Intra and inter-annual climatic conditions have stronger effect than grazing intensity on root growth of permanent grasslands

Abstract

Background and AimsUnderstanding how direct and indirect changes in climatic conditions, management, and species composition affect root production and root traits is of prime importance for grassland C sequestration service delivery.MethodsWe studied during two years the dynamics of root mass production with ingrowth-cores and annual above- and below-ground biomass (ANPP, BNPP) of upland fertile grasslands subjected for 10 years to a gradient of herbage utilization by grazing.ResultsWe observed strong seasonal root production across treatments in both a wet and a dry year but response to grazing intensity was hardly observed within growing seasons. In abandonment, spring and autumn peaks of root growth were delayed by about one month compared to cattle treatments, possibly due to later canopy green-up and lower soil temperature. BNPP was slightly lower in abandonment compared to cattle treatments only during the dry year, whereas this effect on ANPP was observed the wet year. In response to drought, the root- to-shoot biomass ratio declined in the abandonment but not in the cattle treatment, underlining higher resistance to drought of grazed grassland communities.ConclusionsRotational grazing pressure and climatic conditions variability had very limited effects on root growth seasonality although drought had stronger effects on BNPP than on ANPP.

Functional diversity buffers biomass production across variable rainfall conditions through different processes above‐ versus below‐ground

“…A developing consensus is that functional diversity, defined as the diversity of functional trait values within a community, promotes ecosystem functioning (Gagic et al, 2015; Tilman et al, 1997). While above‐ground plant trait research has been successful in predicting plant functions (Lavorel & Garnier, 2002) and identifying patterns of above‐ground diversity (Shipley et al, 2006), below‐ground trait research lags behind (but see Klumpp & Soussana, 2009; Picon‐Cochard et al, 2021). The key challenge is applying this trait‐based approach to understand how plant community change influences ecosystem functions, such as above‐and below‐ground biomass production, under changing environmental conditions.…”