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Restoration and Canopy Type Influence Soil Microflora in a Ponderosa Pine Forest

^a School of Forestry & Merriam-Powell Center for Environmental Research, Northern Arizona Univ., Flagstaff, AZ 86011-5018
^b Crop & Soil Sciences Dep., The Pennsylvania State Univ., University Park, PA 16802
^c School of Natural Resources & Environment, Univ. of Michigan, Ann Arbor, MI 48109

View larger version (25K): [in a new window]   Fig. 1. Mean volumetric soil water content for the 2001-growing season (0- to 15-cm mineral soil depth) for (A) treatments and (B) canopy types. Vertical arrows indicate sampling dates. Repeated measures ANOVA on ranks showed that treatment had a significant effect (P < 0.001) on soil water content across the growing season, with median values from control > thinning restoration > composite restoration plots (Dunn's method, n = 2). Repeated measures ANOVA on ranks also indicated that canopy type had a significant effect (P < 0.001) on soil water content across the growing season, with median values from grass > postsettlement pine retained = presettlement pine areas (Dunn's method, n = 6).

View larger version (31K): [in a new window]   Fig. 2. Mean soil temperature for the 2001-growing season (7.5-cm mineral soil depth) for (A) treatments and (B) canopy types. Vertical arrows indicate sampling dates. Repeated measures ANOVA on ranks indicated that treatment had a significant effect (P < 0.001) on soil temperature across the growing season, with median values from composite restoration > thinning restoration > control (Dunn's method, n = 2). Repeated measures ANOVA on ranks also indicated that canopy type had a significant effect (P < 0.001) on soil temperature across the growing season, with median values from grass > postsettlement pine retained = presettlement pine areas (Dunn's method, n = 6).

View larger version (35K): [in a new window]   Fig. 3. Mean soil respiration rates for (A) treatments and (B) canopy types. Different lowercase letters indicate significant differences within each sampling period, as determined by ANOVA and the Holm-Sidak mean separation test (P 0.033, Bonferroni corrected). Vertical lines represent one standard error of the mean. Respiration increased significantly from dry to wet periods for each treatment (A) and each canopy type (B), as determined by paired t tests (P 0.007). There were no significant differences among treatments or among canopy types for the wet period.

View larger version (35K): [in a new window]   Fig. 4. Mean enzyme activities in treatment plots for (A) dry and (B) wet periods. Vertical lines represent one standard error of the mean. During the dry period, all enzyme activities were statistically similar among treatments (based on ANOVA on ranks, P > 0.10). During the wet period, treatment had a significant effect on all enzyme activities. For a given enzyme, values with different lowercase letters are statistically different (P 0.033, Bonferroni corrected). All enzymes in each treatment increased significantly from dry to wet periods based on paired t tests at P 0.05. Enzymes are abbreviated as follows: ß-glucosidase (ß-gluc), -glucosidase (-gluc), galactosidase (galac), xylosidase (xylo), N-acetyl-glucosaminidase (nag), phosphatase (phos), and sulfatase (sulf).

View larger version (16K): [in a new window]   Fig. 5. Non-metric multi-dimensional scaling (NMDS) ordinations of bacterial and fungal community-level physiological profiles in restoration and control treatments during the dry and wet sampling periods. Each symbol represents a replicate plot (n = 5). Statistical differences among treatments were determined using multi-response permutation procedures (MRPP, P < 0.10), and are denoted by different lowercase letters (P 0.033, Bonferroni corrected). Ordination stress level, a measure of the quality of representation of the data in the ordination, ranged from 8.6 to 13.3; these values suggest fair to good ordinations with no real risk of drawing false inferences (Clarke, 1993).

View larger version (35K): [in a new window]   Fig. 6. Mean enzyme activities in canopy type during the (A) dry and (B) wet periods. Vertical lines represent one standard error of the mean. During the dry period, all enzyme activities were statistically similar among treatments (based on ANOVA on ranks, P > 0.10). During the wet period, canopy type had a significant effect on all enzyme activities except nag. For a given enzyme, values with different lowercase letters are statistically different (P 0.033, Bonferroni corrected). All enzymes in each canopy type increased significantly from dry to wet periods, based on paired t tests at P 0.05. Enzymes are abbreviated as follows: ß-glucosidase (ß-gluc), -glucosidase (-gluc), galactosidase (galac), xylosidase (xylo), N-acetyl-glucosaminidase (nag), phosphatase (phos), and sulfatase (sulf).