Many studies have highlighted the tremendous utility of using passive restoration (i.e., natural regeneration) to restore tropical forests in a cost-effective manner (Crouzeilles et al., 2017; Poorter et al., 2016). Still others demonstrate that active tree planting can more effectively accumulate carbon than natural regeneration (Philipson et al., 2020; Wheeler et al., 2016). Additionally, passive and active restoration outcomes are difficult to directly compare because passive restoration is generally studied in less disturbed sites that do not require active interventions (e.g., tree planting; Reid et al., 2018). To move past the site-selection bias inherent in many studies comparing passive vs. active restoration, we are seeking sites across Costa Rica to join a distributed restoration experiment. Our ultimate goal is to compare how rates of forest recovery vary across the two most common interventions applied in tropical forests: natural regeneration (passive restoration) vs. tree planting (active restoration).

Experimental goals:

Our initial goals are to compare recovery rates of vegetation structure and carbon sequestration, plant species richness and functional diversity, and soil carbon and fertility vary between natural regeneration vs. tree planting restoration interventions. If time allows we will examine how other aspects of the ecosystem recover as well (e.g., vertebrate and invertebrate community, soil microbiome).

Experimental implementation:

1. At sites where your organization is already carrying out restoration, the aim to pair “natural regeneration” (NR) with “tree planting” (TP) treatment plots so that the outcomes can be compared.

2. To the extent possible, the areas under each pair of treatments should be a similar as possible (i.e., same soil types, slope, similar existing vegetation or grass type).

3. We will provide guidance on how to sample initial vegetation and on how to monitor growth of planted and naturally regenerating woody vegetation. The first monitoring should be done immediately after the tree planting and then every two years.

4. For obvious reasons, it is important to leave the naturally regeneration treatments unplanted and protected in the same way as the tree planting treatments.
   
   Requirements to become a site:
   

1. An established program using active tree planting of native and/or naturalized species for forest restoration. The tree planting approach must be targeted to restore native forest, and can include plantation style planting, spatially patterned planting (e.g., strips, clusters) or riparian strip restoration planting.

2. Areas that are mostly cleared of existing vegetation and/or have not been regenerating for more than three years.

3. Space to install a minimum of six plots (min. size: 0.10 hectare; ~1000 m2 or ~32 x 32 m) per intervention (natural regeneration vs. tree planting).

4. A person on staff who is responsible for overseeing the collaborative project and who will be responsive to communication and facilitate data collection.
   
   
   What we offer:
   
   

1. Participation in a large-scale collaborative project over a 5+ year timeframe

2. Training for staff on monitoring methods, technical support and possible on-site support

3. Consulting and guidance for project establishment and initial data collection

4. Co-authorship on collaborative papers

5. Opportunity to lead publications based on supplementary data sets collected at your site

6. Networking opportunities and visibility

7. Participation in workshops / training on new technologies for restoration monitoring
   
   What we ask:
   

1. Partner organizations must comply with all local laws, including any referring to international agreements

2. Project protocols must be followed carefully, and sites must be sampled according to the project schedule (every two years)

3. Sign a data sharing agreement and upload/share data

4. Partners are responsive to communications and questions related to project

5. Co-authors must comment on the respective manuscripts and/or indicate that they agree with the content of the work

6. Partners must share project-related photos & video for outreach and communications purposes
   
   Quantifying recovery rates:
   
   We will provide a variety of protocols to track: (1) rates of biomass accumulation and (2) rates of biodiversity recovery
   
   General Timeline:
   Experiment installed: By end of 2027 * We can also work with already established planted areas assuming that there are similar, nearby unplanted areas with similar characteristics.
   Baseline data collection commences: Immediately after active restoration (tree planting) is completed.
   Bi-annual survey of recovery indicators: Every two years during growing season