Additional carbon sequestration benefits of grassland diversity restoration

Abstract

Summary1. In Europe, grassland agriculture is one of the dominant land uses. A major aim of European agri-environment policy is the management of grassland for botanical diversity conservation and restoration, together with the delivery of ecosystem services including soil carbon (C) sequestration. 2. To test whether management for biodiversity restoration has additional benefits for soil C sequestration, we investigated C and nitrogen (N) accumulation rates in soil and C and N pools in vegetation in a long-term field experiment (16 years) in which fertilizer application and plant seeding were manipulated. In addition, the abundance of the legume Trifolium pratense was manipulated for the last 2 years. To unravel the mechanisms underlying changes in soil C and N pools, we also tested for effects of diversity restoration management on soil structure, ecosystem respiration and soil enzyme activities. 3. We show that the long-term biodiversity restoration practices increased soil C and N storage especially when these treatments were combined with the recent promotion of the legume Trifolium pratense, sequestering 317 g C and 35 g N m )2 year )1 in the most successful management treatment. These high rates of C and N accumulation were associated with reduced ecosystem respiration, increased soil organic matter content and improved soil structure. Cessation of fertilizer use, however, reduced the amount of C and N contained in vegetation. 4. Synthesis and applications. Our findings show that long-term diversity restoration practices can yield significant benefits for soil C storage when they are combined with increased abundance of a single, sub-ordinate legume species. Moreover, we show that these management practices deliver additional ecosystem benefits such as N storage in soil and improved soil structure.

Rapid transfer of photosynthetic carbon through the plant-soil system in differently managed species-rich grasslands

“…Instead of focusing on pre-defined functional groups, future studies could benefit from taking a trait-based approach, using measurable characteristics of the different components of communities (across trophic levels) rather than categorical groups, as has recently become the focus in biodiversity-ecosystem functioning research (De Deyn et al, 2008;Hillebrand and Matthiessen, 2009;Reiss et al, 2009). In contrast to our expectation, under the assumption of overall increased plant photosynthetic activity with fertilisation given higher productivity (De Deyn et al, 2011), we did not find effects of fertiliser application on the C uptake and transfer to microbes. However, our results are in line with the study of Hill et al (2007) where mineral N application also did not affect C assimilation rates in Lolium perenne, as opposed to the strong effect of elevated CO 2 levels.…”

“…In a long-term grassland restoration experiment Smith et al (2003Smith et al ( , 2008 showed that cessation of mineral fertiliser use and the seeding of target plant species increased plant species richness and the abundance of soil fungi, compared to soil bacteria. These restoration treatments also enhanced the rate of soil C and N accumulation (De Deyn et al, 2011), suggesting potential management impacts on short-term C fluxes through plants and soil biota.…”

“…Fertiliser addition was done yearly in early May (25 kg N and 12.5 kg P and K per ha) (Smith et al, 2003(Smith et al, , 2008. The in situ pulse-labelling was performed simultaneously in 12 plots, which correspond with the plots that did not receive seeding with Trifolium pratense in the study on soil C sequestration by De Deyn et al (2011). The identity and % cover of vascular plant species in the central 2 × 2 m of each plot was determined in June 2006 according to Stace (1991).…”

Plant diversity increases soil microbial activity and soil carbon storage

“…Although we cannot rule out that the proposed mechanisms are particularly pronounced at the field site of The Jena Experiment, the underlying relationships between plant diversity and soil carbon storage 17,24 , soil microbial biomass and activity 37,45,46 , and root biomass 24,47 have been reported in several independent experimental settings providing some evidence that the proposed links are of general significance. This leads us to reconsider the role of soil microorganisms as sources rather than sinks for slow-cycling organic matter.…”

“…The observed increase in carbon storage with plant diversity 17 therefore either reflects higher primary production 18,19 or longer persistence of plant-derived organic materials due to slower decomposition 10,16 . Increased plant residue inputs also provide more substrate for soil microorganisms, resulting in a more active and more abundant microbial community 20 .…”