Based on this: Expert Group 4: Seedling stage distance-dependent mortality experimentWe collected ripe fruits and seeds from Premna and Psychotria trees on each island.Seedlings were grown in nurseries on Saipan (for Saipan and Tinian plants), Rota andGuam in September 2010. When seedlings grew their first true leaves, we transplantedthe healthiest seedlings into single cell trays, then outplanted them into the field 1–3months later.Outplanting occurred at five sites on Guam and three sites each on Saipan, Tinian andRota; all sites were at least 500 m and often several km apart, and nearly all sites werethe same as or adjacent to the sites used to collect seed rain (above). Sites wereselected, based on the following criteria: must be comprised primarily of native treespecies, have a karst substrate, and be dominated by Ficus spp. and Pisonia grandis,with an understory of Guamia mariannae, Aglaia mariannensis, Cynometra ramifloraand/or Eugenia reinwardtiana. Within a 60 × 60 m area at each site, we mapped thelocation of all adult (>4 cm diameter at breast height) trees, and used these maps toselect locations that were either near (under or within 1 m of the canopy) or far(typically >7 m) from the parent tree. If there were few adult trees of the same species,we placed two to four ‘near’ plots under the same tree. We set up a chicken wire fence(height 0.9–1.2 m) around each plot to prevent browsing by pigs or deer. Theseungulates are present only on Guam and Rota, but the fences were added to plots onSaipan and Tinian as well to control for any fence effect.We planted 10 seedlings in each near and far plot designated for that species at eachsite on all four islands. Eighty seedlings of each species were planted per site for atotal of 1,120 Premna and 700 Psychotria seedlings across all islands. Premna wasplanted at every site on all islands (total 14 sites). Psychotria was planted at three siteson Saipan, three sites on Rota and three sites on Guam (total nine sites). We did notoutplant Psychotria at two sites on Guam due to a lack of adults or at any sites onTinian due to a lack of seedlings. Premna was outplanted in December 2010, andPsychotria between January 2011 and March 2011. The vast majority of plots, near orfar, contained zero conspecific seedlings and few plots contained more than one ortwo conspecific seedlings, therefore we did not manipulate existing conspecificseedling density or include it in the analysis. Premna seedlings were surveyed forsurvival in July 2011, and Psychotria seedlings were surveyed in July 2012.Because light limitation has a strong effect on seedling survival, we used a sphericaldensiometer to record canopy openness at each fence. Four measurements were takenper fence (one in each cardinal direction), then averaged to get a single estimate ofcanopy openness. single individual conducted all densiometer readings, a All sites onan island were surveyed in the same day, and surveys were not conducted duringstrong wind or rain showers.Extra Details on Modeling ApproachWe used a binomial GLMM to test the impacts of distance to the nearest conspecificadult (‘near’ versus ‘far’) on the proportion of seedlings alive in each plot at the endof the experiment. The full model included bird presence, nearest-neighbor distanceand their interaction as fixed effects to test whether any change in survival withdistance was steeper on Guam. We also included canopy openness and the openness ×distance interaction to test whether the effect of distance was modified by lightenvironment. Canopy openness values were mean-centered before analysis. Allmodels included site as a random effect on the intercept. We used model comparisonbased on AICc to identify the best-fitting model. We used profile likelihood toestimate 95% confidence intervals around the coefficients, based on contrasts withGuam (no birds) and ‘near’ as the reference levels for the island and distance factorsrespectively. The two species (Psychotria and Premna) were analysed independently Answer these questions: - What are the controls - What are the specific explanatory variables that varied - What were the response variables - What was the experimental process in simplified steps
Based on this:
Expert Group 4: Seedling stage distance-dependent mortality experiment
We collected ripe fruits and seeds from Premna and Psychotria trees on each island.
Seedlings were grown in nurseries on Saipan (for Saipan and Tinian plants), Rota and
Guam in September 2010. When seedlings grew their first true leaves, we transplanted
the healthiest seedlings into single cell trays, then outplanted them into the field 1–3
months later.
Outplanting occurred at five sites on Guam and three sites each on Saipan, Tinian and
Rota; all sites were at least 500 m and often several km apart, and nearly all sites were
the same as or adjacent to the sites used to collect seed rain (above). Sites were
selected, based on the following criteria: must be comprised primarily of native tree
species, have a karst substrate, and be dominated by Ficus spp. and Pisonia grandis,
with an understory of Guamia mariannae, Aglaia mariannensis, Cynometra ramiflora
and/or Eugenia reinwardtiana. Within a 60 × 60 m area at each site, we mapped the
location of all adult (>4 cm diameter at breast height) trees, and used these maps to
select locations that were either near (under or within 1 m of the canopy) or far
(typically >7 m) from the parent tree. If there were few adult trees of the same species,
we placed two to four ‘near’ plots under the same tree. We set up a chicken wire fence
(height 0.9–1.2 m) around each plot to prevent browsing by pigs or deer. These
ungulates are present only on Guam and Rota, but the fences were added to plots on
Saipan and Tinian as well to control for any fence effect.
We planted 10 seedlings in each near and far plot designated for that species at each
site on all four islands. Eighty seedlings of each species were planted per site for a
total of 1,120 Premna and 700 Psychotria seedlings across all islands. Premna was
planted at every site on all islands (total 14 sites). Psychotria was planted at three sites
on Saipan, three sites on Rota and three sites on Guam (total nine sites). We did not
outplant Psychotria at two sites on Guam due to a lack of adults or at any sites on
Tinian due to a lack of seedlings. Premna was outplanted in December 2010, and
Psychotria between January 2011 and March 2011. The vast majority of plots, near or
far, contained zero conspecific seedlings and few plots contained more than one or
two conspecific seedlings, therefore we did not manipulate existing conspecific
seedling density or include it in the analysis. Premna seedlings were surveyed for
survival in July 2011, and Psychotria seedlings were surveyed in July 2012.
Because light limitation has a strong effect on seedling survival, we used a spherical
densiometer to record canopy openness at each fence. Four measurements were taken
per fence (one in each cardinal direction), then averaged to get a single estimate of
canopy openness. single individual conducted all densiometer readings, a All sites on
an island were surveyed in the same day, and surveys were not conducted during
strong wind or rain showers.
Extra Details on Modeling Approach
We used a binomial GLMM to test the impacts of distance to the nearest conspecific
adult (‘near’ versus ‘far’) on the proportion of seedlings alive in each plot at the end
of the experiment. The full model included bird presence, nearest-neighbor distance
and their interaction as fixed effects to test whether any change in survival with
distance was steeper on Guam. We also included canopy openness and the openness ×
distance interaction to test whether the effect of distance was modified by light
environment. Canopy openness values were mean-centered before analysis. All
models included site as a random effect on the intercept. We used model comparison
based on AICc to identify the best-fitting model. We used profile likelihood to
estimate 95% confidence intervals around the coefficients, based on contrasts with
Guam (no birds) and ‘near’ as the reference levels for the island and distance factors
respectively. The two species (Psychotria and Premna) were analysed independently
Answer these questions:
- What are the controls
- What are the specific explanatory variables that varied
- What were the response variables
- What was the experimental process in simplified steps
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