Modeling of forest soil and litter health using disturbance and landscape heterogeneity indicators in northern Iran

This paper focuses on the indicators of soil and litter health, disturbance, and landscape heterogeneity as a tool for prediction of ecosystem sustainability in the northern forests of Iran. The study area was divided into spatial homogenous sites using slope, aspect, and soil humidity classes. Then a range of sites along the disturbance gradient was selected for sampling. Chemical and physical indicators of soil and litter health were measured at random points within these sites. Structural equation modeling(SEM) was applied to link six constructs of landscape heterogeneity, three constructs of disturbance(harvest, livestock, and human accessibility), and soil and litter health. The results showed that with decreasing accessibility, the total N and organic matter content of soil increased and effective bulk density decreased. Harvesting activities increased soil organic matter. Therefore, it is concluded that disturbances through harvesting and accessibility inversely affect the soil health. Unexpectedly, it was found that the litter total C and C:N ratio improved with an increase in the harvest and accessibility disturbances, whereas litter bulk density decreased. Investigation of tree composition revealed that in the climax communities, which are normally affected more by harvesting activities, some species like Fagus orientalis Lipsky with low decomposition rate are dominant. The research results showed that changes in disturbance intensity are reflected in litter and soil indicators, whereas the SEM indicated that landscape heterogeneity has a moderator effect on the disturbance to both litter and soil paths.

Long-term effect of fire on herbaceous species diversity in oriental beech (Fagus orientalis Lipsky) forests in northern Iran

We studied the long-term impacts of natural burning on herbaceous species diversity 37 years after a fire occurred in the Roudbar forests of Guilan Province, northern Iran. Numerous studies have examined short-term changes in understory vegetation following wildfire; however, very few long-term studies are available or changes inferred from retrospective studies based on chro- nosequences. For this study, 170 ha of forest （85 ha, burned areas; 85 ha, unburned areas） were surveyed. Because the 1000 m2 plots were too large for detailed measurements of herbaceous species, we determined a sub-sample size according to the Whittaker＇s nested plot sampling protocol and minimal areas method. Hence, sub-plots of 32 m2 were used for herbaceous species measurements, which consisted of percent cover of each species based on the Domin criterion. We measured plant diversity （Shannon-Wiener index）, spe- cies richness （Margalef＇s index）, and evenness （Smith-Wilson index）. Mean percent cover, together with diversity, richness and even- ness, increased markedly in burned areas compared to unburned controls. This suggests that the biodiversity of these forests could be restored within 37 years after fire. However, the abundance of invasive species such as Rubus fruticosus and Bromus benekenii increased significantly in burned areas, but these could be controlled by relevant silvicultural operations.

Observations on the Spermatogenic Cycle of the Grass Snake,Natrix natrix (Serpentes:Colubridae) in Northern Iran

The Grass Snake, Natrix natrix, is one of the non-venomous oviparous snakes of the family Colubridae, found in Mazandaran, a northern province of Iran. In order to study the spermatogenic cycle of this species in the area, sampling was done from April to November, and twenty-six male snakes were collected by hand during daylight hours. Testes were extracted from the specimens, and were fixed and prepared for histological examination. The results indicated that the spermatogenesis started in early June, November. The mean body length of the specimens was reached its height in August and September, and ended in measured 636.21 mm, and the mean volume of testes was 524.54 rnm3 and 569.06 mm3 for the right and left ones, respectively, and the mean weight of the testes was 0.051 g Spermatogenesis in this species is aestival and sperms are stored for use in the year following production.

Effect of thinning on growth of Acer velutinum Boiss. in northern forests of Iran

It has become necessary to develop stands of fast growing endemic species in the Caspian forests because of their reduction in area and the domestic demand of timber processing industries in Iran. Acer velutinum, an endemic species in Iran, is often planted in monocultures or in a mixture with other endemic species. Our study was conducted on A. velutinum planted in Berenjestanak(control plots) and Chaibagh(thinned plots) in northern Iran in 1991. A randomized sampling method with circular sampling plots of 100 m2was used to measure diameter and height of trees. The results show that the diameter of trees in thinned stands was 19.98 cm and in the control stands 13.84 cm, while the mean heights were 18.33 and 17.46 m, respectively. The mean basal area in thinned stands was 30.74 m2and in the control 15.70 m2per ha. The results of Student’s t tests indicate that there are significant differences at a probability level of 99.9% between the two variously treated stands in diameter(d), height(h), basal area, volume growth and the stability coefficient. We conclude that tending operations with suitable intensity in different time periods are recommended to obtain stable stands.

Biostratigraphy and Mass Extinction Pattern across the Cretaceous/Paleogene Boundary, Northern Alborz, Iran

High resolution sampling across the Cretaceous/Paleogene boundary (K/Pg) at the Galanderud section in northern Iran provides the most expanded and continuous section for us to consider biostratigraphy and the mass extinction pattern of Cretaceous planktic foraminifera. Based on planktic foraminifera, four biozones and five sub-biozones have been identified across the K/Pg boundary. These biozones include the Abathomphalus mayaroensis Biozone (Plummerita hantkeninoides subbiozone), the Guembelitria cretacea Biozone (including two sub-biozones: the Hedbergella holmdelensis and the Parvularugoglobigerina longiapertura), the Parvularugoglobigerina eugubina Biozone (including two subbiozones: the Parvularugoglobigerina Sabina and the Eoglobigerina simplicissima) and finely the Parasubbotina pseudobulloides Biozone. Planktic foraminiferal extinction occurred over a brief period, with 3% of the species disappearing in the late Maastrichtian, and 72% of the species becaming extinct at the K/Pg boundary. About 25% of the species survived into the early Danian. Extinction of 73% of the species at the K/Pg boundary is very compatible with the effect of a large asteroid impact.

伊朗Lurestan-Fars地区晚白垩世微相与沉积环境演化

中东阿拉伯地区晚白垩世以来发育巨厚的碳酸盐岩沉积,是油气的有利储层,其沉积环境的演化长期受到国际学术界的广泛关注。以阿拉伯北缘Lurestan-Fars地区(现今伊朗境内)3条剖面(Khoramabad-AD剖面、Kermanshah-KM剖面和Hkhormoj-HM剖面)为研究对象,对上白垩统Savark组、Ilam组、Gurpi组碳酸盐岩地层开展了详细的野外观察和岩石薄片分析。基于岩石结构、生物组合以及沉积构造等特征,将碳酸盐岩划分为13种沉积微相,形成于外缓坡、中缓坡和内缓坡3种沉积环境。整体来看,Santonian时期3条剖面均处于深水的外缓坡环境,但Campanian时期,在AD剖面和KM剖面沉积环境由外缓坡转变为内缓坡环境,代表一次古水深突然变浅事件;但同一时期,HM剖面沉积环境仍处于外缓坡环境。考虑到3条剖面距离蛇绿岩带之间的差异,认为Campanian时期Lurestan地区AD剖面和KM剖面记录的古水深变浅事件与北侧蛇绿岩仰冲作用相关,而Fars地区HM剖面距离蛇绿岩带距离太远,仰冲作用对该地区影响较弱,因而古水深未发生明显改变。

Bark content variations and the production of Populus deltoides as a source of bioenergy under temperate climate conditions

Bark biomass as an energy source has a high economic value.Bark content variations and production helps recognize the potential of this bioenergy source spatially before harvesting.The percentage of fresh and dry bark in Populus deltoides grown under a monoculture system was examined in the temperate region of northern Iran.Diameter at breast height(DBH)and total height data were analyzed based on an initial inventory.Ten sample trees were felled,separated into 2 m-segments,and weighted in the field.A 5-cm-thick disc from each segment was extracted for determining fresh and dry bark percentages.These were statistically significantly different in disc diameter classes and decreased with increasing disc diameters.Bark percentage of the disc classes ranged from 21.8 to 24.4%in small-sized diameters to 8.1-9.3%in large-sized diameters.The differences between fresh and dry bark percentages depended on water content variations.Allometric power equations were fitted to data of fresh and dry bark percentages and disc diameters as well as DBH.The values of R~2 ranged from 0.89 to 0.90.In addition,allometric power equations provided the best fits for relationships between total stem dry biomass,dry bark biomass,and DBH,R~2=0.986 and 0.979 for the total stem dry biomass and stem dry bark biomass,respectively.The allometric models can be used to estimate bark percentage and bark production of P.deltoides in segments and for the whole stem for a wide range of segment diameters(8-44 cm)and DBH(15-45 cm).

伊朗北部阿哈尔地区土地利用信息的遥感分类与制图

遥感作为目前快速实现全球或大区域对地观测的最佳方法,在"一带一路"沿线地区地表信息获取方面具有重要的作用。总结了遥感技术在伊朗北部土地利用分类与制图的流程和方法,在土地利用分类体系、遥感分类方法和成果制图3个方面进行了研究。通过土地利用信息遥感分类标志,建立非接触的土地利用信息分类工作方法,保证了良好的工作精度。进行了伊朗北部地区土地利用信息的遥感制图,获取了该地区土地利用状况,为我国矿业企业与地质调查部门开展"一带一路"区域合作提供了技术支撑和决策依据,为开展境外土地利用信息的提取与制图工作提供了案例。

伊朗德黑兰地铁1号线北延线典型区间事故工况模拟

伊朗德黑兰地铁1号线北延线区间线路的形式为单洞双线,且坡度最大为50‰,事故工况下的通风组织尤为重要。本文利用Stess模拟软件,对典型区间事故工况下的通风模式进行了模拟计算,寻求事故工况下的通风方案和设备运行模式,以确保事故通风设计满足地铁规范对事故区间断面风速的要求。