荒漠土壤盐渍化与放牧对植物种群扩散的影响：以苦豆子为例

Soil salinization is one of the main types of land desertification. Air drying and huge soil evaporation result in increasing soil salinization, negatively affects on vegetation growth and diffusion in the northwest desert region of China. Sophora alopecuroides, a widely distributed perennial moderate halophyte in this area, has nitrogen fixing, medicinal, forage, green manure and ecological function, and plays an important role in the regional ecological balance and economic development. Its population diffusion includes clones (clone) and sexual reproduction (seed). This project is conducted using the method of laboratory experiment combined with field experiment, study on ① the effects of soil salinization on cloning and seeds reproduction of Sophora alopecuroides; ② the soil salinization effects on the survival and growth of the seedlings; ③ the effects of soil salinization on its nitrogen fixation ability; ④ the effects of allelopathy on the formation and diffusion of its population; ⑤ the effects of grazing on the population diffusion of Sophora alopecuroides. The objective is to reveal the responses of the reproduction and growth of Sophora alopecuroides to soil salinization, the population diffusion and adaptation strategies, as well as the effects of grazing in the desert steppe. Our team has good basis for further study, mature research methods, reasonable personnel structure, and the successful completion of the project can be guaranteed. The results will provide theoretical basis for exploring the mechanism of the desert ecosystem stability and regional economic development.

土壤盐渍化是荒漠化的主要类型之一。我国西北荒漠地区空气干燥、蒸发量大、土壤盐渍化日益严重，对植物生长与扩散产生了抑制作用。苦豆子是该地区草地退化后常见的优势草本植物，兼具药用、饲用、绿肥和生态价值，其种群扩散包括无性（克隆）、有性（种子）繁殖两种途径。本项目采用室内控制实验与野外原位实验相结合的方法，研究①土壤盐渍化对苦豆子克隆及种子繁殖的影响；②苦豆子幼株生长对盐胁迫的响应与适应策略；③土壤盐渍化对苦豆子种群密度与结构的影响；④苦豆子化感作用对其种群形成与扩散的影响；⑤放牧对苦豆子种群扩散的影响。目的是探明苦豆子繁殖速率与植株生长对盐胁迫的应答机制，揭示荒漠绿洲苦豆子种群形成与扩散生理机制，及放牧对物种多样性与种群扩散的影响。项目组具有较好的研究基础，研究方法成熟，人员结构合理，能保证项目的顺利完成。研究成果将为探讨荒漠地区植被生态恢复与环境效应、区域生态平衡与可持续发展提供理论基础。

项目背景.苦豆子是一种盐中生植物，是我国西北荒漠区土壤盐渍化后快速形成的优势种群，并成快速扩散之势。本项目采用室内控制实验与野外原位实验相结合的方法，探讨盐胁迫对苦豆子种子繁殖与幼苗生长的影响；苦豆子化感作用及放牧对苦豆子种群形成与扩散的影响，为探讨荒漠区植被群落演替与区域生态平衡提供理论基础。.研究内容.① 盐胁迫对苦豆子种子繁殖及幼株生长的影响；.② 苦豆子化感作用对群落演替及生物多样性的影响；.③ 土壤盐渍化与放牧对苦豆子种群形成与扩散的影响；.重要结果.① 一定程度盐胁迫抑制了苦豆子种子繁殖及幼苗生长.中度盐胁迫对苦豆子种子萌发和幼株生长均造成轻微障碍，但重度盐胁迫导致苦豆子种子发芽率大幅下降，幼株生长受到严重抑制，甚至不能成活。.② 苦豆子化感作用有利于其种群形成，但不利于群落物种多样性.苦豆子化感作用抑制其伴生植物繁殖，有利于其自身种群形成与扩散，但容易促使群落向物种简单化方向演化，造成该地区植物群落物种丰富度下降，相应地也会降低群落稳定性。.③ 土壤盐渍化与放牧对苦豆子种群形成与扩散的影响.随着荒漠区土壤盐渍化程度的日益加重，许多盐敏感的植物逐渐被淘汰，而像苦豆子等耐盐植物得以快速繁殖，从而促成了苦豆子种群的快速形成与扩散，但其扩散范围受种源位置的限制。放牧对苦豆子种群扩散具有很大的帮助：一则苦豆子种子经过牲畜消化道后发芽率显著提高，二则随着动物活动范围的扩大，将苦豆子种子带到较远的地方，扩大了苦豆子种群扩散范围。.关键数据及其科学意义.荒漠区土壤盐渍化逐渐淘汰了一些盐敏感物种，而像苦豆子等耐盐植物得以快速繁殖，再加上苦豆子化感作用及放牧增加了苦豆子种群扩散的速度和范围，两种因素对苦豆子种群扩散极为有利，但不利于苦豆子伴生植物的繁殖，从而降低了该区域植物群落物种丰富度，可能会减弱群落稳定性而向物种简单化演替，研究结果将对探讨荒漠区群落演替机制具有重要的意义。

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