Root exudation is affected by the soil water content (SWC) and availability of nutrients, but the impact of the interaction between these abiotic factors is unclear. Understanding the combined effect of these factors is vital for all ecosystems, including Mediterranean forests, where droughts are increasing. A greenhouse experiment was established with a drought treatment (control versus drought) and the subsequent recovery, factorially combined with four nutrient treatments (control, nitrogen (N) addition, phosphorus (P) addition, and both N and P addition). N was added as ammonium nitrate at a rate of 50 kg N ha⁻¹ and P was added as calcium phosphate at a rate of 25 kg P ha⁻¹. Exudation of total organic carbon (TOC) was measured from the roots of 64 saplings of each of two important tree species that coexist in montane Mediterranean regions, Pinus sylvestris (Scots pine) and Quercus ilex (holm oak). The amount of TOC released from individual roots of the saplings was measured to estimate root exudation per gram of root mass. Chlorophyll fluorescence (F_v/F_m) was also monitored to check for treatment effects on leaf performance. Chlorophyll fluorescence was not affected by SWC or nutrient addition in either species, but root exudation was, and varied between the two species. SWC was positively correlated with the amount of TOC released during the drought period for Q. ilex but had no effect on P. sylvestris. The addition of P increased root exudation in Q. ilex. The amount of TOC released in the recovery period for both species with no added nutrients was weakly negatively correlated with SWC during the drought period, potentially indicating a delayed positive effect of the earlier water stress. SWC positively affected the amount of TOC collected from the roots when P was added for both species and when N was added for P. sylvestris. Our results indicate that the impacts of drought on root exudation will likely vary between species and will depend on the availability of soil nutrients.

根系分泌物受土壤含水量 (SWC) 和养分有效性的影响，但这些非生物因素之间相互作用的影响尚不清楚。了解这些因素的综合影响对于包括地中海森林在内的所有生态系统都至关重要，那里的干旱正在加剧。使用干旱处理（对照与干旱）和随后的恢复建立温室试验，因子结合四种养分处理（对照、添加氮 (N)、添加磷 (P) 以及添加 N 和 P）。N 以硝酸铵的形式以 50 kg N ha ^{-1 的}比例添加，P 以磷酸钙的形式以 25 kg P ha ^-1的比例添加. 总有机碳 (TOC) 的渗出量是从在地中海山地地区共存的两种重要树种中的每一种的 64 棵树苗的根部测量的，这些树种是樟子松（苏格兰松）和栎属植物（圣栎）。测量从树苗的单个根部释放的 TOC 量，以估计每克根部质量的根系分泌物。还监测叶绿素荧光 ( F _v / F _m ) 以检查处理对叶片性能的影响。叶绿素荧光不受任一物种的 SWC 或营养添加的影响，但根系分泌物受到影响，并且在两个物种之间有所不同。SWC 与干旱期 TOC 释放量呈正相关Q. ilex但对P. sylvestris没有影响。P的添加增加了冬青的根系分泌物。没有添加养分的两个物种在恢复期释放的 TOC 量与干旱期 SWC 呈弱负相关，这可能表明早期水分胁迫的延迟正效应。SWC 对两种物种都添加P时和P. sylvestris中添加 N 时从根部收集的 TOC 量产生积极影响。我们的结果表明，干旱对根系分泌物的影响可能因物种而异，并取决于土壤养分的可用性。