Synergistic regulation between leaf N and P on Vcmax and Jmax of species
in subtropical karst and non-karst forests of China
Abstract
Gas exchange capacity of leaves is mainly restricted by the content of N
and P and environmental factors. However, the effects of interaction
between N and P and environmental factors on photosynthetic capacity in
subtropical tree species remain unclear. We measured the gas exchange
parameters (25℃ maximum carboxylation rate [Vcmax,25], and 25℃
maximum electron transport rates [Jmax,25]) and the chemical
properties of leaves (leaf N, leaf P and N:P) in 9 local dominant
species in the subtropical non-karst and karst regions of southwest
China. Environmental factors (temperature [Temp] and soil moisture
content [SMC]) of the study site were also monitored at the same
time. We found that P restriction is common in different research sites.
The results of the mixed linear model show that with the increase of
leaf N content of karst species, the sensitivity of Vcmax,25 to leaf P
increased significantly, and there was a significant interaction of N×P
(P < 0.001). Non-karst species tend to N×SMC interaction (P =
0.04). The difference in N×P interaction on gas exchange parameters
between non-karst and karst species might result from the decoupling
phenomenon of N and P caused by climate change. Factors such as N
sedimentation and soil P loss aggravate the N:P imbalance and lead to
the decoupling effect between N and P elements, and continuously weaken
the influence of N×P interaction on plant Vcmax and Jmax.