# Land-use shapes the composition and stability of soil water-stable aggregates in a plateau agro-pastoral ecotone

## TL;DR

This study shows how different land uses affect soil structure and stability in a region of the Tibetan Plateau.

## Contribution

The study provides new comparative data on soil aggregate composition and stability across multiple land-use types and soil depths in a Tibetan Plateau ecotone.

## Key findings

- Silt and clay particles were the most common soil aggregate fraction across all land-use types.
- Planted forests and grasslands had significantly more stable soil aggregates than croplands and orchards in the top soil layer.
- Soil organic matter content is strongly linked to aggregate stability, highlighting its importance in soil structure.

## Abstract

The northeastern Tibetan Plateau is a typical agro-pastoral ecotone that experiences frequent land-use changes. Maintaining stable soil aggregates in this region is key to protecting the environment and supporting food production on the Tibetan Plateau. Nevertheless, comparative data on soil aggregate composition and stability across diverse land-use types and soil depths in this region are currently limited.

Herein, soil samples from 0–20 cm and 20–40 cm depths were gathered at 52 sites spanning four dominant land-use types in the northeastern Tibetan Plateau: grassland (GL), cropland (CL), orchard (OC), and planted forest (PF). The composition and stability of soil aggregates were assessed using the wet sieving method.

The results exhibited that silt and clay particles (SC, <0.053 mm) were the predominant aggregate fraction across all land-use types, followed by microaggregates (MIA, 0.053–0.25 mm), while small macroaggregates (SMA, 0.25–2 mm) and large macroaggregates (LMA, >2 mm) had relatively low mass proportions. Aggregate stability in the 0–20 cm layer ranked PF > GL > CL > OC, with PF and GL significantly more stable than OC. In the 20–40 cm layer, the highest aggregate stability was found in GL. Except for PF, aggregate stability varied little between different soil layers for other land-use types. Aggregate stability is positively associated with the contents of soil organic carbon, total nitrogen, and alkali-hydrolyzable nitrogen, underscoring the critical role of soil organic matter in regulating soil aggregation.

The findings suggest that land-use type is a key determinant of soil structure in the northeastern Tibetan Plateau.