Researchers found extensive regions in which the addition of nitrogen or iron individually resulted in no significant phytoplankton growth over 48 hours. However, the addition of both nitrogen and iron increased concentrations of chlorophyll a by up to approximately 40-fold, led to diatom proliferation, and reduced community diversity. Once nitrogen–iron co-limitation had been alleviated, the addition of cobalt or cobalt-containing vitamin B12 could further enhance chlorophyll a yields by up to threefold. Results suggest that nitrogen–iron co-limitation is pervasive in the ocean, with other micronutrients also approaching co-deficiency. Such multi-nutrient limitations potentially increase phytoplankton community diversity.
Nutrient co-limitation at the boundary of an oceanic gyre
Burning of biomass releases particulate matter air pollution that causes oxidative stress as well as severe DNA damage in human lung cells — primarily through the actions of the polycyclic aromatic hydrocarbon (PAH) known as retene.
Researchers first determined the concentration of pollutants to be used in the lab experiments designed to mimic the exposure suffered by people who live in the area of the deforestation arc. Using mathematical models, the researchers calculated the human lung’s capacity to inhale particulate matter at the height of the burning season and the percentage of pollutants that is deposited in lung cells. Based on this theoretical mass, they determined the concentration levels to be tested using cultured cells.
After 72 hours of exposure, over 30% of cultured human lung cells died.
Biomass burning in the Amazon region causes DNA damage and cell death in human lung cells
The brown-rot fungal wood decay resulted in higher concentrations of soil C and N and a greater increase in microbial necromass (i.e., 1.3- to 1.7-fold greater) than the white-rot fungal wood decay. The white-rot sets were accompanied by significant differences in the proportions of the bacterial residue index (muramic acid%) with soil depth; however, the brown-rot-associated soils showed complementary shifts, primarily in fungal necromass, across horizontal distances. Soil C and N concentrations were significantly correlated with fungal rather than bacterial necromass in the brown-rot systems. Our findings confirmed that the brown-rot fungi-dominated degradation of lignocellulosic residues resulted in a greater SOM buildup than the white-rot fungi-dominated degradation.
… and that in the short-term carbon through microbial form immobilizes already available N, potentially making less available for plants or loss through leaching.
The belief that adding high-carbon mulch locks up nitrogen may yet have some merit, not necessarily in the mulch, but in the microbes!
Although C input promoted microbial growth and N demand, we did not find indicators of increased N mobilization from SOM polymers, given that none of the soils showed a significant increase in protein depolymerization, and only one soil showed a significant increase in N-targeting enzymes. Instead, our findings suggest that microorganisms immobilized the already available N more efficiently, as indicated by decreased ammonification and inorganic N concentrations. Likewise, although N input stimulated ammonification, we found no significant effect on protein depolymerization. Although our findings do not rule out in general that higher plant-soil C allocation can promote microbial N mining, they suggest that such an effect can be counteracted, at least in the short term, by increased microbial N immobilization, further aggravating plant N limitation.
You would think that a plant would either produce a lot of defensive chemicals to prevent it from being eaten or that it would put its energy into regrowing after being eaten — but not both, given its limited energy,” said graduate student Miles Mesa, who led the research with University of Illinois animal biology professor Ken Paige. “But we found that the plants that overcompensated — with higher reproductive success after having been damaged — also produced more defensive chemicals in their tissues.”
About 90 percent of herbaceous flowering plants engage in a process called endoreduplication — duplicating all of the genetic material in their cells without cell division, the researchers said. This process increases cell size, allowing the plants to quickly rebound from damage.
Each round of endoreduplication doubles a cell’s output. Having twice as many active genes means the cell can pump out more proteins needed to perform cellular tasks.
Some plants multiply their genomes again and again in response to being browsed. One example is scarlet gilia, a red-flowered plant that grows in western North America and is browsed by elk and mule deer. Paige is studying its responses to being eaten.
“We’re seeing two- and three-fold increases in yield after it has been cut — in the same season,” he said.
Plant roots are five times more likely than leaves to turn into soil organic matter for the same mass of material.
This among other findings from Stanford researchers.
Improving how land is managed could increase soil’s carbon storage enough to offset future carbon emissions from thawing permafrost, the researchers find. Among the possible approaches: reduced tillage, year-round livestock forage and compost application. Planting more perennial crops, instead of annuals, could store more carbon and reduce erosion by allowing roots to reach deeper into the ground.
Soil holds potential to slow global warming | Stanford News