Biology subjects

Duursma, R.

Publications and source records attributed to Duursma, R..

3 recordsLinked to original sources

bioRxiv2024

The global spectrum of tree crown architecture

Trees can differ enormously in their crown architectural traits, such as the scaling relationships that link their height and crown size to their stem diameter. Yet despite the importance of crown architecture in shaping the structure and function of woody ecosystems, we lack a complete picture of what drives this incredible diversity in crown shapes. Using data from >500,000 globally distributed trees, we explored how climate, disturbance, competition, functional traits, and evolutionary history constrain the height, crown size and shape of the worlds tree species. We found that variation in height scaling relationships was primarily controlled by water availability and light competition. Conversely, crown width was predominantly shaped by exposure to wind and fire, while also covarying with other functional traits related to mechanical stability and photosynthesis. Additionally, several plant lineages had crown architectures that defy their environments, such as the exceedingly slender dipterocarps of Southeast Asia, or the extremely wide crowns of legumes in African savannas. Our study charts the global spectrum of tree crown architectural types. It provides a roadmap for integrating crown architecture with vegetation models and remote sensing observations, so that we may better understand the processes that shape the 3D structure of woody ecosystems.

ecology↗

bioRxiv2021

Heat stress prevented the biomass and yield stimulation caused by elevated CO2 in two well-watered wheat cultivars

To investigate the interactive effects of elevated CO2 and heat stress (HS), we grew two contrasting wheat cultivars, early-maturing Scout and high-tillering Yitpi, under non-limiting water and nutrients at ambient (aCO2, 450 ppm) or elevated (eCO2, 650 ppm) CO2 and 22{degrees}C in the glasshouse. Plants were exposed to two 3-day HS cycles at the vegetative (38.1{degrees}C) and/or flowering (33.5{degrees}C) stage. At aCO2, both wheat cultivars showed similar responses of photosynthesis and mesophyll conductance to temperature and produced similar grain yield. Relative to aCO2, eCO2 enhanced photosynthesis rate and reduced stomatal conductance and maximal carboxylation rate (Vcmax). During HS, high temperature stimulated photosynthesis at eCO2 in both cultivars, while eCO2 stimulated photosynthesis in Scout. Electron transport rate (Jmax) was unaffected by any treatment. eCO2 equally enhanced biomass and grain yield of both cultivars in control, but not HS, plants. HS reduced biomass and yield of Scout at eCO2. Yitpi, the cultivar with higher grain nitrogen, underwent a trade-off between grain yield and nitrogen. In conclusion, eCO2 improved photosynthesis of control and HS wheat, and improved biomass and grain yield of control plants only. Under well-watered conditions, HS was not detrimental to photosynthesis or growth but precluded a yield response to eCO2. Key messageHigh temperatures increased photosynthetic rates only at eCO2 and photosynthesis was upregulated after recovery from heat stress at eCO2 in Scout suggesting that eCO2 increased optimum temperature of photosynthesis.

physiology↗

bioRxiv2016

Trajectories: how functional traits influence plant growth and shade tolerance across the life-cycle

Plant species differ in many functional traits that drive differences in rates of photosynthesis, biomass allocation, and tissue turnover. Yet, it remains unclear how - and even if - such traits influence whole-plant growth, with the simple linear relationships predicted by existing theory often lacking empirical support. Here we present a new theoretical framework for understanding the effect of diverse functional traits on plant growth and shade-tolerance, extending a widely-used theoretical model that links growth rate in seedlings with a single leaf trait to explicitly include influences of size, light environment, and five other prominent traits: seed mass, height at maturation, leaf mass per unit leaf area, leaf nitrogen per unit leaf area, and wood density. Based on biomass production and allocation, this framework explains why the influence of prominent traits on growth rate and shade tolerance often varies with plant size and why the impact of size on growth varies among traits. Considering growth rate in height, we find the influence of: i) leaf mass per unit leaf area is strong in small plants but weakens with size, ii) leaf nitrogen per unit leaf area does not change with size, iii) wood density is present across sizes but is strongest at intermediate sizes, iv) height at maturation strengthens with size, and v) seed mass decreases with size. Moreover, we show how traits moderate plant responses to light environment and also determine shade tolerance, supporting diverse empirical results. By disentangling the effects of plant size, light environment and traits on growth rates, our results provide a solid theoretical foundation for trait ecology and thus provide a platform for understanding growth across diverse species around the world.

ecology↗