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Has water use efficiency improved in fortes with rising carbon dioxide concentrations?

Published: Tuesday July 23 2013, 15:00:50

Carbon dioxide (CO2) is a vital element for all photosynthetic plants as it is the building block for their growth. Plants take up CO2 via opening in their leaves but at the same time water is lost to the atmosphere (transpiration). Water is another vital element for plants and they want to restrict this loss. So plants need to achieve a balance of taking in enough CO2 for growth while at the same time limiting the loss of water vapour. The more efficient the uptake of CO2 the better this is for photosynthesis. One argument that has been put forward is that under higher concentrations of CO2 plants may be more efficient in their water use since less is likely to be lost when CO2 is taken in.

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Trees in both wet and dry forests are vulnerable to drought conditions

Published: Thursday January 24 2013, 16:07:02

Stress caused by droughts has long term implications for forest coverage according to a new study in Nature. Changes in rainfall patterns (both timing and location) coupled with higher temperatures can lead to a reduction in forested areas in locations where droughts are forecast to increase. It is known that sensitivity to drought is a factor driving the distribution of individual plant types. There is recent evidence that rising temperatures are enhancing chances in forests brought on by drought conditions. One outcome of longer droughts and higher temperatures is rapid forest collapse which has a knock on effect on global forests and their carbon storage ability. Indeed parts of the Amazon forest continues to suffer from the effects of a drought which started in 2005 (for details see here ). Using satellite data, a change in forest canopy has suggested widespread dieback of older, larger trees in the SW Amazon rainforest. Despite rainfall levels returning to more normal conditions, these old growth trees did not appear to recover. The persistence of damage caused by drought could be explained by the new study of Choat et al. that details the physiological mechanisms which govern drought stress in individual tree species. This new study describes the harm caused by the development of gas bubbles in the water vessels transporting water throughout the plants/trees. Understanding how this transport system functions is important for predicting how forests will respond to changes in future climates.

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Water Recycling in Rainforests Influences Rainfall

Published: Wednesday September 12 2012, 15:03:40

A new study shows that the amount of rainfall can be influenced by the degree of forest cover. While there is plenty of anecdotal evidence that forests significantly increase rainfall, until now there has been a lack of observational evidence. Vegetation has been shown to influence precipitation patters because of evapotranspiration. This is the process by which water that is taken in by a plant via its roots and is lost to the atmosphere by its leaves. This pump-like process adds moisture to the atmosphere which in turn influences the energy balance and trace-gas fluxes. If forests are replaced by cropland, this diminished the atmospheric humidity which has the potential to suppress rainfall.

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Climate change influencing mountain plants at an accelerated rate

Published: Thursday May 3 2012, 09:04:45

A new study across Europe shows plants are moving to higher latitudes but such changes can lead to a reduction in species richness. This new study detailed 66 mountain summits located between the north of Europe and the southern Mediterranean Sea. First in 2001 and then in 2008 maps of plant species were taken using the same methods and procedures. Only a few summits of northern and central Europe recorded increasing species numbers, in contrast nearly all sites in the Mediterranean regions showed stagnating or declining species numbers.
Dr Harald Pauli, from the Global Observation Research Initiative in Alpine Environments (GLORIA), the study’s lead author, said, “Our results showing a decline at the Mediterranean sites is worrying because these are the mountains with a very unique flora and a large proportion of their species occur only there and nowhere else on Earth.”

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New study of soil moisture and storm generation could improve rainfall prediction in West Africa

Published: Thursday January 19 2012, 13:29:38

A new study of how storms are generated could improve rainfall prediction in dry regions of Africa where drought and short growing seasons are common. A team of international scientist used satellite observations to demonstrate that short lived changes in soil moisture over tens of kilometres can affect storm generation. Observational data was created using high resolution satellite images every 15 minutes over few kilometres on a daily basis for wet season of 2006-2010.

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