Site Quality Variables Research Articles

Long-term growth data of plantation-grown Eucalyptus established in south-eastern Uruguay

Behind beef production, Eucalyptus logs oriented to kraft pulp production represent Uruguay's second-largest export product. In this context, the analysis of long-term growth data of plantation-grown Eucalyptus forests acquires a material relevance. A total of 2208 permanent plots representing longitudinal growth data of Eucalyptus globulus, Eucalyptus maidenii, Eucalyptus dunnii, and Eucalyptus smithii trees were analyzed and modeled. The plots are part of a more extensive set established since 2012 on a forest state of over 22,000 ha planted. The selected plots were of variable shape, varying in size between 200 and 1000 m2. Both planted and coppiced areas were included. Tree-level data (diameter at the beast height and height) was measured on each plot over a different number of years. Plantation ages, at the time of measurement, ranged from 1 to 18 years. The forests were all planted for the first time under the context of degraded grasslands, where there was no other better alternative use for the land. Soils are not very deep, of medium-to-coarse texture, and have low natural fertility. The dominant land cover was grasslands. The results highlight the variability in site quality. Stand density varied between 100 and 2500 trees per ha (TPH), with a site index (SI) at base age 11 ranging between 12 and 38 m. A strong relationship between dominant height (DH) and standing volume (TV) is evident, reinforcing that SI is still a valuable quantity to represent site quality. A set of anamorphic SI curves fitted to the DH data showed that E. dunnii and E. smithii height far exceeds that of E. globulus and E. maidenii at the same age, with an average SI of 28 and 31 m, respectively. Similarly, a family of TV curves fitted to each species as a function of DH, TPH, basal area, and age showed that the implicit current annual growth (CAI), given the model form used, peaked between 7 and 9 years. Depending on the stocking and site index considered, the CAI varied; but, in all cases, the CAI of E. dunnii was the highest, followed by E. smithii, and then E. maidenii and E. globulus in descending order. As an example, for a fixed density of 1100 TPH, the peak CAI was almost 48.6 m3|ha|yr for E. dunnii (SI28), approximately 42.1 m3|ha|y for E. smithii (SI31), and 17.8-21.3 m3|ha|yr for E. maidenii and E. globulus (SI23).

The Influence of Site Quality and Trust on Repurchase Interest of Tokopedia through Perceived Usefulness

Purpose: this study aims to examine the relationship between site quality variables and trust in Tokopedia consumer repurchase interest in Surabaya through the mediating variable of perceived usefulness.
 Design/methodology/approach: This is a quantitative study and the data will be analysed through partial Least Square (PLS).
 Findings: 5 out of 7 hypotheses cannot be proved and supported by this study
 Research limitations/implications: The respondent of this study are 95 Tokopedia user.
 Practical implications: Only 2 out of 7 hypotheses can be proved and supported.
 Paper type: This study is categorised as a case study.

Imprints of management history on hemiboreal forest ecosystems in the Baltic States

AbstractIn the Baltic States region, anthropogenic disturbances at different temporal and spatial scales mostly determine dynamics and development phases of forest ecosystems. We reviewed the state and condition of hemiboreal forests of the Baltic States region and analyzed species composition of recently established and permanent forest (PF). Agricultural deforestation and spontaneous or artificial conversion back to forest is a scenario leading to ecosystems designated as recent forest (RF, age up to two hundred years). Permanent forest (PF) was defined as areas with no records of agricultural activity during the last 200 yr, including mostly forests managed by traditional even‐aged (clear‐cut) silviculture and salvage after natural disturbances. We hypothesized that RF would have distinctive composition, with higher dominance by hardwoods (e.g., aspen and birch), compared to PF. Ordination revealed divergence in the RF stands; about half had the hypothesized composition distinct from PF, with a tight cluster of stands in the part of the ordination space with high hardwood dominance, while the remaining RF stands were scattered throughout the ordination space occupied by PF with highly variable species composition. Planting of conifers, variability in site quality, and variability in spatial proximity to PF with relatively natural ecosystem legacies likely explained the variable compositions of this latter group of RF. We positioned the observations of RF in a classic quantification of site type conditions (based on Estonian forest vegetation survey previously carried out by Lõhmus), which indicated that RF was more likely to occur on areas of higher soil fertility (in ordination space). Climatic and anthropogenic changes to RF create complex dynamic trends that are difficult to project into the future. Further research in tracing land use changes (using pollen analysis and documented evidence) should be utilized to refine the conceptual framework of ecosystem legacy and memory. Occurrence and frequency of deforestation and its characteristics as a novel disturbance regime are of particular interest.

Tree diameter performance in relation to site quality in smallholder timber production systems in Gunungkidul, Indonesia

Smallholder farmers’ choices of tree species in the Gunungkidul region have been limited by lack of management information. This paper describes activities to help inform farmers’ choices of three common timber species—Tectona grandis, Swietenia macrophylla and Acacia auriculiformis—in agroforestry systems in the region through (1) developing models predicting tree diameter growth based on reference growth function and the growth retardation performance and (2) estimating the contributions of site quality variables to the diameter growth retardation of ≤5 and >5-year-old stands. A total of 48 farms were selected, representing three slope ranges and two soil types, with a circular sample plot of 10 m radius established at each farm. A Quadratic model for each timber species indicated that the age of the tree explains a high percentage of the variance in diameter growth. Diameter growth varies with tree age and responds differently in each soil type and slope position. A set of site quality variables were able to predict retarded diameter performances of each tree species in two group ages and two soil types. These results suggest that the models can inform farmers’ choices of tree species and management.

Tree height prediction approaches for uneven-aged beech forests in northwestern Spain

Artificial neural network methods appear to be a reliable alternative to traditional methods of tree height prediction in even-aged stands. However, this has not been demonstrated for uneven-aged forests. Two back-propagation artificial neural networks were constructed, and their performance in estimating the height of pure uneven-aged stands of common beech (Fagus sylvatica L.) in northwestern Spain was compared with that of the models most commonly used to estimate tree height (nonlinear calibrated local and generalized mixed-effects models and generalized fixed-effects models). All approaches produced accurate results, reducing the root mean squared error by more than 22% relative to basic nonlinear regression. Nonetheless, considering practical use of the models, the traditional approaches require measurement of several trees for calculation of stand-specific variables (generalized models) and for model calibration (mixed-effects models). Back-propagation artificial neural networks require less sampling effort because no height measurements are required for their implementation. However, this technique was not the best height predictor, because of the high degree of variability in site quality between stands. In this case, the local mixed-effects models yielded the best results and provided the best balance between the accuracy of the model and sampling effort.

Estimating the age–diameter relationship of oak species in Switzerland using nonlinear mixed-effects models

Tree growth plays a key role in forest dynamics, yet little attention has been paid to quantifying tree age–diameter relationships. Predicting diameter growth of oaks is especially important due to their role in nature conservation and adaptive forest management under climate change. Thus, we (1) identified environmental variables that shape age–diameter relationships of oaks and (2) quantified the accuracy of predictions based on these variables. We determined the age–diameter relationship of 243 oaks (Quercus spp.) growing in Switzerland by using tree-ring samples. Nonlinear mixed-effects models based on a modified Chapman-Richards equation were fitted with environmental variables included as covariates. The fixed effects elevation, slope and water-holding capacity were most important in shaping the age–diameter relationships. Lower elevations, steeper slopes, north-facing aspects, higher water-holding capacities and moister summers resulted in larger maximum diameters. For 75 % of the oaks, age–diameter relationships predicted by the fixed effects matched fairly well the observations (root mean square error between predictions and observations <6 cm); the inclusion of random effects reduced root mean square errors for 86 % of the trees. These results suggest that water runoff plays a key role for the age–diameter relationships, accompanied by limiting temperature effects at higher elevations. The fixed effects covered variability in site quality, whereas the random effects included tree-specific deviations from expected age–diameter relationships, potentially due to neighbourhood effects such as stand density and competition.

Site index for teak in Colombia

Determination of site quality is a basic tool for proper selection of locations and species, in management of forest plantations. Throughout the Caribbean studies of site quality are few and are hampered by statistical limitations, inappropriate growth models, and limited data. We fitted growth curves for dominant height to evaluate and classify site quality of teak (Tectona grandis) plantations by using data from 44 permanent sample plots established since 1990 in 3–22 years old teak plantations in the Colombian Caribbean region. We used Korf’s and von Bertalanffy’s models to fit curves as non-linear effects models. Both models, with a single random parameter, were considered as adequate for dominant height growth modelling, but Korf’s model was superior. The resulting curves were anamorphic and closely reflected high variability in site quality. Five site classes were clarified: at a base age of 12 years old, teak reached a mean dominant height of 24.8 m on the best sites, 9.8 m in the worst sites, and in the averages sites, 15.8–18.8 m. Using this model, we identified the best and the worst sites for teak plantations in the Caribbean region. This model proved a useful tool, not only for site quality evaluation, but also for improved teak plantation planning and management.

Leaf area index development in temperate oak and beech forests is driven by stand characteristics and weather conditions

Using data from 20 even-aged and homogeneous mature beech and oak study plots in Flanders (Northern Belgium), an analysis of the empirical relationships between the rates of leaf area index (LAI) change throughout the leaf development of 2008 and stand, site and meteorological variables was performed. Species-specific multiple linear regressions were fitted between the rates of LAI change and the predictors for two distinct periods from April until August. After a sharp increase in LAI following budburst, the seasonal LAI development for both species showed a marked period of stationary LAI development over all study plots. The cause for the cessation of LAI growth was assumed to be the decline of air temperature and radiation during this period. Later on, the rate of LAI development restarted similarly in every plot. The influence of weather on LAI development was high and its effects were different between species, with beech mostly affected by radiation and oak negatively related to minimal and maximal values of air temperature. Furthermore, our analysis suggested that stand structural (tree density and stand basal area for both species) and tree growth characteristics (average tree-ring width ratio for oak) variables were major drivers of the LAI development during early spring. Later during the growth period, stand variables became less predominant in affecting LAI development. Site quality variables affected LAI development to a lesser extent. The seasonal LAI development was found very similar among stands. This study adds a more accurate and comprehensive approach to the modelling of LAI development during leaf growth of two important European temperate deciduous forest species.

Site index of Sitka spruce (Picea sitchensis) in relation to different measures of site quality in Ireland

To examine the relationships between Sitka spruce (Picea sitchensis (Bong.) Carr.) site index and site quality variables, we sampled 201 Sitka spruce stands covering the entire range of sites supporting the growth of the species in Ireland. Site index varied significantly with climate and climate surrogate variables, some site quality variables, soil physical and chemical properties, edatopes (combinations of soil nutrient and moisture regimes), rotation types, provenance, and fertilizer regimes. We developed a series of models to predict site index using climate, site, soil physical and chemical properties, edaphic variables, and management factors as predictor variables. Soil nutrient regime (SNR) exhibited the strongest relationship of all variables examined in the study, explaining 51% of the variation in site index, with site index increasing with increasing SNR. We found that edaphic variables of soil moisture regime and SNR produced the best prediction of site index. The species showed the best development on fresh to very moist sites, with rich to very rich soil nutrient regimes. We also developed a composite model explaining 62% of the variation in site index and an elevation zone model (&gt;300 m) explaining 74% of the variation in site index.

Estimating Demand for Urban Fisheries Management: an Illustration of Conjoint Analysis as a Tool for Fisheries Managers

AbstractThis paper illustrates the use of discrete‐choice analysis, a nonmarket valuation technique, for assessing the effect of different management or fishing site quality variables on demand for urban fisheries. The study was carried out in three fishing ponds that are a part of the Close‐to‐Home Fishing Program in the Oklahoma City metropolitan area. We found that, on average, anglers were willing to pay more for physical infrastructure improvements, such as flush toilets ($3.81/year) and docks ($1.28/year), than for having larger channel catfish Ictalurus punctatus stocked (.23/year for a 4‐in increase). Willingness to pay for improvements to the ponds was less for minority anglers than for other anglers. Having relative values for potential management changes for a fishery helps to inform fisheries managers about what characteristics are valued most by anglers, allowing managers to better serve the anglers' interest and to justify the costs of implementing these changes.

Monitoring secondary tropical forests using space-borne data: Implications for Central America

Tropical secondary forests, which play an important role in carbon sequestration, may be monitored using space-borne sensors. Secondary forest biomass or age estimation from space-borne data may be used to quantify the carbon sink these forests represent. At current capabilities, roughly three successional stages up to 15 years of age may be identified from Landsat TM data. Using synthetic aperture radar, reliable biomass estimates may be made up to approximately 60 tons/ha. The potential for overcoming these limitations is reviewed, including the synergy of radar and optical imagery and the unprecedented spatial and spectral resolutions of new sensors. Most of the available literature to date is from the Amazon; in this paper, applicability to Central America is considered, which has a much more heterogeneous landscape and the dynamics of secondary growth have a special significance in the framework of conservation biology and carbon sequestration. We conclude that critical issues in this region will be topographical correction and stratification according to ecological and site quality variables.

Impact of habitat quality on forest plant species colonization

The impact of habitat quality and site history on the recolonization potential of ancient-forest plant species on abandoned farmland was studied in the forest of Ename, Flanders, Belgium. With the exception of a network of fringe relics (linear elements mainly along exploitation roads), our study area was cleared and converted to arable land ca. 1850. From 1869 onward, most fields were gradually abandoned, resulting in a progressive, partly spontaneous reforestation. Each of the 42 actual forest parcels (amounting to 62 ha) was surveyed and a total of 466 plant species were inventoried. Twenty seven of these were identified as ancient-forest plant species and cataloged in a separate subset. Additionally, the spatial distribution of six ancient-forest plant species ( Anemone nemorosa, Corylus avellana, Hyacinthoides non-scripta, Paris quadrifolia, Mercurialis perennis, Vinca minor) was systematically surveyed and digitized in a GIS environment. Habitat quality was assessed on the parcel level using intrinsic soil variables on the one side, and historically related variables (length of the agricultural-occupation period, length of woody fringe relics, and total length of fringe relics s.l.) on the other. Soil texture had a major impact on the duration of agricultural land use after deforestation. Soil phosphate content and pH are positively correlated with the duration of the agricultural land use. The number of ancient-forest plant species was negatively affected by the length of the agricultural-occupation period and soil phosphate content, and positively by the total length of the surrounding fringe relics. The same trends are observed studying the systematically surveyed ancient-forest species. We propose that soil phosphate content affected ancient-forest plant species distribution, because it stimulates vigorous vegetation development and as such has a definite effect on evolving competitive plant relationships. Using raster-G.I.S analysis tools, mean and maximum colonization distances and approximate mean and maximum colonization rates per century were calculated for each systematically surveyed species. We conclude that not only seed dispersal capabilities, but also site quality variables play an important role in the colonization process of ancient-forest plant species. In the short term, afforestation of previously heavily fertilized farmland will not result in floristically diverse and, thus, valuable forest habitats. The relatively immobile soil phosphate represents a major barrier.

Predicting the relative sensitivity of forest production in Ireland to site quality and climate change

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 10:51-67 (1998) - doi:10.3354/cr010051 Predicting the relative sensitivity of forest production in Ireland to site quality and climate change Christine L. Goodale1,*, John D. Aber1, Edward P. Farrell2 1Complex Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824, USA2Department of Environmental Resource Management, University College Dublin, Agriculture Building Belfield, Dublin 4, Ireland *E-mail: christy.goodale@unh.edu Most model-based predictions of climate change effects on forest ecosystems have used either potential or static descriptions of vegetation and site, removing the effects of direct management or land use. In this paper we use a previously developed and validated model of carbon and water balances in forest ecosystems (PnET-II) to assess the relative sensitivity of forest production in Ireland to predicted climate change and to ambient variability in site quality. After validating the model against measured productivity for 2 sets of stands, we ran the model using existing variation in site quality, represented as differences in foliar N concentration, and also for predicted changes in climate and atmospheric CO2. Resulting variations in productivity were compared with those due to potential errors in the specification of input parameters and to variation in current ambient climate across the region. The effects on net primary production (NPP) and wood production of either ambient variation in climate or predicted changes in temperature, precipitation and CO2 are quite small (0 to 30%) relative to the effects of ambient variability in site quality (up to 400%). The range of possible variation in other user-specified physiological parameters resulted in changes of less than 10% in model predictions. We conclude that site-specific conditions and management practices result in a range of forest productivity that is much greater than any likely to be induced by climate change or CO2 enrichment. We also suggest that it is essential to understand and map spatial variability in site quality, as well as to understand how the productive capacity of landscapes will change in response to management and pollution loading, if we are to predict the actual role that climate change will play in altering forest productivity and global biogeochemistry. Regional modeling · Validation · Foliar nitrogen · Sitka spruce Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 10, No. 1. Online publication date: April 09, 1998 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1998 Inter-Research.

Dominant-height and site-index equations for ponderosa pine in east-central Arizona

A dominant-height equation for ponderosa pine (Pinusponderosa Laws.) was constructed utilizing a parameter prediction method and a model by J.E. King. The site-index equation was obtained by inverting the dominant-height equation. A method was examined for indirectly obtaining parameter prediction equations. It proved superior to two direct parameter prediction approaches. Other site-quality variables, such as habitat type groups and elevation, were included in the dominant-height and site-index equations and were successful in refining predictive capability.

Neighbour manipulations in natural vegetation a review

Abstract. This paper reviews the literature on neighbour manipulation experiments on species intemctions in natural of semi‐natural vegetation. Three major approaches have been used: 1) introductions into vegetation, 2) trenching, and 3) vegetation removals. Some studies have used a combination of approaches, especially 1) and 3). The removal approach has been used most commonly and is given the greatest emphasis in this paper accordingly.Details of over 50 such studies are summarized here, 48 of which have appeared within only the last two decades. We compare and contrast the experimental designs of these studies and examine their contributions to the understanding of species interactions in vegetation. Evidence for competition is virtually universal among these studies. Several studies have also detected evidence of beneficence between plant species. Numerous factors may confound interpretations in removal experiments including: life stage dependent species responses, species‐dependent timing and speed of response, inadequacy of controls due to temporal and/or spatial variability in site quality, indirect effects of treatment on soil moisture content or nutrient levels, or on the activities of predators or decomposers, and several constraints inherent in particular experimental designs. Another level of complexity arises as a consequence of several variables related to plant attributes that directly determine the nature of interactions between neighbours (e.g. relative competitive abilities, the magnitude of beneficial interactions, the extent to which neighbours make demands on the same resource units). These may interact in a complex manner to affect the response of a ‘target’ plant to the removal of neighbours. Recommendations for future studies are considered and a neighbourhood experimental design is proposed which enables analysis of the extent to which the fates of naturally established individuals following vegetation removal can be accounted for (in multiple regressions) by several variables that reflect different properties and circumstances of interaction with immediate Thiessen neighbours in the field.

Key problems in the management of sports fisheries

Abstract This article discusses issues associated with valuation of sports fishing activities for marine resource management. Since management decisions have effects on marine resource quality and activity levels of different groups of resource users, careful benefit‐cost evaluation of alternative management plans is essential to implement an efficient management system. Three important issues for measuring sports fishing benefits are discussed: (1) aspects of fishing experience enjoyed by recreationists, (2) congestion, and (3) recreational inputs purchased for fishing participation. The household production function framework is discussed as a plausible approach to incorporate a variety of recreational inputs for describing sports fishing demand. Throughout the article, data deficiency is emphasized. Individual microlevel data about recreationists’ socioeconomic characteristics and expenditures as well as fishing site quality variables are necessary to improve the sports fishing valuation task.