Some criteria of regeneration density in young beech populations

Some criteria of density in beech saplings were studied in various forest associations (mainly Galio odoratiFagetum typicum) growing in the submontane region near Zurich (Swiss Central Plateau). The sample plots were established in regeneration gaps resulting from Swiss irregular shelter wood system (Femelschlag). Five sample plots, each 2x2m in 3 transects (a total of 15 plots in each gap, x 10 gaps), were laid out from the center to the edge of the gap and under the old growth stand in the upper, middle and lower parts of the gap. Three collective criteria (i) number of saplings (Nm-2), (ii) mean distance of saplings and (iii) crown competition factor and one individual criterion (growth space) were investigated within the sample plots. Results showed that the density of beech saplings was not homogenous. The number of saplings (Nm-2) had wide amplitude, which varied between 2.5 and 54.8 and the mean distance of saplings varied between 14.5 and 68.0 cm. The crown competition factor varied between 1 (100%) and 5 (500%) indicating five times of overlapping in crown space of saplings, while the growth space of the studied beech saplings varied between 1.2 and 12.0

Canopy gaps characteristics and structural dynamics in a natural unmanaged oriental beech (Fagus orientalis Lipsky) stand in the north of Iran

Canopy gaps are one of the most important structural features of forest ecosystems, and studying them can have useful results and implications for forest management. The aim of this study was to investigate the characteristics and regeneration within canopy gaps in an intact beech stand in Shastkalateh experimental forest of Hyrcanian region, north of Iran. All canopy gaps and related forest parameters were measured within a permanent plot of 16 ha. Then, for each canopy gap, two parameters were measured—the length (L) as the longest distance within the gap, and the width (W) as the largest distance perpendicular to the length. Considering the composition of the forest, the dominant tree species was oriental beech with 36.3% of the stem number and 56.6% of the stand volume. Totally, 54 canopy gaps were identified which covered about 5% of the forest area. An average of 4.32 gaps.ha-1 existed in the permanent plot and gap sizes varied from 48.3 to 622.7 m^2. Over three-quarters (77.7%) of canopy gaps were smaller than ≤200 m^2 and also over half of the gaps (53%) were formed by a single tree-fall event. The beech made up 52% of gap makers and 23.4% of gap fillers and also had the second largest proportion on standing deadwood of gap maker in the study area, while velvet maple was the most frequent gap filler in approximately 30% of the gaps. Despite the high frequency of small gaps 100 m^2, their proportion of the overall gap area reached only 25%, suggesting the important role of intermediate and large gaps in the gap dynamics. Considering the recent occurring disturbances in the Hyrcanian forests, the study analyzed the main characteristics of disturbance regime with the emphasis on the role of wind and longevity of trees. In general, findings of this study showed that creating small and average gaps in intact beech forests could be based on natural disturbance regimes, and suitable conditions provides for successful regeneration of beech forests in close to nature silviculture

Influence of gap size and development stages on the silvicultural characteristics of oriental beech (Fagus orientalis Lipsky) regeneration

We studied 11 gaps covered with beech saplings (< 1.30 m tall) in a reserve compartment (compartment 139, district one, Langa forest, watershed 36: Kazemrood) of the Caspian beech forest in N Iran. Two transects, each 2 m wide, were laid along the longest (N-S) and shortest (E-W) axis of each gap. Five micro sample plots, each 4 m2, were established: one at the center, and one at each corner. Qualitative and quantitative characteristics of saplings with a diameter at breast height less than 7.5 cm were examined in the micro sample plots. Analysis of variance (ANOVA) and Kruskal-Wallis test were performed using SPSS software for quantitative characteristics, and chi-square test for qualitative characteristics. Results indicated that medium-sized (200-500 m2) gaps promote the growth of oriental beech saplings of desirable silvicultural forms during decay and initial stages

Cellular energy allocation of Glyphodes pyloalis (Lep.: Pyralidae): changes related to exposure to TiO2 nanoparticles

In order to study the pollution potential of TiO2 nanoparticles (TiO2-NPs) on ecological health, this research was carried out on the cellular energy allocation (CEA) of Glyphodes pyloalis Walker exposed to TiO2-NPs. The newly ecdysed fifth instar larvae of G. pyloalis were treated with LC10, LC20, LC30, LC40 and LC50 concentrations of TiO2-NPs and the amount of energy available (Ea), energy consumption (Ec) and cellular energy allocation were compared. The resulting calculated energy reserves (lipid, carbohydrate, glycogen and protein) showed that increasing the time of exposure, the total lipid and carbohydrate amounts significantly decreased, when the LC30, LC40 and LC50 concentrations were applied. The amounts of glycogen in the larvae treated with LC10, LC20 and LC30 concentrations of TiO2-NPs were increased, whereas the LC40 and LC50 concentrations led to decrease in the amount of glycogen. The significant reduction in the amount of total protein compared to the control and over all three days of treatment was observed for LC50 concentration of TiO2-NPs; however, the LC10 concentration lead to a significant increase of the total protein after three days. Ea decreased in a dose-response related manner and over all time points, but it significantly increased in treated larvae by LC10 and LC20 concentrations after two days. Ec increased as concentrations grew to LC30 and then started to decrease. The results showed that CEA was not affected by LC10 concentration, but significantly decreased when the concentration increased and at all time points probably as a cost to deal with TiO2-NPs detoxification. Therefore, it will be possible to use the CEA as an appropriate early biomarker for the impacts of TiO2-NPs

Effects of imidacloprid, dichlorvos, pymetrozine and abamectin, on life table parameters of the predatory bug, Orius albidipennis (Hemiptera: Anthocoridae)

Effects of four pesticides (imidacloprid, dichlorvos, pymetrozine and abamectin) were evaluated on life table parameters of Orius albidipennis (Reuter). Pesticides were used at the concentrations recommended by the manufacturers. The bioassays were carried out using drum-cell method, in a growth chamber at 27 ± 1ºC, R.H. of 65 ± 5% and 16 h photo phase. The net reproductive rate (R0) value for the populations treated with imidacloprid, dichlorvos, pymetrozine, abamectin and tap water as control was, 2.91 ± 0.48, 18.85 ± 2.55, 10.16 ± 1.21, 8.00 ± 1.05, 43.40 ± 7.64; the intrinsic rate of natural increase (rm) was 0.040 ± 0.005, 0.097 ± 0.018, 0.086 ± 0.012, 0.078 ± 0.010, 0.148 ± 0.006: the mean generation time (T) was 25.60 ± 1.12, 25.94 ± 1.85, 26.37 ± 0.25, 25.61 ± 0.21, 25.20 ± 1.16; the doubling time (DT) was 18.04 ± 2.76, 7.72 ± 1.60, 8.23 ± 1.11, 9.24 ± 1.37, 4.68 ± 0.18, and the finite rate of increase (λ) was 1.041 ± 0.006, 1.102 ± 0.019, 1.090 ± 0.013, 1.081 ± 0.011, 1.160 ± 0.007, respectively. Imidacloprid and dichlorvos, which revealed the most and the least effects on the life table parameters, were the most and the least harmful among the chemicals tested

Effects of phosalone residues on alfalfa weevil larval parasitoid, Bathyplectes curculionis (Hym.: Ichneumonidae)

A study was carried out to determine the suitable spraying time for phosalone against alfalfa weevil, Hypera postica (Gyllenhal) (Col.: Curculionidae), with the least adverse effects on its major parasitoid, Bathyplectes curculionis (Thomson) (Hym.: Ichneumonidae). Plots of 10 m2 were sprayed with phosalone (35%) at 3.0 kg/ha, using a knapsack sprayer. The residues of phosalone in parasitoid cocoon and alfalfa foliage were measured at different time intervals after treatment using high performance liquid chromatography. Residues of phosalone on B. curculionis cocoons treated by dipping method were 0.751, 0.466, 0.245, 0.115, 0.075, 0.044 and 0.019 µg/cocoon in 2 hours, 1, 3, 7, 14, 22 and 30 days after treatment, respectively. Results of this experiment revealed that there was no penetration of the insecticide into the cocoon. In fresh foliage, the residues of phosalone were 74.066 ï± 6.9, 47.319 ï± 2.1, 16.345 ï± 1.99 and 3.743 ï± 0.33 mg/kg at 2, 4, 7 and 14 days after spraying, respectively. The residue level on foliage at day 7 is critical and this must be considered as the least interval time between the application of the phosalone and the peak of parasitoid population

The Ser431Phe substitution in acetylcholinesterase associated with pirimicarb and organophosphorous insecticide resistance in the peach-potato aphid, Myzus persicae (Hem.: Aphididae)

The peach-potato aphid, Myzus pesicae Sulzer, is a globally distributed, economically important pest of a wide range of field crops and ornamentals. Due to extensive and repeated use of insecticide, this species has developed many different resistance mechanisms to insecticides. The enzyme acetylcholinesterase (EC 3.1.1.7) (AChE) occurs widely in both vertebrate and invertebrate nervous systems and is the target of organophosphate (OP) and carbamate insecticides. One of resistance mechanisms to OP and carbamate insecticides is the insensitivity of AChE to these insecticides. In this study the possibility of mutation in insensitive AChE was surveyed. The complete coding sequences of acetylcholinesterases (MpAChE2) from susceptible and resistant populations were identified and sequences from resistant and two susceptible populations were compared. Consequently, one amino acid substitution (Ser431Phe) was detected within the resistant population at MpAChE2 gene. The Ser431Phe substitution is located in acyl pocket of acetylcholinesterase. Therefore, it seems that MpAChE2 is important as a target of pirimicarb. This substitution makes the acyl pocket narrower and pirimicarb can not have any access to this site. cDNA was obtained from individual aphids randomly and sequence of MpAChE2 indicated that MpAChE2 of the resistant population was heterozygous