Relative stocking index: a proposed index of site quality

1994 ◽  
Vol 24 (7) ◽  
pp. 1330-1336 ◽  
Author(s):  
William E. Berguson ◽  
David F. Grigal ◽  
Peter C. Bates
Keyword(s):  
Surface Soil ◽  
Stand Density ◽  
Site Index ◽  
Site Quality ◽  
Site Factors ◽  
Forest Inventory And Analysis ◽  
Alternative Index ◽  
Lake States ◽  
Annual Water ◽  
Using Data

Site index is difficult to implement and interpret in multispecies, multiple-aged stands, and its relationship to site factors is obscure. Using data from the USDA forest inventory and analysis (FIA) for the Lake States, we developed log-log relationships between mean tree size and stand density for five cover types. Fits were good, with r2 from 0.96 to 0.98 and slopes from −0.948 to −0.995. We define an alternative index of site quality, the relative stocking index (RSI), as the ratio of a stand's measured density to that predicted using the log–log relationship for its cover type (the norm). We divided the range of RSI into three classes for each type (<0.9 of norm, >0.91 but <1.1 of norm, and >1.1 of norm). Based on analyses of the 1977 and 1990 FIA data from Minnesota, class assignments for individual stands remained constant over that 13-year period. Relationships between site factors and either RSI classes or analogous classes based on site index were examined in a subset of 169 stands. Temperature, precipitation, silt content of surface soil, and calculated annual water deficit all differed significantly among RSI classes, but not among site-index classes. The RSI is easy to apply, robust (resistant to change), and related to site factors. It merits additional examination as an index of site quality, especially in heterogenous stands.

scholarly journals A Novel Approach to Modelling Stand-Level Growth of an Even-Aged Forest Using a Volume Productivity Index with Application to New Zealand-Grown Coast Redwood

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1155 ◽  
Author(s):  
Mark O. Kimberley ◽  
Michael S. Watt
Keyword(s):  
New Zealand ◽  
Growth Model ◽  
Growth Models ◽  
Stand Density ◽  
Site Index ◽  
Growth And Yield ◽  
Productivity Index ◽  
Site Quality ◽  
Spatial And Temporal Variation ◽  
Coast Redwood

Empirical growth models are widely used to predict the growth and yield of plantation tree species, and the precise estimation of site quality is an important component of these models. The most commonly used proxy for site quality in growth models is Site Index (SI), which describes the mean height of dominant trees at a specified base age. Although SI is widely used, considerable research shows significant site-dependent variation in height for a given volume, with this latter variable more closely reflecting actual site productivity. Using a national dataset, this study develops and describes a stand-level growth and yield model for even-aged New Zealand-grown coast redwood (Sequoia sempervirens). We used a novel modelling approach that quantifies site quality using SI and a volume-based index termed the 300 Index, defined as the volume mean annual increment at age 30 years for a reference regime of 300 stems ha−1. The growth model includes a number of interrelated components. Mean top height is modelled from age and SI using a polymorphic Korf function. A modified anamorphic Korf function is used to describe tree quadratic mean diameter (Dq) as a function of age, stand density, SI and a diameter site index. As the Dq model includes stand density in its formulation, it can predict tree growth for different stand densities and thinning regimes. The mortality model is based on a simple attritional equation improved through incorporation of the Reineke stand density index to account for competition-induced mortality. Using these components, the model precisely estimates stand-level volume. The developed model will be of considerable value to growers for yield projection and regime evaluation. By more robustly describing the site effect, the growth model provides researchers with an improved framework for quantifying and understanding the causes of spatial and temporal variation in plantation productivity.

Yields of Southwestern Pinyon-Juniper Woodlands

1988 ◽  
Vol 3 (3) ◽  
pp. 70-74 ◽  
Author(s):  
Frederick W. Smith ◽  
Thomas Schuler
Keyword(s):  
Maximum Yield ◽  
Stand Density ◽  
Site Index ◽  
Average Density ◽  
Pinus Edulis ◽  
Site Quality ◽  
Mixed Species ◽  
Growing Stock ◽  
Highly Correlated ◽  
Utah Juniper

Abstract Site quality and growth-growing stock relations were developed for southwestern woodlands of pinyon (Pinus edulis) and one-seed juniper (Juniperus monosperma) or Utah juniper (J. osteosperma). Anamorphic height-age site index curves for pinyon were developed from a regional sample of 60 woodlands. Site index was unaffected by variation in stocking and was correlated with woodland yield when used in conjunction with density. Pinyon and juniper PAI, when taken separately, were highly correlated with stand density and pinyon site index. Pinyon was twice as productive as juniper at similar stand densities. Pinyon and juniper yields in woodlands of average density and site index were estimated at 0.29 and 0.15 m3ha-1y-1. At high densities pinyon and juniper yields increased to 0.61 and 0.31 m3ha-1y-1 Pinyon and juniper yields appeared independent of the density of the other species in an individual woodland. Maximum yield of dense mixed species woodlands on average sites was 0.78 m3ha-1y-1, and occurred when pinyon constituted 65% of woodland density. West. J. Appl. For. 3(3):70-74, July 1988.

Growth Reductions in Naturally Regenerated Southern Pine Stands in Alabama and Georgia

1991 ◽  
Vol 15 (2) ◽  
pp. 73-79 ◽  
Author(s):  
G. A. Ruark ◽  
C. E. Thomas ◽  
W. A. Bechtold ◽  
D. M. May
Keyword(s):  
Pinus Taeda ◽  
Growth Rates ◽  
Stand Structure ◽  
Basal Area ◽  
Stand Density ◽  
Site Quality ◽  
Usda Forest Service ◽  
Forest Inventory And Analysis ◽  
Pine Stands ◽  
Growth Differences

Abstract Data from Forest Inventory and Analysis (FIA) units of the USDA Forest Service were used to compare average annual stand-level basal area accretion onto survivor pines in naturally regenerated pine stands throughout Alabama and Georgia. Growth rates measured between 1972-82 were compared to growth rates during the previous 10-year survey cycle in each state. Separate analyses were conducted for loblolly (Pinus taeda), longleaf (P. palustris), shortleaf (P. echinata), and slash (P. elliottii) pine cover types. The unadjusted average stand-level growth rates for survivor pines 1.0 in. diameter and greater at breast height were notably lower for all cover types during the latter survey in Georgia, while only the average unadjusted growth of shortleaf was substantially lower during this period in Alabama. However, when growth rates were adjusted with regression models to account for differences in initial stand structure (stand size class, stand density, site quality class, hardwood competition, and mortality) between the two survey periods, reductions in average adjusted basal area growth ranged from 3% to 31% during the later cycle in both states. The reductions were statistically significant in almost every case. The agents causing the growth differences were not identified, but it is unlikely that stand dynamics are responsible. The observational nature of the FIA dataset precludes further resolution of causal relationships. South. J. Appl. For. 15(2):73-79.

Population density influences assessment and application of site index

2000 ◽  
Vol 30 (9) ◽  
pp. 1472-1475 ◽  
Author(s):  
David W MacFarlane ◽  
Edwin J Green ◽  
Harold E Burkhart
Keyword(s):  
Loblolly Pine ◽  
Geographic Location ◽  
Stand Density ◽  
Tree Height ◽  
Significant Negative Correlation ◽  
Site Index ◽  
Height Growth ◽  
Planting Density ◽  
Site Quality ◽  
Pinus Taeda L

The height growth of dominant trees in plantations is often assumed to be independent of initial planting density. This assumption allows for the use of dominant tree height as an index of site quality. We found that this assumption was false for the seven tallest trees in 184 even-aged loblolly pine (Pinus taeda L.) stands, planted at nine initial planting densities, at four different geographic locations. A strong, highly significant negative correlation was found between dominant height and initial planting density for stands 14 and 16 years of age. This leads to large differences in predicted site index for stands with different initial planting densities planted at the same geographic location. Use of these site indices to predict yield produced large differences in predicted yield (m3/ha) at age 25. These results provide strong evidence for density-dependent height growth, even for dominant trees in the stand, and suggest that site index, used as a measurement of site quality, is confounded with stand density.

Reevaluating the self-thinning boundary line for ponderosa pine (Pinus ponderosa) forests

2013 ◽  
Vol 43 (10) ◽  
pp. 963-971 ◽  
Author(s):  
Jianwei Zhang ◽  
William W. Oliver ◽  
Robert F. Powers
Keyword(s):  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Stochastic Frontier ◽  
Site Occupancy ◽  
Stand Density ◽  
Site Index ◽  
The Self ◽  
Site Quality ◽  
Boundary Line ◽  
The Face

The self-thinning rule has been used extensively to predict population dynamics under intraspecific and interspecific competition. In forestry, it is an important silvicultural concept for maintaining stand health in the face of climate change and biotic stress, but uncertainty exists because traditional self-thinning limits were set subjectively without regard to site quality. We addressed this by analyzing ponderosa pine (Pinus ponderosa Lawson & C. Lawson) data from 109 research plots measured repeatedly and 59 inventory plots measured once across California. Self-thinning boundaries were fitted to the data with quantile regression and stochastic frontier function (SFF) techniques with and without site index (SI) as a covariate. The models from both methods fitted the data well with either research plots or all plots. Slopes for size-density trajectories were –0.45 with the 0.99 quantile and –0.47 for SFF. Maximum stand density indices (SDI) were 1250 trees per hectare (TPH) with the 0.99 quantile and 1050–1060 TPH with SFF. Mortality occurred when site occupancy from SFF reached 0.75, suggesting a zone of imminent mortality. Curvilinear trends in maximum SDI across SI for both methods indicate that self-thinning varies with site quality. Any management regimes that increase site quality and productivity will increase the self-thinning boundary.

Modeling self-thinning of unthinned Lake States red pine stands using nonlinear simultaneous differential equations

2000 ◽  
Vol 30 (9) ◽  
pp. 1410-1418 ◽  
Author(s):  
Eric C Turnblom ◽  
Thomas E Burk
Keyword(s):  
Differential Equations ◽  
Growth Models ◽  
Pinus Resinosa ◽  
Site Index ◽  
Ecological Systems ◽  
Red Pine ◽  
The Self ◽  
Site Quality ◽  
Modeling Framework ◽  
Lake States

Forest management demands thorough knowledge of ecological systems. Tree interaction dynamics are one component of these ecological systems. Developing growth models which incorporate ecological "laws" such as the self-thinning rule can lead to better understanding of the laws, to better understanding of what is still unknown, and to what is in need of refinement. To this end a system of simultaneous differential equations incorporating logical, linked hypotheses regarding growth and mortality is proposed and fit to data from red pine (Pinus resinosa Ait.) plantations in the Lake States (Minnesota, Michigan, and Wisconsin). Using this modeling framework it appears that stand initiation history has a large impact on the level of the self-thinning boundary for red pine growing in the Lake States. Stands with initially high density exhibited lower self-thinning boundaries than stands with lower densities. Site quality (as measured by site index) chiefly affected the rate at which stand dynamics progress. Higher quality sites progressed through stand development at faster rates than did sites with lower quality.

scholarly journals Effects of Stand Density on Top Height Estimation for Ponderosa Pine

2012 ◽  
Vol 27 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Martin Ritchie ◽  
Jianwei Zhang ◽  
Todd Hamilton
Keyword(s):  
Ponderosa Pine ◽  
Stand Density ◽  
Tree Height ◽  
Site Index ◽  
Fixed Number ◽  
Site Quality ◽  
Height Estimation ◽  
Growing Stock ◽  
Dominant Height ◽  
Definition Of

Abstract Site index, estimated as a function of dominant-tree height and age, is often used as an expression of site quality. This expression is assumed to be effectively independent of stand density. Observation of dominant height at two different ponderosa pine levels-of-growing-stock studies revealed that top height stability with respect to stand density depends on the definition of the dominant height. Dominant height estimates calculated from a fixed number of trees per acre (ranging from 10 to 60 of the tallest trees per acre) were less affected by density than those calculated from a proportion (with the cutoff ranging from 95th to the 70th percentile) of the largest trees in the stand.

scholarly journals Climate-sensitive site index models for Norway

2016 ◽  
Vol 46 (6) ◽  
pp. 794-803 ◽  
Author(s):  
Clara Antón-Fernández ◽  
Blas Mola-Yudego ◽  
Lise Dalsgaard ◽  
Rasmus Astrup
Keyword(s):  
Climate Change ◽  
Site Index ◽  
National Forest Inventory ◽  
Climatic Conditions ◽  
Site Quality ◽  
Climate Change Scenarios ◽  
Climate Data ◽  
Intergovernmental Panel ◽  
Potential Component ◽  
Using Data

The present study aims to develop biologically sound and parsimonious site index models for Norway to predict changes in site index (SI) under different climatic conditions. The models are constructed using data from the Norwegian National Forest Inventory and climate data from the Norwegian meteorological institute. Site index was modeled using the potential modifier functional form, with a potential component (POT) depending on site quality classes and two modifier components (MOD): temperature and moisture. Each of these modifiers was based on a portfolio of candidate variables. The best model for spruce-dominated stands included temperature as modifier (R2= 0.56). In the case of pine- and deciduous-dominated stands, the best models included both modifiers (R2= 0.40 and 0.54 for temperature and moisture, respectively). We illustrate the use of the models by analyzing the possible shift in SI for year 2100 under one (RCP4.5) of the benchmark scenarios adopted by the Intergovernmental Panel on Climate Change for its fifth assessment report. The models presented can be valuable for evaluating the effect of climate change scenarios in Norwegian forests.

Leaf area - sapwood area relations of lodgepole pine as influenced by stand density and site index

1988 ◽  
Vol 18 (2) ◽  
pp. 247-250 ◽  
Author(s):  
James N. Long ◽  
Frederick W. Smith
Keyword(s):  
Leaf Area ◽  
Forest Ecology ◽  
Lodgepole Pine ◽  
Stand Density ◽  
Site Index ◽  
Site Quality ◽  
Cross Sectional ◽  
Sapwood Area ◽  
Pine Trees ◽  
Stand Conditions

Leaf area to sapwood area ratios for a given species are believed to vary with factors such as site quality, stand density, early stand growth rates, and crown class. Based on data from 55 mature lodgepole pine trees (Pinuscontorta var. latifolia Dougl.) from 10 plots in southeastern Wyoming, we conclude that putative density and site effects on leaf area - sapwood area relations are actually a consequence of the increase in the leaf area to sapwood area ratio with increasing sapwood area. When leaf area is estimated with a nonlinear model that includes tree size and distance to the live crown, the apparent effects of stand density and site index disappear. We consider a constant ratio of leaf area and sapwood cross-sectional area to be inappropriate for the estimation of leaf area aross the range of stand conditions included in most studies of forest ecology.

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