The bio-thermodynamic structures of a mixed native species plantation, a conifer plantation and a... more The bio-thermodynamic structures of a mixed native species plantation, a conifer plantation and an Acacia mangium plantation in Southern China were quantified over a period of 15 years based on eco-exergy methods. The efficiencies of structural development and maintenance were quantified through an integrated application of eco-exergy and emergy methods. The results showed that the storage of eco-exergy increased over 3 times in all three plantations, as predicted by the maximum eco-exergy principle. This trend was primarily seen due to the accumulation of biomass, instead of an increase in the specific eco-exergy (eco-exergy per unit biomass), although species richness did increase. The eco-exergy to emergy and eco-exergy to empower ratios of the three plantations generally increased during the study period, but the rate of increase slowed down after 20 years. The dominant trees are the largest contributors to the eco-exergy stored in the plantations, and thus, the introduction of ...
Conservation biology : the journal of the Society for Conservation Biology, Jan 15, 2015
We assessed the current status of plant conservation translocation efforts in China, a topic poor... more We assessed the current status of plant conservation translocation efforts in China, a topic poorly reported in recent scientific literature. We identified 222 conservation translocation cases involving 154 species, of these 87 were Chinese endemic species and 101 (78%) were listed as threatened on the Chinese Species Red List. We categorized the life form of each species and, when possible, determined for each case the translocation type, propagule source, propagule type, and survival and reproductive parameters. A surprisingly large proportion (26%) of the conservation translocations in China were conservation introductions, largely implemented in response to large-scale habitat destruction caused by the Three-Gorge Dam and another hydropower project. Documentation and management of the translocations varied greatly. Less than half the cases had plant survival records. Statistical analyses showed that survival percentages were significantly correlated with plant life form and the ...
Abstract The total area of China is about 9.6 million km2. Among the terrestrial ecosystems, crop... more Abstract The total area of China is about 9.6 million km2. Among the terrestrial ecosystems, cropland area is about 1.33 billion ha, 78% of which is degraded land; forestland area is about 1.75 billion ha, 72% of which is forest deterioration; grassland area is 3.99 billion ha, 90% of which ...
ABSTRACT There are five wild populations of Cycas fairylakea in Guangdong Province, China, three ... more ABSTRACT There are five wild populations of Cycas fairylakea in Guangdong Province, China, three of which are newly found. A study of the biological characteristics of C. fairylakea populations showed that this species had a narrow colonization area within 300 hm2, and an island pattern of distribution. Because of the overexploitation, urbanization, environment pollution, plant diseases, and insect pests, the wild populations and individuals of C. fairylakea decreased markedly in the past decades. All five populations have an opposite pyramid age structure, few coning plants, few seed production, and low level of seed germination rate or sterility. In conclusion, C. fairylakea in Guangdong Province was threatened seriously and an urgent need to take effective efforts to protect the plants and habitats in its location sites was required.
Establishing seedlings in subtropical plantations is very important for forest health, succession... more Establishing seedlings in subtropical plantations is very important for forest health, succession and management. Information on seedling nutrient concentrations is essential for both the selection of suitable indigenous tree species to accelerate succession of the established plantation and sustainable forest management. In this study, we investigated the concentrations of nitrogen ([N]), phosphorus ([P]), and N:P ratio in leaves, stems and roots of seedlings of three indigenous tree species (Castanopsis chinensis, Michelia chapensis and Psychotria rubra) transplanted with removing or retaining understory vegetation and litter at two typical subtropical forest plantations (Eucalyptus plantation and native species plantation). We also measured the relative growth rate (RGR) of seedling height, and developed the relationships between RGR and leaf [N], [P] and N:P ratio. Results showed that treatments of understory vegetation and associated litter (i.e. removal or retained) generally ...
Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with... more Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with aboveground biomass (MA) and the scaling exponent should not vary with environmental factors. We tested this hypothesis using a large forest biomass database collected in China. Allometric scaling functions relating MB and MA were developed for the entire database and for different groups based on tree age, diameter at breast height, height, latitude, longitude or elevation. To investigate whether the scaling exponent is independent of these biotic and abiotic factors, we analyzed the relationship between the scaling exponent and these factors. Overall MB was significantly related to MA with a scaling exponent of 0.964. The scaling exponent of the allometric function did not vary with tree age, density, latitude, or longitude, but varied with diameter at breast height, height, and elevation. The mean of the scaling exponent over all groups was 0.986. Among 57 scaling relationships devel...
Zeitschrift für Naturforschung. C, Journal of biosciences
The chemical composition of the essential oils of five natural populations of P. ovalifolia from ... more The chemical composition of the essential oils of five natural populations of P. ovalifolia from central and southwest China and their interpopulation variability were first analyzed by using GC-MS. Twenty-two essential oil compounds were obtained, in which eighteen ones were identified and characterized representing 95%-96% of the oil composition. Three main chemotypes, i.e., the methyl-acetyl-hydroquinone-rich, hydroquinone-rich, and acetyl-hydroquinone-rich chemotypes, were then differentiated, corresponding to the three groups obtained from the cluster analysis based on the essential oil composition percentages. Genetic variations among the five populations were also investigated using the Inter-Simple Sequence Repeats (ISSR) markers. Finally, the Mantel test showed that there was a significant correlation between two distance matrices based on the chemical compounds of essential oils and ISSR markers, confirming the congruence of interpopulation relationships in the P. ovalifol...
The distribution of the rare and endangered perennial herb Primulina tabacum Hance is restricted ... more The distribution of the rare and endangered perennial herb Primulina tabacum Hance is restricted to eight karst caves in southern China. To conserve P. tabacum and to evaluate possible reintroduction, we studied its historical distribution and conducted field surveys of both its biotic and physical environment. We used detrended correspondence analysis and canonical correspondence analysis to investigate the plant community structure and to identify the major environmental factors associated with its presence at eight sites and absence from three other sites where it formerly grew. The results revealed differences in community structure among sites and close correlations between species composition and environmental conditions. The data indicate that P. tabacum has special ecological requirements, including alkaline soil, low soil content of N, P, K and organic matter, low light, a high soil water content and high relative humidity, and a high atmospheric CO2 concentration. Soil K content, relative humidity and atmospheric CO2 concentration were the three variables most strongly associated with the vegetation composition and structure of the 11 sites. It appears that as a result of reductions in humidity, some of the historical localities of P. tabacum may no longer be suitable for reintroduction. Pilea notata, Pteris cretica var. nervosa and two moss species, Heteroscyphus coalitus and Gymnostomiella longinervis, were strongly associated with P. tabacum. The first two plants could be useful as indicators of suitable environments for P. tabacum, and the moss species could be useful as nurse plants for the reintroduction of P. tabacum into wild habitats.
Tropical forests continue to vanish rapidly, but few long-term studies have ever examined if and ... more Tropical forests continue to vanish rapidly, but few long-term studies have ever examined if and how the lost forests can be restored. Based on a 45-year restoration study in south China, we found that a tropical rain forest, once completely destroyed, could not recover naturally without deliberate restoration efforts. We identified two kinds of thresholds that must be overcome with human ameliorative measures before the ecosystem was able to recover. The first threshold was imposed primarily by extreme physical conditions such as exceedingly high surface temperature and impoverished soil, while the second was characterized by a critical level of biodiversity and a landscape context that accommodates dispersal and colonization processes. Our three treatment catchments (un-restored barren land, single-species plantation, and mixed-forest stand) exhibited dramatically different changes in biodiversity and ecosystem functioning over 4 decades. The mixed forest, having the highest level of biodiversity and ecosystem functioning, possesses several major properties of tropical rain forest. These findings may have important implications for the restoration of many severely degraded or lost tropical forest ecosystems. rainforest restoration, biodiversity conservation, ecosystem functioning, China
Plantations cover large areas in many countries, and the enhancement of plantation biodiversity i... more Plantations cover large areas in many countries, and the enhancement of plantation biodiversity is an increasingly important ecological concern. Many studies have demonstrated that overstory composition is important because it influences understory regeneration. To compare the understory vegetation and analyze its determinant factors, six typical plantations in South China were investigated: Acacia mangium plantation, Schima superba plantation, Eucalyptus citriodora plantation, E. exserta plantation, mixed-coniferous plantation, and mixed native species plantation. The results show that native species plantations shaded out more grasses and herbs than exotic spe-cies plantations, mixed-species plantations recruited more understory species than monoculture plantations, the leguminous species plantation had higher soil nitrogen than nonleguminous species plantations, and understory vegetation in the mixed-coniferous plantation was similar to that of mixed, native broadleaf species plantation. Although light is the crucial environmental factor affecting the understory community and diversity among the 14 measured factors, other environmental variables such as soil nutrients and soil moisture are also important.
Nurse plants are those that facilitate the growth and development of other plant species (target ... more Nurse plants are those that facilitate the growth and development of other plant species (target species) beneath their canopy because they offer benign microhabitats that are more favorable for seed germination and/or seedling recruitment than their surrounding environment. Nurse plants have been mainly used to restore vegetation in arid and sub-arid zones in recent years. Based on summarizing the definition of nurse plant and target plant, we review the nursing effect mechanisms, ecological factors that influence nursing effect, relationships between nurse plant and ecological restoration. This review also brings forward possible pairs of nurse and target species at lower subtropical areas. Furthermore, we provide the potential tendency in nurse plant research and application.
Establishing seedlings in subtropical plantations is very important for forest health, succession... more Establishing seedlings in subtropical plantations is very important for forest health, succession and management. Information on seedling nutrient concentrations is essential for both the selection of suitable indigenous tree species to accelerate succession of the established plantation and sustainable forest management. In this study, we investigated the concentrations of nitrogen ([N]), phosphorus ([P]), and N:P ratio in leaves, stems and roots of seedlings of three indigenous tree species (Castanopsis chinensis, Michelia chapensis and Psychotria rubra) transplanted with removing or retaining understory vegetation and litter at two typical subtropical forest plantations (Eucalyptus plantation and native species plantation). We also measured the relative growth rate (RGR) of seedling height, and developed the relationships between RGR and leaf [N], [P] and N:P ratio. Results showed that treatments of understory vegetation and associated litter (i.e. removal or retained) generally had no significant effects on leaf [N], [P], N:P ratio and RGR of the transplanted tree seedlings for the experimental period. But among different species, there were significant differences in nutrient concentrations. M. chapensis and P. rubra had higher [N] and [P] compared to C. chinensis. [N] and [P] also varied among different plant tissues with much higher values in leaves than in roots for all indigenous species. RGR of indigenous tree seedlings was mostly positively correlated with leaf [N] and [P], but negatively correlated with leaf N:P ratio. Considering the low [P] and high N:P ratio observed in the introduced indigenous tree seedlings, we propose that the current experimental plantations might be P limited for plant growth.
Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with... more Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with aboveground biomass (MA) and the scaling exponent should not vary with environmental factors. We tested this hypothesis using a large forest biomass database collected in China. Allometric scaling functions relating MB and MA were developed for the entire database and for different groups based on tree age, diameter at breast height, height, latitude, longitude or elevation. To investigate whether the scaling exponent is independent of these biotic and abiotic factors, we analyzed the relationship between the scaling exponent and these factors. Overall MB was significantly related to MA with a scaling exponent of 0.964. The scaling exponent of the allometric function did not vary with tree age, density, latitude, or longitude, but varied with diameter at breast height, height, and elevation. The mean of the scaling exponent over all groups was 0.986. Among 57 scaling relationships developed, 26 of the scaling exponents were not significantly different from 1. Our results generally support the isometric hypothesis. MB scaled near isometrically with MA and the scaling exponent did not vary with tree age, density, latitude, or longitude, but increased with tree size and elevation. While fitting a single allometric scaling relationship may be adequate, the estimation of MB from MA could be improved with size-specific scaling relationships.
The rare and endangered plant Primulina tabacum is a calciphilous perennial herb found only at th... more The rare and endangered plant Primulina tabacum is a calciphilous perennial herb found only at the entrances of a small number of karst cave drainages in southern China. In a conservation effort, we identified potentially suitable habitats and reintroduced P. tabacum plantlets (propagated in vitro) to one historical and two new cave entrances. The transplanted seedlings survived (10%) at only one new location where a moss, Gymnostomiella longinervis Broth, existed. Our field observations indicate that it is probably impossible for this rare plant to naturally recolonize the places where it went extinct because the habitats have changed. Transplanted P. tabacum grew slower than wild P. tabacum. The transplanted P. tabacum performed especially well under the cover of the nursing moss. Positive interactions between species, i.e., nurse plant effects, are important for reintroduction of success. Although light and soil conditions also appeared to be critical for transplantation success, the presence of moss should be considered as a useful and convenient indicator of suitable habitat for P. tabacum. This study case suggests that the use of new propagation methods and nurse plants can facilitate the reintroduction of rare and endangered herbs.
Abstract The objectives of this study were to examine plant biomass accumulation and carbon (C) s... more Abstract The objectives of this study were to examine plant biomass accumulation and carbon (C) storage in four different aged Sonneratia apetala plantations in the Leizhou Bay in South China. The allometric equations using diameter at breast height (DBH) and ...
Seed limitation of desired indigenous species has constrained the succession of established plant... more Seed limitation of desired indigenous species has constrained the succession of established plantations from an early successional stage, to more natural forests in South China. Because of its low cost and time-saving advantages, direct seeding has been considered a useful method in forest regeneration. To improve our understanding of whether and how direct seeding can lead to the establishment of indigenous tree species, we carried out an experiment in four typical plantations (eucalyptus, mixed-native, mixed-legume, mixed-conifer) and a shrubland in South China. We also tested the effect of understory vegetation and litter removal on seedling establishment and growth. Seeds of three indigenous tree species (Castanopsis chinensis, Cryptocarya chinensis, and Psychotria rubra) were sown with understory vegetation and litter either retained or removed. Seedling emergence, survival, and growth were recorded for 21 months. We found that conditions that favored seedling emergence often differed from those that favored seedling survival. While the removal of understory vegetation and litter did not influence the final seedling establishments for all the three introduced species, growth of Psychotria rubra was influenced at several sites. Seed mass was positively correlated with seedling emergence and subsequent growth. The large-seeded Castanopsis chinensis showed higher emergence and growth than the intermediate-seeded Cryptocarya chinensis or the smallseeded Psychotria rubra. Seedlings of Castanopsis chinensis grew better in plant communities with high understory light penetration and high soil exchangeable potassium. Growth of P. rubra seedlings decreased significantly with soil hydrolyzed nitrogen. In conclusion, direct seeding can be useful for the establishment of indigenous tree species into plantations and shrubland. Optimizing early seedling establishment and growth will require the selection of suitable native species for improving seedling establishment in different plantations. Additionally, understory vegetation and litter and fertilizer should be properly managed to enhance the establishment of certain indigenous tree species.
Case studies on Poisson lognormal distribution of species abundance have been rare, especially in... more Case studies on Poisson lognormal distribution of species abundance have been rare, especially in forest communities. We propose a numerical method to fit the Poisson lognormal to the species abundance data at an evergreen mixed forest in the Dinghushan Biosphere Reserve, South China. Plants in the tree, shrub and herb layers in 25 quadrats of 20 m×20 m, 5 m×5 m, and 1 m×1 m were surveyed. Results indicated that: (i) for each layer, the observed species abundance with a similarly small median, mode, and a variance larger than the mean was reverse J-shaped and followed well the zero-truncated Poisson lognormal; (ii) the coefficient of variation, skewness and kurtosis of abundance, and two Poisson lognormal parameters (σ and µ) for shrub layer were closer to those for the herb layer than those for the tree layer; and (iii) from the tree to the shrub to the herb layer, the σ and the coefficient of variation decreased, whereas diversity increased. We suggest that: (i) the species abundance distributions in the three layers reflects the overall community characteristics; (ii) the Poisson lognormal can describe the species abundance distribution in diverse communities with a few abundant species but many rare species; and (iii) 1/σ should be an alternative measure of diversity.
1] Predicted precipitation regime changes in arid ecosystems have the potential to alter soil C b... more 1] Predicted precipitation regime changes in arid ecosystems have the potential to alter soil C balance, but the influence of changes in different aspects of precipitation (amount, seasonality, and intensity) and the factors contributing to such effects are poorly understood. We used a process-based ecosystem model (PALS) that was modified, parameterized, and evaluated for a Mojave Desert ecosystem in the southwestern US to simulate how dryland soil respiration (R s ) and soil C pool size responded to precipitation changes at multiple temporal scales. The effects of changing precipitation on R s were largely mediated by the contrasting respiratory response of plants (R a ) and soil microbes (R h ) and confounded by predrought duration, season, soil temperature, plant phenology, and substrate availability. Increases in precipitation amount stimulated R s and increased the contribution of R a to R s , whereas reductions in summer rainfall and strong increases in rainfall event size reduced total R s and decreased the contribution of R a to R s . Increases in annual rainfall and decreases in summer rainfall benefited dryland soil C sequestration, whereas strong increases in rainfall event size resulted in a loss of soil C, with labile soil C pools being more responsive to precipitation regime changes than recalcitrant C pools at a decadal scale. These simulation results implied that dryland soils may act as C sinks with increased precipitation amount or C sources with decreased precipitation amount, but the strength of the sink/source may be mediated by accompanying shifts in rainfall seasonality and event size distribution.
A quarry is a surface mining operated place, which produces enormous quantities of gravel, limest... more A quarry is a surface mining operated place, which produces enormous quantities of gravel, limestone, and other materials for industrial and construction applications. Restoration and revegetation of deserted quarries are becoming increasingly important. Three areas of a typical quarry in South China: terrace for crushed materials (terrace), spoiled mound, and remaining side slope, were investigated, to compare the existing plant species and to study the relationship between environmental factors and revegetation. The plant species composition of these three areas was found to differ significantly after eight years of natural recovery. The typical plant communities found over them were composed of gramineous herbs, ferns, and shrubs. Soil organic matter, soil moisture, and soil bulk density were considered to be the major determining factors for vegetation succession. There existed abiotic and biotic thresholds during quarrying restoration. Suggestions had been presented that could have accelerated the process of natural recovery in quarries.
The bio-thermodynamic structures of a mixed native species plantation, a conifer plantation and a... more The bio-thermodynamic structures of a mixed native species plantation, a conifer plantation and an Acacia mangium plantation in Southern China were quantified over a period of 15 years based on eco-exergy methods. The efficiencies of structural development and maintenance were quantified through an integrated application of eco-exergy and emergy methods. The results showed that the storage of eco-exergy increased over 3 times in all three plantations, as predicted by the maximum eco-exergy principle. This trend was primarily seen due to the accumulation of biomass, instead of an increase in the specific eco-exergy (eco-exergy per unit biomass), although species richness did increase. The eco-exergy to emergy and eco-exergy to empower ratios of the three plantations generally increased during the study period, but the rate of increase slowed down after 20 years. The dominant trees are the largest contributors to the eco-exergy stored in the plantations, and thus, the introduction of ...
Conservation biology : the journal of the Society for Conservation Biology, Jan 15, 2015
We assessed the current status of plant conservation translocation efforts in China, a topic poor... more We assessed the current status of plant conservation translocation efforts in China, a topic poorly reported in recent scientific literature. We identified 222 conservation translocation cases involving 154 species, of these 87 were Chinese endemic species and 101 (78%) were listed as threatened on the Chinese Species Red List. We categorized the life form of each species and, when possible, determined for each case the translocation type, propagule source, propagule type, and survival and reproductive parameters. A surprisingly large proportion (26%) of the conservation translocations in China were conservation introductions, largely implemented in response to large-scale habitat destruction caused by the Three-Gorge Dam and another hydropower project. Documentation and management of the translocations varied greatly. Less than half the cases had plant survival records. Statistical analyses showed that survival percentages were significantly correlated with plant life form and the ...
Abstract The total area of China is about 9.6 million km2. Among the terrestrial ecosystems, crop... more Abstract The total area of China is about 9.6 million km2. Among the terrestrial ecosystems, cropland area is about 1.33 billion ha, 78% of which is degraded land; forestland area is about 1.75 billion ha, 72% of which is forest deterioration; grassland area is 3.99 billion ha, 90% of which ...
ABSTRACT There are five wild populations of Cycas fairylakea in Guangdong Province, China, three ... more ABSTRACT There are five wild populations of Cycas fairylakea in Guangdong Province, China, three of which are newly found. A study of the biological characteristics of C. fairylakea populations showed that this species had a narrow colonization area within 300 hm2, and an island pattern of distribution. Because of the overexploitation, urbanization, environment pollution, plant diseases, and insect pests, the wild populations and individuals of C. fairylakea decreased markedly in the past decades. All five populations have an opposite pyramid age structure, few coning plants, few seed production, and low level of seed germination rate or sterility. In conclusion, C. fairylakea in Guangdong Province was threatened seriously and an urgent need to take effective efforts to protect the plants and habitats in its location sites was required.
Establishing seedlings in subtropical plantations is very important for forest health, succession... more Establishing seedlings in subtropical plantations is very important for forest health, succession and management. Information on seedling nutrient concentrations is essential for both the selection of suitable indigenous tree species to accelerate succession of the established plantation and sustainable forest management. In this study, we investigated the concentrations of nitrogen ([N]), phosphorus ([P]), and N:P ratio in leaves, stems and roots of seedlings of three indigenous tree species (Castanopsis chinensis, Michelia chapensis and Psychotria rubra) transplanted with removing or retaining understory vegetation and litter at two typical subtropical forest plantations (Eucalyptus plantation and native species plantation). We also measured the relative growth rate (RGR) of seedling height, and developed the relationships between RGR and leaf [N], [P] and N:P ratio. Results showed that treatments of understory vegetation and associated litter (i.e. removal or retained) generally ...
Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with... more Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with aboveground biomass (MA) and the scaling exponent should not vary with environmental factors. We tested this hypothesis using a large forest biomass database collected in China. Allometric scaling functions relating MB and MA were developed for the entire database and for different groups based on tree age, diameter at breast height, height, latitude, longitude or elevation. To investigate whether the scaling exponent is independent of these biotic and abiotic factors, we analyzed the relationship between the scaling exponent and these factors. Overall MB was significantly related to MA with a scaling exponent of 0.964. The scaling exponent of the allometric function did not vary with tree age, density, latitude, or longitude, but varied with diameter at breast height, height, and elevation. The mean of the scaling exponent over all groups was 0.986. Among 57 scaling relationships devel...
Zeitschrift für Naturforschung. C, Journal of biosciences
The chemical composition of the essential oils of five natural populations of P. ovalifolia from ... more The chemical composition of the essential oils of five natural populations of P. ovalifolia from central and southwest China and their interpopulation variability were first analyzed by using GC-MS. Twenty-two essential oil compounds were obtained, in which eighteen ones were identified and characterized representing 95%-96% of the oil composition. Three main chemotypes, i.e., the methyl-acetyl-hydroquinone-rich, hydroquinone-rich, and acetyl-hydroquinone-rich chemotypes, were then differentiated, corresponding to the three groups obtained from the cluster analysis based on the essential oil composition percentages. Genetic variations among the five populations were also investigated using the Inter-Simple Sequence Repeats (ISSR) markers. Finally, the Mantel test showed that there was a significant correlation between two distance matrices based on the chemical compounds of essential oils and ISSR markers, confirming the congruence of interpopulation relationships in the P. ovalifol...
The distribution of the rare and endangered perennial herb Primulina tabacum Hance is restricted ... more The distribution of the rare and endangered perennial herb Primulina tabacum Hance is restricted to eight karst caves in southern China. To conserve P. tabacum and to evaluate possible reintroduction, we studied its historical distribution and conducted field surveys of both its biotic and physical environment. We used detrended correspondence analysis and canonical correspondence analysis to investigate the plant community structure and to identify the major environmental factors associated with its presence at eight sites and absence from three other sites where it formerly grew. The results revealed differences in community structure among sites and close correlations between species composition and environmental conditions. The data indicate that P. tabacum has special ecological requirements, including alkaline soil, low soil content of N, P, K and organic matter, low light, a high soil water content and high relative humidity, and a high atmospheric CO2 concentration. Soil K content, relative humidity and atmospheric CO2 concentration were the three variables most strongly associated with the vegetation composition and structure of the 11 sites. It appears that as a result of reductions in humidity, some of the historical localities of P. tabacum may no longer be suitable for reintroduction. Pilea notata, Pteris cretica var. nervosa and two moss species, Heteroscyphus coalitus and Gymnostomiella longinervis, were strongly associated with P. tabacum. The first two plants could be useful as indicators of suitable environments for P. tabacum, and the moss species could be useful as nurse plants for the reintroduction of P. tabacum into wild habitats.
Tropical forests continue to vanish rapidly, but few long-term studies have ever examined if and ... more Tropical forests continue to vanish rapidly, but few long-term studies have ever examined if and how the lost forests can be restored. Based on a 45-year restoration study in south China, we found that a tropical rain forest, once completely destroyed, could not recover naturally without deliberate restoration efforts. We identified two kinds of thresholds that must be overcome with human ameliorative measures before the ecosystem was able to recover. The first threshold was imposed primarily by extreme physical conditions such as exceedingly high surface temperature and impoverished soil, while the second was characterized by a critical level of biodiversity and a landscape context that accommodates dispersal and colonization processes. Our three treatment catchments (un-restored barren land, single-species plantation, and mixed-forest stand) exhibited dramatically different changes in biodiversity and ecosystem functioning over 4 decades. The mixed forest, having the highest level of biodiversity and ecosystem functioning, possesses several major properties of tropical rain forest. These findings may have important implications for the restoration of many severely degraded or lost tropical forest ecosystems. rainforest restoration, biodiversity conservation, ecosystem functioning, China
Plantations cover large areas in many countries, and the enhancement of plantation biodiversity i... more Plantations cover large areas in many countries, and the enhancement of plantation biodiversity is an increasingly important ecological concern. Many studies have demonstrated that overstory composition is important because it influences understory regeneration. To compare the understory vegetation and analyze its determinant factors, six typical plantations in South China were investigated: Acacia mangium plantation, Schima superba plantation, Eucalyptus citriodora plantation, E. exserta plantation, mixed-coniferous plantation, and mixed native species plantation. The results show that native species plantations shaded out more grasses and herbs than exotic spe-cies plantations, mixed-species plantations recruited more understory species than monoculture plantations, the leguminous species plantation had higher soil nitrogen than nonleguminous species plantations, and understory vegetation in the mixed-coniferous plantation was similar to that of mixed, native broadleaf species plantation. Although light is the crucial environmental factor affecting the understory community and diversity among the 14 measured factors, other environmental variables such as soil nutrients and soil moisture are also important.
Nurse plants are those that facilitate the growth and development of other plant species (target ... more Nurse plants are those that facilitate the growth and development of other plant species (target species) beneath their canopy because they offer benign microhabitats that are more favorable for seed germination and/or seedling recruitment than their surrounding environment. Nurse plants have been mainly used to restore vegetation in arid and sub-arid zones in recent years. Based on summarizing the definition of nurse plant and target plant, we review the nursing effect mechanisms, ecological factors that influence nursing effect, relationships between nurse plant and ecological restoration. This review also brings forward possible pairs of nurse and target species at lower subtropical areas. Furthermore, we provide the potential tendency in nurse plant research and application.
Establishing seedlings in subtropical plantations is very important for forest health, succession... more Establishing seedlings in subtropical plantations is very important for forest health, succession and management. Information on seedling nutrient concentrations is essential for both the selection of suitable indigenous tree species to accelerate succession of the established plantation and sustainable forest management. In this study, we investigated the concentrations of nitrogen ([N]), phosphorus ([P]), and N:P ratio in leaves, stems and roots of seedlings of three indigenous tree species (Castanopsis chinensis, Michelia chapensis and Psychotria rubra) transplanted with removing or retaining understory vegetation and litter at two typical subtropical forest plantations (Eucalyptus plantation and native species plantation). We also measured the relative growth rate (RGR) of seedling height, and developed the relationships between RGR and leaf [N], [P] and N:P ratio. Results showed that treatments of understory vegetation and associated litter (i.e. removal or retained) generally had no significant effects on leaf [N], [P], N:P ratio and RGR of the transplanted tree seedlings for the experimental period. But among different species, there were significant differences in nutrient concentrations. M. chapensis and P. rubra had higher [N] and [P] compared to C. chinensis. [N] and [P] also varied among different plant tissues with much higher values in leaves than in roots for all indigenous species. RGR of indigenous tree seedlings was mostly positively correlated with leaf [N] and [P], but negatively correlated with leaf N:P ratio. Considering the low [P] and high N:P ratio observed in the introduced indigenous tree seedlings, we propose that the current experimental plantations might be P limited for plant growth.
Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with... more Based on the isometric hypothesis, belowground plant biomass (MB) should scale isometrically with aboveground biomass (MA) and the scaling exponent should not vary with environmental factors. We tested this hypothesis using a large forest biomass database collected in China. Allometric scaling functions relating MB and MA were developed for the entire database and for different groups based on tree age, diameter at breast height, height, latitude, longitude or elevation. To investigate whether the scaling exponent is independent of these biotic and abiotic factors, we analyzed the relationship between the scaling exponent and these factors. Overall MB was significantly related to MA with a scaling exponent of 0.964. The scaling exponent of the allometric function did not vary with tree age, density, latitude, or longitude, but varied with diameter at breast height, height, and elevation. The mean of the scaling exponent over all groups was 0.986. Among 57 scaling relationships developed, 26 of the scaling exponents were not significantly different from 1. Our results generally support the isometric hypothesis. MB scaled near isometrically with MA and the scaling exponent did not vary with tree age, density, latitude, or longitude, but increased with tree size and elevation. While fitting a single allometric scaling relationship may be adequate, the estimation of MB from MA could be improved with size-specific scaling relationships.
The rare and endangered plant Primulina tabacum is a calciphilous perennial herb found only at th... more The rare and endangered plant Primulina tabacum is a calciphilous perennial herb found only at the entrances of a small number of karst cave drainages in southern China. In a conservation effort, we identified potentially suitable habitats and reintroduced P. tabacum plantlets (propagated in vitro) to one historical and two new cave entrances. The transplanted seedlings survived (10%) at only one new location where a moss, Gymnostomiella longinervis Broth, existed. Our field observations indicate that it is probably impossible for this rare plant to naturally recolonize the places where it went extinct because the habitats have changed. Transplanted P. tabacum grew slower than wild P. tabacum. The transplanted P. tabacum performed especially well under the cover of the nursing moss. Positive interactions between species, i.e., nurse plant effects, are important for reintroduction of success. Although light and soil conditions also appeared to be critical for transplantation success, the presence of moss should be considered as a useful and convenient indicator of suitable habitat for P. tabacum. This study case suggests that the use of new propagation methods and nurse plants can facilitate the reintroduction of rare and endangered herbs.
Abstract The objectives of this study were to examine plant biomass accumulation and carbon (C) s... more Abstract The objectives of this study were to examine plant biomass accumulation and carbon (C) storage in four different aged Sonneratia apetala plantations in the Leizhou Bay in South China. The allometric equations using diameter at breast height (DBH) and ...
Seed limitation of desired indigenous species has constrained the succession of established plant... more Seed limitation of desired indigenous species has constrained the succession of established plantations from an early successional stage, to more natural forests in South China. Because of its low cost and time-saving advantages, direct seeding has been considered a useful method in forest regeneration. To improve our understanding of whether and how direct seeding can lead to the establishment of indigenous tree species, we carried out an experiment in four typical plantations (eucalyptus, mixed-native, mixed-legume, mixed-conifer) and a shrubland in South China. We also tested the effect of understory vegetation and litter removal on seedling establishment and growth. Seeds of three indigenous tree species (Castanopsis chinensis, Cryptocarya chinensis, and Psychotria rubra) were sown with understory vegetation and litter either retained or removed. Seedling emergence, survival, and growth were recorded for 21 months. We found that conditions that favored seedling emergence often differed from those that favored seedling survival. While the removal of understory vegetation and litter did not influence the final seedling establishments for all the three introduced species, growth of Psychotria rubra was influenced at several sites. Seed mass was positively correlated with seedling emergence and subsequent growth. The large-seeded Castanopsis chinensis showed higher emergence and growth than the intermediate-seeded Cryptocarya chinensis or the smallseeded Psychotria rubra. Seedlings of Castanopsis chinensis grew better in plant communities with high understory light penetration and high soil exchangeable potassium. Growth of P. rubra seedlings decreased significantly with soil hydrolyzed nitrogen. In conclusion, direct seeding can be useful for the establishment of indigenous tree species into plantations and shrubland. Optimizing early seedling establishment and growth will require the selection of suitable native species for improving seedling establishment in different plantations. Additionally, understory vegetation and litter and fertilizer should be properly managed to enhance the establishment of certain indigenous tree species.
Case studies on Poisson lognormal distribution of species abundance have been rare, especially in... more Case studies on Poisson lognormal distribution of species abundance have been rare, especially in forest communities. We propose a numerical method to fit the Poisson lognormal to the species abundance data at an evergreen mixed forest in the Dinghushan Biosphere Reserve, South China. Plants in the tree, shrub and herb layers in 25 quadrats of 20 m×20 m, 5 m×5 m, and 1 m×1 m were surveyed. Results indicated that: (i) for each layer, the observed species abundance with a similarly small median, mode, and a variance larger than the mean was reverse J-shaped and followed well the zero-truncated Poisson lognormal; (ii) the coefficient of variation, skewness and kurtosis of abundance, and two Poisson lognormal parameters (σ and µ) for shrub layer were closer to those for the herb layer than those for the tree layer; and (iii) from the tree to the shrub to the herb layer, the σ and the coefficient of variation decreased, whereas diversity increased. We suggest that: (i) the species abundance distributions in the three layers reflects the overall community characteristics; (ii) the Poisson lognormal can describe the species abundance distribution in diverse communities with a few abundant species but many rare species; and (iii) 1/σ should be an alternative measure of diversity.
1] Predicted precipitation regime changes in arid ecosystems have the potential to alter soil C b... more 1] Predicted precipitation regime changes in arid ecosystems have the potential to alter soil C balance, but the influence of changes in different aspects of precipitation (amount, seasonality, and intensity) and the factors contributing to such effects are poorly understood. We used a process-based ecosystem model (PALS) that was modified, parameterized, and evaluated for a Mojave Desert ecosystem in the southwestern US to simulate how dryland soil respiration (R s ) and soil C pool size responded to precipitation changes at multiple temporal scales. The effects of changing precipitation on R s were largely mediated by the contrasting respiratory response of plants (R a ) and soil microbes (R h ) and confounded by predrought duration, season, soil temperature, plant phenology, and substrate availability. Increases in precipitation amount stimulated R s and increased the contribution of R a to R s , whereas reductions in summer rainfall and strong increases in rainfall event size reduced total R s and decreased the contribution of R a to R s . Increases in annual rainfall and decreases in summer rainfall benefited dryland soil C sequestration, whereas strong increases in rainfall event size resulted in a loss of soil C, with labile soil C pools being more responsive to precipitation regime changes than recalcitrant C pools at a decadal scale. These simulation results implied that dryland soils may act as C sinks with increased precipitation amount or C sources with decreased precipitation amount, but the strength of the sink/source may be mediated by accompanying shifts in rainfall seasonality and event size distribution.
A quarry is a surface mining operated place, which produces enormous quantities of gravel, limest... more A quarry is a surface mining operated place, which produces enormous quantities of gravel, limestone, and other materials for industrial and construction applications. Restoration and revegetation of deserted quarries are becoming increasingly important. Three areas of a typical quarry in South China: terrace for crushed materials (terrace), spoiled mound, and remaining side slope, were investigated, to compare the existing plant species and to study the relationship between environmental factors and revegetation. The plant species composition of these three areas was found to differ significantly after eight years of natural recovery. The typical plant communities found over them were composed of gramineous herbs, ferns, and shrubs. Soil organic matter, soil moisture, and soil bulk density were considered to be the major determining factors for vegetation succession. There existed abiotic and biotic thresholds during quarrying restoration. Suggestions had been presented that could have accelerated the process of natural recovery in quarries.
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