Abstract
In biodiversity experiments based on seeded experimental communities, species richness and species composition exert a strong influence on canopy structure and can lead to an improved use of aboveground resources. In this study, we want to explore whether these findings are applicable to agriculturally managed permanent grassland. Vertical layered profiles of biomass, leaf area (LA) and light intensity were measured in a removal-type biodiversity experiment (GrassMan) to compare the canopy structure in grassland vegetation of different plant species composition (called sward types). Additionally, the altered sward types were subjected to four different management regimes by a combination of the factors fertilization (unfertilized, NPK fertilized) and cutting frequency (one late cut or three cuts). In spite of large compositional differences (ratio grasses : non-leguminous forbs : leguminous forbs ranging from 93 : 7 : 0 to 39 : 52 : 9), the vegetation of the same management regime hardly differed in its canopy structure, whereas the different management regimes led to distinct vertical profiles in the vegetation. However, the allocation of biomass in response to cutting and fertilization differed among the sward types. Vegetation dominated by grasses was denser and had more LA when fertilized compared with vegetation rich in dicots which merely grew taller. In functionally more diverse vegetation, light interception was not increased compared with vegetation consisting of more than 90 % of grasses in terms of biomass. Management had a much stronger influence on structure and light interception than plant species composition in this grassland experiment.
Highlights
Canopy structure, the 3D arrangement of all aboveground plant components in space, is quite diverse in grasslands, despite their relatively low canopy height compared with woody vegetation (Korner 1994)
The botanical and functional composition of the three sward types showed a distinct variation in the buds and tillers per square metre (Table 2)
The bud numbers of legumes and non-leguminous forbs averaged across all cutting and fertilization levels differed significantly among the sward types (t(20, a) ≥ 2.853, P ≤ 0.0098, linear contrasts in LM and GLS), except for the May harvest, when legume bud numbers were almost equal in the control vegetation (Co)- and – Mon-swards
Summary
The 3D arrangement of all aboveground plant components in space, is quite diverse in grasslands, despite their relatively low canopy height compared with woody vegetation (Korner 1994). The determinants of canopy structure in permanent grasslands have been the subject of many scientific studies. The density, total plant height and vertical distribution of leaf area (LA) and biomass in a grassland canopy are influenced by water and nutrient content of the soil as well as by the frequency and type of biomass removal (pasture vs meadow) (Werger et al 1986; Mitchley and Willems 1995; Liira and Zobel 2000; Lienin and Kleyer 2012). Research on the leaf area index (LAI) of single species has been conducted (Sheehy and Cooper 1973; Sheehy and Peacock 1977; Haase et al 1999; Cheng et al 2009) with early studies by Brougham (1958) on LAI and light interception, emphasizing the importance of different leaf angles in a grassland canopy
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