# Relationships between Structural Indices and Conventional Stand Attributes in an Old-Growth Forest in Southeast Europe

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

^{2}to 1500 m

^{2}. The measures of tree species mingling and tree species diversity were strongly associated with each other, while their association with diameter variability was weak to moderately strong. Tree species mingling index was strongly associated with the changes in tree species proportions. However, conventional stand attributes were generally not strongly correlated with the examined indices. For restoring and maintaining old-growth characteristics, forest managers may use structural indices to increase small-scale structural heterogeneity, tree species mingling, and diversity, but only as an additional set of measures, not as surrogates for conventional stand attributes.

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Study Area

^{−1}. The mean and maximum DBH are 24.4 cm and 134.5 cm, respectively. DBH distribution cumulatively for all species at the stand level is rotated-sigmoid. Species composition, with respect to the number of trees, favors beech (56%), followed by fir (38%) and spruce (3%). The basal area amounts to 68.5 m

^{2}·ha

^{−1}, of which fir comprises 53%, beech 37%, and spruce 6%. The share of other species is below 2%, including Acer pseudoplatanus (L.), Fraxinus excelsior (L.), and Ulmus glabra (Huds.).

#### 2.2. Field Measurements

^{2}), a middle plot (radius 17.84 m, area 1000 m

^{2}), and an outer plot covering whole plot area (radius 21.85 m, area 1500 m

^{2}). On each plot, the tree species were distinguished, and the diameters of all trees with DBH ≥ 6.0 cm were cross-measured in two perpendicular directions at 1.30 m above the ground. In order to calculate DBH differentiation (T) and species mingling (M) indices, x and y coordinates were recorded for each tree on each of the 48 plots.

#### 2.3. Data Analysis

_{j}stands for basal area (m

^{2}) of tree with rank j.

^{2}, 1000 m

^{2}, and 1500 m

^{2}, while T and M were first calculated for each tree, and then the average index values were computed at the mentioned nested plot levels. Consequently, these average values of T and M indices were used in the analysis. In order to avoid potential issues related to edge effects, for the computation of these indices, we used only those trees within the 1500 m

^{2}plot for which all neighbors were known/recorded. If the distance from the plot boundary was shorter than that from the nth neighbor, then the nearest trees to tree i may occur outside of the plot. In this case, the trees close to the plot boundary for which the closest neighbors were not known were excluded from the analysis in order to avoid edge effect bias [39,40].

_{4}, M

_{4}, H′) in this study were also evaluated by running a set of Pearson’s correlations to gain insight into how strongly these variables might be associated. In the latter case, strong linear relationships could potentially enable more straightforward usage of structural indices in forestry practice. Complete data analysis was performed in the R statistical package, Version 3.5.1 [41].

## 3. Results

#### 3.1. Descriptive Statistics and Frequency Distributions of All Examined Indices

_{4}for DBH differentiation index and M

_{4}for tree species mingling index.

_{4}on plots ranging from 200 m

^{2}to 1500 m

^{2}were constant, amounting to 0.67 and 0.47, respectively. Likewise, the mean values of M

_{4}(0.41–0.42) were also stable across plots of different sizes. The values of H′ index increased with plot size (Table 1). GC was characterized by left-skewed frequency distributions regardless of plot size (for the largest 1500 m

^{2}plots, p < 0.001). On the other hand, T

_{4}and M

_{4}, as well as the Shannon index (H′) for tree species diversity, exhibited normal frequency distributions regardless of plot size. However, heteroscedasticity was significant for GC (p < 0.001), T

_{4}(p = 0.015) and M

_{4}(p = 0.010), whereas H′ index had equal variances between plots of different size.

#### 3.2. Behavior of Indices with the Change of Plot Size

_{4}and M

_{4}indices were not significantly correlated either with plot size or tree number. The Shannon index (H′) for tree species diversity was similar between the 1000 m

^{2}and 1500 m

^{2}plots, whereas significant differences were found when the smallest 200 m

^{2}plots were compared to the 1000 m

^{2}(p = 0.021) and 1500 m

^{2}(p = 0.011) plots (Figure 2).

#### 3.3. Associations among Indices and Their Correlations with Stand Attributes

_{4}, M

_{4}, and GC were significant only on the 1000 m

^{2}and 1500 m

^{2}plots, but the strength of these correlations was weak to moderate. The Shannon index for tree species diversity (H′) correlated significantly and strongly only with M

_{4}(Table 3).

^{2}, the species mingling index M was positively associated with the relative share of conifers/broadleaves by tree number (r = 0.62; p < 0.001) and with the relative share of conifers/broadleaves by basal area (r = 0.47; p < 0.001). On the 1000 m

^{2}and 1500 m

^{2}plots, the species mingling index M was even better related to the relative share of conifers/broadleaves by tree number (r = 0.71; p < 0.001).

_{4}index (r = 0.46; p = 0.001). Similarly, the values of T

_{4}index on the 1000 m

^{2}and 1500 m

^{2}plots were positively associated with the absolute densities of broadleaved trees (r = 0.51; p < 0.001), as well as with the absolute densities of all trees (r = 0.49; p < 0.001). In addition, the basal area of broadleaves showed a moderate correlation with GC values (r = 0.42; p = 0.003). However, except for M

_{4}index, it is important to notice that the associations of basal area and species proportions with GC, T

_{4}, and H′ were weak to moderately strong at different plot sizes (Pearson’s r values ranged from 0.30 and 0.54). Likewise, independent of plot size, only moderate associations of mean DBH with T

_{4}and M

_{4}were determined. Mean DBH had a relatively strong correlation only with GC values on the 1000 m

^{2}(r = 0.57; p < 0.001) and 1500 m

^{2}(r = 0.66; p < 0.001) plots.

## 4. Discussion

#### 4.1. Local DBH Differentiation, Species Mingling, and Diversity in Perućica

^{2}seem sufficient to capture DBH differentiation and tree species mingling in this forest. However, in forest stands that may exhibit spatial autocorrelation [10], such as by creating cohorts of trees with very similar DBHs or cohorts composed of the same tree species, then larger plot areas might be needed to detect changes in DBH differentiation and species mingling. Consequently, future studies may try to include forest stands that exhibit positive spatial autocorrelation. Regarding Shannon’s H′ index, in this study, even a small increase in the plot size resulted in higher tree species diversity. However, we could expect that the larger the species spatial autocorrelation, that is, the larger the cohorts of one species, the larger the plot area would be required to “capture” additional tree species. This also remains an important task for future studies.

#### 4.2. Relationships between the Evaluated Indices and Conventional Stand Attributes

^{2}and 1500 m

^{2}. We also found that the absolute densities of broadleaved trees were moderately associated with T

_{4}. Strong correlations were found only between tree species mingling index M

_{4}and tree species proportions (see also [2]). Namely, it can be expected that the species with a small share will exhibit high tendency toward mingling with other species, whereas its mingling pattern will probably change with its increased share in the species composition. To verify this statement, additional studies from different forest types would be needed. It would therefore be valuable for future studies to analyze forest stands where two or more species have approximately equal shares in the tree species composition at stand or plot scales. The information from such studies could reveal the true mingling tendency of each constituent tree species.

## 5. Conclusions

_{4}indices, small-scale structural heterogeneity was similar between plots of different sizes (200 m

^{2}, 1000 m

^{2}, and 1500 m

^{2}). The tree species mingling index (M

_{4}) was also rather stable across plots of different sizes. The probability of finding additional tree species (hence diversity) increased with plot size.

_{4}and H′) were strongly associated with each other. On the other hand, the associations between structural indices GC and T

_{4}were rather weak. Thus, the comparison of structural heterogeneity between different sites will only be reasonable using the same index and a similar or the same sampling procedure. The GC was also weakly associated with tree species mingling and diversity, while a moderate association was determined between T

_{4}and M

_{4}indices.

_{4}correlated fairly strongly with the changes in tree species proportions. However, mean DBH, absolute tree density, and basal area were weakly to moderately associated with all analyzed indices (GC, T

_{4}, M

_{4}, H′). Consequently, for restoring and maintaining old-growth characteristics, forest managers may use structural indices to increase local structural heterogeneity, tree species mingling, and diversity, but only as an additional set of measures, not as surrogates for conventional stand attributes. Therefore, future studies will need to include additional stand attributes and perhaps even environmental factors in order to better explain the local variability of structural indices.

## Author Contributions

## Funding

## Conflicts of Interest

## References

- McElhinny, C.; Gibbons, P.; Brack, C.; Bauhus, J. Forest and woodland stand structural complexity: Its definition and measurement. For. Ecol. Manag.
**2005**, 218, 1–24. [Google Scholar] [CrossRef] - Schall, P.; Schulze, E.D.; Fischer, M.; Ayasse, M.; Ammer, C. Relations between forest management, stand structure and productivity across different types of Central European forests. Basic Appl. Ecol.
**2018**, 32, 39–52. [Google Scholar] [CrossRef] - Keeton, W.S. Managing for late-successional/old-growth characteristics in northern hardwood-conifer forests. For. Ecol. Manag.
**2006**, 235, 129–142. [Google Scholar] [CrossRef] - Korpel, S. Die Urwälder der Westkarpaten; Gustav Fischer Verlag: Stuttgart, Germany; Jena: New York, NY, USA, 1995. [Google Scholar]
- Vrška, T.; Adam, D.; Hort, L.; Kolář, T.; Janík, D. European beech (Fagus sylvatica L.) and silver fir (Abies alba Mill.) rotation in the Carpathians—A developmental cycle or a linear trend induced by man? For. Ecol. Manag.
**2009**, 258, 347–356. [Google Scholar] [CrossRef] - Jaworski, A.; Kołodziej, Z.; Łapka, M. Mortality, recruitment, and increment of trees in the Fagus-Abies-Picea stands of a primeval character in the lower mountain zone. Dendrobiology
**2007**, 57, 15–26. [Google Scholar] - Diaci, J.; Rozenbergar, D.; Anic, I.; Mikac, S.; Saniga, M.; Kucbel, S.; Visnjic, C.; Ballian, D. Structural dynamics and synchronous silver fir decline in mixed old-growth mountain forests in Eastern and Southeastern Europe. Forestry
**2011**, 84, 479–491. [Google Scholar] [CrossRef][Green Version] - Zenner, E.K.; Peck, J.L.E. Floating neighborhoods reveal contribution of individual trees to high sub-stand scale heterogeneity. For. Ecol. Manag.
**2018**, 412, 29–40. [Google Scholar] [CrossRef] - Mauro, F.; Haxtema, Z.; Hailemariam, T. Comparison of sampling methods for estimation of nearest-neighbor index values. Can. J. For. Res.
**2017**, 47, 703–7015. [Google Scholar] [CrossRef][Green Version] - Pommerening, A.; Grabarnik, P. Individual-Based Methods in Forest Ecology and Management, 1st ed.; Springer International Publishing: Berlin/Heidelberg, Germany, 2019. [Google Scholar]
- Neumann, M.; Starlinger, F. The significance of different indices for stand structure and diversity in forests. For. Ecol. Manag.
**2001**, 145, 91–106. [Google Scholar] [CrossRef] - Li, Y.; Hui, G.; Yu, S.; Luo, Y.; Yao, X.; Ye, S. Nearest neighbour relationships in Pinus yunnanensis var. Tenuifolia forests along the Nanpan River, China. iForest
**2017**, 10, 746–753. [Google Scholar] [CrossRef][Green Version] - Nagel, T.A.; Mikac, S.; Dolinar, M.; Klopcic, M.; Keren, S.; Svoboda, M.; Diaci, J.; Boncina, A.; Paulic, V. The natural disturbance regime in forests of the Dinaric Mountains: A synthesis of evidence. For. Ecol. Manag.
**2017**, 388, 29–42. [Google Scholar] [CrossRef] - Szwagrzyk, J.; Maciejewski, Z.; Maciejewska, E.; Tomski, A.; Gazda, A. Forest recovery in set-aside windthrow is facilitated by fast growth of advance regeneration. Ann. For. Sci.
**2018**, 75, 80. [Google Scholar] [CrossRef][Green Version] - Nagel, T.A.; Svoboda, M. Gap disturbance regime in an old-growth Fagus–Abies forest in the Dinaric Mountains, Bosnia-Herzegovina. Can. J. For. Res.
**2008**, 38, 2728–2737. [Google Scholar] [CrossRef][Green Version] - Nagel, T.A.; Svoboda, M.; Rugani, T.; Diaci, J. Gap regeneration and replacement patterns in an old-growth Fagus-Abies forest of Bosnia-Herzegovina. Plant Ecol.
**2010**, 208, 307–318. [Google Scholar] [CrossRef] - Nagel, T.A.; Svoboda, M.; Kobal, M. Disturbance, life history traits, and dynamics in an old-growth forest landscape of southeastern Europe. Ecol. Appl.
**2014**, 24, 663–679. [Google Scholar] [CrossRef] - Gadow, K.; Zhang, C.Y.; Wehenkel, C.; Pommerening, A.; Corral-Rivas, J.; Korol, M.; Myklush, S.; Hui, G.Y.; Kiviste, A.; Zhao, X.H. Forest structure and diversity. In Continuous Cover Forestry; Pukkala, T., Gadow, K., Eds.; Springer Science + Business Media: Berlin/Heidelberg, Germany, 2012; pp. 29–84. [Google Scholar]
- Motz, K.; Sterba, H.; Pommerening, A. Sampling measures of tree diversity. For. Ecol. Manag.
**2010**, 260, 1985–1996. [Google Scholar] [CrossRef] - Pretzsch, H. Forest Dynamics, Growth and Yield; Springer: Berlin/Heidelberg, Germany, 2009. [Google Scholar]
- O’Hara, K.L.; Hasenauer, H.; Kindermann, G. Sustainability in multi-aged stands: An analysis of long-term plenter systems. Forestry
**2007**, 80, 163–181. [Google Scholar] [CrossRef][Green Version] - Pukkala, T.; von Gadow, K. Continuous Cover Forestry; Springer: Dordrecht, The Netherlands, 2012. [Google Scholar]
- Shannon, C.E.; Weaver, W. The Mathematical Theory of Communication; University of Illinois Press: Urbana, IL, USA, 1949. [Google Scholar]
- Pommerening, A. Evaluating structural indices by reversing forest structural analysis. For. Ecol. Manag.
**2006**, 224, 266–277. [Google Scholar] [CrossRef] - Peck, J.E.; Zenner, E.K.; Brang, P.; Zingg, A. Tree size distribution and abundance explain structural complexity differentially within stands of even-aged and uneven-aged structure types. Eur. J. For. Res.
**2014**, 133, 335–346. [Google Scholar] [CrossRef] - Bončina, A. History, current status and future prospects of uneven-aged forest management in the Dinaric region: An overview. Forestry
**2011**, 84, 467–478. [Google Scholar] [CrossRef] - O’Hara, K.L.; Bončina, A.; Diaci, J.; Anić, I.; Boydak, M.; Curovic, M.; Govedar, Z.; Grigoriadis, N.; Ivojevic, S.; Keren, S.; et al. Culture and Silviculture: Origins and Evolution of Silviculture in Southeast Europe. Int. For. Rev.
**2018**, 20, 130–143. [Google Scholar] [CrossRef] - Fukarek, P.; Stefanović, V. Prasuma Perucica i njena vegetacija. Rad. Poljopr. Fak.
**1958**, 3, 93–146. [Google Scholar] - Stupar, V.; Milanović, Đ. Istorijat Zaštite Prirode Na Području Nacionalnog Parka Sutjeska. Glas. Sumar. Fak. Univ. Banjoj Luci
**2017**, 113–128. [Google Scholar] [CrossRef][Green Version] - Drinić, P. Taksacioni Elementi Sastojina Jele, Smrce i Bukve Prasumskog Tipa u Bosni. Rad. Poljopr. Fak. Sarajevo B
**1956**, 1, 107–160. [Google Scholar] - Keren, S.; Motta, R.; Govedar, Z.; Lucic, R.; Medarevic, M.; Diaci, J. Comparative structural dynamics of the Janj mixed old-growth mountain forest in Bosnia and Herzegovina: Are conifers in a long-term decline? Forests
**2014**, 5, 1243–1266. [Google Scholar] [CrossRef][Green Version] - Motta, R.; Garbarino, M.; Berretti, R.; Bjelanovic, I.; Borgogno Mondino, E.; Čurović, M.; Keren, S.; Meloni, F.; Nosenzo, A. Structure, spatio-temporal dynamics and disturbance regime of the mixed beech–silver fir–Norway spruce old-growth forest of Biogradska Gora (Montenegro). Plant Biosyst. Int. J. Deal. Asp. Plant Biol.
**2015**, 149, 966–975. [Google Scholar] [CrossRef] - Kozák, D.; Mikolá, M.; Svitok, M.; Ba, R.; Paillet, Y.; Larrieu, L.; Nagel, T.A.; Diku, A.; Frankovic, M.; Janda, P.; et al. Profile of tree-related microhabitats in European primary beech-dominated forests. For. Ecol. Manag.
**2018**, 429, 363–374. [Google Scholar] [CrossRef] - Lexerød, N.L.; Eid, T. An evaluation of different diameter diversity indices based on criteria related to forest management planning. For. Ecol. Manag.
**2006**, 222, 17–28. [Google Scholar] [CrossRef] - Sterba, H.; Zingg, A. Abstandsabhängige und abstandsunabhängige Bestandesstrukturbeschreibung. Allg. Forst Jagdztg.
**2006**, 177, 169–176. [Google Scholar] - Füldner, K. Zur Strukturbeschreibung in Mischbeständen. Forstarchiv
**1995**, 66, 235–240. [Google Scholar] - Füldner, K. Die “Strukturelle Vierergruppe”—Ein Stichprobenverfahren zur Erfassung von Strukturparametern in Wäldern. In Beiträge zur Waldinventur; von Gadow, K., Beisch, T., Eds.; Cuvillier Verlag: Göttingen, Germany, 1996; pp. 13–30. [Google Scholar]
- Pommerening, A.; Uria-Diez, J. Do large forest trees tend towards high species mingling? Ecol. Inform.
**2017**, 42, 139–147. [Google Scholar] [CrossRef] - Kuuluvainen, T.; Leinonen, K.; Nygren, M.; Penttinen, A. Statistical opportunities for comparing stand structural heterogeneity in managed and primeval forests: An example from boreal spruce forest in southern Finland. Silva Fenn.
**1996**, 30, 315–328. [Google Scholar] [CrossRef][Green Version] - Pommerening, A.; Stoyan, D. Edge-correction needs in estimating indices of spatial forest structure. Can. J. For. Res.
**2006**, 36, 1723–1739. [Google Scholar] [CrossRef][Green Version] - R Core Team. A Language and Environment for Statistical Computing; Foundation for Statistical Computing: Vienna, Austria, 2018. [Google Scholar]
- Sterba, J.; Sterba, H. The semi-logarithmic stem number distribution and the Gini-index—Structural diversity in “balanced” dbh-distributions. Austrian J. For. Sci.
**2018**, 135, 19–31. [Google Scholar] - Ponce, D.B.; Donoso, P.J.; Salas-Eljatib, C. Differentiating structural and compositional attributes across successional stages in chilean temperate rainforests. Forests
**2017**, 8, 329. [Google Scholar] [CrossRef][Green Version] - Balanda, M. Spatio-temporal structure of natural forest: A structural index approach. Beskydy
**2012**, 5, 163–172. [Google Scholar] [CrossRef][Green Version] - Parobeková, Z.; Pittner, J.; Kucbel, S.; Saniga, M.; Filípek, M.; Sedmáková, D.; Vencurik, J.; Jaloviar, P. Structural diversity in a mixed spruce-fir-beech old-growth forest remnant of the Western Carpathians. Forests
**2018**, 9, 379. [Google Scholar] [CrossRef][Green Version] - Keren, S.; Diaci, J.; Motta, R.; Govedar, Z. Stand structural complexity of mixed old-growth and adjacent selection forests in the Dinaric Mountains of Bosnia and Herzegovina. For. Ecol. Manag.
**2017**, 400, 531–541. [Google Scholar] [CrossRef] - Seidling, W.; Travaglini, D.; Meyer, P.; Waldner, P.; Fischer, R.; Granke, O.; Chirici, G.; Corona, P. Dead wood and stand structure—Relationships for forest plots across Europe. iForest
**2014**, 7, 269–381. [Google Scholar] [CrossRef] - Szmyt, J.; Dobrowolska, D. Spatial diversity of forest regeneration after catastrophic wind in northeastern Poland. iForest
**2016**, 9, 414–421. [Google Scholar] [CrossRef][Green Version] - Barbeito, I.; Cañellas, I.; Montes, F. Evaluating the behaviour of vertical structure indices in Scots pine forests. Ann. For. Sci.
**2009**, 66, 710. [Google Scholar] [CrossRef][Green Version] - Sterba, H. Diversity indices based on angle count sampling and their interrelationships when used in forest inventories. Forestry
**2008**, 81, 587–597. [Google Scholar] [CrossRef][Green Version]

**Figure 1.**Frequency distributions of the Gini coefficient (GC), diameter differentiation index (T

_{4}), species mingling index (M

_{4}), and Shannon index (H′) in the Perućica old-growth forest based on 48 plots, each with an area of 1500 m

^{2}.

**Figure 2.**Boxplots of the Gini coefficient (GC), diameter differentiation index (T

_{4}), tree species mingling index (M

_{4}), and Shannon index (H′) for different plot sizes. The small inner box represents the median, the large box represents the interquartile range, and the whiskers extend to the lowest and highest values below and above the first and third quartile. Small circles stand for outliers that are more than 1.5-times the interquartile range.

**Table 1.**Statistical summary for the Gini coefficient (GC), diameter differentiation index (T

_{4}), species mingling index (M

_{4}), and Shannon index for tree species diversity (H′) on plots of different sizes in the Perućica old-growth forest.

Plot size | Index | Mean | Median | Min. | Max. | St. Dev. |
---|---|---|---|---|---|---|

200 m^{2} | GC | 0.67 | 0.70 | 0.32 | 0.88 | 0.14 |

T_{4} | 0.47 | 0.47 | 0.33 | 0.62 | 0.06 | |

M_{4} | 0.41 | 0.43 | 0.06 | 0.75 | 0.17 | |

H′ | 0.59 | 0.64 | 0.00 | 1.20 | 0.27 | |

1000 m^{2} | GC | 0.67 | 0.68 | 0.40 | 0.78 | 0.08 |

T_{4} | 0.47 | 0.47 | 0.38 | 0.55 | 0.04 | |

M_{4} | 0.42 | 0.44 | 0.15 | 0.70 | 0.12 | |

H′ | 0.72 | 0.69 | 0.34 | 1.38 | 0.22 | |

1500 m^{2} | GC | 0.67 | 0.69 | 0.37 | 0.77 | 0.08 |

T_{4} | 0.47 | 0.47 | 0.37 | 0.54 | 0.04 | |

M_{4} | 0.42 | 0.42 | 0.10 | 0.70 | 0.12 | |

H′ | 0.73 | 0.69 | 0.25 | 1.34 | 0.21 |

**Table 2.**Mean and median values of species mingling index with one (M

_{1}), two (M

_{2}), three (M

_{3}), and four (M

_{4}) neighbor trees on 1500 m

^{2}plots in the Perućica old-growth forest.

Tree Species | European Beech | Silver Fir | Norway Spruce | |||
---|---|---|---|---|---|---|

Mingling Indices | Mean | Median | Mean | Median | Mean | Median |

M_{1} | 0.30 | 0.00 | 0.45 | 0.00 | 0.74 | 1.00 |

M_{2} | 0.31 | 0.00 | 0.46 | 0.50 | 0.79 | 1.00 |

M_{3} | 0.31 | 0.33 | 0.46 | 0.33 | 0.81 | 1.00 |

M_{4} | 0.31 | 0.25 | 0.47 | 0.50 | 0.81 | 1.00 |

**Table 3.**Pearson’s r coefficients for correlations between the Gini coefficient (GC), diameter differentiation index (T

_{4}), tree species mingling index (M

_{4}), and Shannon index for tree species diversity (H′) for different plot sizes.

Plot Size 200 m^{2} | |||

Index | T_{4} | M_{4} | H′ |

GC | 0.25 | 0.09 | 0.15 |

T_{4} | - | 0.19 | 0.08 |

M_{4} | - | - | 0.87 *** |

Plot Size 1000 m^{2} | |||

Index | T_{4} | M_{4} | H′ |

GC | 0.32 * | 0.05 | 0.05 |

T_{4} | - | 0.36 * | 0.11 |

M_{4} | - | - | 0.85 *** |

Plot Size 1500 m^{2} | |||

Index | T_{4} | M_{4} | H′ |

GC | 0.32 ** | 0.15 | 0.16 |

T_{4} | - | 0.43 *** | 0.14 |

M_{4} | - | - | 0.86 *** |

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Keren, S.; Svoboda, M.; Janda, P.; Nagel, T.A. Relationships between Structural Indices and Conventional Stand Attributes in an Old-Growth Forest in Southeast Europe. *Forests* **2020**, *11*, 4.
https://doi.org/10.3390/f11010004

**AMA Style**

Keren S, Svoboda M, Janda P, Nagel TA. Relationships between Structural Indices and Conventional Stand Attributes in an Old-Growth Forest in Southeast Europe. *Forests*. 2020; 11(1):4.
https://doi.org/10.3390/f11010004

**Chicago/Turabian Style**

Keren, Srđan, Miroslav Svoboda, Pavel Janda, and Thomas A. Nagel. 2020. "Relationships between Structural Indices and Conventional Stand Attributes in an Old-Growth Forest in Southeast Europe" *Forests* 11, no. 1: 4.
https://doi.org/10.3390/f11010004