploiarium alternifolium and Calophyllum hosei by two arbuscular mycorrhizal fungi under greenhouse conditions

Tropical peat-swamp forests are one of the largest near-surface reserves of terrestrial carbon. However, many peat-swamp forest tree species have resulted in the reduction due to over-exploitation, forest fires and conversion into agricultural land in Indonesia. The objective of this study was to determine the effects of two arbuscular mycorrhizal (AM) fungi, Glomus clarum and G. aggregatum, on the early growth of two slow-growing peat-swamp forest tree species, Ploiarium alternifolium and Calophyllum hosei, under greenhouse conditions. Cuttings of P. alternifolium and C. hosei were uninoculated or inoculated with G. clarum and G. aggregatum and grown under greenhouse conditions for 6 months. Percentage AM colonization, plant growth, phosphorus (P) concentration and survival rate were measured. The AM colonization of P. alternifolium and C. hosei ranged from 27 to 32% and 18 to 19%, respectively. Colonization by G. clarum and G. aggregatum increased shoot height, stem diameter, leaf number, and shoot and root dry weights. Cutting shoot P content were increased by AM fungal colonization. The survival rates of inoculated plants were higher (100%) than those of control plants (67%). The results suggest that inoculation with AM fungi improves early growth of P. alternifolium and C. hosei in a tropical peat-swamp forest and can therefore contribute to rehabilitation of peat-swamps.     

Growth response of <Emphasis Type="Italic">Acacia mangium</Emphasis> Willd. seedlings to arbuscular mycorrhizal fungi and four isolates of the ectomycorrhizal fungus <Emphasis Type="Italic">Pisolithus tinctorius</Emphasis> (Pers.) Coker and Couch

Some Acacia mangium Willd. plantations in Asia grow poorly due to low soil fertility and the absence of compatible mycorrhizal fungi. This legume tree can be colonized by arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi but inoculation is not routinely practiced. This study aimed to compare the effectiveness of AM fungi and four isolates of the ECM fungus Pisolithus tinctorius (Pers.) Coker and Couch (Pt) in promoting growth of A. mangium seedlings under glasshouse conditions. AM inoculants were: Glomus etunicatum, G. fasciculatum, G. macrocarpum and Gigaspora margarita and mixed species extracted from rhizosphere soil of a Populus stand in Suwon (AMKFRI), and Carex (AMM6) and Populus (AMM7) growing in mine tailings in Korea. Pisolithus isolates were from Philippines (PtPhil) and Korea (PtKFRI, PtMKACC, PtKACC). Generally, ECM fungi promoted height and diameter growth of A. mangium more than the AM inoculants. The Korean Pisolithus increased plant dry weight by 122–145%, mixed AM inoculants by 61–97%, and Glomus and Gigaspora by 45–72% over the control. PtKACC gave the highest root colonization and promoted the highest growth and concentration of most nutrients. Mycorrhizal root colonization was positively correlated with plant dry weight, Na, Fe and Cu concentrations and N, P, K, Ca, Na, Fe and Cu contents. In conclusion, the results provide strong evidence for benefits of mycorrhizal inoculation on A. mangium seedlings under glasshouse conditions. The Korean Pisolithus isolates (particularly PtKACC), and two AM fungi (AMKFRI and AMM6) are potential mycorrhizal inoculants but their effectiveness and persistence should be determined on degraded lands in tropical countries where A. mangium is being planted for rehabilitation.     

Arbuscular mycorrhizal fungi in the rhizosphere of Macaranga denticulata Muell. Arg., and their effect on the host plant

A fallow enriching tree, Macaranga denticulata Muell. Arg., has been shown to increase rice yield in a rotational shifting cultivation system in northern Thailand through increased accumulation of mineral nutrients. As arbuscular mycorrhizal (AM) fungi may play an important role in nutrient accumulation, AM fungi in the rhizosphere of M. denticulata and the effects of the indigenous soil inoculum on the host plant were investigated. The diversity and abundance of AM fungi were documented for the rhizosphere of M. denticulata in the field for two years. Based on morphology, 29 species of AM fungi were found in the rhizosphere of M. denticulata growing in farmers’ fields. Root colonization ranged from 63.5 to 81.5% in the first year and 68.7 to 79.9% in the second year of study. The highest spore density was observed at the end of the wet season. The effects of indigenous soil inoculum, and N and P fertilizers on the host plant were investigated in pots for four months. Inoculation with soil-containing AM fungi strongly increased plant growth and nutrient contents when P was limiting but N was applied. Application of N and P together strongly depressed root colonization and spore density of AM fungi, whereas applying them separately had much less effect. AM fungi may play an important role in nutrient accumulation in M. denticulata-rich fallow and thus in nutrient cycling that is beneficial to the maintenance of upland rice yield and sustainability of the rotational shifting cultivation system. This revised version was published online in June 2006 with corrections to the Cover Date.     

丛枝菌根真菌提高林木抗逆性机制研究进展

丛枝菌根（AM）真菌是存在于土壤中的重要真菌之一,它能够与宿主林木根系产生互利共生体,从而对林木的生长发育有着多种促进作用。文中综述了近10年来国内外关于AM真菌对林木影响的研究进展,包括AM真菌对林木的抗旱性、抗病性、抗盐性、耐热性、耐虫性及对有害重金属抗性的影响等,通过促进林木光合作用、营养吸收、新陈代谢等来增加林木生长量、生物量的积累,从而提高林木的抗逆性;对在AM真菌研究中存在的难题进行了分析,并对其在林木中的应用研究进行了展望,旨在为林木抗逆性机制研究、森林经营等提供科学参考。     

Seed source and vesicular-arbuscular mycorrhizal symbiont affects growth of Juglans nigra seedlings

Seedlings of Juglans nigra from three seed sources were grown in fumigated soil without vesicular-arbuscular mycorrhizal (VAM) fungi or inoculated with Gigaspora margarita, Glomus deserticola or Glomus etunicatum. Vesicular-arbuscular mycorrhizal development varied significantly between fungal symbionts within a black walnut source. Glomus deserticola and G. etunicatum produced the highest levels of root colonization in all sources. Significant differences in seedling shoot and root growth were attributed to root colonization by specific VAM fungi in each black walnut source. Glomus deserticola stimulated seedling leaf area and root weight 26 and 52%, respectively, in one seed source. Seedling leaf N, P and K concentrations were significantly improved by VAM in two seed sources. Juglans nigra seedlings respond favorably to VAM colonization. However, differences between seed sources suggest a strong host-symbiont interaction.     

Ectomycorrhizas and cadmium toxicity in Norway spruce seedlings

We studied the effects of ectomycorrhizal colonization by Laccaria bicolor (Maire) Orton S238 and Paxillus involutus (Batsch) Fr. 533 on cadmium (Cd) toxicity in Norway spruce seedlings (Picea abies (L.) Karst.). Both mycorrhizal and nonmycorrhizal seedlings were exposed to 0 (control), 0.5 or 5 &mgr;M CdSO(4) for 9 weeks in a sand culture system with frequent addition of nutrient solutions. In pure culture, P. involutus and L. bicolor showed similar Cd tolerance. However, in symbiosis, the Cd treatments decreased colonization by L. bicolor but not by P. involutus. Paxillus involutus ameliorated the negative effects of 0.5 &mgr;M Cd on shoot and root growth and chlorophyll content of old needles, whereas L. bicolor did not. Mycorrhizal colonization did not affect Cd concentrations of old needles and roots of seedlings. Despite differences between the ectomycorrhizal fungi in colonization and ability to alleviate Cd toxicity of seedlings, both species reduced Cd concentrations of young needles to a similar degree compared with nonmycorrhizal seedlings. However, in the 0.5 &mgr;M Cd treatment, the Cd content of needles of seedlings colonized by P. involutus was increased, whereas the Cd content of needles of seedlings colonized by L. bicolor was similar to that of needles of nonmycorrhizal seedings. When the amount of Cd translocated to needles was expressed on a root length basis to account for differences in the size of the root systems, the amount of Cd translocated to the needles was similar in seedlings mycorrhizal with P. involutus and in nonmycorrhizal seedlings. All mycorrhizal seedlings were similarly affected by 5 &mgr;M Cd, indicating that the amelioration efficiency of ectomycorrhizal fungi is dependent on the metal concentration to which the roots are exposed. Concentrations of P, K, Ca, Mg and Mn were decreased by 5 &mgr;M Cd to a similar extent in both nonmycorrhizal and mycorrhizal seedlings. In contrast to L. bicolor, P. involutus increased P uptake and altered patterns of root branching. We conclude that mycorrhizas alleviate Cd-induced reductions in growth of Picea abies seedlings. Although the two mycorrhizal fungi examined differed in their ability to alleviate Cd toxicity, these differences were not related to differences in Cd uptake or translocation to the shoot of the mycorrhizal seedlings. We suggest that amelioration of Cd toxicity by P. involutus may be a result of improved P nutrition or changes in root morphology, or both.     

The influence of Desert False Indigo, <Emphasis Type="Italic">Amorpha fruticosa</Emphasis>, and three arbuscular mycorrhizae fungi on the growth of <Emphasis Type="Italic">Populus ussuriensis</Emphasis> seedlings

The influence of Desert False Indigo, Amorpha fruticosa, on the growth of Populus ussuriensis seedlings inoculated with three arbuscular mycorrhizae (AM) fungi (Glomus mosseae, Glomus intraradices, Glomus sinuosa) was studied using the nylon net method. The results showed that all three AM fungi infected P. ussuriensis seedlings and G. intraradices and also G. mosseae infected A. fruticosa. The AM fungi promoted growth of P. ussuriensis and Desert False indigo seedlings. Moreover, under co-cultivation with A. fruticosa, the biomass of P. ussuriensis increased significantly. The concentration of nitrogen in P. ussuriensis grown with A. fruticosa and the concentration of soluble nitrogen in the rhizosphere were also higher than when grown alone. Hypha were found on the two plant seedlings inoculated with G. mosseae and G. intraradices, suggesting that AM fungi may transport nutrients from seedlings of A. fruticosa to the rhizosphere of P. ussuriensis seedlings, which may have promoted the growth of P. ussuriensis. The AM fungi played a critical role on the effect of A. fruticosa on growth of P. ussuriensis.     

蓝桉和尾叶桉混合菌根研究 Ⅰ.菌根合成及真菌间的相互作用

采用蜡磨菌与ＶＡ 菌根真菌分别对蓝桉和尾叶桉进行单接种或混合接种,研究结果表明,两种菌根类型的真菌均能在桉树苗木根系上成功地定殖,分别合成了外生菌根、ＶＡ 菌根和混合菌根,证实了桉树不仅是菌根营养型树种,而且能形成多种菌根类型。ＶＡ 菌根感染率在接种初期较高,但随时间的推移有降低的趋势;而外生菌根菌初期合成菌根的速度较慢,但单位长度根段内菌根根尖数目有明显增加的趋势。与单接种ＶＡ菌根真菌苗木相比,外生菌根真菌抑制了ＶＡ 菌根菌在根系上的进一步侵染,体现在较低的ＶＡ 菌根感染率;而外生菌根菌显示出了较强的竞争能力,并能在接种后９ 周时开始形成子实体。在混合菌根中,外生菌根有逐步替代ＶＡ 菌根的发展趋势,两种类型的菌根真菌间存在一定的竞争性作用关系。基质磷（Ｐ）素水平对菌根的形成也有一定的影响     

Growth response and nutrient utilization of <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> seedlings inoculated with bioinoculants under tropical nursery conditions

We investigated the role of tetrapartite associations between an arbuscular mycorrhizal (AM) fungus (Glomus geosporum), phosphate solubilizing bacteria (Paenibacillus polymyxa), Frankia and Casuarina equisetifolia on growth, nutrient acquisition, nutrient utilization and seedling quality of C. equisetifolia. Seedlings of C. equisetifolia were grown in an Alfisol soil and inoculated with G. geosporum, P. polymyxa and Frankia either individually or in combinations. Inoculation of bioinoculants stimulated seedling growth, the efficiency of nutrient uptake and improved seedling quality. However, microbial inoculation generally reduced the efficiency of nutrient utilization in dry matter production (nutrient use efficiency). Inoculation of P. polymyxa or Frankia increased the extent of AM colonization, which resulted in the accumulation of the nutrients. Seedlings inoculated with Frankia and G. geosporum had more, and heavier nodules compared to seedlings inoculated with Frankia alone. Dual inoculation of microbes was more effective than individual inoculations. The growth response of seedlings to inoculation involving all the microbes was greater than the response to either individual or dual inoculations. The results of this study showed that the tetrapartite association could improve the growth, nutrient acquisition and seedling quality of C. equisetifolia under tropical nursery conditions.     

Growth of Nursery-grown Bamboo Inoculated with Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria in two Tropical Soil Typeswith and without Fertilizer Application

A nursery experiment was conducted to assess the effect of bioinoculants (Glomus aggregatum, Bacillus polymixa, Azospirillum brasilense) on seedling growth promotion of bamboo (Dendrocalamus strictus (Roxb.) Nees.) in two soil types (alfisol, vertisol) with or without fertilizer application. Bamboo seedlings were grown in the presence or absence of bioinoculants either individually or in all combinations for 180 days in field soil under tropical nursery conditions. Shoot, rhizome and root length, dry masses, nutrient concentrations and arbuscular mycorrhizal (AM) colonized root lengths were determined at harvest. Under the experimental condition tested combined inoculation of AM fungi, PSB and A. brasilense resulted in maximum growth response both under fertilized and unfertilized conditions in both soil types. Fertilizer application enhanced the efficiencies of N, P and K uptake, whereas reduced their usage efficiencies. Though soil type did not affect microbial inoculation response, fertilizer application significantly affected plant response to microbial inoculation.     

Mycorrhizal associations in the rain forest of South Cameroon

Mycorrhizal associations of important tree species were investigated within the research area of the Tropenbos Cameroon Programme (TCP), situated on the western portion of the Atlantic Biafrean forest of south Cameroon. Ninety-seven tree species of economic, social, and ecological importance, and three lianas were selected in three sites that differed in altitude, soil clay content, and soil pH. In each site plots were laid out in undisturbed forest. In each plot, seedlings, saplings, juvenile, and mature trees were identified to species level and counted; girth at breast height measured and basal area calculated; root samples were taken and examined for mycorrhizal type and extent of mycorrhizal colonization.

All 100 species investigated were mycorrhizal. Tree of 74 species formed exclusively arbuscular mycorrhizas (AM); 23 trees and three Gnetum species formed ectomycorrhizas (ECM). Five of these ECM plants also harbored AM structures. Extent of mycorrhizal root colonization showed large differences for various AM trees; however, colonization of more than half of these trees was less than 25%. Colonization of ECM trees was often higher than 75%. The contribution of ECM trees to basal area varied between 19 and 35%. ECM trees often occurred in small to large clumps. In sustainable forest management plans, existing ECM forest clumps should be given special conservation value.     

Effect of exclosure ages on woody plant structure,diversity and regeneration potential in the western Tigray region of Ethiopia

Exclosure is a method of rehabilitating degraded lands by protecting them from the interference of animals and from human encroachment, and is used to regenerate native vegetation as a way to reduce soil erosion, increase rain water infiltration and provide fodder and woody biomass in degraded grazing lands. Therefore, we studied woody plant structure, diversity and regeneration potentials in 5- and 10-year grazing exclosures in comparison with open grazed sites in a semi-arid environment. Data on species diversity, abundance, structure, basal area, frequency, density, and regeneration status were collected from 270 sample plots. Forty-one woody species representing 20 families were identified, with 18, 28 and 38 species found in open grazed areas, and in 5- and 10-year grazing exclosures, respectively. The 10-year grazing exclosures had a higher (P < 0.05) species richness and plant densities compared to the 5-year grazing exclosures and the open grazed areas. The population structure and regeneration status of woody species in both grazing exclosures showed an inverted J-shape, indicating a healthy regeneration status, whereas hampered regeneration was observed in open grazed areas. The establishment of grazing exclosures had positive effects in restoring woody plant diversity and improving vegetation structure and regeneration potentials of degraded grazing lands.