Effects of resource sharing directionality on physiologically integrated clones of the invasive Carpobrotus edulis

Aims One of the key traits associated with clonal growth in plants is the capacity for physiological integration, which allows resource sharing between connected ramets within a clonal system. Resource transport is expected to occur following a source–sink relationship: from ramets established in rich patches to ramets growing in poor patches. However, some experiments have shown that acropetal transport (from basal to apical modules) usually exceeds basipetal transport (from apical to basal ramets). In this study, we aimed to determine the resource transport directionality in physiologically integrated modules of the invader Carpobrotus edulis. Methods We conducted two manipulative experiments under common garden conditions that studied the effect of different nutrient levels located at different positions (basal, medial, apical) on connected and disconnected clonal systems of C. edulis. We compared the biomass partitioning patterns and final biomass of ramets to elucidate whether the effect of physiological integration is affected by the directionality of the resource transport. Important Findings Results indicate a prevalent acropetal transport of resources in C. edulis, with a developmentally-programmed division of labor where basal ramets were specialized in obtaining soil-based resources and apical ramets specialized in aboveground growth. This biomass-partitioning pattern was not affected by the nutrient conditions in which basal or apical ramets were growing, although the highest benefit was achieved by apical ramets growing under the most stressed conditions. This developmentally-programmed division of labor is expected to increase the lateral growth of C. edulis, and therefore could have meaningful implications for the expansion of this invasive species.

Interactions among rooting traits for deep water and nitrogen uptake in upland and lowland ecotypes of switchgrass (Panicum virgatum L.)

Plant phenotypic plasticity in response to nutrient and water availability is an important adaptation for abiotic stress tolerance. Roots intercept water and nutrients while foraging through soil searching for further resources. Substantial amounts of nitrate can leach into groundwater; yet, little is known about how deep rooting affects this process. Here, we phenotyped root system traits and deep 15N nitrate capture across 1.5 m profiles of solid-media using tall mesocosms in switchgrass (Panicum virgatum L.), a cellulosic bioenergy feedstock. Root and shoot biomass, photosynthesis and respiration, and nutrient uptake traits were quantified in response to a water and nitrate stress factorial experiment in the greenhouse for switchgrass upland (VS16) and lowland (AP13) ecotypes. The two switchgrass ecotypes shared common plastic abiotic responses to nitrogen (N) and water availability and yet showed genotypic differences for root and shoot traits. A significant interaction between nitrogen and water stress for axial and lateral root traits represents a complex and shared root development strategy for stress mitigation. Deep root growth and 15N capture were found to be closely linked to aboveground growth. Together, these results represent the wide genetic pool of switchgrass and that deep rooting promotes nitrate capture, plant productivity, and sustainability.HighlightTwo main ecotypes of switchgrass have both shared and different root responses to varying water and nitrogen conditions, with deep rooting shown to be closely linked to aboveground growth.

Effect of biochar amendment on the properties of growing media and growth of containerized Norway spruce, Scots pine, and silver birch seedlings

Common practices and several studies have demonstrated the positive effect of biochar amendment on climate change mitigation, soil properties, and plant growth. We performed a greenhouse experiment to assess the potential of wood biochar to improve the properties of the growing media and the growth of seedlings in boreal tree species. We added willow biochar (0%, 5%, 10%, and 20%) to raw peat and measured the growth of Norway spruce (Picea abies (L.) H. Karst.), Scots pine (Pinus sylvestris L.), and silver birch (Betula pendula Roth) seedlings. In addition, the co-effect of biochar amendment with 0%, 50%, and 100% fertilization was estimated. We found that using up to 10% of biochar did not reduce the water retention capacity of the growing media significantly. Moreover, biochar amendment significantly increased carbon, nitrogen, potassium, and phosphorus concentrations and had a significant liming effect on the growing media. The biochar amendment increased the aboveground growth of spruce seedlings and root biomass, as well as the root collar diameter, of birch seedlings. Biochar amendment did not affect the quality of seedlings, estimated by the Dickson’s quality index, for spruce and pine, while the quality of birch increased. Based on our results, biochar has potential in forest seedling production.