Search

Tree mixture may increase stand productivity while forest tree density mostly negatively influence the tree growth. However, several research have indicated that the knowledge on the corelation between tree mixture and stand productivity is still limited. In this study, the relationships among tree mixture, stand type (i.e., even-aged versus uneven-aged), density and diameter increment of Kazdağı fir (Abies nordmanniana subsp. equi-trojani [Asch. & Sint. ex Boiss] Coode & Cullen) were examined. The research was conducted within the Ayancık Forest Management Directorate, Sinop Regional Directorate of Forestry. Four different stands were selected; a) uneven-aged fir stand, b) even-aged fir stand, c) unevenaged mixed fir-beech stand, and d) even-aged mixed fir-beech stand. Five-year diameter increment in these four different stand types was determined and compared. Random effects regression analysis was utilized to examine the influence of the mixture and tree density on the diameter increment. Statistical relationships were found among tree mixture, stand density and the diameter increment (p<0.05). Moreover, diameter increment varied among the stand types. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) is the third most important cereal crop after rice and wheat which is considered a soil-exhaustive crop. The combination of soil exhaustive and replenishing crops in a cropping system is a beneficial approach where legumes can play a vital role in agricultural sustainability. As maize is a widely spaced crop, intercropping legumes can easily be adopted. Based on these facts, an experiment was conducted at P. G. Research Farm of Centurion University of Technology and Management, Odisha during two consecutive Rabi seasons of 2021-22 and 2022-23 where chickpea (Cicer arietinum L.) and field pea (Pisum sativum L.) were intercropped with hybrid maize by adopting different planting geometry. The mean data of two years revealed that sole maize uniform row (UR) being statistically at par with sole maize paired row recorded the higher plant height and dry matter accumulation of maize than intercropped maize. Sole maize also recorded higher values of yield attributes of maize, namely, number of cobs/plants, number of grains/row and number of rows/cobs which was reflected in the grain yield of maize. Due to inter-species competition, grain yield of maize was reduced in the mixed stand where uniform row sole maize registered the highest grain yield (5857 and 6101 kg/ha, respectively during both years) and it was closely followed by paired row sole maize (5789 and 6005 kg/ha, respectively). Grain and stover yields of legumes, such as chickpea and field pea were higher in pure stand because of its optimum plant stand and devoid of inter-species competition. Moreover, the benefits of the intercropping systems were pronounced in all the intercropping systems laid out in an additive series in terms of land equivalent ratio, relative crowding coefficient, area time equivalent ratio, competitive ratio, maize equivalent yield and monetary advantage. The study revealed that intercropping maize UR + chickpea (1:2) resulted in the highest values of net return and benefit-cost ratio which can be recommended for South Odisha conditions. [ABSTRACT FROM AUTHOR]

An analysis of the creation and operation of protective forest plantations at agricultural enterprises of the Central Chernozem Region allows us to assert that positive ameliorative functions are performed by those forest plantations that have good growth, high stability and longevity. Russian forestry scientists have recognized that the main species in the steppe conditions for all types of protective forest plantations is the English oak. The aim of the research has been to assess the current state of the stands in forest shelterbelts planted via different methods with the English oak as the main species. Taxation works and forest pathology research were carried out in 1997–2021 in the forest shelterbelt no. 9, established in the spring of 1989 by 2-year-old seedlings in the land-use territory of the Federal State Unitary Enterprise Experimental Production Farm “Znamya Oktyabrya” of the Talovskiy District of the Voronezh Region. It has been established that the influence of combinations of tree species in forest belts on the growth of the English oak at the age of 32 years is quite significant. As a result of competitive relations for environmental resources by fast-growing and associate species, the number of live oak trees in a continuous row planting option is 35.6...52.1 % less than in intermittent forest belt options, of their number during planting. The remaining sharply oppressed oak trees in the plantation sown in the continuous row planting way are far behind in height and stem diameter (by 0.8...7.6 m and 4.1...12.7 cm, respectively) compared to the oaks growing in the intermittent forest belts sown in a block planting way. The absence of improvement felling in the experimental plantations during their growth and formation has led to a significant number of dead oak wood and non-viable trees of this species. Moreover, the proportion of dead oak wood and non-viable trees in the forest belt sown via continuous row planting exceeds the indicator in the intermittent forest belts by 36.6...40.6 %. The number of viable oak trees in the intermittent belt options is 17.7...27.3 % higher than in the continuous row planting option, and the number of limitedly viable trees is 11.5...18.9 % higher.

Gmelina arborea is a species that holds economic value in forest markets, primarily due to the versatility of its biomass, rapid growth, and timber quality. The main objective of this research was to evaluate the dendrometry, biomass, soil, and the physical and mechanical properties of the wood in two 18-year-old stands. In rectangular plots of 1000 m², dasometric information from 20 trees was collected, in addition to wood fractions for physical-mechanical tests in the laboratory. Statistically, mixedstand G. arborea exhibited a larger diameter (7.3%) and stem biomass (5.1%), as well as an impact on mechanical properties (8.1%) and hardness on its various axes (long. 6.2%, rad. 1.5%, and tang. 6.3%). It is inferred that mixed stands contribute to greater biomass and better resistance and quality of wood in G. arborea. [ABSTRACT FROM AUTHOR]

Changing environmental conditions, disturbances, and escalating demands for forest ecosystem services require foresters to restore present forestlands with new forest generations that will exhibit ecological integrity, diversity, high adaptive capacity, and the ability to provide essential ecosystem services. Establishing such forests requires careful consideration of the forest landscape and site dynamics. In pursuit of these requirements, we developed a novel framework that enables the restoration of forest sites and promotes the desired features of the forest complex at the same time. This framework was designed with the methods of system engineering and was organized in the same way as the forest planning process. It was tested in the habitat type of Illyrian Fagus sylvatica forests belonging to the Natura 2000 network. The environmental, vegetation, and site conditions were investigated via field inspections, available forest management plans, and simple GIS analyses. Additionally, we established a seminatural stand composed of European beech, sessile oak, sycamore maple, silver fir, and some wild fruit tree species. The survival of planted species was assessed using census and simple random sampling, the performance of provenances by Student's test, while microhabitat factors were explored by a one-way ANOVA. The survival rate of key species was estimated to be 55.6%, while that of fruit species was estimated to be 94.5%. Our framework demonstrated satisfactory performance and contained sufficient benchmarks to facilitate consistent decision-making. In the discussion, we elucidate the framework's primary features and attributes of the mixed stand, where we also expose some open issues to be addressed in the future. [ABSTRACT FROM AUTHOR]

Birch, being one of the main forest-forming tree species, has valuable and soughtafter timber. In production forest conditions, natural regeneration and crops of this species experience strong competition from both grass cover and undesirable hardwoods (aspen, gray alder and willow). Without carrying out high-quality maintenance (agrotechnical care, clearing), the formation of economically valuable birch forests is impossible. The most effective and economical is the chemical care method, which involves the use of modern environmentally friendly herbicides. However, if technological regulations and practical recommendations for the use of herbicides have already been developed for the care of coniferous species (pine, spruce and others), then there are currently no such recommendations for birch. The aim of the research is to develop a scientifically based method of caring for natural young birch stands (clearing, agrotechnical care) using selective herbicides on forest fund lands. The objects of research are seed and vegetative regeneration of birch in young stands formed in clear-cut areas, as well as undesirable herbaceous and tree-shrub vegetation. When laying the experiments and evaluating their results, we were guided by the generally accepted methodology for testing herbicides in agriculture. In field production and small-scale experiments with herbicides magnum, magnum super, mortira and anchor-85 in young stands with birch trees, the biological effectiveness of the action of the preparations on a wide range of undesirable vegetation was determined, as well as their selectivity with respect to birch. High efficiency of herbicides magnum (100–300 g/ha) and magnum super (100–200 g/ha) on dicotyledonous species of herbaceous vegetation and deciduous species – willow, aspen, gray alder and mountain-ash, as well as high resistance of birch to them at continuous spraying during the growing season was established. Herbicides mortira (100–200 g/ha) and anchor-85 (100 g/ha) were recognized as unsuitable for birch care. It was found that after a single application of herbicide magnum at rates of 100 and 200 g/ha in mixed young stands dominated by aspen, willow and gray alder and with participation of birch 1–2 composition units, stands dominated by the latter are formed. Acknowledgements: The study was financially supported by the Federal Agency of Forestry within the state assignment of the Saint Petersburg Forestry Research Institute approved by Order No. 1061 of 25.12.2018. For citation: Egorov A.B., Postnikov A.M., Bubnov A.A., Pavluchenkova L.N., Partolina A.N. Growing Birch in Clear-cut Areas with Herbicide Application. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 58–74. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-58-74

The predominance of mixed forest stands in a productive forest fund, which is located in the middle taiga subzone of Northwest Russia, determines the relevance of an investigation of the growth and development characteristics of the trees. In secondary stands, created by an extensive human consumption of primary spruce stands, spruce trees are generally presented in a minor quantity. The recovery of their dominance is an urgent economic and ecological issue. Despite the unity of approaches concerning the maintenance of deciduous-spruce forests, the research characteristics on the structure of the root systems differ considerably along with age and geographical position. This article investigates a root system competition between spruce and deciduous species in a 70-year-old blueberry-type forest that was 100 thinning by a reconstructive cutting 35 years ago. The mass of fine roots and their distribution in the upper solid layers were examined by the method of soil monoliths in the mixed stands with different proportions of spruce. The numerical characteristics of the stands were determined by the results of a regular complete enumeration on the trail plots. Besides, the tree diameters were measured around the circular plots, which were made for the collection of the monoliths. The records were made on the dynamics of changes in forest floor thickness and vegetation. The relationship between the underground and elevated parts of the stands was explored. It was shown that the roots of spruce can occupy the same ecological niche as the roots of deciduous species. A correlation analysis revealed a statistically significant relationship between the mass of fine spruce roots and the competitive influence of deciduous species, the proportion of spruce in the stand, and its current volume increment. There was a significant difference in spruce root mass under joint growth with birch and aspen. Therefore, it was concluded that this phenomenon has a complex nature. Namely, the mass of the spruce roots has a direct dependency on their closeness to the maternal trees in combination with the spatial heterogeneity of the organic soil layers. The gained findings are important for the regulation of the composition and structure of the mixed deciduous-spruce stands for growing sustainable stands with a high economic value. For citation: Karpechko A.Yu., Sinkevich S.M. Influence of Reconstructive Cutting in Deciduous-Spruce Stands on Root Competition of Species. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 99–112. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-99-112

Many trees of high timber value require canopy cover to become established, and at present, they are only harvested from native rainforests. Other species require high radiation to establish and can be planted in monospecific stands. The main question was whether the canopy generated by a light-demanding rainforest species could protect mid-successional timber species from high radiation and extreme temperatures. We evaluated the establishment of Cabralea canjerana under the canopy of Araucaria angustifolia stands. We related growth to the number of neighbors to determine the best positions to plant C. canjerana. In one stand, we measured environmental and physiological traits, and we determined that the seedling did not suffer light or water stress. Cabralea canjerana plant establishment was successful in stands of different basal areas, and trees reached the highest growth with up to two A. angustifolia neighbors within a 5 m radius. Therefore, the number of neighbors is a tool to choose the planting location to convert even-aged to uneven-aged mixed stands. In this way, valuable native timber species that require canopy protection during the first few years can be planted outside the rainforest. This is the first report of an uneven-aged mixed plantation of two Atlantic forest timber species. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Winter cover crops (WCCs) are fast-growing and high biomass producing crops that are included in the of crop rotation between two main cash crops. WCCs are used for greening the soil and can increase the yield of the main crop by increasing soil organic matter (SOM), soil water infiltrability and reducing water runoff and erosion, decreasing the weeds population and other soil-borne harmful biotic agents, improving soil microbial community, and enhancing agroecosystem services; however, yield can be adversely affected if they fix excessive nitrogen and do not release it in a timely manner. The carbon/nitrogen (C/N) ratio achieved in soil greening is a major factor in the availability of soil nitrogen, regardless of the location of soil residues; therefore, one option is to increase the nitrogen content of WCCs by sowing a mixture of legume and non-legume crops, since non-legumes such as grasses typically have a low nitrogen content and little to no positive effect on soil nitrogen availability on subsequent crops. The combination of legumes and non-legumes as WCCs exhibit multifaceted benefits such as quality biomass production, crop diversification, efficient plant protection, enrichment of soil microbes, biological nitrogen fixation, and so on. The integration of WCCs grasses and legumes into the crop rotation increases rational nitrogen management and can also increase SOM content and, consequently, soil fertility. The effective release of mineral nitrogen into the soil along the time should be taken into account in order to minimize leaching and optimize the symbiotic N fixed for the subsequent cash crop. Finally, with WCCs, it is possible to produce high-quality animal feed in pure stands and in mixtures in order to obtain on sustainable farm forage resources. [ABSTRACT FROM AUTHOR]

Research Highlights: In mixed stands, competitive and supportive relationships occur between trees, illustrated by their dendrometric characteristics. Background and Objectives: We investigated the effect of species composition on growth and yield in mixed beech–coniferous stands in the Romanian Carpathians. Materials and Methods: We selected sites with similar trophicity levels, as determined by the site mapping method. Under the same site conditions, we generated models to determine, for each species (spruce, fir, and beech), the main parameters of the site index, including mean height, dominant height, standing volume yield, and mean annual volume increment for different compositional species proportions (psp) and categories of proportions (i.e., low psp, between 10 and 50%, and high psp, ranging between 60 and 90%). Results: Overall, up to the age of 100 years, mixed stands with low psp had enhanced tree height growth, characterized by mean values 2.2% higher for spruce and 4.8% higher for fir and beech. Dominant height showed similar values, regardless of psp. Mixed stands in which the psp increased (i.e., psp > 50) were more productive, with the mean yield differences at the age of 100 years ranging from +1.7% (for fir) to +3.8% (for spruce and beech), increasing to +6% at 140 years. Conclusions: When setting management targets, the management of mixed forests should be based on an understanding of the relationship between the site, species ecological requirements, and their yield potential. Mixed stands can influence individual tree growth and stand yield through psp. [ABSTRACT FROM AUTHOR]

Aims: Black pine coastal forests play an important role as windbreak and as a natural barrier to sand and salt spray inland in Japan. The recent invasion of N2-fixing black locust (Robinia pseudoacacia) trees in these forests is expected to have a nutritional contribution on black pine trees growth. Thus, the effect of this new source of N on black pine trees N assimilation needs to be assessed. Methods: In order to evaluate this contribution, tree-ring isotopic composition (δ15N) and nitrogen content (%N) of black pine (Pinus thunbergii) trees in a pure stand (BPP) and a mixed stand (BPM) with black locust (BL) trees were measured for the period 2000–2019 for BPP and BL and 1990–2019 for BPM. The same measurements were conducted in plant tissues and in soil samples. Results: The tree ring δ15N values showed that for the last 30 years, BPM trees gradually switched from BPP to BL-derived soil N starting in the 1990s, becoming the dominant N source from 2000 as no significant difference was found between BPM and BL tree ring δ15N values from 2000 to 2019. No difference in root and sapwood BPM and BL δ15N values were found, but BPM foliage (−2.1‰) was different to BPP (−4.4‰) and BL (−0.3‰), which is related to the different N assimilation pathways between BP and BL. Conclusions: Based on the results of this study, the assimilation of BL-derived N inferred from the BPM tissues δ15N values is the result of an increase in soil bioavailable N with a higher δ15N value. [ABSTRACT FROM AUTHOR]

The study was conducted to examine the characteristics of natural regeneration and the spatial relation of seedlings and saplings in the mixed stand of Picea spp. + Larix principis-rupprechtii in Guandi Mountain. The spatial distribution pattern and heterogeneity of naturally occurring seedlings and saplings were studied using the method of adjacent lattice combined with the semivariance function. The results showed that the regeneration density of the understory community was 450-1 350 trees • hm-2, which was dominated by Picea spp., accounting for 81.74% of the community. The regeneration density of Picea spp. was 688 trees • hm-2, and that of L. prirzcipis-rupprechtii was 167 trees•hm-2, the latter demonstrating poor regeneration. A majority of the seedlings and saplings were clustered, and the clustering intensity gradually decreasing with increasing scale. A strong spatial autocorrelation was observed between the seedlings and saplings. Structural and random factors were responsible for 79.6% and 20.4% of variations in the distribution pattern, respectively. The spatial distribution of seedlings and saplings demonstrated anisotropy, with a dominant northeast to southwest pattern and subdominant northwest to southeast pattern. The spatial autocorrelation range of the ground diameter and tree height of seedlings and saplings were 11.25 and 13.85 m, respectively. Structural factors had a greater influence on the spatial heterogeneity, which was stronger in the horizontal direction. [ABSTRACT FROM AUTHOR]

Competition between trees has an impact on their structural features and it is very important to measure the competition index and determine the correlation with some of the characteristics of the trees. To conduct the research, circular sample plots (n = 24) with an area of ​​400 m 2 were established in a 150 × 100 m grid in the forest, Savadkoh-Mazandaran. Within each sample plot, frequency, height, crown diameter and diameter at breast height (dbh) for each tree were measured in the overstorey. The richness and diversity index of trees and competition index for each plot were calculated. The results showed that there was a significant difference between the values ​​of competition index for the three tree species. Competition index with height, dbh and crown diameter had significant positive correlation for all tree species, but negative significant correlation with height and H/D for beech and alder and also positive correlation for hornbeam. There was a negative significant correlation between beech competition index and tree richness index and a positive correlation between alder competition index and tree diversity index. With increasing altitude, competition index values ​​decreased only for hornbeam species. Significant differences were observed among the three tree species in terms of crown diameter, dbh, height and H/D ratio in stand. In general, regarding the relationship between some tree variables and the index of competition in the stand, this information can be used in the selection and application of silvicultural operations such as thinning and remarking in temperate Hyrcanian broadleaf forest.

Taradeh, Kerman province, has valuable forest stands that are under pressure from local communities. In this study, after making forest survey, plot area was selected as ​​1500 m2 and 50 samples were collected systematically with in a grid of 100 m×100 m. In each plot, the plant species were recorded along with diameter at breast height, tree height, crown diameter, number of trees per hectare, large and small crown diameters, regeneration count, the distance between plot center and the nearest tree, and distance to neighboring trees. Results showed that the forests under study are mixed and include Prosopis cineraria, Prosopis farcta, Tamarix stricta, Lysium shawii, and Calligonum comosum as the main species. The mean density of Prosopis cineraria and other species were 10.6 and 37.2 tree.ha-1 and canopy cover were 308 and 1088.3 m2.ha-1, respectively. The height and diameter of P. cineraria trees were in the range of 5.5-14.3 m and 16-100 cm respectively, and its regeneration density was 1.26 tree.ha-1. The structure of the forest was uneven-aged and two-layered which in overstory was occupied by P. cineraria trees. The distribution pattern of P. cineraria trees was clumped which may be influenced by type and size of the seeds, dispersion method, human interference, habitat constraints, and livestock grazing. Due to the lack of trees in low diameter classes and lack of regeneration, tree planting and preservation is recommended, especially in occupied lands.

• Key message: This document provides valuable environmental information about a triplets' essay of Scots pine and Maritime pine in Spain. The dataset characterizes the soil profile (physicochemical parameters of organic and mineral horizons), climate, physiography, understory and overstory. Dataset access is athttps://doi.org/10.5281/zenodo.4384530and associated metadata is available athttps://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/21cca830-daf9-4913-9b5b-a185d77943d5 [ABSTRACT FROM AUTHOR]

Accounting of forest fund on forest reserve lands is a primary stage of scientific studies investigations, which are focused on concerning of their resource potential and others qualities. The study object of investigation is forest stands of reserve zone of the National Nature Park «Skolivski Beskydy». The aim of research is selection of model forest stands. The model forest stands is forest stand with maximum of biodiversity and productivity with most compound vertical structure. Point cruising inventory is most adequate method for receiving primary data about object of research. The distinctive feature of this method is providing supplement of silviculturale and inventory indexes of investigated object through by analysis of spatial structure of forest stands, indexes of horizontal tree placement and biodiversity. The model forest stands in the condition of Majdan forest district were distinguished as a result of point cruising inventory and analyzing of primary data. There were distinguished six model forest stands were distinguished with age range from 55 to 136 years. These models stands were selecting from great number of primary data set. For the objective data selection additionally were developing two patterns were developed. First pattern is in describing dependence between average stand increasing and age. Second pattern is in showing the theoretical dependence of stem volume and average diameter of first stage of stand. The primary data were divided for two groups according to the value (increasing, stem volume). The first group is presented by model forest stands. These objects are laying on the top part of confidence part of model with one-two standard deviation limits. The analysis is shows complex vertical structure of model stands. The trees of models are distributed between three stand stages in different proportions. The share portions of first stage are varying between 43-63%, second stage – 4-32% and third – 24-31%. The analysis of volume distribution are showing the largest concentration on first stage (76-97%). The maximum part of stand volume on the second stage is made 21% and on third stage – 3%. The stages of model stand are formed from beech, fir and spruce. Only one stand from model stands is characterized by the larch, sycamore, spruce and fir in tree composition. The high productivity and structural compound model stands are typical nature formations and forest management activity must be oriented at for these stands.

Birch, as one of the pioneer species, is a part of the preparatory forest, especially aft er extensive calamities. In the 1970s and 1980s, it most oft en served as a substitute stand in connection with the widespread dieback of forests as a result of the effects of air pollution. In recent years, it has become increasingly important in relation to the impacts of climate change. Th is paper deals with the comparison of selected quantitative and qualitative characteristics of two mixed birch stands at the age of 59 years, having the production and spa-therapeutic function, over a 30-year period. Th e results showed higher values of quantitative parameters (a number of trees, basal area, and merchantable volume) in the plot with the spa-therapeutic function. Qualitative production was slightly worse in the plot with production function. [ABSTRACT FROM AUTHOR]

Modification of stands’ structure and managing them using silvicultural methods close to nature and single selection system require information on status of structure, determining the target diameter, basal area and suitable volume to result in long-term equilibrium and sustainability. So, this study was conducted using the selection sample statistical method by selecting five 1-ha sample plots in mixed oriental beech Fagus orientais Lipsky forests of Asalem watershed, located in the west of Guilan Province, Northern Iran. Quantitative and qualitative features of the studied stand were recorded in relation to each sample plot. The results from analysis of the curves related to diameter classes, volume and basal area of the stands with their annual growth showed that 26 to 28 m2.ha^-1 and a volume of 300 to 350 m3.ha-1 with a target diameter of 75-80 cm was suggested for the purposeful removal and avoiding taste markings in order to modify and guide the structures of Northern Iran’s oriental beech stands.

By comparing the pattern of rings among the trees in each region, it is possible to determine the exact year of ring formation. In this study, the data were collected from two different sites, Basht and Dehdez. In each site, 18 Quercus brantii individuals from two growth forms were selected and cut within each plot and the felled trees were then partitioned and the fresh weight was measured in the field. Also, a complete cross-sectional disk was sampled from each sampled tree at stump height (0.3 m aboveground). Moisture and carbon content of samples were measured in the laboratory and dry weights and carbon stock were also calculated. The proportion of annual diameter and average annual biomass quantity in the scale of individual tree and the growing forms including coppice and high-forest were studied in the current research. Average annual radial increment for Quercus brantii from two plantations, high forest, and coppice, were 1.73 and 1.95 in central Zagros forest and 2.04 and 1.98 (mm/year-1) in south Zagros forest, respectively. Also, average annual biomass increment for high forest and coppice were 6.34 and 6.52 in central Zagros forest and 7.20 and 6.84 (kg/year-1) in south Zagros forest, respectively. The carbon allocation was 48% of the biomass production. The results showed that there are no statistically significant differences between annual diameter increment and average annual biomass amounts in two different sites (p

The present study has been done to evaluate the impact of pure ash stand and mixed stand with beech on the herb layer biodiversity and soil properties in the forests of Noor city. There is a unique stand of ash in the forests of Noor city and at 1,900-2,100 m a.s.l., which is rarely seen like that in the northern forests of Iran. Shannon-Wiener diversity indices (H'), Simpson index of dominance (D), Margalef richness (R1) and Pielou's evenness were used to analyse biodiversity. Sampling was also conducted to investigate physical and chemical properties of soil (bulk density, acidity, electrical conductivity, soil moisture, soil lime, nitrogen and organic carbon) in each sample plot and at two depths (10 and 20 cm). The total number of 26 soil samples (13 soil samples at either depth) in pure ash stand and 24 soil samples (12 soil samples at either depth) from this type of stand mixed with beech were taken. The results of plant species biodiversity showed that between the pure ash stand and the stand mixed with beech there is a significant difference at the 99% probability level in Shannon-Wiener diversity, Margalef richness, and Simpson dominance. There is also a significant difference at the 95% probability level between the two stands under study in Pielou's evenness index. The results of soil factors also showed that at the depth of 10-20 cm acidity factor showed a significant difference from its adjacent stand at the 99% probability level. There is also a significant difference at the 99% probability level in acidity (0-10 cm) and soil moisture at the depth of 10-20 cm between the two areas, but there is not any significant difference between the areas under study in electrical conductivity and lime factors at the two depths and also in moisture content at the depth of 0-10 cm. It should be noted that between the stand and soil nitrogen, organic carbon and bulk density parameters at both depths (0-10 and 10-20 cm) a significant difference at the 95% confidence level is shown.

The experiment was conducted during winter seasons: 2016-2017 and 2017-2018 in the field of agriculture college - Al-Qasim Green University - Babylon -Iraq to study effect of sowing dates and seeding rate in the nutritional value of the mixture fodder. The randomized complete block design was used under split-plots arrangement in three replications, the main plots were included three sowing dates (D1: 1 Sep., D2: 15 Sep. and D3: 1 Oct.), while the sub-plots were included seven of the seed rates: (Q1: 150 kg.ha-1 barley, Q2: 130 kg.ha-1 barley, Q3: 110 kg.ha-1 barley + 27 kg.ha -1 clover, Q4: 90 kg.ha-1 barley + 23 kg. ha- 1 clover, Q5: 27 kg.ha-1 clover, Q6: 100 kg.ha-1 barley + 27 kg.ha-1 clover, Q7: clover 35 kg.ha-1. The results showed: D3 treatment was superior in percentage of crude protein and crude protein yield in all seasons respectively, while the D1 treatment was superior in the percentage of crude fiber (24.40 and 23. 87%) in all seasons respectively, Q7 treatment was given higher percentage of crude protein and total yield of crude protein, Q2 treatment was superior in the percentage of crude fibers, Q6 treatment was given the higher yield of crude fibers in the both seasons. [ABSTRACT FROM AUTHOR]

Numerous approaches have been developed to quantify forest structure modules. A variety has measured each as part of stand attributes. This study was carried out in managed mixed stands in northern Iran. The objective was to quantify stand structure and its variation before and after tree marking through the Gini index and structural triangle method. A full sampling inventory was taken in 2004 and 2014 at the beginning and end of a period, before and after tree marking operations in five stands. The results indicate that the Gini index was 39.5, 62.2, 43.0, 82.0 and 74.0% for I, II, III, IV and V stands respectively. Furthermore, approximate structural diameters were determined as a large category for I, III, IV and V stands while stand II had an intermediate-large class pre-tree marking to an intermediate-small class post-tree marking. The paired t-test results were not significant for tree numbers and growing stock changes for all species, and for beech, hornbeam, and velvet maple before and after tree harvesting in the whole stand. Therefore, the Gini index and the structural triangle method can be used for natural stand modeling, structural diversity designation, and for management practices in nature-oriented forestry strategies. [ABSTRACT FROM AUTHOR]

In order to evaluate the carbon storage capacity of pure stands and mixed stands of Fraxinus mandschurica and Larix olgensis plantation, 24-year-old stands were selected in Maoershan area, Shangzhi City, Heilongjiang Province, to measure carbon storage. Results showed that the ecosystem carbon storage of the mixed stand (246.15 t C·hm-2) was greater than those of the L. olgensis (232.01 t C·hm-2) and F. mandshurica (211.86 t C·hm-2) pure stands, but there were no significant differences (P > 0.05). In the three stands, carbon storage of soil layer and tree layer, which were the majority carbon storage in the ecosystems, were accounted for 71.6% ~ 80.1% and 17.3% ~ 24.5% respectively. The carbon storage of soil in the mixed stand was greater than those in two pure stands, but the differences were not significant (P > 0.05). The carbon storage of tree layer in the mixed stand was greater than those in the two pure stands, with a significant difference between the mixed stand and the F. mandshurica pure stand (P < 0.05). The carbon storage of the litter layer in F. manshurica was significantly less than the others (P < 0.05), while the storage of the understory vegetation was significantly greater (P < 0.05). Results show that the mixed stand of F. mandshurica and L. olgensis can increase the carbon fixation of ecosystem compared with the pure stands, which is suitable for building carbon sink forest. [ABSTRACT FROM AUTHOR]

In forest ecosystems nutrient cycling is a constant process that is carried out in different stages. Biological parts of this process begin with intake of nutrients from soil by trees, and continue until litter fall and litter decomposition. Nutrient retranslocation into the soil in pure and mixed stands of Parrotia persica (case study: Patom District of Kheyroud forest) was studied in this research. The nutrient level such as Carbon, Nitrogen, Phosphorous, Calcium, Magnesium and Potassium as well as several physical soil characteristics and biomass production was identified. Results indicated that nutrient retranslocation is quicker (in mixed stands of Parrotia persica, than pure stands, and nutrient retranslocation (With the exception of K), are significantly different between the stands. Additionally, it was observed that biomass production in pure stands is higher than mixed stands, indicating that decomposition in mixed stands is faster than pure stands. Furthermore, soil sample analysis results showed that the amount of all nutrients except Nitrogen and Potassium, in pure stands is more than mixed stands. [ABSTRACT FROM AUTHOR]