Hao Ding

In the context of global climate change, understanding the tradeoffs and synergies between ecosystem services (ESs) is essential for regional ecological management and sustainable development. This study simulated net primary productivity (NPP) and quick flow (QF) in the Middle Reaches of the Yellow River Basin (MRYRB) in 2000 and 2020, utilizing the Carnegie–Ames–Stanford Approach (CASA) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) models to assess ESs related to carbon sequestration (CS) and water yield (WY). The synergistic multi‐temporal scale changes in ESs tradeoffs under different drought conditions were assessed by delineating regions with different drought frequencies. The results showed that (1) the mean NPP in the MRYRB increased from 189.03 g C/m ² in 2000 to 335.94 g C/m ² in 2020, reflecting a 77.71% rise, while the mean annual QF escalated from 41.20 mm in 2000 to 59.59 mm in 2020, marking an increase of 44.64%; (2) on a monthly scale, the tradeoff and synergy relationships exhibited distinct seasonal variations, with tradeoffs prevailing throughout the year and a shift from tradeoff to synergy in CS and WY during the summer and fall. On an annual scale, synergy was the dominant relationship; (3) the intensity of tradeoffs and synergies varied by drought gradients, with the highest intensity observed in high‐frequency drought areas at the monthly scale, whereas, on an annual scale, low‐frequency drought areas exhibited the strongest tradeoffs and synergies. This study provides an in‐depth analysis of the interactions between ESs under varying drought conditions across different time scales. The findings highlight the distinct differences in tradeoffs and synergies of ESs, offering valuable scientific insights for the coordinated management of regional ecosystems.

Against the background of climate change, the global carbon and water cycle has undergone significant changes, and it is of great significance to explore the interrelationships of the carbon and water cycles in different regions to cope with future climate change. In this study, based on gross primary productivity (GPP) and precipitation (PRE) data, the precipitation use efficiency (PUE) of the Loess Plateau (LP) was calculated, and the Sen trend analysis and Mann‐Kendall test were used to analyse the temporal and spatial variation characteristics of PUE, as well as the first‐order difference method was used to derive the relative contributions to quantify the impact of vegetation growth and meteorological factors on PUE. The results show that (1) from 2001 to 2018, the spatial distribution pattern of vegetation PUE exhibited an increasing trend from northwest to southeast. On the time scale, the multi‐year average value of PUE was 1.17 gC m⁻² mm⁻¹, showing an overall upward trend. Among the different land cover types, paddy fields had the highest PUE level, and sparse grassland had the lowest; (2) LAI had the highest relative contribution to vegetation PUE, followed by temperature (Temp), net radiation of the ground surface (RN), specific humidity (Shum), and wind speed (WS). LAI contributes positively to 88.9% of the area. RN positively influences high‐altitude areas, while Shum had a larger area with a negative contribution. The contribution of Temp increases from northwest to southeast, and WS has balanced positive and negative contributions; (3) LAI is the dominant factor for the spatial and temporal variation of PUE in the LP, and the size of the areas where different meteorological factors dominate the changes of PUE are as follows: WS > Shum>RN > Temp. At high altitudes, the dominant meteorological driver is WS, while at low altitudes, the dominant climate driver is Shum. This study is of guiding significance for the ecological restoration and management of the LP, and it can also provide a scientific basis for the improvement of ecosystems and the sustainable management of water resources in the context of global climate change.

The increasing impact of drought stress on ecosystems with regard to climate change has received considerable attention, which has been demonstrated to have a time‐lag effect on ecosystems. However, the time‐lag effect on different types of droughts and gross primary production (GPP) at large regional scales remains unclear. Thus, using the GOSIF GPP product data of solar‐induced chlorophyll fluorescence, the meteorological drought index (standardized precipitation evapotranspiration index [SPEI]), and the agricultural drought index (soil moisture deficit index [SMDI]) based on the soil moisture data obtained from the Global Land Data Assimilation System, the time‐lag effect of regional drought and GPP and the contribution of drought to GPP variation were analysed in China from 2000 to 2018. Results showed that (1) China's annual GPP increased at an average rate of 9.26 g C m⁻² y⁻¹. With regard to the average rate for each climate zone, the largest increase of 30.44 g C m⁻² y⁻¹ was observed in the southern subtropical region, and the smallest increase (4.01 g C m⁻² y⁻¹) was observed in the Qinghai–Tibetan plateau, with about 53.11% of the regions showing a significant upward trend. In addition, the significantly declining regions were primarily concentrated in urban areas, accounting for about 2.26% of China. (2) SPEI and GPP had an average lag time of 6.28 months, whereas SMDI and GPP had an average lag time of 7.17 months. The comparison demonstrated that SMDI had a greater influence on GPP than SPEI. (3) The average contribution rate of meteorological drought and agricultural drought to the decrease of GPP was 79.37% and 87.06%, and their average contribution rate to the increase of GPP was 39.11% and 50.57%, respectively. This study will provide comprehensive understanding of the effects of drought on carbon and water cycles in terrestrial ecosystems with regard to climate change.

Drought is one of the most destructive natural disasters in China and can cause serious environmental and socio-economic impacts. Based on monthly precipitation and temperature data from 571 meteorological stations, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated on a 12-month scale (SPEI-12) from 1985 to 2018 in mainland China, and it was compared with the records of the Bulletin of Flood and Drought Disasters in China to verify its drought monitoring accuracy. Then, run theory was used to explore in depth the spatiotemporal distribution of drought characteristics and trends in various climatic sub-regions. The results showed that: (1) the comparison with the Bulletin of Flood and Drought Disasters in China indicated that the results of SPEI-12 monitoring drought had high accuracy and could identify drought events in mainland China. (2) About 70% of the regions in mainland China experienced droughts more than 50 times, and about 43% of the regions had drought durations of between 100 and 110 months. Nearly 11% of the regions had drought severities of more than 130, which were mainly located in the Northwest Desert (NWC), the southern part of Northeast China (NEC), and the western part of North China (NC). (3) In the past 34 years, the droughts in the Northwest Desert (NWC), the western part of Inner Mongolia (IM), and the Qinghai-Tibet Plateau (TP) showed an aridity trend, while the droughts in South China (SC) and eastern Central and South China (CSC) presented a mitigation tendency. (4) Specifically, the droughts in South China (SC) were more influenced by precipitation, while those in the Northwest Desert (NWC) and Northeast China (NEC) were influenced by temperature and potential evapotranspiration, and the evolution of drought in North China (NC) and the Qinghai-Tibet Plateau (TP) was mainly influenced by soil moisture. The study could provide scientific guidance and a reference for drought response and sustainable development in China.

Under the background of climate warming, the increase in the frequency and severity of drought leads to vegetation facing severe challenges. A comprehensive and systematic assessment of the stability of vegetation under drought stress in the middle reaches of Yellow River basin (MRYRB) will help to grasp the characteristics of vegetation response to drought. In this study, the normalized difference vegetation index (NDVI) was used to achieve quantitative and qualitative assessments of vegetation stability to drought, and the smoothed monthly standardized precipitation evapotranspiration index (SPEI) was used to describe the characteristics of drought events in 2005/2006 and identified vegetation stability parameters using a standardized anomaly of NDVI across space, which included the resistance duration, resilience duration, drought threshold, and lag time. Vegetation was dominated by less resistance and less resilience. The 2005/2006 drought event affected most of the study area, and vegetation growth was inhibited. The duration of vegetation resistance over 100 days accounted for 65.7%, and vegetation in 89.4% of the regions could return to normal within 100 days. The drought threshold of vegetation gradually decreased from northwest to southeast, and the lag time was mainly concentrated from 1 to 3 months. These findings contribute to a better understanding of the effects of drought on the environment, as well as scientific references for reducing ecological, economic, and social losses in future droughts, and promoting ecological environmental governance and high-quality development in the MRYRB.

The frequency and intensity of droughts are increasing in many parts of the world as a result of global climate change and human activity, posing a serious threat to regional ecological security. The climate in the middle reaches of the Yellow River Basin (MRYRB) has been warm and dry in recent years, with frequent droughts. In order to investigate the temporal trend of drought, and reveal the resistance of vegetation to drought in the MRYRB, this study used remotely-sensed vegetation index products (MODIS-NDVI and SPOT-NDVI) and the standardized precipitation evapotranspiration index (SPEI). The results indicated that: (1) drought intensity showed a weak upward trend in the study area from 2000 to 2018, with linear growth rates of SPEI at temporal scales of 1, 3, 6, 9 and 12 months of −0.002, 0.0034, 0.0198, 0.0234, and 0.0249, respectively; (2) drought was positively correlated with vegetation in most areas (97.6%), and vegetation was most affected by drought on long-term time scales (9 and 12 months); (3) with the extension of drought, vegetation resistance index decreased, then gradually recovered after the end of the drought. Forest had the longest resistance duration of 260 days, while grassland and cultivated land had resistance durations of only 170 days. This study adds to the understanding of vegetation’s ability to withstand drought, and these findings provide evidence to support drought response in the MRYRB.

In this work, the biomacromolecule, single‐stranded deoxyribonucleic acid (ssDNA) was innovatively incorporated into the polyamide layer to tailor the permeate flux and antifouling performance of the nanofiltration (NF) membranes. With active amines groups, the ssDNA was as the aqueous phase monomers along with piperazine (PIP), and reacted with trimesoyl chloride on polyethersulfone substrate to fabricate thin‐film composite (TFC) NF membranes. The NF membrane prepared under optimal ratio of ssDNA/PIP had a pure water permeability of 75.8 L m⁻² h⁻¹ (improved 58% compared to PIP NF membrane) and Na₂SO₄ rejection of 98.0% at 6.0 bar. The rejections for different inorganic salts were the order: Na₂SO₄ (98.0%) > MgSO₄ (89.2%) > MgCl₂ (72.8%) > NaCl (23.0%). Furthermore, the TFC NF membranes showed good antifouling performance in long‐term running with 300 ppm bovine serum albumin and humic acid solution. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 47102.