S

FIGURE 3.23 Effect of ectomycorrhizal species diversity on shoot and root growth of birch seedlings when inoculated with a random mixture of mycorrhizal fungal species, selected from a species pool. Data from Baxter and Dighton (2001).

a clear nutritional benefit accrues in an agricultural context. In his commentary on this work, Leake (2001) correctly points out that the study of Baxter and Dighton (2001) was conducted under laboratory conditions and that plant and fungal responses may be different in a more realistic field situation. These results, however, show how little we really understand of the complexities of fungal interactions and the role of diversity in the mycorrhizal community.

Cairney (1999) discussed the range of ectomycorrhizal species and their varied physiological functions, suggesting that we know relatively little about variation in the physiology of the few fungi that we have studied extensively in the laboratory, let alone the myriad of other species about which we know very little and especially of those fungi that we have yet to encourage to grow in culture. In addition, in their review article, Cairney and Burke (1996) cite examples of heterogeneity of the function of mycelia of the same ectomycorrhizal fungus as it exploits pockets of different resources in the soil. They suggest that this heterogeneity of function drives both the ability of

Table 3.17 Relationship Between Plant Growth Parameters and Either Ectomycorrhizal Fungal Diversity or Degree of Root Colonization by Ectomycorrhizal Fungi, Irrespective of Species, as Determined by Stepwise Multiple Regression Analysis

Growth

Nutrients

Table 3.17 Relationship Between Plant Growth Parameters and Either Ectomycorrhizal Fungal Diversity or Degree of Root Colonization by Ectomycorrhizal Fungi, Irrespective of Species, as Determined by Stepwise Multiple Regression Analysis

Nutrients

Dependent variable

Step variable

R2

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