Evapotranspiration (ET) determines the crop productivity in rain-fed agriculture. Global climate change alters the trade-off between soil water supply and atmospheric demand, energy partitioning, and community biophysical and structural properties; however, the interactive effects of these biotic and abiotic factors on ET and its components remain unclear. ET was measured in 2005–2020 in a rain-fed maize ecosystem in northeastern China using the eddy covariance method. By decomposing ET into transpiration (T) and evaporation (E) with the Shuttleworth–Wallace model, we investigated the abiotic and biotic interactive effects on ET and its components at annual levels. Results showed that available energy and albedo exhibited no significant time-series trends, but the Bowen ratio exhibited an increasing trend. Precipitation exhibited no significant trends; however, soil water content (SWC) decreased with time, accompanied by significantly increased air temperature (Ta) and a vapor pressure deficit (VPD). The ET decline was controlled by T, rather than E. The T decline was mainly controlled by canopy conductance and SWC. CO₂ concentrations and the VPD exhibited indirect effects on T by reducing canopy conductance, while Ta and precipitation had indirect effects on T by reducing SWC. Our results indicated that decreasing ET may be more severe with crop physiological adaptability for a decreased SWC. Aiming to enhance water resource efficiency, the practice of returning crop residues to the field to reduce soil evaporation, coupled with adjusting the sowing time to mitigate the risk of seasonal droughts during critical growth stages, represents an effective strategy in agricultural water resource management.

Salt stress is a limiting factor affecting the growth, development, and yield of peanuts. Breeding improvement is a possible solution to overcome salt stress. The salt tolerance of 57 peanut cultivars in Northeast China was identified using indoor simulation at the germination stage, the seedling stage, and field natural identification. At the germination stage, 75 mM NaCl was the most suitable screening concentration, and the seed vitality index of 57 cultivars was analyzed using the membership function and cluster analysis. Among these cultivars, 11 were identified as salt-tolerant and 19 were salt-sensitive during germination. In the seedling stage, six salt tolerance coefficients (STCs) showed significant correlation. A gray relational analysis was used in combination with evaluation grading, resulting in the identification of 14 salt-tolerant cultivars and 12 salt-sensitive cultivars. In the field screening, a comprehensive analysis was conducted using a principal component analysis of nine indices, including agronomic characteristics, yield characteristics, and SPAD. This analysis led to the determination of three comprehensive indices. The weighted membership function was used for comprehensive evaluation. Finally, three salt-tolerant cultivars and four salt-sensitive cultivars suitable for planting in Northeast China were screened out to provide an excellent germplasm for researching the salt-tolerant mechanism of peanuts.

Interannual variability (IAV) in net ecosystem carbon production (NEP) plays an important role in the processes of the carbon cycle, but the long-term trends in NEP and the climatic and biotic control of IAV in NEP still remain unclear in agroecosystems. We investigated interannual variability in NEP, expressed as annual values and anomalies, and its climatic and biotic controls using an eddy-covariance dataset for 2005–2018 for rain-fed spring maize in northeastern China. Average annual NEP was 270±31 g C m⁻²yr ⁻¹, with no significant changes over time. The effects on interannual variability in NEP of gross ecosystem productivity (GEP) that was mainly controlled by soil water content (SWC) and leaf area index (LAI), were more than those of respiration (RE) that was controlled by temperature and LAI. Further, maximum daily NEP (NEP_max) that was dominated by summer vapor pressure deficit explained the largest fraction of annual anomalies in NEP, followed by carbon dioxide uptake period (CUP) that was defined by the beginning date (BDOY) and the end date (EDOY) of CUP. The variability in BDOY was mainly determined by spring precipitation and the effective accumulated temperature, and the variability in EDOY was determined by autumn precipitation, SWC and LAI. NEP may decrease with declining precipitation in the future due to decreasing GEP, NEP_max, or CUP, and irrigation and residues cover may be useful in efforts to maintain current NEP levels. Our results indicate that interannual variability in NEP in agroecosystems may be more sensitive to changes in water conditions (such as precipitation, SWC and VPD) induced by climate changes, while temperature may be an important indirect factor when VPD is dominated.

In the context of global climate change, atmospheric nitrogen deposition is increasing, and precipitation patterns are becoming more variable. This study examines the impact of these changes on nitrogen (N) allocation mechanisms in semi-arid region tree species using one-year-old Mongolian pine (Pinus sylvestris var. mongolica) seedlings. The seedlings were planted in soil collected from the Daqinggou Sandy Ecological Experiment Station (42°54′ N, 122°25′ E). Three moisture treatments were applied (WC (normal moisture, approximately 65% ± 2.5% of the field capacity), WI (30% increased moisture), and WD (30% decreased moisture)), as well as three nitrogen treatments (NC (no nitrogen), NL (5 g·m⁻²·y⁻¹ nitrogen), and NH (10 g·m⁻²·y⁻¹ nitrogen)). The seedlings were sprayed with a ¹⁵N-labeled CH₄N₂O solution (46% N, ¹⁵N abundance 10.14%) in a pot trial, with samples taken in August and October to measure N content and ¹⁵N abundance in the seedling organs and the soil. Parameters such as N_dff (%) (the percentage of nitrogen derived from fertilizer), nitrogen content of organs, ¹⁵N absorption in organs, and ¹⁵N distribution ratio were calculated. The results showed that ¹⁵N allocation in seedlings followed the trend leaves > stems > roots. Under moisture treatments, ¹⁵N allocation ratios in leaves, stems, and roots were 63.63–71.42%, 14.89–24.14%, and 12.23–14.88% under low nitrogen, and 62.63–77.83%, 13.35–22.90%, and 7.31–19.18% under high nitrogen. Significant correlations were found in ¹⁵N abundance among the seedling organs, with coefficients ranging from 0.97 to 1.00. The main effects of moisture and nitrogen, as well as their interaction, significantly impacted ¹⁵N abundance in the seedling organs. Changes in moisture levels affected the nitrogen absorption capacity of Mongolian pine. Increased moisture significantly enhanced ¹⁵N absorption in all organs, leading to 62.63–71.42% of ¹⁵N being allocated to the leaves, maintaining an appropriate proportion with the roots and stems. Nitrogen deposition altered the nitrogen allocation strategy among different organs of Mongolian pine. Under conditions of reduced moisture and low nitrogen, a greater proportion of nitrogen was captured by the roots and stems, with an allocation increase of approximately 4.98–5.77% compared to the control group, thereby mitigating the adverse effects of water deficiency. In conditions of reduced moisture and high nitrogen, the leaves, being active organs, accumulated more limiting elements, with an increase in nitrogen allocation of 2.03–8.07% compared to the control group. To achieve an optimal allocation strategy, moderate nitrogen deposition combined with increased moisture enhanced nitrogen uptake in Mongolian pine seedlings. This study provides scientific evidence for ecological restoration, wind erosion control, and agricultural and forestry management in semi-arid regions under the context of global climate change.

Global climate change presents a significant threat to food security. Analyzing the effects of elevated ozone (O₃) concentration on photosynthetic fluorescence characteristics and yield addresses the damage of climate change on crops, which would serve food security. With open-top chambers (OTCs) and Tiefeng-29 soybeans, we investigated the responses of chlorophyll concentration, fluorescence characteristics, net photosynthetic rate (Pn) and yield components to different O₃ concentrations, which included CK (ambient concentration approximately 45 nL·L⁻¹, T1 (80 ± 10) nL·L⁻¹ and T2 (120 ± 10) nL·L⁻¹ O₃. The parent soybeans (S1) were planted in the current year, and O₃ fumigation commenced 20 days after seedling emergence. Aeration was stopped at maturity, and the offspring soybeans (S2) were retained after harvest for further experiments. In the following year, S1 and S2 soybeans were planted, and O₃ fumigation began 20 days after seedling emergence. The results show that leaf chlorophyll a (chla) and chlorophyll b (chlb) significantly decreased with longer O₃ fumigation time both in parents and offspring, causing damage to the light-trapping ability while the offspring suffered an earlier decrease. The elevated O₃ damaged the electron transfer process by significantly reducing the original and actual photochemical efficiencies of PSII both in parents and offspring. The electron transfer rate (ETR) of the parents and offspring decreased, while the difference between them was not significant after O₃ treatment. The non-photochemical quenching coefficient (NPQ) showed an increasing trend along time but showed no significant difference between parents and offspring. An elevated concentration of O₃ significantly reduced Pn, while the differences in Pn between the parents and the offspring were not significant. Elevated O₃ resulted in reduced yields in both parent and offspring soybeans. Although it was found that the offspring soybeans exhibited higher yields than the parents, their reduction in yield was more significant. Therefore, elevated O₃ concentration reduced soybean yield through damaging photosynthetic process and electron transfer capacity by impairing energy conversion and material accumulation capacity. The offspring had relatively higher light energy conversion efficiency than the parents, resulting in a higher yield than the parents under all treatments.