The effects of organic residue quality on growth and reproduction of Aporrectodea trapezoides under different moisture conditions in a salt-affected agricultural soil

Understanding phosphorus (P) dynamics in tropical sandy soil treated with organic residues of contrasting quality is crucial for P management using organic amendments. This research determined P fractions in a tropical sandy soil under the application of organic residues of different quality, including groundnut stover (GN), tamarind leaf litter (TM), dipterocarp leaf litter (DP), and rice straw (RS). The organic residues were applied at the rate of 10 t DM ha−1 year−1. The P fractions were examined by a sequential extraction procedure. Organic residue application, regardless of residue quality, resulted in P accumulation in soils. For unamended soil, 55% of total P was mainly associated with Al (hydr)oxides. Organic residue application, regardless of residue quality, diminished the NH4F-extractable P (Al-P) fraction, but it had a nonsignificant effect on NaOH-extractable P (Fe-P). The majority of Al-P and Fe-P fractions were associated with crystalline Al and Fe (hydr)oxides. NH4Cl-extractable P (labile P), NaHCO3-extractable P (exchangeable P and mineralizable organic P), HCl-extractable P (Ca-P), and residual P fractions in soil were significantly increased as a result of the incorporation of organic residues. The application of organic residues, particularly those high in ash alkalinity, increase soil pH, labile P, and Ca-P fractions. In contrast, applications of residues high in lignin and polyphenols increase residual P fraction, which is associated with organo-mineral complexes and clay mineral kaolinite.

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Influence of four commonly used pesticides on the survival, growth, and reproduction of the earthworm Aporrectodea trapezoides (Lumbricidae)

Australian Journal of Agricultural Research ◽

10.1071/a98021 ◽

1998 ◽

Vol 49 (8) ◽

pp. 1297 ◽

Cited By ~ 14

Author(s):

L. P. D. Choo ◽

G. H. Baker ◽

L. P. D. Choo ◽

G. H. Baker

Keyword(s):

Filter Paper ◽

Field Experiments ◽

Application Rate ◽

Normal Rate ◽

Cocoon Production ◽

Application Rates ◽

Aporrectodea Trapezoides ◽

Growth And Reproduction ◽

Significant Mortality

The effects of 4 commonly used pesticides, endosulfan (insecticide), fenamiphos (nematicide), methiocarb (molluscicide), and ridomil (fungicide) on the survival, growth, and reproduction of the earthworm Aporrectodea trapezoides (Lumbricidae) were measured in laboratory and field experiments. When the earthworms were exposed to the pesticides on moist filter paper for 48 h, fenamiphos and, to a lesser extent, endosulfan caused significant mortality. In contrast, the survival of A. trapezoides was rarely affected by the pesticides during exposure for 5 weeks in pots and cages containing soil (only noted under 10 × normal application rate of endosulfan against adult worms). However, endosulfan did significantly reduce the weight of juvenile A. trapezoides within 5 weeks when applied to soil at normal application rate in both the field and laboratory. Fenamiphos did so at normal application rate in the field only. Fenamiphos and methiocarb reduced earthworm weight in the laboratory when applied at 10 × normal rate. The clitella of adult earthworms regressed with exposure to endosulfan at normal rate and also exposure to fenamiphos at 10 × normal rate. Cocoon production was inhibited by endosulfan and fenamiphos at normal application rates and methiocarb at 10 × normal rate. The use of some pesticides, in particular endosulfan, could significantly reduce the establishment of abundant and beneficial populations of earthworms in Australian pastures.

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Positive coupling between growth and reproduction in young post-fire Aleppo pines depends on climate and site conditions

International Journal of Wildland Fire ◽

10.1071/wf14045 ◽

2015 ◽

Vol 24 (4) ◽

pp. 507 ◽

Cited By ~ 13

Author(s):

Raquel Alfaro-Sánchez ◽

J. Julio Camarero ◽

Francisco R. López-Serrano ◽

Raúl Sánchez-Salguero ◽

Daniel Moya ◽

...

Keyword(s):

Water Balance ◽

Climate Warming ◽

Growth Patterns ◽

Tree Regeneration ◽

Aleppo Pine ◽

Pine Forests ◽

Female Cone ◽

Cone Production ◽

Moisture Conditions ◽

Growth And Reproduction

In fire- and drought-prone Mediterranean forests tree growth and regeneration depend on the moisture regime between fires. Therefore, post-fire tree regeneration will depend on moisture conditions and how they are altered by fire recurrence and climate warming. Aleppo pine forests are the most abundant Circum-Mediterranean ecosystems subjected to frequent wildfires and summer droughts. Because both stressors constrain their reproduction and growth patterns across diverse ecological conditions, these forests represent a suitable system to test how moisture availability drives post-fire regeneration. Aleppo pine is an obligate seeder species that reproduces at an early age after fire. Such precocious behaviour poses the question as to whether post-fire regeneration depends on moisture conditions and the coupling between female cone production and growth. Here, we evaluate if female cone production and radial growth are linked at the tree level in post-fire Aleppo pines by comparing a dry v. a very dry site and considering stands with three different tree densities in south-eastern Spain. We found that trees with higher basal areas produced more female cones and this positive association intensified as the water balance improved. Aleppo pines from the very dry site were more precocious in reproductive terms than pines of the same age from the dry site, but long-term cone production was lower at the very dry site. Lower tree density enhances the resilience of xeric post-fire Aleppo pine forests, in growth and reproduction terms, but this effect can be reversed by droughts. Overall, a more positive water balance improves post-fire regeneration by enhancing growth and cone production. Thus, silvicultural treatments such as thinning should be applied by taking into account the post-fire water balance to maximise growth and cone production in Aleppo pine stands. Our findings illustrate how climate warming could hamper post-fire tree regeneration by aggravating drought stress.

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A trait based approach to bacterial biofilms in soil

10.7287/peerj.preprints.1637v1 ◽

2016 ◽

Author(s):

Jay T Lennon ◽

Brent K Lehmkuhl

Keyword(s):

Water Availability ◽

Water Retention ◽

Niche Construction ◽

Moisture Gradient ◽

Bacterial Biofilms ◽

Soil Environment ◽

Soil Water Retention ◽

Biofilm Production ◽

Moisture Conditions ◽

Growth And Reproduction

One of the greatest challenges of living in the soil environment is that microorganisms must contend with fluctuations in water availability. Biofilm production is a trait that may helps bacteria persist through moisture conditions that are suboptimal for growth and reproduction. Using an alginate knockout of Pseudomonas aeruginosa, we demonstrate that biofilm production increased survivorship and created a more favorable moisture niche. Although biofilm production is assumed to incur a fitness cost, we were unable to detect a trade-off along a moisture gradient. In addition to increasing desiccation tolerance, biofilm production altered the soil environment in ways that were consistent with niche construction. Specifically, biofilm production increased soil water retention, but this did not facilitate the growth of an unrelated, desiccation-sensitive soil bacterium. In sum, our findings suggest that biofilm production is a response and effect trait that may influence the distribution and abundance of microorganisms in soil environments.

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