Nitrogen-enhanced herbaceous competition threatens woody species persistence in a desert ecosystem

• Published in: Plant and soil Vol. 460; no. 1-2; pp. 333 - 345
• Main Authors: She, Weiwei, Bai, Yuxuan, Zhang, Yuqing, Qin, Shugao, Feng, Wei, Lai, Zongrui, Qiao, Yangui, Liu, Liang, Zhang, Wenjin, Miao, Chun
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.03.2021; Springer; Springer Nature B.V
• Subjects: Arid lands; Arid zones; Availability; Biomedical and Life Sciences; Community composition; Competition; Competition (Biology); Composition; Demographics; Demography; Deserts; Ecology; Enrichment; Environmental aspects; Environmental changes; Grasslands; Herbs; Life Sciences; Multivariate statistical analysis; Nitrogen; Nitrogen enrichment; Nitrogen in the body; Plant Physiology; Plant Sciences; Productivity; Regular Article; Resource availability; Shrubs; Soil Science & Conservation; Woody plants; China; Competition; Shrubland; Nitrogen deposition; Precipitation change; Community composition; Plant demography
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-020-04810-y

Aims Water and nitrogen availability are primary determinants of woody communities in dryland ecosystems and are strongly affected by global change. However, the mechanisms by which resource availability and plant demographic responses regulate woody-herb composition are unclear. Methods We investigated plant productivity, shrub demography, and resource availability in a 5-year field experiment involving three levels of precipitation (ambient, + 20% precipitation, + 40% precipitation) and two levels of nitrogen addition (0, 60 kg N ha − 1 yr − 1 ) in a desert shrubland of northern China. Results Increased precipitation had similar positive effects on shrub and herbaceous productivity and, thus, did not alter the community composition. However, nitrogen enrichment dramatically increased herbaceous productivity but tended to decrease shrub productivity. Five years after the experimental manipulation, increased precipitation and nitrogen enrichment significantly altered shrub demography. Increased precipitation decreased the number and cover of small shrubs but increased those of large shrubs. Nitrogen enrichment largely decreased the number and cover of small shrubs, whereas large shrubs showed a higher resistance. Structural equation modeling revealed that nitrogen-enhanced herbaceous competition for water and light potentially reduced shrub growth, especially the growth of small shrubs. Conclusions Our results suggest that large shrubs can coexist with herbs, whereas small shrubs tend to be competitively excluded from the system under enhanced precipitation and nitrogen deposition. Nitrogen enrichment may lead to continued declines in shrub recruitment and growth, and a conversion to grassland. Our findings highlight the competitive and demographic mechanisms underlying the responses of woody communities to global change.