What causes patterns of vegetation and soils across landscapes and ecosystems?

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Biological, physical, geological, climatic and hydrological factors all play roles in patterns

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Complex landscape patterns are all around us in the bay area. I like the patterns set up between ridges and draws in our savannas. The draws are dominated by woody plants, as lateral flows of water help sustain the higher needs (100 mm per year) of water needed.

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. Here is the patterns we see flying into Tucson. You can see trees route along river channels. A little extra water in this arid environment is enough to support woody vegetation that outlines the water courses

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Here is the pattern of the land on Mars. Those looking at Mars are trying to decide if there was water at one time, based on the patterns on earth

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At water becomes limited, trees become more spatially detached in space, forming gaps between one another

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Types of spatial patterns formed

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Several factors can form patterns in semi-arid systems. It is not all directly water, but can be indirectly related through facilitation and alleopathy

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Here are some of the feedbacks between enhancing and inhibiting vegetation

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Rain interception is another issue, as that can reevaporate water that does not get to the ground if there are lots of light rains

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Laurel Larson, in Geography, studies land patterns in the Everglades. Notice the ridges and sloughs that form

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Larson created models that link geomorphology, velocity of water flow, peat formation and ecology that forms these patterns

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Movement of water and soil and plant build up form these patterns

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Where phosphorus is limited, tree islands, can be self sustaining, with bird deposits

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Deltas of the world are important patterns for wildlife, people, with many ecological services, nurseries for fish and birds, protection against storm surges

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We have an inverted inland Delta in California.

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Glacial till, Lakes and fire scars, aspen and pine; climate gradients aspen grow where ET < ppt; Spruce grow where ET > ppt

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LP0: < 40 years old; LP1: mature, closed canopy, 40 to 150 years since burn: LP2: 150 to 250 year, mixed forest; LP3 > 250, much mortality

The spatial pattern of forests affect their response to fire spread

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Polygons in the tundra are either deep centered or high centered. As the polygons form and collapse.

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http://ngee-arctic.blogspot.com/2011_08_01_archive.html

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Ice-Wedge Formation; Shaver et al 1979 J Ecol

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Microtopography, ice wedges, filling and periodic drainage, meadows form and fill ponds, carex

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Logging in the Pacific Northwest

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How do river networks form. Why do they have dendritic shapes like a leaf?

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What type of river networks are possible and why do branched networks tend to form?

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Look at the land from google earth and you’ll tend to see two types of rivers formed, meandering and braided. Whey the difference?

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The coexistence of vegetation helps form meandering rivers

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Experiment in a flume by Dietrich’s lab showed that meandering rivers formed with alfalfa spoutes

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Important topic in terms of biodiversity.

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Scaling forced by positive spatial feedbacks; probability of establishment increases with tree density; prob of mortality increases with open spaces; soil moisture key; less soil evaporation under trees.

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