| Phyllostachys edulis is the most important economic and ecological bamboo species in China.As typical uneven-aged forest,the deforestation has been harvested by artificial selection for thousands of years.However,the management of bamboo stands is confronted with the double pressures,which are the declined product price caused by the adjustment of international bamboo industrial structure,and the rising labor costs caused by the short of rural labor force.The profit margins of bamboo forest management continuously shrink,as a result,a large number of high-quality bamboos can not be harvested and utilized effectively,which has become the biggest bottleneck problem of bamboo forest management,and even restricts the development of the bamboo industry.In this context,strip clearcutting,with advantages of high efficiency and low cost,and has attracted great attention of scientists.However,the natural growth and development of Phyllostachys edulis is certainly disturbed by strip clearcutting.Whether cut bamboo forest will restore,what restoration characteristics will occur,what and how internal/ external factor influence the restoration process is remain unknown.In this study,logging strips with four different logging stripwidth were set up hierarchically in bamboo forest located at Huangshan District,Anhui Province.The initial restoration characteristics of bamboo forest with different strip clearcutting were studied systematically in contrast with the control of artificial selective logging bamboo forest.The relationship between internal/environmental factors and restoration characteristics was analyzed.Our study aims to explore the restoration laws of strip clearcutting bamboo forest and the appropriate logging intensity,and provide essential data,theory and technic support for the scientific and feasible evaluation of strip clearcutting.The main results are as follows:1.There was a close relationship between the initial recovery characteristics and the strip clearcutting intensity of bamboos forests,and which showed a certain regularity.The temporal,spatial,quantitative and qualitative characteristics of Moso bamboo forests with 3 m(D1),6 m(D2),9 m(D3)and 12 m(D4)logging intensities were systematically studied during restoration process.In terms of temporal characteristics,the number of spring shoots,degraded shoots and new bamboos showed obvious normal distribution at different developmental period among all logging areas,and reached the peak in the second week(from March 26 to April 1).In terms of spatial characteristics,spring shoots and new bamboos of 6 m cutting strip and the control stand were randomly distributed at all scales.While spring shoots of 9 m and 12 m logging strips showed aggregated distribution at small scales,and new bamboos showed regular distribution at certain scales.In terms of quantitative characteristics,the number of spring shoots per unit area of clearcutting treatments was more than that of control,and in the order of which was D3,D1,D2,D4 and CK.The order of new bamboos number per unit area was D3,D4,CK,D2 and D1.In terms of qualitative characteristics,the average DBH of new bamboos decreased regularly with the increase of logging intensity,and was negatively correlated with the distance of individual location from strip margin.The average DBH of new bamboos from D1 to D4 was 8.9 cm,8.5 cm,7.2 cm and 6.6 cm,respectively,while that of the control stand was 9.6 cm.The aboveground biomass per unit area of new bamboos followed the descending order that is CK,D3,D4,D2 and D1.Generally speaking,the restoration of Moso bamboo forest with 6 ? 9 m logging width was better.2.The internal factors,such as non-structural carbohydrates(NSC)concent,and organ biomass distribution patterns were significantly different among new bamboos of different diameter.The relationship of water utilization capacity,photosynthetic pigment content,and photosynthetic product with the quality of new bamboo was analyzed in 12 m logging strip.And the aboveground biomass distribution pattern of new bamboo was detected.We found that the water contents of spring shoots in logging strip were lower than control.The water content of aboveground organs of new bamboos was higher in logging strip than CK,and it indicated that strip clearcutting effected the water utilization capacity of new bamboo.The chlorophyll content in the leaves of new bamboos in logging strip were higher than CK.The NSC contents of spring shoots and that in different organs of new bamboos in logging strip were lower than CK,and The NSC contents of leaves and rhizomes in small-diameter bamboo were higher,which showed that,as clonal plants,bamboo had stronger adaptabilities to adapt the environment changes.The biomass distribution pattern of aboveground organs was significantly different among new bamboos of different diameter.The biomass pattern of large-diameter bamboo was as follows bamboo clum(76.5%),bamboo branch(14.1%)and bamboo leaf(9.4%),respectively,which was consistent with the control.The proportion of leaf of middle-diameter and small-diameter bamboo increased significantly,with 28.6% and 45.1% respectively,showing strong morphological plasticity.New bamboos in logging strip can adapt to the environment to the greatest extent by improving water and light use efficiency and changing the distribution pattern of organ biomass.3.Strip clearcutting had changed the environmental factors with certain regularity,such as forest microclimate,understory vegetation biomass and soil properties factors,which will impact the restoration of logging forests consequently.The changes of forest microclimate,understory herbages and soil during a growing season were systematically studied.For microclimate,the solar radiation intensity,diurnal variation and air relative humidity of strip clearcutting stands were larger than those in selective logging stand,while,atmospheric temperature had no difference between strip clearcutting stands and selective logging stand.The amount sequence of understory herbages coverage and biomass were D1,D4,D2,D3 and CK.The herbages density,individual density and average height of 3 m logging strip were the highest,while the control was the lowest.The diurnal variation range of soil temperature improved along with the increase of logging intensity,while the diurnal variation of soil humidity was similar.The indexes of soil organic matter content,bulk density,acid phosphatase activity,C / N,C / P and non-capillary porosity were screened as the minimum data set(MDS)of soil quality assessment by principal component analysis.Based on soil quality assessment value,the rank of soil quality was D4,D2,D3,D1 and CK in the following year,indicating that strip clearcutting had a certain impact on the soil quality.Strip clearcutting interfered the water content and nutrient metabolism of Phyllostachys edulis,and altered the environmental factors by changing the stand structure.Phyllostachys edulis responded to the disturbance caused by strip clearcutting with different intensity,and showed a certain and regular recovery characteristics by physiological integration and morphological changes.On the whole,the short-term effects and soil capabilities of restoration were better in 6 m ? 9 m logging strips.Our research provides theoretical and fundamental support for realizing large-scale mechanical logging instead of traditional selective logging,which is meaningful to modern management of bamboo forest. |
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