Zhihua Pan

Climate change and its effect on reference crop evapotranspiration in central and western Inner Mongolia during 1961–2009

Water resource is one of the major constraints to agricultural production in central and western Inner Mongolia, where are characteristic by arid and semi-arid climate. Reference crop evapotranspiration (ET0) is an important part of water cycle in agricultural ecosystem, which has a direct effect on crop growth and yield. The implications of climate change on ET0 are of high importance for agriculture regarding water management and irrigation scheduling. The aim of this study was to analyze the variations in climate and its effect on ET0 in central and western Inner Mongolia over the period 1961 to 2009. For this purpose, data in ten meteorological stations across study area were collected and the FAO Penman-Monteith 56 method was used. Results showed that the average temperature, maximum temperature and minimum temperature increased by 0.49°C, 0.31°C and 0.70°C per decade during 1961–2009, respectively. In comparison, the daily temperature range decreased by 0.38°C per decade. The air relative humidity, sunshine hour, and 10-m wind speed decreased generally by 0.58%, 40.11 h, and 0.35 m/s per decade, respectively. Annual mean ET0 decreased significantly at a rate of 12.2 mm per decade over the periods, this was mainly due to the decrease in wind speed in the study area. The decrease in wind speed may balance the effect of the increase in air temperature on ET0. Variations in spatial distribution of ET0 and its main controlling factor were also detected among ten stations. Our results suggested that spatial and temporal distribution of ET0 should be considered regarding the optimization of water resource management for agriculture in central and western Inner Mongolia under foreseen climate change.

The influence of nitrogen fertiliser rate and crop rotation on soil methane flux in rain-fed potato fields in Wuchuan County, China

As one of the important greenhouse gases, the characteristics and principles of methane exchange characteristics in cultivated lands have become hot topics in current climate change research. This study examines the influences of nitrogen fertilisation, temperature and soil water content on methane exchange characteristic and methane exchange functional gene-pmoA gene abundance based on experimental observations of methane exchange fluxes using the static chamber-gas chromatographic method and measurements of methanotroph gene copy numbers in three growing periods by real-time PCR in rain-fed potato fields. The results indicate that the rain-fed potato fields were a CH4 sink with an average annual methane absorption (negative emission) of 940.8±103.2 g CH4-C/ha/year. The cumulative methane absorption first exhibited flat and subsequently increasing trend with the increase of nitrogen fertilisation from 0~135 kg N·ha(-1). Methane cumulative absorption significantly increased with the increase of temperature when temperatures were below 19.6 °C. Methane oxidation capacity (methanotroph pmoA gene copy numbers) showed an increasing and subsequently decreasing trend with the increase of soil moisture. Crop rotation was observed to increase the methane absorption in rain-fed potato fields and nearly one time higher than that under continuous cropping. A mechanism concept model of the methane exchange in rain-fed potato fields was advanced in this paper.

Coincidence of variation in potato yield and climate in northern China

Understanding the effects of climate change on crops is vital for food security. We aimed to characterise the coincidence of yield variations with weather variable for potato in northern China using long-term datasets. Daily climate variables obtained from 607 meteorological stations from 1961 to 2014, detailed field experimental data for the period of 1982 to 2012 in northern China, and multivariate linear statistical model were used in this study. In particular, the first difference method was used to disentangle the contributions of climate change to potato yield. We concluded that during the potato growing, the average daily, maximum and minimum temperatures significantly increased by 0.23°C per decade, 0.20°C per decade and 0.36°C per decade from 1961 to 2014 in northern China, respectively. However, average total radiation, total annual precipitation and potential evapotranspiration from April to September all exhibited downward trends, but the variation of evapotranspiration (-9.99mm per decade) was greater than that of precipitation (-2.65mm per decade). The key climatic factors limiting potato yields in northern China over the past 30years at a regional scale were diurnal temperature range, precipitation, radiation and ET0. The potato yield in northern China was the most sensitive to variation of the diurnal temperature range followed by radiation, precipitation and reference crop evapotranspiration (ET0). Specifically, when the diurnal temperature range decreased 1°C, the potato yield increased 543.9kg·ha-1. When the total radiation decreased 1MJ·m2, the potato yield increased 63.8kg·ha-1. When the ET0 decreased 1mm, the potato yield increased 62.7kg·ha-1. When the precipitation increased 1mm, the potato yield increased 62.9kg·ha-1. A regression model describing the combined effects of different climate variables on potato yield in northern China was established.

Impact of climate change on maize potential productivity and the potential productivity gap in southwest China

The impact of climate change on maize potential productivity and the potential productivity gap in Southwest China (SWC) are investigated in this paper. We analyze the impact of climate change on the photosynthetic, light-temperature, and climatic potential productivity of maize and their gaps in SWC, by using a crop growth dynamics statistical method. During the maize growing season from 1961 to 2010, minimum temperature increased by 0.20°C per decade (p < 0.01) across SWC. The largest increases in average and minimum temperatures were observed mostly in areas of Yunnan Province. Growing season average sunshine hours decreased by 0.2 h day−1 per decade (p < 0.01) and total precipitation showed an insignificant decreasing trend across SWC. Photosynthetic potential productivity decreased by 298 kg ha-1 per decade (p < 0.05). Both light-temperature and climatic potential productivity decreased (p < 0.05) in the northeast of SWC, whereas they increased (p < 0.05) in the southwest of SWC. The gap between light-temperature and climatic potential productivity varied from 12 to 2729 kg ha−1, with the high value areas centered in northern and southwestern SWC. Climatic productivity of these areas reached only 10%–24% of the light-temperature potential productivity, suggesting that there is great potential to increase the maize potential yield by improving water management in these areas. In particular, the gap has become larger in the most recent 10 years. Sensitivity analysis shows that the climatic potential productivity of maize is most sensitive to changes in temperature in SWC. The findings of this study are helpful for quantification of irrigation water requirements so as to achieve maximum yield potentials in SWC.

Comparison of the impacts of climate change on potential productivity of different staple crops in the agro-pastoral ecotone of North China

The aim of this study is to compare the impacts of climate change on the potential productivity and potential productivity gaps of sunflower (Helianthus annuus), potato (Solanum tuberosum), and spring wheat (Triticumaestivum Linn) in the agro-pastoral ecotone (APE) of North China. A crop growth dynamics statistical method was used to calculate the potential productivity affected by light, temperature, precipitation, and soil fertility. The growing season average temperature increased by 0.47, 0.48, and 0.52°C per decade (p < 0.05) for sunflower, potato, and spring wheat, respectively, from 1981 to 2010. Meanwhile, the growing season solar radiation showed a decreasing trend (p < 0.05) and the growing season precipitation changed non-significantly across APE. The light–temperature potential productivity increased by 4.48% per decade for sunflower but decreased by 1.58% and 0.59% per decade for potato and spring wheat. The climate–soil potential productivity reached only 31.20%, 27.79%, and 20.62% of the light–temperature potential productivity for sunflower, potato, and spring wheat, respectively. The gaps between the light–temperature and climate–soil potential productivity increased by 6.41%, 0.97%, and 1.29% per decade for sunflower, potato, and spring wheat, respectively. The increasing suitability of the climate for sunflower suggested that the sown area of sunflower should be increased compared with potato and spring wheat in APE under future climate warming.

A quantitative method for risk assessment of agriculture due to climate change

Climate change has greatly affected agriculture. Agriculture is facing increasing risks as its sensitivity and vulnerability to climate change. Scientific assessment of climate change-induced agricultural risks could help to actively deal with climate change and ensure food security. However, quantitative assessment of risk is a difficult issue. Here, based on the IPCC assessment reports, a quantitative method for risk assessment of agriculture due to climate change is proposed. Risk is described as the product of the degree of loss and its probability of occurrence. The degree of loss can be expressed by the yield change amplitude. The probability of occurrence can be calculated by the new concept of climate change effect-accumulated frequency (CCEAF). Specific steps of this assessment method are suggested. This method is determined feasible and practical by using the spring wheat in Wuchuan County of Inner Mongolia as a test example. The results show that the fluctuation of spring wheat yield increased with the warming and drying climatic trend in Wuchuan County. The maximum yield decrease and its probability were 3.5 and 64.6%, respectively, for the temperature maximum increase 88.3%, and its risk was 2.2%. The maximum yield decrease and its probability were 14.1 and 56.1%, respectively, for the precipitation maximum decrease 35.2%, and its risk was 7.9%. For the comprehensive impacts of temperature and precipitation, the maximum yield decrease and its probability were 17.6 and 53.4%, respectively, and its risk increased to 9.4%. If we do not adopt appropriate adaptation strategies, the degree of loss from the negative impacts of multiclimatic factors and its probability of occurrence will both increase accordingly, and the risk will also grow obviously.

Impacts of recent climate change on dry-land crop water consumption in the northern agro-pastoral transitional zone of China

Climate change has substantially impacted crop growth and development in the northern agro-pastoral transitional zone. Examination of the response of crop water consumption to climate change may provide a guide for adapting local agricultural production and ecological construction to new realities. The water consumption of three local crops (wheat, naked oats, and potatoes) is examined for Wuchuan County in the northern agro-pastoral transitional zone of China using meteorological data from 1960 to 2007 and soil moisture data from 1983 to 2007. The relationships between climate change and the crop water consumption are discussed. The results show that Wuchuan experienced both a warming trend and a reduction of precipitation between 1960 and 2007. The annual mean surface air temperature increased at a rate of 0.04°C yr−1 and the annual precipitation decreased at a rate of 0.7 mm yr−1. Both trends are particularly pronounced between 1983 and 2007, with an increase in annual mean temperature of 0.09°C yr−1 and a decrease in annual mean precipitation of 2.1 mm yr−1. Crop water consumption decreased between 1983 and 2007 for wheat (1.65 mm yr−1), naked oats (2.04 mm yr−1), and potatoes (3.85 mm yr−1). Potatoes and naked oats consume more water than wheat. Climate change has significantly impacted crop water consumption. Water consumption and rainfall during the growing season are positively correlated, while water consumption and active accumulated temperature are negatively correlated. Compared to precipitation, accumulated temperature has little impact on crop water consumption. Recent climate change has been detrimental for crop production in Wuchuan County. Adaptation to climate change should include efforts to breed drought-resistant crops and to develop drought-resistant cultivation techniques.

Assessing the combined effects of climatic factors on spring wheat phenophase and grain yield in Inner Mongolia, China

Understanding the regional relationships between climate change and crop production will benefit strategic decisions for future agricultural adaptation in China. In this study, the combined effects of climatic factors on spring wheat phenophase and grain yield over the past three decades in Inner Mongolia, China, were explored based on the daily climate variables from 1981–2014 and detailed observed data of spring wheat from 1981–2014. Inner Mongolia was divided into three different climate type regions, the eastern, central and western regions. The data were gathered from 10 representative agricultural meteorological experimental stations in Inner Mongolia and analysed with the Agricultural Production Systems Simulator (APSIM) model. First, the performance of the APSIM model in the spring wheat planting areas of Inner Mongolia was tested. Then, the key climatic factors limiting the phenophases and yield of spring wheat were identified. Finally, the responses of spring wheat phenophases and yield to climate change were further explored regionally. Our results revealed a general yield reduction of spring wheat in response to the pronounced climate warming from 1981 to 2014, with an average of 3564 kg·ha-1. The regional differences in yields were significant. The maximum potential yield of spring wheat was found in the western region. However, the minimum potential yield was found in the middle region. The air temperature and soil surface temperature were the optimum climatic factors that affected the key phenophases of spring wheat in Inner Mongolia. The influence of the average maximum temperature on the key phenophases of spring wheat was greater than the average minimum temperature, followed by the relative humidity and solar radiation. The most insensitive climatic factors were precipitation, wind speed and reference crop evapotranspiration. As for the yield of spring wheat, temperature, solar radiation and air relative humidity were major meteorological factors that affected in the eastern and western Inner Mongolia. Furthermore, the effect of the average minimum temperature on yield was greater than that of the average maximum temperature. The increase of temperature in the western and middle regions would reduce the spring wheat yield, while in the eastern region due to the rising temperature, the spring wheat yield increased. The increase of solar radiation in the eastern and central regions would increase the yield of spring wheat. The increased air relative humidity would make the western spring wheat yield increased and the eastern spring wheat yield decreased. Finally, the models describing combined effects of these dominant climatic factors on the maturity and yield in different regions of Inner Mongolia were used to establish geographical differences. Our findings have important implications for improving climate change impact studies and for local agricultural production to cope with ongoing climate change.