Zi Er-Die Ba He-Ti, Jia Guo-Dong, Yu Xin-Xiao, Shi Jia-Mei, Jiang Tao
Key Laboratory of State Forestry and Grassland Administration on Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China.
Ying Yong Sheng Tai Xue Bao. 2020 Jun;31(6):1807-1816. doi: 10.13287/j.1001-9332.202006.023.
Water availability is the key factor limiting plant growth in arid regions. Populus simonii is a typical shelterbelt tree species in Zhangbei County, Hebei Province, with an important role in constructing ecological barrier. With stable isotope technique, graphical method, and multiple linear mixing model, we analyzed water sources and water use strategies of P. simonii in different growth periods with four different degrees of degradation (non-degraded, slightly degraded, modera-tely degraded and severely degraded) in Zhangbei County. Results would help improve our understanding on the cause and mechanism of the large-scale degradation of P. simonii in this area. The results showed that water sources of P. simonii in the early growth stage (May-June) from all four degradation degrees were relatively simple. P. simonii mainly used soil water in 0-40 cm, with the utilization rates being 34.2%, 50.1%, 41.6%, and 55.7% for the four degradation degrees, respectively. At the middle growth stage (July-August), non-degraded P. simonii utilized soil water from layers of 200-280 cm and 280-400 cm, with utilization rates of 20.2% and 30.9%, respectively. Soil water at 200-280 cm and 280-400 cm layers was utilized by slightly degraded poplar, with the contribution rates of each layer being 33.2% and 27.9%, respectively. Moderately degraded P. simonii utilized soil water from the depths of 0-40 cm and 40-120 cm, with the rates of 30% and 26.9%, respectively. Water utilization rate of severely degraded P. simonii to 0-40 cm depth was 55.4%. At the late growth stage (September-October), water sources of non-degraded P. simonii transferred to the upper-middle soil layers, with the utilization rate of 0-40 cm, 40-80 cm, and 80-120 cm being 23.3%, 17.2%, and 16.5%, respectively. The utilization rate of the slightly degraded P. simonii was 35.7% at 0-40 cm and 20.6% at 80-200 cm. The moderately and severely degraded P. simonii mainly utilized soil water at 0-40 cm layer, with the contribution rates of soil water being 43.7% and 51.8%, respectively. With the exacerbation of degradation, the main water source of P. simonii gradually transferred from deep to surface soil water.
水分可利用性是干旱地区限制植物生长的关键因素。小叶杨是河北省张北县典型的防护林树种，在构建生态屏障方面发挥着重要作用。利用稳定同位素技术、图解法和多元线性混合模型，我们分析了张北县四个不同退化程度（未退化、轻度退化、中度退化和重度退化）的小叶杨在不同生长时期的水源和水分利用策略。研究结果将有助于增进我们对该地区小叶杨大规模退化原因及机制的理解。结果表明，四个退化程度的小叶杨在生长初期（5 - 6月）的水源相对单一。小叶杨主要利用0 - 40厘米土层的土壤水，四个退化程度的利用率分别为34.2%、50.1%、41.6%和55.7%。在生长中期（7 - 8月），未退化的小叶杨利用200 - 280厘米和280 - 400厘米土层的土壤水，利用率分别为20.2%和30.9%。轻度退化的杨树利用200 - 280厘米和280 - 400厘米土层的土壤水，各层贡献率分别为33.2%和27.9%。中度退化的小叶杨利用0 - 40厘米和40 - 120厘米深度的土壤水，利用率分别为30%和26.9%。重度退化的小叶杨对0 - 40厘米深度土壤水的利用率为55.4%。在生长后期（9 - 10月），未退化的小叶杨水源转移到土壤中上层，0 - 40厘米、40 - 80厘米和80 - 120厘米的利用率分别为23.3%、17.2%和16.5%。轻度退化的小叶杨在0 - 40厘米的利用率为35.7%，在80 - 200厘米的利用率为20.6%。中度和重度退化的小叶杨主要利用0 - 40厘米土层的土壤水，土壤水贡献率分别为43.7%和51.8%。随着退化加剧，小叶杨的主要水源逐渐从深层土壤水转移到表层土壤水。
