Vegetation–Soil System Characteristics and Stability Assessment of Poplar Plantations across Degradation Gradients in the Heilaigou Watershed

DOI: https://doi.org/10.62517/jlsa.202607301

Author(s)

Henglu Miao1, Qi Ren2, Yuefeng Guo2,3,4,*, Yang Song2, Min Han2, Yonghan Wu2

Affiliation(s)

1Institute of Water Resources Science of Pastoral Areas, Ministry of Water Resources, Hohhot, Inner Mongolia, China 2College of Desert Control Science and Engineering, Inner Mongolia Agricultural University, Hohhot, Inner Mongolia, China 3State Key Laboratory of Water Engineering Ecology and Environment in Arid Area, Inner Mongolia Agricultural University, Hohhot, Inner Mongolia, China 4Inner Mongolia Dalate Desert Ecosystem Observation and Research Station, Ordos, Inner Mongolia, China *Corresponding Author

Abstract

Clearing up the interactive nature of the vegetation-soil system during consecutive degradation of the Populus simonii plantation. Poplar plantations in the Engebei Demonstration Area were used as model systems whereby stands were divided into four categories of degradation depending on the amount of dieback observed; non-degraded (<10%), mildly degraded (10-20%), moderately degraded (20-60) and severely degraded (>60).The vegetation community attributes, soil physicochemical properties and fine-root functional traits of all grades have been systematically measured. ANOVA, principal component analysis (PCA) and entropy-weighted TOPSIS were used to analyze the data and build a composite stability assessment. As the degradation increased, the height of the trees, the diameter of the trees at the breast height (DBH) and the crown area decreased by 24.6, 59.9 and 67.7 percent, respectively, whereas the rate of dieback increased by 7.80-65.30 percent. The shrub-herb layer cover and its biomass were represented by a unimodal trend of rise-then-fall with maximum values reached in the stage of moderate degradation - as an under-story compensation response. The peaks of both SRL and SRA shifted upwards in the soil layer of 80-100 cm to that of 20-60 cm, this indicates that the approach was changed to use deeper water resources than to engage in opportunistic rooting behavior in less deep horizons. The soil sand content was over 88 per cent in heavily degraded stands; total nitrogen (TN) dropped by half, that is, to 0.12 g/kg, and the C/N ratio increased twofold, reaching 42. Total N, AP, C/N, EC, and SWC were selected to be the main driving factors. The stability ranking derived by both PCA and TOPSIS analyses was the same: non-degraded > mildly degraded > moderately degraded > severely degraded. It is also important that the transition between minor and intermediate damage is an inflection point, or an instable state change, which marks the final chance to fix it. The most common deterioration process is the water-salinity-nutrient coupling link. The moderate degradation stage is the final operational opportunity to act on the remediation. Even though a tiered control system is recommended: prevention of unhealthy state of intact stands and silvicultural thinning of poorly lit stands, restorative measures in lightly degraded areas, and complete refurbishment of heavily degraded stands.

Keywords

Poplar Plantation; Degradation Gradient; Vegetation–Soil System; Fine-Root Functional Traits; Principal Component Analysis; Stability Assessment

References

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