Climate change and plant growth (journal)

Vegetation productivity responds to sub-annual climate conditions across semiarid biomes

This is an open-access paper - free to all.

 I know it can be daunting reading a scientific paper that is not in your specialised area, so I've added a summary below and a couple of hints on key knowledge to help those who want it. - Naomi.

Article summary
One predicted impact of climate change is longer and more frequent droughts in some areas of the world.  The timing of rainfall both over one year (within-year / intra-annual) and over many years (inter-annual) is important in understanding how plant communities might respond.

In this journal paper, researchers looked at responses of grassland, shrubland and forest communities in the semi-arid southwestern USA to prolonged drought.  They found that:

• Production in all biomes was impacted by rainfall and temperature
• Higher rainfall is linked with higher production.
• Critical timescales (when production is most affected by temperature and rainfall) are:
• Forests  - January through to September.  
• Shrubland - July and August.  
• Grassland - July through to September
• Production in forests was driven by winter precipitation (which replenishes soil moisture) and limited by maximum summer temperatures.
• Production for shrubs and grassland was driven by summer rainfall and limited by high daily maximum temperatures in summer
• Plant growth increases as temperatures increase to a maximum daily temperature of ~17 degrees C and then rapidly declines when maximum temperatures rise above that.
• It is important to consider both temperature and precipitation patterns when seeking to understand vegetation responses.

Key knowledge and terms used
The balance between temperature and rainfall is directly linked to the kinds of plants that can thrive and ultimately can define biomes at a global level.  The hotter it is, the more water a plant needs to use (through evapotranspiration).  Broadly speaking - Little rainfall = desert, (high temp like Sahara or low temp like Antarctica);  Lots of water and cool temperature = temperature forest; Moderate water and cool temperature = temperate grasslands; Lots of water and high temperature = tropical rainforest.

This paper uses a way of measuring this balance temperature and rainfall called Standardised Precipitation Evapotranspiration Index (SPEI).

Enhanced Vegetation Index (EVI) is a proxy measure of plant growth - it uses satellite data to detect small changes in colour (greenness)


Links to permaculture
Can we use knowledge from natural communities to think about how our natural ecosystems and/or annual crops and forest gardens might respond and how we could adapt?  When might be critical to store/use water?

Addressing water scarcity (book)

Chasing Water: A Guide for Moving from Scarcity to Sustainability

Water scarcity is spreading and intensifying in many regions of the world, with dire consequences for local communities, economies, and freshwater ecosystems. Current approaches tend to rely on policies crafted at the state or national level, which on their own have proved insufficient to arrest water scarcity. To be durable and effective, water plans must be informed by the culture, economics, and varied needs of affected community members. Chasing Water tells a cohesive  story that sustainable water sharing in the twenty-first century can only happen through open, democratic dialogue and local collective action.

Trees help farmers manage drought (report)

Managing the drought: A review of the evidence of the benefits of native trees species for shelter on the water regime of pasture and arable crops

This review assesses the benefits of native tree species for shelter on the water regime of pasture and crops. It draws on evidence from the UK, Europe and other temperate zones. Before the evidence is presented overviews are given of evapotranspiration, shelterbelt design and crop micro-climate. The evidence in the review suggests that under the right conditions native tree shelterbelts could enable UK crops to use water more efficiently. Shelterbelts can be viewed as an insurance policy. They may not provide yield increases every year, but they can buffer crop production when extreme weather events strike.