Brush piles and mesh cages protect blue oak seedlings from animals

Oak tree branches piled over acorn-seeded blue oaks were tested as protection against cattle and deer. The piles remained in place and apparently free of cattle and deer for 8.5 years, until a wildfire destroyed the branches. Before the fire in 1996, seedlings in the brush had similar survival rates but grew significantly faster than seedlings with no brush. Seedling survival and growth rates declined sharply after the fire, although the surviving trees regained their prefire heights in 3 years. Cages made of aluminum window screening, as protection from small animals, significantly increased seedling survival and growth rates. Growth rates over the 12 years of the trial averaged only about 0.5 to 1 inch per year

Legumes show success on Central Coast rangeland

Improvements for rangeland and ley farming systems must be economical and long-lasting if they are to be used by ranchers in low-rainfall areas of California. Commercial and research seedings of annual legumes dating back to the 1970s and 1980s prove that certain medic varieties can be established economically and will remain productive for decades on rangelands with neutral to basic soils. In a 12-year variety trial conducted in eastern San Luis Obispo County, 13 of 18 medics survived

Live oak saplings survive prescribed fire and sprout

Sapling surveys conducted before and after a prescribed fire in an oak woodland revealed that approximately half of marked blue oak and coast live oak saplings were top-killed (aboveground tissue of sapling killed) by the fire. Most top-killed saplings sprouted, and sprout growth was strong within one growing season. Light-intensity prescribed fires probably have little effect on overall sapling survival and recruitment, and may benefit individual saplings by reducing competition and recycling nutrients

The landscape of recombination in African Americans

Recombination, together with mutation, is the ultimate source of genetic variation in populations. We leverage the recent mixture of people of African and European ancestry in the Americas to build a genetic map measuring the probability of crossing-over at each position in the genome, based on about 2.1 million crossovers in 30,000 unrelated African Americans. At intervals of more than three megabases it is nearly identical to a map built in Europeans. At finer scales it differs significantly, and we identify about 2,500 recombination hotspots that are active in people of West African ancestry but nearly inactive in Europeans. The probability of a crossover at these hotspots is almost fully controlled by the alleles an individual carries at PRDM9 (P<10(−245)). We identify a 17 base pair DNA sequence motif that is enriched in these hotspots, and is an excellent match to the predicted binding target of African-enriched alleles of PRDM9