State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, China.
Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, New Territories, Hong Kong SAR, China.
J Environ Manage. 2019 Nov 1;249:109371. doi: 10.1016/j.jenvman.2019.109371. Epub 2019 Aug 9.
Point bar areas around lakes can provide ecological service functions. For example, plants growing on point bars absorb and remove nutrients from the soil and water. However, if the point-bar plants are unregulated, in the fall and winter, plant debris will decompose, releasing nutrients that then enter the water body and cause eutrophication. Therefore, any harvesting should be managed. But how to harvest plants and how often to harvest them, and there is little research on these. In this study, the point bar at Qingcaosha Reservoir was used to study the effects of three plant harvesting modes (M1: unharvested; M2: one harvest in the fall; and M3: one harvest in summer and one in the fall) on the removal of nitrogen (N) from point-bar soil. The largest amount of N was removed by the plants when the M3 mode was used (26.93 g/m). However, the M2 mode removed the most N from the soil during the plant growth season (81.62 g/m), which implied that the nitrification and denitrification effects of soil microorganisms make the largest contribution to N removal from this point-bar soil. The nitrification and denitrification activity of microorganisms was higher for M2 than for M1 and M3 in the following year. Additionally, summer harvesting (M3) had a negative effect on nitrification efficiency in the current season because anaerobic bacteria in the soil significantly increased and nitrifying bacteria significantly decreased after harvesting. However, after a period of recovery, the number of microbial nitrifiers increased again and nitrification activity rose in the following year. The reduction in oxygen supply after harvesting may be the main reason for low nitrification in the current season, but it was beneficial to nitrification and denitrification in the following year because there was luxuriant plant growth. Therefore, when considering both the current season and the following year, harvesting should not be too frequent and one harvest in the fall (M2) led to the largest removal of N from the soil.
点滩区周围的湖泊可以提供生态服务功能。例如，生长在点滩上的植物吸收和去除土壤和水中的养分。然而，如果对点滩植物不加控制，在秋季和冬季，植物残体会分解，释放出进入水体后会导致富营养化的养分。因此，任何收割都应该进行管理。但是，如何收割植物以及多久收割一次，这些方面的研究很少。在这项研究中，以青草沙水库的点滩区为例，研究了三种植物收割模式（M1：不收割；M2：秋季收割一次；M3：夏季和秋季各收割一次）对点滩土壤中氮（N）去除的影响。当使用 M3 模式时，植物去除的 N 量最大（26.93 g/m）。然而，在植物生长季节，M2 模式从土壤中去除的 N 量最多（81.62 g/m），这意味着土壤微生物的硝化和反硝化作用对点滩土壤中 N 的去除贡献最大。第二年，M2 模式下的微生物硝化和反硝化活性高于 M1 和 M3。此外，夏季收割（M3）对本季硝化效率有负面影响，因为收割后土壤中厌氧菌明显增加，硝化菌明显减少。然而，经过一段时间的恢复，微生物硝化菌的数量再次增加，次年硝化活性上升。收割后氧气供应的减少可能是本季硝化作用降低的主要原因，但对次年的硝化和反硝化作用是有利的，因为植物生长茂盛。因此，从当年和次年两季综合考虑，收割不应过于频繁，秋季收割一次（M2）可使土壤中 N 的去除量最大。
