Experimental investigation of fertilization and irrigation effects on an alpine heath, Northwestern Caucasus, Russia.

We investigated the response of an alpine lichen heath plant community to an increase in soil nutrient and water availability. A 5-yr experiment - including additions of calcium, phosphorus, nitrogen, and nitrogen + phosphorus as well as irrigation - was conducted in northwestern Caucasus, Russia, at 2800 m above sea level. Number of plants and generative shoots per species were counted annually. The plant-community composition started to change during the second year of treatments. Plant density and flowering of the community is co-limited by nitrogen and phosphorus. Irrigation and calcium additions caused minimal changes. The total number of forb plants per square meter was not influenced by treatments, whereas the total number of graminoid plants slightly increased in response to P treatment and strongly increased in response to N + P treatment. Forbs responded to N and N + P treatments by an increase in the number of generative shoots. Individual species differed in their response to treatments. Only clonal species responded to experimental treatments, except for one annual nonclonal species, which increased its abundance in response to irrigation. Biodiversity estimated by the Shannon-Wiener index decreased under N + P treatment. Species number was not affected by any of the treatments. © 2005 Regents of the University of Colorado