Previous studies of the N:P ratio in wetland plants have been carried out in northern hemisphere wetlands where atmospheric nitrogen deposition is higher. There is little research on foliar N:P ratio as a potential indicator of nutrient limitation in vegetation communities in southern hemisphere wetlands. This study aimed to redress this knowledge gap and answer the following questions: how well does the plant tissue nitrogen to phosphorus (N:P) ratio predict wetland plant community nutrient limitation, as indicated by vegetation standing stocks and below‐ground biomass, in southern hemisphere fens? Secondly, what are the impacts of realistic upper levels of farm nutrient run‐off on natural montane fen vegetation? Low (35 kg ha⁻¹ year⁻¹) and high (70 kg ha⁻¹ year⁻¹) levels of nitrate‐N or ammonium‐N with and without P (20 kg ha⁻¹ year⁻¹) were added to 81 vegetation plots over a period of 2.75 years. Species composition, plant nutrient status, and above‐ground live vegetation standing stocks were assessed after 3 years, and below‐ground biomass after 2 years. Plant tissue analysis suggested the community was N limited or N and P co‐limited; we found greater standing stocks of vegetation in plots treated with 70 kg ha⁻¹ year⁻¹ ammonium‐N, indicating N limitation. No difference between other treatments was found in above‐ground standing stocks or below‐ground biomass. Plant species cover increased in both high N treatments, consistent with N limitation. These changes in plant species cover were accompanied by significant decreases in species richness in both high N treatments. Native species dominated the vegetation and this was unaffected by nutrient addition (90% cover). This is one of the first studies to test and find support for the N:P ratio in southern hemisphere wetlands. Observed declines in species richness after N fertilisation in an N‐limited fen suggests increased N may pose risks to austral wetlands. Responses by plant communities (changes in composition, biomass) to lower levels of nutrient addition may require longer periods of fertilisation to be apparent in slow growing ecosystems.

中文翻译：

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南方沼泽植物对养分添加的反应和植被氮磷比的预测能力

先前对湿地植物中氮磷比的研究是在大气氮沉降较高的北半球湿地中进行的。关于叶面氮磷比作为南半球湿地植被群落养分限制的潜在指标的研究很少。本研究旨在弥补这一知识差距并回答以下问题：植物组织氮磷 (N:P) 比如何预测湿地植物群落养分限制，如植被常备蓄积量和地下生物量所示，在南部半球巢穴？第二，农场养分流失的现实上限对天然山地沼泽植被有何影响？将低（35 公斤公顷⁻¹ 年⁻¹）和高（70 公斤公顷⁻¹ 年⁻¹）硝酸盐-N 或铵-N（含磷和不含磷）（20 公斤公顷⁻¹ 年⁻¹）添加到 81 2.75 年的植被地块。3 年后评估物种组成、植物养分状况和地上活植被存量，2 年后评估地下生物量。植物组织分析表明，该群落受 N 限制或 N 和 P 共同限制；我们发现在用 70 kg ha⁻¹ 年⁻¹ 铵-N 处理的地块中，植物的常备存量更大，表明 N 限制。在地上常备种群或地下生物量中没有发现其他处理之间的差异。两种高氮处理的植物物种覆盖率均增加，与氮限制一致。在两种高氮处理中，植物物种覆盖率的这些变化都伴随着物种丰富度的显着下降。本地物种占主导地位，这不受营养添加（90% 覆盖）的影响。这是对南半球湿地 N:P 比进行测试并找到支持的首批研究之一。观察到在限氮沼泽中施氮后物种丰富度下降表明，增加氮可能对南方湿地构成风险。在缓慢生长的生态系统中，植物群落（组成、生物量的变化）对较低水平的养分添加的反应可能需要更长时间的施肥才能明显。本地物种占主导地位，这不受营养添加（90% 覆盖）的影响。这是对南半球湿地 N:P 比率进行测试和寻找支持的首批研究之一。观察到在限氮沼泽中施氮后物种丰富度下降表明，增加氮可能对南方湿地构成风险。在缓慢生长的生态系统中，植物群落（组成、生物量的变化）对较低水平的养分添加的反应可能需要更长时间的施肥才能明显。本地物种占主导地位，这不受营养添加（90% 覆盖）的影响。这是对南半球湿地 N:P 比进行测试并找到支持的首批研究之一。观察到在限氮沼泽中施氮后物种丰富度下降表明，增加氮可能对南方湿地构成风险。在缓慢生长的生态系统中，植物群落（组成、生物量的变化）对较低水平的养分添加的反应可能需要更长时间的施肥才能明显。