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Abstract: Winter wheat is one of major grain crops in China. To scientifically map cropping patterns, it is very important to understand the area of its viable cultivation zone in China. Based on published data, geographical information, national climate data, and the MaxEnt model, the relationship between the distribution of the winter wheat cultivation zone and climate was established. The main indices controlling the distribution of the winter wheat cultivation zone were analyzed to reveal climatic suitability. The main controls on winter wheat distribution in China were: the negative accumulation of daily mean temperatures below 0°C during winter (i.e., negative accumulated temperature), annual mean extreme minimum temperatures, potential evapotranspiration, and annual precipitation. For winter wheat to safely survive the winter, the negative accumulated temperature should be higher than −700°C, and the annual mean extreme minimum temperature should be higher than −30°C. Climate suitability classification of the winter wheat cultivation zone was mapped, based on the MaxEnt probability distribution of winter wheat. Former studies indicated that the northeast boundary of the winter wheat cultivation zone is the south of Liaoning Province, and our study indicated that the northeast boundary of the winter wheat cultivation zone is the north of Heilongjiang Province; former studies indicated that the northwest boundary of the winter wheat cultivation zone is the south of Xinjiang Uygur Autonomous Region, and our study indicated that the northwest boundary of the winter wheat cultivation zone is the north of Xinjiang Uygur Autonomous Region. Our study describes a suitable winter wheat cultivation zone in China and the northern boundary of winter wheat cultivation, and it will be helpful for guiding the cultivation of Chinese winter wheat. Based on our climatic indices and their threshold determining the distribution of winter wheat, it will be helpful for gaining a scientific understanding of the effects of climate change. [Copyright &y& Elsevier]

Plant phenology models, especially leafing models, play critical roles in evaluating the impact of climate change on the primary production of temperate plants. Existing models based on temperature alone could not accurately simulate plant leafing in arid and semi-arid regions. The objective of the present study was to test the suitability of the existing temperature-based leafing models in arid and semi-arid regions, and to develop a temperature-precipitation based leafing model (TP), based on the long-term (i.e., 12-27 years) ground leafing observation data and meteorological data in Northeast China. The better simulation of leafing for all the plant species in Northeast China was given by TP with the fixed starting date (TPn) than with the parameterized starting date (TPm), which gave the smallest average root mean square error (RMSE) of 4.21 days. Tree leafing models were validated with independent data, and the coefficient of determination (R2) was greater than 0.60 in 75% of the estimates by TP and the spring warming model (SW) with the fixed starting date. The average RMSE of herb leafing simulated by TPn was 5.03 days, much lower than other models (>9.51 days), while the average R2 of TPn and TPm were 0.68 and 0.57, respectively, much higher than the other models (<0.22). It indicates that TPn is a universal model and more suitable for simulating leafing of trees and herbs than the prior models. Furthermore, water is an important factor determining herb leafing in arid and semi-arid temperate regions. [ABSTRACT FROM AUTHOR]

Estimates of forest vegetation carbon storage in China varied due to different methods used in the assessments. In this paper, we estimated the forest vegetation carbon storage from the Fourth Forest Inventory Data (FFID) in China using a modified volume-derived method. Results showed that total carbon storage and mean carbon density of forest vegetation in China were 3.8 Pg C (about 1.1% of the global vegetation carbon stock) and 41.32 Mg/ha, respectively. In addition, based on linear multiple regression equation and factor analysis method, we analyzed contributions of biotic and abiotic factors (including mean forest age, mean annual temperature, annual precipitation, and altitude) to forest carbon storage. Our results indicated that forest vegetation carbon storage was more sensitive to changes of mean annual temperature than other factors, suggesting that global warming would seriously affect the forest carbon storage. [ABSTRACT FROM AUTHOR]

Water deficit and high temperature often occur simultaneously, but their effects on plants are usually investigated separately. The aim of this study was to test how interactions between water stress and nocturnal warming affect carbon allocation in the perennial grass,Leymus chinensis. Plant biomass, dry mass allocation,14C partitioning and carbon isotope composition (δ13C) were measured. Severe and extreme water stress during nocturnal warming decreased the allocation of dry mass and14C partitioning below ground to the roots, but moderate water stress significantly increased the below-ground allocation of dry mass and 14C, especially at the lower night temperature. The δ13C values were more positive at day/night temperatures of 30/20°C than at 30/25°C, and greater in the roots than in the leaves. By plotting the δ13C values of the leaves against the δ13C values of the roots, the slopes of regressions were steeper at low than at high night temperature, also indicating that nocturnal warming reduces carbon allocation below ground to the roots. The results suggest that nocturnal warming may weaken acclimation during water stress in this species by regulating carbon allocation between source and sink organs. [ABSTRACT FROM AUTHOR]

Controlled experiment of Leymus chinensis seedlings grown in the environmental growth chambers at 3 soil moisture levels and 3 temperature levels was conducted in order to improve the understanding how leaf photosynthetic parameters will respond to climatic change. The results indicated that soil drought and high temperature decreased the photochemical efficiency of photosystem ( Fv/ Fm), the overall photochemical quantum yield of PSII(yield), the coefficient of photochemical fluorescence quenching(qp). but increased the coefficient of non-photochemical fluorescence quenching ( qN). Severe soil drought would decrease Fv/ Fm and yield by 3.12% and 37.04% under 26°C condition, respectively, and 6.60% and 73.33% under 32°C condition, respectively, suggesting that higher temperature may enhance the negative effects of soil drought. All the soil drought treatments resulted in the decline in leaf nitrogen content. There was no significant effect of temperature on leaf nitrogen level, but higher temperature significantly reduced the root nitrogen content and the ratio of root nitrogen to leaf nitrogen, indicating the different strategies of adaptation to soil drought and temperature. It was also implied that higher temperature would enhance the effect of sod drought on leaf photosynthetic capacity, decrease the adaptability of Leymus chinensis to drought. [ABSTRACT FROM AUTHOR]