The Diagnosis and Recommendation Integrated System (DRIS) has been used successfully to diagnose the nutrition of many crops. Some practioners, however, cite problems in applying DRIS to certain crops. Among the problems are: identifying a suitable expression of yield, maintaining symmetry in DRIS index equations, and dealing with extremely variable micronutrients. The purpose of this study was to resolve problems as they were encountered in applying DRIS to Fraser fir (Abies fraseri [Pursh] Poir.) Christmas trees. A total of 107 Fraser fir plantations were sampled for foliage, soil, and diameter measurements. Foliage was analyzed for N, P, K, Ca, Mg, Zn, Mn, Fe, Cu, and B. Age‐adjusted diameter was used successfully as the growth‐response variable. The DRIS symmetry was maintained by including nonsignificant ratios, but setting their standardization functions equal to zero. This reduced the influence of the nondiscriminating nutrient ratios on the DRIS analysis. Norm ranges, as opposed to discrete norms, were used successfully to correct for the influence of extremely variable micronutrient ratios on the DRIS analysis. This combination of adaptations and modifications of DRIS should greatly enhance its use for this tree crop.
Establishing adequate advanced oak reproduction prior to final overstory removal is crucial for regenerating oak forests in the eastern U.S. Many management approaches exist to this end, but benefits associated with any individual technique can depend on the suite of techniques employed and the geographic location. At four mixed-hardwood upland forest sites in central and southern Indiana, we tested factorial combinations of deer fencing, controlled-release fertilization, and various silvicultural techniques (midstory removal, crown thinning, and a shelterwood establishment cut) for promoting the growth and survival of underplanted red oak seedlings. Crown thinning resulted in slow growth and low survival. Midstory removal and the shelterwood establishment cut were nearly equally effective for promoting seedling growth. Seedling survival was strongly influenced by fencing, and differences in survival between silvicultural treatments were minimal when fencing was employed. Fertilization had minimal effects overall, only increasing the probability that unfenced seedlings were in competitive positions relative to surrounding vegetation. We suggest that underplanting oak seedlings can augment natural reproduction, but the practice should be accompanied by a combination of midstory removal and fencing, at a minimum, for adequate growth and survival.
Invasion of non-native shrubs comprises a serious economic and ecological problem in North American forests. Prescribed grazing by goats may offer an effective alternative to traditional methods of control, but has received little study in forest settings. In a 5-year field experiment, we varied the stocking of goats and number of grazing periods to determine effects of prescribed grazing on both invasive shrubs and native plant species. Specifically, we examined how varied stocking levels and grazing periods affect: (1) the cover and height of invasive shrub and native woody species (2) the cover and diversity of herbaceous species, and (3) the density of native tree seedlings. Data were analyzed with linear mixed-effects models. We found that prescribed grazing by goats significantly reduced the cover and height of invasive shrubs, regardless of goat stocking or duration. Generally, the greatest reductions in invasive shrub cover occurred in treatments with two grazing periods, regardless of goat stocking. While we observed mostly neutral or positive effects on the herbaceous layer, all grazing treatments reduced the cover and height of native understory woody species. While changes were not significant, we observed a general decline in the aggregate height of native tree species regeneration. Our results suggest that prescribed grazing by goats provides an effective and environmentally friendly treatment for heavy invasions of non-native shrubs such as Rosa multiflora, but grazing needs to be followed by focused mechanical or chemical treatments to maintain control while allowing the regeneration of native tree species.
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