Clark Lab

Clark contributed to the Forests chapter:

Earth’s climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities. The impacts of global climate change are already being felt in the United States and are projected to intensify in the future—but the severity of future impacts will depend largely on actions taken to reduce greenhouse gas emissions and to adapt to the changes that will occur… [read the report]

 

The amount of water available to a tree determines its susceptibility to drought.  It has been one of the big unknowns in predicting responses to climate change. Here we show that it can be measured: 

We apply this model to multiple seasonal droughts with tree transpiration measurements to demonstrate how species and size differences modulate moisture availability across landscapes. The depletion of individual moisture reservoirs can be tracked over the course of droughts and linked to biomass growth and reproductive output. This mass balance approach can predict individual moisture deficit, tree demographic performance, and drought vulnerability throughout forest stands based on measurements from a sample of trees, more here 

A warming climate is changing the pace of spring green-up.  Using remote sensing and a new approach that quantifies the rate of green-up, Seyednasrollah et al show that green-up is fast in the mountains and relatively insensitive to temperature anomalies, while slow development in warm, coastal forests can respond to temperature swings.  Confirming experimental evidence, this study shows that spring is compressed in cold climates, delayed in onset but then rapidly progressing to full leaf expansion. Conversely, mountainous forest green-up is more susceptible to intensifying drought and moisture deficit, while coastal areas are relatively resilient. Canopy thermal stress slows leaf development following dry years, but accelerates it following wet years.  The study is published in Remote Sensing of Environment.

Now out in Ecology:

Arbuscular mycorrhizal (AM) fungi in the soil may influence tropical tree dynamics and forest succession. The mechanisms are poorly understood, because the functional characteristics and abundances of tree species and AM fungi are likely to be codependent. We used generalized joint attribute modeling to evaluate if AM fungi are associated with three forest community metrics for a sub-tropical montane forest in Puerto Rico.  (read more …)