英国利兹大学Sarah A. Batterman团队近期取得重要工作进展，他们研究发现了植食性动物限制共生固氮的机制。相关研究成果2022年12月7日在线发表于《自然》杂志上。
据介绍，最近的观察表明，成熟和恢复中森林的大量碳汇可能受到氮的强烈限制。与细菌共生的固氮树为热带森林提供了新氮的主要天然来源。然而，固氮树的丰度会受到严格的限制。新氮进入热带生态系统的限制性因素目前还不清楚。
研究人员调查了动物的植食性对限制热带森林共生固氮的影响，评估了固氮树是否比其他树经历了更多的植食性、植食性是否带来了巨大的碳成本以及植食性高是否是草食性动物针对固氮树富含氮叶子的结果。通过对1626片叶子（来自巴拿马43种热带树的350株幼苗）进行分析，研究人员发现：（1）尽管植食性动物降低了所有幼苗的生长和存活，但固氮树的植食性比非固氮树高26%；（2）由于植食性动物，固氮树的碳机会成本比非固氮树高34%，超过了固氮的代谢成本；（3）固氮树的高植食性不是由高叶氮驱动的。
总之，这些发现表明，植食性动物可能足以限制热带共生固氮，并可能限制其在缓解热带碳汇氮限制方面的作用。
附：英文原文
Title: Widespread herbivory cost in tropical nitrogen-fixing tree species
Author: Barker, Will, Comita, Liza S., Wright, S. Joseph, Phillips, Oliver L., Sedio, Brian E., Batterman, Sarah A.
Issue&Volume: 2022-12-07
Abstract: Recent observations suggest that the large carbon sink in mature and recovering forests may be strongly limited by nitrogen1,2,3. Nitrogen-fixing trees (fixers) in symbiosis with bacteria provide the main natural source of new nitrogen to tropical forests3,4. However, abundances of fixers are tightly constrained5,6,7, highlighting the fundamental unanswered question of what limits new nitrogen entering tropical ecosystems. Here we examine whether herbivory by animals is responsible for limiting symbiotic nitrogen fixation in tropical forests. We evaluate whether nitrogen-fixing trees experience more herbivory than other trees, whether herbivory carries a substantial carbon cost, and whether high herbivory is a result of herbivores targeting the nitrogen-rich leaves of fixers8,9. We analysed 1,626 leaves from 350 seedlings of 43 tropical tree species in Panama and found that: (1) although herbivory reduces the growth and survival of all seedlings, nitrogen-fixing trees undergo 26% more herbivory than non-fixers; (2) fixers have 34% higher carbon opportunity costs owing to herbivory than non-fixers, exceeding the metabolic cost of fixing nitrogen; and (3) the high herbivory of fixers is not driven by high leaf nitrogen. Our findings reveal that herbivory may be sufficient to limit tropical symbiotic nitrogen fixation and could constrain its role in alleviating nitrogen limitation on the tropical carbon sink.
DOI: 10.1038/s41586-022-05502-6
Source: https://www.nature.com/articles/s41586-022-05502-6
Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
投稿链接：http://www.nature.com/authors/submit_manuscript.html
本期文章：《自然》：Online/在线发表
