Grass species grown in South American natural grasslands present different growth strategies related to variations in specific leaf area (SLA), leaf dry matter content (LDMC) and possible nitrogen (N) allocation. Nitrogen fertilisation can have effects on physiological processes such as CO₂ assimilation; however, these responses can change depending on the growth strategy adopted by each species. The aim of the present study is to determine the effects of N fertilisation on SLA, LDMC and CO₂ assimilation in eight C₄ grass species: Axonopus affinis, Paspalum pumilum, P. notatum, P. urvillei, P. plicatulum, Andropogon lateralis, Saccharum angustifolium and Aristida laevis. These species were cultivated in pots filled with soil subjected to two conditions of N availability: nil (control) and 200 mg N kg^–1 soil. The SLA of Axonopus affinis was 5.4 times higher than that of Aristida laevis. Axonopus affinis and P. pumilum recorded the lowest LDMC, their leaves showed 53% lower LDMC than observed for Aristida laevis, on average. Resource-capture species showed variation in leaf area with N addition to values 20% higher than the control, whereas species characterised by a resource-conservation growth strategy recorded variation in leaf area with N addition to values only 8% higher than the control. With N addition, the CO₂ assimilation of resource-capture species represented variation (increase) nine times that of resource-conservation species compared with their respective controls. Resource-capture species have greater CO₂ capture potential than resource-conservation species, mainly a result of N addition.

南美天然草原上生长的草种表现出不同的生长策略，这些变化与比叶面积（SLA），叶干物质含量（LDMC）和可能的氮（N）分配有关。氮肥可对生理过程产生影响，例如CO ₂同化；但是，这些响应可能会根据每个物种采用的生长策略而改变。本研究的目的是为了确定N个施肥对SLA，LDMC和CO的影响₂同化在8个C ₄草种：地毯草AFFINIS，雀稗细叶，百喜草，P. urvillei，P. plicatulum，雄侧柏，蔗糖和阿里斯提达。这些物种在充满氮的两个条件下的盆中种植：零（对照）和200 mg N kg ^-1的土壤。Axonopus affinis的SLA是Aristida laevis的5.4倍。Axonopus affinis和P. pumilum的LDMC最低，其叶片的LDMC比Aristida laevis的低53％。， 一般。资源捕获物种显示叶面积变化，其氮含量比对照高20％，而以资源保护生长策略为特征的物种记录叶面积变化，氮含量仅比对照高8％。添加N后，资源捕获物种的CO ₂同化量比资源保护物种的变化（增加）是其各自的对照的九倍。资源捕获物种比资源保护物种具有更大的CO ₂捕获潜力，这主要是由于氮的添加。