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20 August 2021, Volume 42 Issue 08

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Spatial and Temporal Variability of Vegetation Net Primary Productivity in Qiangtang National Nature Reserve under Climate Change

ZHOU Kan-she, DU Jun, SHEN Xu, PU Gui-juan, ZHANG Dong-dong, DANG Xue-ni

2021, 42(08):  627-641.  doi:10.3969/j.issn.1000-6362.2021.08.001

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This paper is based on the meteorological observation data of the five meteorological stations(Shiquanhe,Gerze, Xianza,Bangoin and Amdo)near Qiangtang National Nature Reserve, the climate of Qiangtang National Nature Reserve from 1960 to 1990 and the estimated grid data in the future issued by IPCC5. The Miami model, Thornthwaite Memorial model, and tendency rate were used. The statistical analysis methods were used to study the spatiotemporal evolution of Net Primary Productivity in Qiangtang National Nature Reserve and its response to climate change. The results showed that: (1) the average annual temperature decreases from the west to the east, and the annual precipitation increases from the west to the east. The annual mean temperature(T) showed a significant increasing trend, while the annual precipitation(R) and annual evapotranspiration(E) showed a slight increasing trend. NPP of Temperature(NPPt) and NPP of precipitation(NPPr) showed a slight increasing trend at all stations, and NPP of evapotranspiration(NPPe) and standard NPP(NPPb) showed a slight increasing trend at most stations. (2) NPPt gradually decreased from the west to the east, NPPr gradually increased from the west to the east, NPPe and NPPb first increased and then decreased from the west to the east. The limiting factor of NPP was precipitation in Shiquanhe station and Gerze station, evapotranspiration in Xianza station and Bangoin station, and evapotranspiration or air temperature in Amdo station. (3) The NPPt, NPPr, NPPe and NPPb in different periods of the 21st century were significantly higher than those in all periods of the 20th century. The NPPt, NPPr, NPPe and NPPb were significantly increased in the future under different emission scenarios compared with those from 1960 to 1990. Under the trend of "warming and wetness" in the past 48 years and in the future, the NPP of vegetation increased, and the increase was larger in the cold and humid area in the southeast, but less in the cold and arid area in the northwest. The future climate is conducive to the improvement of local vegetation NPP and the improvement of local ecological environment. Assessing the possible impact of future climate change on the ecological environment of Qiangtang Plateau. The results not only provide a basic method for studying the Net Primary Productivity of vegetation in no man's land at regional scale, but also have important reference value for estimating ecological security research and ecological function planning.

Surface Energy Exchanges and Evapotranspiration of an Alpine Meadow on the Zoige Plateau

GUO Xiao-xuan, WANG Kai, LI Lei, ZHANG Han, MA Lei, YAO Zhi-sheng, ZHANG Wei, HU Zheng-hua, ZHENG Xun-hua

2021, 42(08):  642-656.  doi:10.3969/j.issn.1000-6362.2021.08.002

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The alpine meadow ecosystems of the Zoige Plateau play important roles in the energy and water cycle of the Qinghai-Tibet Plateau, but observation data of this region regarding to surface energy and water fluxes are very scarce. In this study, annual flux measurements were conducted based on the eddy covariance technique at a typical alpine meadow on the Zoige Plateau by using a three-dimensional sonic anemometer and an infrared open-path carbon dioxide and water vapor analyzer. The surface energy and evapotranspiration (ET) fluxes were calculated at the basis of half-hour. The purpose of this study is to reveal the characteristics and influencing factors of surface energy exchanges and ET. The results are as follows. All energy flux components showed clear diurnal and seasonal variation patterns. The annual mean net radiation, sensible heat, latent heat, and soil heat fluxes were 94.5, 21.0, 51.8 and 1.2Wm−2, respectively. The energy fluxes showed a “single peak” diurnal variation pattern both in the growing season and the non-growing season, despite different peak times for different energy components. During the non-growing season, the sensible heat fluxes were slight larger than the latent heat fluxes, while the latter absolutely dominated during the growing season. The annual mean Bowen ratio and energy closure rate were 0.70 and 0.77, respectively. Radiation was the most important environmental factor that influenced the sensible heat fluxes, while temperature, radiation and water vapor pressure deficit for the latent heat fluxes. The ET fluxes during the growing season were significantly larger than those during the non-growing season. The daily ET fluxes ranged from 0.12 to 5.09mmd−1, and the annual mean value was 1.82mmd−1. Evapotranspiration during the non-growing season is controlled by the surface conductivity; during the growing season it is dominated by the radiation, rather than the surface conductivity of soil and vegetation. On a seasonal scale, the dynamics of ET depended on the seasonal variation of precipitation. The annual accumulated precipitation and ET were 682.7mm and 673.6mm, respectively, of which the growing season accounted for 84% and 82%. The lack of precipitation from June to July constrained the ET fluxes. During this period, soil water storage became the main source of ET. All precipitation finally returned to the atmosphere through ET. In this study, the seasonal variation patterns of the surface energy fluxes and ET were similar to those reported by other measurement studies on the Qinghai-Tibet Plateau. However, the annual mean Bowen ratio and annual accumulated ET were the largest among these studies. Such results were jointly attributed to the effects of temperature, precipitation, surface vegetation and other factors. Data of this study could be used for the parameterization optimization of the land surface models and for the validation of satellite and remote sensing data in the Zoige region.

Water Consumption Characteristics of Vitex negundo in Hilly Region of Taihang Mountains and Its Relationship to Reference Evapotranspiration

SANG Yu-qiang, LI Long, SHI Guang-yao, JIA Chang-rong, ZHANG Jin-song

2021, 42(08):  657-665.  doi:10.3969/j.issn.1000-6362.2021.08.003

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Vitex negundo is the native shrub species which was very popular in low mountain area of Taihang Mountains. It is widely used in such aspects as mountain greening, soil and water conservation, and ecological restoration due to its characteristics of strong resistance, and tolerance to barrenness. Studying on the water consumption of Vitex negundowas could not only reveal its water consumption dynamics and influencing mechanism, but also provide theoretical basis for local vegetation restoration and management. The water consumption of Vitex negundo and meteorological factors were measured with large weighing lysimeter and the automatic weather station, respectively. At the same time, reference evapotranspiration (ET0) was calculated by the Penman-Monteith equation recommended by FAO-56. The objective of the paper was to study the water consumption of Vitex negundo on different time scales, to find the adaption capacity to the arid environment, to reveal the relationship with ET0, and to provide empirical model for estimating the water consumption of Vitex negundo under the conditions of lacking measured data. The results showed that: (1) diurnal variation of water consumption of Vitex negundo showed single peak curve on typical days , which was consistent with solar radiation, air temperature, and vapor pressure deficit, but contrary to the relative humidity. Meanwhile, the peak time of water consumption of Vitex negundo. was 2 hours behind that of solar radiation, and time lag was found between them. Water consumption trendy of Vitex negundo on daily time scale showed low water consumption in the early and later growth period, and high in the middle growth period, and the value was 1.50mm, 2.00mm, and 4.00mm per day, respectively. Maximum and minimum of daily water consumption was found on 29th in August and 9th in October, with the value of 6.38mm and 0.20mm, respectively. The water consumption of Vitex negundo on monthly time scale showed the tendency of August >July > September > October> June > May. The total water consumption of Vitex negundo during the growth period was 513.5mm, and the rainfall was 526.6mm. The precipitation could meet the needs of water consumption Vitex negundo from the perspective of water balance. However, seasonal drought existed from May to June due to the less rainfall. (2) Vitex negundo has the feature of environmental adaptability and ecological plasticity. In rainy seasons, Vitex negundo was in prosperous growth period, the water transmission rate was high, and the water consumption was large. Adaptive mechanism started in arid season to reduce water consumption. (3) Good logarithmic relationship was found between daily water consumption of Vitex negundo and reference evapotranspiration in rainy seasons (July to October), while poor correlation was discovered between them in dry seasons ( May to June). The estimated value of water consumption was calculated with the fitting equation, and was compared with the measured valued by the lysimeter. The good consistency and small error were found between the estimated and measured values, which conformed the precision of the fitting equation. It was indicated the fitting equation was accurate to estimate water consumption of Vitex negundo in rainy seasons of the local area, but inaccurate in dry seasons.

Temperature-Increasing Characteristics of Plastic Film Mulching Planting Mode of the Double-Shallow-Furrow in Broader-Row Ridges in Western Heilongjiang during Maize Seedling

LOU De-jun, ZHANG Xing-lin, CONG Zhi-yu, XUE Yao, JIANG Li-xia

2021, 42(08):  666-675.  doi:10.3969/j.issn.1000-6362.2021.08.004

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Temperature changes and their differences were analyzed and compared in a comparative test was conducted between the two planting modes of broader-row ridges with double-shallow-furrow film mulching and bare land in Fuyu County, one of the main maize producing regions of Heilongjiang Province, in May-June 2018,with the soil temperature of 5cm below ground and the near-surface air temperature of 5cm above ground were continuously observed for 24 hours. And the temperature-increasing characteristics and advantages of the shallow-furrow film mulching planting mode were further evaluated. Results show that compared with the bare land, the shallow-furrow film mulching planting mode has a significant warming effect. The temperature increase was mainly at the early stage of maize seed germination, emergence and early stage of seedling growth, that is, before the film mulch was broken and the air was released, and the surface soil temperature and near-surface air temperature significantly increased by 2.8℃ and 6.1℃, respectively. The temperature rose both in the daytime and at night, and the warming effect was greater during the day than at night. At the late stage of seedling growth, that is, after the film mulch was broken, the surface soil temperature and near-surface air temperature dropped slightly, but the temperature decrease was mainly in the daytime, while the temperature increase was distinct at night. The diurnal temperature range was reduced by 3−4℃ on average. During the filming period, the daily minimum temperature of surface soil temperature and near-surface air temperature showed consistent increase, and the minimum surface soil temperature increased significantly by 2.0℃. The shallow-furrow film mulching planting mode increased the integrated temperature by 35% compared with that of the bare land, and the growth period was reduced by 8 days. Results also show that the shallow-furrow film mulching planting mode has obvious effects on temperature increasing during the emergence and growth of maize seedlings, which can reduce the impact of low temperature and strong winds in the maize seedling period, and can provide the basis for improving the utilization rate of heat resources, scientific introduction and optimizing planting structures. This mode is fully operated by machines, which is easy and favorable for large-scale extension. It has vast potential for further application in maize production in cold regions like Heilongjiang Province and other northeastern regions.

Simulation of Influences of Thermal Insulation Quilt Top Roll on the Light Environment in the North-South Greenhouse on Equinox Day

FAN Yi-ran, LIU Huan, YAN Zheng-nan, LI Xiao-ye, YANG Yan-jie

2021, 42(08):  676-685.  doi:10.3969/j.issn.1000-6362.2021.08.005

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In order to figure out the influences of thermal insulation quilt on the light environment in different positions in the greenhouse, the light distributions in different positions (from east to west) in the greenhouse were analyzed. The simulation and actual measurement were conducted in the Spring and Autumn Equinox Day in this study. Shading from direct sunlight in greenhouse was studied through converting the three-dimensional solar altitude angle into two-dimensional angle. Moreover, the movement position and distance of the shading zone from east to west were calculated in the Spring and Autumn Equinox Day. The distribution of daily light integral (DLI) was simulated in the greenhouse in different positions. The simulated greenhouse span was 12m, the ridge height was 4.2m, and the length was 60m The steel arch above the ground was 16m long, the radius was 0.35m, and the diameter was 0.7m after the insulation was rolled up. Ethylene vinyl acetate (EVA) film with actual light transmittance at 65% was used in the greenhouse. The light intensity of different positions in the top roll of insulation quilt in greenhouse was measured and the DLI was calculated. The measured value was compared with the simulated value. The distribution of DLI at different positions in the east-west direction and the light distribution in the greenhouse were analyzed. The results based on the model showed that the DLI at the middle point in east-west direction of greenhouse was the smallest, which was 10.91mol·m−2·d−1. The DLI was lower within 1m from the middle point to east/west, which increased by 11.8% from 10.91mol·m−2·d−1 to 12.20mol·m−2·d−1. DLI increased with the increased distance from the middle to the east/west, and the maximum value was 13.70mol·m−2·d−1, which was 6m away from the middle point (the edge of the greenhouse). The measured results showed that the DLI in the greenhouse was also the smallest at the middle point of the east-west direction, which was 7.31mol·m−2·d−1. The DLI was also lower within 1m from the middle point to east/west, which increased by 3.4% from 7.31mol·m−2·d−1 to 7.56mol·m−2·d−1. Similar trends were observed in the measured results, and the maximum value was 12.70mol·m−2·d−1. The variation law of DLI in measured values was consistent with the simulated values, which were the smallest in the middle point of greenhouse, and DLI increased with the increased distance from the middle to the east/west. The DLI changed slightly in different positions from east to west in the greenhouse. However, this does not affect the accuracy of the simulation trend. The simulation values were consistent with the measured values. In conclusion, DLI in the middle region will restrict the growth of photophilic crops in the season with poor light environment, thus leading to light stress on the growth of vegetables and other light-loving crops in the greenhouse.

The Scientific Problem and Improvement of the Concepts of Accumulated Temperature and Heat Resource

ZHANG Zi-yuan, ZHENG Da-wei, PAN Yu-ying, PAN Zhi-hua

2021, 42(08):  686-692.  doi:10.3969/j.issn.1000-6362.2021.08.006

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The concepts of accumulated temperature and heat resources have been widely presented in domestic literature and teaching materials, and accumulated temperature is usually as the main form of representation of heat resource. But its traditional definition obviously violates the principles of physics, and the measurement units also have not been unified. It urgently needs to be given an accurate scientific interpretation and further standardized. Based on the origin and development history of the concepts of accumulated temperature and heat resources, the problems in its practical application are reviewed in this paper, and the application frequency, geographical distribution characteristics of the term of accumulated temperature and its synonyms through Web of Science related literature are statistically analyzed and compared. The results show that, although accumulated temperature is the main indicator of traditional term of agricultural heat resources and is widely used, however, in fact, plants and cold-blooded animals do not need a certain amount of heat energy to complete a certain stage of growth and development, but require suitable temperature conditions and necessary duration. Excessive heat or too high temperature will cause damage to organisms, and some species even require relatively lower temperatures. On the other hand, literature search and statistics show that the term “accumulated temperature” has been rarer and rarer used in the international academic communities now, and the term “heat resource” is also rarely used in authoritative agricultural meteorological literature. In order to promote a more accurate and scientific term, it is recommended to stop use of the term “accumulated temperature” in Chinese Scientific Journals and to change into "integrated temperature" or "thermal time". And the unit should be unified into "℃·d" or “℃·h” and not “℃”. The term of “heat resource” is also changed to “temperature resource” and broadened, i.e. the synthesis of temperature conditions and their duration conducive to growth and development of plants and cold-blood animals. It will give full scientific significance without affecting the large number of applications and achievements of the current accumulated temperature theory, and will promote further development of agricultural meteorology and related disciplines.

Thought on Statistics Methods of Temperature in the Hottest and Coldest Month-Long Periods

Erkejan HOYHAZI, JIANG Hui-fei , DAI An-ran

2021, 42(08):  693-702.  doi:10.3969/j.issn.1000-6362.2021.08.007

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The hottest and coldest month-long periods' temperatures are common indicators of Agro-climatical division. Commonly the hottest/coldest period is replaced by the full month of July/January directly, but this fixed full month is not an accurate reflection of the actual hottest /coldest period. The hottest/coldest period of the year changes in temperatures and starting to end dates every year. In this paper, the length of the month-long period was set to be 31 days, as the common hottest and coldest months, July and January, are 31 days long. By using the daily temperature data from 1951 to 2018, collected at Changde weather station in Hunan province, the temperature of the hottest/coldest 31-day period was calculated using moving average approaches.  The results showed that, (1)the hottest period spans from late June to early September, and the average hottest 31-day period was from mid-July to mid-August. Comparing the average hottest 31-day period and the full months of July and August with the actual highest 31-day period temperatures, the average temperature error was 0.5℃, 0.9℃, and 1.7℃ colder, respectively. (2) The coldest period spanned from early December to mid-March, and the average coldest 31-day period is from early January to early February. Compared to the actual coldest 31-day period, the temperatures of the average coldest 31-day period and the full months of January and February were 1.0℃, 1.1℃, and 2.9℃ warmer than the temperature of the actual month-long period, respectively. (3) With a temperature error within 1.0℃ considered to be acceptable, the average hottest 31-day period' s average temperature was 90% accurate in calculating the actual hottest 31-day period' s average temperature while using July' s temperature is only 61.2% accurate, which demonstrated that the average hottest 31-day period was more accurate than July. (4) With a temperature error within 2.0℃ and temperature accuracy above 80% considered to be acceptable, the effect during the average coldest 31-day was slightly better than January. In summary, the temperature error of the average 31-day hottest/coldest period was less than these of July/January, and the accuracy is the opposite. Therefore, it is recommended that when estimating the temperature of the hottest/coldest month-long period to not use the fixed full month of July/January but instead use the average hottest/coldest 31-day period while still taking into consideration in the adjustments from the actual temperature.