Comparisons of Mycorrhizal Responsiveness with Field Soil and Commercial Inoculum for Six Native Montane Species and Bromus tectorum

Reestablishing native perennial plants and reducing invasive species are pivotal for many ecological restoration projects. The interactions among plant species, arbuscular mycorrhizal fungi, and soil P availability may be critical determinants of the success of native and non‐native plants in restoration and species invasions. Here we assessed mycorrhizal responsiveness for three late‐successional and three early‐successional plant species native to Rocky Mountain National Park and for the non‐native Downy brome, cheatgrass (Bromus tectorum L.) using field soil and commercial inoculum. Factorial greenhouse experiments were conducted to compare biomass of plant species with and without field soil and commercial inoculum treatments along a phosphorus (P) gradient, which ranged from ambient field levels to 12% of field levels, using dilutions of native soils. The two field soil inoculum treatments resulted in significant biomass differences for all species studied. Late‐successional species responded positively to field inoculum, whereas early‐successional species responded negatively. The two commercial inocula had low colonization rates (14 of 166 inoculated plants). The commercial inocula substrates had significant treatment effects on five of seven species included in the study in the apparent absence of mycorrhizal symbiosis. Soil P levels influenced mycorrhizal responsiveness in only one species, Smooth blue aster (Aster laevis L.). Our results show that, at least for the species studied here, locally collected field inoculum is the best choice for reestablishment of late‐successional native plant species.     

Availability and function of arbuscular mycorrhizal and ectomycorrhizal fungi during revegetation of dewatered reservoirs left after dam removal

Revegetation following dam removal projects may depend on recovery of arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungal communities, which perform valuable ecosystem functions. This study assessed the availability and function of AM and EM fungi for plants colonizing dewatered reservoirs following a dam removal project on the Elwha River, Olympic Peninsula, Washington, United States. Availability was assessed via AM fungal spore density in soils and EM root tip colonization of Salix sitchensis (Sitka willow) in an observational field study. The effect of mycorrhizal fungi from 4 sources (reservoir soils, commercial inoculum, and 2 mature plant community soils) on growth and nutrient status of S. sitchensis was quantified in a greenhouse study. AM fungal spores and EM root tips were present in all field samples. In the greenhouse, plants receiving reservoir soil inoculum had only incipient mantle formation, while plants receiving inoculum from mature plant communities had fully formed EM root tips. EM formation corresponded with alleviation of phosphorus stress in plants (lower shoot nitrogen:phosphorus). Thus, revegetating plants have access to AM and EM fungi following dam removal, and EM formation may be especially important for plant P uptake in reservoir soils. However, availability of mycorrhizal fungi declines with distance from established plant communities. Furthermore, EM fungal communities in recently dewatered reservoirs may not be as effective at forming beneficial mycorrhizae as those from mature plant communities. Whole soil inoculum from mature plant communities may be important for the success of revegetating plants and recovery of mycorrhizal fungal communities.     

Local soil,but not commercial AMF inoculum,increases native and non‐native grass growth at a mine restoration site

Soil communities are often degraded in mined sites, and facilitating the recovery of soil mutualists such as arbuscular mycorrhizal fungi (AMF) may assist with the restoration of native plants. At a grassland mine restoration site, I compared a commercial AMF inoculum with soil collected from beneath native grasses as a source of inoculum, as well as a control treatment. Field plots were broadcast‐inoculated and seeded with native grasses, and biomass of native and non‐native species was measured in three consecutive years. In addition, greenhouse‐grown seedlings of a native bunchgrass (Stipa pulchra) were inoculated with similar treatments, transplanted into the field, and assessed after 18 months. When broadcast inoculation was used, the local soil inoculum tended to increase non‐native grass biomass, and marginally decreased non‐native forb biomass in the second year of study, but did not significantly affect native grass biomass. Broadcast commercial inoculum had no detectable effects on biomass of any plant group. Stipa pulchra transplants had greater N content and mycorrhizal colonization, and marginally higher shoot mass and K content, when pre‐inoculated with local soil (relative to controls). Pre‐inoculation with commercial AMF increased AMF colonization of the S. pulchra transplants, but did not significantly affect biomass or nutrient content. The findings indicate that at this site, the use of local soil as an inoculum had greater effects on native and non‐native plants than the commercial product used. In order to substantially increase native grass performance, inoculation of transplanted plugs may be one potential strategy.     

Adaptation of plant‐mycorrhizal interactions to moisture availability in prairie restoration

The strength and direction of plant response to inoculation with arbuscular mycorrhizal fungi (AM fungi) is dependent on both abiotic and biotic contexts, often generating patterns of AM fungal mediation of plant adaptation. However, knowledge of plant‐community level effects of these interactions in grassland restoration is limited. We conducted a field inoculation experiment by inoculating five plant species native to a drier prairie and five plant species native to a moister prairie with mycorrhizal fungal communities from each prairie type. Species were paired by genus or family to account for phylogenetic effects. The inoculated plants were transplanted to study plots seeded with a restoration seed mix. Plots were manipulated to create either moister or drier conditions similar to environments of the plant species and mycorrhizal communities. In both transplanted and seeded plant species, we found that only drier prairie‐range species benefited from moisture‐regime matched AM fungal inoculum. Other seeded prairie plant species demonstrated a negative response to inoculation, likely due to the earlier successional stage of these species. Additionally, nonseeded plants benefited from inoculation in different ways: native nonseeded plants had highest cover with drier prairie inoculum in drier conditions, while nonnative plants had highest cover with moister prairie‐origin inoculum. These results suggest that use of local AM fungi may be particularly important in restorations at drier sites, even at relatively small differences in moisture availability. Further, specific knowledge of relative responsiveness of seeded plant species and nonseeded plant species to AM fungal inoculation will be useful in planning restorations.     

Inoculation with native soil improves seedling survival and reduces non-native reinvasion in a grassland restoration

Losses of grasslands have been largely attributed to widespread land-use changes, such as conversion to row-crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non-native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non-native plants. In addition to the direct and indirect effects of non-native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam-pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non-native invasive Bothriochloa bladhii (Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30% B. bladhii cover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non-native species.     

Effects of Mycorrhizae and Nontarget Organisms on Restoration of a Seasonal Tropical Forest in Quintana Roo, Mexico: Factors Limiting Tree Establishment

We initiated a study of the effects of mycorrhizal fungal community composition on the restoration of tropical dry seasonal forest trees. Tree seedlings were planted in a severely burned experimental site (1995 fire) during the growing season of 1998 at the El Edén Ecological Reserve, in north Quintana Roo, Mexico. Seedlings of Leucaena leucocephala, Guazuma ulmifolia, Caesalpinia violacea, Piscidia piscipula, Gliricidia sepium, and Cochlospermum vitifolium were germinated in steam‐sterilized soil and either remained uninoculated (nonmycorrhizal at transplanting) or were inoculated with mycorrhizal fungi in soils from early‐seral (recently burned) or late‐seral (mature forest) inoculum. Inoculum from the early‐seral soil was largely Glomus spp., whereas a diverse community of arbuscular mycorrhizal fungi were reintroduced from the mature forest including species of Scutellospora, Gigaspora, Glomus, Sclerocystis, and Acaulospora. Plants grew better when associated with the mature forest inoculum, unlike a previous experiment in which plants grew taller with the early‐seral inoculum. Reasons for the different responses include a less‐intense burn resulting in more residual organic matter. In addition to mycorrhizal responses, plants were severely affected by deer browsing. One tree species, C. vitifolium found in the region but not in the reserve, was eliminated by a resident fungal facultative pathogen. Several practical conclusions for restoration can be made. The common nursery practice of soil sterilization may be detrimental because it eliminates beneficial mycorrhizal fungi; species not native to the site may not survive because they may not be adapted to the local pathogens; and herbivory can be severe depending on the landscape context of the restoration.     

Forest reclamation of fly ash deposit: a field study on appraisal of mycorrhizal inoculation

An extensive field trial was established on a fly ash deposit (1) to evaluate whether the inoculation with arbuscular mycorrhizal fungi (AMF) and/or ectomycorrhizal fungi (EcMF) improves growth and survival of 13 planted tree species and (2) to trace the inoculated mycorrhizal fungi in tree roots after one growing season. Molecular methods were applied to characterize AMF and EcMF entering the studied system (inocula, native soil, and roots of nursery seedlings). Biometric parameters and mortality of the trees were recorded and the presence of AMF and EcMF in sampled trees was determined both microscopically and genetically. Mycorrhizal inoculation did not improve survival or growth of any tree species. Most AMF‐host and all EcMF‐host seedlings were highly precolonized already from the nursery. An abundant and diverse AMF community was also found in the field soil. The AMF inoculum taxa partially overlapped with AMF in the native soil and in the precolonized roots. After one season, the only two inoculum‐unique AMF taxa were detected in host species non‐precolonized or only partially precolonized from the nursery. The components of EcMF inoculum were not detected in any sampled tree. After the season, the ectomycorrhizal hosts maintained most of their original EcMF taxa gathered in nursery, some tree species were additionally colonized by EcMF probably originating from the soil. Our results show considerable self‐restoration potential of nature on the target site. Mycorrhizal inoculation thus did not bring any conclusive advantage to the planted trees and seems superfluous for reclamation practice on the fly ash deposit.     

The good with the bad: when ecological restoration facilitates native and non‐native species

Organisms interact with each other along a spectrum ranging from competition to facilitation. A theme in restoration ecology is tipping the balance of these interactions to favor desired species and site conditions, exemplified by restoring fertile islands and their nurse plant effects to encourage plant recruitment. We tested the effectiveness of outplanting nursery‐grown native perennials and vertical mulching (placing dead plant material upright in soil) for stimulating annual plant recruitment in a disturbed Mojave Desert shrubland in Joshua Tree National Park, California, U.S.A. Over 9 years, differences in annual species richness and cover between interspaces and below outplants and vertical mulch varied among years, potentially via inter‐annual fluctuations in precipitation or maturation of restoration sites. In the ninth year, which was the wettest, both native and non‐native cover averaged 3× higher below outplants than in interspaces. Overall among years at the microsite scale, non‐native annual plants more consistently exploited environments provided by outplants and vertical mulch structures than did native annuals. However, these restoration structures were important for native annual diversity. At the 40‐m² plot scale, disturbed plots that received outplanting supported greater richness of native annual species than disturbed unrestored plots. By facilitating both non‐native and native plants, reestablishing fertile islands to restore dryland ecosystems is a conundrum for restoration. Treatments reducing non‐native plants may need to accompany fertile island restoration to tip the balance of facilitative plant interactions in favor of native species.     

Effect of different soil and clove treatments in the control of white rot of garlic

Soil solarisation was consistently efficacious in reducing inoculum density to undetectable levels in a field naturally‐infested with Sclerotium cepivorum. This treatment delayed epidemic onset of white rot of garlic 2–3 months as compared with the untreated control or the inoculation of planting furrows with Glomus intraradices. Furthermore, significant reductions of disease incidence and of the standardised AUDPC were also observed in solarised plots, resulting in quantitative and qualitative yield improvement. Similar effects were observed in plots planted with tebuconazole‐treated cloves, confirming previous results, whereas Trichoderma harzianum was ineffective as a biocontrol agent, when applied to planting furrows. The inoculation of plots with G. intraradices before planting, in three consecutive years, was neither effective for disease control nor on the development of garlic, although the root systems of garlic plants from all the experimental treatments were heavily mycorrhizal at harvest, indicating the presence of native arbuscular mycorrhizal propagules in the soil and their survival after soil solarisation.     

Restoration of plant communities in The Netherlands through the application of arbuscular mycorrhizal fungi

The aim of plant restoration projects is usually the recovery of the original native plant communities. However, in The Netherlands after restoration management practices have been completed, novel plant communities often develop and there is a return of only 50% to 60% of the desired plant species. A potential cause could be that the biological communities of the soil develop insufficiently to support a high diversity of plant species. This research project focused on the role of the soil biological community in controlling plant diversity. In particular, this project studied whether arbuscular mycorrhizal fungi a major component of the soil biological community, promote native plants. Field research indicated that arbuscular mycorrhizal fungi were present in the soil, even though colonization levels of arbuscules were low, 10% or less. The greatest abundance of arbuscular mycorrhizal fungi was observed at locations where the top soil was removed and where nutrient concentrations were reduced. The results of pot experiments showed that applied arbuscular mycorrhizal fungi significantly promoted the growth of native plant species. A cost benefit analysis revealed that the benefits of applying arbuscular mycorrhizal fungi exceeded the costs. This makes the application of arbuscular mycorrhizal fungi an attractive proposition.     

Seedling Establishment and Survival on Restored Campsites in Subalpine Forest

This study experimented with common restoration techniques (scarification, soil amendments, mulch, and seeding) on six closed wilderness campsites in subalpine forests in Oregon. Effectiveness in encouraging seedling establishment, growth, and survival was assessed every year for the first 7 years following treatment. Closure and restoration of the campsites increased the density of plants established from seed. Despite an original density of virtually zero, mean density of perennial plants was 55 plants/m² 7 years after closure. All the treatments, with the exception of the biodegradable mulch mat, increased plant density. Seven years after treatment, seeding had increased plant density 5‐fold, whereas scarification and soil amendments (organic matter, compost, and soil inoculum) had each increased density 3‐fold. The organic and compost amendments also had the positive benefit of increasing growth rates and shortening the time‐to‐reproductive maturity. Results suggest that restoration of the herbaceous cover on these campsites can occur rapidly using the techniques employed. All but one of the species we seeded established in substantial quantities and survived at densities exceeding their density in the naturally sparse herbaceous cover on these sites. Thirty‐six perennial species volunteered on these sites. The remaining challenge is reestablishment of the shrub species that comprise much of the ground cover in these forests. These species seldom establish from seed.     

Fungus diversity in revegetated paddocks compared with remnant woodland in a south‐eastern Australian agricultural landscape

Summary Despite the importance of fungi for restoration, their presence in revegetated sites has received little attention. We compared the diversity and composition of macrofungi (i.e. those that form fleshy mushrooms and truffles) in 12 sites where 3‐to‐6‐year‐old native trees and shrubs had been planted (woodland restoration sites), with that in six woodland remnants. All sites were within an agricultural landscape near Holbrook in New South Wales. Of 58 fungal genera recorded, 57% occurred in woodland restoration sites and 83% in nearby patches of remnant woodland. Of the genera found in restoration sites, 70% were also found in the woodland remnants. The dominance of early successional genera such as Lacceria and Scleroderma in restoration sites suggests windblown colonisation by fungi. The reduced proportion of hypogeous genera (truffles) that rely on mammal vectors, which are less likely to occur in the restoration sites, also supports the view that most fungi occurred in restoration through colonisation rather than being generated from soil spores. Greatest overall fungal diversity occurred in large remnants that had greater structural complexity. Across all sites, epigeous genera (mushrooms) were most common (78% of all taxa collected across 46 genera) and of the nutritional modes, mycorrhizal genera (forming symbiotic associations with plants) were the most common (206 collections, 71%, 25 genera). Both hypogeous and mycorrhizal fungi were positively associated with the diversity of native forb species (wildflowers), suggesting that lower fungal diversity in restoration sites is likely to be a consequence of long‐term agricultural practices, particularly fertilizer use.     

Relationship of seed source and arbuscular mycorrhizal fungi inoculum type to growth and colonization of big bluestem (Andropogon gerardii)

Big bluestem (Andropogon gerardii) is a key grass of tallgrass prairies and is commonly included in restoration projects. In many cases, it has been found to benefit significantly from arbuscular mycorrhizal (AM) fungi, however results have varied under non-sterile soil conditions. This study investigated the effects of two types of AM fungi inoculum (commercial and prairie) on growth and root colonization of big bluestem from five different seed sources grown in non-sterile soils. Seed sources were collected from five remnant prairies in the Tallgrass Prairie Peninsula located in the Midwestern United States. Growth of big bluestem and root length colonized by AM fungi was highly variable among seed source treatments. Overall, percentage of root length colonized by AM fungi was positively correlated with the total dry weight of plants, and plants that received inoculum generally grew better than those that did not receive inoculum. Inoculum treatment affected both big bluestem growth and percentage root length colonized and there was an interaction between seed source and inoculum treatment relative to colonization. Root colonization responses were not significantly different between the prairie and commercial inoculum types, although there was a significant response between plants that received additional inoculum as opposed to no additional inoculum. Seed sources from Ohio and Illinois had the highest biomasses and greatest percentage of root length colonized while plants from Wisconsin and Missouri grew poorly and had low root colonization. These results demonstrate the importance of considering both seed source and inoculum type before the incorporation of AM inoculum to prairie restoration projects.     

Assessing the residual effects of Carpobrotus edulis invasion, implications for restoration

We examined whether the residual effects on soil caused by the invasion of Carpobrotus edulis, common iceplant, would inhibit the reestablishment of a native plant species. Carpobrotus edulis interacts both directly by suppressing the growth and establishment of other plants and indirectly by altering soil chemistry. We tested whether the residual effects of C. edulis resulted in lowered germination, survival, growth, and reproduction of Gilia millefoliata, a rare dune annual. We compared G. millefoliata planted in plots previously occupied by C. edulis to G. millefoliata planted in plots that previously had native vegetation. Each plot received three treatments: seed, transplant, and unplanted, and were censused every three weeks until senescence. Carpobrotus edulis had strong negative effects on the germination, survival, growth, and reproduction of G. millefoliata. C. edulis lowers soil pH and increases organic content due to the recalcitrance of tissue to decomposition, which may have evolved as a mechanism to facilitate recolonization and invasion.     

Establishment of arbuscular mycorrhizal plants originating from xerothermic grasslands on heavy metal rich industrial wastes–new solution for waste revegetation

Industrial waste substrata, rich in heavy metals, are poorly suited for plant growth. Efforts are made to establish an appropriate plant cover to reduce erosion and further contamination. Grasses are the usual solution, as they grow fast, thrive on poor substrata and have well-developed root systems. Some of them are also highly dependent on mycorrhizal symbiosis that supports their growth especially on poor and polluted soils. However, the commercially available grasses often meet a lack of well established mycorrhiza on the site and the introduced plant populations dramatically decrease with time, despite large financial input including covering the substratum with soil and intensive watering. The aim of this paper was to select proper plants together with mycorrhizal fungi that could accelerate the establishment of the vegetation and improve its diversity under these extreme conditions, minimizing the financial costs of the reclamation (no use of soil layering and watering). The experiments were carried out under field and laboratory conditions. The plant seeds used originated from dry calcareous grasslands. The seeds were germinated under field conditions or in pots filled with soil supplemented with substratum from the industrial wastes. The seedlings were inoculated with AM fungi and introduced on the field plots a few weeks after germination. The inoculum consisted of either crude inoculum harvested from the dry calcareous grasslands or strains originating from polluted areas. Plants colonized by mycorrhizal fungi established well in the experimental plots. The results suggest that inocula from dry calcareous grasslands are potentially useful in revegetation of industrial wastes. Although in several cases the photosynthetic activity of plants was lower than at the natural sites, almost all plants survived and formed seeds. In all experiments the plant vitality was estimated on the basis of chlorophyll a fluorescence and was useful to show differences between waste substrata, inocula and coexisting plant species. The interactions between mycorrhizal and non-mycorrhizal plants were studied under greenhouse conditions and at least no negative effect of this coexistence was found.     

Responses of Pioneer and Later‐Successional Plant Assemblages to Created Microtopographic Variation and Soil Treatments in Riparian Forest Restoration

Riparian forest restoration generally involves introduction of later‐successional tree species, but poor species suitability to severely altered or degraded site conditions results in high mortality and poor community development. Additionally, while microtopographic heterogeneity plays a crucial role in the development of natural riparian forests, little is known regarding effects of restored or created microtopography on the development of introduced plant communities. The objective of this study was to determine the influence of created microtopography and soil treatments on early development of introduced pioneer and later‐successional plant communities in riparian forest restoration. Ridges, flats, and a mound‐and‐pool complex were created, and pioneer and later‐successional tree assemblages were planted within plots in each of these three microtopographic positions. Straw‐based erosion control mats were placed on half the plots as a source of mulch. After two growing seasons, growth and survival of the pioneer assemblage were equal among microtopographic positions, but survival of the later‐successional assemblage was significantly higher on ridges (59%) than on mounds and pools (22%) and flats (26%). A suitability index indicated that performance of the later‐successional assemblage on ridges was higher than that of the pioneer assemblage for all microtopographic positions. Flood duration explained much of the variation in plant assemblage survival, and erosion control mats had little influence on seedling survival. Restoring microtopographic features has the potential to enhance species survival and promote community development. Microtopographic restoration may be as important in riparian forest restoration as proper species selection and hydrologic reestablishment, especially at severely disturbed sites.     

Arbuscular Mycorrhizal Assemblages in Native Plant Roots Change in the Presence of Invasive Exotic Grasses

Plant invasions have the potential to significantly alter soil microbial communities, given their often considerable aboveground effects. We examined how plant invasions altered the arbuscular mycorrhizal fungi of native plant roots in a grassland site in California and one in Utah. In the California site, we used experimentally created plant communities composed of exotic (Avena barbata, Bromus hordeaceus) and native (Nassella pulchra, Lupinus bicolor) monocultures and mixtures. In the Utah semi-arid grassland, we took advantage of invasion by Bromus tectorum into long-term plots dominated by either of two native grasses, Hilaria jamesii or Stipa hymenoides. Arbuscular mycorrhizal fungi colonizing roots were characterized with PCR amplification of the ITS region, cloning, and sequencing. We saw a significant effect of the presence of exotic grasses on the diversity of mycorrhizal fungi colonizing native plant roots. In the three native grasses, richness of mycorrhizal fungi decreased; in the native forb at the California site, the number of fungal RFLP patterns increased in the presence of exotics. The exotic grasses also caused the composition of the mycorrhizal community in native roots to shift dramatically both in California, with turnover of Glomus spp., and Utah, with replacement of Glomus spp. by apparently non-mycorrhizal fungi. Invading plants may be able to influence the network of mycorrhizal fungi in soil that is available to natives through either earlier root activity or differential carbon provision compared to natives. Alteration of the soil microbial community by plant invasion can provide a mechanism for both successful invasion and the resulting effects of invaders on the ecosystem.     

Factors governing survival of black willow (Salix nigra) cuttings in a streambank restoration project

A field study was conducted at Little Topashaw Creek in northern Mississippi, aimed at expanding the limited database on the survivorship of Salix nigra (black willow) cuttings planted on riparian restoration sites. We tested the hypothesis that sediment moisture availability (deficit, excess) as mediated by sediment texture and depth to the prevailing water table is a major factor governing black willow survival during the initial stage of establishment following transplanting. Replicated plots were established across elevational gradients and a range of soil texture. Each plot contained 16 planted cuttings (2.5 cm diameter × 2.5 m length). Plot depth to water table, soil texture, and soil redox potential were measured. Plant gas exchange, leaf chlorophyll content, growth, and survival were monitored periodically over two growing seasons. Survival was best at low elevation compared to cuttings planted at mid- and high elevations. Poor survival and growth were noted for cuttings that encountered sediment moisture deficits in plots with coarse texture while the best cutting survival was recorded for intermediate sand content plots. Results indicated that plot location on the bank and soil texture are two important factors that influence riverbank restoration success. Therefore, any riparian restoration plan should include careful assessment of these factors prior to undertaking such efforts.     

Growth and survival of seedlings of native plants in an impoverished and highly disturbed soil following inoculation with arbuscular mycorrhizal fungi

We investigated whether arbuscular mycorrhizas influenced growth and survival of seedlings in an extremely impoverished and highly disturbed soil. Seedlings of four plants species native to the site were either inoculated with native sporocarpic arbuscular mycorrhizal (AM) fungi or fertilised prior to transplanting, and followed over 86 weeks at the site. One treatment was also irrigated with N-rich leachate from the site. In a laboratory experiment, seedlings were fertilised with excess P for 6 weeks, and location of the P store determined. Growth and survival of AM and fertilised seedlings were similar at the site. Inoculated mycorrhizal fungi and roots appeared to extend into the surrounding soil together. P concentration in leaves of all plants was extremely low. Irrigation with leachate increased growth of seedlings. In the laboratory experiment, significantly more P was stored in roots than shoots. We suggest that successful revegetation of extremely disturbed and impoverished sites requires selection of mycorrhizal fungi and plants to suit the edaphic conditions and methods of out-planting.     

桑及菌根桑在库区消落带的生态重建功能及应用潜力

三峡工程在提供丰富水电资源造福人类的同时,也引发了一些生态环境问题,对库区环境、生物、气候以及人们的生活都产生了不同程度的影响。桑树休眠和生长发育节律与库区水体涨落规律的反向偶联,桑的菌根结构在改善根际土质量,促进桑树水分和养分吸收,增强桑树对盐碱、干旱、重金属的耐受性,提高幼苗的存活率,促进桑苗生长,促进植物群落正向演替等生态过程中发挥着重要的作用。分析了三峡库区消落带周期性水淹的生态特征和岸生植物生态恢复障碍,综述了桑及菌根桑在消落带的生态特性和应用潜力,最后提出了菌根桑生物技术的应用所面临的新课题和挑战。