Root growth of <i>Lotus corniculatus</i> interacts with P distribution in young sandy soil

Abstract

Abstract. Large areas of land are restored with unweathered soil substrates following mining activities in eastern Germany and elsewhere. In the initial stages of colonization of such land by vegetation, plant roots may become key agents in generating soil formation patterns by introducing gradients in chemical and physical soil properties. On the other hand, such patterns may be influenced by root growth responses to pre-existing substrate heterogeneities. In particular, the roots of many plants were found to preferentially proliferate into nutrient-rich patches. Phosphorus (P) is of primary interest in this respect because its availability is often low in unweathered soils, limiting especially the growth of leguminous plants. However, leguminous plants occur frequently among the pioneer plant species on such soils, as they only depend on atmospheric nitrogen (N) fixation as N source. In this study we investigated the relationship between root growth allocation of the legume Lotus corniculatus and soil P distribution on recently restored land. As test sites, the experimental Chicken Creek Catchment (CCC) in eastern Germany and a nearby experimental site (ES) with the same soil substrate were used. We established two experiments with constructed heterogeneity, one in the field on the experimental site and the other in a climate chamber. In addition, we conducted high-density samplings on undisturbed soil plots colonized by L. corniculatus on the ES and on the CCC. In the field experiment, we installed cylindrical ingrowth soil cores (4.5 × 10 cm) with and without P fertilization around single two-month-old L. corniculatus plants. Roots showed preferential growth into the P-fertilized ingrowth-cores. Preferential root allocation was also found in the climate chamber experiment, where single L. corniculatus plants were grown in containers filled with ES soil and where a lateral portion of the containers was additionally supplied with a range of different P concentrations. In the high-density samplings, we excavated soil-cubes of 10 × 10 × 10 cm size from the topsoil of 3 mini-plot areas (50 × 50 cm) each on the ES and the CCC on which L. corniculatus had been planted (ES) or occurred spontaneously (CCC) and for each cube separated the soil attached to the roots (root-adjacent soil) from the remaining soil (root-distant soil). Root length density was negatively correlated with labile P (resin-extractable P) in the root-distant soil of the CCC plots and with water-soluble P in the root-distant soil of the ES plots. The results suggest that P depletion by root uptake during plant growth soon overrode the effect of preferential root allocation in the relationship between root density and plant-available soil P heterogeneity.

Cluster root allocation of white lupin (Lupinus albusL.) in soil with heterogeneous phosphorus and water distribution

“…The lack of a P fertilization effect on shoot biomass production was in contrast to P-limited growth observed on the same soil in Lotus corniculatus L. (Felderer et al 2013). It may have been due to a higher P acquisition efficiency of white lupin and/or to a larger P supply from the seeds.…”

Editorial "Ecosystems in transition: interactions and feedbacks with an emphasis on the initial development"

“…The mentioned Chicken Creek project led to a number of results that are of importance for the understanding of initial ecosystem state transitions (see Hüttl et al, 2013): It was found that the basic assumption of low heterogeneity and structuring of ecosystems in their initial stage was essentially correct. Though small, it seems that these heterogeneities were of great importance for the later development of the system, however, as highlighted by Felderer et al (2013) and Biber et al (2013) in this issue. This relates to earlier publications from the Chicken Creek project, which show that slight differences in substrate properties influenced hydrological pathways, such as erosion rill patterns (Hofer et al, 2012) and groundwater flow patterns (Hofer et al, 2011).…”

“…Fischer et al (2012) show that biocrusts developing on bare surfaces of initial soils can have direct feedbacks effects on physical site conditions. Biber et al (2013) analyze relationships between initial site conditions and evolving vegetation patterns, whilst Felderer et al (2013) investigate strategies of plants to forage for phosphorus as a soil nutrient that is often of very low availability in initial ecosystems. Finally, Mueller-Dombois and Boehmer (2013) summarize the long-term primary succession of Hawaiian rainforest ecosystems which may serve as reference sites for initial ecosystems due to frequent disturbances by volcanism.…”

Landscape Development From Point Zero

“…Favorable effects on root development of L. corniculatus were observed in sandy soils containing finer-textured fragments (Boldt-Burisch et al 2013). As nutrient availability is usually limited under initial soil conditions and particularly phosphorus is a limiting factor for plant growth, it was observed both under experimental and field conditions that L. corniculatus roots increase and are preferentially abundant in P-enriched soil patches (Felderer et al 2013). Due to P uptake by roots and mycorrhizal fungi a depletion of P in these patches revealed that the original distribution of nutrients is changed by the developing vegetation.…”