Superoxide dismutase (SOD) activity and parameters of chlorophyll fluorescence, the ratio of maximal to variable fluorescence (Fv/Fm), maximal fluorescence (Fm), and minimal fluorescence (F0) were determined on Picea abies growing at different altitudes. The decreases of Fv/Fm and Fm, in comparison to samples from the lower stands (control), were found on trees from the highest stands. The decrease of fluorescence parameters was reversible, at least partly, after keeping branches for some days in the laboratory. Fv/Fm measured in spring when trees were partially covered with snow revealed greater degree of photoinactivation in branches collected from above the snow in comparison to those from below the snow. In samples collected from above snow also slower recovery from stress was observed. Two main SOD isoforms were determined in needles of P. abies, and classified as CuZnSODs. The activity of both SOD isoforms was increasing with the altitude, thus indicating the highest level of oxidative stress at the timberline zone. and Z. Miszalski ... [et al.].
The extent (determined by the repellency indices RI and RIc) and persistence (determined by the water drop penetration time, WDPT) of soil water repellency (SWR) induced by pines were assessed in vastly different geographic regions. The actual SWR characteristics were estimated in situ in clay loam soil at Ciavolo, Italy (CiF), sandy soil at Culbin, United Kingdom (CuF), silty clay soil at Javea, Spain (JaF), and sandy soil at Sekule, Slovakia (SeF). For Culbin soil, the potential SWR characteristics were also determined after oven-drying at 60°C (CuD). For two of the three pine species considered, strong (Pinus pinaster at CiF) and severe (Pinus sylvestris at CuD and SeF) SWR conditions were observed. Pinus halepensis trees induced slight SWR at JaF site. RI and RIc increased in the order: JaF < CuF < CiF < CuD < SeF, reflecting nearly the same order of WDPT increase. A lognormal distribution fitted well to histograms of RIc data from CuF and JaF, whereas CiF, CuD and SeF had multimodal distributions. RI correlated closely with WDPT, which was used to develop a classification of RI that showed a robust statistical agreement with WDPT classification according to three different versions of Kappa coefficient.
To uncover adaptation capacities of two flooding-tolerant plant species, Pterocarya stenoptera (a native species) and Pinus elliottii (an exotic species from southeastern USA), to alternating submergence and drought, we investigated their physiological and growth responses to water stress. Water treatments, including control, continuous flooding (CF), and periodic flooding and drought (PF), were applied to seedlings in order to simulate water level fluctuation in the hydrofluctuation zone of the Three Gorges Reservoir Region. Results showed that net photosynthetic rate (P N), stomatal conductance, and intrinsic water-use efficiency of both plant species were negatively affected under CF and PF compared with the corresponding controls. The P N of both species under PF was comparable to that under CF. At the end of the experiment, the ratio of intercellular to ambient CO2 concentration was not statistically different between water treatments, while that of P. elliottii was significantly higher than that of P. stenoptera. Although P. stenoptera formed lenticels under flooding conditions, P. elliottii seedlings allocated more mass to leaves and increased the relative growth rate of height to enhance the photosynthetic efficiency. Our results illustrated that P. stenoptera and P. elliottii seedlings developed different adaptive strategies in response to flooding, both CF and PF. Therefore, both P. stenoptera and P. elliottii are promising candidates for the vegetation reconstruction of the riparian zones in the Three Gorges Reservoir Region., Y. Yang, C. Li., and Obsahuje seznam literatury
The purpose of this study was to assess how terracing affected overland flow and associated sediment losses, at the micro-plot scale (0.25 m2 ), in recently burnt stands of the two principal forest types in north-central Portugal, i.e. mono-specific stands of Maritime Pine and Eucalypt. Terracing is an increasingly common practice of slope engineering in the study region but its impacts on runoff and erosion are poorly studied. Non-terraced plots at the Eucalypt and the Pine site revealed similar median runoff coefficients (rc: 20-30%) as well as comparable median sediment losses (15-25 g m-2 ) during the first seven months following wildfire. During the ensuing, slightly wetter 18-month period, however, non-terraced plots at the Pine site lost noticeably more sediments (in median, 90 vs. 18 g m-2 ), in spite the runoff response had remained basically the same (median rc: 33 vs. 28%). By contrast, terraced plots at the same Pine site lost hugely more sediments (in median, 1,200 g m-2 ) during this 18-month period. Terraced plots at the Eucalypt site even lost three times more sediments (in median, 3,600 g m-2 ). Ground cover and resistance to shear stress seemed to be key factors in the observed/inferred impacts of terracing.