Effects of willow canopies on plant species performance in a low-alpine community
2002
Totland, O. | Esaete, J.
It is believed that abiotic, rather than biotic, factors are of paramount importance to the performance of plants in alpine and arctic habitats. This study examines how Salix lapponum affects 15 associated species by comparing individual growth and reproductive performance of adult plants growing inside and outside shrub canopies. The study also includes experimental removal of Salix lapponum shrubs, and measurements of shoot density of five species inside and outside intact canopies. Mean above-ground plant weight of nine species was significantly higher inside canopies compared to outside. Mean leaf number inside canopies was significantly higher for two species, and total seed number was significantly higher inside for one species. Mean leaf number was significantly lower inside canopies compared to outside for one species. Mean seed weight was significantly lower inside canopies for one species. Removal of Salix lapponum shrubs increased bulbil weight of Bistorta vivipara and seed number and plant weight of Euphrasia frigida. These results suggest that canopy removal relaxed competition. Shoot density was substantially higher outside canopies compared to inside for four species and slightly higher outside for one species. Soil moisture, soil organic content, soil pH, and temperature inside canopies were not significantly different from outside, whereas photosynthetically active radiation (PAR) was markedly reduced inside canopies. Increased growth inside canopies is likely a compensatory mechanism to decreased PAR, which enable plants inside canopies to achieve reproductive outputs that equals those on outside plants. The lower plant density inside canopies is probably caused by reduced germination and establishment possibilities there, due to reduced PAR and higher litter accumulation.
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