Table 2 Composition and importance value (IV) index of the tree species in different development stages in an old-growth oak broad-leaved mixed forest

Quercus aliena var. acutiserrata Maxim

Fagaceae

4.79 ± 0.08

31.57 ± 0.18

50.7 ± 0.28

27.13 ± 0.1

Acer caesium subsp. giraldii (Pax) E.Murr

Aceraceae

25.5 ± 0.17

13.75 ± 0.14

4.59 ± 0.16

13.6 ± 0.08

Ulmus propinqua Koidz

Ulmaceae

0.72 ± 0.03

12.04 ± 0.15

20.79 ± 0.25

12.56 ± 0.09

Cerasus polytricha (Koehne) Yü et Li

Rosaceae

9.94 ± 0.11

6.26 ± 0.1

–

5.58 ± 0.05

Symplocos paniculata (Thunb.) Miq.

Symplocaceae

14.47 ± 0.13

0.54 ± 0.04

–

4.81 ± 0.04

Acer ginnala Maxim.

Aceraceae

6.66 ± 0.1

8.46 ± 0.12

1.93 ± 0.06

6.67 ± 0.05

Pinus armandii Franch.

Pinaceae

7 ± 0.11

7.07 ± 0.09

2.62 ± 0.07

6.18 ± 0.06

Crataegus kansuensis Wils

Rosaceae

14.73 ± 0.14

0.39 ± 0.02

–

4.7 ± 0.04

Malus hupehensis (Pamp.) Rehd

Rosaceae

1.21 ± 0.04

5.19 ± 0.1

3.93 ± 0.12

3.73 ± 0.05

Toxicodendron vernicifluum (Stokes) F. A. Barkl.

Anacardiaceae

0.89 ± 0.04

4.55 ± 0.08

0.56 ± 0.03

2.6 ± 0.04

Quercus wutaishanica Blume

Fagaceae

0.23 ± 0.02

2.52 ± 0.07

3.32 ± 0.1

2.95 ± 0.06

Tilia paucicostata Maxim

Tiliaceae

0.88 ± 0.03

0.77 ± 0.03

0.74 ± 0.03

0.98 ± 0.02

Acer cappadocicum Gled

Aceraceae

1.04 ± 0.04

1.13 ± 0.03

–

0.72 ± 0.02

Lindera obtusiloba Bl.

Lauraceae

1.66 ± 0.05

0.83 ± 0.03

–

0.87 ± 0.02

Acer davidii Franch.

Aceraceae

1.17 ± 0.04

1.08 ± 0.03

–

0.79 ± 0.02

Morus alba Linn.

Moraceae

1.48 ± 0.04

0.1 ± 0.01

–

0.62 ± 0.02

Acer tetramerum var. betulifolium (Maxim.) Rehd

Aceraceae

1.22 ± 0.04

–

–

0.36 ± 0.01

Carya cathayensis Sarg

Juglandaceae

0.77 ± 0.03

0.27 ± 0.02

1.53 ± 0.08

0.84 ± 0.03

Kalopanax septemlobus (Thunb.) Koidz

Araliaceae

0.55 ± 0.03

0.71 ± 0.03

–

0.41 ± 0.02

Tilia oliveri Szyszyl

Tiliaceae

–

0.44 ± 0.02

0.48 ± 0.02

0.4 ± 0.01

Meliosma cuneifolia var. glabriuscula Cufod

Sabiaceae

0.48 ± 0.02

–

–

0.16 ± 0.01

Acer elegantulum Fang et P. L. Chiu

Aceraceae

0.3 ± 0.02

0.29 ± 0.02

0.26 ± 0.02

0.27 ± 0.01

Padus racemosa (Linn.) Gilib

Rosaceae

0.43 ± 0.02

0.1 ± 0.01

–

0.14 ± 0.01

Amygdalus persica L.

Rosaceae

0.28 ± 0.02

0.34 ± 0.02

0.32 ± 0.02

0.34 ± 0.02

Ulmus macrocarpa Hance

Ulmaceae

–

0.29 ± 0.02

0.43 ± 0.03

0.31 ± 0.02

Tilia oliveri

Tiliaceae

0.31 ± 0.02

–

–

0.09 ± 0

Betula platyphylla Suk

Betulaceae

–

0.13 ± 0.01

0.41 ± 0.03

0.2 ± 0.01

Corylus heterophylla var. sutchuenensis Franch

Betulaceae

0.18 ± 0.01

–

–

0.08 ± 0.01

Pyrus betulifolia Bge.

Rosaceae

0.22 ± 0.02

–

0.37 ± 0.03

0.22 ± 0.01

Acer henryi Pax

Aceraceae

–

0.42 ± 0.02

–

0.17 ± 0.01

Pyrus xerophila Yü

Rosaceae

0.31 ± 0.02

–

–

0.09 ± 0

Corylus heterophylla Fisch

Betulaceae

0.48 ± 0.02

–

–

0.13 ± 0.01

Spiraea alpina Pall

Rosaceae

0.14 ± 0.01

0.19 ± 0.01

–

0.12 ± 0.01

Rhus potaninii Maxim.

Anacardiaceae

–

0.22 ± 0.02

0.32 ± 0.02

0.18 ± 0.01

Pinus tabulaeformis Carr.

Pinaceae

–

–

0.72 ± 0.04

0.33 ± 0.02

Staphylea holocarpa Hemsl.

Staphyleaceae

0.29 ± 0.02

–

–

0.06 ± 0

Quercus spinosa David ex Franchet

Fagaceae

0.21 ± 0.02

–

–

0.09 ± 0.01

Celtis koraiensis Nakai

Ulmaceae

0.16 ± 0.01

–

–

0.05 ± 0

Sorbus hupehensis Schneid.

Rosaceae

0.11 ± 0.01

–

–

0.04 ± 0

Morus australis Poir.

Moraceae

0.16 ± 0.01

–

–

0.04 ± 0

Acer palmatum Thunb.

Aceraceae

0.17 ± 0.01

–

–

0.04 ± 0

Prunus salicina Linn.

Rosaceae

0.18 ± 0.01

–

–

0.05 ± 0

Carpinus cordata Bl.

Betulaceae

0.15 ± 0.01

–

–

0.03 ± 0

Fraxinus paxiana Lingelsh.

Oleaceae

0.18 ± 0.01

–

–

0.06 ± 0

Acer tsinglingense Fang et Hsieh.

Aceraceae

–

0.12 ± 0.01

–

0.07 ± 0

Sorbus alnifolia (Sieb. et Zucc.) K. Koch

Rosaceae

0.2 ± 0.01

–

–

0.04 ± 0

Amelanchier sinica (Schneid.) Chun

Rosaceae

0.15 ± 0.01

–

–

0.04 ± 0

Fraxinus platypoda Oliver

Oleaceae

–

0.22 ± 0.02

–

0.06 ± 0