Variation Characteristics of Hydrothermal Resources Effectiveness Under the Background of Climate Change in Southern Rice Production Area of China

The spatiotemporal characteristics of hydrothermal resources in southern rice production area of China have changed under the background of climate change,and this change would affect the effectiveness of hydrothermal resources during local rice growing period.According to the cropping system subdivision in southern rice production area of China during 1980s,this study used climate data from 254 meteorological stations and phonological data from 168 agricultural observation stations in the south of China,and adopted 6 international evaluation indices about the effectiveness of hydrothermal resources to analyze the temporal and spatial characteristics of hydrothermal resources during the growing period of single cropping rice system and double cropping rice system for 16 planting zones in the whole study area.The results showed that：in southern rice production area of China,the effectiveness of thermal resources of single cropping rice area（SCRA） was less than that of double cropping rice area（DCRA）,whereas the effectiveness of thermal resources of both SARA and DCRA showed a decreasing trend.The index value of effective precipitation satisfaction of SCRA was higher than that of DCRA,nevertheless the index value of effective precipitation satisfaction of both SCRA and DCRA showed a decreasing trend.There was a significant linear relationship between effective thermal resource and water demand,likely water demand increased by 18 mm with every 100°C d increase of effective heat.Effective precipitation satisfaction index（EPSI） showed a negative correlation with effective heat,yet showed a positive correlation with effective precipitation.EPSI reduced by 1% when effective heat resource increased by 125°C d.This study could provide insights for policy makers,land managers or farmers to improve water and heat resource uses and rationally arrange rice production activities under global climate change condition.

Evaluation on Genetic Quality and Traits of Rice Landraces in the Taihu Lake Area

In this paper,with 511 rice landraces in the Taihu Lake area as test materials,we select 19 starch synthesis-related intragenic molecular markers to detect the genetic quality of starch,and compare them with 86 bred varieties. The results show that the average polymorphic information content( PIC) of japonica landraces is 0. 1726,slightly higher than the average PIC( 0. 1101) of the bred japonica rice varieties.Based on Nei's genetic distance between materials,UPGMA method is used for clustering,and all study materials are divided into 6 groups.Group I mainly includes indica rice,the bred japonica rice varieties are mainly concentrated in the first half of Group II and Group III,and the japonica landraces are mainly concentrated in the second half of Group III,and Group Ⅳ,Ⅴ,Ⅵ. Both of them are in different regions,and there has been genetic differentiation. According to the national standard of high quality rice,it is found that many rice landraces in the Taihu Lake area have good quality and traits,and these varieties can be used for future high quality breeding.

Physicochemical water quality parameters in typical rice-crayfish integrated systems(RCIS)in China

To determine the variation of water quality in rice-crayfish(Procambarus clarkii)integrated systems(RCIS)in China,eleven water quality parameters were measured monthly in a typical RCIS located in Qianjiang City(Hubei Province)from July 2014 to June 2015,the parameters were analyzed with principal component analysis(PCA)and compared between the trenches and rice areas during the rice fallow period(Nov-May).The trench and rice area comprehensive results showed that pH(7.48-8.68),NH_(4)^(+)-N(0.2-1.09 mg/L),NO_(2)^(-)-N(<0.052 mg/L)and conductivity(435-951μS/cm)were within the suitable ranges for P.clarkii and that turbidity(TU)was high during the crayfish harvesting and rice planting season.Annual averages of total nitrogen(TN),total phosphorus(TP),permanganate index(CODMn),and chlorophyll a(Chl.a)content were<2(except in Nov-Dec),0.25,10 mg/L,and 50 mg/m^(3)(especially in Nov-May,<10 mg/m^(3)),respectively.Dissolved oxygen(DO)was below 4 mg/L in Mar-Sep,with a minimum of~1 mg/L,and much higher in Oct-Feb.The maximum and minimum monthly average water temperature(WT)were 31.4°C in July and 5.7°C in December,while the maximum and minimum instantaneous WT were 39.7°C and 2.5°C,respectively.PCA analysis showed that the first three axes,which were mainly correlated with DO,WT and nutrient level,described most information of the parameters,and parameters showed seasonal changes.Some differences were observed in water parameters between the trenches and rice areas,i.e.,trenches generally had higher TU,WT and DO,and lower TN,TP and CODMn,although no significant differences were found in some months and some parameters.The study revealed relatively low water nutrient level,probable extreme WT and DO level in some seasons,and certain differences between the trenches and rice areas in typical CRIS in China.Accordingly,some measures should be taken to improve the negative parameters:1)enhance the water fertility;2)increase DO,especially in Mar-Sep;3)increase the trench and water depth to avoid extreme WT.And water quality management should be addressed in both trenches and rice areas.