Effects of long-term vegetation restoration on soil aggregate and aggregate-associated nutrient stoichiometry of desertified grassland on the eastern Qinghai–Tibet Plateau

Abstract

In the context of restoring desertified grassland vegetation, elucidating the intricate composition and stability of soil aggregates, coupled with the essential stoichiometric attributes of carbon (C), nitrogen (N) and phosphorus (P), is vital for assessing the intricate soil biogeochemical processes and ecosystem services. However, previous research has predominantly focused on the characteristics of grassland vegetation communities, soil physicochemical factors, and their interrelationships, with limited studies on the properties of C, N, and P stoichiometry. This study examined four desertified grasslands with varying restoration periods (10a, 14a, 20a, and 40a) to assess the long-term restoration effects on soil aggregates and aggregate-associated nutrient stoichiometry in eastern Qinghai–Tibet Plateau, China. The results showed that as the restoration period progressed, plant diversity and vegetation coverage increased accordingly. The contents of soil organic C (SOC), total N (TN), and total P (TP) in soil aggregates of various depths and sizes, especially in the macroaggregates, gradually increased and peaked after 20 years of restoration. Conversely, the contents of microaggregates and clay-silt fractions generally exhibited a downward trend. After two decades, the desertified grassland's soil aggregates achieved an optimal level of stability. Furthermore, the vegetation restoration resulted in notable changes in soil aggregate-associated C, N, and P stoichiometric of desertified grassland. A marked strong correlation was observed between the composition and stability of soil aggregates and the stoichiometric characteristics of these essential nutrients, with the macroaggregate mass ratio showing a positive relationship with aggregate stability. Our findings have significant implications for ecological restoration strategies, aiming to promote long-term soil health and productivity in degraded landscapes.