Influence of liming and acidification on the activity of the mycorrhizal communities in a Picea abies (L.) Karst. stand

A study of mycorrhizal activity was conducted in a mature Norway spruce ((Picea abies) [L.] Karst.) stand subjected to soil treatments of liming and acidification for six years (Höglwald research project). Samples were collected five times during one growing season using a soil corer. All the turgescent, not shriveled mycorrhizal tips were sorted out and identified on the fungal species level as far as yet possible. The proportion of each mycorrhizal type on the plots was calculated. The results revealed a shift in the mycorrhizal communities caused by both acid rain and liming. Data are in agreement with the findings of the more comprehensive study on the mycorrhizal communities carried out by another research group on the same plots (Taylor et al., submitted)The activity of the predominant types of mycorrhizas, Piceirhiza gelatinosa, Piceirhiza nigra, Russula ochroleuca-P. abies, Tuber puberulum-P. abies, Tylospora sp.-P. abies, Xerocomus badius-P. abies, was investigated by staining hand sectioned tips with FDA and their fluorescence. Different FDA-hydrolysing activities of the mycorrihizal types had been found in a previous-year study on the same plots and were confirmed during the second year. The proportion of the different stages of activity of the mycorrhizal tissues was calculated on the type level and in connection to the soil treatments. X. badius-P. abies and R. ochroleuca-P. abies displayed the most active fungal tissues and proportion increased on the acidic plots while Tuber puberulum-P. abies and Piceirhiza nigra were the most active types and occurred in higher proportion after liming. Thus, the overall activities of the mycorrhizas were only slightly changed by the treatments. In addition to the mycorrhizal effect acidification reduced while liming enhanced the meristematic activity of the short root tips. The same tendency was found by studying root production on the same plots (Hahn and Marschner, 1998). Although nearly 3000 mycorrhizal tips were studied, the data are still limited, allowing no statistical validation. This is, however, the first investigation connecting overall activity of the mycorrihizal tissues with the proportion of the mycorrhizal types as influenced both by alterations of the forest soil caused by acid rain and liming. The results are interesting and reasonable but further investments are necessary to validate the general conclusions.