植物生态学报 ›› 2022, Vol. 46 ›› Issue (5): 569-579.DOI: 10.17521/cjpe.2021.0419

所属专题: 青藏高原植物生态学:种群生态学

• 研究论文 • 上一篇    下一篇

祁连山区演替先锋物种西藏沙棘的种群结构及动态对海拔梯度的响应

卢晶, 马宗祺, 高鹏斐, 樊宝丽, 孙坤()   

  1. 西北师范大学生命科学学院, 兰州 730070
  • 收稿日期:2021-11-18 接受日期:2022-03-23 出版日期:2022-05-20 发布日期:2022-06-09
  • 通讯作者: 孙坤
  • 作者简介:* (kunsun@nwnu.edu.cn) ORCID:卢晶: 0000-0002-0319-4491
  • 基金资助:
    国家自然科学基金(31660060);甘肃省重点研发计划(21YF5NA069)

Changes in the Hippophae tibetana population structure and dynamics, a pioneer species of succession, to altitudinal gradients in the Qilian Mountains, China

LU Jing, MA Zong-Qi, GAO Peng-Fei, FAN Bao-Li, SUN Kun()   

  1. College of Life Science, Northwest Normal University, Lanzhou 730070, China
  • Received:2021-11-18 Accepted:2022-03-23 Online:2022-05-20 Published:2022-06-09
  • Contact: SUN Kun
  • Supported by:
    National Natural Science Foundation of China(31660060);Gansu Province Key Research and Development Plan(21YF5NA069)

摘要:

西藏沙棘(Hippophae tibetana)是青藏高原高寒区特有的低矮灌木和植被演替先锋物种, 具有优良的水土保持功效, 对高海拔环境表现出良好的生态适应性, 但有关其种群结构及动态对海拔梯度的响应规律少有研究, 阻碍了对西藏沙棘适应高寒生境生态策略的理解。青藏高原东北缘的祁连山区生态脆弱, 乡土物种西藏沙棘常在海拔2 700-3 300 m的高寒退化草地呈斑块状分布, 对该区水源涵养林的维持具有重要作用。该研究以祁连山区3个海拔(2 868、3 012、3 244 m)的西藏沙棘为研究对象, 通过编制静态生命表及绘制存活曲线, 分析西藏沙棘的种群结构特征和种群动态, 并利用种群动态量化分析和时间序列模型定量研究其未来发展趋势。结果显示: 1)西藏沙棘种群的基径、株高和冠幅均随海拔的升高而降低; 3个海拔种群均呈中龄期个体丰富, 老幼龄期个体较少的纺锤型年龄结构, 充足的中龄期个体可以维持种群短期稳定。2)种群存活曲线均为Deevey-II型, 存活能力为低海拔>中海拔>高海拔; 死亡率和消失率均较高, 呈高海拔>低海拔>中海拔的趋势, 3个海拔种群均缺乏幼苗, 未来均将走向衰退, 高海拔种群较其他海拔提前进入衰退期; 各海拔老龄期生命期望值为中海拔>低海拔>高海拔。3)各海拔种群动态指数(Vpi)均趋于0, 表明各种群均趋于稳定, 中海拔种群受随机干扰风险概率的极大值(Pmax)最小, 表明受随机干扰时中海拔种群最稳定, 中海拔更适宜西藏沙棘的生存。4)未来2、4、6个龄级时间后, 3个海拔的中、老龄期苗木增多, 小龄期苗木数目减少, 且各海拔种群均面临幼苗补充不及时的风险, 各种群将由稳定向衰退发展, 幼苗的缺少, 种内、种间竞争及环境胁迫是造成种群走向衰退的重要原因。

关键词: 青藏高原, 西藏沙棘, 年龄结构, 种群动态, 海拔梯度

Abstract:

Aims The variations in population structure and the quantitative dynamics of plants are a reflection of the local ecology and environment. Hippophae tibetana is a dwarf shrub, and a pioneer species of vegetation succession which is peculiar to the alpine region of the Qingzang Plateau. It has excellent water and soil conservation effects and good ecological adaptability to high-altitude environments. However, little research has been made into the changes in the population structure and dynamics at different altitudes. Such an understanding is important to understanding the ecological strategy of H. tibetana adaptation to alpine habitats. The Qilian Mountains in the northeastern margin of the Qingzang Plateau contain degraded alpine grassland and are ecologically fragile. It is thought that the irregularly distributed native species, H. tibetana, plays an important role in water conservation at 2 700-3 300 m in this region.

Methods The structure, dynamics, life span and morphological characteristics of H. tibetana populations distributed at three altitudes (2 868, 3 012, and 3 244 m) in Tianzhu Zangzu Autonomous County, Qilian Mountains were studied and quantified, establishing static life tables and population survival curves. This quantitative analysis of the population dynamics was used to try to determine future population development trends.

Important findings We found: 1) The plant height, basal diameter and crown width of H. tibetana decreased with elevation. The age structures of all populations at the three altitudes were roughly spindle-shaped, with abundant mature individuals but few seedlings and few old plants. Populations were found to be stable. 2) The survival curves of all populations tended to approach the Deevey-II type, and the survivability was greatest at low altitude, medium at middle altitude, and lowest at high-altitude. The mortality and disappearance rates were both high, ranking from highest to lowest with high-altitude > low-altitude > middle-altitude. Seedlings were proportionally more abundant at the middle and high altitudes. Life expectancy was greatest at middle-altitude > low-altitude > high-altitude. 3) The dynamic index (Vpi) of each altitude population was close to 0, indicating that all populations were stable, and the maximum of probability under random disturbance (Pmax) of the middle altitude population was the smallest, indicating that the middle-altitude populations were the most resiliant to random interference. The middle altitude was the most suitable for the growth of H. tibetana. 4) The proportion of seedlings in all populations is likely to decrease, while the proportion of mature and old plants will increase over the next 2, 4 and 6 age classes of time. Any decline in the total populations at the three altitudes is likely due to the lack of young individuals, interspecific and intraspecific competition, and environmental stress. These findings will enable us to predict future growth and death of H. tibetana populations and provide a reliable theoretical foundation for the protection of natural forests in this region. This will be important to the future management of these alpine environments as global climate warming makes its impact.

Key words: Qingzang Plateau, Hippophae tibetana, age structure, population dynamics, altitude gradient