Long-term effects of 7-year warming experiment in the field on leaf hydraulic and economic traits of subtropical tree species

Rising
temperature associated with climate change may have substantial impacts on
forest tree functions. We conducted a 7-year
warming experiment in sub-tropical China by translocating important native
forest tree species (Machilas breviflora, Syzygium
rehderianum, Schima superba and Itea chinensis) from cooler high-elevation-sites (600 m) to 1-2 ℃
warmer low-elevation-sites (300 and 30 m) to investigate warming effects on
leaf hydraulic and economic traits. Here, we report data from the last three
years (Years 5-7) of the experiment. Warming
increased leaf hydraulic conductance (Kleaf) of S. superba to meet the higher evaporative
demand. M. breviflora (300 m), S. rehderianum, S. superba and I. chinensis (300
m and 30 m) exhibited higher area-based
and mass-based maximum photosynthetic rates (Aa and Am,
respectively) related to increasing stomatal conductance
(gs) and stomatal density in the wet season, which led to
rapid growth; however, we observed decreased growth of M. breviflora at 30 m due to lower stomatal density and decreased Aa
in the wet season. Warming increased photosynthetic nitrogen use efficiency
(PNUE) and photosynthetic phosphorus use efficiency (PPUE), but reduced leaf
dry mass per unit area (LMA) due to lower leaf thickness, suggesting that these
tree species allocated more
resources into upregulating photosynthesis rather than into structural
investment. Our findings
highlight that there was trait variation in
the capacity of trees to acclimate to warmer temperatures such that I. chinensis may benefit from warming,
but S. superba may be negatively
influenced by warming in future climates.