Fengshan Liu

Single rice growth period was prolonged by cultivars shifts, but yield was damaged by climate change during 1981-2009 in China, and late rice was just opposite

Based on the crop trial data during 1981-2009 at 57 agricultural experimental stations across the North Eastern China Plain (NECP) and the middle and lower reaches of Yangtze River (MLRYR), we investigated how major climate variables had changed and how the climate change had affected crop growth and yield in a setting in which agronomic management practices were taken based on actual weather. We found a significant warming trend during rice growing season, and a general decreasing trend in solar radiation (SRD) in the MLRYR during 1981-2009. Rice transplanting, heading, and maturity dates were generally advanced, but the heading and maturity dates of single rice in the MLRYR (YZ_SR) and NECP (NE_SR) were delayed. Climate warming had a negative impact on growth period lengths at about 80% of the investigated stations. Nevertheless, the actual growth period lengths of YZ_SR and NE_SR, as well as the actual length of reproductive growth period (RGP) of early rice in the MLRYR (YZ_ER), were generally prolonged due to adoption of cultivars with longer growth period to obtain higher yield. In contrast, the actual growth period length of late rice in the MLRYR (YZ_LR) was shortened by both climate warming and adoption of early mature cultivars to prevent cold damage and obtain higher yield. During 1981-2009, climate warming and decrease in SRD changed the yield of YZ_ER by -0.59 to 2.4%; climate warming during RGP increased the yield of YZ_LR by 8.38-9.56%; climate warming and decrease in SRD jointly reduced yield of YZ_SR by 7.14-9.68%; climate warming and increase in SRD jointly increased the yield of NE_SR by 1.01-3.29%. Our study suggests that rice production in China has been affected by climate change, yet at the same time changes in varieties continue to be the major factor driving yield and growing period trends.

Spatiotemporal variability of winter wheat phenology in response to weather and climate variability in China

Weather and climate variability are predicted to impact food security by altering crop growth, phenology, and yield processes. Adaptation measures are critical for reducing future vulnerability of crop production to warming weather and climate variability. It is therefore vital to investigate the shifts in crop phenological processes in response to weather/climate variability. This study analyzes the trends in the dates of winter wheat (Triticum aestivum L.) phenology in relation to average temperature of different growth stage and the adaptation of the crop to weather/climate variability in China. The results suggest that the phenological phases of winter wheat have specific regional patterns in China. There are also significant shifts in the dates of winter wheat phenology and the duration of the growth stages in the investigated 30-year period of 1980–2009. While the date of sowing winter wheat delays, the dates of post-winter phenological phases (e.g., heading and maturity dates) advances in most areas of China. Detailed analysis shows that the changes in the phenological phases of winter wheat are strongly related to temperature trends. Temporal trends in phenological phases of winter wheat are similar in characteristics to corresponding trends in temperature. Although warming weather and climate variability is the main driver of the changes in winter wheat phenology, temperature is lower than before in most of the investigated stations during the period from heading to maturity—mainly the grain-filling stage. This is mainly due to the early heading and maturity dates, which in turn not only prolong growth stages but also enhance productivity of winter wheat. This could be a vital adaptation strategy of winter wheat to warming weather with beneficial effects in terms of productivity.

Contributions of climate, varieties, and agronomic management to rice yield change in the past three decades in China

The long-term field experiment data at four representative agro-meteorological stations, together with a crop simulation model, were used to disentangle the contributions of climate change, variety renewal, and fertilization management to rice yield change in the past three decades. We found that during 1981–2009 varieties renewal increased rice yield by 16%–52%, management improvement increased yield by 0–16%, and the contributions of climate change to rice yield varied from — 16% to 10%. Varieties renewal and management improvement offset the negative impacts of climate change on rice production. Among the major climate variables, decreases in solar radiation reduced rice yield on average by 0.1%per year. The impact of temperature change had an explicit spatial pattern. It increased yield by 0.04%–0.4% per year for single rice at Xinbin and Ganyu station and for late rice at Tongcheng station, by contrast reduced yield by 0.2%–0.4% per year for single rice at Mianyang station and early rice at Tongcheng station. During 1981–2009, rice varieties renewal was characterized by increases in thermal requirements, grain number per spike and harvest index. The new varieties were less sensitive to climate change than old ones. The development of high thermal requirements, high yield potential and heat tolerant rice varieties, together with improvement of agronomic management, should be encouraged to meet the challenges of climate change and increasing food demand in future.

Energy partitioning and environmental influence factors in different vegetation types in the GEWEX Asian Monsoon Experiment

Environmental influences upon energy balance in areas of different vegetation types (i.e., forest at Kog-Ma in Thailand and at Yakutsk in Russia, grassland at Amdo in Chinese Tibet and at Arvaikheer in Mongolia, and mixed farmland at Tak in Thailand) in the GEWEX Asian Monsoon Experiment were investigated. The sites we investigated are geographically and climatologically different; and consequently had quite large variations in temperature (T), water vapor pressure deficit (VPD), soil moisture (SM), and precipitation (PPT). During May-October, the net radiation flux (Rn) (in W·m−2) was 406.21 at Tak, 365.57 at Kog-Ma, 390.97 at Amdo, 316.65 at Arvaikheer, and 287.10 at Yakutsk. During the growing period, the Rn partitioned into latent heat flux (λE/Rn) was greater than that partitioned into sensible heat flux (H/Rn) at Tak and at Kog-Ma. In contrast, λE/Rn was lower than H/Rn at Arvaikheer, H/Rn was less than λE/Rn between DOY 149 and DOY 270 at Amdo, and between DOY 165 and DOY 235 at Yakutsk. The Rn partitioned into ground heat flux was generally less than 0.15. The short-wave albedo was 0.12, 0.18, and 0.20 at the forest, mixed land, and grass sites, respectively.At an hourly scale, energy partitions had no correlation with environmental factors, based on average summer halfhourly values. At a seasonal scale energy partitions were linearly correlated (usually p<0.05) with T, VPD, and SM. The λE/Rn increased with increases in SM, T, and VPD at forest areas. At mixed farmlands, λE/Rn generally had positive correlations with SM, T, and VPD, but was restrained at extremely high values of VPD and T. At grasslands, λE/Rn was enhanced with increases of SM and T, but was decreased with VPD.

Impact of thermal time shift on wheat phenology and yield under warming climate in the Huang-Huai-Hai Plain, China

Given climate change can potentially influence crop phenology and subsequent yield, an investigation of relevant adaptation measures could increase the understanding and mitigation of these responses in the future. In this study, field observations at 10 stations in the Huang-Huai-Hai Plain of China (HHHP) are used in combination with the Agricultural Production Systems Simulator (APSIM)–Wheat model to determine the effect of thermal time shift on the phenology and potential yield of wheat from 1981–2009. Warming climate speeds up winter wheat development and thereby decreases the duration of the wheat growth period. However, APSIM–Wheat model simulation suggests prolongation of the period from flowering to maturity (Gr) of winter wheat by 0.2–0.8 d∙10yr–1 as the number of days by which maturity advances, which is less than that by which flowering advances. Based on computed thermal time of the two critical growth phases of wheat, total thermal time from floral initiation to flowering (TT_floral_initiation) increasesd in seven out of the 10 investigated stations. Alternatively, total thermal time from the start of grainfilling to maturity (TT_start_ grain_fill) increased in all investigated stations, except Laiyang. It is thus concluded that thermal time shift during the past three decades (1981–2009) prolongs Gr by 0.2–3.0 d∙10yr–1 in the study area. This suggests that an increase in thermal time (TT) of the wheat growth period is critical for mitigating the effect of growth period reduction due to warming climatic condition. Furthermore, climate change reduces potential yield of winter wheat in 80% of the stations by 2.3–58.8 kg∙yr–1. However, thermal time shift (TTS) increases potential yield of winter wheat in most of the stations by 3.0–51.0 kg∙yr–1. It is concluded that wheat cultivars with longer growth periods and higher thermal requirements could mitigate the negative effects of warming climate on crop production in the study area.