Mycorrhizal Role in Net Primary Priduction and Nutrient Cytcling in Abies Amabilis Ecosystems in Western Washington

Vogt, Kristiina A.; Grier, Charles C.; Meier, Carine; Edmonds, Robert L.

doi:10.2307/1938955

Cited by 245 publications

(107 citation statements)

References 19 publications

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“…It is still unclear whether investments in ®ne roots increase with altitude in trees as they do in forbs, and exports to ectomycorrhiza and ®ne root turnover are unknown (both have been suggested to be particularly important for high-altitude forests; cf. Moser 1966;Wardle 1971;Vogt et al 1984). In their analysis Stevens and Fox (1991) also emphasized the possibility of a rootbased explanation of treeline, but they suggest that`c entral place foraging'' in large, single stemmed individuals in an increasingly patchy and climatically hostile environment may cause a cost/bene®t problem.…”

Section: The Carbon Balancementioning

confidence: 99%

A re-assessment of high elevation treeline positions and their explanation

1998

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In this review I ®rst compile data for the worldwide position of climate-driven alpine treelines. Causes for treeline formation are then discussed with a global perspective. Available evidence suggests a combination of a general thermal boundary for tree growth, with regionally variable``modulatory'' forces, including the presence of certain taxa. Much of the explanatory evidence found in the literature relates to these modulatory aspects at regional scales, whereas no good explanations emerged for the more fundamental global pattern related to temperature per se, on which this review is focused. I hypothesize that the life form``tree'' is limited at treeline altitudes by the potential investment, rather than production, of assimilates (growth as such, rather than photosynthesis or the carbon balance, being limited). In shoots coupled to a cold atmosphere, meristem activity is suggested to be limited for much of the time, especially at night. By reducing soil heat¯ux during the growing season the forest canopy negatively a ects root zone temperature. The lower threshold temperature for tissue growth and development appears to be higher than 3°C and lower than 10°C, possibly in the 5.5±7.5°C range, most commonly associated with seasonal means of air temperature at treeline positions. The physiological and developmental mechanisms responsible have yet to be analyzed. Root zone temperature, though largely unknown, is likely to be most critical.

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Section: The Carbon Balancementioning

confidence: 99%

A re-assessment of high elevation treeline positions and their explanation

1998

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“…The nutrient uptake from the soil and transport to the mycorrhizal root system is mediated to a large extent by extraradical mycelium growing outwards from the mycorrhizal mantle (Read, 1992 ;Marschner & Dell, 1994). The extraradical mycelium also provides the basis for the formation of fruit bodies, which represent, however, only a small proportion of the total ECM fungal biomass in a forest ecosystem (Fogel & Hunt, 1979 ;Vogt et al, 1982).…”

Section: mentioning

confidence: 99%

Nitrogen deposition and ectomycorrhizas

1998

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As a result of increasing anthropogenic nitrogen deposition, N availability in many forest ecosystems, which are normally N-limited, has been enhanced. We discuss the impacts of this increased N availability on the ectomycorrhizal (ECM) symbiosis which is generally regarded as an adaptation to nutrient limited conditions. Nitrogen deposition can influence fruit-body formation by ECM fungi, the production and distribution of the extraradical mycelium in the soil and the formation of ectomycorrhizas.Available data from long-term N deposition studies indicate that the most prominent effects might be discernible above-ground (i.e. on the formation of fruit bodies). ' Generalist ' species, forming a symbiosis with a wide range of tree species, seem to be less affected by increased N availability than ' specialist ' species, especially those living in symbiosis with conifers. However, the importance of below-ground investigations to determine the impacts of N deposition on the ECM symbiosis must not be underestimated. Culture experiments show an optimum N concentration for the formation of extraradical mycelium and mycorrhizas. Often, negative effects only become visible at comparatively high N concentrations, but the use of a few easily cultivated species of ECM fungi, which are adapted to higher N concentrations, undermines our ability to generalize.So far, N deposition experiments in the field have only shown minor changes in the below-ground mycorrhizal population, as estimated from the investigation of mycorrhizal root tips. However, effects on the ECM mycelium, which is the main fungal component in terms of nutrient uptake, cannot be excluded and need further consideration.Because the photoassimilate supply from the plant to the fungal partner is crucial for the maintenance of the ECM symbiosis, we discuss the possible physiological implications of increasing N inputs on the allocation of C to the fungus. Together with ultrastructural changes, physiological effects might precede obvious visible changes and might therefore be useful early indicators of negative impacts of increasing N inputs on the ECM symbiosis.

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“…Late seasonal defoliation or repeated defoliation of deciduous trees may deplete reserves and lead to branch die-back or death of the whole tree (Heichel and Turner, 1984 (Wargo, 1979 (Agren, 1985b;Ingestad and Lund, 1986;Ingestad and Agren, 1988 (Carlyle, 1986 (Eissenstat and Caldwell, 1988 (Carlyle, 1986). This occurs when the substrate C:N ratio decreases to that of the microbial biomass; thus the C:N ratio at which mineralization begins can be associated with site and other factors (Berg and Ekbohm, 1983 (Vogt et al, 1982). However, in controlled experimental systems when nitrogen addition rates were held constant, mycorrhizae did not increase nitrogen uptake even at low levels of addition and decreased relative growth rate of pine seedlings, indicating a carbon drain ).…”

Section: Introductionmentioning

confidence: 99%