柠条人工林细根不同分枝根序寿命估计

植物细根在发育结构上表现的形态特征和生理功能异质性影响细根寿命的准确估计,因此了解分枝根序细根寿命差异对于深入认识细根的周转过程和陆地生态系统碳分配具有重要意义。采用微根管(Minirhizotron)技术对晋西北黄土区的五年生柠条(Caragana Korshinskii Kom.)人工林细根的生长过程进行了为期3a(2007—2009年)的追踪观测,分析了不同因素(土层深度、季节变化、空间位置)对一级根和高级根寿命的影响。结果表明:(1)在各土层深度处,一级根的中值寿命均低于高级根中值寿命,其中一级根中值寿命表现随土层深度增加而增加趋势,而高级根除表层0—20 cm中值寿命较短外,各土层间变化趋势不明显,40—60 cm、80—100 cm土层高级根在观测期结束时其累积存活率仍在50%以上;(2)不同季节出生一级根和高级根的中值寿命季节性表现为:秋季夏季春季,并且在各个季节均表现,高级根寿命显著大于一级根寿命(P0.01);一级根仅夏季与秋季差异性不显著(P0.05),而高级根仅春季与秋季存在极显著差异(P0.01);(3)一级根和高级根距树干基部0 cm处细根中值寿命均大于50 cm处一级根和高级根细根的中值寿命。同一位置处高级根寿命要大于一级根寿命。在距树干基部0 cm处和50 cm处,一级根和高级根的寿命均存在极显著差异(P0.01),但高级根却在距树干基部0 cm和50 cm处差异不明显,而一级根却表现极显著差异(P0.01)。

Estimating fine root longevity among different branching order root for Caragana Korshinskii plantation using Minirhizotron

Fine roots are highly heterogeneous in term of morphological structure and physiological function, which influenced the estimating of fine root longevity. Therefore, investigating the difference of fine root longevity among different root orders is crucial for our knowledge about fine root turnover and carbon allocation in terrestrial ecosystems. In this study, we analyzed the impacts of different factors (soil depth, seasons of birth, and horizontal distance from the plant stems) on lifespan of first-order roots and higher-order roots in a five-year-old Caragana Korshinskii plantation using Minirhizotron from 2007 to 2009. The site located in the Northwest Shanxi, east of the loess plateau region of China. The Minirhizotron tubes were installed at two horizontal distances (0 cm, 50 cm) from plant stems within the 100 cm soil depth. Results showed that: (1) The median lifespan were lower for first order roots than for higher order roots in all soil depths. The first order roots increased with soil depth. Higher order roots did not significantly change with soil depths, except for the surface soil (0-20 cm). The cumulated survival rate was above 50% in both 40-60 cm and 80-100 cm soil depths at the end of observation. (2)For seasonal scale, the median lifespan of first and higher order roots showed: autumn > summer > spring. In all seasons, the lifespan of first order roots was significantly higher than that of higher order roots (P < 0.01). However, it showed discrepancy between first order roots and higher order roots with seasonal change. For first order roots, lifespan in spring was significantly different from summer and autumn. For higher order roots, the differences of lifespan were significant between spring and autumn (P < 0.01); (3) For horizontal distance from the plant stem, the median lifespan of first order roots and higher order roots were higher at 0 cm than at 50 cm from the plant stems. The lifespan of higher order roots were significantly longer than that of the first order roots at the horizontal distance 0 cm and 50 cm(P < 0.01). Whereas, the lifespan of them varied between 0 cm and 50 cm from the plant stems. At the two horizontal distance, the lifespan of first order roots were significantly different (P < 0.01), but that of higher order roots did not show significant differences.