Effect of spacing on the growth, biomass production and carbon stocks of sandalwood (Santalum album L.) trees under farm conditions in Western Maharashtra, India

In recent years, farmers have started growing Santalum album L. in states of India like Maharashtra. This has brought a major change to local agroforestry. In this research we wanted to understand how three different tree spacings (3.05 x 3.05 m, 3.66 x 3.66 m and 3.66 x 4.57 m) alter actual tree growth and carbon (C) storage in Western Maharashtra. We made sure to track the exact land conditions across our 24 study sites. The soil types were neutral to moderately alkaline Vertic and Typic Haplustepts with a pH of 7.1–8.1 and the 10 year local rainfall stayed between 112.03 and 233.45 mm. Field data were gathered on standard traits like tree height, thickness (DBH) and wood volume for two age groups (1–5 years and 6–10 years). To find the final biomass weights, we applied the standard equations along with the scaling methods. All collected datasets were carefully checked using a two-way analysis of variance (ANOVA). The field records showed a very clear link between planting density and growth (P < 0.001). Young trees (1–5 years) grew quite easily because they had plenty of open space. In this young group, the widest rows of 3.66 x 4.57 m gave the best average DBH of 0.09 m. These wide plots recorded a total biomass of 1.33 Mg ha-1 and a CO2 mitigation value of 2.44 Mg ha-1. But things took a tough turn as the trees hit the 6–10 years mature stage. Heavy crowding on these dry Vertic soils started blocking growth in the tightest 3.05 x 3.05 m layout. This resource stress capped the mature DBH at just 0.07 m and dragged the stand biomass down to 2.09 Mg ha-1. In comparison, the medium spacing of 3.66 x 3.66 m hit the perfect sweet spot by keeping individual trees healthy while protecting the farm's overall yield. In the mature stage, this intermediate spacing hit a top average height of 4.79 m, the best DBH of 0.12 m and a great stand volume of 40.43 m3 ha-1. Due to these superior dimensions, the medium plots maximised mature biomass at 4.30 Mg ha-1 and kept a peak net C stock of 2.15 Mg C ha-1. This adds up to a solid climate benefit of 7.89 Mg CO2 ha-1. Since the interaction between age and spacing was non-significant, we can safely say this medium setup stays highly stable over time. In short, these real-world numbers give a reliable roadmap for connecting private sandalwood farming with global climate programs like reducing emissions from deforestation and forest degradation (REDD+).