Data from: Leaf functional traits predict timing of nutrient resorption and carbon depletion in deciduous subarctic plants

Resorption of key elements promotes their conservation in plants in
nutrient-poor ecosystems. In seasonal environments, the timing of
resorption is expected to influence resorption efficiency and plant
fitness due to the trade-off between maximizing photosynthetic carbon gain
by late resorption and minimizing frost risks and nutrient loss by early
resorption. Here, we hypothesize that (1) these alternative strategies
with respect to the timing of element resorption both occur among
summergreen species; (2) deciduous woody plants favour delayed resorption
while herbaceous species benefit from gradual, early-onset resorption; (3)
this pattern is part of a more general relationship in which species with
conservative resource economic traits have more delayed resorption. We
measured nitrogen (N), phosphorus (P) and carbon (C) contents of mature,
senescing and senesced leaves of 22 predominant plant species across four
types of ecosystems in a subarctic region. We then calculated timing of
resorption as the Julian calendar day of 50% of element resorption (T50),
and examined its relationship with plant functional types and leaf
resource economic traits (leaf mass per area [LMA], leaf C, N and P
contents). The timing of N resorption in subarctic plants ranged from day
213 to 254, while the timing of P resorption ranged from day 211 to 261
and of C from day 214 to 260 across species. On average, the resorption of
N and P and depletion of C were 13, 12 and 19 days respectively earlier in
herbaceous plants than in woody ones. For all the three elements, T50 of
plants decreased significantly with increasing acquisitive economic
traits. Synthesis As hypothesized, we found that (1) both
“steady-and-slow” and “late-and-fast” strategies of resorption timing
co-occurred in a subarctic flora; consistent with these two strategies,
herbaceous plants resorbed nutrients and carbon earlier than deciduous
woody species; (2) relevant functional traits representing resource
conservation were positively and linearly related to the timing of
nutrient resorption and carbon depletion. These findings for element
resorption timing have important implications for functional changes in
the vegetation composition of seasonal regions in response to temperature
fluctuations in a changing climate.