The impact of road disturbance on vegetation and soil properties in a beech stand,Hyrcanian forest

The ‘road-effect zone’ is a concept developed to describe the impact of road construction on the surrounding area. Although many aspects of the road-effect zone have been investigated, the road-effect zone on soil properties (pH, bulk density, soil moisture, electrical conductivity, organic matter (%), C (%), total N (%), available Na, Ca, Mg, P, and K), light regimes (leaf area index and canopy cover), and a Raunkiaer’s life-form classification of plants remains poorly understood, especially in oriental beech (Fagus orientalis Lipsky) forests. Hence, the main aims of this research were to estimate the extent of the road-effect zone and to identify the main environmental changes due to forest roads. Specifically, we aimed to evaluate road-effects on: (1) the composition of herbaceous species and tree regeneration (up to 100 m distance from the forest road); (2) the light regime; and (3) soil properties, potentially related to changes in ecosystem functions and composition. We observed that forest roads can have significant impacts on soil, stand characteristics, and vegetation composition. The estimated road-effect zone extended up to 30 m from the road edge. Landscape planners should be aware that road-effect zones can potentially influence the ecology and environmental conditions of an area up to 30 m from the road edge.     

The effect of single-tree selction system on soil properties in an oriental beech stand of Hyrcanian forest,north of Iran

A case study was conducted in beech forests of northern Iran to determine the effect of the created gaps on some soil properties in beech stand. Changes of soil properties in small (60 150 m 2 ), medium (151 241 m 2 ), large (242 332 m 2 ) and very large (333 550 m 2 ) gaps, as well as under closed stands were studied eight years after the gap creation. Soil samples were taken from three depths, 0 10, 10 20 and 20 30 cm. The gaps were different from their around undisturbed stands in terms of the following soil parameters: Mg +2 concentration of 0 10 cm at medium gap size, bulk density of 10 20 cm at very large gap size as well as K + and Ca +2 concentrations at 20 30 cm at small and large gap sizes, respectively. Furthermore, the size of the gaps had no effect on soil characteristics through the whole profile. Water saturation percent (Sp %) at 0 10cm as well as P and Mg +2 at 20 30 cm was different amongst undisturbed stands around different gap sizes. The center and the edges of the gap were different only in terms of organic carbon at the depth of 10 20 cm. Significant differences were observed between gaps andclosed canopy regarding P and Ca +2 at depth 0 10 cm and 10 20 cm, respectively. It can be concluded that applied silvicultural system for harvesting trees which created these gaps might be suitable for conservation and forest management in the region.     

Spatial and temporal variations in soil respiration in relation to stand structure and soil parameters in an unmanaged beech forest

Soil CO2 efflux (soil respiration) plays a crucial role in the global carbon cycle and efflux rates may be strongly altered by climate change. We investigated the spatial patterns of soil respiration rates in 144 measurement locations in a 0.5-ha plot and the temporal patterns along a 300-m transect in the 0.5-ha plot. Measurements were made in an unmanaged, highly heterogeneous beech forest during 2000 and 2001. We investigated the effects of soil, roots and forest stand structure on soil respiration, and we also assessed the stability of these spatial patterns over time. Soil temperature alone explained between 68 and 95% of the temporal variation in soil respiration; however, pronounced spatial scatter of respiration rates was not explained by soil temperature. The observed spatial patterns stayed remarkably stable throughout the growing season and over 2 years. The most important structural parameter of the stand was the mean diameter at breast height of trees within a distance of 4 m of the measurement locations (m-dbh4), which explained 10-19% of the variation in soil respiration throughout the growing season. Among the soil chemical parameters, carbon content (bulk as well as dissolved) and magnesium content explained 62% of the spatial variation in soil respiration. The final best model combining soil, root and stand structural parameters (fine root biomass, soil carbon content, m-dbh4 and soil water content) explained 79% of the variation in soil respiration, illustrating the importance of both biotic and abiotic factors.     

Threshold price as an economic indicator for sustainable forest management under stochastic log price

We seek the minimum harvest age and threshold price for sustaining forest management by constructing a stochastic dynamic programming model using a geometric mean-reverting process for log price dynamics. Three decisions—“Wait for harvest”, “Harvest & Plant”, and “Harvest & Abandon”—are assumed. The applied growth simulator is deterministic. Using the monthly time series data of sugi (Cryptomeria japonica) log price from 1975 to 2006, our analyses show that when the reverted mean is lower than the cost, the minimum harvest age increases as the current price approaches the threshold price, then declines. In other cases with a higher reverted mean, the minimum harvest age increases as the current or initial log price decreases. When the initial log price approaches the threshold price, the minimum harvest age tends to increase. These phenomena can be used to evaluate the possibility of management abandonment under a stochastic situation of log price dynamics.     

林分空间结构的研究

林分的空间结构分析是建立在相邻木空间关系基础上的原则,提出了最佳空间结构单元及其参数.用大小比数、混交度和角尺度等三种结构参数,分析了林分的空间结构,它们是描述林分空间结构的重要参数.     

林木光合生理生态研究概述

林木光合生理生态是当今一个研究热点问题。文章主要从光合动态、环境因子对光合特性的影响、叶绿素与光合作用的关系等几个方面,介绍了林木光合生理生态的研究现状。     

Spatial prediction of forest stand variables

This study aims at the development of a model to predict forest stand variables in management units (stands) from sample plot inventory data. For this purpose we apply a non-parametric most similar neighbour (MSN) approach. The study area is the municipal forest of Waldkirch, 13 km north-east of Freiburg, Germany, which comprises 328 forest stands and 834 sample plots. Low-resolution laser scanning data, classification variables as well rough estimations from the forest management planning serve as auxiliary variables. In order to avoid common problems of k-NN-approaches caused by asymmetry at the boundaries of the regression spaces and distorted distributions, forest stands are tessellated into subunits with an area approximately equivalent to an inventory sample plot. For each subunit only the one nearest neighbour is consulted. Predictions for target variables in stands are obtained by averaging the predictions for all subunits. After formulating a random parameter model with variance components, we calibrate the prior predictions by means of sample plot data within the forest stands via BLUPs (best linear unbiased predictors). Based on bootstrap simulations, prediction errors for most management units finally prove to be smaller than the design-based sampling error of the mean. The calibration approach shows superiority compared with pure non-parametric MSN predictions.     

红壤区生态公益林不同类型林分降雨及产流与产沙量研究

通过对湘中丘陵红壤区不同类型林分的定位观测,对林地不同年份因降雨量差异而产生的径流量、泥沙含量的差异进行对比分析.结果表明:降雨量较大的2010年林地的径流量、泥沙含量、径流系数均大于相对干旱的2009年;径流量、泥沙含量的大小与大雨量降雨的次数和降雨量密切相关.     

菇木林目标树择伐林窗的形成对土壤养分含量的影响

[目的]以浙江省庆元县菇木林为研究对象,探讨菇木林目标树择伐后形成的人工林窗对土壤养分含量和土壤质量的影响.[方法]在对照林分和择伐后林窗内设置调查样地,分层采集0～60 cm土层土壤样品,对比分析土壤养分元素含量和土壤pH值的变化情况.[结果]1)与对照相比,择伐6 a后林窗0～20 cm土层,土壤有机碳、全氮、水解...     

不同林龄水杉人工林下土壤微生物量的变化研究

研究了上海市水杉人工林林下土壤中有机碳、全氮和土壤微生物量碳氮含量.结果显示:沿海地区水杉人工林表层土壤(0～10cm)的有机碳和全氮含量均处于一个比较低的水平,随着林龄的逐渐增大,其含量逐渐变大.土壤微生物量碳占有机碳的比例在0.18%～1.42%,处于-个较低水平;土壤微生物量氮占全氮含量的0.19%～7.04%,...     

Spatial organisation of a bimodal forest stand

Many populations have a bimodal size distribution, even when composed of a single cohort. In developing forest stands, this pattern is usually attributed to asymmetric competition at canopy closure among trees which have access to the upper canopy and those which have failed to reach it. Nevertheless, alternative explanations for bimodality exist, and in sessile organisms spatial pattern analysis can be used to compare their predictions. A 0.25-ha plot was created in a maturing stand of Asiatic white birch (Betula platyphylla Sukacz.) in Central Kamchatka. All stems >1 cm diameter at breast height (DBH) were fully mapped. Mark correlation analysis revealed size compensation among stems up to 3.5 m apart, providing evidence that competition affected the distribution of stem sizes. The spatial pattern of trees was analysed using the pair correlation function g(r). Large trees (>20 cm DBH) had a dispersed distribution to which a Strauss soft-core Gibbs process model was fitted. This suggested that large trees interacted at scales up to 4.16 m. Small trees (1–20 cm DBH) were distributed randomly, but a cross-pair correlation analysis revealed a greater likelihood of occurrence beginning at 4.3 m from large trees, closely matching the modelled interaction distance. These results are consistent with the hypothesis that asymmetric competition is structuring this bimodal cohort of trees: large stems tend towards a dispersed pattern, exerting competitive effects at scales up to approximately 4 m, whereas smaller stems are more commonly found in the interstices within the pattern of large trees.     

Twenty-three years of stand dynamics in an old-growth Chamaecyparis forest in central Japan

Structures and dynamics of old-growth coniferous stands are affected by several types of disturbances including typhoons. We report the forest dynamics of four old-growth Chamaecyparis stands in central Japan that differ in the disturbance history of typhoons over a period of 23 years. The stem number, basal area and mortality were examined. In a predominant stand of C. obtusa (Sieb. et Zucc.) Endl., 24 % of the C. obtusa canopy trees died, mainly as a result of the severe damage of a strong typhoon that caused a single tree-fall gap and the following gap enlargements. In this stand, the total basal area decreased to 76.5 % of the initial value, although the mortality declined in recent years. In contrast, the other three stands decreased only slightly in the stem numbers (0.0–5.6 %) and increased in the basal areas of C. obtusa canopy trees. It is confirmed that the stand-level ingrowths of 300-year-old C. obtusa canopy trees could contribute to the increase in the stock of each stand. Our results support an idea that the dynamics of old-growth Chamaecyparis forests were greatly affected by typhoons. The stand structures will be gradually changed (with the processes of gap dynamics) and C. obtusa will continue to be dominant, potentially over hundreds of years.     

Fuel and stand conditions in an isolated, unmanaged forest landscape in central Oregon

? Mature, unmanaged forests in western North America provide important reference conditions for managers, yet little is known about fuel composition and the factors that influence fuel accumulation in such stands. Our objectives were to characterize fuels in a passively managed landscape of dry forests in central Oregon and identify environmental factors influencing fuel accumulation.

? Ordination techniques and analysis of variance revealed no statistical differences in total fuel loads across a wide range of environmental conditions.

? Individual fuel size classes, however, did vary by stand location and composition. Interior stands had more 1- to 100-h fuels and snags than stands at or near the edge, stands dominated by ponderosa pine had fewer small-diameter fuels and snags, lodgepole pine stands had more 1-h fuels and snags, and white fir stands had more 10-h fuels, duff, and snag basal area.

? Tree species, density and age, and years since last fire were the most important environmental variables, explaining 23% of the variation in fuels.

? Our results present further evidence that fuel composition is highly variable at many spatial and temporal scales. They also provide useful baseline information for managers of fire-prone western forests.

     

皆伐对杉木林土壤物理性质的短期影响

用环刀采集皆伐半年后的杉木林皆伐迹地土壤剖面0～5、5～10、10～15、15～20、20～25、25～30、30～35、35～40、40～45、45～50、65～70和90～95 cm土层的土样,测定其土壤容重、毛管孔隙度、非毛管孔隙度、总孔隙度和毛管持水量等。结果表明:随着土层深度的增加,皆伐迹地的土壤容重和毛管孔隙度增加,非毛管孔隙度波动性下降,总孔隙度和毛管持水量下降后微升;与杉木林地表土层的土壤相比,皆伐迹地表土层土壤的容重、孔隙度和毛管持水量均有所下降。     

湖州市主要林分类型枯落物和土壤持水能力

对湖州市7种主要林分类型植被的枯落物层持水性能和土壤层蓄水能力进行了研究.结果表明:7种林分类型林地枯落物层和土壤层的持水量存在差异,枯落物现存量变化范围为5.92～ 9.88 t/hm2,土壤总孔隙度的变化范围为49.00％ ～58.11％,土壤最大持水量的变化范围为1 934.8～2 324.4 t/hm2.枯落物最大持水量依次为针阔混交林＞常绿阔叶林＞疏林＞马尾松林＞灌木林＞杉木林＞毛竹林,林地水源涵养能力依次为针阔混交林＞常绿阔叶林＞疏林＞灌木林＞毛竹林＞马尾松林＞杉木林,毛竹林的林地持水能力要好于马尾松林和杉木林.全市非毛管总蓄水量为12 919.2万t,最大蓄水量为43 617.7万t.     

Traditional mule logging method in Hyrcanian Forest: a study of the impact on forest stand and soil

We inventoried plant regeneration and soil compaction along mule trails to evaluate damage to forest stands and regeneration follow-ing mule hauling before and after operations in Kheyrud Forest in the...     

不同栽培林龄和轮次的杨树人工林土壤理化性质

采用空间代替时间的方法,构建了不同栽培林龄和轮次的杨树人工林试验样地,测定了土壤主要物理化学性质.结果表明,不同栽培轮次土壤密度值表现为1轮11年生＞2轮9年生,随着林龄增加,土壤密度呈逐渐下降趋势,表现为2轮3年生＞2轮6年生＞2轮9年生,且各样地之间呈显著差异;土壤饱和持水量、毛管持水量、毛管孔隙度和总孔隙度在各样地之间的变化无明显差异,而土壤非毛管孔隙度的变化则呈显著差异,在不同林龄样地上呈极显著差异.试验结果还显示,表层0～10 cm土壤中各养分元素的含量都对应地高于10～ 30 cm土层的含量,而pH值则呈相反的变化趋势;在不同栽培轮次和林龄的杨树人工林样地上对应土层土壤养分元素无明显的变化规律.     

望天树人工林生长量及土壤理化性质

望天树是我国一级珍稀濒危保护植物,为了更有效地保护这一树种,在桂西南那坡县对29年生望天树人工林的生长量及土壤理化性质进行了研究。结果表明:林分平均胸径、平均树高和平均蓄积量分别为28.49cm、28.30m和440.5m3/hm2,净经济收入为39.65万元/hm2。林地0～100cm土层密度为0.819 8～1.174 3g/cm3,土壤总孔隙度为57.0%～66.3%,土壤通气度为16.8%～25.0%,土壤最大持水量、毛管持水量和最小持水量分别为46.7%～94.2%、34.1%～68.8%和20.8%～42.1%。0～40cm土层pH值为4.64～4.96,土壤有机质含量为29.58～70.70g/kg,土壤全N、全P和全K含量分别为1.15～2.71、1.38～1.56和13.27～15.31g/kg,速效N、P和K分别为157.68～327.42、0.32～1.21和9.93～23.12mg/kg。研究结果表明,29年生望天树人工林的生长量较高,林地土壤疏松、土壤通气性能良好、土壤肥力较高。因此,在类似该地区立地环境进行望天树的引种栽培具有较大的生物生产力。     

杉木林土壤化学性质对林分改造及不同坡位的响应

研究了林分改造对杉木林土壤化学性质的影响以及不同坡位间的土壤化学性质差异,以期为科学经营管理杉木人工林与有效利用土壤养分提供科学依据。通过引入6种乡土阔叶树种对广东省韶关市小坑林场的原有低效杉木林进行林分改造,并分别于2016年、2017年与2018年对样地不同坡位(上坡、中坡、下坡)的土壤进行采样,测定土壤化学性质。研究结果表明,样地土壤属酸性,pH值范围为3.60~4.36;林分改造期间,除土壤有效磷含量在2016年与2017年在不同坡位间无明显差异,其他养分含量均随坡位降低而显著增加;经过3年林分改造后,除土壤全钾含量和有效磷含量外,其余指标在各坡位均随着时间变化表现为先降后升。综合来看,林分改造对森林的土壤养分水平有一定程度的提高,且下坡位的土壤更加肥沃,说明针阔叶混交林有利于维持和恢复林地土壤肥力。     

广东四会贞山森林旅游区林分改造造林效果初探

根据广东省四会市大南山林场贞山林区生态林的现状及所处的特殊地理位置状况,按照建设森林公园、提高贞山风景区生态功能等级和景观质量的目标,规划设计了森林旅游区首期林分改造的树种选择及配置,初步分析了林分改造各树种的生长情况,展望了改造后的生态、景观前景,对今后林分改造提出建议。