قاسمعلی پاراد

Changes in flooding regime have resulted in widespread declines in ecosystem functioning Flooding affects soils by altering soil structure, depleting O2, accumulating CO2, inducing anaerobic condition in soil, development of root rot, loss of mycorrhizae, and reductions in root metabolism, leads anaerobic decomposition of organic matter, and changing macro and micro elements of soil and leaf. In this experiment, the variations of macro and micro nutrient concentration in soil and leaf of Alnus subcordata (L.) seedlings under soil flooding stress were investigated during a 120-day outdoor experiment. Seedlings were subjected to three fixed treatments: 1) unflooded; 2) flooded to 3 cm depth and 3) flooded to 15 cm depth and their macro and micro nutrient concentration in leaf and soil were measured at the end of the experiment. Results indicated flooding had no effect on the concentration of Mg, Ca, Zn and organic C soil, while the concentration of P, N and K decreased and the concentration of Fe and Mn increased in the soil by flooding, although did not result in toxicity of elements of soil. In leaves of flooded seedlings, the concentrations of N, P, K, Zn, Ca, Mg and organic C decreased, but the concentrations of Mn and Fe increased to a detrimental level. In addition, there was a significant positive correlation between most of elements in soil and leaf. Generally, the results indicated that flooding changed the concentration of much elements in leaf and soil seedlings of A. subcordata that it is a current phenomenon in anaerobic condition of soil caused by flooding.

This study was conducted in greenhouse condition to investigate the growth, morphological and physiological changes and some antioxidant enzyme activities of one-year-old seedlings of Alnus subcordata C. A. Mey. inoculated with Rhizophagus irregularis mycorrhizal fungi under water deficit stress in a period of 70 days. The experiment was carried out at two inoculation levels (control or non-inoculated seedlings and inoculated with R. irregularismycorrhizal fungi) and with two levels of irrigation including irrigation at field capacity (control treatment) and irrigation at 30% of field capacity (water deficit treatment) in a completely randomized design with four treatments and 10 replications. Results revealed that morphological and physiological characteristics of A. subcordata seedlings significantly decreased under water deficit stress at 99% level while all enzymatic activities significantly increased. Although the morphological characteristics such as height and diameter growth, root length, leaf area, and leaf, stem, root, and total biomass significantly increased by 20-30% in R. irregularis mycorrhiza treatment of the irrigation control plants, these features increased by 55, 40, 46, 47, 37, 35, 50 and 37%, respectively when the plants under water deficit treatment were added R. irregularis mycorrhiza compared to non-mycorrhiza water deficit treatment. The meancomparisonresults indicated that the photosynthesis rate, stomatal conductance, transpiration, and leaf water potential reduced by 57, 54, 53, and 65%, respectively under water deficit regime whereas addition of R. irregularis mycorrhizal fungi in soil alleviated the effects of water deficit. Also, under water deficit condition, activities of catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase significantly increased in comparison with field capacity irrigated seedlings while treatment of soil with mycorrhiza mitigated the destructive effects of water deficit. In general, the present study showed that inoculation of R. irregularis mycorrhizal fungi can alleviate physiological indexes and antioxidant enzyme and consequently leading to an increased tolerance of A. subcordata seedlings during the first year.

Zarde-Kija mushroom(Cantharellus alborufescens) is one of the edible mushrooms belong to the Cantharellaceae family. It is widely distributed in the northern forests of Iran and is desirable for local residents in these areas. Despite the economic importance of this genus, litthe is known about their habitat requirements. This study was conducted to identify the environmental factors affecting the distribution of this mushroom in a plain forest of Noor city (Mazandaran province, northern Iran) with 120 ha area. For this purpose, 20 pair plots (20 m × 20 m) with at least 100 m distance were established (20 plots with Cantharellus and 20 non-Cantarellus plots). To analyze the species-environment relationship (soil characteristics), three groups of plant species were identified by the TWINSPAN method. The results showed this mushroom presents in oak-hornbeam stands with following conditions: clay-loam soils, pH value 5.7-7.2, soil C content 2.2-3.7%, total N 0.16-0.27%, C:N ratio 10.8-18.9, water content 29.4-46.2% and litter thickness 4.8-19 mm. In this regard, soil C content, C/N ratio, amount of sand and clay in plots with Cantharellus was 36, 71, 30 and 18 percent greater than those in plots without Cantharellus. Also, Nitrogen concentration (N), ammonium (NH4+), nitrate (NO3–), litter thickness and amount of silt in non-Cantarellus plots were respectively 30, 20, 19, 48 and 28 percent lesser than those in plots containing Cantharellus. Overall, our findings showed that C content, C:N ratio, sand (%) and clay (%) were the most important factors influencing the presence of C. alborufescens.

The aim of this study was determining the physiological and morphological responses of two-year-old common ash (Fraxinus excelsior L.) seedlings to flooding stress. For this purpose¡ seedlings of common ash were examined in a completely randomized design for 102 days under continuous flooding¡ temporary flooding treatment (for 60 and 42 days drainage¡ respectively) and control. Stomatal conductance¡ transpiration¡ and photosynthesis rate were progressively decreased by flooding while all seedlings survived at the end of flooding. Also¡ flooded plants were able to adequately recover their physiological activities. In addition¡ height¡ root length¡ leaf area¡ and biomass accumulation of seedlings decreased under flooding conditions (particularly in continuous flooding). Diameter growth on the other hand¡ increased in seedlings subjected to temporary flooding. Overall¡ the results showed that two-year-old seedlings of F. excelsior had a suitable response to flooding stress until day 60. After 42 days drainage¡ the physiological characteristics of the seedlings were recovered. Generally¡ on the basis of the findings in this research¡ it is expected that F. excelsior can be used for the purpose of restoration of lowlands and wood production in areas subjected to periodic flooding.

Wild plant germplasm possesses useful adaptive strategies. Wild plant species, for example, are resistant to biotic and abiotic stress and can be used for reforestation, agriculture, and horticulture. We surveyed the potential of wild pear to resist flooding. We looked at survival, growth, biomass, and several physiological variables. The rootstocks of wild pear are candidates for planting in orchards that experience periodic flooding. For this purpose, we conducted a completely randomized design with two flooding treatments: 1. 15 days flooding plus 15 days recovery and 2. control, for a 30 day experimental period. The results showed no discernible effects of flooding on survival, height, and diameter. Nevertheless, seven days of flooding had negative and extensive effects on photosynthesis, transpiration, and stomatal conductance. This trend continued until the fifteenth day. Photosynthesis, however, recovered 15 days after the flooding. In addition, plant biomass was negatively affected by flooding. Cessation of photosynthesis after 15 days of flooding proves that the wild pear can be used as rootstock in areas prone to flooding for up to 15 days. If the flooding continues, however, the plant will eventually die.

The aim of this study was to investigate the variation in concentration of macro- and micro- nutrients in soil and shoots of Quercus castaneifolia seedlings growing in flooded and non-flooded conditions. For this purpose، one-year old seedlings of this species were subjected for 120 days to three different conditions: (i) well-drained control (ii) permanent flooding and (iii) periodic flooding in an experiment as a completely randomized design. The results showed that flooding reduced the ratio of Organic carbon، Total Nitrogen and available Potassium in the soil. Potassium concentration in permanent flooding was reduced to 49% in comparison to control treatment. Also، in the permanent flooding، availability of Fe and Mn increased to 42% and 51% with respect to controls، respectively. Under flooding conditions، nutrient accumulation decreased in leaves of stressed seedlings. In addition، the reduction in N، Ca and Mg in permanently flooded seedlings was greater than those in seedlings growing under periodic flooding. The Zn concentration in leaves diminished as a result of the permanent flooding. In both flooding regimes، Mn concentration in leaves with respect to controls increased 2. 5 times، whereas Fe concentration increased 2. 5 and 3. 5 times، respectively. There was found a positive significant correlation between most of nutrient concentrations of soil and leaf. In conclusion، macro-nutrients in soil and shoot of seedlings under flooding stress were reduced whereas micro-nutrients increased. Taking into account that some macro-nutrient concentrations in soil and leaf of seedlings grown in periodic flooding were greater than those in permanent flooding، it is concluded that for growth of Q. castaneifolia seedlings، periodic flooding is more favorable environment than permanent flooding.

In order to examine the growth, morphological and physiological changes of one-year old potted seedlings of Quercus castaneifolia, a research was performed based on completely randomized design with 3 treatments and 4 replicates (with 48 seedlings) in regimes of permanent flooding and periodic flooding (two weeks in between until 120 days) and in the Natural Resources of Tarbiat Modares University of Noor on 120 days. Analysis of LSD’s test showed that the permanent flooding decreased 19% in survival as compared with control seedlings. This is while, that all seedlings in periodic flooding were survived with respect to controls. This reason may be contributed to producing of adventitious and soil drainage that caused increasing gas exchange of rhizosphere. Also flooding decreased growth characteristics, biomass accumulation, and physiological activity such as photosynthetic, stomatal conductance, transpiration and leaf water potential. Of course, except root length and the root/shoot ratio, other parameters in permanent flooding were smaller than those of in periodic flooding. In contrast, diameter growth response in periodic flooding was higher than that in permanent flooding and it was a little greater than that in control. The reason of this phenomenon may be attributed to the development of woody xylem cells. Generally, on the base of findings in this research, it can be stated that Q. castaneifolia seedling is relatively tolerant to flooding (particularly to periodic flooding). It is suggested that for restoration of degraded forests exposed on flooding stresses and or where the natural regeneration of this species is being restricted by flooding, such a research with further seedlings, in different growth phases and during longer periods can be used with this species and also other species with similar ecological nature.

The aim of this study is investigation of survival، vegetative characteristics and biomass allocation in seedlings of common ash (Fraxinus excelsior L.) grown in different water regimes. For this purpose، seedlings of ash were examined in a completely randomized design for 120 days in an open area of bottomland forest at two levels of soil moisture regimes (permanent flooding، periodic flooding with a rotation period of 15 days) and control level. At the end of the experiment، flooding decreased survival، vegetative characteristics، biomass allocation and vitality of ash seedlings. This reduction in permanent flooding was more than at the periodic flooding. In contrast، diameter growth response in periodic flooding was greater than permanent flooding and control level. The reason of this phenomenon can be attributed to the development of woody xylem cells. In periodic flooding، compared to permanent flooding، because of greater production of adventitious root and soil drainage، access of oxygen required for metabolism was easier and Photosynthetic organs of the plant (leaf area) and leaf biomass prominently increased. Overall، the results showed that F. excelsior was tolerant to flooding and can be used for restoration of bottomland forest، riparian area، lagoons and plains exposure to periodic flooding.