Morphotype community structure of ectomycorrhizas on Douglas fir ( Pseudotsuga menziesii Mirb. Franco) seedlings grown under elevated atmospheric CO 2 and temperature

Abstract

Mycorrhizas alter the acquisition of carbon and nutrients, thereby affecting numerous plant and ecosystem processes. It is important, therefore, to determine how mycorrhizal populations will change under possible future climate conditions. Individual and interactive effects of elevated atmospheric CO concentration and atmospheric temperature were assessed in a 2×2 factorial design [ambient and elevated (200 ppm above ambient) CO concentrations, and ambient and elevated (4°C above ambient) temperatures]. In June 1993, 2-year-old Douglas fir (Pseudotsuga menziesii Mirb. Franco) seedlings were planted in 12 environment-tracking chambers (n=3) containing reconstructed, low-nitrogen, native forest soil. Climate treatments were imposed shortly thereafter, and the seedlings grew until June 1997. Soil cores were taken twice per year during the exposure period. We present findings on changes in the community structure of ectomycorrhizal (ECM) root tips, categorized into morphotypes using gross morphological traits. A diverse and stable community of morphotypes (a total of 40) was encountered; no more than 30 of which were seen at any sampling time. In the first sample, there were only 15 morphotypes found in the 12 chambers. Morphotype numbers increased during the first half of the experiment, remaining fairly constant thereafter. Near the end of the exposure, elevated-temperature treatments maintained more morphotypes than ambient treatments. However, overall, absolute measures (number of ECM tips) were affected primarily by CO treatment, whereas proportional measures (e.g., Simpson's index) were affected primarily by temperature. While some morphotypes were negatively affected seasonally by higher temperatures (putative Rhizopogon group), others (Cenococcum) seemed to thrive. Underlying the dominant patterns of change in diversity, driven by the Rhizopogon group, subdominant populations responded slightly differently. Community diversity through time tended to increase at a greater rate for all subdominant populations compared with the rate when dominant populations were included.

The effect of experimental warming on the root-associated fungal community of Salix arctica

“…This finding is contrary to a previous study examining the effects of warming on ectomycorrhizal fungal communities of Douglas-fir seedlings. Rygiewicz et al (2000) found an increase in the number of different mycorrhizal fungi on seedlings grown in controlled environment chambers with elevated temperatures compared to those grown in chambers with ambient temperatures. Differences in results between our study could be due to the following: (1) differences in how the hosts react to warming; (2) the age of the plant, as seedlings were used for their study while we sampled mature shrubs and (3) greater availability of fungal inoculum, which may be more widely dispersed at lower latitudes, providing greater opportunity for migration of new genotypes.…”

“…Our findings suggest that the root-associated fungal community at these tundra sites were quite resilient to warming, as evidenced by the lack of change in genotype richness or evenness (Kårén and Nylund, 1997;Rygiewicz et al, 2000). Over longer time periods, it would be interesting to know if sites with higher richness, such as the LG and UG sites, are more resilient than the UD site.…”

“…Responses of mycorrhizal fungi to simulated global change factors (CO 2 , warming, shading and fertilization) are also variable, although several studies have found a not unexpected link between increased plant C allocation belowground and increased mycorrhizal colonization (Staddon et al, 2002;Urcelay et al, 2003;Fitter et al, 2004;Heinemeyer and Fitter, 2004;Olsrud et al, 2004;. Some studies have found that experimental treatments alter mycorrhizal community composition (Rygiewicz et al, 2000;Parrent et al, 2006), but these changes are rarely of sufficient magnitude to significantly change the overall richness or diversity of the community.…”

Tallgrass prairie soil fungal communities are resilient to climate change

“…In addition to the ecosystem level context dependencies (Compant et al 2010), interacting environmental drivers may further modulate the fungal community responses (Hayden et al 2012). For example, Rygiewicz et al (2000) showed that soil fungal community responses to elevated temperature differed between [CO 2 ] treatments. Heterotrophic fungal communities and their responses to shifts in environmental conditions are particularly important, because they are essential in carbon and nutrient cycling (Dighton 2003), comprise a large recalcitrant belowground carbon sink (Treseder & Allen 2000), and may be affected directly by the shifts in the environmental drivers or indirectly through the responses in plant communities (Cregger et al 2012).…”

Elevated Atmospheric CO2 Affects Ectomycorrhizal Species Abundance and Increases Sporocarp Production under Field Conditions

“…Some of these experiments have shown little effects of elevated CO2 in ectomycorrhizal community structure. Rygiewicz et al [27] planted two-year-old Pseudotsuga menziesii (Mirb.) Franco seedlings in chambers, and after four years of elevated CO2 exposure found small overall effects on the ectomycorrhizal morphotype community structure.…”