Influence of soil moisture and nutrient gradient on growth and biomass production of Calligonum polygonoides in Indian desert affected by surface vegetation

A field study was carried out on growth and biomass production of Calligonum polygonoides (L.) in different habitats to determine competitive interaction of Dactyloctenium sindicum grass for natural soil resources. Bare dune (BD), bare dune plantation (BDP), semistabilized dune plantation with D. sindicum (SDP), flatland without vegetation (FW), flatland with D. sindicum grass (FG) and flatland plantation with D. sindicum (FGP) were the habitats identified on the basis of micro-topography, presence of D. sindicum grass and plantation. Growth and biomass production of C. polygonoides were observed in relation to changes in biomass from surface vegetation, soil water content and nutrients. D. sindicum grass density and biomass were significantly (P<0.01) high in FG in 1998 whereas, in 1999 and 2000, FGP produced greater biomass. Soil organic matter, NH4–N, NO3–N, PO4–P and K were comparatively greater in the habitats with D. sindicum in 1996. All the nutrients increased in 2000 except NO3–N and the improvement was more in plantation. High (P<0.01) soil water content in FW and BD suggests that D. sindicum had extracted and utilized soil water more efficiently through its extensive root system in the remaining habitats. Soil water content increased in winter and coincided with plant senescence. Plant growth and biomass productions were significantly (P<0.05) less and grass production was greater in FGP. Contrasting result was obtained in BDP habitat in absence of D. sindicum. Difference in soil water content and nutrients seems to be the main cause for productivity differences of C. polygonoides. Lesser plant growth in FGP and SDP habitats was attributed to the competitive effect of D. sindicum grass, which seemed to have a stronger competitive effect on resource utilization. The differences in growth and biomass production accounted for the variation in D. sindicum grass density and root biomass, which was negatively correlated with growth increments and with soil water. The results indicate that surface vegetation affects the productivity of C. polygonoide altering availability of soil resources. Therefore, proper management to ensure water availability will be beneficial to enhance the productivity and the population of this species under afforestation programme.