Long-term nitrogen addition leads to loss of species richness due to litter accumulation and soil acidification in a temperate steppe.
Long-term nitrogen addition leads to loss of species richness due to litter accumulation and soil acidification in a temperate steppe.
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DOI：
10.1371/journal.pone.0047369
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Li L
中科院分区：
文献类型：
--
作者：
Fang Y;Xun F;Bai W;Zhang W;Li L
虽然已知群落结构和物种丰富度对氮肥施用有显著的响应，但对特定物种替代和丰富度损失的机制知之甚少。在中国半干旱温带草原上，通过5个处理的人工施氮试验，研究了施氮对草原群落结构和物种丰富度的影响。随机选取样方调查各样地群落的物种丰富度和生物量。测定了根际土壤中的根素、速效磷、全磷、土壤含水量、pH、速效磷、全磷和无机氮含量。采用二元相关和逐步多元线性回归分析了物种丰富度与测量因子之间的关系。两个优势种，灌木冷蒿和草针茅，响应不同的N添加，使前者逐渐被后者所取代。S. krylovii和A. frigida分别具有高度分枝的纤维状主根系统和不分枝的主根系统。S. krylovii的株高高于A.在对照区和施氮区均表现为冷性。这些差异可能有助于观察到的物种替换。此外，对根际土壤中根元素和AP含量的分析表明，两种植物不同的钙吸收策略和磷、钠反应可能是导致这种替代的原因。物种丰富度沿着5个氮添加水平显著降低。结果表明，物种丰富度与土壤pH值、凋落物量、土壤含水量、AP浓度和无机N浓度存在显著相关关系。结果表明，凋落物积累和土壤酸化分别解释了物种丰富度变异的52.3%和43.3%。这些结果将有助于我们进一步了解氮沉降情景下中国北方半干旱温带草原物种丰富度的变化。
Although community structure and species richness are known to respond to nitrogen fertilization dramatically, little is known about the mechanisms underlying specific species replacement and richness loss. In an experiment in semiarid temperate steppe of China, manipulative N addition with five treatments was conducted to evaluate the effect of N addition on the community structure and species richness. Species richness and biomass of community in each plot were investigated in a randomly selected quadrat. Root element, available and total phosphorus (AP, TP) in rhizospheric soil, and soil moisture, pH, AP, TP and inorganic N in the soil were measured. The relationship between species richness and the measured factors was analyzed using bivariate correlations and stepwise multiple linear regressions. The two dominant species, a shrub Artemisia frigida and a grass Stipa krylovii, responded differently to N addition such that the former was gradually replaced by the latter. S. krylovii and A. frigida had highly-branched fibrous and un-branched tap root systems, respectively. S. krylovii had higher height than A. frigida in both control and N added plots. These differences may contribute to the observed species replacement. In addition, the analysis on root element and AP contents in rhizospheric soil suggests that different calcium acquisition strategies, and phosphorus and sodium responses of the two species may account for the replacement. Species richness was significantly reduced along the five N addition levels. Our results revealed a significant relationship between species richness and soil pH, litter amount, soil moisture, AP concentration and inorganic N concentration. Our results indicate that litter accumulation and soil acidification accounted for 52.3% and 43.3% of the variation in species richness, respectively. These findings would advance our knowledge on the changes in species richness in semiarid temperate steppe of northern China under N deposition scenario.
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