丛枝菌根真菌根内菌丝碱性磷酸酶活性与菌根共生效应的研究

试验研究 3种丛枝菌根真菌根内菌丝碱性磷酸酶活性与菌根共生效应的结果表明 ,3种丛枝菌根真菌对宿主植物的效应不同 ,与接种G .spp处理和未接种对照相比 ,接种G .m和G .i处理显著增加玉米地上部和根系干物质量、P浓度和吸P量 ,但后两者间无显著差异 ;而接种G .spp处理与对照无显著差异。播种后 35d时接种G .m和G .i处理根内菌丝碱性磷酸酶活性显著高于接种G .spp处理 ,而前二者间无显著差异 ,且随生长时间的变化趋势相似 ,35d时酶活性最高 ,35～ 5 0d呈迅速下降趋势 ,至 70d时酶活性仍下降且趋于平缓。G .spp酶活性则一直处于较低水平 ,随生长时间的延长略有起伏。即接种不同丛枝菌根真菌时 ,根内菌丝碱性磷酸酶活性高的菌根真菌对玉米生长促进作用较大 ,可提高玉米P营养状况 ;反之则对玉米生长和P营养状况无明显促进作用 ,且与对照无显著差异。出苗后 35d时根内菌丝碱性磷酸酶活性是预测丛枝菌根真菌对玉米生长效应的有效生理指标之一。     

丛枝菌根对三叶草根际磷酸酶活性的影响

以三叶草为材料,利用三室隔网培养方法,探讨了取自肥料长期定位试验中多年施用与不施用有机肥的田间小区土壤上,接种菌根菌（G.mosseae）对根际土壤酸性和碱性磷酸酶活性的影响。植物生长9周后,收获测定菌丝生长室土壤酸性磷酸酶和碱性磷酸酶活性,并对磷酸酶产生位点进行细胞化学定位。结果表明,接种丛技菌根菌对根际土壤酸性和碱性磷酸酶活性均有增强作用,但作用程度在有机服小区土壤上要大于无机肥小区土壤。根际土壤酸性磷酸酶原位化学定位结果表明,菌丝周围有明显的酸性磷酸酶的反应产物,说明报外丛枝菌根菌丝能直接向外分泌磷酸酶。     

Nitrogen capture by grapevine roots and arbuscular mycorrhizal fungi from legume cover-crop residues under low rates of mineral fertilization

The influence of mineral fertilization on root uptake and arbuscular mycorrhizal fungi-mediated ¹⁵N capture from labeled legume (Medicago polymorpha) residue was examined in winegrapes (Vitis vinifera) in the greenhouse, to evaluate compatibility of fertilization with incorporation of cover-crop residue in winegrape production. Plants grown in marginal vineyard soil were either fertilized with 0.25× Hoagland’s solution or not. This low fertilization rate represents the deficit management approach typical of winegrape production. Access to residue in a separate compartment was controlled to allow mycorrhizal roots (roots + hyphae), hyphae (hyphae-intact), or neither (hyphae-rotated) to proliferate in the residue by means of mesh core treatments. Leaves were weekly analyzed for ¹⁵N. On day 42, plants were analyzed for ¹⁵N and biomass; roots were examined for intraradical colonization; and soils were analyzed for ¹⁵N, inorganic N, Olsen-P, X-K, and extraradical colonization. As expected, extraradical colonization of soil outside the cores was unaffected by mesh core treatment, while that inside the cores varied significantly. ¹⁵N atom% excess was highest in leaves of roots + hyphae. In comparison, leaf ¹⁵N atom% excess in hyphae-intact was consistently intermediate between roots + hyphae and hyphae-rotated, the latter of which remained unchanged over time. Fertilization stimulated host and fungal growth, based on higher biomass and intraradical colonization of fertilized plants. Fertilization did not affect hyphal or root proliferation in residue but did lower %N derived from residue in leaves and stems by 50%. Our results suggest that even low fertilization rates decrease grapevine N uptake from legume crop residue by both extraradical hyphae and roots.     

不同AM菌根菌分泌的磷酸酶对根际土壤有机磷的影响

以三叶草为材料,利用3室隔网培养方法,研究了4种AM菌根菌侵染三叶草后对根际土壤酸性和碱性磷酸酶活性以及菌丝酶活性对土壤有机P的影响。结果表明,接种AM菌根菌 (9周) 对根际土壤酸性和碱性磷酸酶活性均有增强作用,但作用强度主要取决于菌丝在土壤中的生长状况,Glomus属菌根菌在整个菌丝室 (0~6cm) 都影响土壤磷酸酶的活性,其活性在整个菌丝室中都比Gigaspora的高。同一属不同种的根际土壤磷酸酶活性差异不大。AM菌根根际土壤磷酸酶对土壤有机P的降解有很强的促进作用。     

Spatial distribution of phosphatase activity associated with ectomycorrhizal plants is related to soil type

Several ectomycorrhizal fungi, including Hebeloma cylindrosporum, actively release large quantities of phosphatase enzymes into their growth medium. We fractionated the phosphatase activity of the ectomycorrhizal association between H. cylindrosporum and its host plant, Pinus pinaster, with the aim to quantify its spatial and temporal variation in response to contrasting soil phosphorus conditions. Seedlings were grown in mini-rhizoboxes and the phosphomonoesterase activity of rhizosphere soil, released by roots, surface-bound to roots or mycelium was determined spectrophotometrically with the p-nitrophenyl phosphate method or microscopically with the ELF-method as a function of culture time. We showed that acid phosphatase activity of the soil and the root increased with mycorrhizal association. We also observed that the phosphatase activity associated with ectomycorrhizal plants was related to soil type. All phosphatase fractions decreased over culture time, except the proportion of hyphae exhibiting phosphatase activity in the extramatrical mycelium, which increased over time. The specific fractions of phosphatase activity associated with the mycorrhizal plants were clearly related to the soil phosphorus type and content. Soils showed an increase in acid phosphomonoesterase activity with mycorrhizal association, supporting a role for this enzyme in the degradation of soil bound phosphorus. The gradually increasing proportion of hyphae in the extramatrical mycelium exhibiting alkaline phosphatase activity, particularly under low phosphorus conditions, indicates an induction of alkaline phosphatase activity by phosphorus limitation.     

Hyphal translocation and uptake of sulfur by vesicular-arbuscular mycorrhizae of onion

Translocation of S by external hyphae of Glomus fascieulatus, a vesicular-arbuscular (VA) mycorrhizal fungus, was demonstrated. When tracers were injected 8 cm from onion roots in soil chambers, both ³⁵S and ³²P appeared in roots of mycorrhizal plants. Neither radionuclide was present in non-mycorrhizal plants.In a second soil-chamber experiment, mycorrhizal onions took up more ³⁵S per unit dry weight than non-mycorrhizal controls when ³⁵S was injected into soil chambers in a region 3–6 cm from roots. Severing of external hyphae between the application area and the roots reduced the concentration of ³⁵S in tops of mycorrhizal plants but not in roots. Volatile ³⁵S per unit dry weight collected from all plants in each treatment was highest in the mycorrhizal-hyphae intact treatment, and higher in the mycorrhizal-hyphae severed treatment than the non-mycorrhizal treatment. Movement of ³⁵S in soil from the area of application to roots was similar for all treatments.Increased uptake of S from soil by VA mycorrhizal plants can result from hyphal translocation of S to infected roots by external mycorrhizal hyphae.     

Phosphatase activity and cytokinin content in cowpeas (Vigna unguiculata) inoculated with a vesicular-arbuscular mycorrhizal fungus

We examined the effect of a vesicular-arbuscular mycorrhizal (VAM) fungus Glomus pallidum Hall on the phosphatase activity and cytokinin concentration in cowpea [Vigna unguiculata (L.) Walp] roots at successive stages of plant growth. Both acid and alkaline phosphatase activity were significantly (P=0.05) higher in mycorrhizal than in non-mycorrhizal roots 30 days after inoculation. Similarly, the cytokinin content was significantly increased in mycorrhizal roots compared to non-mycorrhizal roots. Our study suggests that these biochemical changes may improve the growth of mycorrhizal cowpea plants.     

A mycorrhizal fungus grows on biochar and captures phosphorus from its surfaces

Biochar application to soils has potential to simultaneously improve soil fertility and store carbon to aid climate change mitigation. While many studies have shown positive effects on plant yields, much less is known about the synergies between biochar and plant growth promoting microbes, such as mycorrhizal fungi. We present the first evidence that arbuscular mycorrhizal (AM) fungi can use biochar as a physical growth matrix and nutrient source. We used monoxenic cultures of the AM fungus Rhizophagus irregularis in symbiosis with carrot roots. Using scanning electron microscopy we observed that AM fungal hyphae grow on and into two contrasting types of biochar particles, strongly attaching to inner and outer surfaces. Loading a nutrient-poor biochar surface with nutrients stimulated hyphal colonization. We labeled biochar surfaces with ³³P radiotracer and found that hyphal contact to the biochar surfaces permitted uptake of ³³P and its subsequent translocation to the associated host roots. Direct access of fungal hyphae to biochar surfaces resulted in six times more ³³P translocation to the host roots than in systems where a mesh prevented hyphal contact with the biochar.We conclude that AM fungal hyphae access microsites within biochar, that are too small for most plant roots to enter (<10 μm), and can hence mediate plant phosphorus uptake from the biochar. Thus, combined management of biochar and AM fungi could contribute to sustainable soil and climate management by providing both a carbon-stable nutrient reservoir and a symbiont that facilitates nutrient uptake from it.     

Palatability of microfungi to soil arthropods in relation to the functioning of arbuscular mycorrhizae

We investigated the feeding preferences of six species of mites and collembolans for three fungi commonly associated with roots of Acer saccharum (Glomus macrocarpum, Alternaria alternata and Trichoderma harzianum), from a maple-forest soil in southern Ontario, Canada. Experiments were also conducted in vitro to determine animal feeding responses to (1) increasing quantities of hyphal biomass, (2) the presence of root vs. litter fungal substrates, and (3) hyphae of different widths of Glomus macrocarpum. The results indicate that arthropods prefer to graze in the litter region rather than in the deeper soil layers. Under ideal moisture/temperature conditions, animals are forced to the lower regions by interspecific interactions. They prefer to graze on hyphae of conidial fungi rather than on those of arbuscular mycorrhizal fungi. When arbuscular mycorrhizal fungal hyphae are grazed, there is a clear preference for the narrower hyphae, which are those further away from the root. The thicker hyphal segments, commonly found connecting absorptive hyphal fans to roots, were less preferred. These data are not consistent with the hypothesis that microarthropods are detrimental to arbuscular mycorrhizal associations, and suggest that Glomalean fungi may have evolved mechanisms to deter grazing by microarthropods.     

Shoot‐produced,light‐dependent factors are partially involved in the expression of the arbuscular mycorrhizal (AM) status of AM host and non‐host plants

Arbuscular mycorrhizal (AM) colonization and hyphal attachment to the roots of a host plant, bean, and a non‐host plant, lupin, were compared when grown either with light or in the dark with the AM fungus Glomus mosseae. When grown with light, bean roots were heavily colonized whereas lupin roots showed no signs of colonization, no formation of appressoria and only scarce hyphal attachment to the roots. In contrast to roots of plants grown with light, to living roots of beans and lupins grown in the dark many hyphae were attached and appressoria were formed. The role of shoot produced, light‐dependent factors in the expression of the AM mycotrophic status of AM host and non‐host plants is discussed.<?show $6#>     

The contribution from hyphae, roots and organic carbon constituents to the aggregation of a sandy loam under long-term clover-based and grass pastures

Water-stable macro-aggregate size fractions (>2.0 mm, 1.0–2.0 mm, 0.5–1.0 mm and 0.25–0.5 mm) and non-aggregated soil from a sandy loam under long-term clover-based pasture and from grass pasture were analysed to determine the role of acid- and water-extractable carbohydrate C, total hyphal length, microbial biomass, organic C and total and mycorrhizal root length in stabilization of the aggregates. Aggregates were examined by scanning electron microscopy (SEM) and the particle-size distribution of the size fractions was also determined. Macro-aggregation increased under grass, relative to clover-based pasture; however, the properties of the aggregate fractions measured did not reflect this difference. Microbial-biomass C, extractable-carbohydrate C, hyphal length, total and mycorrhizal root length and organic C content of the soils were poorly correlated with macro-aggregation. Within the aggregates, the proportion of 250–1000-km sand was smaller and clay, silt and fine sand (20–250 μm) were greater relative to non-aggregated soil, suggesting that the >250-μm sand in the non-aggregated soil limited the stabilization of macro-aggregates. Under SEM, no enmeshment of aggregates by hyphae and roots was apparent. Although 50–160 m hyphae g^?1 soil was found within the aggregates, calculations showed that on average only 5 to 13 lengths of hyphae were associated with each 250-μm cube of soil within the aggregates, and suggested little potential to stabilize the aggregates by enmeshing. On average, all >2.0-mm aggregates contained less than 3.6 mm of roots and less than 50% by weight of <2.0-mm aggregates contained a single length of root. The findings cast doubt about the role of hyphae and fine roots in the stabilization of macro-aggregates through an enmeshing mechanism in sandy soils.     

Organic and inorganic soil phosphates and acid phosphatase activity in the rhizosphere of 80-year-old Norway spruce [Picea abies (L.) Karst.] trees

Summary Inorganic and organic phosphates (P) were measured in bulk soil, rhizosphere soil and mycorrhizal rhizoplane soil of Norway spruce. Various methods of P extraction and estimation were compared. In addition, acid phosphatase activity and mycelial hyphae length were determined. In soil solutions from various locations, about 50% (range 35%–65%) of the total P was present as organic P. Compared to the bulk soil, the concentrations of readily hydrolysable organic P were lower in the rhizosphere soil and in the rhizoplane soil; this difference was particularly marked in the humus layer. In contrast, the concentrations of inorganic P either remained unaffected or increased. A 2- to 2.5-fold increase was found in the activity of acid phosphatase in the rhizoplane soil in comparison to the bulk soil. There was a positive correlation (r = 0.83^***) between phosphatase activity and the length of mycelial hyphae. The results stress the role of organic P and of acid phosphatase in the rhizosphere in the P uptake by mycorrhizal roots of spruce trees grown on acid soils.     

丛枝菌根(AM)真菌与共生植物物质交换研究进展

丛枝菌根(Arbuscular Mycorrhizal,AM)真菌能与约 80% 的陆生植物形成共生关系,植、 菌间矿质养分、 碳水化合物的物质交换是自然界物质循环的重要内容。目前,AM 真菌促进共生植物矿质养分吸收的研究相对较多。研究表明, AM 真菌可通过根外菌丝更小的吸收直径,加强矿质养分的空间有效性; 通过释放有机酸、 土壤酶,活化土壤中被固定的矿质养分; 通过根外菌丝上较低 Km 值的矿质养分转运蛋白,保证养分从土壤至根外菌丝的转运效率; 通过矿质养分在菌丝内运输形式的改变,增强养分的运输速率; 通过诱导共生植物矿质养分转运蛋白表达,提高植、 菌间养分的转运效率。相较于 AM 真菌促进共生植物养分吸收,植物反馈真菌碳水化合物的研究相对较少。鉴于 AM 真菌与植物共生关系在生态系统中的重要作用,明晰植、 菌间矿质养分和碳水化合物交换的具体场所(丛枝、 根内菌丝、 根外菌丝)、 具体形式(离子、 聚合物、 氨基酸、 蔗糖、 单糖)、 具体过程(主动运输)具有重要科学意义。本文对 AM 真菌与共生植物物质交换的丛枝、 菌丝双膜结构,氮(N)、 磷(P)、 糖等物质交换的具体形式以及跨双膜、 耗能量、 互耦连的物质交换过程进行综述,并从物质交换的场所、 形式、 过程三个方面提出了植、 菌物质交换的研究方向。     

玉米丛枝菌根真菌根外菌丝表面定殖细菌解磷功能鉴定

【目的】在田间原位条件下研究丛枝菌根(Arbuscular mycorrhizal, AM)真菌根外菌丝表面有无解磷细菌定殖,并对存在的解磷细菌的种类进行鉴定,对其活化有机磷的能力进行检测,从而为更好地认识菌丝际土壤有机磷的周转和磷的生物地球化学循环过程提供依据。【方法】利用河北省曲周县中国农业大学实验站的玉米长期定位试验,采用田间埋膜方式从玉米根系周围收集AM真菌的根外菌丝,用蒙金娜有机磷固体培养基筛选菌丝表面具有矿化植酸钙能力的细菌,对筛选出的细菌进行分离、 培养,然后提取细菌DNA,通过16S rDNA测序分析来确定解磷细菌的种类。分离鉴定的菌株先用蒙金娜有机磷固体培养基通过测定菌落直径(d)及溶磷圈直径(D)初步鉴定其活化植酸钙的能力,再用无菌的蒙金娜有机磷液体培养基确定每株解磷细菌矿化植酸磷的能力,并对溶液的pH进行测定,每个菌株重复3次。最后采用两室隔网根盒将分离纯化的解磷细菌回接至AM真菌根外菌丝,鉴定回接成功率,确定分离出的解磷细菌能否成功定殖于菌丝表面。【结果】从AM真菌根外菌丝表面分离得到了29株具有活化有机磷能力的细菌,分属于芽胞杆菌、 假单胞菌、 沙雷氏菌、 葡萄球菌和肠杆菌5个不同的属。通过有机磷液体培养进一步检测这些菌株活化植酸磷的能力,发现它们对植酸磷的矿化率为1.9%~21.9%。其中假单胞菌属细菌的解磷能力相对较强,对植酸磷的矿化率达14%以上,液体培养基的pH值下降2~4个单位。将分离纯化的细菌回接至两室隔网根盒的菌丝室,培养30 d后,从菌丝表面再次检测到除假单胞菌属外的芽胞杆菌属(Bacillus)、 沙雷氏菌属(Serratia)、 葡萄球菌属(Staphylococcus)和肠杆菌属(Enterobacter)细菌,另外还检测到贪铜菌属(Cupriavidus)细菌。【结论】在田间原位条件下,与玉米共生的AM真菌的根外菌丝表面有多种解磷细菌定殖,它们活化有机磷能力存在差异,其中以假单胞菌属细菌的解磷能力相对较强。     

Effects of nitrogen feeding for extraradical mycelium of Rhizophagus irregularis maize symbiosis incorporated with phosphorus availability

In terrestrial ecosystems, plants are frequently in symbiosis with arbuscular mycorrhizal fungi (AMF) with mineral nutrients and photosynthesis carbon exchanges in between. This research sought to identify the effects of phosphorus (P) levels on the nitrogen (N) uptake via extraradical mycelium (ERM) and the mycorrhizal growth response (MGR) of maize plants within the AMF symbiosis. Pots were separated into root compartments and hyphae compartments (HCs) with two layers of a 30‐μm mesh membrane and an air gap in between, where only hyphae could pass through, to avoid both N diffusion and root growth effects. Maize plants were inoculated with Rhizophagus irregularis with different N fertilization in HCs under two different P fertilization levels. Our results indicated that a strong increase in MGR with low‐P fertilization. The same tendency was not observed with high‐P fertilization, although both had a large increase in P concentration as a potential source of growth in shoot tissue of mycorrhizal plants. Substantial effects (10.5% more N) were observed in the case of high‐P availability for the host plants from ERM fed with N, whereas under low‐P conditions ERM may prioritize P uptake rather than N uptake. The AM fungi increase the uptake of N and P, which are most limiting in the soil with fewer forces from soil resources. In addition, there was still more P accumulated than N due to the high N for ERM with high‐P supply. Low N in HCs corresponded with a lower colonization rate in roots but with high hyphae density in HCs; this result suggest that N and P availability might change the ratio of extraradical to intraradical hyphae length.     

Effects of fungicides on arbuscular mycorrhizal fungi: differential responses in alkaline phosphatase activity of external and internal hyphae

 The effect of four fungicides on alkaline phosphatase (ALP) activity in internal and external hyphae of an arbuscular mycorrhizal (AM) fungus was examined. Four-week-old plants were treated with an aqueous solution of the fungicides and then harvested 3 days later. Fungicides were applied at a low and a high level corresponding to 1 and 100 times the recommended field application dose. The fungicides were the two abundantly used sterol inhibitors, fenpropimorph and propiconazole, as well as a commercial mixture of them. Benomyl served as a positive control, as this fungicide is known for its deleterious effect on AM fungi. At harvest, roots and hyphae extracted from the soil were stained for ALP activity. Benomyl inhibited fungal ALP activity of both internal and external hyphae at the low application level (1 μg g^–1 soil) corresponding to the recommended field dose. Fenpropimorph had an intermediate effect, inhibiting both internal and external hyphae but only at the high application level (125 μg g^–1 soil). Propiconazole decreased the activity of the external hyphae at the low application level (0.21 μg g^–1 soil) but did not affect the internal activity at any application level. The effect of Tilt Top was similar to that of fenpropimorph. The results showed that the external hyphae were more sensitive than internal hyphae to application of fungicides. Received: 26 May 1999     

The effect of ground cover or initial organic carbon on soil fungi, aggregation, moisture and organic carbon in one season with oat (Avena sativa) plots

The unique capacity of fungi to efficiently sequester carbon in aerobic conditions, presents a way to maximize OC gain in agricultural systems. Oat (Avena sativa) was planted in the temperate climate of southern Ontario, Canada to study factors affecting soil organic carbon (OC). The plots varied with initial OC from 25 to 68 g kg⁻¹ or with ground cover of differing decomposability (alfalfa (Medicago sativa) growing from seed, dried oat straw, dried hay and compost) on high OC soil (60–70 g kg⁻¹). The soil was analysed for correlation of changes in soil aggregation, moisture, OC, fungal hyphal number and length and distribution of organic matter by mass and OC in density fractions within the growing season. At harvest, soil OC and moisture were increased only in plots with ground cover. Total hyphal length was not significantly different with ground cover treatment at harvest, and did not correlate with soil aggregation and soil OC. However, the number of hyphae with >5 μm diameter (primarily mycorrhizal fungi) correlated with % OC in ground cover plots while the number of hyphae <5 μm (primarily saprophytic fungi) correlated with % OC without ground cover in the gradient of initial soil OC. Mycorrhizal hyphae may be important to the increases in soil OC from surface treatment, although there was no treatment effect of mycorrhizal occurrence on the oat roots. This microcosm study, with growing and dried ground cover, suggests surface management may a simple and inexpensive means in agriculture to increase soil moisture and OC that benefits farmers as well as reducing atmospheric CO₂.     

Arbuscular mycorrhizal fungal hyphae enhance transport of the allelochemical juglone in the field

Allelopathy is a biological phenomenon where plants have harmful effects on growth of surrounding plants through the production of chemical substances. Here we focus on allelochemical processes which operate belowground, can influence plant interactions and therefore potentially affect plant community structure. Soil hyphae of arbuscular mycorrhizal fungi (AMF) may enhance transport processes in the soil matrix by providing direct connections between plants facilitating infochemical exchange.In a two-component field study we showed that soil hyphae likely play a crucial role in movement of allelochemicals in natural soils and greatly expand bioactive zones by providing effective transport pathways for chemical compounds. First, we tested the effects of Juglans regia leaf litter extract addition in intact or disrupted hyphal networks and simultaneously determined growth reducing effects on sensitive Lycopersicon lycopersicum plants. Second, we analyzed the effect of juglone on tomato by directly adding leaf litter. In both approaches we found an increase of juglone transport if a hyphal network was present, resulting in reduced growth of target plants.Our results, together with previous work, add to the body of evidence for hyphae of soil fungi playing an important role in the transfer of allelochemicals and effectively acting as transport highways in the field. We suggest that hyphal connections, mostly formed by AMF, increase the effectiveness of allelochemicals in natural systems and can play a crucial role in chemical interaction processes in the soil.     

The role of the external mycelium in early colonization for three arbuscular mycorrhizal fungal species with different colonization strategies

Arbuscular mycorrhizal fungi (AMF) differ in their rate and extent of colonization of both plant roots and soil but the mechanism responsible for these differences is unclear. We compared the external mycelium of three AMF isolates (Glomus intraradices, Glomus etunicatum and Gigaspora gigantea) during early colonization of plant roots. We investigated whether an AMF with the most rapid colonization would have higher numbers of infective structures (i.e., infection hyphae and contact points), an AMF with extensive root colonization would have more infection units, and (3) AMF with extensive soil colonization would have large numbers of all external features (including absorptive hyphae, runner hyphae and hyphal bridges). Using specially designed soil and root observation chambers, we followed the development of the external mycelium for 7 weeks. We found that rapid colonization rate was due, in part, to the presence of more infective structures, in particular more infection hyphae and root contact points. Second, the extensive root colonizer had more, larger infection units. Third, data did not support the hypothesis that the extensive soil colonizer had more external structures. These results show that differences in the architecture of the external mycelium are responsible, in part, for variation in the colonization strategy of AMF.     

Fungal hyphal dynamics in a western oregon douglas-fir stand

Total length and biomass of fungal mycelium in the soil of a young stand of second-growth Douglas-fir in the central Oregon Coast Range were estimated over 27 months with the agar-film technique. Mycelial mass was at maximum in fall and spring and significantly lower in summer. Melanized hyphae dominated other colors, averaging 66% of monthly litter and 73.7% of soil hyphal weight. The mycorrhizal fungus Cenococcum geophilum Fr. had significantly larger average diameter than other hyphae and contributed from 1.2 to 64.8% of the monthly hyphal volume. Multiple regression analyses with temperature, moisture, and litterfall produced no adequate predictive equations for monthly fungal biomass. Large biomass fluctuations over short periods necessitate frequent sampling and long-term study to fully assess the importance of fungal hyphae in ecosystems.