Search results for: Yuancai Lei

Items from 1 to 11 out of 11 results

article

A spatial model for rare binary events

Samuel A. Morris, Brian J. Reich, Krishna Pacifici, Yuancai Lei

Environmental and Ecological Statistics > 2017 > 24 > 4 > 485-504

Many predominant spatial methods for binary data use a latent Gaussian process to capture spatial dependence. However, this may not be appropriate for rare data because these methods based on Gaussian processes are asymptotically independent as the event probability goes to zero. In this paper, we propose a method for rare binary data that builds on spatial extreme value theory. We model binary events...

article

Comparison of seemingly unrelated regressions with error-in-variable models for developing a system of nonlinear additive biomass equations

Liyong Fu, Yuancai Lei, Guangxing Wang, Huiquan Bi, more

Trees > 2016 > 30 > 3 > 839-857

Key message Nonlinear error-in-variable models can advance the development of the systems of additive biomass equations and lead to much higher prediction accuracy of tree biomass than nonlinear seemingly unrelated regression. Abstract In this study, the approach of nonlinear error-in-variable models (NEIVM) was compared with nonlinear seemingly unrelated...

article

Uncertainty of forest biomass carbon patterns simulation on provincial scale: A case study in Jiangxi Province, China

Yifu Wang, Tianxiang Yue, Yuancai Lei, Zhengping Du, more

Journal of Geographical Sciences > 2016 > 26 > 5 > 568-584

Forest vegetation carbon patterns are significant for evaluating carbon emission and accumulation. Many methods were used to simulate patterns of forest vegetation carbon stock in previous studies, however, uncertainty apparently existed between results of different methods, even estimates of same method in different studies. Three previous methods, including Atmosphere-vegetation interaction model...

article

Adverse influences of drought and temperature extremes on survival of potential tree species for commercial environmental forestry in the dryland areas on the western slopes of New South Wales, Australia

Huiquan Bi, Jagrutee Parekh, Yun Li, Simon Murphy, more

Agricultural and Forest Meteorology > 2014 > 197 > C > 188-205

In order to search for suitable tree species for commercial environmental forestry over the vast semiarid and drought prone areas across the western slopes of New South Wales, Australia, a large species trial involving nine selected potential species was established at 45 sites over three broad regions in 2000. A year later, the “Millennium Drought”, the longest uninterrupted series of years with...

article

Parameter estimation of two-level nonlinear mixed effects models using first order conditional linearization and the EM algorithm

Liyong Fu, Mingliang Wang, Yuancai Lei, Shouzheng Tang

Computational Statistics and Data Analysis > 2014 > 69 > Complete > 173-183

Multi-level nonlinear mixed effects (ML-NLME) models have received a great deal of attention in recent years because of the flexibility they offer in handling the repeated-measures data arising from various disciplines. In this study, we propose both maximum likelihood and restricted maximum likelihood estimations of ML-NLME models with two-level random effects, using first order conditional expansion...

article

Tree mortality in response to climate change induced drought across Beijing, China

Xiongqing Zhang, Yuancai Lei, Yong Pang, Xianzhao Liu, more

Climatic Change > 2014 > 124 > 1-2 > 179-190

Tree mortality in response to climate change induced drought has emerged as a global concern. Small changes of tree mortality rates can profoundly affect forest structure, composition, dynamics and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from natural stands (82 plots) in Beijing showed that tree mortality rates have increased significantly over the two decades...

article

Nonlinear mixed-effects crown width models for individual trees of Chinese fir (Cunninghamia lanceolata) in south-central China

Liyong Fu, Hua Sun, Ram P. Sharma, Yuancai Lei, more

Forest Ecology and Management > 2013 > 302 > Complete > 210-220

An individual-tree crown width model was developed with data from 2461 Cunninghamia lanceolata trees in 103 sample plots located on a Huangfengqiao state-owned forest farm in south-central China. To prevent correlations between observations from the same sample plot but different classes of site index, we developed a nested two-level nonlinear mixed-effects (NLME) model that accounts for the random...

article

Regression-type estimators for adaptive two-stage sequential sampling

Mohammad Salehi, Bardia Panahbehagh, Afshin Parvardeh, David R. Smith, more

Environmental and Ecological Statistics > 2013 > 20 > 4 > 571-590

Adaptive two-stage sequential sampling (ATSSS) design was developed to observe more rare units and gain higher efficiency, in the sense of having a smaller variance estimator, than conventional sampling designs with equal effort for rare and spatially cluster populations. For certain rare populations, incorporating auxiliary variables into a sampling design can further improve the observation of rare...

article

Two-stage sequential sampling for two rare species in western Inner Mongolia of China

JingJing Shi, TianZhong Zhao, YuanCai Lei

Chinese Science Bulletin > 2013 > 58 > 4-5 > 507-516

To evaluate the efficiencies of different sampling methods for a rare and clustered population, we investigated the sampling effects for the two species Tamarix chinensis (Salt cedar) and Elaeagnus angustifolia (Russian olive) in western Inner Mongolia with two-stage sequential sampling, which is a new sampling method, traditional simple random sampling and two-stage sampling. Based on two-stage sequential...

article

Predicting tree recruitment with negative binomial mixture models

Xiongqing Zhang, Yuancai Lei, Daoxiong Cai, Fengqiang Liu

Forest Ecology and Management > 2012 > 270 > Complete > 209-215

Tree recruitment models play an important role in simulating stand dynamic processes. Periodic tree recruitment data from permanent plots tend to be overdispersed, and frequently contain an excess of zero counts. Such data have commonly been analyzed using count data models, such as Poisson model, negative binomial models (NB), zero-inflated models, and Hurdle models. Negative binomial mixture models...

article

Additive prediction of aboveground biomass for Pinus radiata (D. Don) plantations

Huiquan Bi, Yushan Long, John Turner, Yuancai Lei, more

Forest Ecology and Management > 2010 > 259 > 12 > 2301-2314

A general and two country-specific systems of additive equations were developed to predict aboveground biomass of Pinus radiata plantations from stand variables that are routinely measured in inventory plots and predicted by conventional growth and yield models. The data for this work consisted of 319 plot-based biomass estimates that were derived from individual tree biomass equations developed in...

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