Environ Monit Assess (2018) 190:377 https://doi.org/10.1007/s10661-018-6754-8 Influence of interspecies competition on beech (Fagus orientalis Lipsky) trees and some features of stand in mixed broad-leaved forest Kambiz Abrari Vajari Received: 15 December 2017 /Accepted: 25 May 2018 # Springer International Publishing AG, part of Springer Nature 2018 Abstract Oriental beech (Fagus orientalis Lipsky) coexistence and planning mixtures in temperate is one of the most important commercial tree spe- broad-leaved forests. cies in the Hyrcanian region. This species is known to suffer from strong intra- and interspecific com- Keywords Broad-leaved tree . Competition index . petition for above- and below-ground resources in Temperate forest . Tree architecture temperate mixed stands. In the present study, a total of 26 beech trees and their surroundings trees as well as stand characteristics were evaluated for Introduction determining the interactions between them and competition index (CI) in mixed beech stand. The Competition is a relationship between trees for results showed that in mixed beech stand, there gaining the growing space and taking limited re- were positive correlation between CI and crown sources such as light, nutrients, and water via their ratio and height/diameter (HD) ratio of target beech growth and development (Van de Peer et al. 2017). trees, but negatively correlated to crown length, A major ecological process that makes key role in crown width, crown area, and crown volume. Total growing and species replacement (Maleki et al. height, DBH, and bole of target beech trees were 2015) and also in tree’s structure and composition decreased with increasing CI. Regression analysis (Fichtner et al. 2012) is competition among trees. showed that CI had positive significant correlation The interactions between plants make a vital role in with functional group of forb richness. The target controlling plant composition (Kunstler et al. 2011) beech trees characteristics including HD ratio and and influenced via a lot of parameters (Guo et al. crown ratio showed contrasting responses to some 2016). A lot of parameters control the growth of variables which were related to their known specif- trees, but one of them is competition among trees ic ecological strategies. This study demonstrates the which can be determined via silvicultural tools different responses of target beech trees in oversto- (Metz et al. 2013). For measuring tree competition, ry to competition in neighborhood conditions which several competition indices have been considered are an important factor in retaining species (Metz et al. 2013) and using competition indices are an important subject of forestry in the world (Pedersen et al. 2013). Several studies show the * K. Abrari Vajari ( ) responses of trees to competition factor in forest Faculty of Agriculture and Natural Resource, Lorestan University, Khorramabad, Iran such as crown architecture (Barbeito et al. 2014; e-mail: [email protected] Bayer et al. 2013; Olivier et al. 2016), tree size e-mail: [email protected] (Antin et al. 2013;Thorpeetal.2010), basal area 377 Page 2 of 7 Environ Monit Assess (2018) 190:377 increment (Contreras et al. 2011), tree morphology of providing information for practical management (Lang et al. 2010), stem girth increment (Martín of beech stands in temperate forest, especially et al. 2014), and crown modeling (Metz et al. selecting the silvicultural methods. 2013). In all studies, competition appeared to be more important factor, which has been shown to impact crown size, architecture, and tree Materials and methods morphology through its various components within forests. Measuring some characteristics of trees Study area within forest stand and their interactions with other trees can be used for evaluating them in The research took place in Hyrcanian beech forest lo- order to design silvicultural operations. For cated (36°, 12′,37″ N and 53°, 25′,47″ E) in Northern example, Sharma et al. (2016) declared that the Iran (Mazandaran province) with an elevation range crownsizesareusedtoevaluatesometreecharac- from 1010 to 1020 ma.s.l. The parent material of this teristics including strength and health of trees, region is marl, conglomerate, and alluvial belonging to wood quality, resistant to wind, and stand density. Pliocene epoch. The predominant soil type is Tree competition can be used as important factor pseudogley. The study site is characterized by a humid for predicting growth of trees (Contreras et al. climate with a mean annual precipitation 858 mm and a 2011) and in mixed stand with complex structure; mean annual temperature of 10.5 °C. The forest area is it is believed that tree competition is considered as dominated by deciduous broad-leaf trees and comprises an obvious process (von Oheimb et al. 2011). 58.5 ha. Four species, oriental beech (Fagus orientalis Quantifying the influences of competition on the Lipsky), Alder (Alnus subcordata C.A.Mey), ironwood different components of trees may be vital to un- (Parrotia persica C.A.Mey), and hornbeam (Carpinus derstanding tree responses and to predict species betulus L.), comprise the overstory layers within stand, ability to compete with neighboring trees with oriental beech more common at higher height. The (Barbeito et al. 2014). Oriental beech (Fagus beech-ironwood trees along with other tree species orientalis Lipsky), as shade-tolerant tree, is one of formed the mixed uneven aged forest type (high forest) the most important commercial tree species and it and the past applied silvicultural system was the selec- plays significant ecological role in the Hyrcanian tion system. region. Beech stands mixed with other broad-leaved species are known to suffer from strong intra- and Field measurements interspecific competition for above- and below- ground resources in temperate mixed stands. To Data sampling was performed during summer 2017 on investigate the influence of neighborhood competi- 26 plots which were selected in a 100 m × 150 m regular tion on target beech trees, the present study was grid within beech stand. At the center of each plot, a carried out in a mixed broad-leaved forest of ori- single stemmed beech trees were sampled in overstory ental beech, hornbeam, ironwood, and Alder in the as target trees (totally 26 trees).The position of the Hyrcanian region, Northern Iran. The main purpose neighbors to the target beech tree was defined by mea- of this study was to identify the correlation between suring the horizontal distance from stem base to stem distant-dependent competition index (CI) caused by base and all trees were determined to species level (von neighboring trees and oriental beech (Fagus Oheimb et al. 2011). The morphological parameters orientalis Lipsky) species and also some stand fea- were measured for each target tree including stem di- tures within mixed broad-leaf temperate forest in ameter at a height of 1.30 m (dbh > 10 cm), total tree the Hyrcanian region. The specific objectives of the height (m), crown length and width (m), crown area study were to (1) identify the correlation between (m2) and volume(m3), height to diameter ratio of the CI and target beech tree characteristics, (2) evaluate tree (the slenderness factor, H/D), crown ratio (crown the interaction between CI and some environmental length–tree height ratio), and bole (m). Crown radius factors in beech stand, and (3) determine the rela- was calculated as the mean value of radii in four differ- tionship of crown and HD ratio with target beech ent directions (N, E, S, W).The crown surface area tree structure. The results can be used with the aim (CSA) and the crown volume (CV) were calculated Environ Monit Assess (2018) 190:377 Page 3 of 7 377 (Promis et al. 2009), supposing that the crown of target normal distribution. Thus, for the comparison of CI in tree has a parabolic shape: different diameter classes of target beech trees, paramet- ÀÁ ric statistics (independent T test) was used. A one-way π Â R 1:5 CSA ¼ Â R2 þ 4 Â C2 −R3 ð1Þ ANOVA (analyses of variance) was performed for ana- Â 2 L 6 CL lyzing the effect of species neighbor identity on the distance parameter and also on the diameter at breast R2 Â C CV ¼ π Â L ð2Þ height (DBH) of trees. The S.N.K. test was used for 2 multiple comparisons of species neighbor identity in where CL (m) is the crown length and R is crown radius relation to distance parameter and DBH (cm) following (m). To calculate the competition index (CI), the follow- the results of ANOVA. To calculate interaction between ing distance-dependent competition index was used of CI and some features of target trees and ecological ’ (Xiang et al. 2013): factors, Pearson s correlation coefficient was used. All ÀÁ data were analyzed with the use of SPSS version 20.0 2 and the statistical significance was based on α =0.05 n dbh j=dbhi CI ¼ ∑ ð3Þ and 0.01. j¼1 distij þ 1 where n is the total number of neighbor trees within the 6–8 m radius of the target tree, dbhi and dbhj are dbh Results (cm) of a target tree (i) and its neighbor trees (j), and distij is the horizontal distance (m) between the target The diameter at breast height (DBH) differed signifi- tree (i)andtheneighbortree(j). The beech target trees in cantly among the three neighbor trees species in the mixed conditions were surrounded by other tree species mixed stand (Table 2). The diameter at breast height including hornbeam, ironwood, and beech. In addition, was significantly higher in beech than in the other some variables including humus and litter thickness species. (cm), forb and graminoid richness (SR), herb layer The size of the distance between adjacent crowns of diversity (Simpson’s index diversity), and beech regen- neighbor trees did not differ significantly in regard to the eration within each plot were measured for determining species pair considered (Table 3).