Abstract
Aims The relationship between biodiversity and ecosystem functioning has intrigued ecologists for several decades, but the effect of loss of a dominant species on community structure and functioning along a nutrient gradient remains poorly understood. The aim of this paper was to test the effect of a dominant species on community structure and function by conducting a species removal experiment along a fertilization gradient. Methods We removed the population of a dominant species (Elymus nutans) in a long-term fertilization field in an alpine meadow on the Tibetan Plateau, China. Univariate general linear models were used to evaluate the effects of fertilization and removal on above-ground vegetation characteristics, including photosynthetically active radiation in the understory, species richness, Shannon–Weiner diversity index, Simpson’s dominance index, above-ground biomass (including different functional groups) and seedling richness and density. Important Findings Results revealed that after two plant growing seasons, there was no significant effect of the removal of a dominant species on species richness and diversity of the remaining vegetation, but the biomass of forbs and seedling recruitment were significantly increased indicative of the potential for long-term effects. Moreover, removal had a large effect at high fertilization levels, but little effect when fertilization levels were low. Our studies indicated that community response to loss of a dominant species was mainly dependent on resource availability and the remaining functional group identities. We also found seedling recruitment was usually more sensitive to the influence of competition of dominant species than the established vegetation in the short term.
Highlights
We removed the population of a dominant species (Elymus nutans) in a long-term fertilization field in an alpine meadow on the Tibetan Plateau, China
The vegetation composition shifted from dominance initially by sedges and forbs, to being dominated by a single grass, E. nutans, which became increasingly dominant (F3, 7 = 1193.68, P < 0.001) and taller (F3, 7 = 27.26, P < 0.001) with fertilization (Table 1)
Increased dominance was mainly driven by the response of the dominant species (E. nutans) in our results (Table 1)
Summary
Fertilization can cause species diversity loss and a shift in species dominance and composition, and these changes further affect productivity, litter decomposition and seedling recruitment (Chapin et al 1998; Dickson et al 2014; Gross et al 2005).The magnitudes of the responses of species diversity and community productivity to fertilization appear to mainly depend on traits of dominant species, which is an important driver factor, both in the short term by affecting seedling recruitment and in the long term, by driving soil processes that regulate nutrient supply for other species (Clark et al 2007).Journal of Plant EcologyOver the past several decades, ecologists have focused on studies of ‘biodiversity–ecosystem functioning’, i.e. the relationship between species diversity and composition in an ecosystem and the functioning of this ecosystem (Balvanera et al 2006; Duffy 2009). Data predict that losses in species diversity will have a negative effect on ecosystem functioning, including productivity and soil nutrient cycling (Balvanera et al 2006; McLaren and Turkington 2010). The ‘mass ratio hypothesis’ proposed by Grime (1998) predicts that the influence of a species or functional group on ecosystem functioning or stability is proportional to their input to primary production. According to this hypothesis, the functioning of ecosystems is determined to a large extent by the traits of the dominant species. Removal experiments have been promoted for biodiversity–ecosystem functioning studies in natural communities (McLaren and Turkington 2010)
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