, Volume 282, Issue 1-2, pp 281-289

Partitioning of Respiration in an Intensively Managed Grassland

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Abstract

Total (R TOT) and heterotrophic (R H) respiration were measured in an intensively managed perennial ryegrass (Lolium perenne L.) grassland. The overall aim of the study was to partition R TOT into R H and autotrophic respiration (R A). This was achieved as follows: (1) analyse the effect of air temperature, soil moisture content and leaf area index on R TOT and the influence of soil temperature and soil moisture content on R H; (2) combine these effects into separate empirical models for R TOT and R H and; (3) use these models to determine temporal trends in R TOT and R H and to assess the relative contribution of R H and R A to R TOT. CO2 fluxes were measured using a vented and thermostatically controlled perspex chamber in conjunction with a portable infrared gas analyser. R TOT was measured in plots with grass and R H in plots with bare soil. R TOT was related to air temperature and R H to soil temperature using exponential relationships. Both R TOT and R H were related to soil moisture content using lognormal relationships. R TOT was related to leaf area index using a linear relationship. These relationships were combined to produce statistical response functions that explained 87% and 84% of the variation in R TOT and R H, respectively. These relationships were combined with meteorological and leaf area index data to reconstruct daily and seasonal fluxes. R TOT values in wintertime were ~4 g C m−2 day−1 increasing to ~10 g C m−2 day−1 in summertime when temperatures and leaf area index were higher and soils were drier. R H has a similar seasonal trend to R TOT but was consistently lower. Wintertime values were ~2 g C m−2 day−1 and increased to ~5 g C m−2 day−1 in summertime. Before day of year 143, and after day of year 259 R H and R A represented 62% and 38% of R TOT, respectively. In the period between these days R H and R A both accounted for 50% of R TOT. In total during 2004 R TOT, R H and R A were 2.34, 1.31 and 1.03 kg C m−2, respectively.