Figure 1.
Site survey locations in relation to total N deposition (2006).
Figure 2.
Relationships between N deposition and plant species richness and abundance.
A decline of species richness across all plant groups correlates with increasing N deposition (A) and where N deposition and temperatures are higher (B). Whilst graminoid species richness declines in relation to increased N deposition inputs (C), graminoid abundance increases (D), indicating the promotion of fewer species at the higher end of the N gradient.
Table 1.
Summary of optimal models for plant species richness in relation to N deposition and climate variables.
Table 2.
Summary of optimal models for vegetation responses in relation to N deposition and climate variables.
Figure 3.
Relationships between N deposition and lower plant species richness and abundance.
Declines in lichen species richness are related to increasing N deposition (A) whereas bryophyte richness per se is principally influenced by temperature (B). At a species level, however, significant species-specific relationships between N deposition and bryophytes were evident (C, D).
Figure 4.
The influence of N deposition and climate on heathland plant and soil chemistry.
Calluna foliar N concentrations were principally related to changes in temperature (A). However, positive relationships were seen between Calluna litter N concentrations and total N deposition (B). Soil carbon concentrations were higher in areas receiving greater oxidised N inputs and rainfall (C), and soil C:N ratios were also positively related to levels of oxidised N deposition (D).
Table 3.
Summary of optimal models for plant and soil biogeochemical responses in relation to N deposition and climatic variables.
Figure 5.
Relationships between N deposition and litter enzyme activity.
Increasing reduced N deposition was positively correlated with increased litter phenol-oxidase activity in upland sites (A) and litter phosphomonoesterase (PME) activity across all sites (B).