Impact of tree plantations on the dynamics of soil aggregates in urban degraded lands in the dry tropics

Abstract

The impact of land-use change in an urban ecosystem on soil aggregate dynamics and soil carbon storage was studied through two annual cycles under five land uses.All the land uses namely: (1) natural mixed vegetation (NV) growing in a protected area; (2) grass fallow (GF); and tree plantations of (3) Cassia siamea (CP); (4) Jatropha curcas (JP); and (5) Tectona grandis (TP) were grown on urban degraded waste lands in a dry tropical region of India. Proportions of soil aggregate fractions, their stability, and soil carbon storage were analyzed at upper (00-15 cm), and lower (15-30 cm) soil depths during the rainy, winter, and summer seasons. Across all the land uses and at both the soil depths, the proportion of macroaggregate was highest during summer and lowest during the rainy season, whereas the reverse trend was observed for mesoaggregate. The annual mean proportion of macroaggregate decreased while meso-and microaggregates increased, with increasing soil depth across all the land uses. At the upper layer, the trends of macroaggregate, aggregate stability, and soil C storage were NV > CP > JP > TP > GF whereas at lower depth, the trend was NV > TP > CP > JP > GF. Across all the land uses in both the depths, soil C storage was strongly and positively correlated with annual mean fraction of soil macroaggregate. All tree plantations improved soil properties considerably as compared to GF at upper soil layer, yet TP reached near NV in these soil properties at lower depth. Soil aggregate fractions may be used as an index of carbon storage capacity in the urban ecosystems. K E Y W O R D S degraded land, soil aggregate fractions, soil C storage, tree plantation, urban land use change 1 | INTRODUCTION The 21st century often is referred as the Century of the Cities, as about 55% of the global population are already city dwellers. It is expected that by 2050 about 68% population may live in urban areas (UN DESA, 2019). Urbanization, an anthropogenically driven, land use change will have implications not only on social, economic, and political fronts but also on the structure, function, and services of ecosystem (Lal & Augustin, 2011; Richter et al., 2020). Understanding ecological consequences of the land use change is critical for maintaining resilience and sustainability of ecosystems at local, regional, and global scale in general and particularly for the tropics (Bustamante et al., 2016; Peng et al., 2019). Land use change caused due to urbanization is abundant in the tropics, where the cumulative impact of various factors including climate and poor soil management results in formation of degraded lands with reduced soil aggregate stability

Relationships between soil and microbial biomass properties and annual flux of nutrients in Central Himalaya forests, India

“…Among soil quality indicators, a small but very active part of soil organic matter—the soil microbial biomass (SMB) has been considered to be a sensitive soil quality indicator particularly for land degradation, and can be used to predict short‐ and long‐term soil quality trends (Mariani et al, 2006; Saviozzi et al, 2002; Tarrasón et al, 2010). SMB plays an important role in indicating soil fertility and is easily altered by changes in the quantity and biochemical composition of forest litter (Hassett & Zak, 2005; Singh et al, 2021). Soil physicochemical attributes significantly alter SMB activity and soil physicochemical properties are regulated by vegetation cover type (Jangid et al, 2011).…”