Assessment of the Climate Variability Effects on Planted Forests (Case study: Dry lands, Semnan Province).

Document Type : Research Paper

Authors

Department of Reclamation of Arid and Mountainous Regions, Faculty of Natural Resources, University of Tehran, Karaj, Iran.

Abstract

Afforestation of wind erosion hotspots using drought-tolerant species such as Haloxylon spp. remains a central strategy in mitigating desertification and stabilizing mobile dunes in Iran's arid regions. Despite these efforts, the long-term sustainability of such ecosystems is becoming increasingly uncertain due to the combined pressures of climate variability and anthropogenic disturbances. This study evaluated the ecological resilience of planted desertland forests in Semnan Province by quantifying the relative contributions of climatic and human influences. A time series of Landsat 8 imagery from 2013 to 2022 was used to derive the Forest Canopy Density (FCD) model. Vegetation dynamics were statistically correlated with drought patterns, as measured by the Standardized Precipitation–Evapotranspiration Index (SPEI), using Pearson correlation analysis. The findings revealed that the FCD maintained a consistent range between 44.9% and 55.8%, indicating a moderate and stable vegetation cover characteristic of established Haloxylon stands in arid environments. The correlation analysis revealed a weak and statistically non-significant association (R = 0.21, p > 0.05, n = 10) between FCD and SPEI at a 9-month lag. This lack of significant climatic coupling highlights that precipitation variability alone explains a negligible portion of vegetation dynamics, strongly pointing to the dominance of non-climatic drivers such as anthropogenic disturbances and groundwater dependency. Furthermore, based on the Residual Trend Analysis (RESTREND), the Mann-Kendall trend test on residuals revealed no statistically significant anthropogenic degradation or restoration trends across the study area (Z-values ranging from -1.40 to +1.40). This indicates that human pressures likely remained constant rather than intensified during the 2013–2022 period, resulting in a fragile status quo. The compounded effects of prolonged droughts and unsustainable water resources management thus shape the sustainability of these afforested systems. The adoption of integrated, climate-informed, and human-responsive land management approaches is strongly recommended to safeguard these critical desert ecosystems.

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