Aims Here we assessed N and P uptake of four grassland species grown together in response to a short-term drought event along a soil P gradient. Methods We used 15 N and 32 P tracers to examine uptake of N and P by the grasses Bothriochloa macra , Themeda triandra , Lolium perenne and Microlaena stipoides grown together in pots with initial available P levels of 3, 8, 12, 20 mg P kg −1 soil. Soil moisture in half the pots was reduced from 60 to 30% water holding capacity during a 7-day period to simulate drought. Results Plant P uptake was strongly reduced by drought in all species across all P levels, much more so than N uptake, indicating decoupling in N and P uptake. Soil available P (Bray method) was not affected by drought, suggesting that the reduced P uptake with drought was due to reduced soil P mobility. Plant competition for N and P changed with drought and soil P levels, where relatively more N and P was taken up with drought by M. stipoides at the lowest soil P level. Conclusions We showed that greater reductions in P than in N uptake and shifts in N and P uptake among species caused by a short-term drought have strong consequences for plant growth.

中文翻译：

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沿土壤有效磷梯度受干旱影响的草地物种对氮和磷的吸收

目的 在这里，我们评估了四种草地物种在响应土壤磷梯度的短期干旱事件时对氮和磷的吸收。方法 我们使用 15 N 和 32 P 示踪剂来检查在初始有效磷水平为 3, 8, 12, 20 mg P kg 的盆中一起生长的禾本科草 Bothriochloa macra , Themeda triandra , Lolium perenne 和 Microlaena stipoides 对 N 和 P 的吸收−1 土壤。在 7 天的时间内，一半盆中的土壤水分从 60% 降低到 30% 的持水量，以模拟干旱。结果 在所有 P 水平上，所有物种的植物 P 吸收都因干旱而显着降低，远低于 N 吸收，表明 N 和 P 吸收脱钩。土壤有效磷（Bray 法）不受干旱影响，表明干旱导致磷吸收减少是由于土壤磷迁移率降低。植物对 N 和 P 的竞争随着干旱和土壤 P 水平的变化而变化，其中最低土壤 P 水平的 M. stipoides 在干旱时吸收了相对更多的 N 和 P。结论 我们表明，短期干旱引起的物种间磷吸收量的减少大于 N 吸收量的减少，以及 N 和 P 吸收量的变化对植物生长有很大的影响。