Spatial and temporal patterns of root distribution in developing stands of four woody crop species grown with drip irrigation and fertilization.

Abstract In forest trees, roots mediate such significant carbon fluxes as primary production and soil C02 efflux. Despite the central role of roots in these critical processes, information on root distribution during stand establishment is limited, yet must be described to accurately predict how various forest types, which are growing with a range of resource limitations, might respond to environmental change. This study reports root length density and biomass development in young stands of eastern cottonwood (Populus deltoidies Bartr.) and American sycamore (Platanus occidentalis L.) that have narrow, high resource site requirements, and compares them with sweetgum (Liquidambar styraczj7ua L.) and loblolly pine (Pinus taeda L.), which have more robust site requirements. Fine roots (5 mm) were sampled to determine spatial distribu-tion in response to fertilizer and irrigation treatments delivered through drip irrigation tubes. Root length density and biomass were predominately controlled by stand development, depth and proximity to drip tubes. After accounting for this spatial and temporal variation, there was a significant increase in RLD with fertilization and irrigation for all genotypes. The response to fertilization was greater than that of irrigation. Both fine and coarse roots responded positively to resources delivered through the drip tube, indicating a wholeroot- system response to resource enrichment and not just a feeder root response. The plastic response to drip tube water and nutrient enrichment demonstmte the capability of root systems to respond to supply heterogeneity by increasing acquisition surface. Fineroot biomass, root density and specific root length were greater for broadleaved species than pine. Roots of all genotypes explored the rooting volume within 2 years, but this occurred faster and to higher root length densities in broadleaved species, indicating they had greater initial opportunity for resource acquisition than pine. Sweetgum's root characteristics and its response to resource availability were similar to the other broadleaved species, despite its hnctional resemblance to pine regarding robust site requirements. It was concluded that genotypes, irrigation arid fertilization significantly influenced tree root system development, which varied spatially in response to resource-supply heterogeneity created by dnp tubes. Knowledge of spatial and temporal patterns of root distribution in these stands will be used to interpret nutrient acquisition and soil respiration measurements

Combined effects of partial rootzone drying and patchy fertilizer placement on nutrient acquisition and growth of oilseed rape (Brassica napus)

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Contrasting root behaviour in two grass species: A test of functionality in dynamic heterogeneous conditions

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Root allocation in metal-rich patch by Thlaspi caerulescens from normal and metalliferous soil: new insights into the rhizobox approach

We compared root responses to spatial heterogeneity of Zn and Ni in Thlaspi caerulescens J. and C. Presl from normal (NM plants) and metalliferous soil (M plants). We investigated whether the strong metal accumulation capacity of NM plants (compared to M plants) was related to a greater capacity of roots to grow towards metal-enriched soil compartments. Two similar experiments were conducted in summer (slow growth) and spring (high growth), respectively. Our study is the first to show that NM plants of T. caerulescens have the ability to allocate more roots in the Zn-enriched compartment of soil. However, the positive response to Zn by roots of NM plants does not explain their higher Zn accumulation capacity as M plants express a similar level of root allocation in Zn-enriched compartment of soil. In M plants, root response to the Zn-rich compartment appears to be more susceptible to variations in growth conditions. Preferential root allocation in Ni-enriched compartment was consistently found in M plants only, suggesting that Ni supply is critical in their native metalliferous soil. Our study also illustrates bias in the interpretation of root allocation studies using two dimensional boxes, as interferences between root response to metal and root chirality have been highlighted. © 2008 Springer Science+Business Media B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe