Plant–soil interrelationship in subtropical forests of Garhwal Himalaya, India

Soils have a significant role in the formation and heterogeneity of habitats and thus consequently cause changes in vegetation structure and plant diversity. In this paper we evaluated variation in species distribution/association, diversity and forest structure in context to the soil physicochemical properties, addressing ten subtropical forests of Garhwal Himalaya, India. The sample plots in each forest type were laid out using a stratified random approach to calculate the vegetation metrics (density, diversity, total basal cover (TBC), importance value). Soil samples were taken from three different depths, viz., (i) 0–10 cm, (ii) 11–30 cm and (iii) 31–60 cm to analyse the soil metrics [(texture, moisture, water holding capacity, pH, soil organic carbon (hereafter SOC), nitrogen, phosphorus (hereafter P), potassium (hereafter K)]. The tree density and TBC were significantly varied and ranged from 300 ± 11.55 to 840 ± 15.55 trees ha−1 and 12.55 ± 4.62 to 36.23 ± 5.77 m2 ha−1, respectively. The soil was sandy loam to clay loam and varies from acidic to alkaline (indicated by the pH), which has shown a significant-negative correlation (r =  − 0.724) with availability of P. The pH was also indentified as a factor to change the amount of P and K in the soil. The diameter class distribution patterns in most of the forests have revealed a positive skewed curve. The principal component analysis has revealed that sand, pH, SOC and bulk density were the main variables affecting the distribution of vegetation in the study area. However, no direct relationships were recorded between tree diversity and density (Adj R2 =  − 0.1116, P = 0.7637), shrub density and diversity (Adj R2 = 0.1121, P = 0.1820). On the other hand, SOC was significantly correlated with tree density (Adj R2 = 0.5747, P = 0.0067) but not correlated with shrub density (Adj R2 = 0.0033, P = 0.3535). The elevation was also insignificantly correlated with the diversity and density metrics. The results have revealed that specific soil properties were major deciding factor for species association, distribution and subsequently shaping forest structure in foothill regions of the Himalaya.