Tree symbioses sustain nitrogen fixation despite excess nitrogen supply
Tree symbioses sustain nitrogen fixation despite excess nitrogen supply
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尽管氮供应过剩，树木共生仍维持固氮作用
DOI：
10.1002/ecm.1562
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发表时间：
2023
影响因子：
6.1
通讯作者：
Kou‐Giesbrecht, Sian
中科院分区：
文献类型：
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作者：
Menge, Duncan N. L.;Wolf, Amelia A.;Funk, Jennifer L.;Perakis, Steven S.;Akana, Palani R.;Arkebauer, Rachel;Bytnerowicz, Thomas A.;Carreras Pereira, K. A.;Huddell, Alexandra M.;Kou‐Giesbrecht, Sian
共生固氮（SNF）是一个关键的生态过程，其影响取决于SNF调节策略，即SNF速率在何种程度上响应于氮素与其他资源的限制。SNF是专性的或表现出不完全的下调可以导致过量的固氮，而兼性SNF策略则不会。我们假设基于树木的SNF策略因纬度（热带与温带）和共生类型（放线菌与根瘤菌）而异。具体来说，我们预计热带根瘤菌共生体显示出强烈的兼性SNF作为其在低纬度森林中成功的解释。在这项研究中，我们在纽约，俄勒冈州和夏威夷使用15 N同位素稀释田间实验，以确定SNF策略在六个固氮树共生体。氮肥+10和+15 g N m− 2 year − 1 4-5年缓解了所有类群的氮限制，为确定SNF策略铺平了道路。与我们的假设相反，我们研究的所有六种共生体即使在高N.刺槐（温带根瘤菌）固定91%的N（%Ndfa）在对照组中，而在+10和+15 g N m− 2年− 1处理中分别为64%和59%。红桤木（温带放线菌）的% Ndfa分别为95%、70%和60%。对于热带物种，% Ndfa分别为86%，80%和82%，Gliricidia sepium（根瘤菌）; 79%，69%和67%，木麻黄（放线菌）; 91%，42%和67%，相思（根瘤菌）;和60%，51%和19%，Morella faya（放线菌）。施磷不刺激树木生长或SNF。这些结果表明，固氮树的纬度丰度分布不是由SNF策略的转变引起的。它们还有助于解释在许多森林中过量的N，其中N固定剂是常见的。
Symbiotic nitrogen fixation (SNF) is a key ecological process whose impact depends on the strategy of SNF regulation—the degree to which rates of SNF change in response to limitation by N versus other resources. SNF that is obligate or exhibits incomplete downregulation can result in excess N fixation, whereas a facultative SNF strategy does not. We hypothesized that tree‐based SNF strategies differed by latitude (tropical vs. temperate) and symbiotic type (actinorhizal vs. rhizobial). Specifically, we expected tropical rhizobial symbioses to display strongly facultative SNF as an explanation of their success in low‐latitude forests. In this study we used15N isotope dilution field experiments in New York, Oregon, and Hawaii to determine SNF strategies in six N‐fixing tree symbioses. Nitrogen fertilization with +10 and +15 g N m−2year−1for 4–5 years alleviated N limitation in all taxa, paving the way to determine SNF strategies. Contrary to our hypothesis, all six of the symbioses we studied sustained SNF even at high N.Robinia pseudoacacia(temperate rhizobial) fixed 91% of its N (%Ndfa) in controls, compared to 64% and 59% in the +10 and +15 g N m−2year−1treatments. ForAlnus rubra(temperate actinorhizal), %Ndfawas 95%, 70%, and 60%. For the tropical species, %Ndfawas 86%, 80%, and 82% forGliricidia sepium(rhizobial); 79%, 69%, and 67% forCasuarina equisetifolia(actinorhizal); 91%, 42%, and 67% forAcacia koa(rhizobial); and 60%, 51%, and 19% forMorella faya(actinorhizal). Fertilization with phosphorus did not stimulate tree growth or SNF. These results suggest that the latitudinal abundance distribution of N‐fixing trees is not caused by a shift in SNF strategy. They also help explain the excess N in many forests where N fixers are common.