Fertilization and litter effects on the functional group biomass, species diversity of plants, microbial biomass, and enzyme activity of two alpine meadow communities

Abstract

We conducted a field experiment in two alpine meadows to investigate the short-term effects of nitrogen enrichment and plant litter biomass on plant species richness, the percent cover of functional groups, soil microbial biomass, and enzyme activity in two alpine meadow communities. The addition of nitrogen fertilizer to experimental plots over two growing seasons increased plant production, as indicated by increases in both the living plant biomass and litter biomass in the Kobresia humilis meadow community. In contrast, fertilization had no significant effect on the amounts of living biomass and litter biomass in the K. tibetica meadow. The litter treatment results indicate that litter removal significantly increased the living biomass and decreased the litter biomass in the K. humilis meadow; however, litter-removal and litter-intact treatments had no impact on the amounts of living biomass and litter biomass in the K. tibetica meadow. Litter production depended on the degree of grass cover and was also influenced by nitrogen enrichment. The increase in plant biomass reflects a strong positive effect of nitrogen enrichment and litter removal on grasses in the K. humilis meadow. Neither fertilization nor litter removal had any impact on the grass biomass in the K. tibetica meadow. Sedge biomass was not significantly affected by either nutrient enrichment or litter removal in either alpine meadow community. The plant species richness decreased in the K. humilis meadow following nitrogen addition. In the K. humilis meadow, microbial biomass C increased significantly in response to the nitrogen enrichment and litter removal treatments. Enzyme activities differed depending on the enzyme and the different alpine meadow communities; in general, enzyme activities were higher in the upper soil layers (0-10 cm and 10-20 cm) than in the lower soil layers (20-40 cm). The amounts of living plant biomass and plant litter biomass in response to the different treatments of the two alpine meadow communities affected the soil microbial biomass C, soil organic C, and soil fertility. These results suggest that the original soil conditions, plant community composition, and community productivity are very important in regulating plant community productivity and microbial biomass and activity.

Urea addition and litter manipulation alter plant community and soil microbial community composition in a Kobresia humilis meadow

“…With the addition of urea N alpine meadow, the aboveground productivity and grass biomass increased [28,46]. These findings are inline with other studies where the addition of N enhanced the community productivity largely due to the increased availability of nutrients [46].…”

“…Four treatment combinations were used for each of the study sites: N addition (þN) with the litter removed (LR): þN þ LR, þN with the litter left intact (LI): þN þ LI, LI without N addition (ÀN): LIþ(ÀN), and LR with ÀN: LRþ(ÀN)[28].…”

Beyond species: functional diversity and the maintenance of ecological processes and services

“…The identity of the dominant functional group varied along gradients of resource availability. In contrast, N addition reduced species richness in alpine meadows, but alteration to community composition with nutrient supplementation depended upon levels of functional evenness and identity of functional dominants (Wang et al. 2010).…”

“…2010). Functionally diverse communities were prone to composition shifts and increased dominance with nutrient addition because they were more likely to contain a species with functional traits suited to exploitation of the added resource (Wang et al. 2010).…”

Functional Diversity: An Important Measure of Ecosystem Functioning

“…Light limitation can reduce species richness and species diversity, but the impact of it depends upon functional evenness of the species in the community i.e., light limitation can reduce species richness and diversity only if the microbial community consists of phototrophic cells in majority [17]. As environmental filters (such as light) act on functional traits, understanding the correspondence between abiotic factors and particular functional traits would help to predict which species from a regional pool could colonize and survive in the respective area [18].…”