共查询到19条相似文献，搜索用时 843 毫秒
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以秭归、兴山、巴东、夷陵4县(区)和神农架南坡813 km2的地域为研究对象,在推广、应用、转化“鄂西山地长江上干流生态经济型防护林体系营建技术研究”科技成果的基础上,根据海拔高度的不同,划分了4个垂直气候带。通过对坡度的调查,根据气候带、坡度、立地条件等因子,划分了防护林类型,建立了4种防护林模式类别,在模式类别的基础上建立了11个防护林模式类型,在模式类型的基础上建立了33个模式种类,总结出33个模式种类的关键技术,并建立了模式分类体系,找出了模式的规律性。 相似文献
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农区防护林在保障农业生产、改善生态环境方面作用巨大。本文分析了农区防护林的正外部性,界定了其公共品的属性。但是,当前农区防护林发展中还存在着一些问题：对农区防护林重视程度不够;财政投入相对不足;林业技术推广与服务有待加强;防护林经营模式有待改进。因此,在宏观层面．应进一步完善农区防护林的投融资制度,加大财政支林力度,切实提高林业技术推广、服务水平．把防护林生态效益补偿提高到一个合适的水平;在微观层面,应不断优化农区防护林经营模式,提高经营主体的参与程度,保障其合法权益,充分调动林农积极性、提高防护林营造质量。 相似文献
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利用线性规划对兴胜村防护林体系优化模式示范区的土地利用进行评价,肯定了这种模式的合理性,并提出了今后农田防护林的发展方向是建成一个完整的最优的大农业生态系统。 相似文献
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利用第六次至第九次全国森林资源清查河北省2001,2006,2011,2016年4个年度的固定样地调查数据,采用非线性回归估计方法,建立了18个树种组的单木胸径生长率和材积生长率模型,以及12个树种组的林分材积生长率模型。结果表明,单木生长率模型的平均预估误差(MPE)基本都在3%以内,而平均百分标准误差(MPSE)、胸径生长率模型大都在10%以内,材积生长率模型大都在20%左右;林分生长率模型的平均预估误差(MPE)基本都在5%以内,平均百分标准误差(MPSE)大都在25%以内。所建模型可为河北省开展森林资源年度更新提供技术支撑。 相似文献
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西藏自治区主要树种生长率模型的研建 总被引：2，自引：2，他引：0
利用西藏自治区2001年森林资源连续清查中复查的493个地面样地的复位样木资料,研究建立了冷杉、云杉、柏木、落叶松、华山松、高山松、乔松、栎类、桦类、杨类、硬阔类、软阔类等12个树种(组)的胸径生长率模型,并导算出了其相应的材积生长率模型,为西藏各类森林资源清查估算生长量提供了参考依据,尤其为2006年西藏森林资源连清复查判定保留木胸径测量值是否正常提供了定量依据。 相似文献
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Determination of site quality is a basic tool for proper selection of locations and species, in management of forest plantations.Throughout the Caribbean studies of site quality are few and are hampered by statistical limitations, inappropriate growth models, and limited data. We fitted growth curves for dominant height to evaluate and classify site quality of teak (Tectona grandis) plantations by using data from 44 permanent sample plots established since 1990 in 3 22 years old teak plantations in the Colombian Caribbean region. We used Korf’s and von Bertalanffy’s models to fit curves as nonlinear effects models. Both models, with a single random parameter, were considered as adequate for dominant height growth modelling, but Korf’s model was superior. There sulting curves were anamorphic and closely reflected high variability insite quality. Five site classes were clarified: at a base age of 12 years old,teak reached a mean dominant height of 24.8 m on the best sites, 9.8 m inthe worst sites, and in the averages sites, 15.8-18.8 m. Using this model,we identified the best and the worst sites for teak plantations in the Caribbean region. This model proved a useful tool, not only for site quality evaluation, but also for improved teak plantation planning and management. 相似文献
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Annualized diameter and height growth equations for Pacific Northwest plantation-grown Douglas-fir, western hemlock, and red alder 总被引：2，自引：0，他引：2
Aaron R. Weiskittel Sean M. Garber Gregory P. Johnson Douglas A. Maguire Robert A. Monserud 《Forest Ecology and Management》2007,250(3):266-278
Simulating the influence of intensive management and annual weather fluctuations on tree growth requires a shorter time step than currently employed by most regional growth models. High-quality data sets are available for several plantation species in the Pacific Northwest region of the United States, but the growth periods ranged from 2 to 12 years in length. Measurement periods of varying length complicate efforts to fit growth models because observed growth rates must be interpolated to a common length growth period or those growth periods longer or shorter than the desired model time step must be discarded. A variation of the iterative technique suggested by Cao [Cao, Q.V., 2000. Prediction of annual diameter growth and survival for individual trees from periodic measurements. Forest Sci. 46, 127–131] was applied to estimate annualized diameter and height growth equations for pure plantations of Douglas-fir, western hemlock, and red alder. Using this technique, fits were significantly improved for all three species by embedding a multi-level nonlinear mixed-effects framework (likelihood ratio test: p < 0.0001). The final models were consistent with expected biological behavior of diameter and height growth over tree, stand, and site variables. The random effects showed some correlation with key physiographic variables such as slope and aspect for Douglas-fir and red alder, but these relationships were not observed for western hemlock. Further, the random effects were more correlated with physiographic variables than actual climate or soils information. Long-term simulations (12–16 years) on an independent dataset using these annualized equations showed that the multi-level mixed effects models were more accurate and precise than those fitted without random effects as mean square error (MSE) was reduced by 13 and 21% for diameter and height growth prediction, respectively. The level of prediction error was also smaller than an existing similar growth model with a longer time step (ORGANON v8) as the annualized equations reduced MSE by 17 and 38% for diameter and height growth prediction, respectively. These models will prove to be quite useful for understanding the interaction of weather and silviculture in the Pacific Northwest and refining the precision of future growth model projections. 相似文献
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Predicted models for potential canopy rainfall interception capacity of landscape trees in Shanghai,China 总被引：1，自引：0，他引：1
Jiankang Guo Bingqin Yu Yuan Zhang Shengquan Che 《European Journal of Forest Research》2017,136(3):387-400
This study aimed to build urban green space with environmental functions (e.g., canopy interception of rainfall) and adjust hydrographic balance to some extent for forecasting the potential canopy rainfall interception capacity of landscape trees and the effects on rainfall distribution. The effects of urban green space on interception and runoff reduction have been conceptualized, but not quantified. Therefore, the leaf area index and the water storage abilities of 17 kinds of landscape trees in common use were measured, at Shanghai, and canopy rainfall interception capacity was calculated using the interception formula. The predicted rainfall interception capacity models were established choosing tree morphological characteristics (diameter at the breast height, height, and crown width) as variables. The model test showed that the errors of 12 models were less than 5% between the predicted and the measured data and the errors of four models were within 5 and 10%, with the error for only one model being between 10 and 11%. Also, the study indicated that conifer trees were able to hold more rainfall compared with broad-leaved trees per unit area (k). The results showed that these models could effectively predict the potential capacity of canopy rainfall interception for landscape trees in Shanghai area and were beneficial for species selection in constructing plant communities, aiming to improve the rainfall interception capacity of urban green space. 相似文献
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Internal bond (IB) strength is one of the most important me-chanical properties that indicate particleboard quality. The aim of this study was to find a simple regression model that considers the most ... 相似文献