Variation in leaf and soil δ15N in diverse tree species in a lowland dipterocarp rainforest, Malaysia.
Tanaka-Oda, A., Kenzo, T., Inoue, Y., Yano, M., Koba, K., & Ichie, T. . 2015. Springer Berlin Heidelberg
Abstract
Key message Large variations in leaf δ15N in Bornean
tropical rainforest trees may indicate that various
tropical species have species-specific strategy for
nitrogen uptake under low soil nutrient conditions,
including root symbiotic microorganisms such as
ectomycorrhiza.
Lowland tropical rainforests in Southeast Asia
are characterized by high species diversity despite limited
soil nutrient conditions. The plant nitrogen isotope ratio
(δ15N) reflects plant uptake of soil nitrogen. We analyzed
d15N values and nitrogen content (N %) in leaves and roots
of 108 woody species with different types of symbiotic
microorganisms, of different life forms (emergent, canopy,
sub-canopy, understory, and canopy gap species), and from
different families in a Bornean lowland dipterocarp forest
to gain more insight into the diversity of nitrogen uptake
strategy in the rhizosphere. Leaf δ15N values in the species
studied varied largely from -7.2 to 5.0 %, which is
comparable to the values of known Asian trees including
temperate, sub-tropical, and tropical mountain forests. Leaf
δ15N also varied significantly among both life forms and
families, though the phylogenetically independent contrast (PIC) relationships were not statistically significant among
life form, family, and symbiotic types. Some families
showed specific leaf δ15N values; Dipterocarpaceae, the
dominant family in the canopy layer with symbiotic ectomycorrhiza
in Southeast Asia, had small intraspecific
variation and higher leaf δ15N values (0.03 %) compared
with species exhibiting arbuscular mycorrhiza, whereas
several families such as Burseraceae, Euphorbiaceae, and
Myrtaceae showed large interspecific variation in leaf δ15N
(e.g., from -7.2 to 5.0 % in Euphorbiaceae). These variations
suggest that tropical species may have family- or
species-specific strategy, such as root symbiotic microorganisms,
for nitrogen uptake under low-nutrient conditions
in tropical rainforests in Southeast Asia.
Key Words
Dipterocarpaceae, Nitrogen acquirement, Nitrogen stable isotope, Root symbiosis, Tropical rainforest
