Clark Lab

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…

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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…

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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 …)

“Congratulations on your most most downloaded article in Global Change Biology (GCB), “The impacts of increasing drought on forest dynamics, structure, and biodiversity.”  Your paper is one of 2016’s 15 most-downloaded, according to Web of Science®.”

The latest release represents a substantial revision of many parts of the code, in R studio: install.packages(‘gjam’) library(gjam)

On Thursday, December 8, Jim Vose, project leader of the U.S. Forest Service Integrated Forest Science accepted the Chief’s Award – one of the highest honors in the Forest Service — in the category of “Sustaining Forests and Grasslands.” Vose accepted as leader of a team that the award honored for “understanding the impacts of drought on the nation’s forests and grasslands: providing a scientific foundation for effective management responses.” read more… The National Assessment was led by Jim Vose, Jim Clark, Charlie…

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Probabilistic forecasts of species’ distributions, abundances, and traits require models that accommodate the joint distribution of species and attributes based on combinations of continuous and discrete observations, mostly zeros…  early view here, pdf here clarkms, appendixs1

The EnviBayes section of ISBA this year has granted two best posters awards at the ISBA World Conference in Forte Village (June 13th – 17th, Cagliari, Italy).  Joint Species distribution modeling: dimension reduction using Dirichlet processes by Daniel Taylor-Rodriguez, postdoc at the Department of Statistical Science Duke University, with Kimberly Kaufield from North Carolina State University, Erin Schliep of University of Missouri, James Clark and Alan Gelfand of Duke University. The paper is accepted at Bayesian Analysis, bayesanaly2016.

To understand the importance of analytical tools such as those provided by Berdanier et al. (2016) in this issue of Tree Physiology, one must understand both the grand challenges facing Earth system modelers, more…

Daniel Taylor-Rodriquez led this analysis and produced best poster, awarded by the Env Section of ISBA.ISBAposter2016

early view in Ecology Trait analysis aims to understand relationships between traits, species diversity, and the environment. Current methods could benefit from a model-based probabilistic framework that accommodates covariance between traits and quantifies contributions from inherent trait syndromes, species interactions, and responses to the environment… read more

Predicting whole-tree water use requires models that accommodate the variation in sap flux between wood types and by depth into the tree. We develop a method for scaling-up flux observations. As an illustrative example, we predict sap flux for a forest in North Carolina, quantifying changes in water use with tree species and size. We include computer software for generating whole-tree flow estimates with other observations in Excel® and the R programming language. treePhys_berdanier2016 treePhys_berdanier2016Suppl

10 things you may not have known about trees/forests

Three papers published, a fourth ready to submit, see Publications    

video coverage (go  to time 2:42 in this clip) Huffington Post Science360News weatherNewsNetwork UPI Christian Science Monitor    

Forests nationwide are feeling the heat from increasing drought and climate change, according to a new study by scientists from 14 research institutions… read more

full report … provides input to the reauthorized National Integrated Drought Information System (NIDIS) and the National Climate Assessment (NCA). Produced every 4 years, the NCA evaluates the effects of global climate change on forests, agriculture, rangelands, land and water resources, human health and welfare, and biological diversity, and it projects major trends.  press release  

Generalized Joint Attribute Modeling for R for jointly modeling species, traits, and other responses, see Code .

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The timing of the first leaves on trees and plants can make or break an agricultural season. Too early, and the leaves might be blasted by the last frost. Too late and they miss out on maximizing the growing season. But as climate change brings warmer-than-usual winters to the U.S., the plants may be more vulnerable to imprecise timing, and the tools traditionally used by farmers and horticulturists to predict the season may be inadequate. [more] In Red Orbit Clark,…

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