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High yields and low carbon emissions are new challenges for modern crop production. Balancing the crop yield and reducing greenhouse gas (GHG) emissions has become a new field of agronomic technology innovation. Cereal–legume intercropping is a typical diversification planting system, which has been expected to achieve the dual goals of high production and low GHG emissions. However, the synergistic effect of integrating various technologies in an intercropping system on GHG emissions and whether it will achieve the high yield and low emissions goal remains to be determined. Therefore, bibliometric analysis has investigated the worldwide development trend of cereal–legume intercropping designs. The literature on the GHG emissions of the cereal–legume intercropping system was summarized. Additionally, the effects and mechanisms of different agricultural management methods regarding soil nitrous oxide and carbon dioxide emissions in the cereal–legume intercropping system were summarized. The research on GHG emissions of cereal–legume intercropping systems in non-growing seasons must be revised. In situ observations of GHG emissions from intercropping systems in different regions should be strengthened. This work is valuable in supporting and evaluating the potential of GHG reduction in a cereal–legume intercropping system in various farming areas. [ABSTRACT FROM AUTHOR]

There have been a number of studies on biogeographic patterns of plant leaf functional traits; however, the variations in traits of other plant organs such as twigs are rarely investigated. In this study, we sampled current-year twigs of 335 tree species from 12 forest sites across a latitudinal span of 32 degrees in China, and measured twig specific density (TSD), twig dry matter content (TDMC), and carbon (C), nitrogen (N) and phosphorous (P) contents, to explore the latitudinal and environmental patterns of these twig traits. The overall mean of TSD and TDMC was 0.37 g cm−3 and 41%, respectively; mean twig C, N and P was 472 mg g−1, 9.8 mg g−1 and 1.15 mg g−1, respectively, and mean N:P mass ratio was 10.6. TSD was positively correlated with TDMC which was positively associated with twig C but negatively with twig N and P. There were no significant differences in TSD between conifer, deciduous-broadleaf and evergreen-broadleaf plants, but evergreen-broadleaf plants had the lowest and conifers the highest TDMC. Conifer twigs were lowest in C, N, P and N:P, whereas deciduous-plant twigs were highest in N and P and evergreen-plant twigs were highest in C and N:P. As latitude increased or temperature/precipitation dropped, TDMC and P increased, but N:P ratio decreased. Our results also showed that the patterns of twig P and N:P stoichiometry were consistent with those reported for leaves, but no significant trends in twig N were observed along the gradient of latitude, climate and soils. This study provides the first large-scale patterns of the twig traits and will improve our understanding of the biogeochemistry of carbon and other key nutrients in forest ecosystems. [ABSTRACT FROM AUTHOR]

Highlights • Maize yield increased more in inbred lines from 1960s to 1980s than 1980s to 2000s. • Soil water-nitrogen uptake and utilization efficiency were more effective and economic. • Modern inbred lines produce less roots in top soil layer but more in deeper soil. • Roots have greater physiological absorption capacity rather than being large. Abstract The evolution of canopy traits related to maize yield increases has been well documented, but the changes in the root system over decades and their relationships with the water use efficiency (WUE) and nitrogen (N) use efficiency (NUE) require further investigation. In this study, we analyzed the morphological and physiological characteristics of the roots, as well as the water-N uptake, WUE, and NUE under low water/N (LW/LN) and high water/N (HW/HN) supply levels in 11 elite inbred maize lines released in China during the 1960s, 1980s, and 2000s. The results showed that yield improvement in the inbred lines from the 1960s to the 1980s (61–109%) was greater than that in those from the 1980s to the 2000s (6–17%), and the resistance to drought and low N also exhibited a significant linear increase over the decades. The utilization of water and N by the inbred lines evolved efficiently and economically, especially in stressful environments. The improved WUE of modern inbred lines was demonstrated by the higher yield and lower evapotranspiration. The NUE defined as the grain yield obtained per unit of N in plants increased in a linear manner over the three decades, and it was accompanied by higher N accumulation in the grains and greater N translocation efficiency in the roots. However, the agronomic N use efficiency improved from the 1960s to the 1980s, but then decreased from the 1980s to the 2000s. The modern inbred lines tended to produce less redundant roots in the top (0–20 cm) soil layer, whereas root development was enhanced in the deeper soil layer. The morphological properties of the roots (dry weight, length, volume, surface area, weight density, and length density) tended to increase from the 1960s to the 1980s but then decreased from the 1980s to the 2000s, and they had significant quadratic relationships with the yield, WUE, and NUE. By contrast, water/N amount absorbed per unit root volume, the physiological properties related to the root absorption area, root activity improved over the decades, where the physiological properties had positive linear relationships with the yield, WUE, and NUE. Thus, we conclude that the maize roots evolved alongside higher yields and greater tolerance to drought and low N environments. The improved WUE and NUE in the modern inbred lines were associated with the greater physiological absorption capacity of the roots rather than larger root size in normal or stressful environments. [ABSTRACT FROM AUTHOR]