Because of its high flooding tolerance, in recent years, mulberry has become a tree species that is used in plant restoration in impact zones in reservoir areas. Therefore, 3-year-old potted forage mulberry seedlings were used to investigate the mechanism of mulberry adaptation to flooding stress. An indoor simulated flooding method was adopted to study the morphology of mulberry seedling leaves and the changes in leaf chlorophyll fluorescence parameters and fluorescence imaging under different flooding times and depths. The results showed that the leaves of mulberry seedlings treated with shallow submergence remained healthy during the flooding period, while the leaves of mulberry seedlings treated with half submergence and full submergence showed different degrees of waterlogging symptoms in the middle and late flooding periods and formed adventitious roots at the base of the stem. Most of the chlorophyll fluorescence parameters decreased at the beginning of flooding, but the steady-state degree of closure of PS II reaction centres (1-qP_Lss) increased significantly. In the later stage of flooding, the fluorescence parameters showed relatively stable trends. Based on these results, we conclude that mulberry has high flooding tolerance due to a combination of morphological and physiological responses.

Introduction: Net primary productivity (NPP) is an important indicator used to characterize the productivity of terrestrial ecosystems. The spatial distribution and dynamic change in NPP are closely related to regional climate, vegetation growth and human activities. Studying the spatiotemporal dynamics of NPP and its influencing factors plays a vital role in understanding ecosystem carbon sink capacity.Methods: Based on MODIS-NPP data, meteorological data, and land use data from 2000 to 2020, we analyzed the spatiotemporal variation characteristics and influencing factors of NPP in the middle reaches of the Yellow River (MRYR) by using unary linear regression analysis, third-order partial correlation analysis, and Sen+Mann-Kendall trend analysis.Results: The results showed that the annual average NPP of the MRYR was 319.24 gCm^-2a^-1 with a spatially decreasing trend from the southern part to the northern part. From 2000 to 2020, the annual average NPP experienced a fluctuating upward trend at a rate of 2.83 gCm^-2a^-1, and the area with a significant upward trend accounted for 87.68%. The NPP of different land use types differed greatly, in which forest had the greatest increase in NPP. Temperature had a negative correlation with NPP in most parts of the MRYR. Water vapor pressure promoted the accumulation of NPP in the northwestern MRYR. The areas with a positive correlation between NPP and water vapor pressure accounted for 87.6%, and 20.43% of the MRYR area passed the significance test of P< 0.05.Conclusion: The results of the study highlight the impact of climate factors and land-use changes on NPP and provide theoretical guidance for high-quality sustainable development in the MRYR.

This study aimed to investigate the adaptive mechanisms of mulberry (Morus alba) to waterlogged conditions, with a specific focus on the development of adventitious roots (ARs), alteration of growth strategies, and adjustment of chlorophyll fluorescence parameters. To achieve this goal, 4-year-old potted mulberry plants were selected for research, and a waterlogging simulation method was implemented. Four treatments were established to investigate the effects of varying water conditions on leaf waterlogging damage, the number of ARs, plant height, chlorophyll fluorescence parameters, and proton motive force (pmf) parameters in mulberry plants. These treatments included the control group (CK), shallow submerged group (SS), half-submerged group (HS) and deep submerged group (DS). Our results showed that (1) The number of ARs in each group increased with increasing waterlogging time. (2) Waterlogging stress inhibited the height growth of mulberry, and the changes in plant height in the HS and DS groups were significantly lower than those in the CK and SS groups. (3) The maximum photochemical quantum yield (Fv/Fm) in the HS and DS groups decreased significantly under waterlogging stress. The nonphotochemical quenching (NPQ_t) of mulberry leaves in the submergence group increased significantly in the early stage of waterlogging stress, and the NPQ_t in the submergence group increased continuously with increasing waterlogging time. (4) Thylakoid conductivity to protons (g_H⁺) in the leaves of mulberry decreased significantly under waterlogging stress, whereas the steady-state rate of proton flux (v_H⁺) and total electrochromic shift (ECS_t) increased significantly. The morphological, physiological, and ecological responses of mulberry plants to waterlogging stress include the timely generation of ARs at the stem base, the adjustment of plant growth strategies, and the repair of photosynthetic response centers in leaves through heat dissipation and thylakoid acidification mechanisms.

Preferential flow indicates that an ordinary phenomenon of rapid and non-equilibrium transport of water and solutes happens in most of soil. It causes a latent pollution of ground and surface waters and affects runoff yield and concentration. This paper studies the preferential flow movement of the dark coniferous ecosystem of Gongga Mountain, sets up the classification of the preferential flow and discusses the types of preferential flow in the reached area. Results show that the perceptible type of the preferential flow in the young, mid-aged and over-mature is macroporous flow; it is finger flow or funnel flow in the mature forest soil and will gradually transform to macroporous flow as the soil layer is deeper. The purpose of this research is to analyze systemically the law of soil water movement of dark coniferous forest ecosystem of Gongga Mountain and to provide theoretical basis for the effective watershed management.