@article{Lang_Betancur-Corredor_Russell_2023, title={Earthworms increase mineral soil nitrogen content – a meta-analysis}, volume={95}, url={https://soil-organisms.org/index.php/SO/article/view/308}, DOI={10.25674/so95iss1id308}, abstractNote={<p class="western" style="line-height: 200%; margin-bottom: 0cm;"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">Soil organisms and their interactions play a key role in various ecosystem processes and functions, such as the provision of nutrients. The main actors in nitrogen transformation processes are microorganisms, but earthworms affect these processes as their activity results in changes of the microhabitat and microbial community. Studies have shown that nitrogen content is higher in earthworm casts than in bulk soil, and that earthworm invasion affects soil mineral nitrogen. However, we still lack a quantitative synthesis of earthworm effects on soil nitrogen in bulk soil that integrates the influence of potential controlling factors (i.e., soil properties, climatic conditions and experimental parameters). Here, we investigated the impact of earthworms on soil ammonium (NH</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">4</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">+</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">), nitrate (NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">) and total mineral nitrogen (ammonium + nitrate, N</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">min</span></span></span></sub></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">) using meta-analytic techniques. Earthworms generally increased NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> (+ 88%) and N</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">min</span></span></span></sub></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> (+ 63%), but did not affect NH</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">4</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">+</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">. We assume that earthworms affect total mineral nitrogen mainly by their impact on NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">. Endogeic and epigeic earthworms significantly increased NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> and N</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">min</span></span></span></sub></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">, whereas no clear effect of anecic earthworms was found. This result is presumably caused by diverse effects of the different ecological groups on the microbial community composition. Our results for mixed ecological groups (i.e., anecic + endogeic earthworms) reveal potentially antagonistic effects of ecological groups. The impact of earthworm presence on NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> and N</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">min</span></span></span></sub></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> increased when experiments lasted longer than one week. </span></span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">The effect of earthworms on</span></span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> NH</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">4</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">+</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">, NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> or N</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">min</span></span></span></sub></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> was not influenced by </span></span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">e</span></span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">arthworm abundance and biomass, soil organic carbon, soil C/N ratio, litter C/N ratio, the initial amount of NH</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">4</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">+</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">, NO</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">3</span></span></span></sub></span><span style="color: #000000;"><sup><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">-</span></span></span></sup></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US"> or N</span></span></span></span><span style="color: #000000;"><sub><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">min</span></span></span></sub></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">, total soil nitrogen or temperature. </span></span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">However, as data availability or replication across factor categories was low for some of these moderators, the non-significant results should be interpreted with caution. Also, we could not investigate interactions among the controlling factors due to paucity of data. Our study thus reveals important knowledge gaps regarding earthworm effects on soil nitrogen. </span></span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="en-US">Overall, our results highlight the importance of earthworms for soil nitrogen cycling and strengthen the call for soil-functional models to incorporate soil faunal effects.</span></span></span></span></p>}, number={1}, journal={SOIL ORGANISMS}, author={Lang, Birgit and Betancur-Corredor, Bibiana and Russell, David J.}, year={2023}, month={Apr.}, pages={1–16} }