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.
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?