Abstract
Most plant biomass allocation studies have focused on allocation to shoots versus roots, and little is known about drivers of allocation for aboveground plant organs. We explored the drivers of within-and between-species variation of aboveground biomass allocation across a strong environmental resource gradient, i.e., a long-term chronosequence of 30 forested islands in northern Sweden across which soil fertility and plant productivity declines while light availability increases. For each of the three coexisting dominant understory dwarf shrub species on each island, we estimated the fraction of the total aboveground biomass produced year of sampling that was allocated to sexual reproduction (i.e., fruits), leaves and stems for each of two growing seasons, to determine how biomass allocation responded to the chronosequence at both the within-species and whole community levels. Against expectations, within-species allocation to fruits was least on less fertile islands, and allocation to leaves at the whole community level was greatest on intermediate islands. Consistent with expectations, different coexisting species showed contrasting allocation patterns, with the species that was best adapted for more fertile conditions allocating the most to vegetative organs, and with its allocation pattern showing the strongest response to the gradient. Our study suggests that co-existing dominant plant species can display highly contrasting biomass allocations to different aboveground organs within and across species in response to limiting environmental resources within the same plant community. Such knowledge is important for understanding how community assembly, trait spectra, and ecological processes driven by the plant community vary across environmental gradients and among contrasting ecosystems.
Highlights
Plants allocate resources to different organs and this allocation can vary greatly among both plant species and environmental conditions [1, 2]
The repeated split plot ANOVA showed that all three allocation variables (RA, SMF, LMF), and shoot turnover varied among species and year but not island size class, and were all affected by interactive effect of species by year and species by island size class (Table 1)
In 2012, interactive effects between species and island size class emerged because reproductive allocation (RA) was least for V. myrtillus on small islands and for V. vitis-idaea on intermediate islands, LMF was least for V. myrtillus on big islands and for V. vitis idaea on small islands, and SMF was highest for V. myrtillus on small islands and for the other two species on intermediate islands (Fig 1a–1c)
Summary
Plants allocate resources to different organs and this allocation can vary greatly among both plant species and environmental conditions [1, 2]. For aboveground, plants allocate resources to organs that provide different functions, including leaves, stems and reproductive structures [6, 7, 8, 9]. Allocation patterns between vegetative and reproductive organs may vary because of trade-offs between the need for carbon gain and the need to produce propagules to maintain future populations [7, 11]. Analysing different fractions of aboveground biomass (i.e. the proportion of total biomass produced allocated to stem (SMF), leaves (LMF) or reproductive organs (RA)) offers an objective way of linking plant biomass investment to different functions [1, 8] under contrasting environmental conditions
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