Some Growth And Chlorophyll Fluorescence Parameters Of Black And Hybrid Poplar Clones Under Water Stress

The effects of water stress on some growth and chlorophyll a fluorescence parameters were investigated in two native black poplar (Populus nigra L.) clones (Kocabey and Gazi) and in two hybrid poplar (Populus x euramericana (Dode) Guinier) clones (I-214 and I-45/51) to determine which among the four clones is the best adapted to water-stress conditions. The potted seedlings were grown under three watering regimes. As a result of the applied watering regimes, the predawn water potential (psi(pd)) of seedlings was maintained at about -0.3, -0.9, and -1.6 MPa in control, moderate, and severe water-stress treatments during the experiment, respectively. Drought treatment had significant effects on the morphology and growth characteristics of the clones but had generally insignificant effects on survival and the photochemical activity of photosystem II (PSII). Results obtained from the present study demonstrate that I-214 was the most successful in terms of its higher root/shoot ratio (R-s), maximum fluorescence yield (F-m), maximum quantum efficiency of PSII (F-v/F-m) values, and lower number of leaves among the examined four poplar clones under drought stress conditions. Consequently, the I-214 poplar clone may have the potential to be used in drought areas.WoSScopu

A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests

Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are potential increases in tree mortality associated with climate-induced physiological stress and interactions with other climate-mediated processes such as insect outbreaks and wildfire. Despite this risk, existing projections of tree mortality are based on models that lack functionally realistic mortality mechanisms, and there has been no attempt to track observations of climate-driven tree mortality globally. Here we present the first global assessment of recent tree mortality attributed to drought and heat stress. Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world\u27s forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited. This further suggests risks to ecosystem services, including the loss of sequestered forest carbon and associated atmospheric feedbacks. Our review also identifies key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system. Overall, our review reveals the potential for amplified tree mortality due to drought and heat in forests worldwide