Short Communication
Vegetation Changes over Seven Years after Clear-cuttingof Bamboo Culms
2018 Volume 24 Issue 1 Pages 1-9
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2018 Volume 24 Issue 1 Pages 1-9
The area of bamboo groves in southwest Japan, comprised mainly of Phyllostachys pubescens, has recently increased. An alternative to these abandoned bamboo groves is their transition to broad-leaved forests. The vegetation transition to broad-leaved forests observed several years after clear-cutting are very important. We investigated the change in species composition after repeating P. pubescens culm cutting. We established four quadrate plots (10 × 10 m): clear-cutting bamboo culms, thinning bamboo culms, and two control sites. Regenerated bamboo culms appeared the next spring after clear-cutting. We concluded that in absence of continuous culm cutting, bamboo recovers after 3 years. We then cut the recovered bamboo culms; this clear-cutting site began to change into a broad-leaved forest. We suggest that a P. pubescens grove can be transitioned to a broad-leaved forest, using continuous selective cutting of the revived bamboo culms over several years.
The area of bamboo groves in southwest Japan, comprised mainly of Phyllostachys pubescens Mazel ex Houzeau de Lehaie, has increased over the past 30 years (e.g. Isagi and Torii, 1998; Suzuki and Nakagoshi, 2011). This rapid expansion of bamboo groves was caused by the abandonment of production groves of bamboo (Torii and Isagi, 1997) and adjacent woodland and cultivated land, because the invasive young bamboo shoots not be removed (Suzuki, 2010). Bamboo groves were originally planted to produce culms or edible young shoots; however, the need for these products has declined due to new materials and imports from China (Suzuki and Nakagoshi, 2011).
One method to halt the expansion of bamboo groves includes cutting off their culms (Ishida et al., 1999) and repeated cutting of bamboo culms (Fujii and Shigematsu, 2008).There have been studies on the control of the expansion of bamboo groves by killing bamboo culms by injecting or spreading weed killer (Egami et al., 2015; Nonaka, 2002). However, in these studies, vegetation changes after cutting an area of bamboo culms were not carefully inspected over several years. Fujii and Shigematsu (2008) said that the occurrence of new young bamboo shoots was seen under cutting bamboo culms for three years. As the bamboo groves transition to broad-leaved forests, it is necessary to observed occurrence of new bamboo culms and vegetation change after clear-cutting cutting by investigation term as long as possible.
In the present study, we investigated the change in species composition by repeating P. pubescens culm cutting, and we suggest the most effective method for a smooth transition from abandoned bamboo groves to broad-leaved forests.
We conducted the experiment in Genkotsu-yama Hill (175 m above sea level), located in neighbouring Sanbe dam, Oda City, Shimane Prefecture, western Japan (Fig. 1). There are secondary forests comprised of Quercus serrata Thunb. ex Murray and Pinus densiflora Sieb. et Zucc. On the southeast side of the hill, there were graves until the 1990s; after which P. pubescens invaded the gravesite and the adjacent secondary forests. The culm density of P. pubescens in the center of the grove was 5600 to 9700 ha-1.
Study area.
The annual mean precipitation and mean temperature from 1981 to 2010 were 1738.4 mm and 15.1 °C, respectively, based on data from the nearest meteorological observatory in Oda (35° 11.4′ N, 132° 29.8′ E).
Field ExperimentWe established four quadrate plots (10 × 10 m; Fig. 1). Plot A was the control site for the P. pubescens groves without cutting, Plot B was the site of cutting all P. pubescens culms, Plot C was the site of thinning the 67% of P. pubescens culms in the secondary forest mixed with bamboo, and Plot D was the control site for secondary forest mixed with bamboo. Plot B was set up in the center of the site of cutting all P. pubescens culms so as not to be affected as much as possible from residual bamboo groves.
We surveyed the plant species composition in all strata (Braun-Blanquet, 1964) and all tree diameters at breast height (DBH) before cutting in September 2005. After this survey, bamboo culms were cut down in the area showed in Fig. 1 (ca. 80 m2; Plot B and a part of Plot C).
After cutting, we surveyed the plant species composition and all tree's DBH in June 2006, September 2006 (Plot B only), June 2007, and September 2008. Over these 3 years, we left each plot undisturbed.
In September 2008 (after the survey), we cut down all of the P. pubescens culms in Plot B. Subsequently, we cut down all of new P. pubescens culms after survey of every year through 2012. We also surveyed plant species composition and all tree's DBH in September 2009, August 2010, September 2011 (Plot B only), and August 2012.
AnalysisWe compared coverage rates of every layer and survey period. We calculated and compared the number of culms per DBH and the total cross-sectional areas at breast height for P. pubescens and other tree species in each plot.
All plant species in the survey plots were classified with respect to life form. Species number with respect to the classification was compared among survey periods.
After clear-cutting (Fig. 2a), P. pubescens returned the next spring with a large number of thin new culms in Plot B (average DBH = 1.4 cm; Fig. 3). However, the height of the culms was below 2 m; they covered the shrub and herb layer with high coverage rate (Fig. 4). The total cross-sectional area at breast height of P. pubescens in Plot B was 118 cm2 in June 2006 (Fig. 5); after 3 years, it increased to 749 cm2. However, in 2008, the total cross-sectional area at breast height of other tree species in Plot B was 51 cm2.
Pictures of Plot B in cutting of 2005 (a), 2008 (b), and 2012 (c).
The histogram of diameters at breast height of Phyllostachys pubescens culms (solid) and other trees (outline) in Plot B.
Vegetation cover rate in each layer. The arrows show the cutting Phyllostachys pubescens culms. 2006a and 2006b designated Jun 2006 and Sep 2006, respectively.
Total cross-sectional area of Phyllostachys pubescens and other woody species. The arrows show the cutting P. pubescens culms. The arrows show the cutting Phyllostachys pubescens culms. 2006a and 2006b designated Jun 2006 and Sep 2006, respectively.
After 2008, we cut the recovered P. pubescens culms in Plot B. Other tree species (Rhus javanica L. var. roxburghii (DC.) Rehder et Wils., Quercus glauca Thunb. ex Murray, Firmiana simplex (L.) W. F. Wight, among others; Appendix) were allowed to grow. In 2012, the total cross-sectional area at breast height of P. pubescens and other tree species was 3 cm2 (only one culm; Fig. 3) and 366 cm2, respectively (Fig. 4).
In Plot C, a section of P. pubescens culms was cut in September 2005. The total cross-sectional area at breast height of P. pubescens decreased from 2,669 to 814 cm2 (Fig. 5). Subsequently, the P. pubescens culms recover till 2009 (991 cm2) by recruitment. Although six P. pubescens culms died between 2009 and 2010, total cross-sectional area was decreased. In 2011 and 2012, a new culm grew every year and total cross-sectional area of P. pubescens was increased between 2010 and 2012.
In Plots A and D, there were few changes in the total cross-sectional area.
Species Composition and Coverage RateBefore cutting, P. pubescens occupied the tree layer in Plots A and B. In Plots C and D, P. pubescens, Quercus sessilifolia Blume, and Q. serrata competed in the tree layer. In Plot C, P. pubescens occupied the sub-tree layer (Appendix).
The tree layer in Plot B disappeared and the coverage rates of the sub-tree layer in Plot C decreased from 80% to 30% as P. pubescens culms were cut (Fig. 4). The coverage rate of the herb layer in Plot B decreased from 95% to 20% with the destruction due to clear-cutting.
In Plot B, the coverage rate of the herb layer recovered after September 2006 (Fig. 4). The coverage rates of the shrub and sub-tree layer recovered in 2008. This recovery was initiated by the recruitment of P. pubescens culms. After the selective cutting of 2008, the coverage rates of the shrub layer were between 15% and 35%. The height of the shrub layer rose to 8.4 m in 2012 (Appendix).
In Plot C, the coverage rate of sub-tree layer was decreased by selective cutting of P. pubesces between 2005 and 2006. Thereafter, the coverage rates of sub-tree layer and shrub layer changed among 20% and 40%, and the coverage rates of herb layer little change in 1% or 2%. The coverage rate of all layers in Plots A and D decreased very little over 7 years (Fig. 4).
Regarding species composition, the number of species present increased from 25 to 57 in Plot B, the spring after the cutting (Fig. 6); these were mainly annual and perennial herbs, especially, Sasa veitchii (Carriere) Rehder var. tyugokensis (Makino) S. Suzuki and Nandina domestica Thunb., dominated by recovered P. pubescens culms (Appendix). In 2007, annual herb and perennial herb species decreased from seven to two and 15 to seven, respectively (Fig. 6). However, Q. glauca, Morus australis Poir., Castanea crenata Sieb. et Zucc., Zanthoxylum ailanthoides Sieb et Zucc., and Rubus spp. increased through 2008 (Appendix). P. pubescens recovered over their species. Before selective cutting in 2008, they covered other emergence and residual species. The surveys in 2006 and 2007 were conducted in June, but no major difference was found in the emerging species.
Number of species in each life form. The arrows show the cutting Phyllostachys pubescens culms. 2006a and 2006b designated Jun 2006 and Sep 2006, respectively.
After selective cutting, the species number at plot B recovered to 56 in 2009 (Fig. 6). After this, the species number decreased as Clethra barbinervis Sieb. et Zucc., Mallotus japonicus, R.japanica var. roxburghii, Celtis sinensis, Firmiana simplex, and Deutzia crenata grew in the shrub layer and S. veitchii var. tyugokensis covered the herb layer in Plot B (Appendix).
In Plot C, the species number increased slightly (Fig. 6); however, some Z. ailanthoides, Q. serrata, and P. densiflora individuals died owing to diseases, in Plots C and D. This affected the cross-sectional area at breast height (Fig. 5).
In Plot A, the species of perennial herbs increased (Fig. 6). This plot also had increased brightness due to cutting of P. pubscens culms in an adjacent area.
Regenerating bamboo culms appeared the spring after cutting. In first year after cutting, bamboo culms became thin (Fig. 3). Ishida et al. (1999), Fujii and Shigematsu (2008) and Abe and Shibata (2009) reported the same events. The regenerated bamboo culms were abandoned till fall of 2008, three years after cutting all P. pubescens culms. They covered other emergence and residual species. The same transitions have been reported by Fujii and Shigematsu (2008). Therefore, P. pubescens came back as at the beginning of the cutting, if regenerating bamboo culms were abandoned.
We find one thin culms in Plot B till 2012, three years after selective cutting recovery bamboo culms every year (Fig. 3), although it took as much distance as possible from remaining bamboo grove. Ishida et al. (1999) documented recruiting new culms in two years after cutting all bamboo culms. Fujii and Shigematsu (2008) documented recruiting new culms in three years after cutting all bamboo culms. It is thought that the rhizomes of P. pubescens survive for several years after cutting the above ground part. When changing vegetation from bamboo groves, continuous P. pubescens culm cutting is needed for suppression of bamboo culms during several years, over than three years.
In Plot B, many species, mainly herb species and pioneer trees, were covered after the cutting P. pubscens culms (Fig. 6, Appendix). Herb species and N. domestica increased between September 2005 and September 2006. However, after the size of recovery bamboo culms increased between 2007 and 2008 (Fig. 3), they declined because they were shaded by P. pubescens. After selective cutting of recovery bamboo culms, pioneer tree species grew and S. veitchii var. tyugokensis dominated the herb layer (Fig. 5, Appendix) because P. pubescens, which had shaded them, was removed. However, the height and species composition of Plot B were not similar to those of Plot D or C which were the broad-leaved forest or the bamboo and broad-leaved tree mixed woodlands, because the pioneer tree species, M. japonicas, R. japonica var. roxburghii and C. sinensis, dominated in plot B but Q. sessilifolia and Q. serrata dominated in plot C or D (Appendix). Thus, we considered that it will take some time to form broad-leaved forests from bamboo groves.
The number of emerging species of perennial herbs increased in Plot A (Fig. 4.) were became the sunlight brightened the forest floor, because the cover rate of the tree layer decreased due to the death and breakage of P. pubescens culms during this period (Fig. 5) and that bamboo culms in adjacent area were clear cut.
When renaturalization from a P. pubescens grove to a broad-leaved forest, we recommend to continue the selective cutting of revived bamboo culms for several years.
We are grateful to the members of the NPO Communication Convention between Green and Water Oda for their arrangement to survey the area and for cutting bamboo culms. We also thank the members of the laboratory in the Graduate School for International Development and Cooperation, Hiroshima University, and the Department of Geography of Ritsumeikan University for field works and surveys.
