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9 th IUFRO : Uneven - aged Silviculture 201 4 , Birmensdorf ZH, Switzerland

9 th IUFRO : Uneven - aged Silviculture 201 4 , Birmensdorf ZH, Switzerland. Concept and application of uneven-aged silviculture in China: A case study of larch plantations in Northeast China. Zhu JJ, Yan QL, Yu LZ

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9 th IUFRO : Uneven - aged Silviculture 201 4 , Birmensdorf ZH, Switzerland

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  1. 9thIUFRO: Uneven-aged Silviculture2014, Birmensdorf ZH, Switzerland Concept and application of uneven-aged silviculture in China: A case study of larch plantations in Northeast China Zhu JJ, Yan QL, Yu LZ State Key Laboratory of Forest and Soil Ecology, Qingyuan Experimental Station of Forest Ecology, Institute of Applied Ecology, Chinese Academy of Sciences (CAS), China June 19 2014

  2. 2 Concept of uneven-aged silviculture in China • Two stages of China forest management since 1949 Sustainable forest management (after 1998) ★Six large scale plantation and rehabilitation projects ★Strict regulations on forest resources management ★National program: motivations mechanism to conserve forest resources (Li, 2014) Forest management for timber harvest (before 1998) Characterized by excessive cutting, and ignoring the ecological functions of forests Caused problems such as depletion of forest resources, soil erosion and desertification. Especially, flood (Yangtze River and Nenjiang River in 1998), • Uneven-aged silviculture as one of the most conducive measures in improving sustainable forest management has been paid a widespread attention recently

  3. 3 Outline of Presentation • Background • Purpose • Methods and Results • Summary • Acknowledgement Application of uneven-aged silviculture in Northeast China ——A case study of larch plantations

  4. 4 Background • General information of forests in China Total forest area: 208 million ha Forest coverage: ca. 22% ca. 1/3 in Northeast China Plantation forests: 69million ha (1/3 of national forest) 8th (2009–2013) National Forest Inventory Data (State Forestry Administration, 2014)

  5. 5 Background • Forests in Northeast China: Secondary forests (SF) • Playing important roles in conserving water resource & timber production (providing 40% of timber for the country) • Heavy timber harvest in the past century 70% of them were mixed broadleaved secondary forests could not provide timber as before

  6. 6 Background • Forests in Northeast China: Larch plantations (LP) • A large area of secondary forests had been replaced by larch (Larix spp.) plantations in order to meet increasing timber demand since 1950’s • Larch plantations: amount to 2 million ha, around 55% of the planted forests in Northeast China • Forming mosaic plantation/secondary forest landscapes (Mason and Zhu, 2014) Mosaic landscapes Secondary Forest Larch plantation

  7. 7 Background • Compared with the adjacent secondary forests, larch plantations induced decreaseofwater conservation capacity and runoff water acidification • Water-holding capacity in larch plantations decreased by20% • Runoff water pH<5.3 in larch plantations, butpH>6.3in secondary forests (Xu et al., 2012)

  8. 8 Background • Compared with the adjacent secondary forests, larch plantations induced soil fertility decline Major reason caused the problems: mono-species composition of larch plantations  Soil fertility decline, water conservation capacity decrease and acidification • Soil organic matter (SOM) of 40-year larch plantation decreased by 33.5% at 0-5 cm soil layer; by 42.6% at 5-15 cm soil layer (Yang et al., 2010)

  9. 9 Purposes • Try to change species composition by promoting the regeneration of broadleaved species  to convert the larch plantations into uneven-aged mixed forests • For larch plantations surrounded by secondary forests: Find outa suitable distribution pattern of larch plantations planted within the secondary forest ecosystems; for improving regeneration potentials and the possibility inducing LP into uneven-aged mixed forests Determinethe effects of thinning trials on natural regeneration of broadleaved species in larch plantations • For larch plantations not surrounded by secondary forests: Test the feasibility of introducing broadleaved species into the thinned larch plantations by artificial assistance

  10. Shenyang Shenyang 10 Study site • Qingyuan Experimental Station of Forest Ecology, CAS • Precipitation: 810.9 mm • Mean T: 4.7℃ • Max. T: 36.5℃ • Min. T: -37.6℃ • Frost-free P: 130 days • Growing season: late Apr-late Sep • Experimental forests: 1350 ha, composed of mixed broadleaved secondary forests and larch plantations; common and typical in Northeast

  11. 11 Experiment forests • Major forest types in Qingyuan Station Mixed broadleaved Secondary Forests  Secondary forest  Mosaic patterns  Larch plantation (Not surrounded by SF, out of the station) Larch plantation surrounded by secondary forest Secondary forest Larch plantation Larch plantation

  12. Secondary forest Larch plantation Secondary forest Sample belt Sample belt Sample point Larch plantation Sample point 12 Methods—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Larch plantations surrounded by secondary forests • —two distribution patterns of larch plantations within secondary forests Contour Pattern Up-Down Pattern • The Contour Type (CT):SF and LP locating at the same slope position/aspect side by side • The Up-Down Type (UDT):LP locating at the down slope of adjacent SF in the same aspect • Survey plots: 4-paired stands

  13. 13 Methods—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Transects and quadrats setting Contour Type (CT) • 3 transects, each separated by 10m • 11 sampling points, at intervals of 2, 4, 8, 16 and 32 m (1 m2) • 132 sampling quadrats (1 m2) Up-Down Type (UDT)

  14. 14 Methods—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Litter cover and depth, vegetation cover,measured at more than nine random points in each sample plot • Canopy openness, estimated in each month of growing season at the sample plots

  15. 32 32 16 16 8 8 4 4 2 2 0 0 2 2 4 4 16 16 8 8 32 32 15 Results—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Seed density for all tree species in soil Number of seeds m-2 Number of seeds m-2 Boundary Boundary SF LP SF LP Positions Positions The Contour Type stands The Up-Down Type stands • varied as a quadratic curve from SF to LP, and peaked at the boundary of SF/LP • increased linearly from SF to LP; More suitable for seed invasion

  16. 32 16 32 16 8 8 4 4 2 2 0 0 2 2 4 4 16 16 8 8 32 32 16 Results—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Seed density for specific tree species in soil--Fraxinus rhynchophylla Number of seeds m-2 Number of seeds m-2 Boundary Boundary SF LP SF LP Positions Positions The Contour Type stands The Up-Down Type stands • declined logarithmically from SF to LP, and seeds only appeared at 4m in LP • increased as a quadratic curve from SF to LP

  17. 32 16 32 16 8 8 4 4 2 2 0 0 2 2 4 4 16 16 8 8 32 32 17 Results—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Seed density for specific tree species in soil--Acer mono Number of seeds m-2 Number of seeds m-2 SF Boundary Boundary LP SF LP Positions Positions The Contour Type stands The Up-Down Type stands • no significant changes from SF to LP • increased as a quadratic curve from SF to LP

  18. Number of seedlings m-2 Number of seedlings m-2 Boundary Boundary SF SF LP LP 32 32 32 32 16 16 16 16 8 8 8 8 4 4 4 4 2 2 2 2 0 0 0 0 2 2 2 2 4 4 4 4 16 16 16 16 8 8 8 8 32 32 32 32 Positions Positions Number of saplings m-2 Number of saplings m-2 Boundary Boundary SF SF LP LP Positions Positions 18 Results—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Seedling/sapling density for all species in UDT stands • Both seedlings and saplings of broadleaved species established in the larch plantation  formed uneven aged larch-broadleaved forests naturally

  19. 19 Results—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • Relationships between seed/seedling/sapling densities and canopy openness in Up-Down Type stands • Canopy openness is the key factor in affecting regeneration of broadleaved species in larch plantations

  20. 20 Results—Effects of two typical distribution patterns of LP on seed, seedling and sapling banks • From the view of improving regeneration potential and inducing larch plantations into the larch-broadleaved forests, the pattern of Up (SF)-and-Down (LP) may be more feasible for seed invasion and seedling or sapling establishment • Problem: How to promote the regeneration of broadleaved species in larch plantations for Contour Type stands? Thinning, the most important measure, has been applied in improving the regeneration… we examined the effects of thinning on the regeneration of broadleaved species in the larch plantations

  21. 21 Methods—Effects of thinning on forming uneven aged larch-broadleaved forests • Larch plantations surrounded by secondary forests • —two thinned stands of larch plantations (data: before/after thinning) Regime A: Larch plantation was planted in 1965, thinned (10, 20, 30, & 50%) in 2004 with random thinning patterns • Regime A (2004 thinned larch stand): to test the effect of recent thinning on emergence and survival of broadleaved species. Species number and seedling density of all regenerated broadleaved species were investigated soon after thinning in 2004 & 2005

  22. 22 Methods—Effects of thinning on forming uneven aged larch-broadleaved forests Regime B: Larch plantation was planted in 1960, thinned in 1994 with random thinning patterns (20, 30, 40 & 60%) • Regime B (1994 thinned larch stand):to confirm the effect of thinning on establishment of broadleaved species after 10 years of thinning. Seedlings (5-50 cm) and saplings (50-500 cm) of all broadleaved species were recorded in 2005. The sapling height and base diameter were measured in 2005

  23. 23 Methods—Effects of thinning on forming uneven aged larch-broadleaved forests • Broadleaved species regeneration in 2004 thinned stands: species number and seedling density • Number of broadleaved species: 15 species, with abundant species of F. rhynchophylla, A. mono, Phellodendron amurense, Cornus controversa • Seedling density of broadleaved species: 3-11 seedlings m-2 • Seedling density in 2005 > in 2004 • More seedlings in 50% than in 30% (surveyed in 2004 and 2005)

  24. 24 Results—Effects of thinning on forming uneven aged larch-broadleaved forests • Regeneration establishment in 1994 thinned stands • Number of regenerated broadleaved species: 10 with abundant species of A. mono, F. rhynchophylla, F. mandshurica and Quercus mongolica etc. • Density of regenerated broadleaved species: 1-8 seedlings per m2, 2-7 saplings per 10 m2 • Seedling density: 40% > 60%, Sapling density : 60% > 40% Seedlings: 5–50 cm in height Saplings: 50–500 cm in height (surveyed in 2005)

  25. 25 Results—Effects of thinning on forming uneven aged larch-broadleaved forests • Sapling growth in 1994 thinned stands (surveyed in 2005) • Basal diameter and height of saplings in 60% were higher than those in 40%, but they both established. • The regeneration of broadleaved species was successful in 40% and 60% thinning treatments after 11 years.

  26. 26 Results—Effects of thinning on forming uneven aged larch-broadleaved forests • For larch plantations surrounded by secondary forests, it may be feasible to develop uneven-aged larch-broadleaved forests through thinning; the thinning intensity should be large enough to satisfy the survival and growth of seedlings or saplings • For larch plantations not surrounded by secondary forests, whether can we promote the regeneration of broadleaved species by artificial assistance?

  27. Thinning intensity Stem density (trees ha-1) Canopy openness 0 (CK) 900 11±1% 25% 675 21±1% 50% 450 25±1% 100% 0 100% 27 Methods—Seed germination & seedling growth of introduced broadleaved species in LP stands • Larch plantations not surrounded by secondary forests • —nine stands in a thinned larch plantation (10.3 ha, 20yrs) in 2011 Dominant broadleaved species:Fraxinus mandshurica & Juglans mandshurica

  28. pressed half-way into the soil (ST) on top of the litter cover (LT) under 1cm soil with 4cm litter cover (LS1) under 1cm soil without litter cover (S1) beneath the litter of 4 cm depth (LS) 28 Methods—Seed germination & seedling growth of introduced broadleaved species in LP stands • Seed germination in thinned larch plantations not surrounded by secondary forests (Oct 2011-Oct 2013) • Treatments:Fraxinus & Juglans seeds were collected and directly seeded at five positions by simulating the states of seeds after falling off in thinned stands in autumn (2011) • Germination, seedling emergence and survival were monitored after seeding (50 seeds×3 replications)

  29. 25% CK 100% 50% 29 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • Seed germination—J. mandshurica • Highest: 25% & 50% thinned stands; S1/LS1: 19.2±2.2%/ 21.3±2.2% • Lowest: 100% & CK; LT: 5.4±2.2% Seed germination rate (%) Seed germination rate (%) ST: pressed half-way into soil; LT: on top of litter; LS: beneath litter; S1: under soil without litter cover; LS1: under soil with litter coverage

  30. Seed germination rate (%) 30 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • Seed germination—F. mandshurica • Highest: 50% thinned stands, next CK, 25%; S1/LS1: 34.7±2.0%/ 37.7±2.3% • Lowest: 100% (17.7±2.5%), ST/LT: 20.3±2.3%/ 22.0±2.4% 25% CK 100% 50% ST: pressed half-way into soil; LT: on top of litter; LS: beneath litter; S1: under soil without litter cover; LS1: under soil with litter coverage

  31. 31 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • Seedling emergence and survival F. mandshurica J. mandshurica • J. mandshurica: lower survival rates in general, less than 4%; Control plot exhibited the lowest survival; The highest: 25%/S1 10.7%, 50%/LS1: 10.3% • F. mandshurica: 14% survival in average; The highest: 50%/S1 23%

  32. 32 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • For larch plantations not surrounded by secondary forests, 25% (675 stems per hectare) and 50% thinning (450 stems per hectare), and under soil seeding are necessary for the germination and emergence of Juglans and Fraxinus. But, the survival of the seedlings after germination was very poor. • Problem: Is it possible to plant the seedlings of broadleaved species in the thinned larch plantations to promote the regeneration of broadleaved species?

  33. 0.5cm 33 Methods—Seed germination & seedling growth of introduced broadleaved species in LP stands • Planting seedlings in thinned larch plantations not surrounded by secondary forests (May-Oct 2013) • Treatments: 1-year & 2-year FM & JM seedlings were planted randomly in each stand in spring (50 seedlings×3 replications) 0.5cm 1-yr-old 2-yr-old J. Mandshurica F. mandshurica • Seedling survival was monitored at interval of one month from May to Oct. • Seedling harvest was conducted in autumn. Height, collar diameter, root length, biomass, leaf δ13C, non-structural carbon content were measured

  34. 34 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • Seedling survival • Lowest: at 100% thinned stands (33% for F. mandshurica; 58% for J. mandshurica) • Highest: CK, 25% & 50% thinning stands (45% for F. mandshurica, 86% for J. mandshurica)

  35. 1-yr-old δ13C (‰) 2-yr-old 35 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • Water use efficiency Light regime at 100 cm Soil water content in 0-20 cm • It may be caused by the water stress because of lower soil water contents and higher light intensities in the clear-cutting plot • δ13C of leaves: carbon isotope was the highest in seedling leaves of clear-cutting plot, which confirmed the deduction

  36. 36 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • Seedling growth • Height/diameter:no significant differences between thinning intensities for both aged seedlings (short observed period) • Growth trend: diameter growth of both species showed the increasing trend with the increase of thinning intensities

  37. 37 Results—Seed germination & seedling growth of introduced broadleaved species in LP stands • For the larch plantations not surrounded by secondary forests, artificial assistance (thinning, and planting seedlings of dominant broadleaved species) has potential to improve the regeneration of broadleaved species in the larch plantations. • Further observations are being carried out…

  38. 38 Summary • For larch plantations (LP) surrounded by secondary forests (SF), the natural regeneration of broadleaved species have established with Up secondary forest and Down larch plantation pattern. Therefore, it is feasible for the Up-Down pattern larch plantations to develop the uneven-aged larch-broadleaved forests • For LP surrounded by SF, when they located side by side, it is likely to form an uneven-aged larch-broadleaved forest by thinning with appropriate canopy openness • For LP not surrounded by SF, artificial assistance, including thinning larch plantations and planting broadleaved species seedlings, has potential to promote the regeneration of broadleaved species in the larch plantations. But, the further observations are needed

  39. Questions & Comments Qingyuan Experimental Station of Forest Ecology, CAS • Acknowledgement • National Basic Research Program of China (973) (2012CB416900) & National Natural Science Foundation of China (31330016) provided the financial support • The member in Research Group of Ecology & Management of Secondary Forests, IAE, CAS gave the helps in field observations and valuable suggestions Thank you for your attention!

  40. 40 References • Mason WL, Zhu JJ. 2014. Silviculture of Planted Forests Managed for Multi-functional Objectives: Lessons from Chinese and British Experiences. In Fenning T (ed.),Challenges and Opportunities for the World’s Forests in the 21st Century. pp. 37-54. Springer, New York. • Yan QL, Zhu JJ, Gang Q. 2013. Comparison of spatial patterns of soil seed banks between larch plantations and adjacent secondary forests in Northeast China: implication for spatial distribution mode of larch plantations. Trees-Structure and Function, 27: 1747-1754. • Yang K, Zhu JJ, Yan QL, Sun OJX. 2010. Changes in soil P chemistry as affected by conversion of natural secondary forests to larch plantations. Forest Ecology and Management, 260: 422–428. • Yang K, Shi W, Zhu JJ. 2013. The impact of secondary forests conversion into larch plantations on soil chemical and microbiological properties. Plant and Soil, 368: 535–546. • Zhang M, Zhu JJ, Li MC, Zhang GQ, Yan QL. 2013. Different light acclimation strategies of two coexisting tree species seedlings in a temperate secondary forest along five natural light levels. Forest Ecology and Management, 306: 234–242 • Zhu JJ, Liu ZG, Wang HX, Yan QL, et al. 2008. Effects of site preparation on emergence and early establishment of Larix olgensis in montane regions of northeastern China. New Forests, 36: 247-260. • Zhu JJ, Yang K, Yan QL, Liu ZG, Yu LZ, Wang HX. 2010. Feasibility of implementing thinning in even-aged Larix olgensis plantations to develop uneven-aged larch–broadleaved mixed forests. Journal of Forest Research, 15: 71-80.

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