The amount of parenchyma and living fibers affects storage of non-structural carbohydrates in young stems and roots of temperate trees

PREMISE OF THE STUDY: Concentrations of nonstructural carbohydrates (NSCs) are used as proxies for the net carbon balance of trees and as indicators of carbon starvation resulting from environmental stress. Woody organs are the largest NSC-storing compartments in forest ecosystems; therefore, it is essential to understand the factors that affect the size of this important storage pool. In wood, NSC are predominantly deposited in ray and axial parenchyma (RAP); however, direct links between nutrient storage and RAP anatomy have not yet been established. Here, we tested whether the NSC storage capacity of wood is influenced by the amount of RAP. METHODS: We measured NSC concentrations and RAP fractions in root and stem sapwood of 12 temperate species sampled at the onset of winter dormancy and in stem sapwood of four tropical trees growing in an evergreen lowland rainforest. The patterns of starch distribution were visualized by staining with Lugol’s solution. KEY RESULTS: The concentration of NSCs in sapwood of temperate trees scales tightly with the amount of RAP and living fibers (LFs), with almost all RAP and LFs being densely packed with starch grains. In contrast, the tropical species had lower NSC concentrations despite their higher RAP and LFs fraction and had considerable interspecific differences in starch distribution. CONCLUSIONS: The differences in RAP and LFs abundance affect the ability of sapwood to store NSC in temperate trees, whereas a more diverse set of functions of RAP might be pronounced in species growing in a tropical environment with little seasonalit

Land use change impacts on floods at the catchment scale : challenges and opportunities for future research

Research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage, and terracing are identified. Potential strategies in addressing these gaps are proposed, such as complex systems approaches to link processes across time scales, long-term experiments on physical-chemical-biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology, and geomorphology. Plain Language Summary This commentary explores research gaps in the field of land use change impacts on floods at the catchment scale and proposes possible ways forward for addressing these gaps. Specifically the impacts of forest management, agricultural practices, artificial drainage, and terracing on flood generation at the catchment scale are explored. Potential strategies in addressing research gaps in these fields are complex systems approaches to link processes across time scales, long-term experiments on physical-chemical-biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology, and geomorphology

Xylem embolism refilling and resilience against drought-induced mortality in woody plants: processes and trade-offs

Understanding which species are able to recover from drought, under what conditions, and the mechanistic processes involved, will facilitate predictions of plant mortality in response to global change. In response to drought, some species die because of embolism-induced hydraulic failure, whilst others are able to avoid mortality and recover, following rehydration. Several tree species have evolved strategies to avoid embolism, whereas others tolerate high embolism rates but can recover their hydraulic functioning upon drought relief. Here, we focus on structures and processes that might allow some plants to recover from drought stress via embolism reversal. We provide insights into how embolism repair may have evolved, anatomical and physiological features that facilitate this process, and describe possible trade-offs and related costs. Recent controversies on methods used for estimating embolism formation/repair are also discussed, providing some methodological suggestions. Although controversial, embolism repair processes are apparently based on the activity of phloem and ray/axial parenchyma. The mechanism is energetically demanding, and the costs to plants include metabolism and transport of soluble sugars, water and inorganic ions. We propose that embolism repair should be considered as a possible component of a \u2018hydraulic efficiency-safety\u2019 spectrum. We also advance a framework for vegetation models, describing how vulnerability curves may change in hydrodynamic model formulations for plants that recover from embolism