Biology subjects

Franklin, O.

Publications and source records attributed to Franklin, O..

5 recordsLinked to original sources

bioRxiv2023

An eco-physiological model of forest photosynthesis and transpiration under combined nitrogen and water limitation

Although the separate effects of water and nitrogen (N) limitations on forest growth are well known, the question of how to predict their combined effects remains a challenge for modeling of climate change impacts on forests. Here, we address this challenge by developing a new eco-physiological model that accounts for plasticity in stomatal conductance and leaf N concentration. Based on an optimality principle, our model determines stomatal conductance and leaf N concentration by balancing carbon uptake maximization, hydraulic risk and cost of maintaining photosynthetic capacity. We demonstrate the accuracy of the model predictions by comparing them against gross primary production estimates from eddy covariance flux measurements and sap-flow scaled canopy transpiration in a long-term fertilized and an unfertilized Scots pine (Pinus sylvestris L.) forest in northern Sweden. The model also explains the response to N fertilization as a consequence of (i) reduced carbon cost of N uptake and (ii) increased leaf area per hydraulic conductance. The results suggest that leaves optimally coordinate N concentration and stomatal conductance both on short (weekly) time scales in response to weather conditions and on longer time scales in response to soil water and N availabilities.

ecology↗

bioRxiv2023

Competition for light can drive adverse species-composition shifts in the Amazon Forest under elevated CO2

The resilience of biodiverse forests to climate change depends on an interplay of adaptive processes operating at multiple temporal and organizational scales. These include short-term acclimation of physiological processes like photosynthesis and respiration, mid-term changes in forest structure due to competition, and long-term changes in community composition arising from competitive exclusion and genetic trait evolution. To investigate the roles of diversity and adaptation for forest resilience, we present Plant-FATE, a parsimonious eco-evolutionary vegetation model. Tested with data from a hyperdiverse Amazonian terra-firme forest, our model accurately predicts multiple emergent ecosystem properties characterizing forest structure and function. Under elevated CO2 conditions, we predict an increase in productivity, leaf area, and aboveground biomass, with the magnitude of this increase declining in nutrient-deprived soils if trees allocate more carbon to the rhizosphere to overcome nutrient limitation. Furthermore, increased aboveground productivity leads to greater competition for light and drives a shift in community composition towards fast-growing but short-lived species characterized by lower wood densities. Such a transition reduces the carbon residence time of woody biomass, dampening carbon-sink strength and potentially rendering the Amazon Forest more vulnerable to future climatic extreme events.

ecology↗

bioRxiv2022

Optimal balancing of xylem efficiency and safety explains plant vulnerability to drought

O_LIIn vast areas of the world, the growth of forests and vegetation is water-limited and plant survival depends on the ability to avoid catastrophic hydraulic failure. Therefore, it is remarkable that plants take high hydraulic risks by operating at water potentials ({psi}) that induce partial failure of the water conduits (xylem). Here we present an eco-evolutionary optimality principle for xylem conduit design that explains this phenomenon. C_LIO_LIBased on the hypothesis that conductive efficiency and safety are optimally co-adapted to the environment, we derive a simple relationship between the intrinsic tolerance to negative water potential ({psi}50) and the environmentally dependent minimum xylem{psi} . C_LIO_LIThis relationship is constrained by a physiological tradeoff between xylem conductivity and safety, which is relatively strong at the level of individual conduits although it may be weak at the whole sapwood level. The model explains observed variation in{psi} 50 both across a large number of species, and along the xylem path in two species. The larger hydraulic safety margin in gymnosperms compared to angiosperms is explained as an adaptation to the gymnosperms lower capacity to recover from conductivity loss. C_LIO_LIThe constant xylem safety factor provides a powerful principle for simplifying and improving plant and vegetation models. C_LI

plant biology↗

bioRxiv2020

Moose or spruce: A systems analysis model for managing conflicts between moose and forestry in Sweden

Sweden has the worlds highest density of moose (Alces alces). Moose is not only a valuable game species; it also causes forest damages and traffic accidents. To avoid moose browsing, foresters respond by planting spruce (Picea abies) to an extent that reshapes the forest landscape with impacts on both production and biodiversity. To address this problem and maintain a healthy moose population in balance with the other interests, an adaptive management based on the knowledge and experiences of local hunters and landowners is advocated. However, the different stakeholders do not agree on what is an appropriate moose population, which leads to conflicts that are hard to resolve. A key problem is that it is very difficult to encompass and foresee long-term consequences of different options for moose hunting and forest management. This makes it challenging to form coherent strategies that integrate different sectorial interests at a national level. To address this issue, we have developed a systems analysis framework for integrated modeling of the moose population, forestry, and their interactions and consequences for biodiversity. We analyze the short and long-term consequences for multiple scenarios of moose hunting and forest management. Based on the results we elucidate and quantify the trade-offs and possible synergies between moose hunting and forest production. This analysis can be used to support better informed and more constructive discussions among the stakeholders in the Swedish forest sectors, and to support policies for long term sustainable forest and moose management.

ecology↗

bioRxiv2020

Modeling Risks and Mitigation Options for the Chronic Wasting Disease (CWD) in Scandinavia

Chronic wasting disease (CWD) is a contagious neural prion-disease affecting deer populations in North America with severe ecological and societal consequences. CWD is fatal and infectious prions spread and remain in the environment for many years even without animals present. The recent appearance of CWD in reindeers in Norway called for a drastic culling operation to prevent further spreading of the disease. This appears to have stopped the spreading of CWD among reindeers, but due to the persistence of CWD prions in the environment a reappearance of new cases among reindeer or other species in the future cannot be excluded. To evaluate the risks and the effectiveness of alternative management (monitoring and culling) options, we developed a model of CWD dynamics and management. The model includes stochastic population and spatial dynamics of the four relevant deer species in northern Sweden and Norway: reindeer (Rangifer tarandus), roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces). Transmission of CWD is modelled via direct contacts and via the environment. The model was parameterized and calibrated based on CWD studies from USA, data from the Norwegian CWD cases, and local deer population and vegetation data. The results indicate that without management, a CWD epidemic can be initiated by a single infected reindeer and would spread to other deer species. It would lead to dramatic population declines of reindeer and red deer and would also reduce the populations of roe deer and moose. The disease prevalence would stabilise at a about 50% after 50 years, as observed in some areas in the USA. A management strategy to cull only visibly sick animals, even with very efficient detection, cannot prevent a catastrophic development but merely slow the outbreak. To prevent an outbreak and the establishment of CWD it is necessary to cull all individuals, not only visibly sick ones, of an affected species in a relatively large area (30x30 km in our model) once a case is detected. Further, to prevent a slow buildup of CWD in the environment and eliminate the risk of outbreaks in the future it is necessary to expand this area of culling even further. Although the model has not yet been thoroughly validated due to scarcity of data, the results suggest that the drastic culling done in Norway was appropriate and necessary to prevent establishment of CWD and that further monitoring and potential culling is required to prevent outbreaks in the future.

ecology↗