RESUMEN
To analyze the effects of forest edge on radial growth and cell characteristics in different stand types of Larix principis-rupprechtii, we investigated the differences on radial growth, cell size and numbers between edge trees and inner trees of L. principis-rupprechtii in pure L. principis-rupprechtii forests and mixed forests of L. principis-rupprechtii and Betula platyphylla in Saihanba mechanical forest farm, China. The results showed that radial growth of the edge trees was significantly faster than that of the inner trees in pure forests, with the total ring width, earlywood width and latewood width of edge trees being 48.9%, 58.9% and 29.6% higher than those of inner trees, respectively. However, there was no difference in radial growth between edge trees and inner trees in mixed forest. The total number of earlywood cells, the number of large cells and small cells in earlywood of edge trees were increased by 63.3%, 55.6% and 70.0%, while the total number of latewood cells, the number of large cells and small cells in latewood of edge trees were increased by 35.4%, 37.5% and 28.5% compared with those of inner trees. There was no significant difference in the cell sizes between edge trees and inner trees. The cell numbers of earlywood and latewood of edge trees were not significantly different from those of inner trees in mixed forest, but the cell size in the earlywood of edge trees was 50.0% larger than those of inner trees in mixed forest. The sizes of the largest cells, the smallest cells, the large cells and the small cells in the earlywood of edge trees were increased by 28.6%, 33.3%, 16.6% and 25.0% compared with those of inner trees, respectively. The fast growth of edge trees and slow growth of inner trees in the pure forests could be effectively alleviated by cultivating mixed forests.
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Larix , Betula , China , Bosques , ÁrbolesRESUMEN
Pure and mixed larch (Larix pricipis-rupprechtii) and birch (Betula platyphylla) plantations in Saihanba area were selected as test objects, with two stand density (200-340 and 880-1100 trees·hm-2) of each stand type. Based on tree size-stratified sampling approach, a total of 668 tree core samples were collected. A linear mixed model was used to analyze the effects of tree species interaction, stand density, and tree size on larch productivity. Results showed that basal area increment of larch was affected by competition, diameter at breast height, tree age, and neighborhood density to different degrees. Overyielding of larch was mainly due to the positive effect of birch on larch growth in the mixed plantation with higher stand density. For mixed plantation with lower stand density, the productivity of those two species was lower than that pure plantation because of a lack of species interaction. Intraspecific competition was the main factor influencing larch productivity. Larch productivity was positively affected by tree size, with the magnitude of tree size effect varying with stand density and species composition. Suitable enhancement of stand density and selection of birch as the mixing tree species could improve productivity of larch.
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Larix , Betula , ÁrbolesRESUMEN
Litter is an important contribution to forest soil. Litter decomposition plays an important role in nutrient cycling of forest ecosystem. A field litterbag experiment was conducted to examine the dynamics of decomposition rate, nutrient release and enzyme activity during litter decomposition in the pure forests of Larix principis-rupprechtii (L) and mixed forests, including L and Betula platyphylla (B), L and Quercus mongolica (Q), as well as LBQ, in Saihanba area, Hebei Pro-vince, China. The results showed that the decomposition rate of leaf litter in L forest was significantly lower than that in mixed forests during the 720 d decomposition. The LB had the highest decomposition rate of L leaf litter. All treatments had the same change trend of nutrient contents, with the contents of N and P being increased and that of C, K and C/N being decreased. Contrast to pure leaf litter of L, leaf litter in mixed forests could promote the release of C and K, and inhibit litter N and P release. During the litter decomposition, the activities of catalase, urease and acid phosphatase increased, while that of sucrase decreased in all leaf litter of forests. The decomposition rate of leaf litter was positively correlated with the activities of catalase, urease and acid phosphatase, negatively correlated with that of sucrase. Our results showed that leaf litter mixture of L. principis-rupprechtii, B. platyphylla and Q. mongolica could enhance the litter decomposition of L. principis-rupprechtii, and that enzyme activities were closely related to litter decomposition.
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Larix , Árboles , China , Ecosistema , Bosques , Nutrientes , Hojas de la Planta , SueloRESUMEN
To explore the changes of vegetation landscape pattern and its driving mechanism in Saihanba Nature Reserve, we analyzed vegetation type changes from 1989 to 2013 and the driving factors using random forest and Logistic regression models in conjunction with land dynamic degree indicator, based on three Landsat TM imageries obtained in 1989, 2000 and 2013. The results showed that the proportion of shrubland was always small in this area from 1989 to 2013. During 1989-2013, the proportion of shrubland rapidly decreased and plantation area significantly increased, while the area of grassland and natural secondary forest slightly changed. Key driving factors for the vegetation dynamics were dependent on vegetation type and time. The change of each vegetation type from 1989 to 2000 was significantly influenced by social factors, i.e. distance to road and total investment of afforestation. Since the implementation of the Natural Forest Protection Project and establishment of Saihanba Nature Reserve, the role of natural factors including elevation and aspect gradually became more important during the 2000-2013. The vegetation landscape dynamics were primarily determined by social activities, while the distribution patterns of vegetation types were probably controlled by natural factors in the study area.
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Conservación de los Recursos Naturales , China , EcosistemaRESUMEN
Quantitative analysis of the relationships between the distribution of natural plant communities and environmental factors was studied using two-way indicator species analysis (TWINSPAN) and detrended canonical correspondence analysis (DCCA) methods, in the Saihanba National Nature Reserve in Hebei Province. The results showed that the natural plant communities in the Saihanba Reserve could be classified into eight types, i.e., Sanguisorba officinalis + Carex heterostachya + Trollius chinensis community, S. officinalis + Elymus sibiricus + Geranium platyanthum community, C. lanceolata + Ophiopogon chingii community, Spiraea pubescens - Tripolium vulgare community, Armeniaca sibirica + S. pubescens - T. vulgare + C. lanceolata community, Quercus mongolica + Betula costata - Lespedeza bicolor + S. pubescens - C. lanceolata community, Betula platyphylla + Populus davidiana - Corylus mandshurica + Rosa davurica - Phlomis umbrosa + C. lanceolata + Thalictrum aquilegifolium community and Picea asperata + B. platyphylla - Rosa davurica + Salix taishanensis var. hebeinica - C. lanceolata + Commelina diffusa community. DCCA analysis indicated that slope position and soil nutrients were the main influence factors for the spatial distribution of natural plant communities in the Saihanba National Nature Reserve. Topographic, spatial and soil factors accounted for 34.02% of the variation of species pattern. Of the variation, soil factors accounted for 15.67%, topographic factors 10.05% and spatial factors 6.00%. In the interactions among all factor combinations (2.30%), the interaction between soil and topographic factors was the largest (0.93%), and the interaction among soil, topographic and spatial factors was the least (0.16%). The unexplained portion accounted for 65.98% of spatial distribution, which might be due to anthropogenic disturbance or interspecific competition.
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Ecosistema , Poaceae/clasificación , Árboles/clasificación , China , SueloRESUMEN
It is often difficult to estimate site indices for different types of plantation by using an ordinary site index model. The objective of this paper was to establish a site index model for plantations in varied site conditions, and assess the site qualities. In this study, a nonlinear mixed site index model was constructed based on data from the second class forest resources inventory and 173 temporary sample plots. The results showed that the main limiting factors for height growth of Larix principis-rupprechtii were elevation, slope, soil thickness and soil type. A linear regression model was constructed for the main constraining site factors and dominant tree height, with the coefficient of determination being 0.912, and the baseline age of Larix principis-rupprechtii determined as 20 years. The nonlinear mixed site index model parameters for the main site types were estimated (R2 > 0.85, the error between the predicted value and the actual value was in the range of -0.43 to 0.45, with an average root mean squared error (RMSE) in the range of 0.907 to 1.148). The estimation error between the predicted value and the actual value of dominant tree height for the main site types was in the confidence interval of [-0.95, 0.95]. The site quality of the high altitude-shady-sandy loam-medium soil layer was the highest and that of low altitude-sunny-sandy loam-medium soil layer was the lowest, while the other two sites were moderate.
