TITLE:
Using Water Stable Isotopes to Trace Water Sources of Three Typical Japanese Tree Species under Heavy Rainfall Conditions
AUTHORS:
Qiqin Zhang, M. Larry Lopez C., Alexander C. Brandt, Jordi Voltas, Takeshi Nakatsuka, Mónica Aguilera
KEYWORDS:
High Precipitation, Water Use, Stable Isotopes, Xylem Water, Soil Water
JOURNAL NAME:
Open Journal of Forestry,
Vol.10 No.1,
December
6,
2019
ABSTRACT: Stable
isotopes of xylem water (18O and D) have been successfully used to
determine sources of soil water for plant transpiration, but mainly in
drought-prone environments. The water uptake strategies of three representative
tree species in Japan, namely cedar (Cryptomeria japonica), larch (Larix
kaempferi) and beech (Fagus crenata), were investigated using δ18O and δD of water (precipitation, soil and xylem), together with wood α-cellulose δ13C and δ18O,
along one growing season. The study was carried out in the research forest of
Yamagata University (Shonai region), a high precipitation area in Japan, which
exceeds 3000 mm per year. Precipitation water δ18O and δD
increased along the summer growing season, but oxygen and hydrogen isotopic
composition of soil water remained essentially unchanged. In general, xylem
water isotopes of cedar and larch followed the local meteoric water line, but
beech xylem water was decoupled from soil and precipitation values in July and
August. For this tree species, the xylem water isotopic records were more depleted than cedar and larch xylem water
isotopic values and the precipitation water isotopic records, indicating that
beech used more water from soil layers during July-August than the other two
species, which mainly used newly-fallen precipitation. Wood δ18O showed an opposite
seasonal trend to the one found for xylem water, likely because of leaf water
isotope enrichment, which was in turn controlled by seasonal transpiration
rate. The higher δ13C
values of cedar during summer suggested that this species had enhanced
water-use efficiency during the growing season compared with the deciduous
species larch and beech. Our results highlight different water use strategies
among forest tree species even in areas where the annual water balance is far
from limiting plant performance.