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Nielsen, U. N.

Publications and source records attributed to Nielsen, U. N..

2 recordsLinked to original sources

Global monitoring of soil animal communities using a common methodology

Here we introduce the Soil BON Foodweb Team, a cross-continental collaborative network that aims to monitor soil animal communities and food webs using consistent methodology at a global scale. Soil animals support vital soil processes via soil structure modification, direct consumption of dead organic matter, and interactions with microbial and plant communities. Soil animal effects on ecosystem functions have been demonstrated by correlative analyses as well as in laboratory and field experiments, but these studies typically focus on selected animal groups or species at one or few sites with limited variation in environmental conditions. The lack of comprehensive harmonised large-scale soil animal community data including microfauna, mesofauna, and macrofauna, in conjunction with related soil functions, limits our understanding of biological interactions in soil communities and how these interactions affect ecosystem functioning. To provide such data, the Soil BON Foodweb Team invites researchers worldwide to use a common methodology to address six long-term goals: (1) to collect globally representative harmonised data on soil micro-, meso-, and macrofauna communities; (2) to describe key environmental drivers of soil animal communities and food webs; (3) to assess the efficiency of conservation approaches for the protection of soil animal communities; (4) to describe soil food webs and their association with soil functioning globally; (5) to establish a global research network for soil biodiversity monitoring and collaborative projects in related topics; (6) to reinforce local collaboration networks and expertise and support capacity building for soil animal research around the world. In this paper, we describe the vision of the global research network and the common sampling protocol to assess soil animal communities and advocate for the use of standard methodologies across observational and experimental soil animal studies. We will use this protocol to conduct soil animal assessments and reconstruct soil food webs on the sites included in the global soil biodiversity monitoring network, Soil BON, allowing us to assess linkages among soil biodiversity, vegetation, soil physico-chemical properties, and ecosystem functions. In the present paper, we call for researchers especially from countries and ecoregions that remain underrepresented in the majority of soil biodiversity assessments to join us. Together we will be able to provide science-based evidence to support soil biodiversity conservation and functioning of terrestrial ecosystems.

ecology↗

The fate of carbon in a mature forest under carbon dioxide enrichment

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1,2,3,4,5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. While evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3,4,5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7,8,9,10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving an open question about the fate of additional carbon fixed under eCO24, 5, 7,8,9,10,11. Here, using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responds to four years of eCO2 exposure. We show that, although the eCO2 treatment of ambient +150 ppm (+38%) induced a 12% (+247 gCm-2yr-1) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone contributing [~]50% of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on CO2 fertilization as a driver of increased carbon sinks in standing forests and afforestation projects.

ecology↗