Improved recruitment and early growth of Scots pine (Pinus sylvestris L.) seedlings after fire and soil scarification

The success of seedling recruitment of Scots pine (Pinus sylvestris L.) is strongly dependent on soil surface properties, such as humus depth and moisture content. In an undisturbed forest floor, seedlings are seldom able to become established due to the high incidence of desiccation in the organic soil layer. Methods that remove the organic soil layer are often necessary to improve the availability for radicles to reach the more stable moisture regime in the mineral soil. In this study we investigated pine-seedling establishment after mechanical soil scarification, burning of litter (O_L) and burning of litter and humus (O_L and O_FH) in two mature pine stands in Germany. The herbaceous layer of the first stand was dominated by grasses (Molinia caerulea L. and Deschampsia flexuosa L.), whereas the herbaceous layer of the second stand was dominated by blueberry (Vaccinium myrtillus L.). Pine seeds were placed in experimental plots, and seedling numbers and heights were recorded at regular intervals. All treatments that removed organic soil resulted in higher seedling counts than did the undisturbed forest floor. The highest seedling counts were found on scarified and severely burnt plots, whereas seedling counts were lower on lightly burnt plots. Seedlings were significantly taller on burnt plots. This study shows that pine regeneration is stimulated by fire, not only in boreal forests, but also under central European conditions. With the expectation of higher fire frequency in the near future due to climatic changes, natural regeneration and succession on burnt sites should receive more focus in forest management and research.     

Geological controls on conifer distributions and their implications for forest management in Finnish Lapland

Abstract

Soil water and nutrient regimes of naturally established old-growth conifer stands and those of intensively managed Norway spruce [Picea abies (L.) Karst.] sites were assessed over a range of lithological provinces in Finnish Lapland. Soil dielectric permittivity (ε), as a measure of soil water content (θ _v) and soil electrical conductivity (σ _a), as a measure of soil solute content, were species specific, such that high soil θ _v>0.27 cm³cm^?3 (ε>15) constitutes an edaphic constraint for Scots pine (Pinus sylvestris L.) and low soil solute content (σ _a<0.5 mS m^?1) is constraining for Norway spruce. The spatial pattern of the soil θ _v was temporally stabile, such that intraseasonal and interseasonal soil θ _v was significantly higher in silty tills of spruce stands compared to sandy tills of pine stands. Scots pine was the only conifer on tills derived from felsic rocks of Hetta granite (HG) and Lapland granulite (LG). Norway spruce dominated on tills derived from the mafic rocks of Lapland greenstone belt (LGB), but tills of LG and HG constitute a dispersal barrier for spruce. Mechanical site preparation (MSP) with ploughing (Marttiini) was not able to amend soil θ _v to meet site requirements of Scots pine at former spruce sites. MSP resulted in significant reduction in soil nutrient content such that untreated control σ _a>tilt/shoulder σ _a>trench σ _a. The results imply that MSP treatments through which cross-contour tracks are created pose a risk to the sustainability of soil quality in Lapland.     

Effects of temperature on the site productivity of Pinus sylvestris and lodgepole pine in Finland and Sweden

The influence of temperature regime on forest production in the northern boreal forest was studied by analysing the variation in site index for 20 provenance tests of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in Finland and Sweden with respect to temperature. The site indices were regressed with several different temperature variables, which were obtained from interpolated monthly averages over 30 years from permanent meteorological stations nearby. There were strong correlations between all tested temperature variables and site index (r = 0.80–0.94). Site fertility influenced site index to some extent but the slope of the test sites did not. An increase in temperature sum from 600 to 1200 degree days (corresponding to an increase of the mean temperature in July from 13 to 15°C) was associated with an increase in site index of Scots pine (Pinus sylvestris L.) from 12.2 to 21.6 m (77%). Such an increase in site index can be assumed to correspond to an increase of 6.5 m³ ha^?1 wood (183%) in mean annual increment. The effect of temperature was greater on poor sites than on fertile sites, and in harsh temperature regimes than in mild.     

Influence of Tree Roots on Nitrogen Mineralization

This study compared the total carbon (C), mineral nitrogen (N) contents and N mineralization potentials of the rhizospheric and bulk soils, collected at two depths in three forest sites in France. The site at Breuil is a comparative plantation of different species with or without fertilization, the Fougères site is a time sequence of four Fagus sylvatica L . stands including a limed plot, and the Aubure site is a comparison between adjacent young and old Picea abies. (L.) Karst stands with different nitrifying activity. Mineral N was extracted from fresh soil with K 2 SO 4 and after laboratory incubation at 15°;C for 2 days or 1 week. The moisture, C and N contents of the rhizospheric soil were higher than in the bulk soil in the A 1 horizon, but only slightly higher or similar in A 1 B horizons. Soil-extractable NH 4 and net mineralization were much larger in the rhizospheric soil than in the bulk soil. Soil-extractable NO 3 and net nitrification were not significantly different. Soil-extractable NH 4 and net N mineralization were linearly and positively related to the soil C (or N) contents, but the relationship was stronger and the amount of mineral N per gram of carbon was higher for rhizospheric soil. This suggests that the quality of rhizospheric carbon should be taken into account. Net N mineralization was negatively related to the soil C/N ratio. In summary, tree roots appear to have a strong influence on N transformation in soils.     

长期粗放经营毛竹林土壤微生物群落演变特征

[目的]通过分析土壤微生物生物量及群落结构的演变趋势,筛选影响土壤微生物群落的关键环境因子,揭示土壤微生物群落对毛竹林长期粗放经营的响应机理。[方法]选取不同粗放经营年限(5 a、9 a、15 a、18 a)毛竹林,以天然马尾松林(Masson pine,MP)作为对照,采用磷脂脂肪酸(Phospholipid fatty acids,PLFA)分析方法表征土壤微生物量及群落结构。[结果]结果表明,毛竹林土壤微生物总PLFA含量以及细菌、真菌、放线菌等PLFA含量均显著低于马尾松林(P0.05),但不同经营年限毛竹林之间没有显著差异。土壤碱解氮及有效磷含量对土壤微生物总PLFA含量以及细菌、真菌、原生动物等PLFA含量影响显著(P0.05),而土壤碱解氮、p H值以及有机质含量对放线菌PLFA含量影响显著(P0.05)。长期粗放经营过程中毛竹林土壤微生物丰富度及多样性均呈逐渐下降趋势。非度量多维尺度转换排序(Non-metric multidimensional scaling,NMDS)分析结果表明,毛竹林土壤微生物群落结构与马尾松林有明显区分(R=0.388 1,P=0.009)。土壤含水量、碱解氮、有效磷以及p H值合计解释了90.28%的微生物群落结构变异量,其中土壤含水量、碱解氮、有效磷贡献显著(P0.05)。[结论]长期粗放经营降低了毛竹林土壤微生物量,改变了群落结构,其生态风险还有待于进一步评估。     

Analysis of soil moisture variation by forest cover structure in lower western Himalayas, India

Soil moisture affects various hydrological processes, including evapotranspiration, infiltration, and runoff. Forested areas in the lower western Himalaya in India constitute the headwater catchments for many hill streams and have experienced degradation in forest cover due to grazing, deforestation and other human activities. This change in forest cover is likely to alter the soil moisture regime and, consequently, flow regimes in streams. The effect of change in forest cover on soil moisture regimes of this dry region has not been studied through long term field observations. We monitored soil matric potentials in two small watersheds in the lower western Himalaya of India. The watersheds consisted of homogeneous land covers of moderately dense oak forest and moderately degraded mixed oak forest. Observations were recorded at three sites at three depths in each watershed at fortnightly intervals for a period of three years. The soil moisture contents derived from soil potential measurements were analyzed to understand the spatial, temporal and profile variations under the two structures of forest cover. The analysis revealed large variations in soil moisture storage at different sites and depths and also during different seasons in each watershed. Mean soil moisture storage during monsoon, winter and summer seasons was higher under dense forest than under degraded forest. Highest soil moisture content occurred at shallow soil profiles, decreasing with depth in both watersheds. A high positive correlation was found between tree density and soil moisture content. Mean soil moisture content over the entire study period was higher under dense forest than under degraded forest. This indicated a potential for soil water storage under well managed oak forest. Because soil water storage is vital for sustenance of low flows, attention is needed on the management of oak forests in the Himalayan region.     

广西大青山西南桦人工林土壤养分特征及其与立地生产力的关系

[目的]探讨西南桦人工林对土壤的适应性及土壤养分特征,揭示土壤养分状况与立地生产力的关系,为其造林地选择及人工林养分管理提供参考。[方法]在广西大青山林区西南桦人工林内设置47块600 m2的典型样地,调查常规测树因子,采集土壤样品,测定10项常规土壤化学性质指标;按照土壤养分分级标准评价土壤养分状况,基于立地指数将样地分为高产和低产组,进一步比较分析两组立地间各养分指标的差异性,探讨土壤养分对立地生产力的影响。[结果]表明:广西大青山西南桦人工林地土壤绝大部分为强酸性,有机质、有效N、全N含量中等偏上,有效P甚缺,其它养分含量中等偏下。高产和低产立地间土壤有机质和全K含量均呈极显著差异(P0.01),有效N含量差异显著(P0.05)。[结论]西南桦对于低pH值、低P含量的土壤具有较强的适应性;有机质、全K和有效N含量是影响广西大青山西南桦人工林立地指数的关键土壤养分因子。     

Enhancing the regeneration of compacted forest soils by planting black alder in skid lane tracks

Soil compaction due to the use of heavy machinery for timber harvesting has become a widespread problem in forestry. However, only few studies deal with the regeneration of compacted forest soils. In the present study, we examined the potential of accelerating soil regeneration by planting black alder trees (Alnus glutinosa (L.) Gaertn.) in skid lane tracks. In 2003, seedlings were planted into the rut beds of severely compacted skid lanes in two Swiss forest sites. In addition, some of the ruts were filled with compost. In 2009 and 2010, we assessed the success of these measures by analysing physical parameters of soil structure (bulk density, total and coarse porosity and air permeability), root densities and tree growth. Tree growth was exceptionally strong on the skid lanes. Total and coarse soil porosity and air permeability showed significant increase in planted skid lanes as compared to untreated control subplots, approaching values found for untrafficked soil in the immediate vicinity. All soil physical parameters were closely correlated to root mass density. Compost application enhanced tree growth and soil structure regeneration on one site, but had a retarding effect on the other site. Planting black alders has great potential as an environmentally friendly measure to accelerate the structural regeneration of compacted forest soils in temperate humid climates.     

Predicting regeneration establishment in Norway spruce plantations using a multivariate multilevel model

This study predicts the regeneration establishment on 3-year-old Norway spruce (Picea abies (L.) Karst.) plantations in southern Finland using regeneration survey data. Regeneration establishment was described by seven response variables: number of planted spruces, natural Scots pines (Pinus sylvestris L.), natural spruces, natural seed-origin birches (Betula pubescens Ehrh. and B. pendula Roth.) and other broadleaves (i.e. sprout-origin birches and other broadleaves than birch), as well as height of crop-tree spruce and dominant height of broadleaves. Due to the multivariate (several responses for each plot) and multilevel (plot, stand, municipality, forest centre) structure, regeneration establishment was modelled by fitting a multivariate multilevel model with explanatory variables such as temperature sum, site fertility, soil quality and method of site preparation. In the model, the numbers of tree seedlings were modelled using over-dispersed Poisson distributed equations, and the tree heights were modelled using normally distributed linear equations. The estimated fixed and random parameters of the equations were logical, and there was no serious bias in predicting the regeneration establishment in the independent test data set. This modelling approach can be used to predict the regeneration establishment stochastically by taking into account the large unexplained variation in regeneration models.     

The influence of soil scarification on the turn‐over rate of slash needles and nutrient release

The effect of soil scarification on decomposition of green Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) needles and mineral nutrient release was investigated. The treatments studied were ploughing, disk trenching, mound on inverted humus and untreated control. The study was conducted on two clear‐felled sites with different ground moisture conditions, located in south Sweden. The needles decomposed and released their contents of N and Ca considerably faster on scarified areas than on untreated ones. For P, Mg and especially K, only minor differences between scarified and untreated areas were established. At the wet site, needle decomposition and nutrient mineralization were generally affected to the same extent by all three scarification methods studied. At the dry to fresh site, mounding and ploughing enhanced needle decomposition and nutrient mineralization more than disk trenching. The effect of different scarification methods on the long‐term production capacity of soils is discussed.     

Herbicides and planting date affect early performance of container-grown and bare-root loblolly pine seedlings in Alabama

The survival of bare-root and container-grown loblolly pine (Pinus taeda L.) seedlings exceeded 90% when outplanted in March at two sites in Lee County, Alabama. At both sites, soil moisture and seedling survival were greater in March than in May. A March herbicide application reduced weed biomass by 75–80% at both sites. At the moist site, herbicide application did not affect survival. However, at the drier site, a reduction in weed biomass increased both the percent soil moisture and the survival of May-planted bare-root seedlings. When soil moisture at planting time was less than 13% on a dry weight basis container-grown seedlings survived better than bare-root seedlings. At both sites, reduced weed competition resulted in greater seedling heights and diameters.Alabama Experiment Station Journal Series No. 9-85802.     

Sitka spruce site index in response to varying soil moisture and nutrients in three different climate regions in Ireland

We examined the relationships between Sitka spruce (Picea sitchensis (Bong.) Carr.) site index, windspeed, former land use, soil moisture and soil nutrients with a view to identifying factors limiting the growth potential of the species in three climate regions in Ireland. We selected plantations covering three climate regions (delineated on the basis of ‘growing season’ balance of precipitation and potential evapotranspiration; representing dry, moist and wet climate regions) located on sites representing the range of soil moisture regimes (SMR), soil nutrient regimes (SNR), and land use types found throughout Ireland. Site index of Sitka spruce varied among climate region, with significantly lower site index associated with the wet climate region mainly due to the deterioration in edaphic conditions and adverse climatic conditions. The effect of edaphic variables (SMR, SNR) on site index was consistent across climate regions, site index increasing with increasing SNR, and decreasing with excess moisture or moisture deficit. Site index reached a maximum on fresh/very rich sites in the dry and moist climate regions and on moist/rich sites in the wet climate region. In the dry climate region, water supply (SMR) was the most important variable regulating growth, in wetter windier climates nutrient supply (SNR) was the most important factor, accounting for 69% of the variation in site index. The study has allowed region-specific recommendations to be made for successful plantation establishment in Ireland and for countries with similar climatic regions.     

鼠茅草间作对油茶林地土壤养分及酶活性的影响

[目的]探索油茶林间作鼠茅草对土壤质量的影响,为油茶林地的科学经营提供参考。[方法]采用随机定点取样法,测定分析鼠茅草腐解过程中油茶林地0~20 cm耕作层土壤含水量、养分含量及酶活性指标的动态变化。[结果]鼠茅草间作对油茶林地0~20 cm耕作层土壤含水量、养分含量及酶活性影响显著。与对照相比,7—10月鼠茅草间作的土壤含水量平均增幅达39.62%;鼠茅草间作不仅显著提高了油茶林地0~20 cm耕作层土壤有机质、全氮、全磷及全钾含量,而且也提高了土壤中的水解性氮、有效磷与速效钾的含量,其中,有效磷增幅最显著,在8月下旬为对照组的9倍;鼠茅草间作对油茶林地土壤脲酶、酸性磷酸酶与过氧化氢酶的活性影响显著,对蔗糖酶活性影响不显著。[结论]鼠茅草间作经营一定程度上提高了油茶林地土壤肥力水平,对油茶林地土壤改良和可持续生产具有积极的作用。     

Long-term dynamics of a mixed conifer stand in Slovenia managed with a farmer selection system

The single-tree selection system is an important option for management of Norway spruce (Picea abies (L.) Karst.) and silver fir (Abies alba Mill.) forests because it provides continuous cover, requires low investments for tending, and promotes natural regeneration as well as high stand resistance and elasticity. It is often regarded as a very conservative system that usually results in only minor spatiotemporal changes in forest structure and composition. We studied management history, structural changes, regeneration dynamics, and light climate of a traditional single-tree farmer selection silver fir-Norway spruce forest (site typology Bazzanio-Abietetum). Stand structure was analyzed on five 0.25 ha permanent plots in 1994, 2001, and 2008. Regeneration density and height growth, forest floor vegetation, and light climate were also assessed on 1.5 × 1.5 m regeneration subplots in 2001 and 2008. Tree cores extracted from dominant trees from both species in two plots were used for reconstructing stand history and age structure of the canopy layer. We documented the forest response to three types of selection management regimes: excessive, normal, and conservative. Excessive management with harvest intensity significantly above the increment was documented until the late 1950s, including two peaks of heavy fellings (diameter limit cut) in the 1880s and 1930s, which favoured establishment of Norway spruce and released regeneration. The period that followed was characterized by normal selection management, but was nevertheless marked by a decline of silver fir as a result of air pollution and several droughts. This led to sanitary fellings that were carried out from the late 1970s to the early 1990s. In the last two decades conservative management followed, which led to suppression and decline of regeneration, especially of Norway spruce, and loss of selection structure. Although we recorded lower regeneration potential of silver fir compared with Norway spruce within the seedling category, silver fir outcompeted Norway spruce within the small-sized tree category (1 cm < dbh ? 10 cm) because of its superior height growth in low light levels (diffuse light <6%) and occupied a greater share of the canopy. Nevertheless, we anticipate that over the long-term the low light regime will also cause regeneration decline of silver fir and broadleaves. Our research revealed significant structural changes in a single-tree farmer selection forest during the last 150 years. These were a result of variable management regime and environment. A farmer single-tree selection system could better mimic the natural disturbance regime if spatiotemporal combinations of diverse felling regimes would be used.     

林分结构调整对云南松次生林生长和土壤性质的影响

[目的]探究云南松林结构调整对林木生长和土壤性状的影响,为云南松林保护和利用提供科学依据。[方法]按照森林抚育规程对林分进行结构调整,采用典型取样法对比分析林分结构调整前后土壤性质和林木生长状况的差异。[结果]云南松林结构调整后,(1)结构调整样地单株蓄积量比对照样地提高了近60%,树高和胸径提高幅度均在15%以上,林下天然更新植株数量是对照样地的3.1倍;(2)结构调整后林内植物种类增加,林下灌木层和草本层盖度分别提高了63.3%和22.7%,灌木层和草本层平均高度分别提高了24.7%和17.9%;(3)结构调整样地现存凋落物量显著下降,与对照相比下降了20.4%,土壤表层温度、有机质含量、基础呼吸和土壤微生物生物量显著提高,土壤其他性质参数变幅相对较小。[结论]林分结构调整可显著提高云南松生长量,有利于云南松较大径级林木的培育;促进了云南松林下更新和林下植被发育,有利于林分群落结构的形成;提高了土壤微生物数量和活性,加速了土壤有机质转化,研究揭示林分结构调整促进了云南松林土壤—植物系统正反馈作用。     

Spatial distribution of late-successional coniferous species regeneration following disturbance in southwestern Québec boreal forest

Remnant tree stands left intact following a disturbance constitute the sole seed banks available for regeneration of coniferous species that neither bear serotinous cones nor reproduce vegetatively. The success of regeneration of tree species on these disturbed sites is, therefore, dependent on the distance from potential seed sources. The regeneration of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss) and white cedar (Thuja occidentalis L.) was studied at two sites in Québec’s southwestern boreal forest in order to quantify the influence of remnant stands on spatial distribution of regeneration. The first site is located in an area that burned in 1944 while the second site is located in an area that was clear-cut in the mid-1980s. Canonical correspondence analyses were used to determine the respective contributions of environmental data and spatial variables to the pattern of spatial distribution of regeneration. The results reveal that distance from a remnant stand is the most important variable in explaining spatial distribution of regeneration when compared to environmental variables such as soil type, drainage, slope and altitude. The plots of regeneration density against distance from a remnant stand for both the burned site and logged site show that regeneration density decreases abruptly with distance from a remnant stand. Furthermore, spatial autocorrelation analyses (Moran’s I) indicate that even small remnant zones can significantly influence the pattern of spatial distribution of regeneration for the three species studied. The results presented here suggest that where preestablished regeneration is not abundant enough, alternative silvicultural systems such as strip clear-cutting or seed-tree systems could be used instead of cuts with protection of regeneration and soils (CPRS).     

Oak decline in the Boston Mountains,Arkansas, USA: Spatial and temporal patterns under two fire regimes

A spatially explicit forest succession and disturbance model is used to delineate the extent and dispersion of oak decline under two fire regimes over a 150-year period. The objectives of this study are to delineate potential current and future oak decline areas using species composition and age structure data in combination with ecological land types, and to investigate how relatively frequent simulated fires and fire suppression affect the dynamics of oak decline. We parameterized LANDIS, a spatially explicit forest succession and disturbance model, for areas in the Boston Mountains of Arkansas, USA. Land type distribution and initial species/age class were parameterized into LANDIS using existing forest data. Tree species were parameterized as five functional groups including white oak (Quercus alba L., Quercus stellata Wangenh., Quercus muehlenbergii Engelm.), red oak (Qurecus rubra L., Quercus marilandica Muenchh., Quercus falcata Michx., Quercus coccinea Muenchh.), black oak (Quercus velutina Lam.), shortleaf pine (Pinus echinata Mill), and maple (Acer rubrum L., Acer saccharum Marsh.) groups. Two fire regimes were also parameterized: current fire regime with a fire return interval of 300 years and a historic fire regime with an overall average fire return interval of 50 years. The 150-year simulation suggests that white oak and shortleaf pine abundance would increase under the historic fire regime and that the red oak group abundance increases under the current fire regime. The black oak group also shows a strong increasing trend under the current fire regime, and only the maple group remains relatively unchanged under both scenarios. At present, 45% of the sites in the study area are classified as potential oak decline sites (sites where red and black oak are >70 years old). After 150 simulation years, 30% of the sites are classified as potential oak decline sites under the current fire regime whereas 20% of the sites are potential oak decline sites under the historic fire regime. This analysis delineates potential oak decline sites and establishes risk ratings for these areas. This is a further step toward precision management and planning.     

Carbon and nitrogen dynamics in topsoils along forest conversion sequences in the Ore Mountains and the Saxonian lowland, Germany

Carbon and nitrogen stocks and their medium-term and readily decomposable fractions in topsoils were compared in relation to soil microbial biomass and activity along sequences from coniferous to deciduous stands. The study was carried out in the Ore Mountains and the Saxonian lowland, representing two typical natural regions in Saxony, Germany. In accordance with current forest conversion practices, the investigation sites represent different stands: mature conifer stands of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) (type A); Norway Scots spruce and pine with advanced plantings of European beech (Fagus sylvatica L.) or European beech/Common oak (Quercus petreae Liebl.) (type B); and mature deciduous stands of European beech and European beech/Common oak (type C). The investigated forest sites can be grouped into three silvicultural situations according to the development from coniferous stands to advanced plantings and finally mature deciduous forests (chronosequence A–B–C). The organic layer (L, F and H horizons) and uppermost mineral soil (0–10 cm) were analysed for potential C mineralisation, microbial biomass, concentrations of total C and N (TOC and TN) and for medium-term and readily decomposable C and N fractions, obtained by hot- and cold-water extraction respectively. The results showed an increase in organic layer thickness and mass as well as TOC and TN stocks along the forest sequences in the lowland. Yet, underplanted sites with two storeys revealed higher organic layer mass as well as TOC and TN stocks as compared to coniferous and deciduous stands. Stocks of hot- and cold-water-extractable C and N in relation to microbial biomass and its activity revealed a high turnover activity in deeper organic horizons of deciduous forests compared to coniferous stands. The stand-specific differentiation is discussed in relation to microbial biomass, litter quantity and quality and forest structure, but also with respect to the site-specific climatic factors and water budget as well as liming and fly-ash impacts. Results indicate higher dynamics in deciduous stands in the lowland especially during the initial turnover phase. The elevated microbial activity in deeper organic horizons of deciduous litter-influenced sites in spring is discussed as a specific indicator for long-term C sequestration potential as besides C mineralisation organic compounds are humified and thus, can be stored in the organic layer or in deeper soil horizons. Due to liming activities, stand-specific effects on organic matter turnover dynamics have evened out today in the Ore mountain region, but will presumably occur again once base saturation decreases. Here, the stand-specific effect on microbial biomass can currently be seen again as C_mic in the L horizon increased from spruce to beech. Our study sites in the lowland revealed no significant fly-ash impact. Differences between sites were evaluated by calculating the discriminance function. TOC and TN as well as medium-term degradable C and N were defined in this study as indicators for turnover dynamics along forest conversion sites.     

Effect of micro-environmental factors on natural regeneration of <Emphasis Type="Italic">Sal</Emphasis> (S<Emphasis Type="Italic">horea robusta</Emphasis>)

Micro-environmental factors viz., soil moisture and light intensity are important factors that affect natural regeneration in forests. These factors vary spatially depending on the overhead canopy density of the forest. The present study focused on studying the effect of variation of soil moisture and light intensity on natural regeneration of sal species (Shorea robusta) under different micro-environments due to overhead canopy of varying forest density. Experimental plots of 40m× 40m size were laid under different overhead canopy densities in a small sal forested watershed in the foot hills of Himalayas in Nainital District of Uttarakhand State, India. The plots were monitored on a long term basis for soil moisture at multi depths, light intensity and natural regeneration of sal. The results of the study revealed that the natural regeneration was highest under C1 (up to-0.30) canopy followed by C2 (0.30–0.50), and C3 (0.50–0.70) canopies. The C3 canopy showed the dying back of sal shoots over 4 years of study. The highest R² value of linear regression between incremental score of plot regeneration and average soil moisture content was obtained as 0.156 for average soil moisture content during non-monsoon months at 100 cm depth. The R² value between incremental score of plot regeneration and annual average light intensity was obtained as 0.688 which indicated that the regeneration is largely dependent on the light intensity conditions during the year. The multiple linear regression analysis between the incremental score of regeneration and the average light intensity and average soil moisture content revealed that that about 80% of variation in regeneration is explained by both the factors.