Ecological implications of changes in vegetation elemental composition under different heather (Calluna vulgaris)...

Heather (Calluna vulgaris)-dominated peatlands are important biodiversity habitats, often shaped by historical management. In the UK, these habitats were traditionally burnt to rejuvenate vegetation for grazing. Heather burning intensified over the last two centuries for red grouse (Lagopus lagopus scoticus) management, creating a mosaic of vegetation composition and ages for shelter, foraging and nesting of many rare upland birds. More recently, burning has been claimed to negatively impact peatlands and associated key ecosystem services, including carbon storage. Regulation has consequently tightened, with burning replaced by cutting or no heather management. However, surprisingly little is known regarding long-term management effects and evidence of negative burning impacts remains contested. Here, we examine how these three management approaches affect elemental composition of two principal food plants, heather and cotton-grass (Eriophorum spp.) across three British upland peatlands over ten years. We find that: 1) heather shoot nutrition significantly improved following management (mainly increasing Mn, P, N, Na, Zn, and, for burning only, Fe and K and decreasing Al) compared to no management, 2) management benefits were most pronounced post-burning, and often for longer than post-cutting, 3) impacts were primarily evident in heather shoots and nutrient levels generally realigned over nine years post-management, and 4) cotton-grass, especially flower heads, showed significantly increased Mn on burnt plots. These elemental benefits (Fe, N, Mn, P) are important for carbon uptake, egg formation (K, Zn), avian breeding success and grazing animals (P). This study highlights the value of long-term, holistic monitoring when assessing peatland management strategies.