| Natural vegetations are being changed distinctly due to climate changing and man-made interference. Whereas the area of plantations are extending constantly and plantations affect powerfully upon ecosystem. Because the single species components of the vegetations, which differed greatly from natural forests, caused many problems such as the cycle of material is slow, soil deteriorating, lower productivity. Thus resulted in ecosystem declining. It is necessary to study the differences between natural forests and plantations. Pinus tabulaeformis grows in many regions of north in China, having important functions in water and soil conservation, but those studies for Pinus tabulaeformis plantations are still less, especially for the contrasting analyses to natural forests and plantations of the species. Because of the special geographical position and ecosystem diversity, Qinling is ranked international biodiversity key region, Xuyangba forest region stands the center of Qinling southern slope, forests are dense and present obvious vertical distribution. In this paper, we investigated the species components, community structures, species diversity, species richness, seedling regeneration characteristics and soil nutritional status of the natural secondary forest and the plantation, in order to clear influence of different management style on restoration of the communities after disafforest about 40 years. Main results as follow:1. Based on the survey and the date, characteristics of species compositions and structures of two communities were analysed, the results indicted that (1) The natural secondary forest was composed of 134 vascular species which belonged to 66 families, 104 genera, Compositae was the family with the richest species, followed by Rosaceae, Caprifoliaceae, Gramineae; The planted forest included 125 vascular species which belonged to 73 families, 104 genera, Rosaceae occupied a dominant position, then Caprifoliaceae, Compositae and Gramineae; The families which included 1 to 2 species were plentiful in the two communities; There were 70 co-occurring species between the two communities that resulted in 53.03% at similarity index. (2)The vertical structures of the two communities were similar and divided into three layers, i.e. arbor layer, shrub layer and herb layer, and arbor layers were divided into three sublayers; Height and diameter of arbor layer, height and coverage of shrub layer and coverage of herb layer in plantation were significantly greater than those in natural forest (P<0.05), but the coverage of arbor layer between natural secondary forest and plantation was similar (P>0.05); Important values of dominating species in two communities did not show significant difference (P>0.05), but P. tabulaeformis height in secondary forest was lower than that in planted forest (P<0.05). (3) The spatial distribution patterns of main species in two communities were all clump distribution, the aggregating intensity of P. tabulaeformis in planted forest was higher than that in secondary forest, the aggregating intensities of Symplocos paniculata and Mattenccia strathiopteris were similar between two communities; The density of arbor layer in plantation was lower than that in natural forest (P<0.05), the density of shrub layer between natural secondary forest and plantation was similar(P>0.05), but the plant density of herb layer was higher in plantation (P<0.05).2. The analyses of diversity characteristics of two communities showed that Margalef index, Richness index of arbor layer appeared lower in artificial forest (P<0.05), Evenness index appeared lower in natural secondary forest (P<0.05), Shannon-Wiener index, Simpson index were similar between two communities (P>0.05); The differences of all indexes of the shrub layer between the two communities were non-significant (P>0.05); In the herb layers, Simpson's Dominance index in plantation was higher than that in the secondary forest (P<0.05), The differences of Margalef index, Richness index, Shannon-Wiener index, Evenness index between the two communities were non-significant (P>0.05).From the angle of spatial patterns, Margalef indexes, Richness indexes and Shannon-Wiener indexes of the both communities varied as follow: shrub layer> herb layer> tree layer; Simpson indexes of the both communities varied as follow: tree layer>herb layer>shrub layer; Evenness indexes varied as follow: a) secondary forest: shrub layer>herb layer>tree layer; b) plantation: shrub layer>tree layer>herb layer.3. The seedings of several main species were investigated and the results showed that (1) In two communities, P. tabulaeformis seedlings, Quercus aliena var.acutserrata seedlings, Pinus armandii seedlings distributed in all measured quadrats in the study; (2) The densities of P. tabulaeformis seed seedlings, P. armandii seed seedlings and Q. aliena var.acutserrata sprout seedlings between the two communities were non-significant (P>0.05), the densities of seed seedlings and total seedings of Q. aliena var. acutserrata in natural forest were higher than those in plantation(.P<0.05); (3) The average age and average height of P. tabulaeformis seedlings between the two communities did not show significant difference (P>0.05), the age and height of Q. aliena var.acutserrata seedlings in plantation were higher than those in the secondary forest (P<0.05); the age and height of P. armandii seedlings in the secondary forest. were higher than those in plantation(P<0.05).4. Adopting diameter structer to replace age structer to carry on dynamics analysis, the results indicated that diameter-class structures of the same plant populations were similar between the two vegetation types. Diameter-class structures of P. tabulaeformis taked on conversed J belonged to a stable type, P. tabulaeformis had played and would play an important role in the restoration of vegetation in this region; Diameter-class structures of Q. aliena var. acutserrata presented pyramid tended to be a growing type; Diameter-class structures of P. armandii appeared L which was characterized by a growing type.5. The static life table and survival curve analyses showed that the survivorship states of the main species in natural secondary forest were consistent with those in plantation. The survival curve of P. tabulaeformis tended to be the type Deevey II, the survival curves of Q.aliena var.acutserrata and P. armandii all exhibited as Deevey HI type. The peak mortality of main species appeared in age 1, it became stable for mortality rates in age 2, there were higher mortality rates in the stage of middle and end.6. Litter layer in plantation was thicker than that in natural secondary forest(P<0.05), but pH was lower than that in natural secondary forest(P<0.05), indexes of nutrient in soil had not significant differences between natural secondary forest and plantation(P>0.05).These results indicated that the plantations and the natural secondary forest had more similarity in species composition, space structure, biodiversity, main population structures and dynamics, soil status after 40 years' restoration.As a result, P. tabulaeformis is suitable for the afforestation at Xunyangba region in Qinling Mountain; Given rational tending, artificial P. tabulaeformis forest could accelerate the restoration of vegetation. |
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