Wang Fugang, Shi Lei, Zhang Ruiyi, Xu Weizhou, Bo Yaojun
College of Life Science, Yulin University, Yulin, China.
Shaanxi Engineering Research Center of Forage Plants of the Loess Plateau, Yulin University, Yulin, Shaanxi, China.
Front Plant Sci. 2024 Jun 24;15:1400309. doi: 10.3389/fpls.2024.1400309. eCollection 2024.
Grass-legume mixture can effectively improve productivity and stimulate overyielding in artificial grasslands, but may be N-limited in semi-arid regions. This study investigated the effects of N addition on chlorophyll fluorescence and production in the grass-legume mixtures community.
An N addition experiment was conducted in the and mixture community, with seven mixture ratios (B0L10, B2L8, B4L6, B5L5, B6L4, B8L2, and B10L0) according to the sowing abundance of and and four N addition levels, N0, N25, N50, and N75 (0,25,50,75kgNhm a), respectively. We analyzed the response of chlorophyll fluorescence parameters of the two species, the rapid light-response curves of chlorophyll fluorescence, as well as aboveground biomass (AGB) and overyielding.
Our results showed that the two species showed different photosynthetic strategies, with having significantly higher initial fluorescence (Fo), effective photochemical quantum yield of PSII (ΦPSII), and coefficient of photochemical fluorescence quenching (qP) than , consisting with results of rapid light-response curves. N addition and mixture ratio both had significant effects on chlorophyll fluorescence and AGB (<0.001). The ΦPSII and qP of were significantly lowest in B5L5 and B6L4 under N addition, and the effect of N varied with mixture ratio. The photosynthetic efficiency of was higher in mixture than in monoculture (B10L0), and ΦPSII was significantly higher in N50 than in N25 and N50 at mixture communities except at B5L5. The community AGB was significantly higher in mixture communities than in two monocultures and highest at B6L4. In the same mixture ratio, the AGB was highest under the N50. The overyielding effects were significantly highest under the N75 and B6L4 treatments, mainly attributed to The partial least squares path models demonstrated that adding N increased soil nutrient content, and complementary utilization by and increased the photosynthetic efficiency. However, as the different photosynthetic strategies of these two species, the effect on AGB was offset, and the mixture ratio's effects were larger than N. Our results proposed the B6L4 and N50 treatments were the optimal combination, with the highest AGB and overyielding, moderate grass-legume ratio, optimal community structure, and forage values.
禾本科-豆科混合群落能有效提高人工草地生产力并促进超产，但在半干旱地区可能受氮限制。本研究调查了施氮对禾本科-豆科混合群落叶绿素荧光和产量的影响。
在该混合群落中进行了施氮实验，根据和的播种丰度设置了七个混合比例（B0L10、B2L8、B4L6、B5L5、B6L4、B8L2和B10L0）以及四个施氮水平，分别为N0、N25、N50和N75（0、25、50、75kgNhm² a）。我们分析了两种植物叶绿素荧光参数的响应、叶绿素荧光的快速光响应曲线，以及地上生物量（AGB）和超产情况。
我们的结果表明，两种植物表现出不同的光合策略，的初始荧光（Fo）、PSII的有效光化学量子产率（ΦPSII）和光化学荧光猝灭系数（qP）显著高于，这与快速光响应曲线的结果一致。施氮和混合比例对叶绿素荧光和AGB均有显著影响（<0.001）。施氮条件下，在B5L5和B6L4中，的ΦPSII和qP显著最低，且氮的影响随混合比例而变化。在混合群落中，的光合效率高于单作（B10L0），除B5L5外，在混合群落中，N50处理下的ΦPSII显著高于N25和N50处理。混合群落的群落AGB显著高于两种单作群落，在B6L4时最高。在相同混合比例下，N50处理下的AGB最高。在N75和B6L4处理下，超产效应显著最高，主要归因于。偏最小二乘路径模型表明，施氮增加了土壤养分含量，和的互补利用提高了光合效率。然而，由于这两种植物不同的光合策略，对AGB的影响被抵消，且混合比例的影响大于氮。我们的结果表明，B6L4和N50处理是最佳组合，具有最高的AGB和超产，适中的禾本科-豆科比例以及最佳的群落结构和饲用价值。
