Hot answers tagged

50

I am an archaeologist and I specialize in the ancient Maya. Here's how it happens: 1: The vast majority of ancient Maya buildings are built using a "core and veneer" technique. The bulk of the building's volume is earth and stone rubble, faced with a veneer of nicely-shaped limestone blocks that are themselves covered by a layer of lime plaster (stucco). ...


16

The accumulation of soil in such situations takes a long time. The main way soil would have been naturally transported there would be by the wind. The wind blown soil would get caught and accumulate. Plants, particularly grasses, would grow on the soil and the plant roots would create mesh that would protect the soil from erosion. You are correct in that ...


13

It will depend on the time of year and the time of day. As you noted, you often see more frost in an open field than in a forest. A comment indicated the forest insulated the surface but I believe it will also reduce radiant heat loss at night, compared to the open field. During the day, the ground surface is more shaded and the trees reduce the advective ...


11

For rain to fall, water vapour must exist in sufficient quantities in the atmosphere. The main source of atmospheric water vapour is evaporation from oceans. However, evaporation from large bodies of water such as lakes and dams also contributes. Another significant contributor, on a local level, is transpiration from forests. the Amazon alone creates 50-...


10

Leaves, mostly. Photosynthesis requires carbon dioxide, and it gets it via stomata - small controllable pores in the leaf. When the stomata open, water goes out, because the air is generally drier than the interior of the leaf. Water in the leaves is drawn up from the roots, via the xylem, using the suction from the lost water in the leaves, and also acting ...


9

Don't forget the protection from wind in colder seasons as well. Basic survival skill is to always make shelters under cover (as in a forest) rather than in an open meadow. On a cold day it may not feel much warmer in still air but getting out of the wind does make a significant difference.


8

I cannot find any language in peer-reviewed literature (as far as publicly accessible) that makes the 20% claim reported in the question. I therefore consider this claim to be of obscure and dubious origin. About 50% to 55% of the oxygen produced via photosynthesis is estimated to come from the world's oceans, as reported in the following two papers: ...


7

The difference is that a carbon sink accumulates carbon, whereas a carbon reservoir has accumulated carbon. That is to say: A carbon sink is an ongoing process which is increasing the amount of carbon stored in it. Whereas although a carbon reservoir might exchange individual carbon-based molecules with other parts of the carbon cycle, as much will go out ...


7

One of the consequences that I find more fascinating with the increased CO2 problem is the changes that affect specific components of the environment. One example that I like is the effect on poison ivy. Researchers at Duke University (Mohan et al., 2006), as part of their Free-Air CO2 Enrichment (FACE) experiment, reported a large change in poison ivy ...


7

If you increase CO2 concentration and keep all other parameters at there current level, then biomass production should go up. The reason is simply that CO2 is one of the building blocks biomass is made of in photosynthesis. In the real world it's trickier than that of course. Here you have to take into account how natural cycles will be affected by ...


7

Short answer Different plants reflect light at different wavelengths with specific patterns. If you know the reflection pattern of a broad-leaved forest and that of a needle-leaved forest, you can compare them with the pattern observed with a satellite and conclude to which forest it is more similar. Long answer Optical remote sensing Optical sensors ...


6

Forests directly below the alpine tree line are high-elevation or Montane forests. See more about Montane ecology here. Image from http://www.nature.com/scitable/knowledge/library/global-treeline-position-15897370


6

Wildfires are mainly caused by humans (or their technology) and lightning. Lightning is the most prolific natural source. There really aren't many other sources in most areas, unless there is volcanic activity or a meteor strike as you mention. There are also occasional cases of wildfire when peat dries out. During a hot-dry summer, it can take several ...


6

When I need data about past and future projected land use change, I usually refer to the global dataset that was developed for the global climate simulations CMIP6. The dataset is the Land Use Harmonization V.2 LUHv2 and it was developed by researchers at the University of Maryland. Reading the supporting document of the dataset, among others, the ...


6

Right, there are a lot of misconceptions about this. They are mostly to do with the difference between the magnitude of carbon storage and the rate of carbon uptake, and also the difference between whole site carbon storage and above ground biomass carbon storage. There is also ongoing research taking place which (as you might imagine) takes a very long time ...


5

In general, no, NDVI is not used to derive vegetation type. NDVI is useful for studying phenology, but it won't tell you the type of plant that is being remotely sensed. Good land cover systems use a variety of data sources to derive general plant type (e.g. conifer vs deciduous). For instance, the National Land Class Database (NLCD) description states: ...


5

This is counterproductive, both ecologically and economically, and is also well beyond the capabilities of current robots. Ecologically counterproductive Forests have evolved to live with, and in many cases, to depend on forest fires. Aggressive fire prevention by the US Forest Service and other agencies throughout much of the 20th century resulted in ...


5

Do we need to worry about oxygen? No. Although some reports have claimed the Amazon produces 20% of the world’s oxygen, it is not clear where this figure originated. The true figure is likely to be no more than 6%, according to climate scientists such as Michael Mann and Jonathan Foley [Twitter links]. Even if it were accurate, the crops being planted in ...


5

A "highly tapering stem" is simply that the trunk of the tree is less cylindrical and more conical in profile. It's a problem because while you may have a lot of timber volume you don't have as much timber that is usable because you'll end up with a higher proportion of sawmill waste. I'm English and have a degree in forestry. Regardless of comments ...


4

The same issue arises when land is bought and sold. The area used is the flat area from a plan. Slope is not considered because it would require at lot of data because the rate of change of topography and slopes is never uniform. Also the calculations to determine the true area can be convoluted if the change in topography is complex.


4

A carbon reservoir is measured by the amount of carbon it contains, for example kilograms of carbon [kg C]. A carbon source or sink is measured by the amount that comes out or into the reservoir from the rest of the system per unit of time, for example kilograms per day [kg C/day]. A coal or oil deposit can be either a reservoir or source, as carbon flows ...


4

It seems that tropical forests absorb more carbon dioxide than many scientists have believed before. NASA and NCAR scientists have shown that tropical forests absorb 1.4 billion metric tons out of a total global absorption of 2.5 billion metric tons. This estimate is much larger than previous estimates and the tropical contribution seems to be much larger ...


4

CO2 can only enhance plant growth when other resources such as nutrients or water are not limiting growth. If N for instance is scarce, no matter how much you increase CO2, plants will not take advantage of the increased CO2 concentration.


4

Nobody knows - yet. But one can say that these rings are too numerous and too regular in shape to be related to either kimberlites or (even more bizarrely) Oklo-type natural nuclear reactors, as some have suggested. For what it is worth, here is my own hypothesis: The areas concerned are all periglacial in an area of abundant boulder clay. In colder ...


4

Your idea has merit. Shale is classified by geologists as being a mudstone. It is composed of silt and clay sized minerals. According to this geology website, shales can be crushed to produce a clay and then mixed with water. These days, items that were once made from natural clay, such as terracotta pots and tiles for roofs, are now made from crushed shale....


4

Most fires are probably in the periphery because they are started by humans. They encroach on the jungle from the outside, where they already live, and there are roads instead of impenetrable jungle.


4

Most of the Mexican pyramids are less steep than their Egyptian counterparts, and have niches and terraces which their Egyptian counterparts don't. An important difference is the climate, which is much damper in Mexico, and shows how the rainforest can reclaim areas where it has been eradicated if the site is then abandoned. Yet another factor is the type of ...


3

This book is based on Australian experience, some of it may be relevant of North American wildfires. I read it ten years ago. Paul Collins, Burn - The Epic Story of Bushfire in Australia, Allen & Unwin, 2006, ISBN 9781741750539, ISBN 1 74175 053 9. Part 4, titled: The Great Fire Debates, has three chapters (9 to 11); 09 To burn or not to burn 10 ...


3

It has been suggested that proper management of large herds of goats, cattle, deer, or elephants on the land are effective in preventing desertification. So perhaps this could be used to mitigate conditions leading to excessive grass and forest fires. Maybe your idea would scale-up more effectively if the robots were set to manage large herds of animals that ...


3

David LeBauer is correct in saying that there are 'allometric equations' to estimate the leaf biomass, but they only refer to small experimental plots in such places as Hawaii, Japan, Singapore and Malaysia. The number of species involved is a few dozen at most. As 'N9ZN' points out, trying to develop generalizations would be a titanic task, and essentially ...


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