Search for: All records

Diurnal branch movements in woody plants have only recently been described in detail. While previously only vegetative and reproductive structures have been known to move on hourly timescales, imaging technologies such as terrestrial laser scanning and near‐surface repeat digital photography provide a means of remotely monitoring plant movements at high enough temporal and spatial resolution to capture rhythmic movements of woody material. Virtually, nothing is known about the range of species and ecosystems in which woody movements might occur or what causes these movements. We report that diurnal woody branch movements occur in a number of tree and shrub species across a broad range of abiotic conditions. We examined detailed branch movements in one species, creosote (Larrea tridentata), and found that branch movements were highly correlated with humidity, air temperature, vapor pressure deficit, and stem water potential: all factors related to plant water status. We also found that live and dead branch movements were distinct in the timing of their movements and in the abiotic conditions with which they were most correlated. Changes in dead branch position were most correlated with humidity, with these movements consistently lagging 1–2 h behind changes in humidity. Live branch movements were also highly correlated with vapor pressure deficit and humidity but went from lagging 1–2 h behind changes in these abiotic conditions in summer to being nearly in sync in winter. We believe that this is the first study that (1) documents diurnal branch movements in creosote, (2) differentiates between the movements of live and dead branches, and (3) relates environmental data to these movements. We hope these findings encourage other researchers to more closely examine imagery from their sites for evidence of branch movements, which may provide deeper insights into water and solute movements in plants and physiological responses to water stress.

 

Patterns of plant biomass partitioning are fundamental to estimates of primary productivity and ecosystem process rates. Allometric relationships between aboveground plant biomass and non-destructive measures of plant size, such as cover, volume, or stem density are widely used in plant ecology. Such size-biomass allometry is often assumed to be invariant for a given plant species, plant functional group, or ecosystem type. Allometric adjustments may be an important component of the short- or long-term responses of plants to abiotic conditions. We used 18 years of size-biomass data describing 85 plant species to investigate the sensitivity of allometry to precipitation, temperature, or drought across two seasons and four ecosystems in central New Mexico, USA. Our results demonstrate that many plant species adjust patterns in the partitioning of aboveground biomass under different climates and highlight the importance of long-term data for understanding functional differences among plant species. 

Macrosystem‐scale research is supported by many ecological networks of people, infrastructure, and data. However, no network is sufficient to address all macrosystems ecology research questions, and there is much to be gained by conducting research and sharing resources across multiple networks. Unfortunately, conducting macrosystem research across networks is challenging due to the diversity of expertise and skills required, as well as issues related to data discoverability, veracity, and interoperability. The ecological and environmental science community could substantially benefit from networking existing networks to leverage past research investments and spur new collaborations. Here, we describe the need for a “network of networks” (NoN) approach to macrosystems ecological research and articulate both the challenges and potential benefits associated with such an effort. We describe the challenges brought by rapid increases in the volume, velocity, and variety of “big data” ecology and highlight how a NoN could build on the successes and creativity within component networks, while also recognizing and improving upon past failures. We argue that a NoN approach requires careful planning to ensure that it is accessible and inclusive, incorporates multimodal communications and ways to interact, supports the creation, testing, and promulgation of community standards, and ensures individuals and groups receive appropriate credit for their contributions. Additionally, a NoN must recognize important trade‐offs in network architecture, including how the degree of centralization of people, infrastructure, and data influence network scalability and creativity. If implemented carefully and thoughtfully, a NoN has the potential to substantially advance our understanding of ecological processes, characteristics, and trajectories across broad spatial and temporal scales in an efficient, inclusive, and equitable manner.

 

Reordering of dominant species is an important mechanism of community response to global environmental change. We asked how wildfire (apulseevent) interacts with directional changes in climate (environmentalpresses) to affect plant community dynamics in a Chihuahuan Desert grassland.

Sevilleta National Wildlife Refuge, Socorro County, New Mexico, USA.

Vegetation cover by species was measured twice each year from 1989 to 2019 along two permanently located 400‐m long line intercept transects, one in Chihuahuan Desert grassland, and the second in the ecotone between Chihuahuan Desert and Great Plains grasslands. Trends in community structure were plotted over time, and climate sensitivity functions were used to predict how changes in the Pacific Decadal Oscillation (PDO) affected vegetation dynamics.

Community composition was undergoing gradual change in the absence of disturbance in the ecotone and desert grassland. These changes were related to the reordering of abundances between two foundation grasses,Bouteloua eriopodaandB. gracilis, that together account for >80% of above‐ground primary production. However, reordering varied over time in response to wildfire (apulse) and changes in the PDO (apress). Community dynamics were initially related to the warm and cool phases of the PDO, but in the ecotone these relationships changed following wildfire, which reset the system.

Species reordering is an important component of community dynamics in response to ecological presses. However, reordering is a complex, non‐linear process in response to ecological presses that may change over time and interact with pulse disturbances.

 

Primary production, a key regulator of the global carbon cycle, is highly responsive to variations in climate. Yet, a detailed, continental‐scale risk assessment of climate‐related impacts on primary production is lacking. We combined 16 years of MODIS NDVI data, a remotely sensed proxy for primary production, with observations from 1218 climate stations to derive values of ecosystem sensitivity to precipitation and aridity. For the first time, we produced an empirically‐derived map of ecosystem sensitivity to climate across the conterminous United States. Over this 16‐year period, annual primary production values were most sensitive to precipitation and aridity in dryland and grassland ecosystems. Century‐long trends measured at the climate stations showed intensifying aridity and climatic variability in many of these sensitive regions. Dryland ecosystems in the western US may be particularly vulnerable to reductions in primary production and consequent degradation of ecosystem services as climate change and variability increase in the future.

 

Patterns of plant biomass partitioning are fundamental to estimates of primary productivity and ecosystem process rates. Allometric relationships between above‐ground plant biomass and non‐destructive measures of plant size, such as cover, volume or stem density are widely used in plant ecology. Such size‐biomass allometry is often assumed to be invariant for a given plant species, plant functional group or ecosystem type.

Allometric adjustment may be an important component of the short‐ or long‐term response of plants to abiotic conditions. We used 18 years of size‐biomass data describing of 85 plant species to investigate the sensitivity of allometry to precipitation, temperature or drought across two seasons and four ecosystems in central New Mexico, USA.

Size‐biomass allometry varied with climate in 65%–70% of plant species. Closely related plant species had similar sensitivities of allometry to natural spatiotemporal variation in precipitation, temperature or drought. Annuals were less sensitive than perennials, and forbs were less sensitive than grasses or shrubs. However, the differences associated with plant life history or functional group were not independent of plant evolutionary history, as supported by the application of phylogenetically independent contrasts.

Our results demonstrate that many plant species adjust patterns in the partitioning of above‐ground biomass under different climates and highlight the importance of long‐term data for understanding functional differences among plant species.

A freePlain Language Summarycan be found within the Supporting Information of this article.