Publication Date:
2006-05-01
Description:
We suggest that the net outcome of interactions between regenerating conifers and early seral deciduous species depends on trade-offs between competition and facilitation over time. Vegetation management treatments that dramatically reduce competitive effects of deciduous species may constrain the ability of conifers to optimize resource trade-offs (e.g., increased growth response to light at the expense of increased drought mortality), potentially affecting long-term productivity. In a 15-year study in southern interior British Columbia, we investigated whether lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) survival, growth, and resource availability differed among manipulated stand compositions, from pure pine stands to mixtures with native N2-fixing Sitka alder (Alnus viridis subsp. sinuata (Regel) Á. Löve & D. Löve) or herbs. We found that pine growth increases were sustained only in pure stands, where alder and herbs were completely removed, corresponding with short-term increases in light, soil and air temperature, and soil nitrate. However, this came at a significant cost to survival (through loss of protection from browsing, desiccation, and sun scald), as well as dramatic depletions in soil nitrogen mineralization over the longer term. Our results support a competitionfacilitation trade-off hypothesis, suggesting that treatment-imposed shifts in resource availability over time could negatively affect forest productivity.
Print ISSN:
0045-5067
Electronic ISSN:
1208-6037
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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