Community assembly mechanisms and succession processes significantly differ among treatments during the restoration of Stipa grandis – Leymus chinensis communities

Abstract

Understanding community assembly mechanisms is helpful to predict community dynamics. To explore which community assembly mechanism(s) drive(s) the grassland restoration in semi-arid region, we investigated the relationships between plant trait and species relative abundance (SRA), and estimated community functional diversity indices for each community under different treatments (enclosure, grazing and mowing treatment) in a restoration region of Stipa grandis – Leymus chinensis communities in the northern China from 2010 to 2012. There was a high fraction of significant relationships between trait value and SRA, suggesting that niche theory structured the grassland restoration in this region. The functional richness was higher and the functional divergence was lower in the enclosure community than that in the grazing or mowing community, and significantly positive plant height - SRA relationship was found in the enclosure community. These findings demonstrated that limiting similarity based on niche theory was more important in structuring the enclosure community and that environmental filtering based on niche theory played a more important role in driving the grazing or mowing community. Only the factor of year significantly affected the functional evenness (FEve), and the lowest FEve in 2011 implied that the relatively lower precipitation could enhance the effect of limiting similarity on community assembly in the semi-arid grassland.

Shrub‐encroached grassland as an alternative stable state in semiarid steppe regions: Evidence from community stability and assembly

“…Understanding the mechanisms underlying community assembly and predicting community dynamics have long been focused on in the field of ecology (Dong et al, 2019; Kraft, Cornwell, Webb, & Acherly, 2007), especially in the context of restoration ecology (Jones, Barber, & Gibson, 2019). Secondary succession (or restoration process) is community assembly in action with community composition changes, and therefore, it offers a chance to test the relative importance of different assembly mechanisms along the restoration duration (Pinho et al, 2018).…”

Is shrub-encroached grassland a stable state in the semi-arid steppe region?

“…Understanding the mechanisms underlying community assembly and predicting community dynamics has long been a central problem in ecology (Kraft et al, 2007;Dong et al, 2019), especially in the context of restoration communities (Jones et al, 2019). Proposed mechanisms range from niche-based assembly rules (Diamond 1975) to neutral assembly (Hubbell, 2001).…”

“…Due to global changes, large areas of terrestrial communities are degrading, especially in arid and semi-arid regions (Eldridge et al, 2011;Chen et al, 2014;Dong et al, 2019). For example, in the semi-arid Inner Mongolia Steppe in the northern China, large areas of native climax communities, Stipa grandis -Leymus chinensis communities, degraded or even thicketized because of drought caused by climate change and overgrazing by cattle or/and sheep, with the loss of plant diversity and the decline of ecosystem functioning (Peng et al, 2013;Dong et al, 2019). In response, a number of restoration practices were carried out to restore the semi-arid grassland vegetation, and fencing is regarded as an effective management practice (Wu et al, 2009).…”

“…In response, a number of restoration practices were carried out to restore the semi-arid grassland vegetation, and fencing is regarded as an effective management practice (Wu et al, 2009). Therefore, many researches have been focused on the restoration processes (or secondary succession) of different communities, including forest (Muscarella et al, 2015;Liu et al, 2018;Pinho et al, 2018), wetlands (Lozada-Gobilard et al, 2019), grasslands (Conradi et al, 2017;Barber et al, 2019;Dong et al, 2019) and abandoned agricultural fields (Dinnage, 2009). Secondary succession is community assembly in action with changes in species richness as well as community composition, and therefore, it offers a chance to test the relative importance of different assembly processes along restoration duration and its consequences on the structure and functioning of plant communities (Pinho et al, 2018).…”

“…As for the secondary succession of non-shrub-encroached degraded grasslands, both arrivals of propagules from outside and germinations from soil seed bank are very important at the the beginning of restoration, thereby, both random processes (arrival) and environmental filtering (conditions for germination) are expected to dominate the community assembly during the early stage of succession (Meiners et al, 2015;Marteinsdóttir et al, 2018). As successions proceed, competitive exclusion increasingly influences community assembly due to the improvement of abiotic conditions (Chen and Tang, 2016) and interspecific competition (Purschke et al, 2013;Dong et al, 2019). Consequently, the community gradually tends to be relatively stable (Zhang et al, 2019).…”