@article {KNZ001876, title = {Drivers of nocturnal water flux in a tallgrass prairie}, journal = {Functional Ecology}, volume = {32}, year = {2018}, pages = {1155-1167}, abstract = {

Nocturnal transpiration can impact water balance from the local community to earth-atmosphere fluxes. However, the dynamics and drivers of nocturnal transpiration among coexisting plant functional groups in herbaceous ecosystems are unknown.
Here, we addressed the following questions: (1) How do nocturnal (Enight) and diurnal (Eday) transpiration vary among coexisting grasses, forbs, and shrubs in a tallgrass prairie? (2) What environmental variables drive Enight and do these differ from the drivers of Eday? (3) Is Enight associated with daytime physiological processes?
We measured diurnal and nocturnal leaf gas exchange on perennial grass, forb and woody species in a North American tallgrass prairie. Measurements were made periodically across two growing seasons (May\–August 2014\–2015) on three C4 grasses (Andropogon gerardii, Sorghastrum nutans and Panicum virgatum), two C3 forbs (Vernonia baldwinii and Solidago canadensis), one C3 sub-shrub (Amorpha canescens) and two C3 shrubs (Cornus drummondii and Rhus glabra).
By extending our study to multiple functional groups, we were able to make several key observations: (1) Enight was variable among co-occurring plant functional groups, with the highest rates occurring in C4 grasses, (2) Enight and Eday exhibited different responses to vapour pressure deficit and other environmental drivers, and (3) rates of Enight were strongly related to predawn leaf water potential for grasses and woody species, and were likely modulated by small-scale changes in soil moisture availability.
Our results provide novel insight into an often-overlooked portion of ecosystem water balance. Considering the high rates of Enight observed in C4 grasses, as well as the widespread global occurrence of C4 grasses, nocturnal water loss might constitute a greater proportion of global evapotranspiration than previously estimated. Additionally, future predictions of nocturnal water loss may be complicated by stomatal behaviour that differs between the day and at night. Finally, these data suggest a water-use strategy by C4 grasses wherein the high rates of Enight occurring during wet periods may confer a competitive advantage to maximize resource consumption during periods of greater availability.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2435.13072}, url = {https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.13072}, author = {O{\textquoteright}Keefe, K. and Jesse B. Nippert}, editor = {Sala, Anna} } @article {KNZ001857, title = {Below-ground biological responses to pyrogenic organic matter and litter inputs in grasslands}, journal = {Functional Ecology}, volume = {31}, year = {2017}, pages = {260 - 269}, abstract = {

1. Terrestrial ecosystems are often burned by both managed and wildfires. During a fire, the above-ground biomass that would typically accumulate and be decomposed as litter on the soil surface is combusted. Pyrogenic organic matter (PyOM) remaining after a fire is a considerably more recalcitrant organic input to the soil than fresh litter. The activity and community composition of soil organisms responsible for decomposition of organic matter and nutrient recycling in the soil could thus be affected by altered resource availability caused by frequent fires.

2. We examined the effect of PyOM vs. fresh litter inputs to soil biota at both an annually burned and an infrequently burned tallgrass prairie site by tracing (13) C-and N-15-labelled litter and PyOM into growing plant roots, microbial phospholipid fatty acids (PLFAs) and soil nematodes for 1 year.

3. Litter-derived C or N was incorporated into microbes, nematodes and roots, while PyOM contributed minimally to soil microbes and plant roots and was not detectable in nematodes. Soil microbial and nematode abundances in the PyOM amended plots did not significantly differ from the bare soil plots, but nematodes were more abundant and microbial PLFAs less abundant in litter-amended plots. The annually burned site had less predator and omnivore nematodes, with increased abundance of microbial feeders and greater microbial uptake of litter C.

4. An alteration of the soil food web structure caused by burning and the removal of the litter layer, along with the accumulation of non-microbially decomposed PyOM in the soil, contributes to the limitation of N cycling in frequently burned ecosystems.

}, keywords = {LTER-KNZ, fire, litter decomposition, Nematodes, phospholipid fatty acid, pyrogenic organic matter, Stable isotopes, tallgrass prairie}, doi = {10.1111/fec.2017.31.issue-110.1111/1365-2435.12693}, author = {Soong, Jennifer L. and Dam, Marie and Wall, Diana H. and Cotrufo, M. Francesca}, editor = {Nicolson, Susan W. and Wright, Geraldine A. and Sala, Anna} }