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草业学报 ›› 2020, Vol. 29 ›› Issue (4): 41-50.DOI: 10.11686/cyxb2019306

• 研究论文 • 上一篇    下一篇

荒漠草原土壤种子库对灌丛引入和降水梯度的响应特征

于露1,**, 周玉蓉1,**, 赵亚楠1, 郭天斗1, 孙忠超1, 王红梅1,2,*   

  1. 1.宁夏大学农学院,宁夏 银川 750021;
    2.西北退化生态系统恢复与重建教育部重点实验室,宁夏 银川 750021
  • 收稿日期:2019-07-08 修回日期:2019-08-30 出版日期:2020-04-20 发布日期:2020-04-20
  • 通讯作者: E-mail: whm_826@163.com
  • 作者简介:于露(1995-),女,吉林松原人,在读硕士。E-mail: yulu5890@163.com。周玉蓉(1994-),女,甘肃武威人,在读硕士。E-mail:1206525170@qq.com。
    **共同第一作者.
  • 基金资助:
    国家自然科学基金项目(31860677),国家重点研发计划课题(2016YFC0500505),宁夏科技支撑计划项目(2015惠民计划)和宁夏高等学校一流学科建设项目(NXYLXK2017A01)资助

Responses of the soil seed bank to simulated rainfall levels and anthropogenically introduced shrub encroachment in the desert steppe

YU Lu1,**, ZHOU Yu-rong1,**, ZHAO Ya-nan1, GUO Tian-dou1, SUN Zhong-chao1, WANG Hong-mei1,2,*   

  1. 1.School of Agriculture, Ningxia University, Yinchuan 750021, China;
    2.Ministry of Education Key Laboratory for Restoration and Reconstruction of Degraded Ecosystem in Northwest China, Yinchuan 750021, China
  • Received:2019-07-08 Revised:2019-08-30 Online:2020-04-20 Published:2020-04-20
  • Contact: E-mail: whm_826@163.com
  • About author:**These authors contributed equally to this work.

摘要: 为了揭示宁夏荒漠草原土壤种子库对灌丛引入过程及降水的响应特征,采用室内萌发法和野外水分激发法,对宁夏荒漠草原封育草地、放牧地、不同年限(3、12、22 yr)和间距(40、6、2 m)柠条灌丛地开展草地-放牧-灌丛引入过程的土壤种子库萌发及其对不同降水梯度(-60%,-40%,-20%,0,20%,40%)响应特征进行了研究。结果如下:不同年限、间距引入灌丛地0~200 cm年平均土壤水分含量显著低于封育草地和放牧地(P<0.05),随着灌丛年限和密度增加,加剧深层土壤水分的消耗,土壤旱化加重,使得灌丛地无明显春季返潮期,土壤水分仅为8.14%、8.83%,分别显著低于同期封育草地和放牧地16.00%、13.00%,在这样的水土条件下不同年限、间距灌丛地室内萌发下的0~10 cm土壤种子库密度分别为6186和5831 粒· m-2,分别高于封育草地、放牧地2965、2065粒·m-2(P<0.05)。各样地主要集中于0~5 cm土层,占萌发总数70.04%,且均以一年生猪毛蒿萌发为主,高达87.12%~96.55%,并随灌丛年限和密度的增大而增加,而多年生草本萌发种类仅为5种;不同降水梯度野外激发下的不同年限、间距灌丛地种子萌发平均数量为855和640粒·m-2,以降水量+20%时所激发土壤种子库萌发密度最高,分别为2266和1600粒·m-2,一年生与多年生草本种子库萌发密度和种类均随降水量升高而增加,且均在降水梯度最大时(+40%)呈下降趋势,而且相较于多年生草本,一年生草本在不同灌丛地萌发率高达90.58%~100.00%,显著高于放牧地或封育地(P<0.05),在灌丛引入过程中对土壤干旱和降水变化表现得更为敏感和适应。

关键词: 荒漠草原, 人工灌丛, 土壤种子库, 土壤水分

Abstract: This study explored the responses of the soil seed bank (0-5 and 5-10 cm soil depths sampled) to variation in precipitation and to encroachment by anthropogenically introduced shrubs (Caragana) in desert steppe grassland in Yanchi County, Ningxia Province. Simulated rainfall levels relative to mean annual precipitation of 290 mm (-60%, -40%, -20%, 0, 20%, 40%) were generated for eight otherwise similar sites with different vegetation categories: grassland fenced to preclude grazing (FY), grazed grassland (FM), and grassland with introduced shrubs established for 3, 12, or 22 years (3 sites, PY3, PY12, PY22) or at planting distances of 2, 6, or 40 m (3 sites, PS2, PS6, PS40). Species represented in the seedbank and their numbers were determined using germination counts after incubation of sampled soil in the field and in the greenhouse. A major finding was that in grassland with introduced shrubs, soil moisture for 0-200 cm soil depth was 8.14% when averaged across seasons and over PY sites, and 8.83% when averaged over PS sites, which was significantly lower (P<0.05) than corresponding values for FY and FM sites (16.00% and 13.00%, respectively). PS and PY sites also did not show higher soil moisture levels in spring than in autumn that were seen in FY and FM plots, and the soil moisture reduction at 40 m spacing was about 50% of that at 6 and 2 m shrub spacing. The number of species detected in the soil seed bank in field germination tests at the eight sites ranged between 4 and 7, comprising annual herbs, perennial herbs and shrubs, with total counts of 2965·m-2 and 2065·m-2, respectively, for FY and FM sites; 6198, 6465 and 5897·m-2, respectively, for PY3, PY12 and PY22 sites; and 3898, 5897 and 7698·m-2, respectively, for PS40, PS6 and PS2 sites. Of the total seed bank germination counts across the eight sites, 89.6% (range 87.12% to 96.55%) belonged to the annual herb Artemisia scoparia, and 70.04% came from the 0-5 cm soil layer. The number of species detected in glasshouse pot germination tests at different simulated rainfall levels, for samples from the eight sites, ranged between 1 and 5. For soil samples from all eight sites, the highest numbers of germinated seeds occurred in the +20% rainfall treatments and the lowest in the -60% treatment, while the +40% treatment was usually second lowest. For FY and FM sites the germinated seed density of the +20% treatment was 533 and 233·m-2, respectively. For sites with introduced shrubs, peak germination was 2266·m-2 and 1600·m-2 averaged over PY and PS sites, respectively. In summary, at these sites, introduced Caragana shrubs depleted soil moisture at depth, and the soil moisture reduction increased the dominance in the seedbank of the annual herb Artemisia scoparia, and tended to reduce species richness of the seedbank.

Key words: desert grassland, anthropogenic introduced shrub, soil seed bank, soil moisture