Drought, heat, and their combined stress reduce the productivity
and alter the photosynthetic characteristics of different alpine meadow
plants
Li Ma1,4, Zhonghua Zhang1,4,
Bingrong Zhou2, Manhou Xu3, Huakun
Zhou1
(1Northwest Plateau Institute of Biology, Chinese
Academy of Sciences, Key Laboratory of Cold Regions Restoration Ecology,
Xining, Qinghai Province 810008, China; 2The Qinghai
Institute of Meteorological Science, Xining, Qinghai Province 810001,
China; 3Taiyuan Normal University, Jinzhong, Shanxi
Province 030619, China ; 4University of Chinese
Academy of Sciences, Beijing 100049, China)
Correspondence: Huakun Zhou, Northwest Institute of Plateau Biology,
Chinese Academy of Sciences, Xining, China. Emails:
hkzhou@nwipb.cas.cn
Abstract: Alpine meadow plants, which are adapted to humid and
cold environments, are more sensitive to environmental factors such as
drought and high temperatures. However, excluding species competition,
the physiological responses of individual alpine meadow species to
drought and heat stress remain unclear. In this study, four
representative species of typical functional groups in an alpine meadow
of the Qinghai-Tibet Plateau were selected as experimental materials.
Heat (H1, H2), drought (D1, D2), and combined heat and drought stress
(D1H1, D2H2) treatments were implemented to reveal the physiological
characteristics’ response to a constant drought and heat environment.
Our results showed that the leaf water content (LWC) of Kobresia
humilis and Poa annua increased significantly under heat stress
and the compound heat and drought stress (P <0.05).
Additionally, the aboveground biomass (AGB) of Oxytropis
ochrocephala and Saussurea pulchra decreased significantly under
compound stress (P <0.05). The response patterns of the
net photosynthetic rate (Pn) and transpiration rate (Tr) of K.
humilis and P. annua under various stress treatments were
similar; as were those of O. ochrocephala and S. pulchra .
The stomatal conductance (Gs) variation in K. humilis, P.
annua, O. ochrocephala , and S. pulchra were the same under three
kinds of stress treatments. The photosynthetic characteristics were more
sensitive to the effects of composite than of single factors. The
drought × heat × species treatment had a significant influence on
various indexes except on height and the belowground biomass
(P <0.01). Within a certain range, daytime temperature
(DT) promoted the height and increased the LWC of the plants, while it
inhibited their AGB and intercellular CO2 concentration.
The Pn, Tr, and Gs were more sensitive to soil moisture than to DT. Our
results help improve understanding of the physiological response
regularity of representative alpine meadow plant species to continuous
drought and high temperature conditions.
Keywords: alpine meadow, drought stress, heat stress,
productivity, photosynthetic characteristics