Wood Baits Research Articles

Electrical integrity and week-long oscillation in fungal mycelia

The electrical potential of the mycelia of a cord-forming wood decay fungus, Pholiota brunnescens, was monitored for over 100 days on a plain agar plate during the colonization onto a wood bait. Causality analyses of the electrical potential at different locations of the mycelium revealed a clear and stable causal relationship with the directional flow of the electrical potential from the hyphae at the bait location to other parts of the mycelium. However, this causality disappeared after 60 days of incubation, coinciding with the onset of slow electrical oscillation at the bait location, which occurred over one week per oscillation cycle. We speculated that the hyphae that initially colonized the bait may act as a temporary activity center, which generates electrical signals to other parts of the mycelium, thereby facilitating the colonization of the entire mycelial body to the bait. The week-long electrical oscillation represents the longest oscillation period ever recorded in fungi and warrants further investigation to elucidate its function and stability in response to environmental stimuli.

Hyphal connection increases net resource utilization of saprotrophic fungal mycelia by improving local performance: A case study of the cord-forming basidiomycete, Phanerochaete velutina

To identify the functional advantages of hyphal connections in fungal mycelial networks, we evaluated the wood decaying abilities of the mycelia of a saprotrophic basidiomycete, Phanerochaete velutina, in soil dishes with wood baits. The dishes were surrounded by water, allowing the mycelia to access water. Dishes with two or three baits were placed adjacent to or distant from each other, representing the ease of creating hyphal bridges between the two dishes. After 8 months of incubation, the weight loss of the wood bait was significantly larger in the adjacent pairs of dishes compared to the distant pairs. Mycelia in the adjacent dishes had higher chances to access the water and thus increase water content of the wood, which was the primary factor related to wood weight loss. These results suggest that hyphal connections increase decay ability of P. velutina possibly due to water transfer across the mycelial network.

Bark and ambrosia beetles on native and transplanted dead wood along an altitudinal tropical forest gradient

AbstractGlobal warming is expected to shift the distribution ranges of many species towards higher latitudes and altitudes. This will rewire plant‐herbivore food webs as new combinations of herbivore species encounter novel host plants. We investigated the effects of a simulated altitudinal shift in an herbivore‐host community of bark and ambrosia beetles on fig trees in a tropical mountain forest on Mt. Wilhelm, Papua New Guinea. We reared beetles from wood baits cut from five local Ficus species in their natural altitudinal ranges, between 200 and 1700 m a. s. l. Further, we transplanted baits from three of these tree species 500 m below the limits of their natural distribution range, to simulate a mean temperature increase of 2.7°C. Beetle species richness declined, and their species composition changed with increasing elevation. Furthermore, while altitude explained a large proportion of variance in beetle composition, host tree species was more important for bark beetles than ambrosia beetles. Beetle communities that assembled on the transplanted baits were similar in diversity and host specificity to those on the fig trees native to the same elevation, but also contained a number of unique species. Overall, these results indicate that saproxylic beetles in this tropical forest are highly resilient and flexible to the potential effects of climate change.Abstract in Česky is available with online material.

Preference of Subterranean Termites among Community Timber Species in Bogor, Indonesia

Many methods have been explored to increase the palatability of pine (Pinus merkusii), the most common wood used for termite baiting. However, because of the undersupply of pine in Indonesia, it is crucial to vary the wood species for termite baiting and look for potential alternatives. Furthermore, various studies have shown that baiting time influences the intensity and pattern of termite attacks. Therefore, the present research aimed to study the preferences of subterranean termites and find the ideal baiting time among community wood species from Bogor, West Java, as a baiting alternative to pine. The woods tested were Acacia mangium (acacia), Falcataria moluccana (sengon), Anthocephalus cadamba (jabon), Maesopsis eminii (manii), Swietenia mahagoni (mahogany), Hevea brasiliensis (rubberwood), and P. merkusii (pine). Field tests were carried out based on the American Society for Testing and Materials D 1758-06 at the Arboretum, Faculty of Forestry and Environment, IPB University, with a baiting time of one to six months. The results led to the identification of four species of termites, namely Microtermes sp., Macrotermes sp., Shedorhinotermes sp., and Capritermes sp.. The frequency of termite attacks on the test site reached 93.1%. Rubberwood was the most potential wood bait for subterranean termites, indicated by the highest average weight loss value (65.8%) with a shorter optimal baiting time (up to one month) than that of other tested woods.

Decomposition of Wood by Termites in Different Types of Land Use

Decomposition is an important process in nature, as it can break down organic matter into smaller particles and nutrients. Nutrients are returned to the environment and can be reused by other organisms. One important organism that plays a role in the decomposition process is termites because termites are able to decompose organic matter such as wood in all habitats. Different termite habitats can be seen in terms of different types of land use. Some types of land use, such as natural forests, secondary forests, palm oil plantations, and settlements, can be used as a test site for wood decomposition by termites. All types of land use can be found in Dharmasraya Regency, West Sumatra Province. The purpose of this study was to study the decomposition of wood by termites in several different types of land use. Four types of land use are selected from habitats with the least disturbed conditions to the extent of high habitat disturbances, namely natural forests, secondary forests, palm oil plantations, and settlements. The study was conducted in Dharmasraya Regency, West Sumatra Province. The research method uses pine wood bait (Pinus merkusii), measuring 1.9 cm x 1.9 cm x 25 cm. The wooden bait is winded for seven days, and the wood bait is weighed to gain its initial weight and measured moisture content. Furthermore, wood bait that has been installed is observed and re-weighed to gain final weight and measured water content. The results showed that deforestation in Dharmasraya, West Sumatra had an effect on reducing wood decomposition by termites. Five (5) termite species were found in wood bait, including Pericapritermes sp.1, Microtermes sp.1, Schedorhinotermes sp.1, Macrotermes gilvus, and Coptotermes curvignathus.

Timing of Resource Addition Affects the Migration Behavior of Wood Decomposer Fungal Mycelia.

Studies of fungal behavior are essential for a better understanding of fungal-driven ecological processes. Here, we evaluated the effects of timing of resource (bait) addition on the behavior of fungal mycelia when it remains in the inoculum and when it migrates from it towards a bait, using cord-forming basidiomycetes. Experiments allowed mycelium to grow from an inoculum wood across the surface of a soil microcosm, where it encountered a new wood bait 14 or 98 d after the start of growth. After the 42-d colonization of the bait, inoculum and bait were individually moved to a dish containing fresh soil to determine whether the mycelia were able to grow out. When the inoculum and bait of mycelia baited after 14 d were transferred to new soil, there was 100% regrowth from both inoculum and bait in Pholiota brunnescens and Phanerochaete velutina, indicating that no migration occurred. However, when mycelium was baited after 98 d, 3 and 4 out of 10 replicates of P. brunnescens and P. velutina, respectively, regrew only from bait and not from inoculum, indicating migration. These results suggest that prolonged periods without new resources alter the behavior of mycelium, probably due to the exhaustion of resources.

Diversity of marine fungi associated with wood baits in the estuary Ria de Aveiro, with descriptions of Paralulworthia halima, comb. nov., Remispora submersa, sp. nov., and Zalerion pseudomaritima, sp. nov.

ABSTRACT Lignicolous marine fungi are a particular group of microorganisms that are typically found in mangroves, salt marshes, and estuaries, normally associated with driftwood or submerged wood. During investigations of lignicolous fungi occurring in the estuary Ria de Aveiro, Portugal, wood baits were submerged in a marina for 1 year. Seventeen distinct marine fungal species were identified, with the most abundant taxa belonging to the family Lulworthiaceae. Through single- and multilocus phylogenies based on sequences of the internal transcribed spacer (ITS) region and large subunit (28S) and small subunit (18S) of the ribosomal RNA gene cluster in combination with morphological and physiological data, we describe Remispora submersa, sp. nov., and Zalerion pseudomaritima, sp. nov., as novel species. Additionally, we propose that Papulaspora halima, a species whose taxonomic placement has been somehow confusing, be transferred to the genus Paralulworthia as Paralulworthia halima.

Diversity, density and distribution of termites in housing complexes in Purwokerto, Central Java, Indonesia

Abstract. Pratikno H, Haryanto T, Apriyanto DN. 2020. Diversity, density, and distribution of termites in housing complexes in Purwokerto City, Central Java Indonesia. Biodiversitas 21: 5729-5735. Termite attacks have detrimental effects on buildings and incur considerable costs. The rapid development of housing complex in Purwokerto City, Central Java Province, Indonesia urges an investigation on the occurrence of termite attacks. This research aimed to identify the diversity of termite species, its spatial distribution and its density on a variety of wood on housing complexes in Purwokerto City and the surrounding areas. The context of this study focused on wood species commonly used by the developers, namely albasia (Paraserianthes falcataria), which is commonly used for the upper ceiling, bangkirai (Shorea laevifolia) for poles and door/window frames, and teak (Tectona grandis) which is often used for door and window boards. We used bait techniques with the rationale that it is cheap and environmentally friendly as well as accurate. Four housing complexes in four subdistricts were randomly selected stratified based on four altitude ranges (<100 m, 100 m, 200 m, and 300 m). In each selected housing complex wood baits of three durability types (i.e. albasia, bangkirai and teak) were installed, each measuring 30 cm x 2 cm x 2 cm with five replications. Data of termite species, spatial distribution of termite species, and individual density in each housing complex were recorded after three months since the wood baits were stockpiled. Microclimate variables during the study were also recorded. The differences in density across housing complexes and the three types of wood were tested using ANOVA and continued with Duncan's test. The results showed three species of termites attacked wood baits, namely Microtermes insperatus, Macrotermes gilvus, and Odontotermes javanicus, all belong subterranean termite group. M. insperatus and O. javanicus had specific spatial distribution without overlapping zone among the two, while M. gilvus was the most adaptable and widely distributed in all housing complexes (<100-300 m asl.) regardless of the durable quality of the wood. There was significant difference in termite attacks across housing complexes with Ketapang housing complex in Sokaraja Subdistrict (<100 m asl.) was most frequently attacked. Conversely, there were no significant differences in termite attacks across the three types of wood (i.e. albasia, bangkirai, and teak).

Ecological memory and relocation decisions in fungal mycelial networks: responses to quantity and location of new resources

Saprotrophic cord-forming basidiomycetes, with their mycelial networks at the soil/litter interface on the forest floor, play a major role in wood decomposition and nutrient cycling/relocation. Many studies have investigated foraging behaviour of their mycelium, but there is little information on their intelligence. Here, we investigate the effects of relative size of inoculum wood and new wood resource (bait) on the decision of a mycelium to remain in, or migrate from, inoculum to bait using Phanerochaete velutina as a model. Experiments allowed mycelium to grow from an inoculum across the surface of a soil microcosm where it encountered a new wood bait. After colonisation of the bait, the original inoculum was moved to a tray of fresh soil to determine whether the fungus was still able to grow out. This also allowed us to test the mycelium’s memory of growth direction. When inocula were transferred to new soil, there was regrowth from 67% of the inocula, and a threshold bait size acted as a cue for the mycelium’s decision to migrate for a final time, rather than a threshold of relative size of inoculum: bait. There was greater regrowth from the side that originally faced the new bait, implying memory of growth direction.

Suspended Dead Wood Decomposes Slowly in the Tropics, with Microbial Decay Greater than Termite Decay

Coarse woody debris (CWD) is an important pool of carbon in forest ecosystems and is present in all strata as fallen, standing or suspended CWD. However, there are relatively few decomposition studies of CWD in tropical forests compared with temperate forests, and research on suspended CWD in particular has largely not been attempted. Termites are important decomposers in tropical ecosystems yet their role relative to microbial decomposers and the importance of the vertical location of CWD has rarely been considered. For the first time, we examined the relative contribution of macro-invertebrates (predominantly termites) and microbes to the decay of suspended and ground-placed (fallen) CWD in lowland, tropical rainforest. We set up wood baits (Pinus radiata) with and without termite access, and measured wood mass loss after 1 year. Mass loss of ground-placed CWD assays was over four times greater than suspended CWD assays. Termite decomposition was vertically stratified with termites having a large relative contribution to the decomposition of ground-placed CWD and a negligible contribution to the decomposition of suspended CWD. In contrast, the effect of microbes on decomposition was low and not vertically stratified. Although our results support the findings of temperate studies in that decomposition of CWD is dependent on its physical location, we show that in tropical rainforests this is predominantly due to greater termite decomposition on the forest floor. Suspended CWD remains an important carbon sink due to slow microbial decay until it falls to the forest floor where it is more accessible to termites.

Relative roles of termites and saprotrophic microbes as drivers of wood decay: A wood block test

AbstractDeadwood in tropical ecosystems represents an important but poorly studied carbon (C) pool. Biologically mediated decay of this pool occurs by both saprotrophic microbes and macro‐invertebrates, such as termites. The activity of these decay agents is influenced by abiotic conditions, especially water availability in tropical systems. While saprotrophic microbial activity is directly controlled by moisture, termites employ various morphological and behavioural modifications that should allow for continued activity in dry conditions. We therefore hypothesized that the relative role of termites would be enhanced in the dry season and a dry compared to a wet site. We deployed a novel wood bait (Pinus radiata) at two sites (rainforest and savanna), with or without access holes cut into termite‐excluding mesh. Mass loss from wood baits was measured after a dry season and after a full dry/wet annual cycle. Mass loss was higher at the rainforest site, demonstrating the overall role of moisture in driving wood decay. Counter to expectations, we found no evidence that the relative role of termites was higher at the dry site, nor during the dry season. However, the prevalence of termites was higher in the savanna compared to the rainforest. While termites clearly impact wood decay, these findings indicate that the relative importance of termites in the fate of deadwood may not reflect their mere presence within and across ecosystems. If moisture availability shifts under climate change, our results suggest similar functional responses between termites and saprotrophic microbes in driving C loss from deadwood.

Bait and scrape: An approach for assessing biofilm microbial communities on organic media used for gas-phase biofiltration

Gas-phase biofilters offer effective pollution control for agricultural effluents, but a better understanding of microbial communities responsible for capture and degradation is needed to improve process control. In this study, we developed a wood bait and optimized microbial biofilm sampling for monitoring microbial biomarkers (microbial C, ergosterol, DNA) in a full-scale biofilter. Results demonstrated that targeting biofilm dynamics required removing the biofilm from the wood substrates prior to biomarker extraction. We identified a sampling threshold for these biofilms of ≥100mg for accurate and low variability biomarker measurement, a threshold that can inform analyses in other systems or using other approaches (i.e. DNA sequencing). Using this approach in a full-scale biofilter revealed that the fungal contribution (as ergosterol) to total microbial biomass was greatest in the most desiccation-prone area of the biofilter. This observation is in-line with results from previous lab-scale studies and could be due, in part, to connectivity between fungal hyphae growing in biofilms and the wood baits, shown by confocal microscopy. This work provides a targeted sampling strategy for microbial biofilms in gas-phase biofiltration, adaptable to other pollution control bioreactors and that can be used to study microbial community dynamics in full-scale systems.

Effects of two locust control methods on wood-eating termites in arid Australia

Termites are ubiquitous detritivores and are a key influence on soil function and nutrient cycles, particularly in arid and semi-arid ecosystems. Locust control presents a unique hazard to termites and the effective functioning of ecosystems as a consequence of the overlap between pesticide applications and termite populations in grassland and desert landscapes. We monitored the effects of locust control methods using ultra-low-volume (ULV) barrier application of a chemical pesticide, fipronil, and a blanket application of a fungal biopesticide, Metarhizium acridum, on wood-eating termites in arid western New South Wales, Australia. We tested the hypothesis that spray applications decrease termite activity at wood baits using a BACI designed field experiment over 2 years. Our replicated control and treatment sites represented the spatial scale of Australian locust control activities. There was no detectable impact of either locust control treatment on termite activity, bait mass loss or termite community composition measures. Non-significant differences in termite survey measures among sites suggested that climate and environmental conditions were stronger drivers of our termite measures than the single, localized and unreplicated application of pesticides more commonly used in locust control operations in arid Australia. A lack of evidence for an impact of our fipronil or Metarhizium application methods supports their use as low hazard locust control options with minimal large scale and longer-term effects on termites in Australian arid rangelands. Future research would be necessary to determine the probable short-term impacts of treatments on individual termite colonies and the possible impacts on non-wood eating termite species in the arid-zone.

The impact of the locust control insecticide fipronil on termites and ants in two contrasting habitats in northern Australia

Termites and ants are key ecosystem engineers and nutrient re-cyclers. Extensive spraying of insecticides presents a hazard to these insects. Using a control-treatment paired design comprising 3 replicate pairs of plots per soil type, we quantified the impact of fipronil on termite consumption of cardboard and wood baits, termite repair of deliberately damaged mounds as well as ant community composition and abundance in two different habitats (black vertisol and red kandosol soil) when applied aerially at a dose rate recommended for locust control in Australia. The study was conducted from 2006 to 2008. The diversity of termites and ants was higher and side-effects were more pronounced on kandosol than on vertisol soil. Overall termite consumption of cardboard baits was significantly greater in unsprayed than in sprayed plots while losses were significantly greater in only one (vertisol) or two (kandosol) sprayed plots, respectively, compared to paired unsprayed plots. In the first year, termite consumption of wood baits was generally significantly greater on unsprayed than on sprayed kandosol while only marginally significant on unsprayed vertisol. Again, losses were significantly greater in one (vertisol) and two (kandosol) sprayed plots, respectively, compared to paired unsprayed plots. Overall termite consumption of wood baits was similar among plots in the second year post-spray although consumption remained significantly depressed in one pair of sprayed plots in each habitat. The capacity of the mound-building termite, Drepanotermes rubriceps (Froggatt) unique to kandosol, to repair damaged mounds was significantly reduced by fipronil. Furthermore, colonies of Iridomyrmex greensladei Shattuck, an ant species associated with mounds of D. rubriceps, were not re-located five months post-spray. Ant communities were also adversely affected. On vertisol, species richness and relative abundance were similar among treatments, but significantly fewer species were caught in one individual sprayed plot. In contrast on kandosol, species richness and relative abundance were significantly reduced by fipronil. A drop in species richness was observed in all and a drop in relative abundance in two sprayed plots. On vertisol, abundances of two species were significantly lower in sprayed than in paired unsprayed plots. Likewise on kandosol, abundances of five species were significantly reduced in sprayed plots, and one species was not caught at all. The weight of evidence of our findings indicate that fipronil, even at a low rate, will have substantial adverse impacts on the diversity and activity of termites and ants, especially if applied within one to two years of earlier applications.

Resource acquisition by the mycelial-cord-former Stropharia caerulea: effect of resource quantity and quality

Saprotrophic mycelial-cord-forming basidiomycetes, which extend between organic substrata on the forest floor, exhibit remarkable patterns of reallocation of biomass and nutrients when encountering new resources. These have been equated with foraging strategies, and differ between species, resources quality and quantity. Stropharia caerulea occupies more disturbed sites than the fungi previously examined, and the responses of its mycelial foraging systems were investigated non-destructively by image analysis. Resource quantity and quality affected extension rate, extra-resource biomass production and distribution, as quantified by box-count fractal dimension. When mycelia grew from 0.5 cm3 beech (Fagus sylvatica) wood inocula across compressed, non-sterile soil to 0.06–4 cm3 uncolonised sterile beech wood extension rate fell after contact with large wood baits but biomass production and mycelial distribution was unaffected. In contrast, extension rates of cord systems grown from 0.15 cm3U. dioica rhizome inocula to 0.1–1.2 cm3 rhizome were unaffected after contact with equal or larger sized baits, but biomass production rates fell and mass fractal dimension increased. Mycelial morphology was affected by inoculum age; systems grown from 84 day old 0.5 cm3 beech wood inocula took 10 days longer achieving the fractal values of systems developing from 22 day old inocula. Foraging strategies and resource relations of mycelial cord systems are discussed.

Comparison of colony foundation success between sexual pairs and female asexual units in the termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

AbstractIn termites, a male and a female usually found a colony cooperatively. However, pairing efficiency tends to be low in Reticulitermes speratus because of a limited mate‐searching range, the female‐biased sex ratio, and a relatively low calling ability. Females that fail to pair with males found colonies either in female–female pairs or even alone. In the laboratory, we examined colony foundation by single females (F), female–female pairs (FF), and normal male–female pairs (FM). The time until colony foundation (when termites began excavating wood baits) differed significantly among the unit types. Time until excavation was much longer for single females than for FF and FM units, which reflects the relative success of colony foundation. The survival rate of single females was also significantly lower than that of FF‐ and FM‐unit females, although there was no difference between FF and FM units. This result demonstrates that cooperation, even female–female, promotes female survivorship. Nevertheless, the number of progeny per female was significantly lower in FF units than in FM units, possibly because females of FF units must share reproductive output. These results lead us to the conclusion that a normal monogamous pair is the best unit for colony foundation. Nevertheless, females alone can establish colonies by parthenogenesis, and even female–female cooperation promotes colony foundation success if pairing with males is not possible. Considering the functional decision for females in F and FF units of how much time to spend searching for a male mate, we believe that these facultative pathways of colony foundation by parthenogenesis have adaptive significance.

Three-dimensional outgrowth of a wood-rotting fungus added to a contaminated soil from a former gasworks site

The capability of wood-rotting fungi (WRF) to colonise contaminated soil is an important fungal characteristic in the development of WRF-based soil bioremediation, it is also important to have methods that monitor the presence of the WRF in the soil. In this lab-scale study, it was shown that it was possible to re-capture, localise and identify a brown-rot fungus, Antrodia vaillantii, after it has been inoculated into, and grown in, a contaminated soil from a former gasworks site. The three-dimensional outgrowth of A. vaillantii was monitored by allowing it to grow into fungicide-treated wood baits, temporarily placed in the soil. After two weeks, the baits were withdrawn from the soil and surface sterilised with hydrogen peroxide to favour fungi growing inside baits, i.e., A. vaillantii. After subsequent plating of baits on selective agar medium the presence of A. vaillantii was confirmed with PCR/RFLP. A. vaillantii was found to be viable throughout the 54 days long study and exhibited a surface growth pattern similar to other well-known cord-forming basidiomycetes. Firstly, the upper part of the soil closest to the place of inoculation was colonised, however, over a period of time, the area of colonisation spread deeper into the soil. The detection method employed in the current study gave a conservative estimate of the fungal proliferation and did not require extensive sampling. Its use could be applicable in both applied research, such as soil bioremediation, and in pure microbial ecology studies.

Temporary phosphorus partitioning in mycelial systems of the cord-forming basidiomycete Phanerochaete velutina.

Mycelial cord systems, up to 50-cm diameter, of the basidiomycete Phanerochaete velutina (DC.: Pers.) Parmasto, a common woodland saprotroph, grown on non-sterile soil in model laboratory microcosms were baited, after 27 d, with pairs of fresh beech wood blocks (baits), placed at 10 d intervals behind the foraging colony margin. System development was quantified by image analysis. Mean radial extent and hyphal cover increased linearly with time until day 21, but declined before the mycelial systems reached the edges of the laboratory microcosms. The mass (DBM ) and border (DBS ) fractal dimensions of the mycelial systems changed with time but the ratio DBM ∶DBS became constant after 14 d. A separate central compartment containing the inoculum was supplied with 32 P orthophosphate and its translocation to wood baits monitored non-destructively for 73 d. Whilst total 32 P acquisition by wood baits increased linearly with time, the proportion of total allocated to baits varied significantly both temporally and according to the length of time that baits had been in contact with the mycelium. Most recently supplied wood baits were not the main sink for supplied phosphorus; rather, the rate of 32 P acquisition was initially greatest in baits from which egress of the fungus had already occurred. The rate of 32 P acquisition by the most recently added baits increased with time, supported by efflux from other wood baits, which had initially been the main sinks for translocated phosphorus. The results raise important questions about the ecological and functional significance of nutrient partitioning in cord systems and imply that 'observed' translocation, rather than being an absolute measure, indicates the degree to which phosphorus is loaded from a translocation stream in regions where it is being actively utilized and/or stored.

Wood decay and phosphorus translocation by the cord‐forming basidiomycete Phanerochaete velutina: the significance of local nutrient supply

Mycelial cord systems of Phanerochaete velutina (DC.: Pers.) Parmasto grown from 4 cm3 inocula on a nutrient‐depleted non‐sterile soil in compartmentalized laboratory microcosms were baited after 13 d of growth with either fresh, non‐sterile 4 cm3 wood blocks or control Perspex® blocks of the same contact area. After 112 d, mature mycelial systems, which were in senescent phase, were subjected to disturbance by supplying a new fresh wood bait diametrically opposite the existing bait and, after 126 d, to nutrient regime amendment by application of NPK solution. At harvest (186 d) there was a significant (P0·001) linear relationship between extra‐resource mycelial biomass and total wood decay over the preceding 74 d. Nutrient amendment alone did not significantly (P>0·05) affect extra‐resource mycelial biomass production or wood decay rates in either disturbed or undisturbed cord systems. However, both mycelial biomass production and resource decay were significantly (P0·05) enhanced when nutrient amendment and disturbance treatments were applied concurrently. Bi‐directional phosphorus translocation to inocula and wood baits (determined non‐destructively) was assessed by labelling the NPK solution applied distal or proximal to the initially supplied bait with 32P. In both disturbed and undisturbed cord systems the rate of 32P uptake from a local supply was two orders of magnitude higher than from a distal supply. In disturbed cord systems uptake of 32P by inocula, which were midway between the two radiotracer supply points, was significantly (P0·05) higher when the supply point contained a newly supplied wood bait. Net translocation of 32P to newly supplied wood baits increased with time at the expense of translocation to inocula and existing wood baits. The switch in direction of net phosphorus translocation, the importance of localized nutrient scavenging and the partitioning of wood decay are discussed in relation to the ecological significance of mycelial cords.

Patch formation and developmental polarity in mycelial cord systems of Phanerochaete velutina on a nutrient-depleted soil.

Development of mycelial cord systems of Phanerochaete velutina (DC.: Pers.) Parmasto from 4-cm3 inocula on a nutrient-depleted non-sterile soil was studied in laboratory microcosms using image analysis techniques. Cord systems were "baited" after 13d growth with either fresh, non-sterile 4-cm3 wood baits or control Perspex® blocks of the same contact area placed behind the foraging mycelial front. After 26 d growth, mycelial 'patches' arose by dedifferentiation of consolidated mycelial cords in both wood- and Perspex-baited cord systems. 'Patches' comprised fine, highly branched separate hyphae extending radially from points of aggregated hyphae in cords. 'Patches' and cords could be readily distinguished by image analysis and the areas covered by patches and cords could be measured and compared. Whilst the total hyphal cover of Perspex- and wood-baited systems did not differ significantly (P > 0.05), patch cover in wood-baited systems was up to 10 times greater than in Perspex-baited systems. Patches were temporary structures, regressing more rapidly with age than mycelial cords. Patch development ceased after application of a nutrient solution which replenished phosphate levels in the soil. Wood-baited mycelial systems displayed significant developmental polarity (P≤ 005) of both total hyphal cover (patches plus cords) and hyphae in patches towards the 'baited' sector of cord systems after 42 d, which corresponded with peak patch development. However, significant (P≤ 0.05) developmental polarity of the mycelial systems along the bait-inoculum line could be detected 8 d before patch formation when assessed by fractal geometry. Radiotracer studies showed that mycelial patches were not sinks for supplied 32 P, but that they were sites of increased nutrient uptake capacity compared with that of mycelial cords. We discuss the need for mycelial cord systems to balance allocation of mycelial biomass between the two essential processes of colonizing wood resource units, and the acquisition of soluble inorganic nutrients from soil.