Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales ...

Background Under field conditions, the development of crops depends on capacity of the canopy to intercept incident radiation and convert it into new biomass (Gifford et al. 1984). The amount of incident radiation intercepted depends on the leaf area index (LAI) and canopy orientation in space. The fraction of the incident photosynthetically active radiation (IPAR) that is absorbed by a canopy ...

Simulations of the different components of the spectral radiation budget of structurally simple leaf and shoot canopies with varying canopy leaf area index (LAI) were performed. The aims were (1) to test a proposed parameterization of the budget using two spectrally invariant canopy structural parameters ( p and pt) governing canopy absorption and transmittance, respectively, and (2) to incorpo...

Leaf quantity (i.e., canopy leaf area index, LAI), quality (i.e., per-area photosynthetic capacity), and longevity all influence the photosynthetic seasonality of tropical evergreen forests. However, these components of tropical leaf phenology are poorly represented in most terrestrial biosphere models (TBMs). Here, we explored alternative options for the representation of leaf phenology effect...

Leaf mass per area (LMA, g m(-2)) is an essential trait for modeling canopy function due to its strong association with photosynthesis, respiration and leaf nitrogen. Leaf mass per area, which is influenced by both leaf thickness and density (LMA = thickness × density), generally increases from the bottom to the top of tree canopies, yet the mechanisms behind this universal pattern are not yet ...

Leaf life span is an important plant trait associated with interspecific variation in leaf, organismal, and ecosystem processes. We hypothesized that intraspecific variation in gymnosperm needle traits with latitude reflects both selection and acclimation for traits adaptive to the associated temperature and moisture gradient. This hypothesis was supported, because across 127 sites along a 2,16...

Canopy temperature is a useful indicator of crop water stress and can also be used for making timely irrigation scheduling decisions for center pivot and subsurface drip irrigation systems. However, it is not known how closely the measured canopy temperature from a circular area of the canopy surface compares with a larger continuous area that includes the full canopy width. A study was conduct...

The geologic history of closed-canopy forests is of great interest to paleoecologists and paleoclimatologists alike. Closed canopies have pronounced effects on local, continental and global rainfall and temperature patterns. Although evidence for canopy closure is difficult to reconstruct from the fossil record, the characteristic isotope gradients of the “canopy effect” could be preserved in l...

In June 1993, net photosynthetic rates, stomatal conductance and isoprene emission rates of sweetgum leaves (Liquidambar styraciflua L.) were measured at the top of the forest canopy (sun leaves) and within the canopy at a height of 8-10 m above ground level (shade leaves). Large differences in net photosynthetic rates and stomatal conductance were found between sun and shade leaves. Mean rates...

through a model of stomatal conductance Jinzhi Wang Introduction I came to CGREC on May 7, 2008 to work under the direction of Dr. Xuejun Dong, eco-physiologist at the Center. His work involves the relationship between environmental factors (precipitation, temperature, and radiation) and soil respiration and plant physiology (leaf photosynthetic rates and leaf area index) of dominant species. O...