Nutrient-Induced Modifications of Wood Anatomical Traits of Alchornea lojaensis (Euphorbiaceae)

Abstract

Regarding woody plant responses on higher atmospheric inputs of the macronutrients nitrogen (N) and phosphorous (P) on tropical forests in the future, an adaptive modification of wood anatomical traits on the cellular level of woody plants is expected. As part of an interdisciplinary nutrient manipulation experiment (NUMEX) carried out in Southern Ecuador, we present here the first descriptive and quantitative wood anatomical analysis of the tropical evergreen tree species Alchornea lojaensis (Euphorbiaceae). We sampled branch wood of nine individual trees belonging to treatments with N fertilization, N+P fertilization, and a control group, respectively. Quantitative evaluations of eleven different vessel parameters were conducted. The results showed that this endemic tree species will be able to adapt well to the future effects of climate change and higher nutrient deposition. This was firstly implied by an increase in vessel diameter and consequently a higher theo. area-specific hydraulic conductivity with higher nutrient availability. Secondly, the percentage of small vessels (0-20 µm diameter) strongly increased with fertilization. Thirdly, the vessel arrangement (solitary vessels vs. multiple vessel groupings) changed toward a lower percentage of solitary vessel fraction (V S ), and concurrently toward a higher total vessel grouping index (V G ) and a higher mean group size of non-solitary vessels (V M ) after N and N+P addition. We conclude that higher nutrient availability of N and N+P triggered higher foliage amount and water demand, leading to higher cavitation risk in larger vessels. This is counteracted by a stronger grouping of vessels with smaller risk of cavitation to ensure water supply during drier periods that are expected to occur in higher frequency in the near future.

Two Dominant Herbaceous Species Have Different Plastic Responses to N Addition in a Desert Steppe

“…Leaf anatomical structure was evaluated via paraffin sectioning of tissues and light microscopy observations/methods ( Spannl et al, 2016 ). We selected fully expanded sun leaves from five randomly selected plants of each species.…”

Growth, hydraulics and functional traits of Melia dubia across a steep climatic gradient in southern India

“…The higher AGBI on soils with a high P content was accompanied by an increase in stem vessel diameter and reductions in branch and stem vessel density. This is consistent with the described increase in vessel diameter with nutrient availability, mainly nitrogen (Hacke et al 2010;Plavcová et al 2013;Spannl et al, 2016) and may reflect a shift to a more efficient xylem anatomy precipitated by the more favorable nutrient availability (Goldstein et al, 2013;. Most likely, nutrients alter wood anatomical and hydraulic traits due to their link to growth rates (Ewers et al, 2001;Phillips et al, 2001;Giardina et al, 2003;Amponsah et al 2004;Lovelock et al, 2004;Bucci et al, 2006;B´aez and Homeier, 2018).…”

Hydraulic tradeoffs underlie local variation in tropical forest functional diversity and sensitivity to drought

“…2a). These modifications should produce less water‐demanding xylem architectures (Tyree & Zimmermann, 2002), create alternative pathways for water transport, bypassing embolized vessels (von Arx et al ., 2013; Spannl et al ., 2016), and reinforce the xylem under strongly negative water potentials (Hacke et al ., 2001). Hydraulic efficiency, in turn, seems to be achieved by invariably large and solitary vessels, reflecting more suitable phenotypes to wet sites.…”