Low-Altitude Boundary of Abies faxoniana Is More Susceptible to Long-Term Open-Top Chamber Warming in the Eastern Tibetan Plateau

With global climate change, for evaluating warming effect on subalpine forest distribution, the substantial effects of long-term warming on tree growth and soil nutrients need to be explored. In this study, we focused on different responses in the boundaries of trees and soils to warming. Using the open-top chamber (OTC), a 10-year artificial warming experiment was conducted to evaluate the impacts of warming on Abies faxoniana at three different altitudes. We determined metabolites and nutrient concentrations in needles of A. faxoniana and characterized the soil chemistries. Many kinds of sugars, amino acids, and organic acids showed higher contents at high altitude (3,500 m) compared with low altitude (2,600 m), which could have been due to the temperature differences. Warming significantly decreased needle sugar and amino acid concentrations at high altitude but increased them at low altitude. These results indicated contrasting physiological and metabolic responses of A. faxoniana to long-term warming at different altitudes. Furthermore, we found that OTC warming significantly increased the concentrations of soil extractable sodium, aluminum (Al), and manganese (Mn), while decreased potassium (K) and phosphorus (P) concentrations and pH values at low altitude rather than at middle (3,000 m) or high altitude. The soil carbon and nitrogen contents were increased only at the middle altitude. In A. faxoniana at low altitudes, more mineral nutrients iron, K, and P were demand, and a mass of Al, Mn, and zinc was accumulated under warming. Soil P limitation and heavy metals accumulation are disadvantageous for trees at low altitudes with warming. Therefore, compared with high altitudes, A. faxoniana growing at low boundary in alpine regions is expected to be more susceptible to warming.

Performance of promising rice varieties under ambient and elevated temperature regimes

Open top chamber system was designed for undertaking research into rice crop response to increased temperature during rainy season at Regional Agricultural Research Station (RARS), Khajura, Banke in 2018. With the objective of determining the efficacy of the chamber system and to generate possible differences in climate which could alter plant response between ambient and chamber system, 5 different rice varieties (Radha-4, Sukhkhadhan-3, Sukhkhadhan-2, IR83383-G-B-141-1 and IR87751-20-4-4-2) with three temperature conditions were used: ambient condition, open top chamber with 1.2m height enclosed from base with plastic sheet and open top chamber with 1.5m height enclosed from base with plastic sheet. With 3.1°c higher temperature Sukhkhadhan-2 significantly (p value= 0.0199) produced higher grain yield 4.33 t/ha under chamber condition in contrast to open field (2.93 t/ha) as well as significantly (p value=0.0175) higher biomass yield 13.62 t/ha under elevated temperature. Also, Sukhkhadhan-2 significantly (p value=0.0012) attained maximum height (86.99 cm) under chamber condition compared to open field (73.06 cm) during harvest. Statistical analysis showed no significant difference for number of tillers per hill during maturity stage. Significantly sukhkhadhan-3 (p value=0.02994) showed longer panicle length 25.7cm under chamber than normal field condition (23.74 cm). In addition, Radha- 4 significantly (p value=0.03823) produced more filled grains per panicle (169) under chamber conditions than ambient condition (112). The consideration of crop variety is a good adoption measure to minimize incidence of elevated temperature in farming system.

Open top chamber microclimate may limit photosynthetic processes in Antarctic lichen: Case study from King George Island, Antarctica

Long-term manipulated warming experiments using the open top chamber (OTC) approach tend to mimick the future climate and predict the changes in photosynthesis and production of vegetation under globally changed climate. In Antarctica, several long-term experiments are carried out recently. Here we report to the lichens grown in OTCs installed at the Fildes Peninsula (King George Island). The field study compares primary photochemical processes of photosynthesis in Antarctic lichen Placopsis antarctica grown for one year in OTC and compared to outside plot (control). We measured effective quantum yield of photosystem II (ΦPSII) of green algae part of thallus in 10 min. interval for 12 days. We examined the responses of diurnal ΦPSII to PAR in relation to environmental factors through continuous 12-d-long monitoring of chlorophyll fluorescence parameters ΦPSII in particular. Daily courses of ΦPSII and photosynthetic electron transport rate (ETR) to photosynthetically active radiation (PAR) and hydration state of thallus have been assumed to reflect changes in physiological status of P. antarctica in changing Antarctic environment. The data indicate that OTC microenvironment may lead to partial limitation of photosynthetic processes in P. antarctica during austral summer season. The limitation is caused by accelerated dehydration of thallus in OTC compared to the outside generally colder control plot, and thus shortened physiologically active period of lichens in OTC.