Lihui Ma, Xiaoli Liu, Jie Chai, Youke Wang, Jingui Yang
Institute of Water Saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, China.
Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China.
Front Plant Sci. 2021 Oct 19;12:684468. doi: 10.3389/fpls.2021.684468. eCollection 2021.
The vertical root distribution and rooting depth are the main belowground plant functional traits used to indicate drought resistance in arid and semiarid regions. The effects of the slope aspect on the aboveground traits are visible but not the belowground deep root traits. We aimed to investigate the fine root traits of the locust tree ( L.) planted on southerly and northerly aspects, and the variations in the rooting depth in regions with different rainfall, as well as assessing how deep rooting, might affect the response to drought in a loess region. We selected three study sites with different rainfall amounts, with six sampling plots at each site (three each with southerly and northerly aspects). Soil core samples were collected down to the depth where no roots were present. The locust trees tended to develop deeper fine roots rather than greater heights. The tree height and diameter were greater for locust trees on northerly aspects, whereas trees on southerly aspects had significantly deeper rooting depths. Fine root traits (root length, root area, and root dry weight density) were higher in the southerly aspect for both Changwu and Ansai, but lower in Suide. The ratio of the root front depth tree height ranged from 1.04 to 3.17, which was higher on southerly than northerly aspects, and it increased as the rainfall decreased. Locust tree growth traits (belowground fine root and aboveground tree height) were positively correlated with the mean annual rainfall. The soil moisture content of the topsoil decreased as the rainfall decreased, but the pattern varied in the deep layer. Our results suggest that the variations in the belowground rooting depth under different slope aspects may be related to plant survival strategies. The vertical extension of the rooting depth and tree height may be key functional traits that determine plant growth in drought-prone regions.
垂直根系分布和生根深度是用于指示干旱和半干旱地区抗旱性的主要地下植物功能性状。坡面朝向对地上性状的影响明显，但对地下深层根系性状的影响不明显。我们旨在研究种植在南坡和北坡的刺槐的细根性状，以及不同降雨区域生根深度的变化，并评估深根如何影响黄土地区对干旱的响应。我们选择了三个降雨量不同的研究地点，每个地点有六个采样区（南坡和北坡各三个）。采集土壤岩心样本至无根系的深度。刺槐倾向于形成更深的细根而不是更高的树高。北坡刺槐的树高和直径更大，而南坡的树生根深度明显更深。长武和安塞的细根性状（根长、根面积和根干重密度）在南坡较高，但在绥德较低。根前深度与树高的比值在1.04至3.17之间，南坡高于北坡，且随降雨量减少而增加。刺槐生长性状（地下细根和地上树高）与年平均降雨量呈正相关。表层土壤水分含量随降雨量减少而降低，但深层变化模式不同。我们的结果表明，不同坡面下地下生根深度的变化可能与植物生存策略有关。生根深度和树高的垂直延伸可能是决定干旱易发地区植物生长的关键功能性状。
