Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop mode...Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height （dbh） and merchantable stem volume （V） using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height （H） and crown area （CA）. Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predic- tions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.展开更多
Wholly defined ex vivo expansion conditions for biliary tree stem cell(BTSC)organoids were established,consisting of a defined proliferative medium(DPM)used in combination with soft hyaluronan hydrogels.The DPM consis...Wholly defined ex vivo expansion conditions for biliary tree stem cell(BTSC)organoids were established,consisting of a defined proliferative medium(DPM)used in combination with soft hyaluronan hydrogels.The DPM consisted of commercially available Kubota's Medium(KM),to which a set of small molecules,particular paracrine signals,and heparan sulfate(HS)were added.The small molecules used were DNA methyltransferase inhibitor(RG108),TGF-βType I receptor inhibitor(A83-01),adenylate cyclase activator(Forskolin),and L-type Ca2+channel agonist(Bay K8644).A key paracrine signal proved to be R-spondin 1(RSPO1),a secreted protein that activates Wnts.Soluble hyaluronans,0.05%sodium hyaluronate,were used with DPM to expand monolayer cultures.Expansion of organoids was achieved by using DPM in combination with embedding organoids in Matrigel that was replaced with a defined thiol-hyaluronan triggered with PEGDA to form a hydrogel with a rheology[G*]of less than 100 Pa.The combination is called the BTSC-Expansion-Glycogel-System(BEX-gel system)for expanding BTSCs as a monolayer or as organoids.The BTSC organoids were expanded more than 3000-fold ex vivo in the BEX-gel system within 70 days while maintaining phenotypic traits indicative of stem/progenitors.Stem-cell-patch grafting of expanded BTSC organoids was performed on the livers of Fah-/-mice with tyrosinemia and resulted in the rescue of the mice and restoration of their normal liver functions.The BEX-gel system for BTSC organoid expansion provides a strategy to generate sufficient numbers of organoids for the therapeutic treatments of liver diseases.展开更多
Collaborative forest management (CFM) is a form of forest governance in which local communities are involved in the management and decision-making processes related to forest resources. It is believed that forests und...Collaborative forest management (CFM) is a form of forest governance in which local communities are involved in the management and decision-making processes related to forest resources. It is believed that forests under such management are better in tree diversity and conservation status and thus hold more carbon stocks. The study assessed the impact of CFM on carbon stocks, tree species diversity & tree species density in Mabira Central Forest Reserve. Data were collected from plots that were systematically laid in the different purposively selected forest areas. The study findings show that there is no difference in stem density and carbon stocks between CFM and non-CFM areas. CFM areas had lower species richness compared to non-CFM areas. CFM areas, however, exhibited more species diversity than non-CFM areas. Climax colonization may favor a few dominant species over others, hence lowering species diversity despite the number of species being many in the understory, hence at the same time increasing species richness. Likewise, disturbance in CFM area may affect natural colonization and favor the emergency of many species either naturally or through assisted regeneration by reforestation, hence increasing diversity, whereas artificial selection of preferred species through harvesting may lower species richness, as observed. Recommendations for improving collaborative forest management (CFM) areas include implementing targeted interventions to enhance carbon sequestration, such as promoting reforestation and afforestation with high-carbon-storing species and strengthening monitoring and evaluation frameworks to assess carbon stock changes over time. Additionally, efforts should focus on enhancing biodiversity conservation by implementing more stringent protection measures and reducing human disturbance while encouraging community participation in biodiversity monitoring and conservation education.展开更多
Neural stem cells promote neuronal regeneration and repair of brain tissue after injury,but have limited resources and proliferative ability in vivo.We hypothesized that nerve growth factor would promote in vitro prol...Neural stem cells promote neuronal regeneration and repair of brain tissue after injury,but have limited resources and proliferative ability in vivo.We hypothesized that nerve growth factor would promote in vitro proliferation of neural stem cells derived from the tree shrews,a primate-like mammal that has been proposed as an alternative to primates in biomedical translational research.We cultured neural stem cells from the hippocampus of tree shrews at embryonic day 38,and added nerve growth factor（100 μg/L） to the culture medium.Neural stem cells from the hippocampus of tree shrews cultured without nerve growth factor were used as controls.After 3 days,fluorescence microscopy after DAPI and nestin staining revealed that the number of neurospheres and DAPI/nestin-positive cells was markedly greater in the nerve growth factor-treated cells than in control cells.These findings demonstrate that nerve growth factor promotes the proliferation of neural stem cells derived from tree shrews.展开更多
Let T be a tree. The set of leaves of Τ is denoted by Leaf(Τ). The subtree Τ—Leaf(Τ) of T is called the stem of Τ. A stem is called a k-ended stem if it has at most k-leaves in it. In this paper, we prove the fo...Let T be a tree. The set of leaves of Τ is denoted by Leaf(Τ). The subtree Τ—Leaf(Τ) of T is called the stem of Τ. A stem is called a k-ended stem if it has at most k-leaves in it. In this paper, we prove the following theorem. Let G be a connected graph and k≥2 be an integer. Let u and ν be a pair of nonadjacent vertices in G. Suppose that |NG(u)∪NG(v)|≥|G|-k-1. Then G has a spanning tree with k-ended stem if and only if G+uv has a spanning tree with k-ended stem. Moreover, the condition on |NG(u)∪NG(v)| is sharp.展开更多
In this study, compatible taper and stem volume equations were developed for Larix kaempferi species of South Korea. The dataset was split into two groups： 80% of the data were used in model fitting and the remaining...In this study, compatible taper and stem volume equations were developed for Larix kaempferi species of South Korea. The dataset was split into two groups： 80% of the data were used in model fitting and the remaining 2o% were used for validation. The compatible MB76 equations were used to predict the diameter outside bark to a specific height, the height to a specific diameter and the stem volume of the species. The result of the stem volume analysis was compared with the existing stem volume model of Larix kaempferi species of South Korea which was developed by the Korea Forest Research Institute and with a simple volume model that was developed with fitting dataset in this study. The compatible model provided accurate prediction of the total stem volume when compared to the existing stem volume model and with a simple volume model. It is concluded that the compatible taper and stem volume equations are more convenient to use and therefore it is recommended to be applied in the Larix kaempferi species of South Korea.展开更多
High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, ...High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.展开更多
The development of equations to predict tree height, crown diameter, crown depth from stem diameter of a tree species enables arborists, researchers, and urban forest managers to model costs and benefits, analyze alte...The development of equations to predict tree height, crown diameter, crown depth from stem diameter of a tree species enables arborists, researchers, and urban forest managers to model costs and benefits, analyze alternative management scenarios, and determine the best management practices for sustainable forests. The objective of this study was to develop regression prediction models for tree age, tree height, crown diameter, crown ratio and crown depth for A. senegal growing in Ferlo, in the northern Senegal. Four plantations of different years old (ISRA, 10 years old plantations, Ndodj, 8 years old plantations, Boulal, 5 years old plantations and Déali, 4 years old plantations) were selected. The following dendometric variables: crown height, crown diameter, stem diameter at the breast height, stem basal diameter (at 0.30 m) and the height from the tree base to first branch were measured on a total of 489 trees. The results suggested that the ecological structure of the different year old A. Senegal plantation revealed a bell-shaped form with left dissymmetric distribution indicating a predominance of individuals with small diameter at breast height. Allometry study of A. Senegal showed highly significant positive correlations (p = 0.00) between stem diameter at breast height, stem basal diameter, tree height, crown diameter and crown depth. Positive correlations were also found between crown diameter, tree height and crown height. Prediction models derived from these relationships can be used to estimate the tree height, stem diameter at breast height and crown depth from crown diameter with greater precision. As for A. Senegal age estimation, the established model is not strong as it can explain only 49.1% of the age variation.展开更多
基金supported by the U.S.Department of Defense,through the Strategic Environmental Research and Development Program(SERDP)
文摘Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height （dbh） and merchantable stem volume （V） using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height （H） and crown area （CA）. Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predic- tions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.
基金Major Program of National Key Research and Development Project(2020YFA0112600,2019YFA0801502)National Natural Science Foundation of China(82173019,82270638,8220374,82300718)+1 种基金Project of Shanghai Science and Technology Commission(22ZR1451100,22Y11908500)Peak Disciplines(Type IV)of Institutions of Higher Learning in Shanghai,and Shanghai Engineering Research Center of Stem Cells Translational Medicine(20DZ2255100).
文摘Wholly defined ex vivo expansion conditions for biliary tree stem cell(BTSC)organoids were established,consisting of a defined proliferative medium(DPM)used in combination with soft hyaluronan hydrogels.The DPM consisted of commercially available Kubota's Medium(KM),to which a set of small molecules,particular paracrine signals,and heparan sulfate(HS)were added.The small molecules used were DNA methyltransferase inhibitor(RG108),TGF-βType I receptor inhibitor(A83-01),adenylate cyclase activator(Forskolin),and L-type Ca2+channel agonist(Bay K8644).A key paracrine signal proved to be R-spondin 1(RSPO1),a secreted protein that activates Wnts.Soluble hyaluronans,0.05%sodium hyaluronate,were used with DPM to expand monolayer cultures.Expansion of organoids was achieved by using DPM in combination with embedding organoids in Matrigel that was replaced with a defined thiol-hyaluronan triggered with PEGDA to form a hydrogel with a rheology[G*]of less than 100 Pa.The combination is called the BTSC-Expansion-Glycogel-System(BEX-gel system)for expanding BTSCs as a monolayer or as organoids.The BTSC organoids were expanded more than 3000-fold ex vivo in the BEX-gel system within 70 days while maintaining phenotypic traits indicative of stem/progenitors.Stem-cell-patch grafting of expanded BTSC organoids was performed on the livers of Fah-/-mice with tyrosinemia and resulted in the rescue of the mice and restoration of their normal liver functions.The BEX-gel system for BTSC organoid expansion provides a strategy to generate sufficient numbers of organoids for the therapeutic treatments of liver diseases.
文摘Collaborative forest management (CFM) is a form of forest governance in which local communities are involved in the management and decision-making processes related to forest resources. It is believed that forests under such management are better in tree diversity and conservation status and thus hold more carbon stocks. The study assessed the impact of CFM on carbon stocks, tree species diversity & tree species density in Mabira Central Forest Reserve. Data were collected from plots that were systematically laid in the different purposively selected forest areas. The study findings show that there is no difference in stem density and carbon stocks between CFM and non-CFM areas. CFM areas had lower species richness compared to non-CFM areas. CFM areas, however, exhibited more species diversity than non-CFM areas. Climax colonization may favor a few dominant species over others, hence lowering species diversity despite the number of species being many in the understory, hence at the same time increasing species richness. Likewise, disturbance in CFM area may affect natural colonization and favor the emergency of many species either naturally or through assisted regeneration by reforestation, hence increasing diversity, whereas artificial selection of preferred species through harvesting may lower species richness, as observed. Recommendations for improving collaborative forest management (CFM) areas include implementing targeted interventions to enhance carbon sequestration, such as promoting reforestation and afforestation with high-carbon-storing species and strengthening monitoring and evaluation frameworks to assess carbon stock changes over time. Additionally, efforts should focus on enhancing biodiversity conservation by implementing more stringent protection measures and reducing human disturbance while encouraging community participation in biodiversity monitoring and conservation education.
基金supported by a grant from the National Key Technology Research and Development Program of the Ministry of Science and Technology of China,No.2014BAI01B00
文摘Neural stem cells promote neuronal regeneration and repair of brain tissue after injury,but have limited resources and proliferative ability in vivo.We hypothesized that nerve growth factor would promote in vitro proliferation of neural stem cells derived from the tree shrews,a primate-like mammal that has been proposed as an alternative to primates in biomedical translational research.We cultured neural stem cells from the hippocampus of tree shrews at embryonic day 38,and added nerve growth factor（100 μg/L） to the culture medium.Neural stem cells from the hippocampus of tree shrews cultured without nerve growth factor were used as controls.After 3 days,fluorescence microscopy after DAPI and nestin staining revealed that the number of neurospheres and DAPI/nestin-positive cells was markedly greater in the nerve growth factor-treated cells than in control cells.These findings demonstrate that nerve growth factor promotes the proliferation of neural stem cells derived from tree shrews.
文摘Let T be a tree. The set of leaves of Τ is denoted by Leaf(Τ). The subtree Τ—Leaf(Τ) of T is called the stem of Τ. A stem is called a k-ended stem if it has at most k-leaves in it. In this paper, we prove the following theorem. Let G be a connected graph and k≥2 be an integer. Let u and ν be a pair of nonadjacent vertices in G. Suppose that |NG(u)∪NG(v)|≥|G|-k-1. Then G has a spanning tree with k-ended stem if and only if G+uv has a spanning tree with k-ended stem. Moreover, the condition on |NG(u)∪NG(v)| is sharp.
基金the Korea Forest Service for funding this research(Project No.S211316L020130)
文摘In this study, compatible taper and stem volume equations were developed for Larix kaempferi species of South Korea. The dataset was split into two groups： 80% of the data were used in model fitting and the remaining 2o% were used for validation. The compatible MB76 equations were used to predict the diameter outside bark to a specific height, the height to a specific diameter and the stem volume of the species. The result of the stem volume analysis was compared with the existing stem volume model of Larix kaempferi species of South Korea which was developed by the Korea Forest Research Institute and with a simple volume model that was developed with fitting dataset in this study. The compatible model provided accurate prediction of the total stem volume when compared to the existing stem volume model and with a simple volume model. It is concluded that the compatible taper and stem volume equations are more convenient to use and therefore it is recommended to be applied in the Larix kaempferi species of South Korea.
基金funded by the National Natural Science Foundation of China (40971032, 91125026)
文摘High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.
文摘The development of equations to predict tree height, crown diameter, crown depth from stem diameter of a tree species enables arborists, researchers, and urban forest managers to model costs and benefits, analyze alternative management scenarios, and determine the best management practices for sustainable forests. The objective of this study was to develop regression prediction models for tree age, tree height, crown diameter, crown ratio and crown depth for A. senegal growing in Ferlo, in the northern Senegal. Four plantations of different years old (ISRA, 10 years old plantations, Ndodj, 8 years old plantations, Boulal, 5 years old plantations and Déali, 4 years old plantations) were selected. The following dendometric variables: crown height, crown diameter, stem diameter at the breast height, stem basal diameter (at 0.30 m) and the height from the tree base to first branch were measured on a total of 489 trees. The results suggested that the ecological structure of the different year old A. Senegal plantation revealed a bell-shaped form with left dissymmetric distribution indicating a predominance of individuals with small diameter at breast height. Allometry study of A. Senegal showed highly significant positive correlations (p = 0.00) between stem diameter at breast height, stem basal diameter, tree height, crown diameter and crown depth. Positive correlations were also found between crown diameter, tree height and crown height. Prediction models derived from these relationships can be used to estimate the tree height, stem diameter at breast height and crown depth from crown diameter with greater precision. As for A. Senegal age estimation, the established model is not strong as it can explain only 49.1% of the age variation.
