Hydrogen cyanide, a key plant defense, as a potential driver of root-associated nematode communities along urbanization gradients
Bibliographic record
Abstract
Introduction Plant chemical defenses can influence the distribution, community composition, and abundance of soil biota. Urbanization plays a key role in shaping soil biotic communities either directly through changes in soil properties or indirectly via changes in plant characteristics such as defense traits. The effects of urbanization and plant defenses on the abundance and structure of aboveground plant-associated communities have been studied, yet their effects on belowground root-associated communities are poorly understood. Methods Here we sampled white clover ( Trifolium repens L.) leaves and roots along urban–rural gradients in the cities of Antwerp and Ghent, Belgium. We measured production of hydrogen cyanide (HCN) in leaves, a known defense trait against herbivores, and abundances of different feeding guilds of nematodes associated with the roots. Results We found that HCN production decreased with increasing levels of urbanization in both cities. Urbanization was significantly correlated with shifts in root-associated nematode community structure in Antwerp but not in Ghent. Responses of nematode feeding guilds and trophic groups to urbanization were highly dependent on the clovers’ HCN production, especially in Ghent. Changes in nematode channel ratio in Antwerp indicated that urban root-associated nematode communities of white clover were more strongly dominated by fungivorous nematodes. Discussion Our results demonstrate that urbanization is driving changes in a plant phenotypic trait and in the community structure of root-associated nematodes, as well as that both changes interact. Plant defense mechanisms could thus help elucidate the effects of urbanization on root-associated biota communities. As strong differences existed between the two studied cities, the particular properties of cities should be taken into account to better understand the direction and strength of phenotypic trait changes driven by urbanization.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".