Hai Ren

Global variation in elevational diversity patterns

While horizontal gradients of biodiversity have been examined extensively in the past, vertical diversity gradients (elevation, water depth) are attracting increasing attention. We compiled data from 443 elevational gradients involving diverse organisms worldwide to investigate how elevational diversity patterns may vary between the Northern and Southern hemispheres and across latitudes. Our results show that most elevational diversity curves are positively skewed (maximum diversity below the middle of the gradient) and the elevation of the peak in diversity increases with the elevation of lower sampling limits and to a lesser extent with upper limit. Mountains with greater elevational extents, and taxonomic groups that are more inclusive, show proportionally more unimodal patterns whereas other ranges and taxa show highly variable gradients. The two hemispheres share some interesting similarities but also remarkable differences, likely reflecting differences in landmass and mountain configurations. Different taxonomic groups exhibit diversity peaks at different elevations, probably reflecting both physical and physiological constraints.

Wild Plant Species with Extremely Small Populations Require Conservation and Reintroduction in China

For reintroduction of rare and endangered plants, plants protected and propagated via ex situ conservation are returned to their original natural and semi-natural ecosystems or to suitable wild habitats. The goal is to establish a population with sufficient numbers and genetic resources to enable it to adapt to change and to be self-sustaining and self-renewing (Griffith et al. 1989; IUCN 1998). International organizations have also published guidelines for the reintroduction of wild species, and at least 249 reintroduction trials involving 172 taxa have been conducted worldwide (Godefroid et al. 2011). More than 890 papers related to reintroduction have been published (Polak and Saltz 2011). To date, there have been 62 successful reintroduction cases in the world (Albrecht et al. 2011). Based on ex situ conservation and research on threatened plants, China has performed several reintroduction experiments. Until now, 38 plant species have been successfully reintroduced. Reintroduced herbs include Primulina tabacum, Paphiopedilum wardii, Paphiopedilum armeniacum, Paraisometrum mileense, Tigridiopalma magnifica, Metabriggsia ovalifolia, Paphiopedilum malipoense, and Doritis pulcherrima. Reintroduced shrubs include Myricaria laxiflora (Chen et al. 2005), Loropetalum subcordatum, and Cycas debaoensis (Ren et al. 2008). Reintroduced trees include Disanthus cercidifolius subdp longipes, Nageia nagi, Manglietia longipedunculata, Bretschneidara sinensis, Parakmeria lotungensis, Davidia involucrate, Dipteronia sinensis, Lirianthe odoratissima, Manglietia aromatica, Euryodendron excelsum, Formanodendron doichangensis, Pachylarnax sinica, Cyclobalanopsis sichourensis, Nyssa yunnanensis, and Diploknema yunnanensis (Sun et al. 2006; Zheng and Sun 2009). The lower plant Adiantum reniforme. var. sinense has also been successfully reintroduced (Ren 2012). The reintroduction of plant species with extremely small populations in China involves a number of main features and problems. Botanical gardens play an important role in the early stage of wild plant reintroduction because such gardens research introduction techniques are related to ex situ conservation. The government is important because it promotes interactions with international organizations and it develops and implements the relevant laws and regulations. For example, the State Forestry Administration approved the “Implementation Plan for Saving Wild Plants of Extremely Small Populations” in 2012; Botanical Garden Conservation International launched a “10 species program” in China aiming at insuring species survival and population recovery. Those works are conducted mainly in relatively developed areas, such as Guangdong and Zhejiang provinces, or biodiversity-rich regions (such as Yunnan province), and over a short period of time, but few related papers have been published. The plant species that have been systematically studied include Primulina tabacum, Tigridiopalma magnifica, Bretschneidara sinensis, Pachylarnax sinica, and Cyclobalanopsis sichourensis. The species that have been reintroduced are confined to those in single-species families and genera, and relic species or rare and endangered species. With respect to the reintroduction of wild plants, researchers in China have studied the ecological characteristics, population genetics, and breeding biology of 28 species. The research has confirmed that these species have narrow distribution areas and shrinking population sizes related to anthropogenic disturbance and climate change. Primulina tabacum, Tigridiopalma magnifica, and Cycas changjiangensis have had 3, 1, and 2 wild distribution points (populations), respectively, that became extinct in the past decade (Ren et al. 2010, 2012). The genetic diversity of these plants is generally low. These plants have varying degrees of natural reproduction barriers (Jian et al. 2010). To increase the successful reintroduction of rare and endangered species, researchers have combined methods of biotechnology and ecological restoration. Our investigations showed that reintroduction of Primulina tabacum often required the use of bryophytes as nurse plants (Ren et al. 2010). Successful reintroduction of Tigridiopalma magnifica indicated that rare and endangered species can be transplanted and established with anthropogenic assistance under the conditions of global climate change, which clarified current academic debate (Ren et al. 2012). We have also successfully reintroduced some trees (including species of Magnoliaceae) and produced substantial numbers of plants from seeds. Some of these seedlings have been used for urban landscaping. Most importantly, we have established the following protocol for the reintroduction of rare and endangered plants: first, select the appropriate target plant species; second, conduct basic research on their breeding and other aspects of their biology and ecology; and then, reintroduce them to the wild while also developing their market-oriented production. By consulting with regional and national agencies concerned with ecological planning, we have promoted this protocol for the reintroduction of rare and endangered plants throughout China.

Natural recovery of different areas of a deserted quarry in South China

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.

Interpopulation congruence in Chinese Primula ovalifolia revealed by chemical and molecular markers using essential oils and ISSRs.

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. ovalifolia revealed by the chemical and molecular markers

The role of salicylic acid in response of two rice cultivars to chilling stress

Two rice (Oryza sativa L.) cultivars differing in chilling sensitivity, Changbaijiu (chilling-tolerant) and Zhongjian (chilling-sensitive) were pre-treated with 0.5, 1.0 and 2.0 mM salicylic acid (SA) for 24 h before chilling at 5°C for 1 d. Chilling induced SA accumulation, particularly conjugated SA in both leaves and roots of the two rice cultivars. After SA administration, SA accumulated in the roots of both cultivars at a concentration-dependent manner, whereas only a slight increase was observed in their leaves. Conjugated SA accounted for most of the increase. The beneficial effect of SA treatment on protecting rice seedlings from chilling injury was not observed at any concentration in either cultivar. Pre-treatment with SA even decreased their chilling tolerance confirmed by increased electrolyte leakage and lipid peroxidation. Further, most of the activities of antioxidant enzymes decreased or remained unchanged in leaves and roots of SA pre-treated seedlings after chilling. These results implied that down-regulation of antioxidant defence might be involved in the reduction of chilling tolerance in SA-pre-treated plants.

Direct somatic embryogenesis and shoot organogenesis from leaf explants of Primulina tabacum

AbstractsAn efficient propagation system via somatic embryogenesis and shoot organogenesis and plant regeneration system for endangered species Primulina tabacum Hance was established. Thidiazuron (TDZ) was the key plant growth regulator for inducing somatic embryogenesis and kinetin (KIN) and 6-benzylaminopurine (BAP) were the key cytokinins for inducing shoot organogenesis from leaf explants. TDZ combined with BAP or KIN in the induction Murashige and Skoog medium induced both somatic embryos and adventitious shoots. Leaf explants with abaxial site in contact with the medium induced less somatic embryos or adventitious shoots compared to inversely placed leaf explants and the optimum pH was 6.5–7.0. Secondary somatic embryos or adventitious shoot could be induced from primary somatic embryos using TDZ and BAP. Shoots developed adventitious roots on rooting medium containing 0.5 μM indole-3-butyric acid and 0.2 % activated carbon. Over 90 % of plantlets survived following acclimatization and transfer to potting mixture (sand:Vermiculite:limestone; 1:2:1).

Estimating Change in Sedimentary Organic Carbon Content During Mangrove Restoration in Southern China Using Carbon Isotopic Measurements

Abstract Based on total carbon (C) and C isotopes in sediment cores, sedimentary organic carbon (SOC) was quantified in three types of mangrove sites (barren flat sites without mangroves, mangrove plantations, and natural mangrove forests), which were considered to represent a continuum from least restored to most restored sites in southern China. SOC densities in the barren sites, plantations, and natural forests were 90, 170 and 288 Mg ha −1 , respectively. We inferred that mangrove restoration increased SOC accumulation in coastal areas. At 0–70 cm depth, SOC δ 13 C values in both mangrove sites ranged from −27.37‰ to −23.07‰ and exhibited gradual enrichment with depth. In contrast, the values in the barren flat sites remained around −22.19‰ and fluctuated slightly with depth. At 0–60 cm, the 14 C ages of the SOC in the barren flat site, the natural mangrove site, and the artificial mangrove site ranged from 1 397 to 2 608, 255 to 2 453, and 391 to 2 512 years BP, respectively. In both types of mangrove sites but not in the barren flat sites, the enrichment of δ 13 C with depth was related to increases in SOC decay and SOC age with depth. According to analysis of 14 C age, much of the mangrove-derived C was transported and stored at 0–60 cm depth under anaerobic conditions in both mangrove sites. The sediments of mangrove forests in southern China sequester large quantities of SOC during mangrove restoration.

Modeling Productivity in Mangrove Forests as Impacted by Effective Soil Water Availability and Its Sensitivity to Climate Change Using Biome-BGC

Ecosystem dynamics and the responses to climate change in mangrove forests are poorly understood. We applied the biogeochemical process model Biome-BGC to simulate the dynamics of net primary productivity (NPP) and leaf area index (LAI) under the present and future climate conditions in mangrove forests in Shenzhen, Zhanjiang, and Qiongshan across the southern coast of China, and in three monocultural mangrove stands of two native species, Avicennia marina and Kandelia obovata, and one exotic species, Sonneratia apetala, in Shenzhen. The soil hydrological process of the model was modified by incorporating a soil water (SW) stress index to account for the impact of the effective SW availability in the coastal wetland. Our modified Biome-BGC well predicted the dynamics of NPP and LAI in the mangrove forests at the study sites. We found that the six mangrove systems differed in sensitivity to variations in the effective SW availability. At the ecosystem level, however, soil salinity alone could not entirely explain the limitation of the effective SW availability on the productivity of mangrove forests. Increasing atmospheric CO2 concentration differentially affected growth of different mangrove species but only had a small impact on NPP (<7%); whereas a doubling of atmospheric CO2 concentration associated with a 2°C temperature rise would increase NPP by 14–19% across the three geographically separate mangrove forests and by 12% to as much as 68% across the three monocultural mangrove stands. Our simulation analysis indicates that temperature change is more important than increasing CO2 concentration in affecting productivity of mangroves at the ecosystem level, and that different mangrove species differ in sensitivity to increases in temperature and CO2 concentration.

Near Isometric Biomass Partitioning in Forest Ecosystems of China

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.

Characteristics of sun- and shade-adapted populations of an endangered plant Primulina tabacum Hance

Primulina tabacum Hance is an endangered perennial herb distributed in calcium-rich and nitrogen-limited soil of the karst limestone areas in southern China. The morphological, ultrastructural, and physiological traits were determined for P. tabacum populations growing in three different environment conditions: twilight zone of a cave (site TZ, extremely low light intensity), at a cave entrance (site EZ, low light intensity), and in an open area (site OA, high light intensity). At site OA, P. tabacum plants were exposed to high light (635 μmol m−2 s−1 of mean daily photosynthetically active radiation) with drought stress, and expressed traits to minimize light capture and water loss. Compared to plants at sites EZ and TZ, those at site OA had thicker leaves with higher densities of stomata and pubescence, higher palisade/spongy ratio, higher light-saturated rate of net photosynthetic rate (Pmax), higher biomass, higher non-photochemical quenching coefficient (NPQ), and higher light saturation point (LSP) but fewer grana per chloroplast and less thylakoid stacking per granum. In contrast, P. tabacum growing at the cave vicinities: EZ (mean daily irradiance 59 μmol m−2 s−1) and TZ (mean daily irradiance 11 μmol m−2 s−1) showed typical shade-adapted characteristics for optimum light capture. The presence of sun- and shade-adapted characteristics indicates that P. tabacum has different strategies to cope with different environments but whether these strategies reflect genetic selection or phenological plasticity is yet to be determined. Such variability in physiological and morphological traits is important for the survival of P. tabacum in heterogeneous light conditions.