ResumenThe n-alkanes in plant cuticular wax have been used as markers for estimating the species composition of herbivore diets, but the long -chain fatty alcohols (LCOH) of plant wax may also be useful. The objective of this research was to assess if LCOH contributed extra information to differentiate plant species, compared with n-alkanes only. We used 3 data sets consisting of nalkane and LCOH concentrations of plant species occurring in pastures of New South Wales, Australia. We used Principal Component Analysis (PCA) to summarise the data for n-alkane and LCOH concentrations obtained for the species in these data sets. The first 3 principal components explained 86 to 93% and 75 to 99% of the variance in n-alkane and LCOH concentrations, respectively. Orthogonal Procrustes Rotation (OPR) was then used to compare the results of PCA conducted with n-alkane and LCOH data, with a view to establishing whether LCOH provided discriminatory information in addition to that provided by the nalkanes. Results of OPR indicated that this was so for all 3 data sets, and suggested that the LCOH would be useful additional markers for discriminating between plant species. We tested this by using Discriminant Analysis and cross -validation procedures in 2 data sets to distinguish between defined species groups of C3 grasses, C4 grasses, clovers and Lotus spp. The discrimination between these categories and the proportion of plant species correctly classified into the defined categories was better when using n-alkanes and LCOH together, compared with alkanes alone. Our results indicate that LCOH provided additional information that could be used for distinguishing plant species as part of estimating the species composition of herbivore diets.

Nutrients and herbivores are well-known drivers of grassland diversity and stability in local communities. However, whether they interact to impact the stability of aboveground biomass and whether these effects depend on spatial scales remain unknown.It is also unclear whether nutrients and herbivores impact stability via different facets of plant diversity including species richness, evenness, and changes in community composition through time and space. We used a replicated experiment adding nutrients and excluding herbivores for 5 years in 34 global grasslands to explore these questions. We found that both nutrient addition and herbivore exclusion alone reduced stability at the larger spatial scale (aggregated local communities; gamma | 2679 CHEN Et al.

Nutrient enrichment can simultaneously increase and destabilise plant biomass production, with co‐limitation by multiple nutrients potentially intensifying these effects. Here, we test how factorial additions of nitrogen (N), phosphorus (P) and potassium with essential nutrients (K+) affect the stability (mean/standard deviation) of aboveground biomass in 34 grasslands over 7 years. Destabilisation with fertilisation was prevalent but was driven by single nutrients, not synergistic nutrient interactions. On average, N‐based treatments increased mean biomass production by 21–51% but increased its standard deviation by 40–68% and so consistently reduced stability. Adding P increased interannual variability and reduced stability without altering mean biomass, while K+ had no general effects. Declines in stability were largest in the most nutrient‐limited grasslands, or where nutrients reduced species richness or intensified species synchrony. We show that nutrients can differentially impact the stability of biomass production, with N and P in particular disproportionately increasing its interannual variability.

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