What determines the outcome of competition for organic nitrogen between plant roots and soil microbes?

大多数氮以蛋白质的形式进入土壤，在成为无机氮（铵;硝酸盐）之前需要土壤微生物进行相当大的修饰，这在历史上被认为是支持所有植物氮的需求。现在很清楚，植物根和土壤微生物激烈竞争根际早期蛋白质分解产物（短肽和氨基酸）的碳和氮。然而，尽管引起了激烈的辩论，并产生了许多高知名度的出版物，决定这一竞争结果的关键因素仍然是一个猜测的主题。因此，这仍然是我们对土壤中碳和氮循环的理解中的一个主要知识空白。许多人认为，植物-微生物竞争的结果是由单个植物物种对特定形式的氮的“偏好”控制的。其他人认为，结果是由土壤微生物竞争对手的效率/活性或其他因素，如无机氮的可用性或植物根部真菌共生体的存在。一些证据表明，在土壤氮矿化率低的生态系统中（例如高海拔或高纬度地区），植物比氮矿化率高的生态系统（例如农业生态系统）更成功地竞争有机形式的氮。同样，在某些调查中，根系感染真菌共生体对有机氮吸收的影响也很明显。然而，哪些生态系统特征驱动根际竞争的结果，哪些是巧合从来没有在一个协调庄园调查。

Most nitrogen enters the soil as protein, requiring considerable modification by soil microbes before becoming inorganic nitrogen (ammonium; nitrate), which was historically considered to support all plant nitrogen requirements. It is now clear that plant roots and soil microbes compete fiercely for the carbon and nitrogen of early protein breakdown products (short peptides and amino acids) in the rhizosphere. However, despite being hotly debated and generating many high profile publications, the key factors determining the outcome of this competition remain a subject of speculation. Consequently, this remains a major knowledge gap in our understanding of carbon and nitrogen cycling in soils.Many have suggested that the outcome of plant-microbe competition is controlled by the "preference" of individual plant species for particular forms of nitrogen. Others argue that the outcome is driven by the efficiency/activity of the soil microbial competitor or other factors such as the availability of inorganic nitrogen or the presence of fungal symbionts in plant roots. Some evidence suggests that in ecosystems where soil nitrogen mineralisation rates are low (e.g. those at high altitudes or latitudes), plants are more successful competitors for organic forms of nitrogen than in ecosystems where nitrogen mineralisation rates are high (e.g. agri-ecosystems). Similarly, an effect of root infection with a fungal symbiont on organic nitrogen acquisition is apparent in some investigations. However, which ecosystem characteristics drive the outcome of rhizosphere competition and which are coincidental has never been investigated in a coordinated manor.