Growth Allocation Patterns Research Articles

The responses of shoot-root-rhizosphere continuum to simultaneous fertilizer addition, warming, ozone and herbivory in young Scots pine seedlings in a high latitude field experiment

It is not clear how climate change in combination with increasing soil nitrogen availability and herbivory affects boreal forests, the largest terrestrial biome in the world. In this study, Scots pine (Pinus sylvestris) seedlings were exposed to moderate warming (ca. 1 °C), 1.5 × ambient ozone (O3) concentration, fertilizer addition (120 kg N ha−1 yr−1) and shoot herbivory by pine sawfly (Acantholyda posticalis) alone and in combination. We measured fine root morphology, mycorrhizal colonization level, root fungal biomass (ergosterol), rhizosphere emission of biogenic volatile organic compounds (BVOCs), and microbial biomass (PLFAs) in the rhizosphere soil as well as seedling above- and below-ground growth. Warming and fertilization effects on fine root proportions or root fungal biomass occurred in combination with other factors, combination effects being usually negative on the studied variables, or then warming and fertilization in combination cancelled some other factors’ effects. O3 effects on needle growth, root fungal biomass and BVOCs were more often seen after the third exposure year, and sometimes only in combination with other studied factors. Of abiotic factors, fertilizer addition had reducing effect on rhizosphere BVOCs. Though increased nitrogen availability and warming increased both shoot and root dry masses, growth allocation to above- and below-ground parts was not equally increased in the combined exposures. Thus, we conclude that climate change factors together with increased nitrogen availability and herbivory are likely to affect the below-ground compartments negatively, more often than shoots, and ultimately change in growth allocation pattern which may affect overall seedling growth and survival in later years.

Long-term differential stem growth responses in mature eastern white pine following release from competition

The magnitude and duration of the growth response in residual trees following silvicultural release treatments are measures used to assess the success of silvicultural practices. Eighty-eight eastern white pine (Pinus strobus L.) trees, representing three different dominance classes, were sampled destructively from stands from a single study site that included areas of both unharvested (control) and silvicultural release treatments. The study area consisted of several pine mixedwood stands with understory white pine growing in association with an overstory of predominantly intolerant hardwoods. Annual height, diameter, basal area, stem and sawtimber volume increment, pattern of stem increment allocation along the bole, stem form, and height–diameter ratio were reconstructed over a postrelease period of 23 years using detailed stem analysis. Within 3 years of release, white pine in all dominance classes showed significant increases in diameter, basal area, and volume increment compared with control trees. Differences in the volume increment between released and control trees varied with canopy position, with emergent trees showing the greatest increased volume growth, followed by dominant and intermediate classes, respectively. A temporary shift in the growth allocation pattern along the bole varied depending on crown class, suggesting a period of growth adjustment during which trees are acclimating to changes in resource availability and wind exposure. The shift in growth allocation contributed to increased stem taper, resulting in decreased form class and height–diameter ratios in the released trees.

Inter‐individual differences in rates of routine energy loss and growth in young‐of‐the‐year juvenile Atlantic cod

Inter‐individual differences in rates of routine (non‐feeding) metabolism and growth were evaluated in young‐of‐the‐year (YOY) juvenile Atlantic cod Gadus morhua. Rates of O2 consumption, CO2 production and ammonia (TAN) excretion were measured in 64, 25–43 mm standard length (LS) YOY growing at different rates (0·27–0·47 mm day−1) in a common rearing tank. Parameter rates (y) increased allometrically (y = a·Mb) with increasing body mass (M) with b‐values for O2 production, CO2 consumption and TAN excretion equal to 0·81, 0·89 and 0·56, respectively. In some cases, residuals from these regressions were significantly negatively correlated to fish growth rate. In no cases did residuals of parameter rates increase with increasing growth rate. These data suggest that, during unfed periods, relatively fast‐growing fish were more metabolically efficient than slower‐growing fish from the same cohort. The fish condition factor, derived from , also significantly decreased with increasing growth rate. Results indicated differences in both the rates of routine energy loss and the patterns of growth allocation among YOY Atlantic cod. Since these physiological attributes were positively correlated with growth rate, they may be indicative of ‘survivors’ in field populations.