Abstract：
Phosphorus (P) availability to forest trees is often limited by local soil conditions that increase its fixation to soil minerals. In certain regions, atmospheric-P inputs can compensate for low soil-P availability. Among atmospheric-P sources, desert dust is the most dominant. However, the effects of desert dust on P nutrition and its uptake mechanisms by forest trees are currently unknown. We hypothesized that forest trees that naturally grow on P-poor soils or soils with high soil-P fixation capacity can acquire P from desert dust deposited on their leaves via direct foliar uptake, bypassing the soil, thus promoting tree growth and productivity. We performed a controlled greenhouse experiment with three forest tree species: Palestine Oak (Quercus calliprinos) and Carob (Ceratonia siliqua), native to the NE edge of the Saharan desert, and Brazilian peppertree (Schinus terebinthifolius), native to the Atlantic Forest in Brazil, which is located on the western part of the trans-Atlantic Saharan dust route. To simulate natural dust deposition events, the trees had desert dust applied directly upon their foliage and were monitored for growth and final biomass, P levels, leaf surface pH and the rate of photosynthesis. The dust treatment increased the P concentration significantly by 33-37% in Ceratonia and Schinus trees. On the other hand, trees that received the dust displayed a 17-58% reduction in biomass, probably related to particle coverage of the leaf surface that inhibited photosynthesis by 17-30%. Overall, our findings show that direct P uptake from desert dust can be an alternative P uptake pathway for multiple tree species under P-deficient conditions, with implications for forest trees\' P economy.
摘要：
森林树木的磷（P）可用性通常受到当地土壤条件的限制，这增加了其对土壤矿物质的固定。在某些地区,大气磷的输入可以弥补土壤磷有效性的不足。在大气P源中，沙漠尘埃是最主要的。然而,目前尚不清楚沙漠粉尘对P营养的影响及其被林木吸收的机制。我们假设在贫磷土壤或具有高土壤-磷固定能力的土壤上自然生长的林木可以通过直接叶面吸收从沉积在其叶子上的沙漠灰尘中获取磷，绕过土壤，从而促进树木的生长和生产力。我们对三种森林树种进行了受控温室实验：巴勒斯坦橡树（Quercuscalliprinos）和角豆树（Ceratoniasiliqua），原产于撒哈拉沙漠的东北部边缘，和巴西胡椒树（Tchinusterterbinthifolus），原产于巴西的大西洋森林，位于跨大西洋撒哈拉尘埃路线的西部。为了模拟自然尘埃沉积事件，这些树木直接在其叶子上施加了沙漠灰尘，并对其生长和最终生物量进行了监测，P级,叶片表面pH和光合作用速率。粉尘处理使Ceratonia和Schinus树的P浓度显着增加了33-37％。另一方面,接收到灰尘的树木显示生物量减少了17-58%，可能与叶片表面的颗粒覆盖率有关，后者抑制了17-30％的光合作用。总的来说,我们的发现表明，在缺磷条件下，沙漠灰尘中的直接磷吸收可能是多种树种的替代磷吸收途径，对林木经济有影响。
