Cropping history trumps fallow duration in long‐term soil and vegetation dynamics of shifting cultivation systems
Bibliographic record
Abstract
In the study of shifting cultivation systems, fallow duration is seen as the key determinant of vegetation and soil dynamics: long fallows renew soil fertility, biomass, and biodiversity. However, long fallow systems are increasingly replaced around the world with short-medium fallow systems, and awareness is growing of the need to look across multiple (not just single) crop-fallow cycles to accurately understand observed soil and vegetation patterns. In a study from Peru that builds on 50+ years of field-level land-use histories, we found that, over multiple crop-fallow cycles, farmers' cropping practices mattered more than fallow duration for biodiversity and soil fertility. After initial clearing of primary forest, a precipitous decline occurred in tree species richness of fallows (>50%) with gradual but continued loss thereafter (~0.5 species/yr), which resulted in shifts in species composition over time. For soils, the decline in fertility was more gradual with each additional cycle of cropping resulting in lowered soil organic matter, available phosphorus, and exchangeable sodium levels, even in fields with long fallow durations. In the most intensively used sites, soils experienced a 16% decline of soil organic matter over 4+ cycles. In contrast to previous studies, biomass accumulation and carbon stocks were not related to cropping history or to the number and duration of cycles observed. This suggests that biodiversity-soils-biomass dynamics may not necessarily "move together" in these systems. These results point to the importance of the number of crop-fallow cycles over fallow duration in driving soil fertility and vegetation dynamics under shifting cultivation in the Peruvian Amazon. Overtime shifting cultivation may erode soil fertility and biodiversity levels even if long fallows persist. As the decline in soils appears slow, it may be possible to address this effect with the use of amendments, however biodiversity declines and species compositional changes may be much harder to reverse.
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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".