Abstract
Stock farming plays an important role in the agriculture of alpine regions although deleterious effects on the soils are most pronounced here. We investigated the effects of cattle trampling on soil physical, chemical and microbial properties in a Swiss sub-alpine pasture. About 10% of the study site was bare of vegetation as a result of repeated cattle trampling and the bulk density of these bare steps was 20% higher than of the soils unaffected by trampling. In the upper 25 cm, soil organic carbon (SOC) concentrations and total SOC stocks were 35% and 20% respectively lower than on the vegetated slope. As compared with the vegetated slope, topsoils of the bare steps featured narrower C:N-ratios and were more enriched in the 15N isotope, with typical values of deeper soil layers. This indicates that bare soils primarily evolved by erosion and not by a compaction, which might, together with the reduced litter input, explain the lower SOC contents. The abundances of soil microbes, estimated by the concentrations of phospholipid fatty acid (PLFA), were 30% smaller in the bare soils than in the vegetated areas. This depletion was most pronounced for fungi as expressed in the lower concentrations of the fatty acid 18:26.9 (45%) and ergosterol (50%). The lower fungal abundance very likely has negative consequences for the stability of the bare soils, since fungi play an important role in the formation of soil aggregates. In summary, our results show that cattle trampling decreases soil carbon storage and alters soil microbial community structure. © 2011 Elsevier B.V. All rights reserved.
Generated Summary
This research investigates the effects of cattle trampling on soil properties and microbial communities in a Swiss sub-alpine pasture. The study employs a field experiment, comparing soil characteristics in bare steps, vegetated shoulders, and unaffected slopes. Soil samples were analyzed for physical, chemical, and microbial properties, including soil organic carbon (SOC), total nitrogen (TN), and phospholipid fatty acids (PLFA). Stable isotope analysis of nitrogen was also conducted to understand soil formation processes. The study aimed to elucidate the processes leading to the formation of steps in steep alpine grasslands and to quantify the effects of cattle trampling on soil characteristics, using a combination of field measurements and laboratory analyses. The research provides insights into the impact of livestock grazing on soil health and the dynamics of soil microbial communities in alpine ecosystems.
Key Findings & Statistics
- Bare steps covered 10% of the study area, vegetated shoulders 33%, and unaffected slopes 57%.
- Bulk density in bare steps was 20% higher than in unaffected soils.
- In bare steps, SOC and TN concentrations were 35% and 20% lower, respectively, compared to vegetated areas.
- Soil organic carbon (SOC) concentrations in bare steps were 35% lower than in vegetated areas.
- Total SOC stocks were 20% lower in bare steps compared to vegetated areas.
- The uppermost 25 cm of bare steps showed a 35% and 20% reduction in soil organic carbon (SOC) and total nitrogen (TN) respectively, compared to vegetated areas.
- Soil pH values ranged from 4.7 to 5.3, with slightly higher values in bare steps.
- The soil in bare steps contained about 6 kg m-2 organic carbon and 0.69 kg m-2 nitrogen, while the unaffected slopes had 7.6 kg m-2 organic carbon and 0.74 kg m-2 nitrogen.
- Soil respiration in bare steps was about 40% lower than in vegetated areas.
- The fungal biomarker ergosterol was about 50% lower in the bare steps compared to vegetated areas.
- PLFA analysis revealed a 28% lower bacterial and 45% lower fungal abundance in bare steps compared to vegetated areas.
- Cattle tracks had an average track width of 72 cm ± 9.67 cm.
- On the tracks, the bare steps covered 0.21±0.01 ha, and the vegetated shoulders covered 0.66±0.01 ha.
- The study area included approximately 0.87±0.11 ha of cattle tracks.
- In the uppermost 25 cm of the bare steps, the study showed 35% and 20% reductions in SOC and TN concentrations, respectively.
- The bare steps contained only 6 kg m⁻² SOC and 0.69 kg m⁻² TN within 0-25 cm depth.
- The study area covered 2 ha.
- Cattle tracks made a contribution of 0.87±0.11 ha to the study area (2 ha), while 1.13±0.11 ha were unaffected by the trampling.
Other Important Findings
- The study suggests that the formation of bare steps is primarily due to erosion rather than soil compaction.
- Cattle trampling leads to a decrease in soil carbon storage and alters the structure of soil microbial communities.
- Bare steps showed narrower C:N ratios and were more enriched in the 15N isotope compared to vegetated areas.
- Fungal abundance, particularly the fatty acid 18:26.9, was significantly reduced in the bare steps.
- The decrease in fungal abundance may have negative consequences for the stability of the bare soils, as fungi play an important role in the formation of soil aggregates.
- Trampling significantly reduced soil respiration rates.
- Soils in bare steps exhibited lower soil porosity and higher bulk density compared to vegetated areas.
- The proportion of Gram-negative bacteria did not change significantly, whereas a decrease in fungal abundance was observed.
Limitations Noted in the Document
- The study does not include ungrazed control plots, limiting the ability to fully isolate the impacts of cattle trampling.
- The study focuses on a single sub-alpine pasture, which limits the generalizability of the findings to other ecosystems.
- The study acknowledges that the bare steps have been formed through both erosion and compaction, but does not fully quantify the relative contribution of each process.
- The study focuses on a rather large area.
- The specific mechanisms by which trampling affects the soil microbial communities were not fully elucidated.
- The study notes that the results are site-specific, and cannot be generalized.
- The absence of ungrazed control plots in the study represents a significant limitation.
Conclusion
The research underscores the significant impact of cattle trampling on the physical, chemical, and microbial properties of soils in sub-alpine pastures. The study reveals that trampling-induced erosion leads to a decrease in soil carbon storage and alters the structure of soil microbial communities. The findings demonstrate that cattle trampling decreases soil carbon storage and alters the soil microbial community structure. This is reflected in lower soil organic carbon (SOC) concentrations, total SOC stocks, and reduced microbial biomass, particularly fungi, in the bare steps. The observed shift in the microbial community, with lower fungal abundance, indicates potential consequences for soil aggregate stability. The study highlights the complex interplay between trampling, erosion, and microbial activity in alpine grassland ecosystems. The results show that cattle trampling decreases soil carbon storage and alters soil microbial community structure. The reduction in soil organic matter and the shift in microbial communities suggest a degradation of soil health in trampled areas. The study emphasizes that trampling affects soil carbon storage and microbial community structure in alpine pastures. These findings have implications for understanding and managing the impacts of livestock grazing on soil health and ecosystem function in alpine regions. Further research is needed to fully understand the fate of the eroded organic material and the long-term consequences of these changes on ecosystem services.