Activity of soil dehydrogenase (DHA) was measured in the mineral soil in a forest stand of 15 to 16-year-old Scots pine (Pinus sylvestris L.) from geographically diverse populations, as an indicator of biological activity of soil microorganisms, in a provenance experiment in Poland. The pine populations originated from six European countries (Sweden, Russia, Latvia, Poland, Germany, France) and differed widely in aboveground biomass and productivity. Soil DHA during two growing seasons showed pronounced seasonal variability, which was significantly related to the fine root concentration of nonstructural carbohydrates. Higher DHA was found in soil under canopies of the central and southern European populations than in those from more northern parts of the Scots pine range. Significant positive correlation between soil DHA and aboveground tree biomass suggest that these patterns most likely resulted from differences in carbon dynamics and productivity among populations.
We explored changes in growth, phenology, net CO₂ assimilation rate, water use efficiency, secondary defense compounds, substrate and foliage nutrient concentration of a degraded urban horse chestnut (Aesculus hippocastanum L.) site restored for three years using mulching (tree branches including foliage) and fertilization (primarily nitrogen addition). Prior to restoration, this site was characterized by high pH (ca. 8), low foliage and substrate N, and high Na and Cl concentration. Our data indicated that in untreated plots NaCl used for road deicing is the decisive factors that may be responsible for the decrease of foliar N concentration (via a reduction in NO₃⁻ uptake), for the decrease in photosynthesis (through high concentrations of Na and Cl in the leaves) and for increased senescence of the leaves. After three years of treatment, total nitrogen concentration in substrate increased by 3- to 4-fold and calcium concentration decreased by more than 50% in relation to pretreatment levels. Treatment significantly increased seed production (from less than 12 to more than 100 seeds per tree), individual leaf mass (from 1.8 to 3.3 g/leaf), CO₂ assimilation rate (by 21 to 30 %), improved leaf C:N ratio, and increased foliage life span by as much as six weeks. The beginning of leaf fall in untreated control trees started in midJuly and those of mulched and fertilized trees in late October. Applied treatment also eliminated visible symptoms of leaf damage due to high sodium and chlorine levels, indicating the possible role of other factors in the development of necroses. After three years of treatment, pH of most degraded plots declined from 8.2 to 7.8. That decline was accompanied by an increase in foliar Zn, Cu, and Pb concentration in the mulched and fertilized plants. In addition, treatment lowered foliage phenolics making these plants potentially more vulnerable to insect herbivory. Our study indicates that stable carbon isotope discrimination is of little value as an indicator of cumulative salinity and urban environment stress in A. hippocastanum due to pronounced differences in leaf phenology and ontogeny. The results of our study show that street tree recovery can take as little as two to three years after application of fertilization and mulching.
Root distribution sampling techniques are often inaccurate, time consuming and costly. We present an inexpensive approach to soil profile-wall mapping using a desktop scanner that allowed us to spend reduced time in the field. The scanner was pressed onto the vertical surface of a 1 x 1 m soil pit and images of the roots were taken in situ. In a common garden planting of eleven, 30-year-old conifer and hardwood tree species in Poland, we compared root counts (number of roots cm–2) obtained by this method with independent measurements of root length density (RLD) obtained from soil cores. We found a positive correlation (Spearman rank correlation r=0.93; P<0.001) suggesting general agreement of the two approaches in ranking among the species. Soil coring as well as grid mapping with plastic overlays took a longer total time for quantifying root distribution than the scanning procedure. The desktop scanner approach we developed is an inexpensive, time efficient and accurate way of quantifying root distribution and abundance that allows a unique coupling of root data to soil properties.