These results challenge the idea that nitrogen availability and a severe climate limit the rate of plant and microbial succession in cold-arid regions and will inform conservation efforts to mitigate the effects of global change on these fragile and threatened ecosystems. We also show that phosphorus addition greatly accelerates the rate of succession for plants and for microbial phototrophs, even at the most extreme deglaciating site at over 5000 meters above sea level in the Andes of arid southern Peru. We combine field and microcosm studies of both plant and microbial primary producers and show that phosphorus, not nitrogen, is the nutrient most limiting to the earliest stages of primary succession along glacial chronosequences in the Central Andes and central Alaska. Global warming is now causing rapid glacial retreat even in inland areas with cold, dry climates, areas where ecological succession has not been adequately studied. The information provided by using this approach can increase our understanding of the earliest stages of ecosystem development and may help inform strategies for the reclamation of disturbed arid ecosystems by identifying potential limiting nutrients.Ĭurrent models of ecosystem development hold that low nitrogen availability limits the earliest stages of primary succession, but these models were developed from studies conducted in areas with temperate or wet climates. By contrast, nitrogen additions had no significant effect on the growth of microbial phototrophs, and all nutrient additions suppressed the growth of early successional mosses.Ĭonclusions: We propose that the method described here offers a valuable tool for assessing the nature of nutrient limitation of photosynthetic organisms in early successional and desert ecosystems. Results: Fertilization with phosphorus significantly increased the growth rate and final percentage cover, and decreased the lag time for growth of cyanobacterial and algal communities in recently deglaciated soils. Methods: We modified the point–intercept method used in plant ecology to quantify the spread of cyanobacteria, algae and mosses on the soil surface in response to additions of nitrogen and phosphorus. We used the new method to test the hypothesis that phosphorus limits the growth of crusts in newly deglaciated soils of the high Andes. Little is known about the factors that limit the growth of these communities, especially during early stages of primary succession or following disturbance.Īims: Our main goal was to develop a method to study nutrient limitations of crust growth in laboratory microcosms. Background: Photosynthetic crust communities are important to the functioning of many desert and early successional ecosystems.
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