Association between Soil Fertility and Growth Performance of Planted Shorea macrophylla (de Vriese) after Enrichment Planting at Rehabilitation Sites of Sampadi Forest Reserve, Sarawak, Malaysia

Table 3

Factor loadings of surface and subsurface soil physicochemical properties, principal component analysis (PCA), and results of PCA of the rehabilitated forest.

	Variables analyzed
	pH (H2O), SOM, Total N, CEC, Exch. Ca, Exch. Mg, Exch. K, Exch. Al, Available P, clay, silt, sand contents, and bulk density
	Value	PC1	PC2	PC3
Surface soils (0–10 cm)
Contribution ratio (%)		34.4	29.2	12.7
Variables with a high positive factor loading (>0.7)		Exch. Al, Available P, and silt	Total N, clay, and SOM	ND
Variables with a high negative factor loading (>0.7)		pH (H2O) and sand	Bulk density	ND
Contribution name of PC axis		Available phosphorus, soil acidity, and soil texture	Soil organic matter constituent
Subsurface soils (30–40 cm)
Contribution ratio (%)		34.4	29.3	10.3
Variables with a high positive factor loading (>0.7)		Exch. Al and silt	Total N, Exch. K, clay, and SOM	ND
Variables with a high negative factor loading (>0.7)		pH (H2O), sand, and bulk density	ND	Exch. Ca
Contribution name of PC axis		Soil acidity and soil texture	Cation retention capacity, soil organic matter constituent	Available nutrient

(+) = factor loading with a positive value; (−) = factor loading with a negative value; and ND = not determined. SOM = soil organic matter, Total N = total nitrogen, Exch. Ca, Mg, K, and Al = exchangeable Ca, Mg, K, and Al, clay, silt, and sand = percentage of clay, silt, and sand.