Dirks Inga, Köhler Julia, Rachmilevitch Shimon, Meier Ina C
French Associates Institute for Agriculture and Biotechnology of Drylands, Ben Gurion University of the Negev, Beersheba, Israel.
Plant Ecology, Albrecht-von-Haller Institute for Plant Sciences, University of Göttingen, Göttingen, Germany.
Front Plant Sci. 2019 Apr 5;10:405. doi: 10.3389/fpls.2019.00405. eCollection 2019.
While a severe decrease in phosphorus (P) availability is already taking place in a large number of ecosystems, drought and nitrogen (N) deposition will likely further decrease the availability of P under global change. Plants have developed physiological strategies to cope with decreasing P resources, but it is unclear how these strategies respond to elevated N deposition and summer droughts. We investigated the influence of N and P availability and soil drought on P uptake (H PO feeding experiment) and use efficiencies in young Webb. trees. We hypothesized that (H1) the expected increases in soil N:P ratios will increase the efficiencies of P uptake and use of oak saplings but will decrease the efficiencies of N uptake and use, whereas (H2) drought will affect P uptake efficiency more than N uptake efficiency. In confirmation of (H1) we found that a sharp increase of the soil N:P ratio from 4 to 42 g g significantly increased the instantaneous P uptake efficiency (PUptakeE) by five-fold and long-term P uptake efficiency (PUptakeE) by six-fold, while it decreased N uptake efficiency (NUptakeE) and N use efficiency (NUE). In contradiction to (H1), P use efficiency (PUE) did not respond to the simulated extended gradient of soil N:P ratios but remained relatively constant. (H2) was only partially confirmed as soil drought reduced PUptakeE by up to a fourth at high soil N:P ratios but had no significant effect on NUptakeE. As a consequence, increasing summer droughts may decrease the response of PUptakeE to increasing P limitation, which - in the absence of adjustments of the efficiency of P use - can aggravate growth reductions in this eastern Mediterranean tree species under global change.
虽然大量生态系统中磷（P）的有效性已大幅下降，但在全球变化背景下，干旱和氮（N）沉降可能会进一步降低磷的有效性。植物已形成应对磷资源减少的生理策略，但尚不清楚这些策略如何响应氮沉降增加和夏季干旱。我们研究了氮磷有效性和土壤干旱对幼龄韦布树磷吸收（H₂PO₄ 饲喂实验）和利用效率的影响。我们假设：（H1）土壤氮磷比预期的增加将提高橡树幼苗磷吸收和利用效率，但会降低氮吸收和利用效率；而（H2）干旱对磷吸收效率的影响大于对氮吸收效率的影响。证实（H1）的是，我们发现土壤氮磷比从4克/克急剧增加到42克/克，瞬时磷吸收效率（PUptakeE）显著提高了五倍，长期磷吸收效率（PUptakeE）提高了六倍，而氮吸收效率（NUptakeE）和氮利用效率（NUE）降低。与（H1）相反，磷利用效率（PUE）对模拟的土壤氮磷比扩展梯度没有响应，而是保持相对恒定。（H2）仅部分得到证实，因为在高土壤氮磷比条件下，土壤干旱使PUptakeE降低了高达四分之一，但对NUptakeE没有显著影响。因此，夏季干旱加剧可能会降低PUptakeE对磷限制增加的响应，在缺乏磷利用效率调整的情况下，这可能会加剧全球变化下这种地中海东部树种的生长减少。
