Browsing by Author "Stepp, John R."

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Biodiversity and Phytochemical Quality in Indigenous and State-Supported Tea Management Systems of Yunnan, China.
(2013-02) Ahmed, Selena; Peters, Charles M.; Chunlin, Long; Meyer, Rachel; Unachukwu, Uchenna J.; Litt, Amy; Kennelly, Edward J.; Stepp, John R.
The Chinese government initiated one of the world's largest conservation programs involving agricultural ecosystems with the implementation of the ‘Grain for Green’ (Tui Geng Huan Lin) forest policy between 1999 and 2003. This is the first study to systematically quantify multiple dimensions of biodiversity, phytochemical quality and economic benefits associated with (1) the Grain for Green's tea (Camellia sinensis; Theaceae) initiative; (2) the state's previous forest policy involving tea populations in protected areas and; (3) the indigenous tea agro‐ecosystems replaced or overlooked by this conservation program. There are several novel and unexpected findings. While forest populations contained the greatest ecological diversity, agro‐forests and mixed crop plots were associated with the greatest genetic diversity, phytochemical quality and economic benefits. Indigenous management practices should be incorporated into conservation in China in order to create policies that are more aligned towards biodiversity conservation and sustainable livelihoods while allowing local communities to maintain their cultural identity through agrarian practices.
Changes in Tea Plant Secondary Metabolite Profiles as a Function of Leafhopper Density and Damage
(2020-05) Scott, Eric R.; Li, Xin; Wei, Ji-Peng; Kfoury, Nicole; Morimoto, Joshua; Guo, Ming-Ming; Agyei, Amma; Robbat Jr., Albert; Ahmed, Selena; Cash, Sean B.; Griffin, Timothy S.; Stepp, John R.; Han, Wen-Yen; Orians, Colin M.
Insect herbivores have dramatic effects on the chemical composition of plants. Many of these induced metabolites contribute to the quality (e.g., flavor, human health benefits) of specialty crops such as the tea plant (Camellia sinensis). Induced chemical changes are often studied by comparing plants damaged and undamaged by herbivores. However, when herbivory is quantitative, the relationship between herbivore pressure and induction can be linearly or non-linearly density dependent or density independent, and induction may only occur after some threshold of herbivory. The shape of this relationship can vary among metabolites within plants. The tea green leafhopper (Empoasca onukii) can be a widespread pest on tea, but some tea farmers take advantage of leafhopper-induced metabolites in order to produce high-quality “bug-bitten” teas such as Eastern Beauty oolong. To understand the effects of increasing leafhopper density on tea metabolites important for quality, we conducted a manipulative experiment exposing tea plants to feeding by a range of E. onukii densities. After E. onukii feeding, we measured volatile and non-volatile metabolites, and quantified percent damaged leaf area from scanned leaf images. E. onukii density had a highly significant effect on volatile production, while the effect of leaf damage was only marginally significant. The volatiles most responsive to leafhopper density were mainly terpenes that increased in concentration monotonically with density, while the volatiles most responsive to leaf damage were primarily fatty acid derivatives and volatile phenylpropanoids/benzenoids. In contrast, damage (percent leaf area damaged), but not leafhopper density, significantly reduced total polyphenols, epigallocatechin gallate (EGCG), and theobromine concentrations in a dose-dependent manner. The shape of induced responses varied among metabolites with some changing linearly with herbivore pressure and some responding only after a threshold in herbivore pressure with a threshold around 0.6 insects/leaf being common. This study illustrates the importance of measuring a diversity of metabolites over a range of herbivory to fully understand the effects of herbivores on induced metabolites. Our study also shows that any increases in leafhopper density associated with climate warming, could have dramatic effects on secondary metabolites and tea quality.
Comparative homegarden medical ethnobotany of Naxi healers and farmers in Northwestern Yunnan, China
(2014-01) Yang, Lixin; Ahmed, Selena; Stepp, John R.; Mi, Kai; Zhao, Yanqiang; Ma, Junzeng; Liang, Chen; Pei, Shengji; Huai, Huyin; Xu, Gang; Hamilton, Alan C.; Yang, Zhi-wei; Xue, Dayuan
Background Homegardens are ecologically and culturally important systems for cultivating medicinal plants for wellbeing by healers and farmers in Naxi communities of the Sino Himalayan region. The cultivation of medicinal plants in Naxi communities and associated ethnomedical knowledge base for maintaining and utilizing these resources is at risk with expanded commercialization of natural resources, development policies and rapid socio-economic change in China. Research is needed to understand the medicinal plant species maintained in Naxi homegardens, their use and contribution to community wellbeing, and how these practices and knowledge base varies between Naxi healers and farmers in order to develop plans for biodiversity conservation and preservation of ethnomedical practices. The main objective of this study is to document and compare medicinal plant species in Naxi homegardens and associated ethnomedical knowledge between Naxi healers and farmers. Methods Ethnobotanical homegarden surveys were conducted with three Naxi healers and 28 farmer households in two Naxi communities in Lijiang Prefecture in Northwest Yunnan Province of China. Surveys included inventories of medicinal plants in homegardens and semi-structured interviews with homegarden managers to document traditional medicinal uses of inventoried plants. Inventoried plants were classified into 13 ‘usage categories’ of medical condition groupings that impact a system of the body. Finally, plant species richness was calculated for each homegarden and species richness was compared between healers and farmers as well as between study sites using a Least Square Means Tukey HSD function. Results Ethnobotanical surveys at the study sites found that 13% of households rely exclusively on traditional Naxi medicine, 26% exclusively use Western medicine and 61% use a combination of traditional Naxi and Western medicine. A total of 106 medicinal plants were inventoried in Naxi homegardens representing 50 botanical families. Over 85% of inventoried medicinal plants were herbaceous. The most represented families were Asteraceae (12.8%), Ranunculaceae (8.3%), Apiaceae (8.3%), and Polygonaceae (7.3%). The primary medical functions of inventoried plants were to treat inflammation (73 species), circulatory system disorders (62), nervous system disorders (41), detoxification (39), digestive system disorders (33), muscular-skeletal system disorders (26), genitourinary system disorders (26), skin conditions (23), respiratory systems disorders (22), and cold and flu (20). Local herbal experts maintained greater medicinal plant species richness in their homegardens compared to local farmers as well as had greater knowledge of medicinal functions of plants. Healers maintained medicinal plants primarily for healing while farmer households maintained approximately 90% of the medicinal plants in their homegardens for commercialization and the remaining for household healthcare. Conclusions This study highlights the importance of biodiversity and traditional ecological and medical knowledge for human wellbeing and livelihoods in Naxi communities. Conservation efforts and policies are necessary to preserve the ecological and cultural base that maintains medicinal plant use by both healers and farmers in Naxi homegardens of the Sino Himalayan region.
Cultural and Ecosystem Services of Flowering Quince (Chaenomeles speciosa) in the Naxi and Tibetan Highlands of NW Yunnan, China.
(2015-09) Yang, Lixin; Ahmed, Selena; Stepp, John R.; Zhao, Yanqinag; Zeng, Ma Jun; Pei, Shengji; Xue, Dayuan; Xu, Gang
Naxi, Tibetan, Bai, Yi, and Han communities in the Hengduan Mountain region of China’s western Yunnan have an extensive history of cultivating flowering quince (Chaenomeles speciosa [Sweet] Nakai; Rosaceae; Fig. 1). Flowering quince is cultivated and utilized by communities for food, medicine, and as a windbreak barrier and soil protector at the edges of their fields and gardens (Gao et al. 2011). The Hengduan Mountains are characterized by limited fertile land and cultivated fields that have relatively low productivity. Socio–linguistic groups living in the area for hundreds of years have developed ecological knowledge regarding suitable plants to cultivate in order to support community wellbeing in this extreme habitat. This study presents an ethnobotanical profile of flowering quince and seeks to understand the cultural and ecosystem services it provides to communities in the Hengduan Mountain region. The main objective of this study is to understand the rationale for its traditional cultivation and to explore the potential commercial value of flowering quince.
Effects of water availability and pest pressures on tea (Camellia sinensis) growth and functional quality
(2014-02) Ahmed, Selena; Orians, Colin M.; Griffin, Timothy S.; Buckley, Sarabeth; Unachukwu, Uchenna J.; Stratton, Anne E.; Stepp, John R.; Robbat, Albert Jr.; Cash, Sean; Kennelly, Edward J.
Extreme shifts in water availability linked to global climate change are impacting crops worldwide. The present study examines the direct and interactive effects of water availability and pest pressures on tea (Camellia sinensis; Theaceae) growth and functional quality. Manipulative greenhouse experiments were used to measure the effects of variable water availability and pest pressures simulated by jasmonic acid (JA) on tea leaf growth and secondary metabolites that determine tea quality. Water treatments were simulated to replicate ideal tea growing conditions and extreme precipitation events in tropical southwestern China, a major centre of tea production. Results show that higher water availability and JA significantly increased the growth of new leaves while their interactive effect was not significant. The effect of water availability and JA on tea quality varied with individual secondary metabolites. Higher water availability significantly increased total methylxanthine concentrations of tea leaves but there was no significant effect of JA treatments or the interaction of water and JA. Water availability, JA treatments or their interactive effects had no effect on the concentrations of epigallocatechin 3-gallate. In contrast, increased water availability resulted in significantly lower concentrations of epicatechin 3-gallate but the effect of JA and the interactive effects of water and JA were not significant. Lastly, higher water availability resulted in significantly higher total phenolic concentrations but there was no significant impact of JA and their interaction. These findings point to the fascinating dynamics of climate change effects on tea plants with offsetting interactions between precipitation and pest pressures within agro-ecosystems, and the need for future climate studies to examine interactive biotic and abiotic effects.
Environmental Factors Variably Impact Tea Secondary Metabolites in the Context of Climate Change: A Systematic Review
(2019-08) Ahmed, Selena; Griffin, Timothy; Kraner, Debra; Schaffner, Katherine; Sharma, Deepak; Leitch, Alicia; Orians, Colin M.; Han, Wenyan; Stepp, John R.; Robbat, Albert; Matyas, Corene; Chunlin, Long; Dayuan, Xue; Houser, Robert; Cash, Sean
Climate change is impacting food and beverage crops around the world with implications for environmental and human wellbeing. While numerous studies have examined climate change effects on crop yields, relatively few studies have examined effects on crop quality (concentrations of nutrients, minerals, and secondary metabolites). This review article employs a culturally relevant beverage crop, tea (Camelia sinensis), as a lens to examine environmental effects linked to climate change on the directionality of crop quality. Our systematic review identified eighty-six articles as relevant to the review question. Findings provide evidence that shifts in seasonality, water stress, geography, light factors, altitude, herbivory and microbes, temperature, and soil factors that are linked to climate change can result in both increases and decreases up to 50% in secondary metabolites. A gap was found regarding evidence on the direct effects of carbon dioxide on tea quality, highlighting a critical research area for future study. While this systematic review provides evidence that multiple environmental parameters are impacting tea quality, the directionality and magnitude of these impacts is not clear with contradictory evidence between studies likely due to confounding factors including variation in tea variety, cultivar, specific environmental and agricultural management conditions, and differences in research methods. The environmental factors with the most consistent evidence in this systematic review were seasonality and water stress with 14 out of 18 studies (78%) demonstrating a decrease in concentrations of phenolic compounds or their bioactivity with a seasonal shift from the spring and /or first tea harvest to other seasons and seven out of ten studies (70%) showing an increase in levels of phenolic compounds or their bioactivity with drought stress. Herbivory and soil fertility were two of the variables that showed the greatest contradictory evidence on tea quality. Both herbivory and soil fertility are variables which farmers have the greatest control over, pointing to the importance of agricultural management for climate mitigation and adaptation. The development of evidence-based management strategies and crop breeding programs for resilient cultivars are called for to mitigate climate impacts on crop quality and overall risk in agricultural and food systems.
Increased Market Integration, Value, and Ecological Knowledge of Tea Agro-forests in the Akha Highlands of Southwest China.
(2010) Ahmed, Selena; Stepp, John R.; Toleno, Robban A. J.; Peters, Charles M.
This study assesses the persistence and change of traditional land use patterns and ecological knowledge in response to expanded commercialization of tea (Camellia sinensis var. assamica (L.) Kuntze Theaceae in an indigenous Akha (Hani) community in the midlevel montane forests of southwest Yunnan, China. Surveys were conducted in 2005 and 2008, over a period corresponding to a regional tea market boom and bust cycle, to compare the valuation smallholders attribute to land use types and to determine the role that value systems play in shaping environmental behavior and knowledge. At the community level, increased market integration of tea agroforests is associated with reconfiguration of land use, intensified management, reorganization of labor structures, and generation of knowledge on tea resources. Akha have tapped into customary resources and forged new social networks with tea industry agents to take advantage of emerging market opportunities. They have resisted state reforms calling for the cultivation of high-intensity plantations and introduced cultivars. Consequently, they have benefited from price premiums through niche market networks for tea sourced from agroforests and proprietary landraces not available to other communities disempowered by market cycles. Subsistence agriculture, home gardening, and foraging persist for food security despite tea wealth. However, as traditional values are reoriented toward market-based ideologies, the community may risk a breakdown of the social institutions that support sustainability.
Pu-erh Tea Tasting in Yunnan, China: Correlation of Drinkers’ Perceptions to Phytochemistry.
(2010-10) Ahmed, Selena; Unachukwu, Uchenna J.; Stepp, John R.; Peters, Charles M.; Long, Chunlin; Kennelly, Edward J.
Aim of the study: Pu-erh (or pu’er) tea tasting is a social practice that emphasizes shared sensory experience, wellbeing, and alertness. The present study examines how variable production and preparation practices of pu-erh tea affect drinkers’ perceptions, phytochemical profiles, and anti-oxidant activity. Materials and methods: One hundred semi-structured interviews were conducted in Yunnan Province to understand the cultural and environmental context of pu-erh tea tasting. The gong fu cha dao (‘way of tea’ with ‘effort,’ ‘work,’ or ‘skill’) method of brewing tea through multiple infusions was employed to evaluate green and black pu-erh samples from smallholder agro-forests and terrace plantations. Ranking interviews, High Performance Liquid Chromatography (HPLC), and the 1-1-diphenyl-2-picrylhydrazyl (DPPH) assay were conducted to characterize color and taste profiles, Total Catechin Content (TCC), Total Methylxanthine Content (TMC), and free radical scavenging capacity (IC50). Results: Significant variation was found among pu-erh samples based on: (1) agro-ecosystem mode of production by TCC (P < 0.0001) and TMC (P < 0.0265), (2) processing method for TCC (P < 0.0001), TMC (P < 0.0027), and free radical scavenging capacity (P < 0.0001), (3) infusion sequence for TMC (P < 0.0013), (4) taste rankings for TCC (P < 0.0001), TMC (P < 0.0001), and IC50 (P < 0.0059) and, (5) color rankings for TMC (P < 0.0009) and IC50 (P < 0.0001). Samples rated as bitter and bitter-sweet contained the greatest TCC and free radical scavenging capacity. Conclusions: This research demonstrated that production environment, processing methods, and infusion sequence in preparing tea are related to the phytochemical profile, free radical scavenging activity, and flavor of tea. Findings contribute to the ethnomedical literature by supporting previous studies that have hypothesized that the taste of plants, particularly bitterness, may guide societies in the search for medicinal plants and beneficial phytochemicals.
The Role of Montane Forests for Indigenous Dongba Papermaking in the Naxi Highlands of Northwest Yunnan, China. Mountain Research and Development.
(2011-11) Yang, Lixin; Stepp, John R.; Ahmed, Selena; Pei, Shengji; Xue, Dayuan
China's rapid economic development is influencing cultural practices and natural resource management in indigenous mountain communities throughout the country. Numerous studies have documented loss and change of cultural practices and environmental degradation in indigenous communities with the expansion of roads, markets, tourism, and other infrastructure development. The present study focuses on papermaking, a socioecological practice that began in China, as a case study to examine the influence of development on cultural practices and natural resource management. The Naxi are an indigenous people who primarily inhabit the mountains of the eastern Himalaya in China's northwest Yunnan province. The Naxi people are unique in that they have the last remaining pictographic writing system in the world. The Naxi pictographic script is customarily learned and mastered by shaman priests known as Dongba (Dto'mba) who transmit their knowledge to their sons. Approximately 300,000 Naxi live in this area. The pictographic system is transmitted on paper sourced from montane forest resources, primarily Wisktroemia delavayi. This cultural tradition almost disappeared during the Cultural Revolution in China during the 1960s and 1970s but has recently seen a revival. Research involved both ethnographic interviews and ecological sampling. Semistructured interviews were conducted with 100 informants between 2002–2011 to understand the management and use of W. delavayi for Dongba papermaking and the impact of market integration on papermaking. Sample plots were surveyed for floristic composition and structure in the 3 vegetation types where W. delavayi grows. Density, height, diameter, and number of branches of W. delavayiplants were recorded within each plot. Ecological importance values were calculated based on relative density, relative dominance, and relative frequency to determine the habitat where W. delavayidemonstrates the greatest growth. Additional plots were surveyed to understand the regeneration of W. delavayi after the local harvest cycle.
Striking changes in tea metabolites due to elevational effects
(2018-10) Kfoury, Nicole; Morimoto, Joshua; Kern, Amanda; Scott, Eric R.; Orians, Colin M.; Ahmed, Selena; Griffin, Timothy S.; Cash, Sean B.; Stepp, John R.; Xue, Dayuan; Long, Chunlin; Robbat, Albert Jr.
Climate effects on crop quality at the molecular level are not well-understood. Gas and liquid chromatography–mass spectrometry were used to measure changes of hundreds of compounds in tea at different elevations in Yunnan Province, China. Some increased in concentration while others decreased by 100’s of percent. Orthogonal projection to latent structures-discriminant analysis revealed compounds exhibiting analgesic, antianxiety, antibacterial, anticancer, antidepressant, antifungal, anti-inflammatory, antioxidant, anti-stress, and cardioprotective properties statistically (p = 0.003) differentiated high from low elevation tea. Also, sweet, floral, honey-like notes were higher in concentration in the former while the latter displayed grassy, hay-like aroma. In addition, multivariate analysis of variance showed low elevation tea had statistically (p = 0.0062) higher concentrations of caffeine, epicatechin gallate, gallocatechin, and catechin; all bitter compounds. Although volatiles represent a small fraction of the total mass, this is the first comprehensive report illustrating how normal variations in temperature, 5 °C, due to elevational effects impact tea quality.