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Dryad

Plant trait responses to variation in N and P availability

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May 01, 2023 version files 119.50 KB

Abstract

  1. Global change drivers such as eutrophication and plant invasions will create novel environments for many plant species. Through adaptive trait plasticity plants may maintain their performance under these novel conditions and may outcompete those showing low adaptive trait plasticity. In a greenhouse study, we determined if plasticity in traits is adaptive or maladaptive in endangered, non-endangered and invasive plant species in response to variation of nitrogen (N) and phosphorus (P) availability (N:P ratios 1.7, 15 and 135) and whether plastic trait responses are adaptive and/or costly for fitness (i.e. biomass).
  2. Species choice comprised 17 species from three functional groups (legumes, non-legume forbs and grasses), either classified as endangered, non-endangered or invasive. After two months plants were harvested and nine traits related to carbon assimilation and nutrient uptake were measured (leaf area, SLA, LDMC, SPAD, RMR, root length, SRL, root surface area and PME activity).
  3. We found more traits responding plastically to variation in P than in N. Plasticity only created costs when P was varied. Plasticity in traits was mostly adaptively neutral towards fitness, with plasticity in three traits being similarly adaptive across all species groups: SPAD (as a measure of chlorophyll content, adaptive to N and P limitation), leaf area and root surface area (adaptive to P limitation). We found little differences in trait plasticity between endangered, non-endangered and invasive species.
  4. Synthesis. Along a gradient from N limitation, balanced N:P supply and P limitation we found that the type of fluctuating nutrient (i.e. if N or P is varied) is decisive for the adaptive value of a trait. Variation in P availability (from balanced supply to P limitation) created both a stronger reduction in fitness as well as created plasticity costs in more traits than variation in N availability (from balanced supply to N limitation). However, the patterns observed in our study may change if nutrient availability is altered, either by nutrient inputs or by a shift in nutrient availabilities, e.g. by decreasing N input as foreseen by European Legislation, but without simultaneously decreasing P input.