3.2. Species composition of adult trees and functional traits
Adult trees accounted for 9955 stems from a total of 167 species (Table A1). No large differences were observed in functional traits among plots for the 95 species sampled. Primary forest tended to have slightly higher values of wood density and seed size than other forests (Fig. 3). The trait values of trees growing in secondary plots and enriched plantation varied greatly.
The PCA of functional traits among species explained 63% of their variations cumulatively up to principal component 2 (PC2; Fig. 4). LMA and leaf toughness had a high correlation (r = 0.99). The correlation between wood density and seed size was also high (r = 0.78). Some species displayed distinguishing characteristics such as thick leaves in Bischofia javanica (29), Mahonia siamensis (107), and Pinus kesiya (129); large leaves in Toona ciliata (158), Alangium chinense (6), and Vernonia volkameriaefolia (164); high LMA and tough leaves in T. gymnanthera (157), Podocarpus neriifolius (132), and C. acuminatissima (39); and dense wood and large seeds ( Fig. 4) in Garcinia cowa (74), Lithocarpus auriculatus (97), and Lithocarpus truncates (99).
The dominant species in primary forest tended to have high values for functional traits such as leaf toughness, wood density, and seed size (Table 2). The dominance of certain species in primary forest also had a positive significant correlation with PC1 and a negative significant correlation with PC3. The correlations in disturbed forests varied greatly with no clear differences between primary and disturbed forests.
3.3. Seedling/sapling composition
Seedling/sapling densities exhibited different patterns among the forest types (Table A2). In primary forest, the seedlings/saplings of C. acuminatissima were present in the highest density, followed by Syzygium claviflorum, Memecylon scutellatum, and Helicia nilagirica ( Table A2). Seedling/sapling densities of Archidendron clypearia, C. acuminatissima, Cryptocarya impressa, and H. nilagirica were highest in secondary forests (including AFV and/or ANV). Seedling/sapling densities of Beilschmiedia gammieana, Castanopsis diversifolia, H. nilagirica, and Maesa ramentacea were highest in enriched plantations (including PMS and/or PPS).
3.4. The factors determining tree regeneration
In total, 30 species with a seedling/sapling density sufficient for statistical analyses (species with ⩾30 stems) were analyzed (Table 3). The factors relating to forest type and structure affected the regeneration of many species (12–15 spp.), while those relating to the physical environment (soil and light) affected a relatively small number of species (8–10 spp.). The distance from conspecific species had an intermediate effect.
Some species were affected by many factors while others were affected by only one or two factors. Seedling/sapling densities of species such as C. acuminatissima, S. claviflorum, B. gammieana, Sarcosperma arboretum, and M. ramentacea were affected by many factors, including the forest structure (BA, tree density and forest types), physical environment (soil and/or light condition), and the distance from conspecific trees. Many of these species had a higher dominance in primary forest ( Table A1). In contrast, C. diversifolia, D. glandulosa, Eurya acuminata, Wendlandia tinctoria, Perilepta auriculata, Trevesia palmata, Pittosporum napaulense, and Glochidion eriocarpum were affected by only one factor ( Table 3), and many of these species had a relatively high dominance in disturbed forests ( Table A1).
The effects of the different physical environment factors varied between species. Many species had positive correlations with soil moisture. Species with a higher dominance in primary forest had both positive and negative correlations with light conditions, suggesting differences in light demand. However, P. napaulense and G. eriocarpum, which had a higher dominance in disturbed forest, correlated positively with light conditions, with no significant correlation with other factors. Most species, with the exception of M. scutellatum and Eriobotrya bengalensis, had positive correlations with distance from conspecific trees.
3.5. Functional traits affecting tree regeneration
Seedling/sapling abundance for all tree species and at all sites had positive and significant correlations with LMA, seed size, wood density, and leaf toughness, and a negative significant correlation with leaf area (Table 4). In the primary forest, seedling/sapling abundances were positively correlated with LMA, seed size, wood density, and leaf toughness, and negatively correlated with leaf area and leaf thickness. In secondary forests, seedling/sapling abundance was negatively correlated with LMA and wood density, and positively correlated with leaf thickness and leaf area. The functional traits related to seedling/sapling abundance in the primary forest were similar to those for all sites, although fewer traits in secondary forests were related to seedling/sapling abundance. This suggests that tree species in primary forest have traits relating to regeneration but their establishment in secondary forest is difficult, although these species were well established in primary forest. In enrichment plantations, most functional traits relating to seedling/sapling abundance were positively correlated with seed size, LMA, leaf area, and leaf toughness, while negative correlations were recorded for wood density and leaf thickness (Table 4). The functional traits relating to tree regeneration in enrichment plantations were intermediate between primary and secondary forest traits.
3.6. Functional traits and the factors determining seedling/sapling distribution
The distance from conspecific adult trees was negatively correlated with seed size, LMA, wood density, and leaf toughness (Table 5). Among the physical environment variables, soil moisture had positive correlations with wood density and leaf toughness, and soil bulk density had a negative correlation with seed size. Relative light density had a negative correlation with wood density. Among the forest structure factors, forest type had a positive correlation with leaf toughness (Table 5, Fig. 5).
The species with less tough leaves, for example, P. napaulense (130), P. auriculata (122), D. glandulosa (59), and Litsea martabarnica (94) tended to grow in areas of low soil moisture (secondary forest) and far away from conspecific adults ( Fig. 5A–C). Species with low wood density, for example, Saurauia roxburghii (142), T. palmata (160), A. clypearia (15), S. arboretum (141), and Actinodaphne henryi (4) tended to grow in areas of low soil moisture and high light intensity, and far away from conspecific adults ( Fig. 5D–F). Species with small seeds (most species with climax species traits and pioneer species traits) tended to grow in areas of high soil bulk density and far away from conspecific adults ( Fig. 5G and H). Species with low LMA, for example, P. auriculata (122), M. ramentacea (105), P. napaulense (130), and E. acuminata (67) tended to grow in the areas far away from conspecific adults ( Fig. 5I). Most of the species with climax species traits (and/or high LMA, strong leaf, dense wood), for example, C. acuminatissima (39), Castanopsis tribuloides (41), C. diversifolia (40), B. gammieana (25), and T. gymnanthera (157) ( Fig. 5A–I) were located in areas with the opposite environmental conditions to the areas where species with pioneer species traits were located (in contrast to the climax species traits and/or thicker leaf and larger leaf traits). However, some species with climax species traits such as D. glandulosa, L. martabarnica, S. arboretum, and A. henryi can grow together with species with pioneer species traits under similar environmental conditions and establishment limitations.
4. Discussion
4.1. The potential for the succession process to provide effective restoration
In secondary forests, only a few seedlings/saplings of the trees that dominate in primary forest were found, even 30 years after the abandonment of cultivation. Although the seedlings/saplings of some species such as C. acuminatissima and S. claviflorum were present on the forest floor of the primary forest, we did not find many seedlings/saplings of these species in the secondary forests ( Table A2). Late-successional species, whose adult trees dominate in primary forest, experience difficulties in establishing their seedlings in disturbed areas ( Favaretto et al., 2011), partly because of the time required to enhance seedling establishment ( Yan et al., 2007 and Spyreas et al., 2012). The restoration of original forest solely by natural regeneration and/or succession will therefore require long time periods.
The seedling/sapling distributions of the species were affected by many factors and varied among species. Many of them were associated with forest types or the developmental stage (BA, density) of forests, together with some environmental factors such as soil moisture and light. The seedlings/sapling density of the species dominating in primary forests tended to be influenced by distance from conspecific trees as well as physical factors. The density of many species was negatively correlated with distance, while only two species had positive correlations, which is suggestive of density dependent mortality (Janzen, 1970, Connell, 1971 and Clark and Clark, 1984). These results imply recruitment limitation by distance from conspecific adult trees. The results for many species suggested positive effects of soil moisture, while responses to the light conditions varied among species. Some species which had a higher dominance in disturbed forests showed a dependence on light conditions, which supports previous studies indicating that light conditions affect many pioneer, light-demanding species (Favaretto et al., 2011).
The use of natural regeneration only will therefore not be
3.2 องค์ประกอบชนิดผู้ใหญ่ต้นและลักษณะงานต้นไม้สำหรับผู้ใหญ่บัญชีสำหรับ 9955 ลำจากทั้งหมด 167 พันธุ์ (ตาราง A1) ความแตกต่างไม่มากถูกสังเกตในลักษณะทำงานระหว่างผืนสำหรับพันธุ์ 95 ความ หลักป่ามีแนวโน้มที่จะ มีค่าสูงขึ้นเล็กน้อยความหนาแน่นของไม้และขนาดเมล็ดมากกว่าป่าอื่น ๆ (Fig. 3) ค่าติดต้นไม้เติบโตในผืนรอง และอุดมไปสวนที่แตกต่างกันมากPCA ของลักษณะการทำงานระหว่างพันธุ์อธิบาย 63% ของรูปแบบของพวกเขาจนถึงส่วนประกอบหลัก 2 (PC2; cumulatively Fig. 4) นึ่ง LMA และใบไม้มีความสัมพันธ์สูง (r = 0.99) นอกจากนี้ยังมีความสัมพันธ์ระหว่างความหนาแน่นของไม้และขนาดเมล็ดสูง (r = 0.78) บางชนิดแสดงลักษณะที่แตกต่างเช่นใบหนา Bischofia javanica (29), ดอยอินทนนท์ Mahonia (107), และ Pinus kesiya (129), ใบไม้ขนาดใหญ่ใน ciliata Toona (158), chinense Alangium (6), และ Vernonia volkameriaefolia (164); LMA สูงและทนใบต. gymnanthera (157), Podocarpus neriifolius (132), และ C. acuminatissima (39); และความหนาแน่นสูงขนาดใหญ่ และไม้เมล็ด (Fig. 4) cowa เนีย (74), Lithocarpus auriculatus (97), และ Lithocarpus ตัดทอน (99)สายพันธุ์หลักป่าหลักมีแนวโน้มที่จะ มีค่าสูงสำหรับลักษณะการทำงานเช่นใบนึ่ง ความหนาแน่นไม้ และขนาดเมล็ด (ตาราง 2) ปกครองบางชนิดในป่าหลักมีความสัมพันธ์อย่างมีนัยสำคัญบวกกับ PC1 และความสัมพันธ์เชิงลบอย่างมีนัยสำคัญกับ PC3 ความสัมพันธ์ในการรบกวนป่าแตกต่างกันอย่าง มีความแตกต่างไม่ชัดเจนระหว่างหลัก และรบกวนป่า3.3. แหล่ง/sapling องค์ประกอบแหล่ง/sapling แน่นจัดแสดงรูปแบบที่แตกต่างกันระหว่างชนิดป่า (ตาราง A2) ในป่าหลัก การกล้าไม้/กล้าไม้และประสงค์ของ C. acuminatissima มีอยู่ในความหนาแน่นสูงสุด ตาม Syzygium claviflorum, Memecylon scutellatum และ Helicia nilagirica (ตาราง A2) แหล่ง/sapling ความหนาแน่นของต้น clypearia, C. acuminatissima, Cryptocarya impressa และ H. nilagirica ได้สูงสุดในป่ารอง (รวม AFV / ANV) แหล่ง/sapling แน่น Beilschmiedia gammieana, Castanopsis diversifolia, H. nilagirica และ ramentacea แม่สาอยู่สูงสุดในไร่อุดม (รวม PMS หรือ PPS)3.4.ปัจจัยที่กำหนดต้นไม้ฟื้นฟูรวม 30 ชนิด โดยมี แหล่ง/sapling หนาแน่นเพียงพอสำหรับการวิเคราะห์ทางสถิติ (พันธุ์ ด้วยลำต้น ⩾30) ได้วิเคราะห์ (ตาราง 3) ปัจจัยที่เกี่ยวข้องกับป่าชนิดและโครงสร้างได้รับผลกระทบฟื้นฟูหลายพันธุ์ (12 – 15 โอ) ขณะที่ เกี่ยวข้องกับสิ่งแวดล้อมทางกายภาพ (ดินและไฟ) ได้รับผลกระทบจำนวนค่อนข้างน้อยพันธุ์ (โอ 8-10) ระยะห่างจากสายพันธุ์ conspecific มีผลปานกลางบางชนิดได้รับผลกระทบจากปัจจัยหลายอย่างในขณะที่คนอื่น ๆ ได้รับผลกระทบจากปัจจัยหนึ่ง หรือสองเท่านั้น ความหนาแน่นของ แหล่ง/sapling พันธุ์เช่น C. acuminatissima, S. claviflorum, gammieana เกิด ตัม Sarcosperma และ ramentacea เมตรได้รับผลกระทบจากปัจจัยหลาย รวมทั้งโครงสร้างป่า (BA ความหนาแน่นของต้นไม้ และป่าชนิด), สิ่งแวดล้อมทางกายภาพ (ดินหรือแสง), และระยะห่างจากต้นไม้ conspecific หลายพันธุ์ได้ครอบงำสูงหลักป่า (ตาราง A1) ในทางตรงกันข้าม C. diversifolia ว้าก D., Eurya acuminata, Wendlandia tinctoria, Perilepta auriculata, Trevesia palmata, Pittosporum napaulense และ Glochidion eriocarpum ได้รับผลกระทบจากปัจจัยเดียวเท่านั้น (ตาราง 3), และหลายพันธุ์มีปกครองค่อนข้างสูงในการรบกวนป่า (ตาราง A1)ผลของปัจจัยสภาพแวดล้อมทางกายภาพที่แตกต่างหลากหลายระหว่างสายพันธุ์ หลายชนิดมีความสัมพันธ์ในเชิงบวกกับความชื้นของดิน พันธุ์ตระหง่านสูงในป่าหลักมีทั้งบวก และลบความสัมพันธ์กับสภาพแสง การแนะนำความแตกต่างในความต้องการแสง อย่างไรก็ตาม P. napaulense และ eriocarpum กรัม ซึ่งได้ครอบงำสูงรบกวนป่า correlated บวกกับสภาพแสง ด้วยไม่มีความสัมพันธ์อย่างมีนัยสำคัญกับปัจจัยอื่น ๆ ด้วย สปีชีส์ส่วนใหญ่ ยกเว้น M. scutellatum และ Eriobotrya bengalensis มีความสัมพันธ์ในเชิงบวกกับระยะห่างจากต้นไม้ conspecific3.5. Functional traits affecting tree regenerationSeedling/sapling abundance for all tree species and at all sites had positive and significant correlations with LMA, seed size, wood density, and leaf toughness, and a negative significant correlation with leaf area (Table 4). In the primary forest, seedling/sapling abundances were positively correlated with LMA, seed size, wood density, and leaf toughness, and negatively correlated with leaf area and leaf thickness. In secondary forests, seedling/sapling abundance was negatively correlated with LMA and wood density, and positively correlated with leaf thickness and leaf area. The functional traits related to seedling/sapling abundance in the primary forest were similar to those for all sites, although fewer traits in secondary forests were related to seedling/sapling abundance. This suggests that tree species in primary forest have traits relating to regeneration but their establishment in secondary forest is difficult, although these species were well established in primary forest. In enrichment plantations, most functional traits relating to seedling/sapling abundance were positively correlated with seed size, LMA, leaf area, and leaf toughness, while negative correlations were recorded for wood density and leaf thickness (Table 4). The functional traits relating to tree regeneration in enrichment plantations were intermediate between primary and secondary forest traits.3.6. Functional traits and the factors determining seedling/sapling distributionThe distance from conspecific adult trees was negatively correlated with seed size, LMA, wood density, and leaf toughness (Table 5). Among the physical environment variables, soil moisture had positive correlations with wood density and leaf toughness, and soil bulk density had a negative correlation with seed size. Relative light density had a negative correlation with wood density. Among the forest structure factors, forest type had a positive correlation with leaf toughness (Table 5, Fig. 5).The species with less tough leaves, for example, P. napaulense (130), P. auriculata (122), D. glandulosa (59), and Litsea martabarnica (94) tended to grow in areas of low soil moisture (secondary forest) and far away from conspecific adults ( Fig. 5A–C). Species with low wood density, for example, Saurauia roxburghii (142), T. palmata (160), A. clypearia (15), S. arboretum (141), and Actinodaphne henryi (4) tended to grow in areas of low soil moisture and high light intensity, and far away from conspecific adults ( Fig. 5D–F). Species with small seeds (most species with climax species traits and pioneer species traits) tended to grow in areas of high soil bulk density and far away from conspecific adults ( Fig. 5G and H). Species with low LMA, for example, P. auriculata (122), M. ramentacea (105), P. napaulense (130), and E. acuminata (67) tended to grow in the areas far away from conspecific adults ( Fig. 5I). Most of the species with climax species traits (and/or high LMA, strong leaf, dense wood), for example, C. acuminatissima (39), Castanopsis tribuloides (41), C. diversifolia (40), B. gammieana (25), and T. gymnanthera (157) ( Fig. 5A–I) were located in areas with the opposite environmental conditions to the areas where species with pioneer species traits were located (in contrast to the climax species traits and/or thicker leaf and larger leaf traits). However, some species with climax species traits such as D. glandulosa, L. martabarnica, S. arboretum, and A. henryi can grow together with species with pioneer species traits under similar environmental conditions and establishment limitations.4. Discussion4.1. The potential for the succession process to provide effective restorationIn secondary forests, only a few seedlings/saplings of the trees that dominate in primary forest were found, even 30 years after the abandonment of cultivation. Although the seedlings/saplings of some species such as C. acuminatissima and S. claviflorum were present on the forest floor of the primary forest, we did not find many seedlings/saplings of these species in the secondary forests ( Table A2). Late-successional species, whose adult trees dominate in primary forest, experience difficulties in establishing their seedlings in disturbed areas ( Favaretto et al., 2011), partly because of the time required to enhance seedling establishment ( Yan et al., 2007 and Spyreas et al., 2012). The restoration of original forest solely by natural regeneration and/or succession will therefore require long time periods.The seedling/sapling distributions of the species were affected by many factors and varied among species. Many of them were associated with forest types or the developmental stage (BA, density) of forests, together with some environmental factors such as soil moisture and light. The seedlings/sapling density of the species dominating in primary forests tended to be influenced by distance from conspecific trees as well as physical factors. The density of many species was negatively correlated with distance, while only two species had positive correlations, which is suggestive of density dependent mortality (Janzen, 1970, Connell, 1971 and Clark and Clark, 1984). These results imply recruitment limitation by distance from conspecific adult trees. The results for many species suggested positive effects of soil moisture, while responses to the light conditions varied among species. Some species which had a higher dominance in disturbed forests showed a dependence on light conditions, which supports previous studies indicating that light conditions affect many pioneer, light-demanding species (Favaretto et al., 2011).The use of natural regeneration only will therefore not be
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