Effects of thinning on wood production, leaf area index, transpiration and canopy interception of a plantation subject to drought

We conducted thinning trials in a 5-year-old Eucalyptus globulus ssp. globulus Labill plantation near Warrenbayne, northeastern Victoria, Australia, where soil salinization and waterlogging are common, and assessed treatment effects on tree growth, water use and survival. Half-hectare plots were thinned from the original density of 1100 stems ha(-1) to densities of 800, 600 and 400 stems ha(-1), and stem diameter increment, leaf area index, transpiration, canopy interception and depth of tree water source monitored for 21 months. Two drought periods occurred during the study, rainfall was 30% below the long-term average and there was severe mortality in all three plots. Analysis of deuterium abundance in soil and xylem water indicated that the trees accessed water only from the top meter of the soil profile. Transpiration rates were higher in the most heavily thinned plot than in the least thinned plot, which underwent a reduction in basal area during the study. The most heavily thinned plot increased in basal area by 10% during the study. Edge trees had significantly greater diameters than trees from the middle of the plots.     

Dynamics of leaf area index and canopy openness of three forest types in a warm temperate zone

Deciduous broad-leaved forests (DBF), Larix principis-rupprechtii (LF) and Pinus tabulaeformis plantations (PF) are three typical forest communities in the warm temperate zone of the Dongling Mountains. In this study, we used an indirect method, hemispheric photography, to measure and analyze the dynamics of leaf area index (LAI) and canopy openness of the three forest communities. The results show that the LAI values of DBF and LF increased gradually with plant growth and development. The highest LAI value appeared in August, while canopy openness changed inversely with LAI. The lowest value appeared in November. DBF maintained a higher LAI in August and had a more open canopy in November compared with LF. For PF, we observed little changes in the LAI and canopy openness which was attributed to the leaf retention of this evergreen species. However, a similar relation between LAI and canopy openness was found for the three forest communities: canopy openness varied inversely with LAI. The relation is exponential and significant. Therefore, canopy openness is a good indicator of LAI in forests. This result can be used to test the validity of the LAI based on remote sensing and to provide a reference for the study of the canopy heterogeneity and its effect. This also benefits modeling for fluxes of carbon, water and energy from the level of the stand to landscape. __________ Translated from Journal of Plant Ecology, 2007, 31(3): 431–436 [译自: 植物生态学报]     

Methodology comparison for slope correction in canopy leaf area index estimation using hemispherical photography

The slope effect and correction methods for estimation of canopy gap fraction, leaf area index (LAI), mean leaf angle and clumping index using hemispherical photography, were investigated. The evaluation was carried out in tropical cloud forest and plantations in South-East Kenya in order to consider a range of canopy architecture and slopes up to 65%. The aim was to compare two acquisition techniques and various correction procedures. All estimates assume uniform slope, canopy parallel to ground and homogeneous canopy structure at the photo site level.

(1) Photographs oriented to local zenith (levelled acquisition). Calculation and removal of sky parts of the hemisphere obstructed by topography. Azimuthal inversion of gap fraction without prior averaging, deriving local LAI estimates (quasi-random model). (i) Fixed path lengths over azimuths. Zenith reference axis. LAI referred to horizontal and corrected for topographic shading. (ii) Variable path lengths over azimuths. Normal to slope reference axis. LAI adjusted to horizontal by dividing by the slope cosine.

(2) Photographs oriented parallel to slope (tilted acquisition). Fixed path lengths over azimuths. Normal to slope reference axis. LAI adjusted to horizontal by dividing by the slope cosine. Azimuthal inversion of gap fraction without prior averaging, deriving local LAI estimates (quasi-random model).

Gap fractions present a stronger upslope/downslope asymmetry if retrieved from levelled acquisition. As a result, gap dispersion index and clumping index proved to be significantly higher for levelled acquisition (P < 0.001). LAI estimates adjusted to horizontal are not significantly different, whether retrieved from levelled or tilted acquisitions, up to 30% slopes. From levelled acquisition, fixed and variable path length do not yield significantly different LAI estimates along the whole slope gradient. From tilted acquisition, LAI values were systematically higher than from levelled acquisitions, the stronger the slope, the higher the difference. Mean leaf angles do not differ significantly (P > 0.05) for fixed vs. variable path lengths along the slope gradient up to 30%. For more severe slopes, variable path lengths yield lower mean leaf angle values. The interpretation of results from tilted acquisition remains uncertain. As a preliminary study, no preference is suggested for the levelled or tilted acquisition technique. Further investigation is needed and indirect optical derived estimates should be checked against direct reference measures, which are almost entirely lacking for mountainous areas.     

Modelling biomass and leaf area index in a sub-arctic Scandinavian mountain area

Estimates of biomass and leaf area index (LAI) are important variables in ecological and climate models. However, very little is known about the biomass and LAI of the vegetation in the Scandinavian mountain area. In this study, extensive field data consisting of diameter at breast height for 13?000 trees and height for 550 trees were collected. Furthermore, biomass and leaf area (LA) measurements for 46 mountain birch trees [Betula pubescens ssp. czerepanovii (Orlowa) Hämet-Ahti] and biomass and LA measurements for shrubs (e.g. Salix spp., Betula nana) at 36 sample plots were carried out. Multiplicative linear models for trees were fitted to tree biomass and LA measurements using basal area at breast height, height, crown diameter and diameter at stump height as explanatory variables. Additive linear models were fitted to shrub biomass and LAI measurements using coverage of shrubs, topographic variables and soil type as explanatory variables. The functions were then used to predict the biomass and LAI for trees and shrubs for the entire test area, which covers an area of 84 km² and is located at latitude 68° N. The mean total biomass estimates were 27?493 kg ha^?1 for the forest and 7650 kg ha^?1 for snow-protected heath and meadow vegetation. The LAIs were 2.06 and 0.52, respectively. For monitoring biomass and LAI in the Scandinavian mountain area, the functions could also be applied to data from traditional field-based inventories and the estimates might further be improved by combining the estimates from the test area with auxiliary information such as remote sensing images.     

园林植物叶面积指数研究进展

本文对园林植物叶面积指数(LAI)研究的进展进行了综述,详细介绍了LAI的定义、LAI的主要测定方法、LAI与枝干的相关关系、LAI的应用现状,并对园林植物叶面积指数的研究前景进行了讨论。     

Validation of an efficient visual method for estimating leaf area index in clonal Eucalyptus plantations

Leaf area index (LAI) is a key ecophysiological parameter in forest stands because it characterises the interface between atmospheric processes and plant physiology. Several indirect methods for estimating LAI have been developed. However, these methods have limitations that can affect the estimates. This study aimed to evaluate the accuracy and applicability of a visual method for estimating LAI in clonal Eucalyptus grandis × E. urophylla plantations and to compare it with hemispherical photography, ceptometer and LAI-2000^® estimates. Destructive sampling for direct determination of the actual LAI was performed in 22 plots at two geographical locations in Brazil. Actual LAI values were then used to develop a field guide with photographic images representing an LAI range of 1.0–5.0 m² m^?2 (leaf area/ground area). The visual LAI estimation guide was evaluated with 17 observers in the field. The average difference between actual LAI and visual LAI estimation was 12% and the absolute difference between the two methods was less than or equal to 0.5 m² m^?2 in 77% of plots. Pearson’s correlation coefficients were high between actual LAI and hemispherical photographs (0.8), visual estimation (0.93) and LAI-2000^® (0.99) and low for the ceptometer (0.18). However, absolute values differed among methods, with the average difference between the actual and estimated LAI of [12]% for visual estimation, 28% for the LAI-2000^®, 37% for the ceptometer and ?43% for hemispherical photographs. The LAI-2000^® and ceptometer overestimated LAI in all plots, whereas hemispherical photographs underestimated the values in all measurements, showing that these methods need calibration to be used. No differences were observed between actual LAI and visual estimates across stand ages of 2–8 years and LAI of 1.5–5.3 m² m^?2 (P > 0.05). The results show that visual estimation of LAI in Eucalyptus stands is a practical method that is unaffected by atmospheric characteristics and can be used on an operational scale.     

Spatial and temporal variations in leaf area index, specific leaf area and leaf nitrogen of two co-occurring savanna tree species

Foliage growth, mass- and area-based leaf nitrogen concentrations (Nm and N a) and specific leaf area (SLA) were surveyed during a complete vegetation cycle for two co-occurring savanna tree species: Crossopteryx febrifuga (Afzel. ex G. Don) Benth. and Cussonia arborea A. Rich. The study was conducted in the natural reserve of Lamto, Ivory Coast, on isolated and clumped trees. Leaf flush occurred before the beginning of the rainy season. Maximum leaf area index (LAI), computed on a projected canopy basis for individual trees, was similar (mean of about 4) for both species. Seasonal courses of the ratio of actual to maximum LAI were similar for individuals of the same species, but differed between species. For C. febrifuga, clumped trees reached their maximum LAI before isolated trees. The LAI of C. arborea trees did not differ between clumped and isolated individuals, but maximum LAI was reached about 2 months later than for C. febrifuga. Leaf fall was associated with decreasing soil water content for C. arborea. For C. febrifuga, leaf fall started before the end of the rainy period and was independent of changes in soil water content. These features lead to a partial niche separation in time for light resource acquisition between the two species. Although Nm, N a and SLA decreased with time, SLA and N a decreased later in the vegetation cycle for C. arborea than for C. febrifuga. For both species, N a decreased and SLA increased with decreasing leaf irradiance within the canopy, although effects of light on leaf characteristics did not differ between isolated and clumped trees. Given relationships between N a and photosynthetic capacities previously reported for these species, our results show that C. arborea exhibits higher photosynthetic capacity than C. febrifuga during most of the vegetation cycle and at all irradiances.     

Use of middle infrared radiation to estimate the leaf area index of a boreal forest

The leaf area index (LAI) of boreal forest can be estimated using reflected radiation recorded by satellite sensors. Measurements of visible and near infrared radiation are commonly used in the normalized difference vegetation index (NDVI) to estimate LAI. However, research, mainly in tropical forest, has demonstrated that LAI is related more closely to radiation of middle infrared wavelengths than of visible wavelengths. This paper derives a vegetation index, VI3, based on radiation from vegetation recorded at near and middle infrared wavelengths. For a boreal forest canopy, the relationship between VI3 and LAI was observed to be much stronger than that between NDVI and LAI. In addition, the LAI estimated using VI3 accounted for about 76% of the variation in field estimates of LAI, compared with about 46% when using the NDVI. We conclude that information provided by middle infrared radiation should be considered when estimating the leaf area index of boreal forest.     

日本栗叶面积与叶片生物量计算方法的初步研究

以6年生日本栗品种＂辽栗10号＂与＂大峰＂为试材,对其叶长、叶宽、单叶面积、单叶干重、冠幅、冠高、单株叶片生物量进行了测定。研究不同品种间叶片长宽比值和比叶面积的差异性,叶片长、叶宽和叶片长宽乘积与单叶面积的相关性以及冠幅、冠高与单株叶片生物量的相关性。结果表明：不同品种间叶片长宽比、比叶面积均无显著差异;对日本栗叶长、叶宽、叶片长宽乘积与单叶面积进行一元回归方程拟合,决定系数与修正决定系数均达极显著水平（P〈0.0001）,其中以叶片长宽乘积与单叶面积的一元二次回归方程回归效果最好,决定系数达0.987 9,修正决定系数达0.987 7;单株叶片生物量与冠幅面积和冠高的二元线性回归关系达极显著水平（P〈0.0001）,决定系数达0.997 2,修正决定系数达0.996 4。在生产上,可以通过测量冠幅面积、冠高计算出单株叶片生物量和叶面积指数,该方法操作简单,具有较高应用价值。     

Decreasing the error in the measurement of the ecosystem effective leaf area index of a Pinus massoniana forest

Decreasing the forest ecosystem leaf-area index error(LAIe)helps accurately estimate the growth and light energy utilization of aboveground foliage.Analyzing light transmission in forest ecosystems can effectively determine LAIe.The LAI-2200 plant canopy analyzer(PCA)is used extensively for rapid field-effective LAI(LAIe)measurements and primarily to measure forest canopy LAIe values.However,sometimes this parameter must also be measured in forests with small clearings.In this study,we used the LAI-2200 PCA to obtain one A-value and four B-values each for the canopy,herbaceous layer,and forest ecosystem LAIe.Field measurements showed that the three LAIe types were obviously different.In certain quadrats,the average herbaceous layer(Dicranopteris dichotoma Bernh.)LAIe apparently exceeded that of the Pinus massoniana forest ecosystem.The sources of this error were measuring and recording A-value readings for small canopies and underestimating the ecosystem LAIe.We obtained similar coefficients of determination for both the pre-recomputation and post-recomputation of the canopy and forest ecosystem LAIe(R^2C 0.96 and R^2C 0.99,respectively);thus,the error was decreased.Measuring field LAIe with the LAI-2200 PCA and recomputation should compensate for LAIe underestimation in complex forest ecosystems.     

Response of LAI-2000 estimates to changes in plant surface area index in a Scots pine stand

We assessed the accuracy with which the LAI-2000 plant canopy analyzer measured changes in leaf area index (LAI) and plant area index (PAI) in a 25-year-old Scots pine (Pinus sylvestris L.) stand. Stand density was 2100 stems ha(-1) and mean tree height was 8.7 m. Needle and branch areas of the stand were reduced progressively to zero by the stepwise removal of branches on all trees growing in a circular plot with a radius of 25 m. An LAI-2000 estimate was taken after each step reduction. The needle and branch surface areas removed at each step were estimated from direct measurements and were compared with the changes in the LAI-2000 estimates. Initially (before removal of branches), directly measured PAI was 5.2 (needles = 86%, branches = 8% and stems = 6%). The LAI-2000 estimate of total surface area was 66% of direct PAI and 77% of direct LAI. There was a nonlinear relationship between the LAI-2000 estimate and directly measured PAI, such that their ratio (equivalent to the clumping factor) increased from 0.66 to 1.05 with decreasing PAI. At the last measurement, when only stems were left, the LAI-2000 estimate agreed well with the direct measurement of PAI. The LAI-2000 underestimated the direct measurement of LAI at the first three steps when LAI was > 2 and the proportion of woody area was small (< 20%). However, because the LAI-2000 estimate included stem and branch areas, it overestimated the direct measurement of LAI at the last three measurements when the proportion of woody area was large (> 20%).     

Landscape pattern and spatial variability of leaf area index in Eastern Amazonia

Uncertainties about the implications of land-cover heterogeneity on the Amazonian carbon (C) and water cycles are, in part, related to the lack of information about spatial patterns of key variables that control these fluxes at the regional scale. Leaf area index (LAI) is one of these key variables, regulating a number of ecosystem processes (e.g. evaporation, transpiration and photosynthesis). In order to generate a sampling strategy for LAI across a section of Amazonia, we generated a landscape unit (LU) map for the Tapajós region, Eastern Amazonia, as a basis for stratification. We identified seven primary forest classes, stratified according to vegetation and/or terrain characteristics, and one secondary forest class, covering 80% of the region. Primary forest units were the most representative, covering 62% of the total area. The LAI measurements were carried out in 13 selected LUs. In each LU, we marked out three 50 m × 50 m plots giving a total number of 39 plots (9.75 ha). A pair of LAI-2000 plant canopy analysers was used to estimate LAI. We recorded a total of 25 LAI measurements within each plot. We used the field data to verify the statistical distribution of LAI samples, analyse the LAI variability within and among sites, and show the influence of sample size on LAI variation and precision. The LAI showed a high coefficient of variation at the plot level (0.25 ha), from 5.2% to 23%, but this was reduced at the landscape unit level (three co-located plots, 1.8–12%). The level of precision was <10% and 15% at the plot and landscape unit level, respectively. The LAI decreased from a dense lowland forest site (5.10) to a secondary forest (3.46) and to a pasture site (1.56). We found evidence for differences in the scale of spatial heterogeneity of closed canopy forest versus open canopy forest and palm forests. Landscape variables could, in part, explain differences in LAI among forest sites, and land use is an important modifier of LAI patterns. The stratified LAI sampling proposed in the present study could cope with three important aspects of C and water fluxes modelling: (1) optimise the information obtained from field measurements, which is an advance for models parameterisation, compared to the usual random sampling; (2) generate information for a subsequent scaling up of point field measurements to surfaces covering the whole region; and (3) build a useful basis for validation of estimations, based on remote sensing data, of LAI in the Tapajós region. The variability of LAI in the Tapajós region showed that this variable is a source of uncertainty for large-scale process modelling.     

The potential for increasing rubber production by matching tapping intensity to leaf area index

Understanding resource capture can help design appropriate species combinations, planting designs and management. Leaf area index (LAI) and its longevity are the most important factors defining dry matter production and thus growth and productivity. The ecophysiological modifications and yield of rubber (Hevea spp.) in an agroforestry system (AFS) with beans (Phaseolus vulgaris L.) were studied. The experiment was established in Southeast-Brazil, with three rubber cultivars: IAN 3087, RRIM 600 and RRIM 527. The AFS comprised double rows of rubber trees along with beans sown in autumn and winter seasons in 1999. There was about 50% higher rubber yield per tree in the AFS than the rubber monoculture. Trees within the AFS responded to higher solar radiation availability with higher LAI and total foliage area, allowing its greater interception. All three cultivars had higher LAI in the AFS than monoculture, reaching maximum values in the AFS between April and May of 3.17 for RRIM 527; 2.83 for RRIM 600 and 2.28 for IAN 3087. The maximum LAI values for monocrop rubber trees were: 2.65, 2.62 and 1.99, respectively, for each cultivar. Rubber production and LAI were positively correlated in both the AFS and monoculture but leaf fall of rubber trees in the AFS was delayed and total phytomass was larger. It is suggested that trees in the AFS were under exploited and could yield more without compromising their life cycle if the tapping system was intensified. This shows how knowledge of LAI can be used to manage tapping intensity in the field, leading to higher rubber yield.     

Estimating leaf area index in different types of mature forest stands in Switzerland: a comparison of methods

Leaf area index (LAI) was estimated at 15 sites in the Swiss Long-Term Forest Ecosystem Research Programme (LWF) in 2004–2005 using two indirect techniques: the LAI-2000 plant canopy analyzer (Licor Inc.) and digital hemispherical photography, applying several exposure settings. Hemispherical photographs of the canopy were analysed using Hemisfer, a software package that offers several new features, which were tested here: (1) automatic thresholding taking the gamma value of the picture into account; (2) implementation of several equations to solve the gap-fraction inversion model from which LAI estimates are derived; (3) correction for ground slope effects, and (4) correction for clumped canopies. In seven broadleaved stands in our sample set, LAI was also estimated semi-directly from litterfall. The various equations used to solve the gap-fraction inversion model generated significantly different estimates for the LAI-2000 measurements. In contrast, the same equations applied in Hemisfer did not produce significantly different estimates. The best relationship between the LAI-2000 and the Hemisfer estimates was obtained when the hemispherical photographs were overexposed by one to two stops compared with the exposure setting derived from the reading of a spotmeter in a canopy gap. There was no clear general relationship between the litterfall and the LAI-2000 or the hemispherical photographs estimates. This was probably due to the heterogeneity of the canopy, or to biased litterfall collection at sites on steep slopes or sites subject to strong winds. This study introduces new arguments into the comparison of the advantages and drawbacks of the LAI-2000 and hemispherical photography in terms of applicability and accuracy.     

人工红松幼龄林的叶面积指数与生长动态

对凉山自然保护区的全坡位红松（Ｐｉｎｕｓ ｋｏｒａｉｅｎｓｉｓ）造林地进行了生长与叶面积指数的动态调查表明，立地条件好的地段红松生长好，上层阔叶树发育亦好。立地条件和上层阔叶树的庇护是导致红松生长差异的主要原因。     

Shoot structure, leaf area index and productivity of evergreen conifer stands

For 12 conifer species, the maximum ratio of shoot to leaf silhouette area of shade-acclimated shoots was found to vary from 0.50 to 0.99. Maximum leaf area index (leaf area per unit ground area) of conifer stands varied from 3.5 to 20, and maximum mean annual increment varied by a factor of 2. Significant correlations were found between leaf silhouette area ratio of shade-acclimated shoots and the maximum leaf area index (R(2) = 0.84) and the maximum mean annual increment (R(2) = 0.93). These results support a hypothesis that species to species differences in the morphology of shade-adapted shoots strongly affect both the development of leaf area and the productivity of stands of evergreen conifers.     

Estimating leaf area index of mature temperate forests using regressions on site and vegetation data

Canopy gap fraction and leaf area index (LAI) were measured using hemispherical photography in 91 mature forests across Switzerland, including coniferous, broadleaved and mixed stands. The gap fraction and LAI derived from five photographs per site could be reproduced with a high coefficient of determination (R² > 0.7) by regression against simple stand parameters obtained from vegetation surveys: coverages of the tree, shrub and herb layers, and tree height. The method appeared to be robust across the different types of forests. Applied to 981 sites across Switzerland, the regression model produced LAI values ranging from 1.4 to 6.7. These predictions were compared with site variables not included in the regression. LAI appeared limited by the altitude, with maximal values decreasing by one third from 400 to 2000 m above see level. Water availability was also clearly a limitation at sites with a negative water balance, i.e. where the yearly potential evapotranspiration exceeded the precipitation. High or low values of a humidity index based on the ground vegetation also corresponded to a limitation of the LAI, with shorter trees at dry sites and more open canopies at wet sites. Compared to optical measurements (including hemispherical photography), our regression method is fast and inexpensive. Such an approach appears very promising for obtaining reliable estimates of LAI for many sites with low costs. These estimates can then be fed into process models at the stand level.     

Age-related effects on leaf area/sapwood area relationships,canopy transpiration and carbon gain of Norway spruce stands (Picea abies) in the Fichtelgebirge,Germany

Stand age is an important structural determinant of canopy transpiration (E(c)) and carbon gain. Another more functional parameter of forest structure is the leaf area/sapwood area relationship, A(L)/A(S), which changes with site conditions and has been used to estimate leaf area index of forest canopies. The interpretation of age-related changes in A(L)/A(S) and the question of how A(L)/A(S) is related to forest functions are of current interest because they may help to explain forest canopy fluxes and growth. We conducted studies in mature stands of Picea abies (L.) Karst. varying in age from 40 to 140 years, in tree density from 1680 to 320 trees ha(-1), and in tree height from 15 to 30 m. Structural parameters were measured by biomass harvests of individual trees and stand biometry. We estimated E(c) from scaled-up xylem sap flux of trees, and canopy-level fluxes were predicted by a three-dimensional microclimate and gas exchange model (STANDFLUX). In contrast to pine species, A(L)/A(S) of P. abies increased with stand age from 0.26 to 0.48 m(2) cm(-2). Agreement between E(c) derived from scaled-up sap flux and modeled canopy transpiration was obtained with the same parameterization of needle physiology independent of stand age. Reduced light interception per leaf area and, as a consequence, reductions in net canopy photosynthesis (A(c)), canopy conductance (g(c)) and E(c) were predicted by the model in the older stands. Seasonal water-use efficiency (WUE = A(c)/E(c)), derived from scaled-up sap flux and stem growth as well as from model simulation, declined with increasing A(L)/A(S) and stand age. Based on the different behavior of age-related A(L)/A(S) in Norway spruce stands compared with other tree species, we conclude that WUE rather than A(L)/A(S) could represent a common age-related property of all species. We also conclude that, in addition to hydraulic limitations reducing carbon gain in old stands, a functional change in A(L)/A(S) that is related to reduced light interception per leaf area provides another potential explanation for reduced carbon gain in old stands of P. abies, even when hydraulic constraints increase in response to changes in canopy architecture and aging.     

Estimation of leaf area index from high resolution ZY-3 satellite imagery in a catchment dominated by Larix principis-rupprechtii,northern China

Leaf area index(LAI) is a key factor that determines a forest ecosystem's net primary production and energy exchange between the atmosphere and land surfaces.LAI can be measured in many ways, but there has been little research to compare LAI estimated by different methods. In this study, we compared the LAI results from two different approaches, i.e., the dimidiate pixel model(DPM) and an empirical statistic model(ESM) using ZY-3 high-accuracy satellite images validated by field data. We explored the relationship of LAI of Larix principis-rupprechtii Mayr plantations with topographic conditions. The results show that DPM improves the simulation of LAI(r = 0.86,RMSE = 0.57) compared with ESM(r = 0.62, RMSE =0.79). We further concluded that elevation and slope significantly affect the distribution of LAI. The maximum peak of LAI appeared at an aspect of east and southeast at an elevation of 1700–2000 m. Our results suggest that ZY-3 can satisfy the needs of quantitative monitoring of leaf area indices in small-scale catchment areas. DPM provides a simple and accurate method to obtain forest vegetation parameters in the case of non-ground measurement points.     

Temporal variation and efficiency of leaf area index in young mountain Norway spruce stand

Temporal variation of leaf area index (LAI) in two young Norway spruce stands with different densities was monitored during eight consecutive growing seasons (1998–2005). We focused on: (1) LAI dynamics and above-ground mass production of both spruce stands and their comparison, (2) leaf area duration (LADU), crop production index (CPI) and leaf area efficiency (LAE) evaluation, and (3) thinning impact on the above-mentioned parameters. Also, we tried to deduce the most effective LAI value for the Norway spruce forest investigated. The LAI values of both spruce stands showed a typical seasonal course. To describe the LAI dynamics of the stand, we recommend taking LAI measurements within short time intervals at the time of budding and needle expansion growth (i.e., in early spring) and close to the LAI peak, when the twig growth has been completed. The reason was that after reaching the seasonal maximum, no significant differences between subsequently obtained values were found in the following 2 months. Therefore, we recommend this period for the estimation of seasonally representative LAI values, enabling the comparison of various spruce stands. The maximum hemi-surface LAI value reached 12.4. Based on our results, the most effective LAI values for maximum above-ground biomass production were within the range of 10–11. We found an LAI over these values to be less effective for additional production of above-ground biomass. In forest practice, thinning intensity is mostly described by percentage of stocking reduction. We want to show that not only thinning intensity, but also the type of thinning is important information. The type of thinning significantly affected the stand above-ground biomass increment, canopy openness, stand LAI and LAI efficiency. The stimulating effect of high-type thinning was observed; the LAE as well as the CPI increased. Low-type thinning had no such effects on LAE increments compared to the high-type thinning with similar intensity.

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