Just How Does Nitrogen Drive Change in Plant Communities?

Nitrogen enrichment can dramatically change the existing environment for plants and typically leads to increased productivity, decresed diversity, and shifts plant community composition. But what mechanisms are responsible for these changes? Researchers designed a multi-site experiment to find out, experimentally manipulating each of three possible drivers across mesocosms of three ecosystem types (tall grass prairie, alpine tundra, and desert grassland).

Winter Conditions Vital to Year-Round Lake Dynamics

This month’s Ecology Letters features the first global quantitative synthesis of under-ice lake ecology. In their analysis of 36 abiotic and biotic variables across 101 lakes, the authors issue a call to arms for more winter lake research—currently the focus of only 2% of freshwater publications. As the climate warms, they warn, temperate ecosystems are losing ice, and limnologists remain unsure what ecological processes are at stake. Though winter has long been understood as an inactive period, some data suggests that winter foodwebs and physical processes remain vigorous and that winter ecology can drive subsequent summer conditions.

Growing Grass: A Story of Nitrogen, Phosphorus, and Leaf Size

Ecologists know that nitrogen, phosphorus and leaf area play key roles in the productivity of plant communities. But how tightly are they tied together? And are those relationships sustained over different types of landscapes? A recent study of tallgrass prairie communities, building on a previous study of arctic tundra, found leaf area index (LAI) to be strongly correlated to both total foliar nitrogen and total foliar phosphorus in several plant functional types (grass, forb, woody, and sedge) and grazing treatments (cattle, bison, and ungrazed).

Finding the Hidden Phytoplankton Blooms

In stratified lakes, a large portion of phytoplankton biomass is found—not at the surface, where sampling is easiest—but somewhere down the water column, in what is known as a subsurface chlorophyll maximum (SSCM). Researchers in Global Lake Ecological Observatory Network (GLEON) compared automated high-frequency chlorophyll fluorescence (ChlF) profiles with surface samples and discrete depth profiles. In 7 of the 11 lakes studied, automated sampling captured the presence of SSCM’s that would have been missed by conventional sampling.

What (and when) is the point-of-no-return?

How-and when-do ecosystems change character? Are those shifts reversible? And what signs might precede them? Such questions are hard enough to answer in a single place. One might think that incorporating different kinds of ecosystems would only complicate the problem. But a group of scientists in the Long-Term Ecological Research Network is finding a remarkably consistent pattern by combining models and data across several long-term ecological experiments.

Cold Air Drainage Flows Subsidize Montane Valley Ecosystem Productivity

Landscape ecologists and nature-lovers are well aware of the way that valleys collect deeper, moister soils than neighboring hill slopes and crests. Now, researchers at Coweeta LTER have have found that cool air, sliding downslope from higher elevations and pooling in mountain valleys, subsidizes productivity in a different way. The cold air drainage was most prevalent at night and in the evenings, so it had little effect on photosynthesis, but reduced plant and soil respiration by about 8 percent. Overall, the authors estimate it boosted annual net carbon uptake by about 15 percent.

PhysFest: the “Un-Meeting”

PhysFest participants measure gas exchange on an annually-burned watershed. On June 5th, 45 plant eco-physiologists traveled to Kansas from all corners of the country to take part in the inaugural PhysFest. This “un-meeting,” held at the Konza Prairie Biological Station and LTER Site and hosted by the Kansas State Plant EcoPhys Lab, aimed to break all… Read more »

2015 LTER Mini-Symposium talks available for viewing and download

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Early this year the annual Long Term Ecological Research (LTER) Mini-Symposium scheduled for Thursday, March 5, 2015, had to be postponed when inclement weather forced the closure of the National Science Foundation (NSF) (see http://bit.ly/1NkuT9Q). At the time we reported that webcasts of the talks would be presented in blocks of two or three at… Read more »