Changes in Pteridium aquilinum growth and phototoxicity following treatments with lime, sulphuric acid, wood ash, glyphosate and ammonium nitrate

The comparative effects of lime, sulphuric acid, wood ash, glyphosate and ammonium nitrate on Pteridium aquilinum (L.) Kuhn growth and development were evaluated in a Scots pine (Pinus sylvestris L.) clear-cut stand in south-east Sweden over a 4-year period. P. aquilinum growth was effectively controlled following the application of glyphosate, but the other treatments generally had little effect on growth in terms of shoot density and length. Shoot length was positively related to the number of shoots on plots treated with ammonium nitrate but negatively correlated with the number of P. aquilinum shoots found on wood ash-treated and control plots. In a bioassay aspen (Populus tremula L.) seedling emergence and pH were significantly lower in humus treated with sulphuric acid, glyphosate, ammonium nitrate and in untreated humus as compared with the humus treated with lime and wood ash. The negative effect of humus on emergence of aspen seedlings may be caused by phytotoxic compounds at a lower pH level. Forest regeneration might be performed with shade-tolerant species such as Norway spruce (Picea abies (L.) Karst.) planted beneath a thin canopy of trees to prevent the rapid increase of P. aquilinum.