Ranked set sampling (RSS) is a sampling approach that leads to improved statistical inference in ... more Ranked set sampling (RSS) is a sampling approach that leads to improved statistical inference in situations where the units to be sampled can be ranked (either through some subjective judgment or via the use of an auxiliary variable) relative to each other prior to formal measurement. It has the most promise for leading to improved methodology in situations where ranking of the items to be sampled can be carried out relatively easily and cheaply compared to the effort and expense required for actual quantification of the characteristic of interest. Although the theoretical benefits of RSS in estimation and statistical inference have been extensively demonstrated in the literature, the methodology has not yet been widely adopted by practitioners. The aim of this study is to use a crop production dataset from the United States Department of Agriculture to demonstrate the practical benefits of RSS relative to the more commonly used simple random sampling in estimation of the mean and median of a population. The results of our study provide clear evidence that the use of RSS can lead to substantial gains in precision of estimation for both of these situations.
Isoprene emissions are a key component in biosphere-atmosphere interactions, and the most signifi... more Isoprene emissions are a key component in biosphere-atmosphere interactions, and the most significant global source is the Amazon rainforest. However, intra- and inter-annual variations in biological and environmental factors that regulate isoprene emission from Amazonia are not well understood and, thereby, poorly represented in models. Here, with datasets covering several years of measurements at the Amazon Tall Tower Observatory (ATTO) in central Amazonia, Brazil, we (1) quantified canopy profiles of isoprene mixing ratios across seasons of normal and anomalous years and related them to the main drivers of isoprene emission – solar radiation, temperature, and leaf phenology; (2) evaluated the effect of leaf age on the magnitude of the isoprene emission factor (Es) from different tree species and scaled up to canopy with intra- and inter-annual leaf age distribution derived by a phenocam; and (3) adapted the leaf age algorithm from MEGAN with observed changes in Es across leaf age...
Palms have been characterized as tolerant of high winds, but that may be a simplified view. The e... more Palms have been characterized as tolerant of high winds, but that may be a simplified view. The effects of hurricanes on palm collections at Montgomery Botanical Center offered the opportunity to investigate aspects of natural selection for wind tolerance. A major finding is that wind tolerance is correlated with geography - Caribbean palms are more resistant than South American palms. This finding prompted further investigation of palm habit - basic morphology - in relation to wind resistance. Here, we present data on basic stem shape (height and diameter), root habit characters and their relationship to wind tolerance, using examples from Coccothrinax and Syagrus. We find that stem shape correlates with hurricane tolerance in Syagrus, but not in Coccothrinax; this is consistent with natural selection of Caribbean palms for high winds.
The Cycadales are a group of significant global conservation concern and have the highest extinct... more The Cycadales are a group of significant global conservation concern and have the highest extinction risk of all seed plants. Understanding the synchronisation of reproductive phenology of Cycadales may be useful for conservation by enabling the targeting of pollen and seed collection from wild populations and identifying the window of fertilisation to aid in the cultivation of Cycadales. Phenological data for 11 species of Zamia were gathered from herbarium specimens. Four phenological characters were coded with monthly character states. DNA was isolated and sequenced for 26S, CAB, NEEDLY, matK and rbcL, and a simultaneous phylogenetic analysis of phenology and DNA sequence data was carried out. Three major clades were recovered: a Caribbean clade, a Central American clade and a South American clade. Eight species showed statistically significant synchronisation in microsporangiate and ovulate phenological phases, indicating the time of fertilisation. Close reproductive synchronisa...
Ranked set sampling (RSS) is a sampling approach that leads to improved statistical inference in ... more Ranked set sampling (RSS) is a sampling approach that leads to improved statistical inference in situations where the units to be sampled can be ranked (either through some subjective judgment or via the use of an auxiliary variable) relative to each other prior to formal measurement. It has the most promise for leading to improved methodology in situations where ranking of the items to be sampled can be carried out relatively easily and cheaply compared to the effort and expense required for actual quantification of the characteristic of interest. Although the theoretical benefits of RSS in estimation and statistical inference have been extensively demonstrated in the literature, the methodology has not yet been widely adopted by practitioners. The aim of this study is to use a crop production dataset from the United States Department of Agriculture to demonstrate the practical benefits of RSS relative to the more commonly used simple random sampling in estimation of the mean and median of a population. The results of our study provide clear evidence that the use of RSS can lead to substantial gains in precision of estimation for both of these situations.
Isoprene emissions are a key component in biosphere-atmosphere interactions, and the most signifi... more Isoprene emissions are a key component in biosphere-atmosphere interactions, and the most significant global source is the Amazon rainforest. However, intra- and inter-annual variations in biological and environmental factors that regulate isoprene emission from Amazonia are not well understood and, thereby, poorly represented in models. Here, with datasets covering several years of measurements at the Amazon Tall Tower Observatory (ATTO) in central Amazonia, Brazil, we (1) quantified canopy profiles of isoprene mixing ratios across seasons of normal and anomalous years and related them to the main drivers of isoprene emission – solar radiation, temperature, and leaf phenology; (2) evaluated the effect of leaf age on the magnitude of the isoprene emission factor (Es) from different tree species and scaled up to canopy with intra- and inter-annual leaf age distribution derived by a phenocam; and (3) adapted the leaf age algorithm from MEGAN with observed changes in Es across leaf age...
Palms have been characterized as tolerant of high winds, but that may be a simplified view. The e... more Palms have been characterized as tolerant of high winds, but that may be a simplified view. The effects of hurricanes on palm collections at Montgomery Botanical Center offered the opportunity to investigate aspects of natural selection for wind tolerance. A major finding is that wind tolerance is correlated with geography - Caribbean palms are more resistant than South American palms. This finding prompted further investigation of palm habit - basic morphology - in relation to wind resistance. Here, we present data on basic stem shape (height and diameter), root habit characters and their relationship to wind tolerance, using examples from Coccothrinax and Syagrus. We find that stem shape correlates with hurricane tolerance in Syagrus, but not in Coccothrinax; this is consistent with natural selection of Caribbean palms for high winds.
The Cycadales are a group of significant global conservation concern and have the highest extinct... more The Cycadales are a group of significant global conservation concern and have the highest extinction risk of all seed plants. Understanding the synchronisation of reproductive phenology of Cycadales may be useful for conservation by enabling the targeting of pollen and seed collection from wild populations and identifying the window of fertilisation to aid in the cultivation of Cycadales. Phenological data for 11 species of Zamia were gathered from herbarium specimens. Four phenological characters were coded with monthly character states. DNA was isolated and sequenced for 26S, CAB, NEEDLY, matK and rbcL, and a simultaneous phylogenetic analysis of phenology and DNA sequence data was carried out. Three major clades were recovered: a Caribbean clade, a Central American clade and a South American clade. Eight species showed statistically significant synchronisation in microsporangiate and ovulate phenological phases, indicating the time of fertilisation. Close reproductive synchronisa...
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