The development of the Xiong’an New Area is a crucial strategy for the next millennium in China. The ecosystem upstream of the Xiong’an New Area, serving for the development of the Xiong’an New Area, changed with land use changes. To analyze the contribution rate of the land use change to the ecosystem service value, we analyzed the land use changes of three small watersheds (7318.56 km²) upstream of the Xiong’an New Area based on a total of six phases of land use data from 1980 to 2015. Then, the ecosystem service value (ESV) was calculated using the equivalent factor method. The results showed that the construction land and arable land were the largest land use types that increased and decreased in the area of the study area, respectively. The grassland and construction land were the land use types with the largest transfer-out area and transfer-in area, respectively. The regulating services accounted for the largest proportion of total ESV among different ecosystem service functions, and the grassland and woodland accounted for the largest proportion of total ESV among different land use types. ESV in the study area fluctuated slightly from 1980 to 2015. The decrease of ESV mainly occurred in the surrounding areas of mountain towns, and the conversion of cultivated land to construction land was the main reason for the decrease of ESV in this area. The conversion of grassland to construction land had the largest contribution rate to the decrease of ESV in the study area, while the conversion of grassland to waters had the largest contribution rate to the increase of ESV. In conclusion, controlling the development of construction land and strengthening water resources’ protection may improve the ecosystem service value in the upstream Xiong’an New Area in the future.

Clarifying the interrelationship between climate and land use/land cover (LULC) changes on water yield in mountainous areas is very urgent due to the dramatic decrease in the water availability of mountainous areas. In this study, the InVEST model was used to calculate the water yield of the mountainous area in Beijing–Tianjin–Hebei region (BTH) from 1980 to 2020, and six scenarios were designed to identify the contribution rates of climate and LULC change on the water yield. The results showed that, in 1980–2020, the water yield in the mountainous area of BTH was the largest in 1990, at 377.95 mm and the smallest in 1980, at 150.49 mm. After 2000, the interannual water yield showed a slightly increasing trend, which was significantly lower than the water yield in 1990, the values ranging from 217.01 mm to 324.65 mm. During the study period, the spatial distribution of the water yield was similar over the years, with high values in the south-central Taihang Mountain (THM) and the northeastern Yanshan Mountain (YSM). The THM was the main water yield area of the mountainous area in BTH. The annual water yield of farmland was the highest, followed by forest land and grassland, while the proportion of volumetric water yield was the largest in forest land with an increasing trend from 1980 to 2020 and the grassland showed a decreasing trend, while that of farmland increased first from 1980 to 2000 and decreased from 2000 to 2020. Climate is the key factor controlling the water yield of the mountainous area in BTH from 1980–2000, 2000 to 2020, and 1980 to 2020. In the period of 2000–2020, the effect of LULC on the water yield is negative, while the effect is positive in 1980–2000 and 1980–2020. The contribution rate of climate to the water yield increases in the THM, Bashang region (BSR) and YSM from the period 1980–2000 to 2000–2020, while that of LULC in those three regions changes from a positive impact in 1980–2000 to a negative impact in 2000–2020, and the contribution rate is also greatly reduced. In the long term, land revegetation will gradually benefit the water yield in the mountainous areas of BTH, including the THM, BSR, and YSM. These results can provide an important scientific and technological reference for the ecological management and protection of water source sites, as well as the planning and utilization of water resources in mountainous areas of BTH.

Climate warming has and will continue to exert a significantly impact on crop phenology in the past and coming decades. Combining observed data of phenology and a crop growth model provides a good approach for quantitating the effects of climate warming and crop management on crop phenology. The purpose of this study is to determine the impacts of temperature change, sowing date (SD) adjustment and cultivar shift on maize phenology in northern China during 1981–2010. Results indicated that climate warming caused anthesis date (AD) and maturity date (MD) of maize to advance by 0.2–5.5 and 0.6–11.1 d/10a, respectively. Due to climate-driven changes in maize phenology, three growth periods of maize, i.e., vegetative growth period (VGP; from sowing to anthesis), reproductive growth period (RGP; from anthesis to maturity) and whole growth period (WGP; from sowing to maturity) shortened by 0.2–5.5, 0.4–5.6 and 0.6–11.1 d/10a, respectively. With SD adjustment (i.e., SD advancement), AD and MD occurred early by 0.5–2.6 and 0.1–3.4 d/10a, respectively. SD adjustment caused duration of VGP of maize to prolong. However, duration of RGP slightly shortened by 0.1–1.3 d/10a. Furthermore, due to cultivar shift, MD of maize significantly delayed by 4.9–12.2 d/10a. Durations of VGP, RGP and WGP of maize prolonged by 0.2–4.1, 1.6–8.4 and 4.3–11.8 d/10a, respectively. In conclusion, our results indicated that cultivar shift, to some extent, could mitigate the negative impact of climate warming on maize phenology.

Litter decomposition is a prominent pathway for nutrient availability and management in terrestrial ecosystems. An in-situ litter decomposition experiment was carried out for different land use types along an elevation gradient in the Taihang Mountain area restored after heavy forest degradation in the past. Four land use types, i.e., cropland, shrubland, grassland, and forest, selected randomly from a 300–700 m elevation were investigated for the experiment using the litter bag technique. Litter mass loss ranged from 26.9% (forest) to 44.3% (cropland) varying significantly among land use types. The initial litter quality, mainly N and C/N, had a significant effect on the litter loss rate. The interaction of elevation × land use types × time was significant (p < 0.001). Litter nutrient mobility (K > P ≈ N > C) of the decomposing litter was sporadic with substantial stoichiometric effects of C/N, N/P, and C/P. The residual litters were enriched in ¹⁵N and depleted in ¹³C as compared to the initial litter. Increment of N, P, and δ¹⁵N values in residual litter indicates that, even in the highly weathered substrate, plant litter plays a crucial role in conserving nutrients. This study is a strong baseline for monitoring the functioning of the Taihang Mountain ecosystem restored after the complete destruction in the early 1990s.

Groundwater evapotranspiration (ET_g) is an important component of the hydrological cycle in water-scarce regions and is important for local ecosystems and agricultural irrigation management. However, accurate estimation of ET_g is not easy due to uncertainties in climatic conditions, vegetation parameters, and the hydrological parameters of the unsaturated zone and aquifers. The current methods for calculating ET_g mainly include the WTF method and the numerical groundwater model. The WTF method often requires data supplementation from the numerical unsaturated model to reduce uncertainty; in addition, it relies on point-monitoring data and cannot solve the spatial heterogeneity of ET_g. The ET_g calculation module of the numerical groundwater model is set up too simply and ignores the influence from the unsaturated zone and surface cover. Subsequent research breakthroughs should focus on the improvement of WTF calculation theory and the setting up of an aquifer water-table fluctuation monitoring network. The numerical groundwater model should couple the surface remote sensing data with the unsaturated zone model to improve the accuracy of ET_g calculation.

Forest water conservation function is an important part of forest ecosystem services. The discontinuous distribution of forests in semiarid areas brings difficulties to the quantitative evaluation of forest water conservation functions at the basin scale. In this paper, we took the upstream of Xiong’an New Area (Zijingguan—ZJG, Zhongtangmei—ZTM and Fuping—FP basins) as an example and combine the soil and water assessment tool (SWAT) and the water balance method to calculate the amount of forest water conservation (AFWC) at annual, monthly and daily scales from 2007 to 2017, and analyzed the changes of AFWC. The results showed that the hydrological response unit (HRU) generated with the threshold area zero can accurately reflect the forest patch distribution in the three basins. On an annual scale, the annual AFWC were all positive in ZJG and ZTM basins from 2007 to 2017. While, the annual AFWC in the FP basin was negative in 2009, 2013, 2014 and 2017. On a monthly scale, the positive values of AFWC mainly appear from June to September, and the negative values of AFWC mainly appear from December to March. On a daily scale, the AFWC during extreme precipitation was positive, while that was negative during extreme drought. The annual and monthly AFWC in the three basins was positively correlated with the wetness index, and FP basin needs more humid climate conditions than ZJG and ZTM basins to make the forest store water and keep in a stable water storage state. The above results can not only provide important insight into sustainable forest and water resources management in the region, but also serve as reference cases for other regions to carry out relevant research work.