Mycorrhizal Response to Experimental pH and P Manipulation in Acidic Hardwood Forests

<div><p>Many temperate forests of the Northeastern United States and Europe have received significant anthropogenic acid and nitrogen (N) deposition over the last century. Although temperate hardwood forests are generally thought to be N-limited, anthropogenic deposition increases the possibility of phosphorus (P) limiting productivity in these forest ecosystems. Moreover, inorganic P availability is largely controlled by soil pH and biogeochemical theory suggests that forests with acidic soils (i.e., </p></div

Rarefaction curves showing the expected number of species (97% OTUs) as a function of the number of EcM root tips from each treatment.

<p>Although the control appears to have lower diversity than the treatments, this visual difference is not statistically significant (95% confidence intervals not shown to improve figure clarity).</p

CCA ordinations showing the effect of location, treatment, pH, and P availability on the on AM (A) and EcM (B) communities.

<p>Region is denoted by shape: glaciated (triangles) and unglaciated (inverted triangles) and treatment is denoted with color: control (white), elevated pH (grey), elevated P (dotted grey), and elevated pH+P (black). Centroids and error bars represent the mean and standard errors of axes scores within a given treatment. Monte Carlo <i>P</i>-values for eigenvalues for the AM and EcM ordinations were 0.03 and <0.01, respectively. Joint-plot overlays were unable to detect any significant correlations between tree species and either the AM or EcM community composition.</p

The effect of region and treatments on soil pH and phosphorus with mean values and standard errors.

<p><i>P</i>-values for the effect of region and treatments from the LME model with forest blocks as the random effect (n = 9). Asterisks denote a significant difference, in comparison to controls, at <i>P</i><0.05 (**) and <i>P</i><0.10 (*).</p