DOI: 10.5285/8899768c-cc5a-4885-a88b-c08374ee568e
title: Plant structural measurements in North Wales and Northwest England 2013 and 2014

description: The data consists of plant structural plant community measurements from fifteen sites located in the Conwy catchment (North Wales) and from two sites in North West England. Annual aboveground net primary productivity (NPP), canopy height (cht), bryophyte cover (Bcov), leaf dry matter content (LDMC), leaf mass area (LMA) and specific leaf area (SLA) were measured on the dominant plant species. Data were collected in 2013 and 2014. The sites were chosen to represent habitat types and the terrestrial productivity gradient in Britain from intensive agriculturally managed lowland grasslands through to montane heath. Plots within the sites were located using a stratified random sampling design. Plant trait values were taken from existing published databases or were directly measured in each plot for the two species contributing the highest percentage cover.

NPP (grams of dry mass per square metre per year) was measured using a variety of methods according to the plant functional types present. SLA and LDMC was measured on site focussing on the dominant vascular plant species in each plot defined as the two species contributing maximum standing biomass in the year of sampling. Leaf area was calculated based on scanned photographs analysed using Image J software v1.46r.

Plant parameters were tested across a land use intensification gradient to detect parameters that can predict aboveground biomass production across different land management types. Data were used to enhance the predictions of biomass production in the Joint UK Land Environment Simulator model (JULES). Measurements informed the improvement of the nitrogen cycle component in the model.

Measurements were undertaken by trained members of staff from Bangor University, the Centre for Ecology & Hydrology and Exeter University.
This data was collected for the NERC project - The Multi-Scale Response of Water quality, Biodiversity and Carbon Sequestration to Coupled Macronutrient Cycling from Source to Sea (NE/J011991/1). The project is also referred to as Turf2Surf.
description: At the seventeen sites measurements were made in plots ranging in size from 200 metres square to 0.5 metres square located using a stratified random sampling design. The species composition and percentage cover of all plant species was recorded in all plots.

NPP (grams dry mass per metre squared per year) was measured on all dominant plant species at all sites between 2013 and 2014. Measurement of NPP varied according to the plant functional types present. These types comprised 'cool season' C3 graminoids (Poacaea, Junacaea, Cyperacaea), broadleaved and needle-leaved trees, dwarf shrubs, forbs and bryophytes. All plots were visited in early January at the start of each measurement year. Any green material and standing litter was removed by clipping to 1 cm vegetation height. In grazed systems (grasslands and mires) exclosures were installed and the vegetation cut twice throughout the growing season; first at estimated peak biomass and a second time to capture late summer and autumn regrowth. These two values were then summed. In ombrotrophic and minerotrophic peatlands, growth of Sphagnum species was measured over two years using the cranked wire method. Peatland graminoids were measured by harvesting annual biomass accumulation in exclosures over one year using the same methods applied to grazed grasslands. Annual productivity of dwarf shrub heath (Calluna vulgaris) was estimated from a growth curve built from total biomass harvests all carried out in October 2014 on the same ombrogenous mire plateau in the upper Conwy valley. Sampling was carried out across a chronosequence of stands of 5, 11 and 30 year-old Calluna.

In woodlands, different methods were used to measure annual production of trees; litter buckets for leaf litter fall, annual woody mass increment by combining tree-coring, DBH (tree diameter at 1.3 m), wood density and tree height measurements, herbaceous understorey growth by harvesting in one year after cutting back in January and the bryophyte layer by harvesting the moss mat that had grown through coarse plastic meshes of known size pegged securely onto the moss layer in early January and harvested after one year. Measurement of NPP was carried out using plots of varying dimensions scaled to the size of the plant types present but then expressed as production per square metre across all vegetation types.
   
For plant traits in situ measurement of SLA and LDMC was carried out focussing on the dominant vascular plant species in each plot defined as the two species contributing maximum standing biomass in the year of sampling.  LDMC was measured by weighing fresh material consisting of between approximately 10 to several hundred leaves from different plants depending on the size of the leaves. Leaf material was stored in plastic boxes between dampened tissue paper and transported to the laboratory within 24 hours of harvesting. Leaves were then blotted dry and weighed fresh then dried for 24 hours at 80 degrees Celsius and weighed again. LDMC is expressed as g dry mass g-1 fresh mass. SLA was measured by sampling 10 leaves from different plants. Leaf area was calculated based on scanned photographs analysed using the Image J software v1.46r (See Supporting Information). Dry weight was measured as for LDMC. SLA is expressed as square millimetres per milligram of dry mass.

LMA was determined on ten leaves that were scanned or photographed. The dry weight of these leaves was determined. The leaf area was analysed using the program Image J and LMA was calculated.

For plant species abundance in each NPP plot all vascular plant species and bryophytes were identified and cover estimated in intervals of 5 percent. Percentage cover was based on horizontal leaf projection over the plot so that total cover over all species was allowed to exceed 100. 

Mean abundance-weighted trait values for SLA and LDMC were computed for each NPP sampling plot within each site using either the raw percentage cover or square-root transformed cover value for each species in each sample plot within each site. The trait values for each species in each sample plot and within site were based either on replicated measurements on the dominant plants in each plot or, if not dominants, then were extracted from the databases described above. The full details are available in the supporting documentations.

All results were entered into Excel spreadsheets. Results from all the analyses were combined into one Excel spreadsheet. Data were then exported from this combined Excel spreadsheet as .csv files for ingestion into the EIDC.