State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
PLoS One. 2010 Aug 12;5(8):e12125. doi: 10.1371/journal.pone.0012125.
Root lifespan is an important trait that determines plants' ability to acquire and conserve soil resources. There have been several studies investigating characteristics of root lifespan of both woody and herbaceous species. However, most of the studies have focused on non-clonal plants, and there have been little data on root lifespan for clonal plants that occur widely in temperate grasslands.
METHODOLOGY/PRINCIPAL FINDINGS: We investigated the effects of rhizome severing on overall root lifespan of Leymus chinensis, a clonal, dominant grass species in the temperate steppe in northern China, in a 2-year field study using modified rhizotron technique. More specifically, we investigated the effects of rhizome severing on root lifespan of roots born in different seasons and distributed at different soil depths. Rhizome severing led to an increase in the overall root lifespan from 81 to 103 days. The increase in root lifespan exhibited spatial and temporal characteristics such that it increased lifespan for roots distributed in the top two soil layers and for roots born in summer and spring, but it had no effect on lifespan of roots in the deep soil layer and born in autumn. We also examined the effect of rhizome severing on carbohydrate and N contents in roots, and found that root carbohydrate and N contents were not affected by rhizome severing. Further, we found that root lifespan of Stipa krylovii and Artemisia frigida, two dominant, non-clonal species in the temperate steppe, was significantly longer (118 d) than that of L. chinensis (81 d), and this value became comparable to that of L. chinensis under rhizome severing (103 d).
CONCLUSIONS/SIGNIFICANCE: We found that root lifespan in dominant, clonal L. chinensis was shorter than for the dominant, non-clonal species of S. krylovii and A. frigida. There was a substantial increase in the root lifespan of L. chinensis in response to severing their rhizomes, and this increase in root lifespan exhibited temporal and spatial characteristics. These findings suggest that the presence of rhizomes is likely to account for the observed short lifespan of clonal plant species in the temperate steppe.
根寿命是决定植物获取和保存土壤资源能力的一个重要特征。已经有几项研究调查了木本和草本物种的根寿命特征。然而，大多数研究都集中在非克隆植物上，而对于广泛存在于温带草原的克隆植物的根寿命数据则很少。
方法/主要发现：我们使用改良的根管技术，在一项为期两年的野外研究中，调查了根茎切断对中国北方温带草原优势克隆草种赖草（Leymus chinensis）整体根寿命的影响。更具体地说，我们调查了根茎切断对不同季节出生和分布在不同土壤深度的根的根寿命的影响。根茎切断导致根寿命从 81 天增加到 103 天。根寿命的增加具有时空特征，即增加了分布在最上面两个土壤层和夏季和春季出生的根的寿命，但对分布在深层土壤和秋季出生的根的寿命没有影响。我们还检查了根茎切断对根碳水化合物和 N 含量的影响，发现根碳水化合物和 N 含量不受根茎切断的影响。此外，我们发现，温带草原的两种优势非克隆物种赖草（Leymus chinensis）和冷蒿（Artemisia frigida）的根寿命明显长于赖草（118 天），而在根茎切断后，其根寿命与赖草相当（103 天）。
结论/意义：我们发现，优势克隆种赖草的根寿命短于优势非克隆种赖草和冷蒿。根茎切断后，赖草的根寿命显著增加，且这种根寿命的增加具有时空特征。这些发现表明，根茎的存在可能是温带草原观察到克隆植物物种寿命较短的原因。
