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20 January 2017, Volume 38 Issue 01

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Phenological Variation and Its Response to Climate Warming in Semi-Arid Region of Loess Plateau

LEI Jun, YAO Yu-bi, SUN Run, GUO Ji-ping, NIU Hai-yang

2017, 38(01):  1-8.  doi:10.3969/j.issn.1000-6362.2017.01.001

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To reveal the response characteristics of typical plant phenology to climate warming in semi-arid region of the Loss plateau, the variation characters of phenophases for typical plant during spring and autumn was investigated by using correlation methods, based on phonological and temperature data from 1994 to 2014. The results showed that the day difference of leaf-expansion stage for herbaceous plant between earliest date and latest date ranged from 20-36d in historical record, and 20-38d for woody pant. The phenology for herbaceous plant in spring showed an advanced trend, and there was a large difference of phenology for woody plants. The leaf-expansion stage of Peony (Paeonia suffruticoss) and Hankow willow (Salix matsudana) showed an obviously advanced trend. Meanwhile, there was a delay trend in discoloration beginning period and withered beginning period of herbaceous plant, as same as for woody plant, withered the deciduous beginning period in autumn. There was no obviously variation for growing season of Peony, but the growing season of other typical plant increased significantly. The beginning flowering stage was sensitive to temperature in past one month and three months, and temperature from March to May. The beginning flowering stage advanced 5-8d when the temperature increased 1℃. We concluded that the phenology of herbaceous plant in Loss plateau was more sensitive to climate warming than woody plant. For the purpose of ecological restoration, we suggested that choosing insensitive trees to climate warming, including Almond (Prunus armeniaca) and Elm (Ulmus pumila), in vulnerable region of Loss plateau was the best choice.

Changes of Main Phenophases of Natural Calendar and Phenological Seasons in Hohhot

ZHU Yuan-jun, HAO Qi, QING Hua, ZHAO Li-qing, PIAO Shun-ji

2017, 38(01):  9-20.  doi:10.3969/j.issn.1000-6362.2017.01.002

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Based on the continuous phenological observation data of 23 woody plant species in Hohhot from 1983 to 2014, the natural calendar was established, and the changes of main phenophases of natural calendar and phenological seasons since 1983 and the reasons for these changes were revealed by analyzing the differences of phenophases between 1983-1998 and 1999-2014 and the correlation between phenophases changes and climatic factors. The results showed that in comparison with those of 1983-1998 the start time of phenological spring （represented by the time of bud expansion of Salix babylonica） and summer （represented by the time of 50% of full flowering of Robinia pseudoacacia） in 1999-2014 was advanced by 7 days and 4 days separately; while the start time of phenological autumn （represented by the time of fruit drop of Sorbaria kirilowii） and winter （represented by the time of all leaves of Amygdalus triloba coloring） in 1999-2014 was delayed respectively by 3 days and 6 days. The order of phenophase in spring, autumn and winter changed in different degrees. Correlation analysis between the phenological index of the first date of a season and climatic factors preceding three months of the season indicated that the mean air temperature of the first preceding month showed negative correlation with phenological index of the first date of spring, and significantly negative correlation with that of summer, but a positive correlation with that of winter. Mean sunshine duration of the first preceding month was positively correlated with the phenological index of the first date of autumn but a negative correlation with that of winter, and mean rain capacity of the first preceding month was positively correlated with phenological index of the first date of summer. Additionally, the mean air temperature of the second preceding month correlated with the phenological index of the first date of summer negatively; while the mean rain capacity of the third preceding month correlated with that of the first date of autumn negatively. The raise of average temperature was probably the main reason for the changes of phenological season in Hohhot, and the average sunshine duration and average precipitation also affected the changes of phenological season in different extent.

Effects of Soil Water Stress on Photosynthetic Characteristics and Antioxidant Enzyme System of Cucumber Leaves in Greenhouse

ZHANG Man-yi, YANG Zai-qiang,HOU Meng-yuan

2017, 38(01):  21-30.  doi:10.3969/j.issn.1000-6362.2017.01.003

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Took cucumber variety of ‘Jinyan4’ as experimental materials, the potting experiment in all growth stages of cucumber under different soil water stresses was conducted in Venlo greenhouse of Nanjing University of Information Science &Technology in autumn and winter of 2015/2016. Soil water treatments were divided into four levels: normal water supply (CK, 70%-80% of field water holding capacity), mild water stress (T1, 60%-70% of field water holding capacity), moderate water stress (T2, 50%-60% of field water holding capacity), and severe water stress (T3, 30%-40% of field water holding capacity). Soil water sensor EM50 was used to monitor soil water content. The photosynthetic characteristics and antioxidant enzyme activities of cucumber leaves were determined at seedling stage, tendril stage, flowering stage and ripening stage. The results showed that photosynthetic pigment contents in different treatments had a declining trend under soil water stresses. Compared with CK, chlorophyll a, chlorophyll b and carotenoids content of severe water stress (T3) treatment was reduced by 47.41%, 41.03% and 34.03%, respectively. Chlorophyll a/b had a minor change in different treatments. Leaf net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), transpiration rate (Tr), stomatal conductance (Gs) declined with increase of soil water stress degree. Meanwhile, stomatal limitation value (Ls) increased. Water Use Efficiency (WUE) of severe water stress (T3) treatment was higher than other treatments. With the prolonging of soil water stress days, the malonaldehyde (MDA) contents had a gradual rise and the activity of superoxide dismutase (SOD) and catalase (CAT) increased firstly and then decreased. Conversely, the activity of peroxidase (POD) showed a decreasing trend firstly and then decreased before an increasing trend. With the aggravation of soil water stress, SOD, POD and CAT activity and MDA contents increased gradually. This study indicated that soil water stress made activities of antioxidant enzymes and MDA contents of cucumber leaf increased, but weaken photosynthesis.

Temporal and Spatial Variations of Agro-meteorological Disasters of Main Crops in China in a Changing Climate (Ⅱ):Drought of Cereal Crops in Northwest China

HE Bin, LIU Zhi-juan, YANG Xiao-guang, SUN Shuang

2017, 38(01):  31-41.  doi:10.3969/j.issn.1000-6362.2017.01.004

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Based on the 1961-2010 daily meteorological data from 149 meteorological stations in northwest China and the growth period data of spring wheat, spring maize and summer maize, the spatial distribution and time evolution characteristic of drought for the three crops were cleared by using the crop water deficit index (CWDI). The results showed that (1) the occurrence of drought was frequent for the three crops during the whole growing seasons and each growth period in the study region. Specially, extreme drought and severe drought occurred with a wide range and high frequency, while light drought and moderate drought tended to occur in the eastern parts of the study region such as the southern area of Gansu and Shaanxi Province where the drought occurred less frequently and the level was lower. (2) The ratios of drought occurring stations for spring wheat, spring maize and summer maize during the whole growing period were 79.1%, 84.5% and 77.4%, respectively; the variation in the ratio of drought occurring stations for summer maize was relatively steady but the ratios of drought occurring stations for spring wheat and summer maize both showed a high fluctuation. Overall, the ratio of drought occurring stations for spring wheat during the whole growing season exhibited a declining trend, with a rate of -0.55 percent points per decade. However, the ratio of drought occurring stations for spring maize and summer maize during the growing season showed an increasing trend, with the rates of 0.24 percent points per decade and 0.20 percent points per decade, respectively. (3) The drought strength for spring wheat and summer maize in the eastern parts of the study region showed an increasing trend while a declining trend was detected in the west. The drought strength for summer maize in northern Shaanxi Province, Ningxia Autonomous Region and Hexi Corridor experienced an increasing trend, however other regions showed a decreasing trend.

Extreme High-temperature in Summer and Its Impacts on Vegetation in East China

GE Fei-fan, MAO Ke-biao, JIANG Yue-lin, TAN Xue-lan, ZHAO Ying-hui, XIA Lang

2017, 38(01):  42-51.  doi:10.3969/j.issn.1000-6362.2017.01.005

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Based on daily maximum surface air temperature data during 1971?2006 and normalized difference vegetation index (NDVI) data of AVHRR during 1981?2006, the frequency and average duration days of summer extreme heat wave were analyzed by using method of Morlet wavelet transform, as well as the periodic variation about the occurrence times of extreme high-temperature. Meanwhile, the relationship between the occurrence times of extreme high-temperature and NVDI was analyzed by using Singular Value Decomposing (SVD) in East China. The results showed that, (1) the frequency of summer extreme heat wave in East China showed that southern region was higher than the northern, the western was higher than the eastern, the plain region was higher than the mountainous region. But high value areas of average duration days were closed to the sea. (2) Occurrence times of summer extreme high-temperature in East China were mainly affected by three temporal scales which were 22 years, 9 years and 4 years. Among three temporal scales, the scale fluctuation around 22 years was the first primary period with a relatively stable oscillation throughout the whole time domain. The second primary period was around 9 years, its oscillation amplitude had been gradually increasing from the beginning of 1994, which could have been a great impact in the future. (3) NDVI correlated significantly with the occurrence times of summer extreme high-temperature in East China. The summer vegetation coverage was lower in the east of Jiangsu, while higher in the north of Shandong as well as the southwest and northwest of Jiangxi, when the occurrence times of summer extreme high-temperature in the south and center of East China were above normal. The summer vegetation coverage was higher in the northeast of Shandong, while lower in the east of Jiangsu as well as the south of Fujian and the north of Jiangxi, when the occurrence times of summer extreme high-temperature in the center of Shandong region were below normal.

Estimating Dry Matter Content of Poplar Leaf by Hyperspectral Data

CHENG Zhi-qing, ZHANG Jin-song, MENG Ping, LI Yan-quan, ZHENG Ning

2017, 38(01):  52-60.  doi:10.3969/j.issn.1000-6362.2017.01.006

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In order to explore estimating the dry matter content of poplar leaves accurately, rapidly and accurately and nondestructive with hyperspectral data. Simulated values of poplar leave hyperspectral data which were leaf scales and canopy scales were obtained by PROSPECT and PROSAIL models which input parameters were measured by the physical and chemical data and soil background spectral data. At the same time, the dry matter content, equivalent water thickness and hyperspectral data were obtained from the measured leaf scales and canopy scales. Finally, the statistical methods were used to analyze the dry matter content in two scales of poplar leaves. The results showed that, the best band combination of the normalized difference vegetation index of dry matter was respectively band combination between 1685nm and 1704nm and band combination between 1551nm and 2143nm, respectively in leaf scales and canopy scales. Dry matter content models of leaf and canopy scales were built respectively by NDMI (1685,1704) and NDMI(1551,2143). The model validation accuracy of the leaf scale dry matter content was R2=0.663, RMSE=0.001g·cm-2, and the model validation accuracy of the canopy scale dry matter content was R2=0.91, RMSE=16.7g·m-2. Obviously, the hyperspectral technique has a high precision for estimating the dry matter content of poplar leaves, which can provide reference for the rapid and nondestructive estimation of dry matter content of poplar leaves.