What was done
Mushroom monitoring was performed each week without interruption during the yearly fruiting season over the period 1975-2006 at a 75-hectare "fungus reserve" in western Switzerland. This was done within a protected area that consisted of a multi-storied mixed-beech forest, where all aboveground fruiting bodies of larger fungi within five 300-m² plots were, in the words of the authors, "macroscopically and/or microscopically identified, counted, and mapped at weekly intervals." This incredible effort resulted in data being recorded for a total of 65,631 individual mycorrhizal mushrooms representing 273 species; and using these data, Buntgen et al. state that "seasonal mushroom means and their time of emergence were correlated against monthly and seasonal means of different climate indices, over different temporal intervals." So what did they learn?

What was learned
The three researchers report that "the average annual number of observed mushrooms increased from 1313 (pre-1991) to 2730 (1991 and thereafter), while average fruiting time during the latter period was delayed by 10 days as compared with that of the former." In addition, they state that the "reconstructed intra-annual timing of mushroom fruiting for the 20th century paralleled contemporary Swiss wine harvest dates, providing independent evidence of climate-induced ecosystem change."

What it means
In describing the significance of their findings, Buntgen et al. write that "enhanced growth conditions and extended growing seasons appear beneficial to fungi," and they state that "the observed changes can be explained by improved growth conditions and extended growing seasons during the late 20th century, not only for the fungi but also for their host plants." And they conclude that these "enhanced growth conditions and extended growing seasons appear beneficial from an economic as well as from an environmental perspective."

From an economic perspective, for example, they say that "an increase in the number of fungal fruiting bodies represents an edible attraction for both humans and animals," noting that "some edible mycorrhizal fungi are among the world's most expensive delicacies," citing Hall et al. (2003), while also reporting that mycelial formation and mushroom production "represent an important food supply for many soil invertebrates and small mammals," citing Krebs et al. (2008).

Likewise, from an ecological perspective, they indicate that the thread-like hyphae of the fungi "increase the efficiency of water and nutrient absorption in host plants, thereby enhancing their resistance to pathogens," citing Smith and Read (1997); and they further explain that "this symbiotic relationship has considerable impact on carbon dioxide sequestration in terrestrial ecosystems (Hogberg and Read, 2006; Orwin et al., 2011) by increasing the amount of biomass turnover and carbon exchange."

And let it be noted that the fungal growth enhancements and growing season elongations that were documented by Buntgen et al. occurred concomitantly with what climate alarmists typically describe as (1) unprecedented global warmth within a millennial context and (2) unprecedented atmospheric CO2 concentrations within a far more lengthy time period.

References
Hall, I.R., Wang, Y. and Amicucci, A. 2003. Cultivation of edible ectomycorrhizal mushrooms. Trends in Biotechnology 21: 433-438.

Hogberg, P. and Read, D.J. 2006. Towards a more plant physiological perspective on soil ecology. Trends in Ecology and Evolution 21: 548-554.

Krebs, C.J., Carrier, P., Boutin, S., Boonstra, R. and Hofer, E. 2008. Mushroom crops in relation to weather in southwestern Yukon. Botany 86: 1497-1502.

Orwin, K.H., Kirschbaum, M.U.F., St John, M.G. and Dickie, I.A. 2011. Organic nutrient uptake by mycorrhizal fungi enhances ecosystem carbon storage: a model-based assessment. Ecology Letters 14: 493-502.

Smith, S.E. and Read, D.J. 1997. Mycorrhizal Symbiosis, 2nd edition. Academic Press, London, United Kingdom.