DOI: 10.5061/dryad.12jm63z6j
title: Resource limitation of compensatory responses in ecosystem processes after biodiversity loss

description: Biodiversity loss may result in a decline in important ecosystem
 processes. The effect of biodiversity loss on ecosystem functioning is
 determined by the functional contribution of the species lost and the
 compensatory responses of the remaining species. It is unknown to what
 extent the strength of the compensatory response of the remaining species
 depends on resource availability. Here we evaluate how the primary
 production of an assemblage of salt marsh plants responds to a realistic
 sequence of species loss in a 7-year experiment, with and without the
 addition of fertiliser. We found near-full compensation of progressive
 species loss in gross community primary production by the
 extinction-resistant species with fertiliser as long as one species
 (Triglochin maritima) remained. Without fertiliser, at least 4 species,
 including the particularly abundant species Plantago maritima, were needed
 to maintain gross community primary production. These results suggest that
 the magnitude of the compensation by extirpation-resistant species for the
 decline in ecosystem processes associated with progressive biodiversity
 loss depends on the resource context, and that compensation after the loss
 of plant species can be accelerated by increasing resource availability.
 Ultimately, full compensation appears to be limited by the presence and
 abundance of species in the remaining community that possess traits that
 allow them to compensate for the species lost. These findings suggest that
 the conclusions of a large body of biodiversity-ecosystem experiments
 cannot be used for informing the management of natural systems, because
 they do not simulate realistic extinction sequences, and therefore cannot
 quantify the potential for compensation of ecosystem services in the real
 world.
description: We evaluate how the primary production of an assemblage of salt
 marsh plants responds to a realistic sequence of species loss in a 7-year
 experiment, with and without the addition of fertiliser.
 Following a previous study by Davies<em> et al.</em>
 (2012) on algal impact in salt marshes, this paper investigates how plant
 communities respond to the gradual loss of species caused by increasing
 fucoid algae deposits. Ninety 1-m<sup>2</sup> experimental
 plots spaced ~ 3 m apart were established in an area of transitional low
 salt marsh in the Cefni estuary, Anglesey, Wales, UK (53°10′12″ N:
 4°23′39″ W). In June 2009, the undisturbed assemblage of salt marsh plants
 was manipulated. A central 40 x 40 cm area of each of 32 plots was
 randomly allocated to a stage in the extirpation sequence of species in
 response to increased volumes of fucoid algae deposited on the marsh
 surface (see Davies<em> et al.</em>, 2012). Species were
 removed on a species-by-species basis following the derived extirpation
 sequence (<em>Salicornia ramosissima </em>J<em>.
 </em>Woods<em>, &lt; Puccinellia maritima
 </em>(Huds.) Parl.<em> &lt; Armeria maritima
 </em>(Mill.)<em> &lt; Limonium humile
 </em>Mill.<em> &lt; Plantago maritima
 </em>L.<em> &lt; Aster tripolium </em>L.
 <em>&lt; Triglochin</em> <em>maritima </em>L.,
 from least to most extirpation resistant). The
 experiment lasted for 7 years from 2009 to 2017. To quantify whether
 compensation was context-dependent, and limited by nutrient availability,
 half the plots for each treatment (n = 2 per treatment) where fertilised
 in 2013 while the rest of the plots (n = 2 per treatment) were left
 unfertilised. Fertilisation was carried out by spreading 50g of Osmocote
 slow release fertiliser pellets per 40x40 cm plot on 07/05/2013. These
 pellets were not visible anymore in 2015 and therefore the treatment was
 repeated on 28/05/2015. The experiment was finished after 7 years in
 2017. During every summer growth season, one or more
 samples were collected for each replicate treatment plot in each year to
 provide an average value of gross community productivity and % cover per
 plant species over the peak of each growing season. At the end of the
 experiment in 2017, the biomass of each plant species in each plot was
 also measured destructively. Gross community
 productivity (GCP, a measure of primary production) was quantified once or
 more in every year during June, July, August, and/or September (dates
 given in SM). Gross community productivity (GCP) was estimated as
 CO<sub>2</sub> flux recorded using an LI-840
 CO<sub>2</sub>/H<sub>2</sub>0 gas analyser (LI-COR
 Biosciences, Lincoln, NE, USA) connected to a clear plexiglass chamber
 (0.09 m<sup>2</sup> internal base area, 0.19 m high, internal
 volume = 17.1 litres). GCP was estimated using the rate of
 CO<sub>2</sub> flux recorded during consecutive light and dark
 measurements representing net community productivity (NCP,
 CO<sub>2</sub> utilization by photosynthesis plus
 CO<sub>2</sub> production by respiration) and community
 respiration (CR, CO<sub>2</sub> production during
 respiration), respectively. GCP was then estimated as GCP = NCP - CR and
 expressed at the community level as mmol CO<sub>2</sub> uptake
 m<sup>-2</sup> h<sup>-1</sup>.
 CO<sub>2</sub> flux measurements were recorded in a stratified
 random order between 10:00 h and 14:00 h BST during a neap tidal cycle on
 days with low cloud cover to minimize imprecision caused by the effect of
 abiotic factors on photosynthetic rates. In addition, GCP measurements
 were recorded only where light levels exceeded 700 µmol PPFD
 m<sup>-2</sup> s<sup>-1</sup>, a previously
 observed threshold above which variation in ambient light level has
 minimal impacts on primary production in this salt marsh
 community. Total dry-weight biomass by species was
 measured at the end of the experiment in September 2017 by clipping all
 vegetation at the soil level. Species biomass could only be estimated
 before the end of the experiment as this required destructive sampling. To
 estimate a proxy for total community biomass before the end of the
 experiment, the abundance of each species in each plot was assessed as %
 cover using a 0.3 x 0.3 m point quadrat (49 point intersections) in July
 and/or August. The vegetation cover and GCP were not measured in
 2015.
description: # **Resource limitation of compensatory responses in ecosystem processes
 after biodiversity loss**
 [https://doi.org/10.5061/dryad.12jm63z6j](https://doi.org/10.5061/dryad.12jm63z6j) We evaluate how the primary production of an assemblage of salt marsh plants responds to a realistic sequence of species loss in a 7-year experiment, with and without the addition of fertiliser. The cover per plant species and the primary production were quantified in most years, and photos were taken of the plots in each year. We quantified the biomass at the end of the experiment. **Description of the data and file structure** The file **Treatments.csv** specifies what species richness and fertiliser treatment was allocated to each plot number. The column *Treat* indicates the treatment level, which defines the species richness treatment *SR*. ‘Control’ means that the species richness was not manipulated. For the other treatments, species were removed on a species-by-species basis following the derived extirpation sequence (*Salicornia ramosissima* J. Woods, &lt; *Puccinellia maritima* (Huds.) Parl. &lt; *Armeria maritima* (Mill.) &lt; *Limonium humile* Mill. &lt; *Plantago maritima* L. &lt; *Aster tripolium* L. &lt; *Triglochin maritima* L., from least to most extirpation resistant). *Plot* indicates the plot number, which is used to match across the different data files. The column *Fertiliser* indicates if the plot was fertilised (“Fertiliser”) or not (“None”) from 2013 onwards. The file **Flux.data.2009.2017.csv** gives the estimated gross community production (GCP, mmol CO2 uptake m-2 h-1) for each plot for each measurement, for all years in which this was measured. *Plot* indicates the plot number, which is used to match across the different data files. *Year* indicates when the measurement was taken, as a decimal year. Month is the month in which the measurement was taken. GCP indicates the gross community production in mmol CO2 uptake m-2 h-1). The column *Treat* indicates the treatment level, which defines the species richness treatment *SR*. ‘Control’ means that the species richness was not manipulated. For the other treatments, species were removed on a species-by-species basis following the derived extirpation sequence (*Salicornia ramosissim*a J. Woods, &lt; *Puccinellia maritima* (Huds.) Parl. &lt; *Armeria maritima* (Mill.) &lt; *Limonium humile* Mill. &lt; *Plantago maritima* L. &lt; *Aster tripolium* L. &lt; *Triglochin maritima* L., from least to most extirpation resistant). *Plot* indicates the plot number, which is used to match across the different data files The column *Fertiliser* indicates if the plot was fertilised (“Fertiliser”) or not (“None”) from 2013 onwards. The file **Cover measurements 2009.2017.csv** gives the cover by plant species for each date at which this was quantified. Cover was quantified at 49 points, and the numbers indicate the number of points at which a plant species was found. Multiple plant species can be found at a single point. *Date* gives the date of the measurement as dd/mm/yyyy. *Plot* indicates the plot number, which is used to match across the different data files. The following columns (Salicornia, Puccinellia, Armeria, Limonium, Plantago, Aster, Triglochin, Spergularia, Halimione, Bare, Algal mat) give the number of points at which a plant species was found. Bare indicates that no plant or algal mat was present under a point. The file **Dry_weight_09_2017.csv** gives the dry weight per plant species in g per plot at the final harvest in September 2017. *Plot* indicates the plot number, which is used to match across the different data files. Total gives the total dry weight for all plant species combined per plant species in g per plot. The following columns (Salicornia, Puccinellia, Armeria, Limonium, Plantago, Aster, Triglochin, Halimione, Spergularia_marina) give the total dry weight per plant species in g per plot. There are 9 folders with photos of every plot taken between 2011 and 2017. The size of the square aluminum frame in the photos is 40 by 40 cm. The folders are labelled as **Photosddmmyy**, while the filename for the photos indicates the plot number. A few photos are missing because they were mistakenly not taken during the survey. A single replicate per treatment/fertiliser combination for the 2017 photos is presented in the paper, and these photos are not included in this submission for copyright reasons.