Comparing the recovery of richness, structure, and biomass in naturally regrowing and planted reforestation

Abstract

The clearing of natural vegetation for agriculture has reduced the capacity of natural systems to provide ecosystem functions. Ecological restoration can restore desirable ecosystem functions, such as creating habitat for animal conservation and carbon sequestration as woody biomass. In order to maintain these beneficial ecosystem functions, restoration projects need to mature into self‐perpetuating communities. Here we compared the ecological attributes of two types of restoration, “active” tree plantings with “passive” natural forest regeneration (“natural regrowth”) to existing remnant vegetation in a cleared agricultural landscape. Specifically, we measured differences between forest categories in factors that may predict future restoration failure or ecosystem collapse: aboveground plant biomass and biomass accrual over time (for regrowing stands), plant density and size class distributions, and diversity of functional groups based on seed dispersal and growth strategy traits. We found that natural regrowth and planted forests were similar in many ecological characteristics, including biomass accrual. Despite this, planted stands contained fewer tree recruit and shrub individuals, which may be due to limited recruitment in plantings. If this continues, these forests may be at risk of collapsing into nonforest states after mature trees senesce. Lower shrub density and richness of mid‐story trees may lead to lower structural complexity in planting plots, and alongside lower richness of fleshy‐fruited plant species may reduce animal resources and animal use of the restored stand. In our study region, natural regrowth may result in restored woodland communities with greater conservation and carbon mitigation value.

Restoring riparian forest in the Atlantic Forest: does planting seedlings make a difference?

“…Although our observations should be considered preliminary as the restoring areas are only eight years old, the highest richness and Shannon diversity in passive restoration (when compared to the planting seedlings) are more pronounced in the lower stratum, which suggests a positive prognostic in the evolution of passive restoring sites. Similarly, Staples et al (2020) observed that forest sites under spontaneous regeneration in Australia present higher diversity of two functional groups—fleshy‐fruited species and mid‐story trees—as well as a more abundant and diverse recruit community than in planted sites. Also, in Tropical Africa, Ssekuubwa et al (2019) observed that passively restored forests had higher diversity and abundance of seedlings than similarly aged and actively restored forests.…”

Does restoration success vary with tree size under restoration plantings and regrowth forests?

“…The progressive increase in stem density, basal area, height, and crown width of small, medium, and large trees suggests increasing structural complexity due to restoration that is potentially beneficial to forest wildlife by increasing habitat availability (Staples et al, 2020). However, our results revealed that the structural attributes of stem density, basal area, height, and crown width in the older planting years (i.e., 1995, 1996, and 1997 planting years) tended to decline between 2014 and 2017 sampling years which might be interpreted as an indication of post‐restoration disturbance.…”

Using Propagules to Restore Coastal Marine Ecosystems

“…To design restoration actions that are most likely to meet the goals, it will be important to understand how the choice of activity influences the trajectory of the restored ecosystem. There are few comparisons for marine ecosystems that allow such comparisons, but experimental tests in terrestrial forests have demonstrated differences between naturally regenerating and planted forests (Li et al, 2018;Caughlin et al, 2019;Staples et al, 2020).…”