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The carbon balance of forests is controlled by many component processes of carbon acquisition and carbon loss and depends on the age of vegetation, soils, species composition, and the local climate. Thus, examining the carbon balance of different forests around the world is necessary to understand the global carbon balance. Nevertheless, the available information on the carbon balance of Larix principis-rupprechtii forests in the Qinling Mountains remains considerably limited. We provide the first set of results (2010-2013) from a long-term project measuring forest-atmosphere exchanges of CO2 at the Qinling National Forest Ecosystem Research Station (QNFERS), and compare the net ecosystem exchange (NEE) based on biometric measurements with those observed via the eddy covariance method. We also compare the total ecosystem respiration via scaled-up chamber and eddy covariance measurements. The net primary productivity (NPP) was 817.16 ± 81.48 g.C.m-2.y-1, of which DBliving and Dtotal accounted for 77.7%, and 22.3%, respectively. Total ecosystem respiration was 814.47 ± 64.22 g.C.m-2.y-1, and cumulative annual soil respiration, coarse woody debris respiration, stem respiration, and leaf respiration were 715.47 ± 28.48, 15.41 ± 1.72, 35.28 ± 4.78, and 48.31 ± 5.24 g.C.m-2.y-1, respectively, accounting for 87.85%, 1.89%, 4.33%, and 5.93% of the total ecosystem respiration. A comparison between ecosystem respiration from chamber measurements and that from eddy covariance measurements showed a strong linear correlation between the two methods (R2 = 0.93). The NEE of CO2 between forests and the atmosphere measured by eddy covariance was -288.33 ± 25.26 g.C.m-2.y-1, which revealed a carbon sink in the L. principis-rupprechtii forest. This number was 14% higher than the result from the biometric measurements (-336.71 ± 25.15 g.C.m-2.y-1). The study findings provided a cross-validation of the CO2 exchange measured via biometric and eddy covariance, which are beneficial for obtaining the true ecosystem fluxes, and more accurately evaluating carbon budgets. [ABSTRACT FROM AUTHOR]

The Loess Plateau in China constitutes an area short of soil nitrogen and organic carbon due to local land degradation induced by various factors (i.e. long term changes of land use, climate conditions, and soil properties). The present study aimed to examine the effects of species and land management by afforestation on tree N acquisition capacity and soil N and C availability in degraded soils of the Loess Plateau area. We quantified root N uptake of inorganic and organic N sources as well as soil N and C availability, both at the tree species (i.e. Robinia pseudoacacia L., Juglans regia L. and Pinus tabulaeformis Carr.) and the land management (i.e. arable vs. monoculture vs. mixed afforested stands) levels. Our results indicated that afforestation improved soil N and organic C availabilities compared to abandoned arable land ( p < 0.05). In particular, the presence of N 2 -fixing R. pseudoacacia enhanced root N concentrations (ca. 3.0 times) and soil NO 3 - (ca. 5.4 times), soil total N (ca. 1.9 times) and organic C (ca. 3.4 times) availabilities, but decreased soil NH 4 + (ca. −33%), microbial biomass carbon (ca. −74%) and nitrogen (ca. −54%) in the mixed stand compared to J. regia monoculture. Under the experimental conditions applied, the afforested trees preferred organic over inorganic N compounds as well as NO 3 − over NH 4 + ; J. regia in monoculture had a highest root amino acids N uptake capacities (i.e. 76.6 ± 7.7 nmol N (g fw) − 1 h −1 for glutamine, 90.3 ± 8.9 nmol N (g fw) − 1 h −1 for arginine) compared to other tree species whereas such high uptake capacities were largely repressed in the mixed stand with R. pseudoacacia . Thus, in the Loess Plateau area, the inter-planting system of J. regia with N 2 -fixing R. pseudoacacia could improve the total soil N and organic C pools as well as plant N cycling compared to traditional arable land use and J. regia monoculture system. This study shows that inter-planting R. pseudoacacia with economic fruit trees can be considered a successful strategy for soil regeneration by afforestation in future land management projects. [ABSTRACT FROM AUTHOR]

Nowadays, agro-forestry farming is a major issue in Vietnamat midland and mountainous region as it has to satisfy the demand of forest production and ecosystem protection. Compared to some other types of forest, agro-forest has demonstrated outstanding strength as it provides landowners with early and fast income generation. Therefore, developing agro-forest becomes a trend when the research on land use gets much attention. However, environmental efficiency of agro-forest is quite varied and closely reliable on the structure of the forest system. Taking into consideration of both environmental condition and the efficiency at the same time is significant not only in evaluating the current situation of the forest but also in improving its structure, thereby reaching environmental goals. Nevertheless, there is a shortage of research on above problem in Hoa Binh hydropower reservoir environment. Due to this restriction many agroforests were in failure to enhance their economic and protective functions and the forest also showed low stability. In order to have a part in solving the aforesaid inadequacies, this paper has been conducted. The environmental protection and soil conservation of vegetation have high requirements in hydropower station reservoir area. Finding a kind of land use pattern that can meet the interests of all parties is particularly important in the context that moving local residents out of the reservoir area is impossible. In the present study, the four main agro-forestry system patterns (Acacia mangium - Zea mays; Acacia mangium - Manihot esculenta crantz; Eucalyptus camandulensis - Oryza sativa; Acacia mangium - Manihot esculenta crantz - Zea mays) were employed as the research subjects in two different areas (Thung Nai Commune, Cao Phong District and Vay Nua Commune, Da Bac District) of Hoa Binh hydropower station reservoir area in Vietnam. Multiple structural indicators such as plant species composition, morphemic structures, density and canopy of the plantation used, coverage of shrub layers as well as environmental indicators such as fertility retention, water use efficiency and soil conservation through prohibition of erosion were used to evaluate the four proposed agroforestry patterns employed in the study and to find out the most appropriate one. The results showed that among the four patterns, Acacia mangium - Manihot esculenta crantz - Zea mays pattern had the highest comprehensive environment benefit and soil conservation benefit; on the contrary, Eucalyptus camandulensis - Oraza sativa pattern scored lowest. So, the former planting area should be encouraged to increase, and the latter planting area should be reduced in the future practice. On the basis of Acacia mangium - Manihot esculenta crantz - Zea mays pattern, we put forward the Acacia mangium - Manihot esculenta crantz - Zea mays - Cinnamomum cassia pattern that has higher expectations of comprehensive environmental benefits. It's proposed as a better choice for the application of agroforestry system in Hoa Binh hydropower station reservoir area. And this research also provides a reference for the areas with similar climatic and environmental conditions with Hoa Binh hydropower station reservoir area. [ABSTRACT FROM AUTHOR]

Since 2005, an unresolved debate has questioned whether R-shaped vulnerability curves ( VCs) might be an artefact of the centrifuge method of measuring VCs. VCs with R-shape show loss of stem conductivity from approximately zero tension, and if true, this suggests that some plants either refill embolized vessels every night or function well with a high percentage of vessels permanently embolized. The R-shaped curves occur more in species with vessels greater than half the length of the segments spun in a centrifuge. Many have hypothesized that the embolism is seeded by agents (bubbles or particles) entering the stem end and travelling towards the axis of rotation in long vessels, causing premature cavitation. VCs were measured on R obinia pseudoacacia L. by three different techniques to yield three different VCs; R-shaped: Cavitron P50 = 0.30 MPa and S-shaped: air injection P50 = 1.48 MPa and bench top dehydration P50 = 3.57 MPa. Stem conductivity measured in the Cavitron was unstable and is a function of vessel length when measured repeatedly with constant tension, and this observation is discussed in terms of stability of air bubbles drawn into cut-open vessels during repeated Cavitron measurement of conductivity; hence, R-shaped curves measured in a Cavitron are probably invalid. [ABSTRACT FROM AUTHOR]

Vulnerability curves ( VCs) generally can be fitted to the Weibull equation; however, a growing number of VCs appear to be recalcitrant, that is, deviate from a Weibull but seem to fit dual Weibull curves. We hypothesize that dual Weibull curves in Hippophae rhamnoides L. are due to different vessel diameter classes, inter-vessel hydraulic connections or vessels versus fibre tracheids. We used dye staining techniques, hydraulic measurements and quantitative anatomy measurements to test these hypotheses. The fibres contribute 1.3% of the total stem conductivity, which eliminates the hypothesis that fibre tracheids account for the second Weibull curve. Nevertheless, the staining pattern of vessels and fibre tracheids suggested that fibres might function as a hydraulic bridge between adjacent vessels. We also argue that fibre bridges are safer than vessel-to-vessel pits and put forward the concept as a new paradigm. Hence, we tentatively propose that the first Weibull curve may be accounted by vessels connected to each other directly by pit fields, while the second Weibull curve is associated with vessels that are connected almost exclusively by fibre bridges. Further research is needed to test the concept of fibre bridge safety in species that have recalcitrant or normal Weibull curves. [ABSTRACT FROM AUTHOR]

• Stakeholders and park visitors' perception of lawns in a typical Chinese megacity are studied. • The aesthetic and ecological values of lawns are mostly appreciated. • Messy meadows are least preferred, while neat lawns are most preferred by park visitors. • Chinese lawns are limited for public access due to a large number of visitors and associated damage. • Challenges and opportunities of using sustainable lawn alternatives in Chinese cities are analysed. The lawn is one of the most visible elements of urban green spaces. China, as one of the latest adopters of lawns, has seen a dramatic increase in yearly planted lawn area. However, there is an urgent need for sustainable lawn alternatives in China due to potential threats to the urban environment from intensive maintenance and cultural inadequacy of lawns. This study aims to explore how stakeholders and park visitors relate to lawns and how this affects their decisions in designing, managing and interacting with lawns and lawn alternatives in China by using Xi'an as a case study city. The study uses face-to-face interviews with stakeholders and questionnaires with park visitors as well as observational studies of people's activity on park lawns. Results show that park lawns in Xi'an are subject to high maintenance compared with some European cities and people have limited access to them. Lawn activities differ from western countries due to cultural reasons. The lawn is valued for its ecological and aesthetical values but least appreciated as important places for outdoor activities. Recognition of various functions of lawns, western influences and unavailability of sustainable alternatives are reasons of increasing use of conventional lawns. Physical factors, cultural preferences, limited maintenance budget, local policies, biodiversity-oriented attitudes and unsuitability of current lawn alternatives are factors favouring the search of sustainable lawn alternatives. Park visitors like lawns because of their neatness and green colour, meanwhile they appreciate groundcovers with bright colourful flowers. The establishment of biodiverse lawn alternatives is not welcomed in urban areas but can be accepted in districts with ecological visions, wetland parks and suburban areas. Our findings might lessen the knowledge gaps among decision makers, park visitors and researchers regarding lawns. This study contributes to the knowledge of policy making and planning of sustainable green spaces from region, city to park levels. [ABSTRACT FROM AUTHOR]

Strigolactones (SLs) have recently been shown to play roles in modulating plant architecture and improving plant tolerance to multiple stresses, but the underlying mechanisms for SLs regulating leaf elongation and the influence by air temperature are still unknown. This study aimed to investigate the effects of SLs on leaf elongation in tall fescue (Festuca arundinacea, cv. 'Kentucky-31') under different temperature regimes, and to determine the interactions of SLs and auxin in the regulation of leaf growth. Tall fescue plants were treated with GR24 (synthetic analog of SLs), naphthaleneacetic acid (NAA, synthetic analog), or N-1-naphthylphthalamic acid (NPA, auxin transport inhibitor) (individually and combined) under normal temperature (22/18 °C) and high-temperature conditions (35/30 °C) in controlled-environment growth chambers. Exogenous application of GR24 stimulated leaf elongation and mitigated the heat inhibition of leaf growth in tall fescue. GR24-induced leaf elongation was associated with an increase in cell numbers, upregulated expression of cell-cycle-related genes, and downregulated expression of auxin transport-related genes in elongating leaves. The results suggest that SLs enhance leaf elongation by stimulating cell division and interference with auxin transport in tall fescue. [ABSTRACT FROM AUTHOR]

Aims: Although the variation in absorptive root traits at the species level and driving factors has received a lot of attention, it is still unknown how community-level root traits vary along the environmental gradients. Methods: In this study, absorptive fine roots of 69 woody plants from four forest vegetation on the northern slope of Taibai Mountain were collected, and four root traits (including morphological and chemical traits) were measured. Results: At the species level, absorptive root traits, except root nitrogen concentration (RNC), did not change along altitudinal gradients. A large proportion of variation in root diameter (RD), specific root length (SRL) and root tissue density (RTD) was attributed to phylogenetic taxonomy (clade, 39.47-60.72%). Differently, community-level absorptive roots at birch forest exhibited thinner RDc and lesser RNCc but longer SRLc and greater RTDc than other altitudes, which were mainly influenced by the climatic (aridity index) and soil factors (soil available P and nitrate concentration). Moreover, unlike root economic space, community-level root traits were divided into the morphological (including RDc, SRLc and RTDc) and chemical (including RNCc) dimensions. Conclusions: Our results indicate that the response of community-level root traits to climatic and soil factors is more significant compared to species-level root traits. Future studies should incorporate community-level root traits into global vegetation distribution models. [ABSTRACT FROM AUTHOR]

To lessen the negative environmental impact of chemical fertilizers, replacing chemical fertilizers with more organic fertilizers for famers is a good choice. However, most of the farmers would like to use chemical fertilizers instead of organic fertilizers in developing countries, mainly because they fear that they may lose income if they use organic fertilizers instead of chemical fertilizers. From this point, policy makers need to find strategies to incentivize farmers to use organic fertilizers instead of chemical fertilizers. Therefore, a randomly selected household survey on the use of chemical and organic fertilizers by apple growers in China was conducted from July 2016 to October 2016. Its aim is to find out what could promote farmers to replace chemical fertilizers with organic fertilizers partially or completely. We have analyzed farmers' choices involving prospect utility, risk, and environment based on Kahneman's prospect theory and Lewin's field theory. Twelve psychological and socio-economic variables were included in a tobit regression model to explain farmers' choice between organic fertilizers and chemical fertilizers. We find that membership in agriculture cooperatives, subsidies on organic fertilizers, and farm size play positive roles in influencing farmers' choice of organic fertilizers instead of chemical fertilizers. The results will be helpful to update extension policy of organic fertilizers. [ABSTRACT FROM AUTHOR]

Purpose: We sought to identify the effects of elevationally (1560−2160 m) driven climate (mean annual air temperatures of + 4.0 to + 10 oC and mean annual precipitation of 900–1200 mm), forest type and soil property variations on soil greenhouse gas (GHG) fluxes in the Qinling Mountains, China. Methods: Soil GHGs were monitored at five temperate forest sites using static chambers for two full years. The related edaphoclimatic parameters were also monitored. Results: The cumulative soil CO2 and N2O emissions and the CH4 uptake from the five sites ranged between 3.82 to 7.48 t CO2-C ha−1 yr−1, 1.19 to 2.25 kg N2O-N ha−1 yr−1, and 0.89 to 5.67 kg CH4-C ha−1 year−1, respectively. Average soil CO2 emissions decreased with increasing site elevation, whereas CH4 and N2O fluxes showed no clear relationship with site elevation. All sites were net CH4 sinks. Occasionally, soils switched to net sources of CH4 during summer or autumn rainfall events at all sites. All sites were net N2O sources although short periods of soil N2O uptake were observed during freeze–thaw cycles and during summer rainfall. The source strength of N2O and CH4 differed during summer and winter and snowfall which had direct effects on soil water content. Conclusions: Site elevation could be used as a predictive variable for constructing regional soil CO2 emissions budgets, whereas soil CH4 and N2O fluxes are driven by a more complex interplay of climatic and soil biochemical variables, which are more difficult to integrate on a regional scale. [ABSTRACT FROM AUTHOR]

Low temperature is an adverse environmental factor posing damage to tomato plants and causing huge loss of yields. Thus, seeking an effective way of ameliorating cold damage is important for sustainable tomato production. Melatonin is a crucial molecule involved in plant abiotic stress responses. In this study, we investigated the role of exogenous melatonin in amelioration of cold damage in tomato plants. Lower malondialdehyde (MDA) content and electrolyte leakage, greater activities of antioxidant enzymes, and higher levels of non-enzymatic antioxidants were observed in melatonin-pretreated plants than in non-melatonin-pretreated plants under cold stress. Gene expression analyses showed that exogenous melatonin substantially promoted expression of cold-responsive genes, including SlICE , SlCBF and SlP5CS , under cold condition. Notably, SlSBP , a gene encoding a Calvin cycle enzyme sedoheptulose-1,7-bisphosphatase (SBPase), was considerably induced in melatonin-treated plants under cold stress, consistent with the observed increase in photosynthetic carbon assimilation. Analyses of metabolites revealed that levels of polyamines, sucrose, and proline were significantly enhanced following cold treatment in melatonin-pretreated plants. Collectively, our data provide evidence for the ameliorative effects of melatonin on cold-induced damage to tomato plants. Our work also provides a case study that exogenous application of melatonin may be potentially employed as a strategy to improve cold tolerance in tomato production. [ABSTRACT FROM AUTHOR]

Sedoheptulose-1,7-bisphosphatase (SBPase) is a critical enzyme involved in photosynthetic carbon fixation in the Calvin cycle. Here, we report the effects of SBPase overexpression on the tolerance to chilling-induced oxidative stress in transgenic tomato ( Solanum lycopersicum ) plants. In transgenic plants overexpressing SBPase, CO 2 fixation and carbohydrate accumulation were increased in comparison with equivalent wild-type plants. SBPase was found to be susceptible to oxidative stress and the activity was substantially inhibited by reactive oxygen species both in vivo and in vitro . In response to chilling stress, production of H 2 O 2 was increased in parallel with the reduction in SBPase activity in tomato plants, however, transgenic plants maintained significantly higher SBPase activity than wild-type plants did. Under chilling stress, compared with wild-type plants, transgenic plants were found to have increased CO 2 fixation and reduced electrolyte leakage. The overall tolerance could be ascribed to the enhancement of photosynthetic carbon fixation, the reductions in the level of H 2 O 2 and the increased accumulation of carbohydrate in transgenic plants. Collectively, our data suggest that high level of SBPase activity gives an advantage to photosynthetic carbon fixation and tolerance to chilling-induced oxidative stress in tomato plants. This work presents a case study that an individual enzyme in the Calvin cycle may be a useful target for genetically engineering stress tolerance in horticultural crops. [ABSTRACT FROM AUTHOR]