Evapotranspiration and its components over a rainfed spring maize cropland under plastic film on the Loess Plateau, China

Aim of study: To determine seasonal variations in evapotranspiration (ET) and its components; and ascertain the key factors controlling ET and its components in a rainfed spring maize field under plastic film.Area of study: Shouyang County in Shanxi Province on the eastern Loess Plateau, ChinaMaterial and methods: Eddy covariance system combined with micro-lysimeters and meteorological observing instruments were used in the field. The manual method was used to measure the green leaf area index (GLAI) during the growing season.Main results: In 2015 and 2016, the growing season ET accounted for 80% and 79% of annual ET, respectively. Soil evaporation (E) accounted for 36% and 33% of the growing season ET in 2015 and 2016, respectively. The daily crop coefficient increased with increasing GLAI until a threshold of ~3 m2 m−2 in the canopy-increasing stage, and decreased linearly with decreasing GLAI in the canopy-decreasing stage. At equivalent GLAI, daily basal crop coefficient and soil water evaporation coefficient were generally higher in the canopy-increasing and -decreasing stages, respectively. During the growing season, the most important factor controlling daily ET, T, and E was net radiation (Rn), followed by GLAI for daily ET and T, and soil water content at 10-cm depth for daily E; during the non-growing season, daily ET was mainly controlled by Rn.Research highlights: The daily crop coefficient and its components reacted differently to GLAI in the canopy-increasing and -decreasing stages

Effects of Climate Warming on Net Primary Productivity in China During 1961–2010

The response of ecosystems to different magnitudes of climate warming and corresponding precipitation changes during the last few decades may provide an important reference for predicting the magnitude and trajectory of net primary productivity (NPP) in the future. In this study, a process-based ecosystem model, Carbon Exchange between Vegetation, Soil and Atmosphere (CEVSA), was used to investigate the response of NPP to warming at both national and subregional scales during 1961–2010. The results suggest that a 1.3°C increase in temperature stimulated the positive changing trend in NPP at national scale during the past 50 years. Regardless of the magnitude of temperature increase, warming enhanced the increase in NPP; however, the positive trend of NPP decreased when warming exceeded 2°C. The largest increase in NPP was found in regions where temperature increased by 1–2°C, and this rate of increase also contributed the most to the total increase in NPP in China\u27s terrestrial ecosystems. Decreasing precipitation depressed the positive trend in NPP that was stimulated by warming. In northern China, warming depressed the increasing trend of NPP and warming that was accompanied by decreasing precipitation led to negative changing trends in NPP in large parts of northern China, especially when warming exceeded 2°C. However, warming stimulated the increase in NPP until warming was greater than 2°C, and decreased precipitation helped to increase the NPP in southern China

Data from: Discrepancies in vegetation phenology trends and shift patterns in different climatic zones in middle and eastern Eurasia between 1982 and 2015

Changes in vegetation phenology directly reflect the response of vegetation growth to climate change. In this study, using the Normalized Difference Vegetation Index (NDVI) dataset from 1982 to 2015, we extracted start date of vegetation growing season (SOS), end date of vegetation growing season (EOS) and length of vegetation growing season (LOS) in the middle and eastern Eurasia region and evaluated linear trends in SOS, EOS and LOS for the entire study area, as well as for four climatic zones. The results show that the LOS has significantly increased by 0.27 d/yr (days per year), mostly due to a significantly advanced SOS (-0.20 d/yr) and a slightly delayed EOS (0.07 d/yr) over the entire study area from 1982 to 2015. The vegetation phenology trends in the four climatic zones are not continuous throughout the 34 year period. Furthermore, discrepancies in the shifting patterns of vegetation phenology trend existed among different climatic zones. Turning points (TP) of SOS trends in the Cold zone, Temperate zone and Tibetan Plateau zone occurred in the mid or late 1990s. The advanced trends of SOS in the Cold zone, Temperate zone and Tibetan Plateau zone exhibited accelerated, stalled and reversed patterns after the corresponding TP, respectively. The TP did not occurred in Cold-Temperate zone, where the SOS showed a consistent and continuous advance. TPs of EOS trends in the Cold zone, Cold-Temperate zone, Temperate zone and Tibetan Plateau zone occurred in the late 1980s or mid-1990s. The EOS in the Cold zone, Cold-Temperate zone, Temperate zone and Tibetan Plateau zone showed weak advanced or delayed trends after the corresponding TP, which were comparable with the delayed trends before the corresponding TP. The shift patterns of LOS trends were primarily influenced by the shift patterns of SOS trends and were also heterogeneous within climatic zones

Phenology data in middle and eastern Eurasia from 1982 to 2015

The folder named SOS stores the SOS data. The folder named EOS stores the EOS data. The "xlsx" files store the data corresponding to the figure in the article

The Resilience of Vegetation to the 2009/2010 Extreme Drought in Southwest China

The 2009/2010 extreme drought in southwest China (SWC) was a “once-in-a-century” drought event, which caused unprecedented damage to the regional ecology and socioeconomic development. The event provided a chance to explore the resilience of vegetation growth and productivity to the extreme drought. Here, we used the self-calibrating Palmer drought severity index (scPDSI) to describe the characteristics of the extreme drought. Vegetation growth and productivity indices, including the normalized difference vegetation index (NDVI), leaf area index (LAI), and gross primary productivity (GPP), were applied to analyze the resilience of different vegetation types to the extreme drought. Our results showed that the extreme drought event occurred mainly in Yunnan Province, Guizhou Province, central and northern Guangxi Zhuang Autonomous Region, and northwestern Sichuan Province. The spatial heterogeneity of the extreme drought was related to the temperature increase and water deficit. During the extreme drought, the vegetation growth and productivity of evergreen broadleaf forest were the least suppressed, whereas cropland was greatly suppressed. The recovery of cropland was higher than that of evergreen broadleaf forest. NDVI and LAI were recovered in more than 80% of the drought-affected area within 5 months, whereas GPP required a longer time to recover. Moreover, the results of multiple linear regression showed that an increase in surface soil moisture was able to significantly improve the resistance of vegetation NDVI and LAI in evergreen broadleaf forest, evergreen needleleaf forest, evergreen broadleaf shrubland, deciduous broadleaf shrubland, and grassland. Our study highlights the differences in the resilience of different vegetation types to extreme drought and indicates that surface soil moisture is an important factor affecting vegetation resistance in SWC

Projections of the Net Primary Production of Terrestrial Ecosystem and Spatiotemporal Responses to Climate Change in the Yangtze River Economic Belt

Evaluating the responses of net primary productivity (NPP) to climate change is essential for regional ecosystem management and adaptations to climate change. The Yangtze River Economic Belt (YREB) is a key ecological functional area and hotspot of carbon sequestration in China due to the high degree of forest coverage. We used a process-based ecosystem model to project terrestrial NPP and analyzed the response to climate change over the 21st century in the YREB under two representative concentration pathway (RCP) scenarios using the regional climate model. The results show that the projection of NPP generally increased by 13.5% under RCP4.5 and 16.4% under RCP8.5 in the middle of the century, by 23% under RCP4.5, and by 35% under RCP8.5 in the late term of the century compared with that from a reference period of current climate conditions (1985–2006). The rate of NPP change under the RCP8.5 scenario is higher than that under the RCP4.5 scenario. Similarly, the NPP is also projected to increase both with 1.5 and 2 °C global warming targets in the YREB. The magnitudes of NPP increment are approximately 14.7% with 1.5 °C and 21% with 2 °C warming targets compared with the current climate, which are higher than the average increments of China. Although NPP is projected to increase under the two scenarios, the tendency of NPP increasingly exhibits a slowdown after the 2060 s under the RCP4.5 scenario, and the growth rate of NPP is projected to drop in more than 31% of regional areas with the additional 0.5 °C warming. In contrast, under the RCP8.5 scenario, the trend in NPP keeps rising substantially, even above 2 °C global warming. However, the NPP in some provinces, including Jiangxi and Hunan, is projected to reduce at the end of the 21st century, probably because of temperature rises, precipitation decreases, and water demand increases. Generally, the NPP is projected to increase due to climate change, particularly temperature increase. However, temperature rising does not always show a positive effect on NPP increasing; the growth rate of NPP will slow down under the RCP4.5 scenario in the mid-late 21st century, and NPP will also reduce by the end of this century under the RCP8.5 scenario in some places, probably presenting some risks to terrestrial ecosystems in these areas, in terms of reduced functions and service decline, a weakened capacity of carbon sequestration, and reduced agricultural production

Projections of the Net Primary Production of Terrestrial Ecosystem and Spatiotemporal Responses to Climate Change in the Yangtze River Economic Belt

Evaluating the responses of net primary productivity (NPP) to climate change is essential for regional ecosystem management and adaptations to climate change. The Yangtze River Economic Belt (YREB) is a key ecological functional area and hotspot of carbon sequestration in China due to the high degree of forest coverage. We used a process-based ecosystem model to project terrestrial NPP and analyzed the response to climate change over the 21st century in the YREB under two representative concentration pathway (RCP) scenarios using the regional climate model. The results show that the projection of NPP generally increased by 13.5% under RCP4.5 and 16.4% under RCP8.5 in the middle of the century, by 23% under RCP4.5, and by 35% under RCP8.5 in the late term of the century compared with that from a reference period of current climate conditions (1985–2006). The rate of NPP change under the RCP8.5 scenario is higher than that under the RCP4.5 scenario. Similarly, the NPP is also projected to increase both with 1.5 and 2 °C global warming targets in the YREB. The magnitudes of NPP increment are approximately 14.7% with 1.5 °C and 21% with 2 °C warming targets compared with the current climate, which are higher than the average increments of China. Although NPP is projected to increase under the two scenarios, the tendency of NPP increasingly exhibits a slowdown after the 2060 s under the RCP4.5 scenario, and the growth rate of NPP is projected to drop in more than 31% of regional areas with the additional 0.5 °C warming. In contrast, under the RCP8.5 scenario, the trend in NPP keeps rising substantially, even above 2 °C global warming. However, the NPP in some provinces, including Jiangxi and Hunan, is projected to reduce at the end of the 21st century, probably because of temperature rises, precipitation decreases, and water demand increases. Generally, the NPP is projected to increase due to climate change, particularly temperature increase. However, temperature rising does not always show a positive effect on NPP increasing; the growth rate of NPP will slow down under the RCP4.5 scenario in the mid-late 21st century, and NPP will also reduce by the end of this century under the RCP8.5 scenario in some places, probably presenting some risks to terrestrial ecosystems in these areas, in terms of reduced functions and service decline, a weakened capacity of carbon sequestration, and reduced agricultural production

The Resilience of Vegetation to the 2009/2010 Extreme Drought in Southwest China

The 2009/2010 extreme drought in southwest China (SWC) was a “once-in-a-century” drought event, which caused unprecedented damage to the regional ecology and socioeconomic development. The event provided a chance to explore the resilience of vegetation growth and productivity to the extreme drought. Here, we used the self-calibrating Palmer drought severity index (scPDSI) to describe the characteristics of the extreme drought. Vegetation growth and productivity indices, including the normalized difference vegetation index (NDVI), leaf area index (LAI), and gross primary productivity (GPP), were applied to analyze the resilience of different vegetation types to the extreme drought. Our results showed that the extreme drought event occurred mainly in Yunnan Province, Guizhou Province, central and northern Guangxi Zhuang Autonomous Region, and northwestern Sichuan Province. The spatial heterogeneity of the extreme drought was related to the temperature increase and water deficit. During the extreme drought, the vegetation growth and productivity of evergreen broadleaf forest were the least suppressed, whereas cropland was greatly suppressed. The recovery of cropland was higher than that of evergreen broadleaf forest. NDVI and LAI were recovered in more than 80% of the drought-affected area within 5 months, whereas GPP required a longer time to recover. Moreover, the results of multiple linear regression showed that an increase in surface soil moisture was able to significantly improve the resistance of vegetation NDVI and LAI in evergreen broadleaf forest, evergreen needleleaf forest, evergreen broadleaf shrubland, deciduous broadleaf shrubland, and grassland. Our study highlights the differences in the resilience of different vegetation types to extreme drought and indicates that surface soil moisture is an important factor affecting vegetation resistance in SWC

Interphase Effect on the Macro Nonlinear Mechanical Behavior of Cement-Based Solidified Sand Mixture

This paper investigates the interphase effect on the macro nonlinear mechanical behavior of cement-based solidified sand mixture (CBSSM) using a finite element numerical simulation method. CBSSM is a multiphase composite whose main components are soil, cement, sand and water, often found in soft soil foundation reinforcement. The emergence of this composite material can reduce the cost of soft soil foundation reinforcement and weaken silt pollution. Simplifying the CBSSM into a three-phase structure can efficiently excavate the interphase effects, that is, the sand phase with higher strength, the cement-based solidified soil phase (CBSS) with moderate strength, and the interphase with weaker strength. The interphase between aggregate and CBSS in the mixture exhibits the weak properties due to high porosity but gets little attention. In order to clarify the mechanical relationship between interphase and CBSSM, a bilinear Cohesive Model (CM) was selected for the interphase, which can phenomenologically model damage behaviors such as damage nucleation, initiation and propagation. Firstly, carry out the unconfined compression experiments on the CBSSM with different artificial gradations and then gain the nonlinear stress–strain curves. Secondly, take the Monte Carlo method to establish the numerical models of CBSSM with different gradations, which can generate geometric models containing randomly distributed and non-overlapping sand aggregates in Python by code. Then, import the CBSSM geometric models into the finite element platform Abaqus and implement the same boundary conditions as the test. Fit experimental nonlinear stress–strain curves and verify the reliability of numerical models. Finally, analyze the interphase damage effect on the macroscopic mechanical properties of CBSSM by the most reliable numerical model. The results show that there is an obviously interphase effect on CBSSM mechanical behavior, and the interphase with greater strength and stiffness ensures the macro load capacity and service life of the CBSSM; a growth in the interphase number can also adversely affect the durability of CBSSM, which provides a favorable reference for the engineering practice