Volcanic after effects

the Hawaiian volcano of Mauna Loa supports an extraordinary range of climates and ecosystems. Yet the slopes of the volcano are constantly being resurfaced by the red-hot lava that destroys everything in its path. After an eruption, the cooled lava quickly becomes a home for plants -- a unique resource for biologists interested in the first signs of life on a new land. Mauna Loa's range of climates and ecosystems include steamy lowland tropical forests to freezing alpine areas near its 4170 m summit and soggy cloud forests with more than 7.3 m of rain each year ( Natural History , Vol 106, No 5).

Scientists at Stanford University and the University of Hawaii have now succeeded in dating and mapping most of Mauna Loa's hundreds of lava flows. They examined the flows that occurred from November 1880 to December 1881, when a great outpouring of lava emerged at 3078.5 m and flowed 42 km, stopping just outside the old town of Hilo.

Scientists found that at about 2438.4 m, lichens covered the rock surface, softening its rough edges. Farther down the flow, near 1524 m, the lichens began to disappear and the 'ohia trees grew denser. The 'ohia tree ( Metrosideros polymorpha ) covers most of the forested area of Mauna Loa. By 914.4 m above the sea level, the organic residue leaves dead and decaying leaves to cover deep cracks in the lava, providing enough soil for small groves of 'ohia trees. At 304.8 m, the 'ohia trees reach a height of 6.07 m. Scientists wanted to determine what controls plant growth, soil development and nutrient cycling. They found that nitrogen and phosphorus that are available for new plants helps them to grow more quickly and in large quantities: 'ohia leaves from the lower, warmer reaches of lava flows contain more nutrients than the leaves from cooler uplands. This helps young rainforests to develop in warm, wet lowlands while equally wet but cooler areas support only shrublands.