Ndzwanana Zimbini, Tsvuura Zivanai, Valentine Alex J, Pérez-Fernández María A, Magadlela Anathi
School of Life Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa.
Botany and Zoology Department, University of Stellenbosch, Matieland, Stellenbosch, South Africa.
AoB Plants. 2019 Feb 27;11(3):plz008. doi: 10.1093/aobpla/plz008. eCollection 2019 Jun.
fixes atmospheric nitrogen (N) and distributes it back into ecosystems. We hypothesize that biological nitrogen fixation in this plant species is limited by competition from the invasive shrub, . Competition would therefore result in the legume plant switching its limited nitrogen (N) sources in phosphorus-poor soils in savannah ecosystems when resources have to be shared. This study investigated the different patterns of N use and growth costs by a native and an introduced leguminous shrubby species. We propose that the two species sharing the same environment might result in competition. The competitive effect would induce in the indigenous legume to better utilize atmospheric-derived N modifying plant growth kinetics and plant mineral concentrations. Seedlings of were cultivated in natural soil inoculum with low levels of phosphorus (mg L ± SE) of 3.67 ± 0.88. The experiments were divided into two treatments where (i) seedlings of were subjected to competition by cultivating them together with seedlings of , and (ii) seedlings of were cultivated independently. Although was subjected to competition, the N-fixing bacteria that occupied the nodules was species, similar to plants not subjected to competition. Total plant biomass was similar between treatments although plants subjected to competition accumulated more below-ground biomass and showed higher carbon construction costs than plants growing individually. Total plant phosphorus and nitrogen decreased in seedlings of under competition, whereas no differences were observed in percent N derived from the atmosphere (%NDFA) between treatments. The specific nitrogen utilization rate (SNUR) was higher in plants subjected to competition while specific nitrogen absorption rate (SNAR) showed the opposite response. is highly adapted to nutrient-poor savannah ecosystems and can withstand competition from invasive shrubs by utilizing both atmospheric and soil nitrogen sources.
固定大气中的氮（N）并将其重新分配到生态系统中。我们假设这种植物物种中的生物固氮受到入侵灌木竞争的限制。因此，在稀树草原生态系统中，当资源必须共享时，竞争会导致豆科植物在缺磷土壤中切换其有限的氮源。本研究调查了本地和引入的豆科灌木物种不同的氮利用模式和生长成本。我们提出，共享相同环境的这两个物种可能会导致竞争。竞争效应会促使本土豆科植物更好地利用大气来源的氮，从而改变植物生长动力学和植物矿物质浓度。将[植物名称]的幼苗种植在低磷（毫克/升±标准误差）为3.67±0.88的天然土壤接种物中。实验分为两个处理组，（i）将[植物名称]的幼苗与[另一植物名称]的幼苗一起培养，使其受到竞争，（ii）将[植物名称]的幼苗单独培养。尽管[植物名称]受到了竞争，但占据根瘤的固氮细菌是[细菌物种名称]，与未受到竞争的植物相似。各处理组之间的总植物生物量相似，尽管受到竞争的[植物名称]植物积累了更多的地下生物量，并且与单独生长的植物相比，表现出更高的碳构建成本。在竞争条件下，[植物名称]幼苗中的总植物磷和氮含量下降，而各处理组之间来自大气的氮百分比（%NDFA）没有差异。受到竞争的[植物名称]植物的比氮利用率（SNUR）较高，而比氮吸收速率（SNAR）则表现出相反的反应。[植物名称]高度适应营养贫瘠的稀树草原生态系统，并且可以通过利用大气和土壤氮源来抵御来自入侵灌木的竞争。
