Precipitation and nitrogen deposition alter biocrust–vascular plant coexistence in a desert ecosystem: Threshold and mechanisms. (6th January 2022)

• Record Type: Journal Article
• Authors: She, Weiwei; Chen, Ning; Zhang, Yuqing; Qin, Shugao; Bai, Yuxuan; Feng, Wei; Lai, Zongrui; Qiao, Yangui; Liu, Liang; Zhang, Wenjin; Miao, Chun
• Is Part Of: Journal of ecology. Volume 110:Number 4(2022)
• Page Start: 772
• Page End: 783
• Publication Date: 2022-01-06
• Subjects: biological soil crust -- competition -- critical threshold -- nitrogen enrichment -- plant–plant interactions -- precipitation change -- shrubland; Plant ecology -- Periodicals; 577.05
• DOI: 10.1111/1365-2745.13834
• Languages: English
• ISSNs: 0022-0477

Abstract

Abstract: Dryland ecosystems exist in various vegetation landscapes with contrasting compositions of vascular plants and biocrusts (surface‐soil mats comprised of soil particles, cyanobacteria, lichens, mosses and fungi), and they are very vulnerable to ongoing global change. However, compared to vascular plants, the responses of biocrusts and their coexistence with vascular plants to global change remain elusive. We conducted a 5‐year experiment involving multi‐level precipitation and nitrogen addition in a desert shrubland of northern China to examine these responses. We found that shrubs, perennial herbs and annuals exhibited facilitative, competitive and insignificant effects on biocrusts respectively. Biocrusts coexisted with vascular plants below a threshold of herbaceous productivity of approximately 70 g/m 2 and tended to be replaced by herbs beyond this threshold, resulting from the balance between the shade tolerance of biocrusts and herb‐induced light limitation. Increased precipitation and nitrogen enrichment altered biocrust–vascular plant composition by influencing this balance and tended to shift from a biocrust‐dominated to a vascular plant‐dominated state when the threshold was crossed. Synthesis . Our results suggest that biocrusts can coexist with dwarf shrubs and annuals, but cannot withstand perennial herbs when the herbaceous productivity threshold was exceeded. Our findings provide new insights into the threshold and mechanisms of biocrust–vascular plant coexistence, which may greatly contribute to managing dryland ecosystems for global change. Abstract : In a precipitation and nitrogen manipulation experiment in a desert shrubland, we found that biocrusts can coexist with dwarf shrubs and annuals, but not withstand perennial herbs when the herbaceous productivity threshold (~70 g/m 2 ) was exceeded. This study provides new insights into the threshold and mechanisms of biocrust–vascular plant coexistence, with important implications for dryland conservation and management. 摘要: 旱区植被由维管植物和生物土壤结皮构成, 对全球变化十分敏感。然而, 相较于维管植物, 全球变化对生物土壤结皮及其与维管植物共存关系的影响, 并不清楚。 本研究以毛乌素沙地油蒿 ( Artemisia ordosica ) 灌木地为研究对象, 通过连续5年的降水和氮素增加控制试验来探究这一问题。 结果显示, 灌木、多年生草本和一年草本对结皮分别具有促进、竞争和中性作用。 当草本植物地上生产力低于70 g m −2 时, 结皮与维管植物共存; 当草本超出该阈值时, 结皮将被草本取代。结皮的耐荫性与草本介导的光限制之间的平衡, 决定了二者间的阈值响应关系。降水和氮素增加通过影响这一平衡关系进而改变结皮‐维管植物组成, 并驱使生态系统从以结皮为主的状态转向以维管植物为主的状态。 研究表明, 结皮能够与矮灌木和一年生草本共存, 但与多年生草本不能持续共存。当草本地上生产力超过70 g m −2 时, 结皮将被维管植物取代。研究揭示了结皮与维管植物共存的阈值和机制, 这对于全球变化背景下旱区生态系统的保育和管理, 具有十分重要的意义。