Abstract
AbstractPeatlands are recognized as important carbon stores; despite this, many have been drained for agricultural improvement. Drainage has been shown to lower water tables and alter vegetation composition, modifying primary productivity and decomposition, potentially initiating peat loss. To quantify CO2 fluxes across whole landscapes, it is vital to understand how vegetation composition and CO2 fluxes vary spatially in response to the pattern of drainage features. However, Molinia caerulea‐dominated peatlands are poorly understood despite their widespread extent.Photosynthesis (PG600) and ecosystem respiration (REco) were modelled (12 °C, 600 µmol photons m−2 s−1, greenness excess index of 60) using empirically derived parameters based on closed‐chamber measurements collected over a growing season. Partitioned below‐ground fluxes were also collected. Plots were arranged ⅛, ¼ and ½ the distance between adjacent ditches in two catchments located in Exmoor National Park, southwest England.Water table depths were deepest closest to the ditch and non‐significantly (p = 0·197) shallower further away. Non‐Molinia species coverage and the Simpson diversity index significantly decreased with water table depth (p < 0·024) and increased non‐significantly (p < 0·083) away from the ditch. No CO2 fluxes showed significant spatial distribution in response to drainage ditches, arguably due to insignificant spatial distribution of water tables and vegetation composition. Whilst REco showed no significant spatial variation, PG600 varied significantly between sites (p = 0·012), thereby controlling the spatial distribution of net ecosystem exchange between sites. As PG600 significantly co‐varied with water table depths (p = 0·034), determining the spatial distribution of water table depths may enable CO2 fluxes to be estimated across M. caerulea‐dominated landscapes. © 2015 The Authors. Ecohydrology published by John Wiley & Sons, Ltd.
Highlights
A small imbalance between primary productivity and decay within peatlands has led to the accumulation of large carbon stores (Yu et al, 2010)
Annual net primary productivity (ANPP), percentage cover of leaf litter and Molinia were lowest at 1⁄4 distance (Figure 2g, h and i), but showed no significant differences between proportional distances from the ditch (Table III) or from the absolute distances from the ditch (Table V)
Across all locations (n = 36) where the average water table depth was closer to the surface, more non-Molinia species coverage, increased vegetation diversity and reduced PG600 occurred, indicating wetter conditions may be sub-optimum for M. caerulea
Summary
A small imbalance between primary productivity and decay within peatlands has led to the accumulation of large carbon stores (Yu et al, 2010). Drainage ditches are frequently the main spatial feature within managed blanket bogs They have been shown to lower the mean water table (Coulson et al, 1990, Wilson et al, 2010, Holden et al, 2011), which in turn reduces species richness (Bellamy et al, 2012), affecting species dependent on high water levels including Sphagnum. Using a combination of gas flux chambers and soil collars enables the measurement of both ecosystem and partitioned below-ground fluxes at discrete distances from drainage features. Such monitoring facilitates understanding of the variables driving spatial variation in CO2 fluxes assisting upscaling (Laine et al, 2006)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
