DOI: 10.5061/dryad.3xsj3txgc
title: Degree of intervention affects interannual and within-plot heterogeneity of seed arrival in tropical forest restoration

description: 1. In degraded tropical landscapes lack of seed dispersal can strongly
 limit recovery, and restoration interventions can overcome this barrier by
 attracting dispersers. However, seed dispersal patterns are typically
 studied over short time periods, thus the influences of temporal and
 spatial variability on seed arrival cannot be teased apart. 2. Choice of
 management approach can have important implications for
 restoration-mediated community reassembly. Accordingly, we used a 3.5-year
 record of seed deposition in premontane tropical wet forest in southern
 Costa Rica to examine how seed arrival differed between passive (natural
 regeneration) and active (applied nucleation, plantation) restoration
 after a decade of recovery, compared to remnant forest. We investigated:
 (1) how restoration treatments affected seed deposition rates and
 community composition; (2) how within-plot heterogeneity of
 animal-dispersed seed deposition varied by intervention; and (3) how
 interannual variation influenced animal-dispersed seed arrival across
 treatments. 3. Overall seed rain composition and diversity in restoration
 treatments is converging towards, but still differs substantially from,
 remnant forest (89.7, 86.6, and 76.3% Shannon diversity recovered in
 applied nucleation, plantation, and natural regeneration, respectively).
 4. Within-plot animal-dispersed seed heterogeneity was similar in applied
 nucleation and remnant forest, 27.0% more heterogeneous in applied
 nucleation than plantation, and equivalent when comparing natural
 regeneration to individual active restoration treatments. 5. In contrast
 to active interventions, animal-dispersed tree and shrub communities did
 not differ year to year in natural regeneration, which may promote the
 assembly of relatively homogeneous plant communities at this successional
 stage. 6. Synthesis and applications: Compared to natural regeneration,
 active restoration interventions: (i) catalyzed recovery of seed diversity
 (overall Shannon diversity 17.5 and 13.4% higher in applied nucleation and
 plantation, respectively), (ii) shifted seed community composition towards
 remnant forest more rapidly (overall Shannon diversity 13.4 and 10.2%
 closer), (iii) almost doubled the proportion of later-successional tree
 species arriving, and (iv) had seed communities that differed year to year
 – a pattern not observed in natural regeneration. Finally, applied
 nucleation was the only intervention where seed arrival was as spatially
 heterogeneous as remnant forest, highlighting that this approach may
 facilitate the recovery of specific natural dispersal processes.
description: Description of data collected: Site
 and study description We conducted this study
 at five ~1-ha sites in southern Costa Rica, a subset of the 13 replicate
 restoration sites of this long-term experiment, located between the Las
 Cruces Biological Station (8° 47' 7" N, 82° 57' 32" W)
 and the town of Agua Buena (8° 44' 52" N, 82° 56' 39"
 W). At the start of the study, from 2004-2006, we established three
 0.25-ha (50?50 m) plots separated by a ≥5 m buffer at each site. Three
 restoration treatments: natural regeneration, applied nucleation, or
 plantation, were applied to one of the plots at each of the sites. At
 three of the five sites selected for this study, equivalent sized plots
 were established in adjacent remnant forests to serve as
 references Seed rain data
 We measured seed rain twice monthly from May 2013 - November 2016
 (3.5 yr) in four subplots (separated by ≥10 m) within each treatment plot,
 referred to as sampling ‘stations.’ At each station three 0.25-m2 seed
 traps with 0.69-mm mesh were placed at randomly-selected ≥1-m intervals
 (e.g., at 1.0, 2.5, and 4.5 m) along transects. In total, 216 traps were
 monitored: each restoration treatment had 60 seed traps (5 sites X 4
 stations X 3 traps) and reference forests had 36 traps (3 sites X 4
 stations X 3 traps).      For each sampling period,
 seeds were collected from each trap, stored separately in paper envelopes,
 and then dried at 65°C to preserve until processing. Seeds were counted
 and identified to species using a reference collection at Las Cruces
 Biological Station. We excluded grass seeds (Poaceae), as they are not a
 major component of mature forest flora. Less than 0.01% of seeds were
 identified to only family or morphospecies. Using local knowledge and
 literature reviews, we classified species’ dispersal syndrome
 (ectozoochorous, endozoochorous, anemochorous, explosive, or gravity),
 categorized species as early or later-successional, and grouped species
 into ten growth forms: two herbaceous (forb, vine), eight woody groups
 (liana, shrub, understory palm, understory tree, canopy tree, emergent
 tree), and epiphytes (both herbaceous and woody species).
 Preparation for analysis<br> We summed
 species-level seed(s) observations for each each sampling station for each
 year (rows in the data set). <br>  
description: Species-level seed rain data summed annually at each sampling
 station - WerdenEtAl2021_JAE_seedRainDat.csv  For more
 details see the attached ReadMe file -
 WerdenEtAl2021_JAE_seedRain_ReadMe.txt
 <em>Missing values: </em>The seed length column
 (seedLength) has missing values (represented with NAs) as seed length was
 not recorded for all species.