Phân tích đặc điểm cây lân cận gần nhất của rừng lá rộng nhiệt đới

Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 5 - 2017 43 ANALYZING OF NEAREST NEIGHBORHOOD CHARACTERISTICS OF TROPICAL BROADLEAVED FOREST STANDS Nguyen Hong Hai Vietnam National University of Forestry SUMMARY Spatial structure is one of the major parameters for describing forest stand structure. We applied a new method to quantitative analysis spatial structure of forest stand based on nearest neighbour distance between tree groups. Three 1-ha plots (100 m x 100 m) were designed on the tropical broadleaved forests to validate the distribution of structural parameters. All tree with diameter at breast high (DBH) ≥ 6 cm were mapped, measured tree DBH and classified species. We calculated and described structural parameters such as Mingling, DBH dominance and Uniform Angle Index by using Crancod and Microsoft Excel softwares. The results showed that: most of studied species were found highly mixed with other species. In DBH dominance analysis, most of dominant tree species in Ha Tinh and Binh Dinh plots were less competition in tree DBH comparing to nearest neighbours. However, three species had positive advantage in tree size, therefore bearing higher competitive capacity for nutrient resources. About spatial distribution, most of tree species in three studied plots were from regular to clumped patterns but mainly focused at random pattern. The spatial structural parameters offer direct information and valuable about spatial structure of forest stand. Those information can be used in thinning of sustainable forest management, modelling and restoration. Keywords: Broadleaved forest, dominance, mingling, nearest neighborhood, uniform angle index. I. INTRODUCTION Structural characteristics of forest stand can be describe as the distribution characteristics of individuals of the same species, which is typically represented by different diameters and tree ages (Li et al., 2002). In a given space, population structure is vulnerable to isolation from other populations within the same community, therefore, for any tree species in a mixed forest, interspecific and intraspecific differences in tree size, species mingling and distribution patterns may be the most important characteristics of population structure. Distribution patterns directly reflect the way individuals assemble or scatter in space, which may in turn be associated with conditions of competition and utilization of environmental resources among adjacent trees. Tree size is directly related to the degree of maturation of a tree population and to the competitive advantage of the population within the community, it may also be directly related to the survive viability and ecological niche of the population. Intraspecific aggregation involves isolation between species in the same community, and the process is close to seed dispersal, regeneration capacity and growth. A number of methods for describing forest structural attributes have been largely developed for decades. However, an exact description of small-scale structural attributes is considered to be increasingly importance (Corral-Rivas et al. 2010). Recently, new individual tree indices, such as uniform angle index, species mingling and dominance (Gadow et al. 1998; Aguirre et al. 2003; Hui et al. 2011), have been developed. The basic idea of these indices is to characterize the neighborhood of a reference tree by its using n- nearest neighbors. The techniques of nearest neighbor statistics allow us determining the relationship within neighborhood groups of trees such as species and size class at small scales. This method has several advantages Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 44 over using expression frequency to depict the attributes among individuals when compared to the traditional methods (Pommerening 2002). For instance, greater inhomogeneity in species and homogeneity in size classes indicate greater structural diversity al. 2012). In this study, our overall goal is to characterize spatial attributes of neighborhood trees by applying the current techniques of nearest neighbor statistics. For a better understanding of structural units, we three structural units for each species analyses, such as mingling - index, mingling - dominance and dominance uniform angle index. II. RESEARCH METHODOLOGY 2.1. Study site and data collection Three1-ha plots was designed tropical broadleaved forest stand (at coordinates of 18°20'52,13'' N 105°20'16,43'' E), Binh Dinh (at coordinates of 14°8'40.94'' N; 108°54'2.30'' E Hoa (at coordinates of 12 109°4’40,35" E) provinces. In each a grid of 25 subplots (20 m x 2 created in which all trees with diameter at breast height - DBH ≥ 6 cm w Tree position (x, y coordinates) was recorded by using a laser distance measurer (Leica Disto D5) and compass; other characteristics such as species and DBH were also investigated. 2.2. Data analysis We applied current techniques of nearest neighbor statistics which are based on the assumption that the spatial structure of a forest stand determined by the distribution of specific structural relationships within neighborhood groups of trees. A forest stand is composed by (Gadow et combined in uniform angle - in 2012 on s in Ha Tinh ; ) and Khanh °39’48,89" N; study plot, 0 m) was then ere mapped. neighborhood structural units of n used three structural indices proposed by Gadow & Hui (2002) such as species mingling, dominance and uniform angle index to describe homogeneity or heterogeneity of trees through a variety of species, diameter classes and spatial arrangements with equations from 2.1-2.3 (Gadow et al. 1998 2003, Hui et al. 2011, 2011). Species mingling (M): composition and spatial pattern of forest trees. It is defined as the proportion of the n nearest neighbours that are different species from the reference tree (Fig. 1a). vj = 1 if neighbor j is not the same species as reference tree i, otherwise v Dominance (U): differentiation between a reference tree and its four nearest neighbors. It is defined as the proportion of n nearest neighbors that are smaller than reference tree (Fig. vj = 0 if neighbor j is smaller than reference tree i, otherwise vj = 1. Uniform angle index (W): degree of regularity for the four nearest neighbors as reference tree. It is defined as the proportion of angle ( standard angle 0 (Fig. 1c). Wi = 1 if j<0, otherwise W 360°/(n+1). 5 - 2017 -trees. We , Aguirre et al. Pommerening et al. Describes the species (2.1) j = 0. Describes the size 1b). (2.2) Describes the ) smaller than the (2.3) i = 0, 0= JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. Figure 1. Definition of the spatial parameters: Mingling (a), Dominance The methods described above were implemented by using software Crancord ( To eliminate the edge effect of the estimates in M calculation, we applied the nearest neighbor edge correction method proposed by Pommerening & Stoyan (2006). III. RESULTS 3.1. Forest stand properties The forest characteristics were described in Table 1. In Ha Tinh plot, the forest stand was dominated by five tree species, Vatica odorata, Gironniera subaequalis Nephelium melliferum, Calophyllum calaba and Calophyllum calaba. These species gained and Uniform Angle Index (c) i, Wi and Ui including , 42% of tree abundance, 44.7% of total basal area and 43% of important value index (IVI). The Ha Tinh plot was high diversity compared to two other plots. In Binh Dinh plot, six dominant species among total contribute 35% in individu 50% in total basal area and 46% This is highest diversity among three studied plots containing most dominant trees such as Parashorea chinensis, Parashorea chinensis Ilex rotunda, Intsia bijuga Melanorrhoea laccifera annamensis. The most dominant species in Khanh Hoa plot, including wightianum, Diospyros Silviculture 5 - 2017 45 (b) most 97 tree species in al abundance, of total IVI. , , Hopea pierei, and Wringtia Syzygium sylvatica, Nephelium Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 5 - 2017 46 melliferum and Ormosia balansae in total of 47 tree species, contributed more for this community, with 64% in individual abundance, 71% in total basal area and 68% in IVI. Table 1. Characteristics of tree species in the studied plots Plot Species N G IVI Shannon Simpson Ha Tinh Vatica odorata 43 2.1106 11.98 3.34 0.96 Gironniera subaequalis 37 2.3440 11.82 Nephelium melliferum 32 1.7777 9.51 Calophyllum calaba 19 0.9069 5.22 Knema cortiosa 22 0.6857 5.00 53 others 208 9.6709 56.47 Binh Dinh Parashorea chinensis 163 11.1659 21.38 3.70 0.96 Ilex rotunda 50 2.3573 5.29 Intsia bijuga 17 3.3772 4.85 Hopea pierei 48 1.7652 4.49 Melanorrhoea laccifera 26 1.7552 3.38 Wringtia annamensis 46 0.79184 3.24 91 others 649 20.98 57.34 Khanh Hoa Syzygium wightianum 226 11.0721 28.18 2.62 0.87 Diospyros sylvatica 191 9.3845 23.86 Nephelium melliferum 54 2.3009 6.27 Polyalthia nemoralis 34 2.1977 4.95 Ormosia balansae 42 1.7623 4.84 43 others 302 10.4872 31.87 N - species abundance, G - basal area (m2), DBH - diameter at breast height, IVI - important value index, Shannon - Shannon - Wiener index. 3.2. Structural characteristics Analyzed results of Ha Tinh plot was shown in Fig. 2. All five species showed species mixture (Mingling) concentrated at high levels from high mixture to complete mixture, M= 0.75 - 1 in V. odorata, M = 0.5 - 1 in G. subaequalis, M = 0.75 - 1 in N. melliferum, M= 0.5 - 0.75 in C. calaba and M = 0.75 - 1 in K. cortiosa. These evidences shown that these dominant species were highly mixed with other tree species in adjacent neighbours. About DBH dominance to nearest neighbour, V. odorata (U = 0 - 0.75) and N. melliferum (U = 0.50) were dominant to medium advantages. While G. subaequalis (U = 0.75 - 1) and C. calaba (U = 1) were disadvantaged to completely disadvantaged, C. calaba and K. cortiosa were advantaged (U= 0). The results showed that these species were less advantage in DBH comparing to their nearest neighbours, except K. cortiosa. UAI shows spatial distribution of reference individuals to their nearest neighbours. All five dominant species were regular to clumped pattern with W = 0.25 - 0.75 (V. odorata, G. subaequalis, N. melliferum, C. calaba and K. cortiosa). JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. Figure 2. Structural characteristics of five dominant species at Ha Tinh plot Silviculture 5 - 2017 47 Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 48 The results of six dominant species were shown in Fig. 3. All tree species showed high levels of mixing with other species in nearest neighbours. Complete mixture contained chinensis (M = 0.75 - 1), I. rotunda - 1), I. bijuga (M = 1) and H. pi - 1). M. laccifera (M = 0.5 - annamensis (M = 0.25 - 1) varied from low mixture to Complete mixture. Four species were less competitive in tree size with nearest neighbours, their DBH dominaces were medium to complete disadvantage such as P. chinensis I. rotunda (M = 0.5 - 1), I. bijuga Figure 3. Structural characteristics of six dominant species at Binh Dinh plot P. (M = 0.75 erei (M = 0.75 0.75) and W. (U = 0.5 - 1), (M = 0.75 - 1) and M. laccifera (M = 0.75 remaining species, H. pierei W. annamensis (M = 0 advantages from predominance to disadvantage comparing to adjacent neighbours. In spatial distribution, most species ranged from regular to clumped distribution, highly concentrated at random pattern (M 0.5) including P. chinensis rotunda (M = 0.25 - 0.75), and H. pierei (M = 0.5 annamensis (M = 0.25 laccifera (M = 1) was very clump distribution to their neighb 5 - 2017 - 1). While two (M = 0 - 0.75) and - 0.5) had tree size however = (M = 0.25 - 0.75), I. I. bijuga (M = 0.5) - 0.75) and W. - 0.75). Only M. ed orhoods. JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. Figure 3 (cont). Structural characteristics of six dominant species at Binh Dinh plot In Khanh Hoa studied plot dominant species were mixed with nearest neighbours from medium to high mixture including S. wightianum (M = 0.5 sylvatica (M = 0.5 - 1) and N. melliferum 0.5 - 1). However, those species were concentrated at medium level meaning that, in nearest trees, there are less interspecific neighbours. P. nemoralis (M = 0.75) and balansae (M = 1) were shown high to complete mixing with other species in nei Proportions of high advance in DBH dominance were high in S. wightianum Figure 4. Structural characteristics of five dominant species at Khanh Hoa (Fig. 4), three - 1), D. (M = O. ghbourhood. (U = 0 - 1), D. sylvatica (U = 0 (U = 0 - 1) inferring competitive advantage comparing to these nearest neigbours. However, these proportion values were low in (U = 0 - 0.75), O. balansae Spatial patterns were from regular to clumped distribution but mainly at medium level (W = 0.5) such as 0.25 - 0.5), D. sylvatica melliferum (W = 0.25 - 0.75), = 0.5 - 0.75) and O. balansae That mean most of the dominant species were medium to clumped distribution to neighbours Silviculture 5 - 2017 49 - 1) and N. melliferum P. nemoralis (U = 0 - 1). S. wightianum (W = (W= 0.25-0.75), N. P. nemoralis (W (W = 0.5 - 0.75). . plot Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 50 Figure 4 (cont). Structural characteristics of five dominant species at Khanh Hoa plot 3.3. Discussion The relationship between tree individuals and their nearest neighbors is highly potential to elucidate competitive interaction for limited environmental resources, the mutual dependence and species coexistence al. 1998). The structural parameters were considered closely to species association (Gadow et between each individual and its four nearest neighboring trees by the relationship between mixture, size differentiation and distribution pattern, thus, this approach is advantageous compared to the univariate analysis of structural parameters (Li et al. 2014 The results shown evidences that most of studied species were found highly mixed with 5 - 2017 ). Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 5 - 2017 51 other species. In DBH dominance analysis, most of dominant tree species in Ha Tinh and Binh Dinh plots were less competition in tree DBH comparing to nearest neighbours. However, three species, including S. wightianum, D. sylvatica and N. melliferum in Khanh Hoa plot, had positive advantage in tree size, therefore bearing higher competitive capacity for nutrient resources. About spatial distribution, most of tree species in three studied plots were from regular to clumped patterns but mainly focused at random pattern, excepting M. laccifera in strong clumped distribution, comparing to nearest neighbours. These finding may be a reflection of dispersal limitation and development processes of these forest communities. The tendency of species aggregation is common and especially in high tree species diversity forests (Wright 2002), as a pattern of mixed species would lead to a reduction of species diversity due to competitive interaction. This is supported by a finding of Hubbell & Foster (1986) that, in species-rich communities, two individual of the same species may share only a few common species among their nearest neighbors. Moreover, functionally similar species may produce ecological equivalence among species traits which was explained by neutral theory (Hubbell 2006). High diversity species meaning high mixture may also involve seft-thinning process where number of saplings are decreased as average tree size increases over time, consequently increasing chance to replace by other species. Regular pattern can be resulted by interspecific competition between tree species making greater distance between interspecific individuals. IV. CONCLUSION The important practical advantage of this approach is that stand spatial attributes can be determined simply by evaluating the immediate neighbourhoods of a given number of reference trees. Therefore, management methods can be based on considering spatial attributes (size, species and distribution pattern) of each tree, allowing comparison of spatial structure between actual and ideal stand distributions. Our study revealed that selective thinning can improve the health and spatial structure of forest stands and ensure the success of forest management in structurally complex forests. REFERENCES 1. Aguirre O, Hui G, von Gadow K & Jiménez J. (2003) An analysis of spatial forest structure using neighbourhood-based variables. Forest Ecology and Management 183(1): 137-145. 2. Clark PJ & Evans FC. (1954) Distance to nearest neighbor as a measure of spatial relationships in populations. Ecology 35(4): 445-453. 3. Corral-Rivas JJ, Wehenkel C, Castellanos-Bocaz HA, Vargas-Larreta B & Diéguez-Aranda U. (2010) A permutation test of spatial randomness: application to nearest neighbour indices in forest stands. Journal of forest research 15(4): 218-225. 4. Gadow K & Hui G. (2002) Characterizing forest spatial structure and diversity. W: Bjoerk L.[red.]. Sustainable forestry in temperate regions. Materiały konferencyjne IUFRO, Lund: 20-30. 5. Gadow Kv, Zhang CY, Wehenkel C, Pommerening A, Corral-Rivas J, Korol M, Myklush S, Hui GY, Kiviste A & Zhao XH (2012) Forest structure and diversity. Continuous cover forestry, Springer: 29- 83. 6. Hui G, Zhao X, Zhao Z & von Gadow K. (2011) Evaluating tree species spatial diversity based on neighborhood relationships. Forest Science 57(4): 292- 300. 7. Li Y, Hui G, Zhao Z, Hu Y & Ye S. (2014) Spatial structural characteristics of three hardwood species in Korean pine broad-leaved forest—Validating the bivariate distribution of structural parameters from the point of tree population. Forest Ecology and Management 314: 17-25. 8. Pommerening A, Gonçalves AC & Rodríguez- Soalleiro R. (2011) Species mingling and diameter differentiation as second-order characteristics. Allg. Forst-u. J.-Ztg 182: 115-129. 9. Pommerening A & Stoyan D. (2006) Edge- correction needs in estimating indices of spatial forest structure. Canadian Journal of Forest Research 36(7): 1723-1739. Silviculture JOURNAL OF FORESTRY SCIENCE AND TECHNOLOGY NO. 5 - 2017 52 PHÂN TÍCH ĐẶC ĐIỂM CÂY LÂN CẬN GẦN NHẤT CỦA RỪNG LÁ RỘNG NHIỆT ĐỚI Nguyễn Hồng Hải Trường Đại học Lâm nghiệp TÓM TẮT Cấu trúc không gian là một trong những chỉ tiêu quan trọng để mô tả cấu trúc lâm phần. Chúng tôi áp dụng một phương pháp mới để phân tích định lượng cấu trúc không gian của rừng dựa vào quan hệ của các nhóm cây lân cận nhau. 03 ô tiêu chuẩn 1-ha (100 m x 100 m), được thiết lập trên trạng thái rừng lá rộng thường xanh, được sử dụng để đánh giá các tham số cấu trúc. Tất cả các cây gỗ có đường kính ngang ngực ≥ 6 cm được xác định loài, đo đếm đường kính ngang ngực và vị trí tương đối trong ô tiêu chuẩn. Chúng tôi tính toán và mô tả các tham số cấu trúc như trộn lẫn, ưu thế đường kính và chỉ số đồng góc bằng phần mềm Crancod và Microsoft Excel. Kết quả cho thấy rằng: các loài cây được phân tích đều trộn lẫn mức độ cao với các loài cây khác. Phân tích ưu thế đường kính cho thấy: cây ưu thế ở Hà Tĩnh và Bình Dịnh kém cạnh tranh hơn về đường kính với cây lân cận gần nhất. Tuy vậy, có 03 loài có ưu thế đường kính nên có ưu thế cạnh tranh về không gian dinh dưỡng. Về phân bố không gian, hầu hết các loài cây ưu thế ở 03 ô tiêu chuẩn có phân bố từ dạng đều đến cụm với cây lân cận, tập trung chủ yếu ở dạng đều. Các tham số cấu trúc không gian cung cấp những thông tin trực tiếp và có giá trị về cấu trúc không gian của lâm phần. Những thông tin này có thể được sử dụng cho việc tỉa thưa trong quản lý rừng bền vững, mô hình hóa và phục hồi rừng. Từ khóa: Chỉ số đồng góc, lân cận gần nhất, rừng lá rộng nhiệt đới, trộn lẫn, ưu thế. Received : 08/9/2017 Revised : 30/9/2017 Accepted : 06/10/2017