Journal of Ecology Compensatory effects between

VOLUME 3, NUMBER 3, PAGES 183–189 Pinus massoniana and broadleaved SEPTEMBER 2010 doi: 10.1093/jpe/rtq020 species Advanced Access published on 4 August 2010 1,2,3 1 1,2 1 1, available online at Qian Li ,YuLiang, Bo Tong , Xiaojun Du and Keping Ma * www.jpe.oxfordjournals.org 1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, 2

Graduate School of Chinese Academy of Sciences, Beijing 100049, China Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021 3 College of Life Science and Technology, Central South University of and Technology, Changsha 410004, China *Correspondence address. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China. Tel: +86-10-6283-6223; Fax: +86-10-8259-9518; E-mail: [email protected]

Abstract

Aims P. massoniana. Pinus massoniana had competitive effects on Litho- Evaluation of the interaction intensity between Masson (Pinus carpus glaber, Cyclobalanopsis glauca and Elaeocarpus japonicus. massoniana) and broadleaved will facilitate selecting tree com- Significantly negative relations were found between biomass of binations suitable for reforestation in abandoned sites in subtropical P. massoniana and the broadleaved trees in the third year of the ex- areas. periment, and the compensatory effects between P. massoniana and the broadleaved trees may be involved in stability maintenance in the Methods multi-species forests in the subtropical area. The results of homoge- Pinus massoniana and seven broadleaved trees species were grown neity test of variances also showed that the biomass per pot in the either in monoculture or in two-species mixture. Biomass of tree spe- mixture had significantly lower variances than that in the monocul- cies was measured and inter-specific interactions were estimated us- ture, suggesting that total biomass is more stable in the mixture than ing log response ratio. Test of homogeneity of variances was the monoculture. performed to compare the stability of biomass in the monoculture of the broadleaved trees with that in the mixture. Keywords: competitive effects d plant–plant interactions Important Findings d facilitative effects d subtropical forest Our results showed that the direction and intensity of interactions Received: 6 May 2010 Revised: 16 June 2010 Accepted: 16 June between P. massoniana and the broadleaved trees varied from year 2010 to year and the identity of the broadleaved species. Facilitative inter- actions were found between Camellia oleifera, Rhus chinensis and

INTRODUCTION ative effects of neighbor may result from inter-specific competition for nutrients, water or light. In contrast, the accu- Inter-specific interactions between plants are the essential mulation of nutrients, provision of shade, amelioration of dis- drivers in structuring plant communities (Callaway and turbance or protection from herbivores by some species may Walker 1997; Fowler 2003). The nature of plant–plant inter- lead to facilitative effects of neighbor plants (Fernando et al. actions is diverse, with the potential net outcome of these 2004). interactions ranging from positive to negative (Goldberg Evergreen broad-leaved forests formerly covered ;25% 1990). Both positive and negative effects may exist between area in China (Wang et al. 2007). However, most of the sub- two plant species and the net effect of a plant–plant interaction tropical forests have been destroyed by clear logging in the depends on the balance of negative and positive effects 1950’s and the 1960’s due to policy and economic reasons. (Callaway and Walker 1997; Chapin et al. 1994; Maestre In recent years, China has made great efforts in reforestation et al. 2004; Maestre et al. 2009; Niu and Wan 2008). The neg- and ecological restoration in the disturbed areas. It has been

Ó The Author 2010. Published by Oxford University Press on behalf of the Institute of Botany, Chinese Academy of Sciences and the Botanical Society of China. All rights reserved. For permissions, please email: [email protected] 184 Journal of Plant Ecology a long-term debate in forestry of which kinds of forests, pure or Experimental design and sampling mixed species, should be used in reforestation (Berkowitz et al. One species, P. massoniana, and seven broadleaved tree 1995; Brenton and Facelli 2005; Knoke et al. 2008). Owing to species, i.e. Quercus variabilis (Fagaceae), Q. glandulifera (Faga- the advantages of mixed-species forests in fireproofing, path- ceae), Cyclobalanopsis glauca (Fagaceae), Lithocarpus glaber (Faga- ogen resistance and higher productivity in many countries in ceae), Rhus chinensis (), Elaeocarpus japonicus the world, it is currently a major objective of forest manage- (Elaeocarpaceae) and Camellia oleifera (Theaceae), were used ment and policy to convert mono-species coniferous forests in- in our study. Quercus variabilis, Q. glandulifera and R. chinensis to multi-species forests (Baumgarten and von Teuffel 2005; are deciduous, and C. glauca, L. glaber, E. japonicus and C. oleifera Fritz 2006; Knoke et al. 2008). How to select suitable plant spe- are evergreen trees. Plant were sterilized with a 0.1% cies or species combinations from many candidate plant spe- hypochloric acid solution for 3 min and sown in March cies is essential for the success of reforestation in terms of 2003. Tree seedlings were either grown as monoculture or biomass accumulation and ecosystem stability. two-species mixture of P. massoniana and one broadleaved Pinus massoniana (Masson pine) is a tree species commonly species in pots (38 cm in diameter and 40 cm in height). Four Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021 used in reforestation of disturbed sites in subtropical area of individuals of single species were kept in each pot as the mono- China, and has been documented to have positive effects on culture treatment and two individuals of each species were kept soil and water conservation in forest plantations (Wang et al. in each pot as the mixture treatment. Fifteen replicates per spe- 2007). Similar to the situation in other countries, mixed for- cies combination were used in the experiment, resulting in a to- ests are more and more popular in reforestation in China. tal of 225 pots (15 species combinations 3 15 replicates). During However, lack of information on the interactions between the experiment duration, the pots were kept under conditions pine and broadleaved tree species makes it difficult to select with ambient temperature and precipitation. suitable species combinations in the establishment of mixed Plants were harvested in the end of October in 2003, 2004 forests. Evaluation on the performances of both pine and and 2005. Three replicates of each species combination were broadleaved species in species mixtures will be therefore harvested in each year. and shoots were separated for helpful in selecting suitable species combinations in refores- all seedlings, oven dried at 70°C for 48 h and weighed. tation (Wang et al. 2002; White et al. 1999; Zavala and Zea 2004). Statistical analyses In the present study, P. massoniana and seven common Shoot, and total plant biomass of P. massoniana and broadleaved trees species of the local forest were grown in broadleaved trees in the mixture were compared with those monoculture or two-species mixture. Growth of tree species in the monoculture using Student’s t-test in SPSS for win- were determined and inter-specific interactions between dows (version 13.0, SPSS Inc., USA). We used log response P. massoniana and the broadleaved trees were measured. ratio (lnRR) to evaluate the response of one species to the The specific objectives of this study are (i) to evaluate the in- presence of the other. LnRR = ln(Xmix/Xmono), where X is teraction intensity between P. massoniana and the broadleaved an estimation of plant performance in the presence (mix) trees and (ii) to select species combinations suitable for refor- or in the absence (mono) of neighbors (Oksanen et al. estation in the abandoned sites in subtropical area. 2006; Weigelt and Jolliffe 2003). Positive values of lnRR in- dicate facilitative effects of heterospecific neighbor species on target species and negative values indicate competitive inhi- MATERIALS AND METHODS bition of neighbor species on target species. Test of homoge- neity of variances was performed using Levene statistic in Site descriptions SPSS for windows (version 13.0, SPSS Inc.) to compare the # The experiment was conducted in Dujiangyan city (30°45 to stability of biomass in the monoculture of broadleaved trees # # # 31°22 N, 103°25 to 103°47 E), Sichuan Province, China. The with that in the mixture. Correlation between biomass of site has a mean annual precipitation of 1 244 mm, a mean an- P. massoniana and broadleaved trees were analyzed by linear nual temperature of 15.2°C and an altitude of ;780 m above regression using SPSS for windows. the sea level. The typical vegetation of this region is subtropical broad-leaved evergreen forest and the dominant tree species RESULTS belong to families of Fagaceae, Lauraceae, Theaceae, Magno- liaceae and (Du et al. 2007). Soil was taken from an Responses of P. massoniana to broadleaved trees abandoned site where clear-cut logging was carried out at the In the first year, no broad-leaved trees showed significantly end of 1950s and early of 1960s (sees the descriptions in negative effects on seedling growth of P. massoniana Du et al. 2008). The abandoned site was dominated by a variety (Fig. 1a). Two species, L. glaber and R. chinensis, showed signif- of annual and perennial ferns, grasses, herbs and some shrubs icantly facilitative effects on shoot biomass of P. massoniana. (Liang et al. 2004). Soil organic matter (SOM) and nitrogen A significantly higher root biomass of P. massoniana was also contents of the soil are 1.04 6 0.17% (mean 6 1 SE) and found in the P. massoniana–R. chinensis combination as com-

0.14 6 0.02%, respectively. Soil pH value (H2O) is 5.19 6 0.19. pared with the monoculture of Masson pine. Li et al. | Compensatory effects between trees 185

In 2004, the presence of C. oleifera as neighbor showed Responses of broadleaved trees to P. massoniana significantly facilitative effects on seedling performance of In 2003, the presence of P. massoniana showed significantly fa- P. massoniana (P < 0.001). As a result of strongly positive in- cilitative effects on shoot biomass of Q. glandulifera (P < 0.01) ter-specific interaction, dry weight of shoot, root and total and root biomass of C. glauca (Fig. 2a). In 2004, P. massoniana plant of P. massoniana seedlings in the P. massoniana–C. oleifera showed significantly competitive effects on shoot biomass of combination were 2.89, 2.48 and 2.79 times of those in the L. glaber and C. glauca as well as root biomass of E. japonicus P. massoniana monoculture, respectively (Fig. 1b). Enhance- (Fig. 2b). In 2005, dry biomass of L. glaber and E. japonicus ment of shoot biomass of P. massoniana was also found in its was significantly reduced as a result of inter-specific competi- combination with R. chinensis (P < 0.05). In contrast, Q. varia- tion from P. massoniana (P < 0.05) (Fig. 2c). bilis and L. glaber had significant competitive effects on shoot biomass accumulation of P. massoniana. LnRR of broadleaved trees and P. massoniana In 2005, the presence of the seven broadleaved trees showed LnRR of the broadleaved trees to P. massoniana shifted greatly no effect on biomass accumulation of P. massoniana seedlings, Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021 in different years (Fig. 3). In the first year of the experiment, except for a significantly negative effect of Q. variabilis on shoot five of the seven broadleaved species showed positive or neu- biomass and a significantly positive effect of C. glauca on root tral responses to the presence of P. massoniana. However, lnRR biomass of P. massoniana (Fig. 1c). of three species, C. glauca, E. japonicus and L. glaber changed from positive to negative in 2004. In the last year of the exper- 0.6 iment, five of the seven broadleaved trees showed negative (a) 0.4 *** * 4 (a) 0.2 # 2 ** 0 0 # * # 2 # 0.2 # )

g * 4 (

t 0.4

n #

a 6 l

p 12

r (b) *** 8 ) e 10 g p (

s 8 t

s ** 15 n a a (b) 6 l m p 10

r y 4 r e 5 # ** # d * p 2 *** a s ** s 0 * n 0 a # a i

n m 5 * 2 #

o y s 4 r s ** d 10

a g

m n . i 15 30 l P (c) d 20 e

20 e S 40 (c) 10 * 30 20 0 10 * # * 10 Root * 0 10 # Shoot # 20 20 # Pm Qg Qv Lg Cg Rc Ej Co 30 monoculture mixculture Neighbor plants 40 50 Qg Qv Lg Cg Rc Ej Co Figure 1: changes in shoot and root dry biomass per plant (mean 6 Broadleaved species standard error) of Pinus massoniana grown in the monoculture and grown with the broad-leaved species in the two-species mixture. #, *, ** and *** indicate P < 0.1, P < 0.05, P < 0.01 and P < 0.001, respec- Figure 2: shoot and root dry biomass per plant (mean 6 standard er- tively. (a), (b) and (c) represent 3 years of experiment duration 2003, ror) of the broad-leaved species grown in the monoculture and in the 2004 and 2005, respectively. Abbreviations for species names: Pm two-species mixture with Pinus massoniana. #, *, ** and *** indicate P < (Pinus massoniana), Qv (Quercus variabilis), Qg (Quercus glandulifera), 0.1, P < 0.05, P < 0.01 and P < 0.001, respectively. (a), (b) and (c) Lg (Lithocarpus glaber), Cg (Cyclobalanopsis glauca), Rc (Rhus chinensis), represent 3 years of experiment duration 2003, 2004 and 2005, Ej (Elaeocarpus japonicus) and Co (Camellia oleifera). respectively. 186 Journal of Plant Ecology responses to the presence of P. massoniana. In contrast, R. chi- Stability in biomass of the monoculture and the nensis showed a different trend with a negative response to the mixture presence of P. massoniana in the first year and a positive re- The results of homogeneity test of variances showed that sponse in the last year. shoot, root and total biomass per pot had significantly lower LnRR of P. massoniana to the broadleaved trees was different variances in the mixture than in monoculture, with the excep- from those of broadleaved species to P. massoniana. LnRR tion of the variance of shoot biomass in the year of 2005 tended to change from negative at the beginning of the exper- (Table 1). These results suggest that the ‘two-species commu- iment to positive at the end of the experiment in 2005. nities’ containing one pine and one broadleaved species are more stable than the monoculture in term of biomass. Relationship between biomass of P. massoniana and the broadleaved trees in the mixture In 2003, no correlations were found between biomass of DISCUSSION

P. massoniana and broadleaved trees. In 2004, significantly neg- Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021 ative correlations were found between root biomass as well as Understanding the mechanisms maintaining diversity in total biomass of P. massoniana and those of broadleaved trees (P < species-rich communities remains a major challenge for ecol- 0.05, Fig. 4). In 2005, biomass of P. massoniana also showed neg- ogists. Increasing evidence suggests that negative density ative dependence upon that of broadleaved trees (P = 0.001). dependence, particularly at early life stages, is widespread in

Figure 3: lnRR of the broadleaved species to Pinus massoniana (A1, A2, A3) and P. massoniana to the broadleaved species (B1, B2, B3). Abbrevia- tions for species names are the same as in Figure 1. Li et al. | Compensatory effects between trees 187 Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021

Figure 4: relationship between biomass of Pinus massoniana and the broadleaved trees in each pot of mixture. plant communities (Comita and Hubbell 2009). Density of effects of P. massoniana on L. glaber, C. glauca and E. japonicus conspecific and heterospecific neighbors may significantly af- were also observed. These results suggested that plant spe- fect the survival of species in the seedling bank of a natural cies may have different response strategies to different forest (Comita and Hubbell 2009; Hubbell et al. 2001; Peters neighbors. 2003). Given that individuals can spend a considerable portion of their life in the seedling bank (Hubbell 1998), the inter- Inter-specific interactions changed with time specific interaction of seedlings may play an important role Better understanding of the direction and strength of inter- in coexistence of species and diversity maintenance in natural action over the life history stages of plants are important to forests. assess the influence of plant interaction on community com- position (e.g. Goldberg et al. 2001; Lortie and Turkington Different interaction modes between species 2008; Miriti 2006; Schiffers and Tielborger 2006; Shilo-Volin Competitive interactions are integral to theories of species co- et al. 2005). Our results indicated that the direction and in- existence in plant community, but plant–plant facilitation is tensity of interaction between P. massoniana and the broad- generally omitted from coexistence models (e.g. Travis et al. leaved trees varied from year to year. The increased 2005, 2006; Vellend 2008). In recent year, it has well been competitive effects of P. massoniana on most broadleaved tree documented that different types of interactions, from compet- species in the third year of the experiment might be a result of itive to facilitative, might exist between plant species (Maestre increased competition in limited pot space. We also found the et al. 2004, 2009; Niu and Wan 2008; Palmer et al. 2003; facilitative or neutral effects of P. massoniana on performances Passarge et al. 2006). Our results indicate that interactions be- of C. oleifera and R. chinensis after 3 years of the pot experi- tween P. massoniana and different broadleaved tree species ment, which may be helpful in selection of broadleaved spe- vary with identity of the broadleaved tree species. cies in establishment of a mixed-species forest. Because In our study, facilitative interactions were found between C. oleifera and R. chinensis are small trees or shrub species C. oleifera, R. chinensis and P. massoniana, while competitive and P. massoniana is large trees, the functional compensatory 188 Journal of Plant Ecology

Table 1: test of homogeneity of variances of shoot, root and total biomass (dry weight) per pot of monoculture and mixturea FUNDING National Natural Science Foundation of China Shoot Root Biomass (30710103907); State Key Basic Research and Development Mono Mix Mono Mix Mono Mix Plan of China (2002CB111505). 2003 coefficient of variation 0.801 0.499 1.157 0.957 1.029 0.748 Levene statistic 14.223** 25.214*** 24.014*** ACKNOWLEDGEMENTS

2004 We thank Dr Bernhard Schmid for his valuable suggestions on design coefficient of variation 0.784 0.395 1.065 0.799 0.806 0.421 of the experiment. We are grateful to Dr Shiqiang Wan, Dr Jinsheng He Levene statistic 6.542* 9.714** 21.396*** and three anonymous reviewers for their helpful suggestions on an early version of the manuscript. 2005 Conflict of interest statement. None declared. Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021 coefficient of variation 0.810 0.402 0.901 0.673 0.817 0.328 Levene statistic 2.037 8.111** 11.806** a *, ** and *** indicate significant differences in variances at P < 0.05, REFERENCES P < 0.01 and P < 0.001 levels, respectively. Bai YF, Han XG, Wu JG, et al. (2004) Ecosystem stability and compen- satory effects in the Inner Mongolia grassland. Nature 431:181–4. may partially explain the positive response of these two spe- Baumgarten M, von Teuffel K (2005) Nachhaltige Waldwirtschaft cies to P. massoniana. The alleviated competitive effects of in Deutschland. In von Teuffel K, et al. (eds). Waldumbau. Berlin, these two broadleaved trees to P. massoniana in the experi- Germany: Springer, 1–10. mental duration might be due to the improved soil moisture Berkowitz AR, Canham CD, Kelly VR (1995) Competition vs. facilita- under higher coverage in the third year. Pinus massoniana tion of tree seedling growth and survival in early successional com- munities. Ecology 76:1156–68. could also share many mycorrhizal fungi with species of Fagaceae (Q Ding, Y Liang, K Ma personal communication; Brenton ML, Facelli JM (2005) Effects of competition, resource avail- ability and invertebrates on tree seedling establishment. J Ecol Perry et al. 1989), which could also alleviate the competition 93:968–77. between P. massoniana and the four ectomycorrhizal species, Callaway RM, Walker LR (1997) Competition and facilitation: a syn- i.e. Q. variabilis, Q. glandulifera, L. glaber and C. glauca in the thetic approach to interactions in plant communities. Ecology family of Fagaceae. 78:1958–65. Chapin FS, Walker LR, Fastie CL, et al. (1994) Mechanisms of primary Compensatory effects and the productivity stability succession following deglaciation at Glacier Bay, Alaska. Ecol Monogr Ecosystem stability is also an important aspect in sustainable 64:149–75. reforestation actions. For sustainable reforestation actions in Comita LS, Hubbell SP (2009) Local neighborhood and species’ shade fire-prone landscapes, and re-sprouting broad-leaved tolerance influence survival in a diverse seedling bank. Ecology species should be combined to take advantage of the comple- 90:328–34. mentary features of both species groups, i.e. the faster growth Du X, Liu C, Yu X, et al. (2008) Effects of shading on early growth of Cyclobalanopsis glauca (Fagaceae) in subtropical abandoned fields: of pines and the high fire resilience of broadleaved species Implications for vegetation restoration. Acta Oecologica 33:154–161. (Pausas et al. 2004). Du XJ, Guo QF, Gao XM, et al. (2007) rain, soil seed bank, seed Compensatory effects between plant species are usually loss and regeneration of Castanopsis fargesii (Fagaceae) in a subtrop- considered as a contribution to the stability of ecosystems. ical evergreen broad-leaved forest. For Ecol Manage 238:212–9. Bai et al. (2004) have documented that negative relations Fowler N (2003) The role of competition in plant communities in arid existed between biomass of main plant functional groups, and semiarid regions. Ann Rev Ecol Syst 17:89–110. which suggests that the compensatory effects between plant Fritz P (ed.) (2006) O¨ kologischer waldumbau in Deutschland—Fragen, factional groups may play an important role in stability Antworten, Perspektiven. Mu¨ nchen, Germany: Oekom. maintenance of ecosystem. Our results show that compen- Goldberg DE (1990) Components of resource competition in plant satory effects existed between P. massoniana and some of communities. In Grace J, Tilman D (eds). Perspectives in plant com- the broadleaved trees. Since all the trees we used are com- petition. New York: Academic Press, 27–49. mon species in natural subtropical forests, such compensa- Goldberg DE, Turkington R, Olsvig-Whittaker L, et al. (2001) Density tory effects may be helpful in stability maintenance of dependence in an annual plant community: variation among life these forests. That is, the decrease in biomass of pine or history stages. Ecol Monogr 71:423–46. broadleaved trees can be compensated by the other; thus, Hubbell SP (1998) The maintenance of diversity in a neotropical tree the biomass or productivity of the whole system would be community: conceptual issues, current evidence, and challenges relatively stable. ahead. In Dallmeir F, Cominsky JA (eds). Forest Biodiversity Research, Li et al. | Compensatory effects between trees 189

Monitoring and Modeling: Conceptual Background and Old World Case Perry DA, Margolis H, Choquette C, et al. (1989) Ectomycorrhizal me- Studies. Pearl River, NY: Parthenon, 17–44. diation of competition between coniferous tree species. New Phytol Hubbell SP, Ahumada JA, Condit R, et al. (2001) Local neighborhood 112:501–11. effects on long-term survival of individual trees in a neotropical for- Peters HA (2003) Neighbour-regulated mortality: the influence of pos- est. Ecol Res 16:859–75. itive and negative density dependence on tree populations in Knoke T, Ammer C, Stimm B, et al. (2008) Admixing broadleaved to species-rich tropical forests. Ecol Lett 6:757–65. coniferous tree species: a review on yield, ecological stability and Sammul M, Oksanen L, Magi M (2006) Regional effects on competi- economics. Eur J For Res 127:89–101. tion-productivity relationship: a set of field experiments in two dis- Liang Y, Guo LD, Ma KP (2004) Genetic structure of a population of the tant regions. Oikos 112:138–48. ectomycorrhizal fungus Russula vinosa in subtropical woodlands in Schiffers K, Tielborger K (2006) Ontogenetic shifts in interactions southwest China. Mycorrhiza 14:235–40. among annual plants. J Ecol 94:336–41. Lortie CJ, Turkington R (2008) Species-specific positive effects in an Shilo-Volin H, Novoplansky A, Goldberg DE, et al. (2005) Density reg- annual plant community. Oikos 117:1511–21. ulation in annual plant communities under variable resource levels.

Maestre FT, Callaway RM, Valladares F, et al. (2009) Refining the Oikos 108:241–52. Downloaded from https://academic.oup.com/jpe/article/3/3/183/960486 by guest on 30 September 2021 stress-gradient hypothesis for competition and facilitation in plant Travis JMJ, Brooker RW, Clark EJ, et al. (2006) The distribution of communities. J Ecol 97:199–205. positive and negative species interactions across environmental Maestre FT, Cortina J, Bautista S (2004) Mechanisms underlying the gradients on a dual-lattice model. J Theor Biol 241:896–902. interaction between Pinus halepensis and the native late-succes- Travis JMJ, Brooker RW, Dytham C, et al. (2005) The interplay of pos- sional shrub Pistacia lentiscus in a semi-arid plantation. Ecography itive and negative species interactions across an environmental gra- 27:776–86. dient: insights from an individual-based simulation model. Biol Lett Miriti MN (2006) Ontogenetic shift from facilitation to competition in 1:5–8. a desert shrub. J Ecol 94:973–9. Vellend M (2008) Effects of diversity on diversity: consequences of Niu SL, Wan SQ (2008) Warming changes species competitive hierar- competition and facilitation. Oikos 117:1075–85. chy in a temperate steppe of northern China. JPlantEcol1: Wang XH, Kent M, Fang XF (2007) Evergreen broad-leaved forest in 103–10. Eastern China: its ecology and conservation and the importance of Oksanen L, Sammul M, Magi M (2006) On the indices of plant-plant resprouting in forest restoration. For Ecol Manage 245:76–87. competition and their pitfalls. Oikos 112:149–55. Wang ZL, Wang FZ, Chen S, et al. (2002) Competition and coexistence Palmer TM, Stanton ML, Young TP (2003) Competition and coexis- in regional habitats. Am Nat 159:498–508. tence: exploring mechanisms that restrict and maintain diversity Weigelt A, Jolliffe P (2003) Indices of plant competition. J Ecol within mutualist guilds. Am Nat 162:563–79. 91:707–20. Passarge J, Hol S, Escher M, et al. (2006) Competition for nutrients and White AS, Witham JW, Hunter ML Jr, et al. (1999) Relationship be- light: stable coexistence, alternative stable states, or competitive ex- tween plant species richness and biomass in a coastal Maine Quer- clusion? Ecol Monogr 76:57–72. cus-Pinus forest. J Veg Sci 10:755–62. Pausas JG, Blade C, Valdecantos A, et al. (2004) Pines and in the Zavala MA, Zea E (2004) Mechanisms maintaining biodiversity in restoration of mediterranean landscapes of Spain: new perspectives Mediterranean pine- forests: insights from a spatial simulation for an old practice—a review. Plant Ecol 171:209–20. model. Plant Ecol 171:197–207.