Mining for natural resources has caused significant disturbance to natural ecosystems throughout the world. Successful restoration is dependent upon methods that encourage recovery by natural succession. Unfortunately, current U.S. land reclamation protocols have resulted in soil compaction with aggressive, non-native herbaceous groundcovers that impede the succession of native trees. To overcome this, methods such as deep soil ripping and plowing/disking were applied to a reclaimed mine site in Ohio, U.S.A. Plantings of pure American chestnut (Castanea dentata) and two putative blight-resistant chestnut hybrids (BC1F3 and BC2F3) were assessed. This study utilized a randomized block design, with a total of three replicated blocks, each containing a control and three soil treatments (100 seedlings per treatment, 400 per block, 1200 total) arranged as: (1) control plot, untreated and representative of reclamation policy, (2) plots plowed and disked to a depth of 30 cm, (3) plots cross-ripped to a depth of 1 m, and (4) the combination of deep soil ripping and plowed/disked. After 11 field seasons, tree height (m) and root collar diameter (cm) were measured and all trees were evaluated for natural chestnut blight infection. All woody plants located within 2 m2 circular quadrats around planted trees were identified to species.
Results/Conclusions
After 11 field seasons, the survival of chestnuts in plots that employed either ripping, or the combination of the two methods (70% and 68%, respectively) were significantly (P < 0.0001) greater than the plowed/disked (62%) or control plots (17%). Likewise, tree height responded similarly across the treatments and averaged 3.4 m, which was significantly taller than the chestnut trees in the control plots (2.3 m, P = 0.04). When heights among the different tree types were compared, BC1F3 hybrids were similar to the Pure American chestnuts (3.6 and 3.5 m, respectively), which were both significantly taller than the BC2F3 hybrids (3.2 m; P = 0.02). Both hybrid chestnut lines had significantly higher survival (66 and 71%) when compared to the pure American trees (61%, P = 0.03). Hybrid chestnuts also exhibited significantly less canker infection than the pure American lines (P < 0.0001). Vegetation community composition was similar among treatments with one difference, there were more native species sampled in plots that received a mechanical treatment (P = 0.05). In this study, planting methods promoted vigorous growth and native plant recruitment, which can be applied more broadly to other regions where anthropogenic disturbance creates soil conditions that hinder natural recovery.