Effects of nitrogen deposition on tundra vegetation undergoing invasion by Deyeuxia angustifolia in Changbai Mountains

Abstract

In recent years, herbaceous species such as Deyeuxia angustifolia (Kom.) Y. L. Chang has invaded alpine tundra regions of the western slope of the Changbai Mountains. Because atmospheric nitrogen deposition is predicted to increase under a warming climate and D. angustifolia is sensitive to nitrogen addition, field experiments were conducted from 2010 to 2013 to determine the effect of increased nitrogen deposition on the mechanisms of D. angustifolia invasion. The goal of this study is to evaluate the impact of increased nitrogen deposition on the changes in alpine tundra vegetation (consisting mostly of Rhododendron chrysanthum Pall. and Vaccinium uliginosum Linn.). The results showed that: 1) simulated nitrogen deposition affected overall characteristics and structure of R. chrysanthum and V. uliginosum communities and had a positive impact on the growth of tundra vegetation invaded by D. angustifolia; 2) R. chrysanthum was more resistant to invasion by D. angustifolia than V. uliginosum; 3) simulated nitrogen deposition could improve the growth and enhance the competitiveness of D. angustifolia, which was gradually replacing R. chrysanthum and V. uliginosum and might become the dominant species in the system in future, transforming alpine tundra into alpine meadow in the Changbai Mountains.

The Changbai Alpine Shrub Tundra Will Be Replaced by Herbaceous Tundra under Global Climate Change

“…Jin et al (2016) [36] suggest that herbaceous species have now been forming patches on the alpine tundra zone and becoming a co-dominant plant species with shrubs that have correspondingly been becoming fragmented and patchy. Therefore, the tundra seems to be transforming into alpine meadows [36,37].…”

“…The aggregate intensity of R. chrysanthum is the weakest, while the aggregate intensity of herbs is usually stronger. Moreover, the associations among six dominant herbs are different and their associations are low [37]. This phenomenon indicates that there may be differences in habitat selection among dominant herbs and, thus, they may occupy various spatial locations.…”

Soil Microbial Community and Enzyme Activity Responses to Herbaceous Plant Expansion in the Changbai Mountains Tundra, China

“…Increasing available N and P enhanced the com-petitiveness of herbaceous plants, and it had a direct adverse effect on shrubs which was reflected by gradual replacement of shrubs by herbs (Aerts et al, 1990;Alons et al, 2001). Jin et al (2016a) also found that increased available nitrogen significantly promoted nitrophilous herbs such as C. angustifolia. This increased the competitive ability of these herbs, and these herbs became the new dominant species by gradually replacing shrubs such as R. chrysanthum and V. uliginosum.…”

“…Herbaceous plants on the western slopes of the Changbai Mountains tundra have increased since the 1990s, and they have successfully invaded this alpine landscape with a gradual trend that follows an altitudinal gradient. These herb species, which previously either occurred in the birch forest zone or were occasionally observed in tundra, are now forming patches and have often become common or even dominant species (Jin et al, 2016a). Currently, the expansion range has extended from relatively low elevations to higher elevations in the tundra.…”

“…Expansion of the herbaceous plant Calamagrostis angustifolia into tundra areas is thought to be related to climate change and vegetation succession (Xu and Zhang, 2010). Water erosion of volcanic ash, vegetation succession, as well as the physical and chemical soil properties can also impact herbaceous plant upward expansion from low elevation forest areas into high elevation tundra areas (Jin et al, 2013;2014;2016a). However, long-term observation of the below-ground processes for herb expansion phenomenon in the tundra of the Changbai Mountains is limited.…”