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Soil Phosphorus (soil + phosphorus)
Selected AbstractsSoil phosphorus and disturbance influence liana communities in a subtropical montane forestJOURNAL OF VEGETATION SCIENCE, Issue 3 2010Agustina Malizia Abstract Questions: What are the effects of soil, topography, treefall gaps, tree species composition, and tree density on liana species composition and total liana abundance? Location: A 6-ha permanent plot in a subtropical montane forest in northwest Argentina. Methods: Multiple regressions were used to quantify associations of liana species composition and total liana abundance with edaphic, disturbance and tree community variables. Gradients in liana and tree species composition were quantified using principal components analysis (PCA). Results: Liana species composition was correlated most strongly with soil phosphorus concentration (R2=0.55). Total liana aanased with phosphorus and the density of recent treefall gaps (R2=0.60). Conclusions: In our study area, liana composition and abundance are most strongly correlated with features of the physical environment, rather than host tree characteristics. Our results support the hypothesis that recent increases in liana abundance in mature tropical forests may be related to increased rates of gap formation. [source] Enhancing diversity of species-poor grasslands: an experimental assessment of multiple constraintsJOURNAL OF APPLIED ECOLOGY, Issue 1 2007RICHARD F. PYWELL Summary 1Many grasslands in north-west Europe are productive but species-poor communities resulting from intensive agriculture. Reducing the intensity of management under agri-environment schemes has often failed to increase botanical diversity. We investigated biotic and abiotic constraints on diversification by manipulating seed and microsite availability, soil fertility, resource competition, herbivory and deficiencies in the soil microbial community. 2The effectiveness of 13 restoration treatments was investigated over 4 years in a randomized block experiment established in two productive grasslands in central-east and south-west England. 3Severe disturbance involving turf removal followed by seed addition was the most effective and reliable means of increasing grassland diversity. Disturbance by multiple harrowing was moderately effective but was enhanced by molluscicide application to reduce seedling herbivory and by sowing the hemiparasite Rhinanthus to reduce competition from grasses. 4Low-level disturbance by grazing or slot-seeding was ineffective in increasing diversity. Inoculation with soil microbial communities from species-rich grasslands had no effect on botanical diversity. Nitrogen and potassium fertilizer addition accelerated off-take of phosphorus in cut herbage but did not cause a reduction in soil phosphorus or increase botanical diversity. 5Different grazing management regimes had little impact on diversity. This may reflect the constraining effect of the July hay cut on species dispersal and colonization. 6Synthesis and applications. Three alternative approaches to grassland diversification, with different outcomes, are recommended. (i) High intervention deturfing, which would create patches with low competitive conditions for rapid and reliable establishment of the target community. For reasons of cost and practicality this can only be done over small areas but will form source populations for subsequent spread. (ii) Moderate intervention (harrowing or slot-seeding) over large areas, which would establish a limited number of desirable, generalist species that perform well in restoration. This method is low cost and rapid but the increases in biodiversity are less predictable. (iii) Phased restoration, which would complement the above approaches. Productivity and competition are reduced over 3,5 years using Rhinanthus or fertilizers to accelerate phosphorus off-take. After this time harrowing and seeding should allow a wide range of more specialist species to establish. However, further research is required to determine the long-term effectiveness of these approaches. [source] Effect of land use on some soil properties related to the risk of loss of soil phosphorusLAND DEGRADATION AND DEVELOPMENT, Issue 1 2008F. Troitiño Abstract Although land use clearly modifies soil properties, the intensity of the modifications depends on the management procedures and also on the soil properties themselves. To enable construction of models that describe soil nutrient losses, extensive databases corresponding to soils under different land use must be made available. Analysis of 404 samples of soils (from Galicia, NW Spain), under different types of use revealed that most of the soil properties underwent changes in the following order: forest use (least modified) - grassland - arable (most modified). Decreases in the contents of organic matter, extractable oxides and P-adsorption capacity followed the same order, as did increases in the contents of available P (total, inorganic and organic), P desorbed with distilled water, and degree of P saturation. In general, in all of the soils, independently of their use, the amount of P desorbed (whether total P, molybdate reactive P or particulate P) was more closely related to the degree of P saturation than to the levels of P extracted with bicarbonate. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mycorrhizal infection and high soil phosphorus improve vegetative growth and the female and male functions in tomatoNEW PHYTOLOGIST, Issue 1 2002Jennifer L. Poulton Summary ,,To further characterize the effects of mycorrhizal infection and soil phosphorus (P) availability on plant fitness, this study examined their effects on the female and male functions, as well as vegetative growth of tomato (Lycopersicon esculentum). ,,Two cultivars of tomato were grown in a glasshouse under three treatment combinations: nonmycorrhizal, low P (NMPO); nonmycorrhizal, high P (NMP3); and mycorrhizal, low P (MPO). ,,Mycorrhizal infection and high soil P conditions improved several vegetative (leaf area, days until first flower and leaf P concentration) and reproductive traits (total flower production, fruit mass, seed number and pollen production per plant, and mean pollen production per flower). In general, mycorrhizal and P responses were greater for reproductive traits than vegetative traits. In one cultivar, these responses were greater for the male function than the female function. ,,Thus, mycorrhizal infection and high soil P conditions enhanced fitness through both the female and male functions. Similar trends were usually observed in the NMP3 and MPO treatments, suggesting that mycorrhizal effects were largely the result of improved P acquisition. [source] Physiological changes in white lupin associated with variation in root-zone CO2 concentration and cluster-root P mobilizationPLANT CELL & ENVIRONMENT, Issue 10 2005M. D. CRAMER ABSTRACT White lupin (Lupinus albus L.) mobilizes insoluble soil phosphorus through exudation of organic acids from ,cluster' roots. Organic acid synthesis requires anaplerotic carbon derived from dark CO2 fixation involving PEP-carboxylase. We tested the hypothesis that variation in root-zone CO2 concentration would influence organic acid synthesis and thus P mobilization. Root-zone CO2 concentrations and soil FePO4 concentrations supplied to sand-grown white lupin (cv. Kiev Mutant) were varied. More biomass accumulated in plants supplied with 360 µL L,1 CO2 to the root-zone, compared with those aerated with either 100 or 6000 µL L,1 CO2. Increased FePO4 in the sand resulted in greater leaf P concentrations, but root-zone [CO2] did not influence leaf P concentration. Suppression of cluster-root development in plants supplied with 100 µL L,1 root-zone CO2 was correlated with increased leaf [P]. However, at both 360 and 6000 µL L,1 CO2, cluster-root development was suppressed only at the highest leaf P concentration. Phloem sap [P] was significantly increased by greater [FePO4] in the sand, but was reduced with increased root-zone [CO2], and this may have triggered increased cluster-root initiation. Succinate was the major organic acid (carboxylate) in the phloem sap (minor components included malate, citrate, fumarate) and was increased at greater [FePO4], suggesting that this shoot-derived carboxylate might provide an important source of organic acids for root metabolism. Since cluster root development was inhibited by increasing concentrations of FePO4 in the sand, it is possible that succinate was utilized for the functioning of the root-nodules. [source] | |||||||||||||