Enclosure Measurements Research Articles

Effects of enclosure measures on soil water infiltration and evaporation in arid and semi-arid grassland in northern China

Effects of enclosure measures on soil water infiltration and evaporation in arid and semi-arid grassland in northern China

Effects of Enclosure Succession on the Morphological Characteristics and Nutrient Content of a Bamboo Whip System in a Moso Bamboo (Phyllostachys edulis) Forest on Wuyi Mountain, China

To investigate the morphological characteristics and nutrient content of bamboo whip systems in the Wuyi Mountain Moso bamboo (Phyllostachys edulis) forest in response to enclosure succession. The mixed Moso bamboo forests in the Wuyi Mountain Nature Reserve with 0, 4, 6, 11, 16, and 41 enclosure years were taken as the object of investigation. All the bamboo whips in the 2 m × 2 m sample plots were excavated layer-by-layer according to the soil layers of 0–20 cm, 20–40 cm, and 40–60 cm, and a total of 54 plots were dug. The morphological characteristics and nutrient contents of the Moso bamboo whips in the different soil layers were analyzed and evaluated. Enclosure management measures can not only effectively improve vegetation coverage, biodiversity, and biomass, but also improve soil moisture and nutrient status, indirectly affecting the vegetation, which is of great significance for preventing soil erosion. The results showed that the whip number, whip diameter, flagella number, whip length, and whip weight in the 0–20 cm soil layer were significantly increased by 169.2%, 11.0%, 197.5%, 113.7%, and 109.0% (p < 0.05), respectively, compared with CK after 41 years of enclosure. The average internode length was significantly decreased by 27.9% (p < 0.05) compared to CK after 41 years of enclosure. In the 20–40 cm soil layer, the whip diameter increased by 9.7% after 41 years of enclosure compared with CK, but the whip number, flagella number, whip length, and whip weight were significantly reduced after 16 and 41 years of enclosure compared to CK (p < 0.05). In the 40–60 cm soil layer, the whip number, number of flagella, and whip length increased significantly after 6 and 11 years of enclosure compared with CK (p < 0.05). In the 0–20 cm soil layer, the contents of total nitrogen, total phosphorus, and total potassium in CK were higher than those in other enclosure years, and the soluble sugar content in CK was significantly higher than that in the enclosures of 4, 6, 11, and 41 years by 39.8%, 37.9%, 34.4%, and 34.0% (p < 0.05). The organic carbon content was significantly increased by 14.8%, 12.7%, 7.2%, and 7.1% (p < 0.05) after 4, 6, 11, and 41 years of enclosure compared with CK, respectively. The starch content was significantly increased by 34.1%, 23.0%, and 62.7% (p < 0.05) after 6, 16, and 41 years of enclosure compared with CK, respectively. In the 20–40 cm and 40–60 cm soil layers, the total nitrogen content and soluble sugar content in CK were significantly lower than that in the enclosures of 4 years (p < 0.05), the total phosphorus and total potassium content in CK were significantly higher than that in the enclosures of 41 years (p < 0.05), and the organic carbon content and starch content in CK were significantly higher than that in the enclosures of 6 years (p < 0.05). In summary, enclosure measures were implemented for Moso bamboo forests in the Wuyi Mountain Nature Reserve, which promote the growth of Moso bamboo whips and optimize the structure of bamboo whips.

Vegetation Characteristics of the Main Grassland Types in China Respond Differently to the Duration of Enclosure: A Meta-Analysis

Enclosure is one of the useful measures to protect and restore degraded grasslands, and it is widely used around the world. The vegetation characteristics of grasslands directly reflect the recovery status of degraded grasslands; however, conflicting results of plant traits were continually achieved in the numerous on-site studies of enclosure in the last two decades. It is necessary to conduct a systematic assessment to find a general conclusion for the effects of enclosure on different grasslands. Studies on the enclosure grasslands in China were taken as the objects to refine the relationships between grassland vegetation characteristics and enclosure measures using meta-analysis. Enclosure had positive effects on the restoration of vegetation coverage, aboveground and belowground biomass, and diversity of degraded grasslands. Different vegetation characteristics and grassland types showed different responses to enclosure duration. The vegetation productivity reached a maximum in the 11–15 years of enclosure for alpine grasslands and typical steppe grasslands, 6–10 years for desert grasslands, and more than 15 years of enclosure for meadow grasslands. Plant species diversity reached the peak values when alpine grasslands and typical steppe grasslands were enclosed approximately 10 years, desert grasslands approximately 11–15 years, and meadow grasslands approximately 5 years. These results indicated that the management strategies of enclosed grasslands should be adjusted reasonably according to the types and the management objectives of grasslands in order to maintain or even improve the condition and services of grassland ecosystems.

Evaluation of isoprene light response curves for bryophyte-dominated ecosystems and implications for atmospheric composition

Isoprene is emitted from numerous plant species in response to light and temperature and parameterisations of these relationships, based on observations from a few vascular plant species, have been shown to be broadly applicable to many different vegetation types. Here, we investigate their performance when applied to an ecosystem dominated by bryophytes. Over a six-week period, emissions of isoprene were measured above a Scottish peat bog. The light response derived on the basis of both canopy-scale flux and whole-plant enclosure measurements, deviated from the classical response, showing no sign of saturation within the observed range. We attribute this response to the canopy architecture of moss hummocks, which may attenuate light differently compared to a grass canopy. Both existing big-leaf and canopy-level emission algorithms, developed for vascular plants but commonly used for moorland vegetation, failed to replicate the observed fluxes, overestimating at low light intensities (<1000 μmol m−2 s−1 photosynthetically active radiation) and underestimating during daytime clear sky conditions. The light response was optimised for bryophyte-dominated ecosystems using measured fluxes and incorporated into the EMEP4UK chemical transport model and applied exclusively to moorland. The revised parameterisation resulted in a small reduction in the average annual isoprene emissions in the northern latitudes (5%), but peak isoprene emissions and concentrations increased by up to a factor of two. Yet, no significant change in average or maximum surface ozone concentrations was observed, reflecting that the northern latitudes are in a chemical regime that is strongly NOx limited, in part due to the spatial segregation with the urban sources of NO x . We conclude that, the anticipated increase in isoprene emissions from the northern latitudes in response to climate change is unlikely to contribute towards ozone-related air quality issues, as long as NO x pollution does not increase. However, the non-saturating light response may be equally applicable to non-vascular plants elsewhere, including in the tropics.

Rapid Sampling Protocol of Isoprene Emission Rate of Palm (Arecaceae) Species Using Excised Leaves

The high isoprene emission capacity of palm species can decrease regional air quality and enhance the greenhouse effect when land is converted to palm plantations. Propagation of low-emitting individuals can be a strategy for reducing isoprene emission from palms. However, the identification of low-emitting individuals requires large-scale sampling. Thus, we aimed to develop a rapid method in which the isoprene emission rate of leaf segments is observed. We examined the temperature response and effect of incubation length on the isoprene emission rate of palm leaf and found that leaf temperatures at 25 to 30 °C and an incubation length of 40 min are suitable parameters. To further examine the validity of the method, we applied both the enclosure method and this method to the same sections of leaves. High coefficient of determinations (0.993 and 0.982) between the results of the two methods were detected regardless of seasonal temperature. This result proves that the method is capable of measuring the isoprene emission rate under any growth conditions if the incubation temperature is controlled. By using a water bath tank and a tested light source, we can simply implement a unified environmental control of multiple samples at once, which achieves a higher time efficiency than conventional enclosure measurements.

Response of soil aggregate stability and erodibility to different treatments on typical steppe in the Loess Plateau, China

Vegetation restoration is an effective means to increase the stability of aggregates and the ability of soil to resist erosion. At present, there are few studies on soil aggregate stability in contour trench and fish‐scale pit grasslands (FPGs). Therefore, to determine the effects of different treatments on the stability of aggregates in the Loess Plateau, grazing grassland (GG), fencing grassland (FG), contour trench grassland (CG), and FPG were selected to compare distributions of soil aggregates, the soil aggregate stability, and soil erodibility K value. The results showed that &lt;0.25‐mm and &gt;5‐mm aggregates were the main components. The mass percentage of 5–0.25‐mm aggregates in FG was significantly higher than that in GG, CG, or FPG. The proportion of large water‐stable aggregates, mean weight diameter, and geometric mean diameter values were significantly higher in GG than in FG, CG, or FPG for topsoil, while FG had the highest WR0.25 (70.21%) for subsoil. The opposite trends were found for fractal dimension and percentage of aggregate destruction values. The K values for CG and FPG were found to be significantly higher than those for GG and FG. A correlation analysis indicated that soil organic carbon can promote the stability of soil aggregates. A negative correlation was found between the comprehensive score and K values. In summary, FG had positive effects on soil aggregate stability and erodibility. This finding can guide the local government to adopt enclosure measures when implementing ecological restoration of degraded grasslands.

A Paradigm Shift in Critical Care Infrastructure in Complex Settings: Evaluating an Ultraportable Operating Room to Improve Field Surgical Safety.

Scarcity of operating rooms and personal protective equipment in far-forward field settings make surgical infections a potential concern for combat mortality and morbidity. Surgical and transport personnel also face infectious risks from bodily fluid exposures. Our study aimed to describe the serial, proof-of-concept testing of the SurgiBox technology: an inflatable sterile environment that addresses the aforementioned problems, fits on gurneys and backpacks, and drapes over incisions. The SurgiBox environmental control unit and inflatable enclosure were optimized over five generations based on iterative feedback from stakeholders experienced in surgery in austere settings. The airflow system was developed by analytic modeling, verified through in silico modeling in SOLIDWORKS, and confirmed with prototype smoke-trail checking. Particulate counts evaluated the enclosure's ability to control and mitigate users' exposures to potentially infectious contaminants from the surgical field in various settings. SurgiBox enclosures were setup over a mannequin's torso, in a configuration and position for either thoracic or abdominal surgery. A particle counter was serially positioned in sternotomy and laparotomy positions, as well as bilateral flank positions. This setup was repeated with open ports exposing the enclosure to the external environment. To simulate stress scenarios, sampling was repeated with enclosure measurements during an increase in external particulate concentration. The airflow technology effectively kept contaminants away from the incision and maintained a pressure differential to reduce particle entry. Benchtop testing demonstrated that even when ports were opened or the external environment had high contaminant burden, the enclosed surgical field consistently registered 0 particle count in all positions. Time from kit opening to incision averaged 54.5 seconds, with the rate-limiting step being connecting the environmental control unit to the enclosure. The portable kit weighted 5.9 lbs. Analytic, in silico, and mechanical airflow modeling and benchtop testing have helped to quantify the SurgiBox system's reliability in creating and maintaining an operating room-quality surgical field within the enclosure as well as protecting the surgical team outside the enclosure. More recent and ongoing work has focused on specifying optimal use settings in the casualty chain of care, expanding support for circumferential procedures, automating airflow control, and accelerating system setup. SurgiBox's ultimate goal is to take timely, safe surgery to patients in even the most austere of settings.

The importance of accounting for enhanced emissions of monoterpenes from new Scots pine foliage in models - A Finnish case study

Models to predict the emissions of biogenic volatile organic compounds (BVOCs) from terrestrial vegetation largely use standardised emission potentials derived from shoot enclosure measurements of mature foliage. In these models, the potential of new foliage to emit BVOCs is assumed to be similar, or up to twice as high, as that of mature foliage, and thus new conifers foliage is predicted to have a negligible to minor contribution to canopy BVOC emissions during spring time due to the small foliage mass of emerging and growing needles. Extensive observations have, however, recently demonstrated that the potential of new Scots pine needles to emit several different BVOCs can be up to about 500 times higher than that of the corresponding mature foliage. Thus, we build on these discoveries and investigate the potential impact of considering these enhanced emissions from new Scots pine foliage on estimates of monoterpene emissions and new atmospheric aerosol particle formation and their subsequent growth. We show that the importance of taking the enhanced monoterpene emission potential of new Scots pine foliage into account decreases as a function of season, tree age and latitude, and that new foliage could be responsible for the majority of the whole tree's foliage emissions of monoterpenes during spring time, independently of tree age and location. Our results suggest that annual monoterpene emission estimates from Finland would increase with up to ~25% if the enhanced emissions from new Scots pine foliage were also considered, with the majority being emitted during spring time where also new particle formation has been observed to occur most frequently. We estimate that our findings can lead to increases in predictions of the formation rates of 2 nm particles during spring time by ~75–280% in northern Finland and by ~130–870% in southern Finland. Likewise, simulated growth rates of 2–3 nm particles would increase by ~65–180% in northern Finland and by ~110–520% in southern Finland if the enhanced emissions of monoterpenes from new Scots pine foliage were explicitly considered. Since only one measurement study (Aalto et al., 2014), on which our work builds, has so far found highly pronounced emissions of monoterpenes from new Scots pine foliage compared to those of mature, we conclude that more spring time measurements of new conifers foliage are required for improving emission algorithms in biogenic emission models. • In models, emission potentials of new and mature foliage are assumed to be similar. • VOCs emissions from new vs mature pine foliage can differ by 2–3 orders of magnitude. • Accounting for new foliage emissions significantly impacts annual emission estimates. • Enhanced springtime emissions can lead to enhanced aerosol formation and growth.

Modeling and prediction accuracy of ammonia gas emissions from feedlot cattle

ABSTRACT Objective The objective was to develop an equation to indirectly predict the effect of feeding ExperiorTM (lubabegron; Elanco Animal Health, Greenfield, IN) on ammonia gas emissions (AGE) from cattle in subsequent feedlot studies. Materials and Methods Our approach was to develop a prediction equation [the Elanco Ammonia Gas Emission Prediction Model (EPM)] using data from a 91-d clinical efficacy study in which lubabegron was fed to cattle housed in a cattle pen enclosure system and compare the precision and accuracy of the EPM with the precision and accuracy of a published equation that was developed to predict AGE from open-air feedlots. Results and Discussion The evaluation of the published equation used to predict daily AGE (g/animal) resulted in poor precision (R2 = 0.329) but reasonable accuracy (prediction bias = +14.8%). The developed EPM equation explained 98.7% of the variation in observed log10 of cumulative AGE in the clinical efficacy study. Implications and Applications The EPM explained 58.9 to 84.9% of the variation in cumulative AGE in 2 evaluation data sets, with a prediction bias of +0.13 to +18.6%. These data suggest that the EPM derived from the development data set using the cattle pen enclosure measurement system showed great promise to accurately and precisely predict cumulative AGE in future feedlot studies.

Evaluation of semi-static enclosure technique for rapid surveys of biogenic volatile organic compounds (BVOCs) emission measurements

Biogenic volatile organic compounds (BVOCs) are important drivers of atmospheric chemical composition and accurate model simulations require characterization of the emissions associated with specific vegetation types which is typically determined using enclosure measurements. Static enclosure techniques were used for past BVOC emission measurement studies, especially in the 1960s–1980s, but are no longer widely used because of concerns that the resulting emission rates are not representative. The main advantages of the static approach are the capability for rapid measurements and a lower detection limit that enables the use of less sensitive analytical techniques. We evaluate a version of the static approach which we call the semi-static approach. In order to evaluate the performance of the semi-static approach for BVOCs emission measurements, multiple replicate measurements for different plants were conducted in a laboratory growth chamber using both semi-static and dynamic enclosure techniques. Variability of replicate measurements was calculated and the results from the two techniques were compared. The semi-static technique provided consistent measurements for isoprene but not for α-pinene, β-pinene and other compounds that are stored in leaves. The measured isoprene emission factors were much higher than dynamic measurements. There were a large number of compounds to be detected by dynamic technique that could not be detected by the semi-static technique. But the semi-static technique could still provide qualitative information on categorization of non, low and high emitters for some compounds.

Leaf enclosure measurements for determining volatile organic compound emission capacity from Cannabis spp.

Leaf enclosure measurements for determining volatile organic compound emission capacity from Cannabis spp.

Leaf enclosure measurements for determining volatile organic compound emission capacity from Cannabis spp.

The legal commercialization of Cannabis for recreational and medical use in certain US states has effectively created a new and nearly unregulated cultivation industry. Within the city limits of Denver, Colorado, there are now more than 600 registered Cannabis spp. cultivation facilities (CCFs) for recreational and medical uses, each containing thousands of plants. Ambient measurements collected inside growing operations pre-legalization have found concentrations as high as 50–100 ppbv of terpenes; a group of highly reactive biogenic volatile organic compounds (BVOCs) and known precursors for the formation of ozone and particulate matter (PM). Due to its illicit nature there has been insufficient experimental data produced to determine Cannabis spp. emission rates. This study used, for the first time, an enclosure chamber and live Cannabis spp. plants during a 90-day growing period consisting of four different strains of Cannabis spp.: Critical Mass, Lemon Wheel, Elephant Purple, and Rockstar Kush. These measurements enabled characterization of terpenes and estimates of emission capacity (EC, μgC g−1 hr−1) at standard conditions. During peak growth, the percentages of individual BVOC emissions were dominated by β-myrcene (18–60%), eucalyptol (17–38%), and d-limonene (3–10%) for all strains. Our results showed large variability in the rate and composition of terpene emissions across different strains. For the Critical Mass and Lemon Wheel, the dominant terpenoid was eucalyptol (32% and 38%), and it was β-myrcene (60% and 45%) for the Elephant Purple and Rockstar Kush. Critical Mass produced the highest terpene emission capacity (8.7 μgC g−1 hr−1) and Rockstar Kush the lowest (4.9 μgC g−1 hr−1). With 600 CCFs in Denver, and assuming 10,000 plants per CCF, an emission capacity of 8.7 μgC g−1 hr−1 would more than double the existing rate of BVOC emissions to 520 metric ton year−1. Using Maximum Incremental Reactivity (MIR) values the total ozone formation potential from all these emitted species could produce 2100 metric tons year−1 of ozone, and based on published secondary organic aerosols yields 131 metric tons year−1 of PM. It is likely that the ECs calculated here are lower than those achieved in CCFs where growing conditions are optimized for rapid growth and higher biomass yields. Further studies including a greater number of the 620 available Cannabis spp. strains and a wider range of treatments are needed to generate a representative dataset. Such a dataset could then better enable assessments of the potential impacts of this new industry on indoor and regional air quality.

材料屏蔽效能测试方法比较研究

屏蔽效能是对屏蔽体隔离或限制电磁波的能力的度量，是反映屏蔽材料最主要的指标，因此，屏蔽效能测试技术的规范性、适用性至关重要。目前屏蔽效能测试标准已有十几种，包括国标、国军标、行标等，虽然每种方法都能获得实验数据，但不同测试条件下的实验数据差异性很大，影响到屏蔽材料的应用。该文从屏蔽效能测试基本原理入手，分析了现行标准中材料屏蔽效能的主要测试方法，并通过平面屏蔽材料试验验证，对比了GB/T 12190-2006和GB/T 30142-2013中屏蔽室窗口测试法的差异性，进一步试验了不同天线测试距离和校准参考方式对测试结果的影响，以期为屏蔽材料的设计和装备整体规划提供一定的指导。 Shielding effectiveness, a measure of the ability of a shield to isolate or limit electromagnetic waves, is the main indicator of shielding materials. Therefore, standardizing and appropriately applying shielding effectiveness testing techniques occupy a very influential position. Nowadays, there are dozens of standards for shielding effectiveness testing here, including national standard, national military standard, industry standard, etc. Although the experimental data could be obtained by all of these methods, they are quite different under different test conditions, which hinder the application of shielding materials. Based on the basic principle of measurements of shielding effectiveness, this paper analyzes the main measurements of shielding effectiveness of materials by current standards. Through the verification of test of flat screen materials, it compares the differences of shielding enclosure measurements between GB/T 12190-2006 and GB/T 30142-2013. Further, various antenna testing distances and calibration references are tested to provide some guidance for shielding material design and equipment integrated planning.

Measuring visual enclosure for street walkability: Using machine learning algorithms and Google Street View imagery

One major limitation currently with studying street level urban design qualities for walkability is the often inconsistent and unreliable measures of streetscape features across different field surveyors even with costly training due to lack of more objective processes, which also make large scale study difficult. The recent advances in sensor technologies and digitization have produced a wealth of data to help research activities by facilitating improved measurements and conducting large scale analysis. This paper explores the potential of big data and big data analytics in the light of current approaches to measuring streetscape features. By applying machine learning algorithms on Google Street View imagery, we generated objectively three measures on visual enclosure. The results showed that sky areas were identified fairly well for the calculation of proportion of sky. The three visual enclosure measures were found to be correlated with pedestrian volume and Walk Score. This method allows large scale and consistent objective measures of visual enclosure that can be done reproducibly and universally applicable with readily available Google Street View imagery in many countries around the world to help test their association with walking behaviors.

Performance validation case study: Federal office building with an integrated facade

The General Services Administration Edith Green Wendell Wyatt building has undergone an extensive retrofit and is distinguished by its new integrated facade.1 It has been transformed from a poorly performing office building into a highly efficient Leadership in Energy and Environmental Design (LEED) Platinum facility. The unitized curtain wall includes fixed exterior shading tuned for each solar orientation. The new interior environment optimizes daylight and electric lighting, thermal comfort, and air quality. This article reports on post-occupancy evaluations to validate and fine-tune the performance of Edith Green Wendell Wyatt building. The focus is on post-occupancy evaluation studies that relate to the integrated facades. Overall, post-occupancy evaluations address three categories: (1) resource use and generation—energy and water, (2) occupant satisfaction, and (3) indoor environmental quality measurements. During design, the impact of building enclosure measures and internal loads was linked directly to the selection of the mechanical system. The team determined that strategic use of glazing and exterior shading would support highly efficient hydronic radiant heating and cooling. Post-occupancy evaluation methods include installed data sources (from the building management system and other installed measurement and verification systems) and proposed field testing. Occupant satisfaction has been evaluated with an on-line survey from the Center for the Built Environment. The results have been filtered by solar orientation, floor, and other criteria to understand the facades’ impact on occupant satisfaction. Pre-occupancy results and additional benchmarking compare the results with government and other general office buildings. As of January 2015, many of the post-occupancy evaluation studies have been completed, but some are still on-going. Post-occupancy evaluation objectives include: demonstrating federal energy compliance, refining building performance, and providing feedback for future work.

Monitoring the dynamic emission of biogenic volatile organic compounds from Cryptomeria japonica by enclosure measurement

Abstract Research on biogenic volatile organic compounds (BVOCs) emitted from trees is essential in the world since these BVOCs play an important role in the atmospheric process which may further influence on the air quality. However, little is known about BVOCs emitted from trees in the field in Taiwan. Hence, this study intends to establish an enclosure technique coupled with in situ sampling to facilitate the collection of BVOCs emitted from Cryptomeria japonica leaves. Furthermore, the emission model derived from the relationship between emission rate and temperature was applied to estimate the emission of BVOCs in the field. Results from GC–MS showed that the BVOCs emitted from intact leaves contain 14 monoterpenoids and 4 sesquiterpenoid. The emission rate of the major constituent, sabinene, was 0.42 μg h−1 g−1 around noon on September 11, 2013. Sabinene varies with the changing temperature inside the bag. These findings indicated that the enclosure technique can collect the BVOCs emitted from intact leaves and monitor the dynamic changes in emission. Two determinants, basal emission rate (at 30 °C) and β coefficient, of sabinene were further measured, and they were 1.29 μg h−1 g−1 and 0.18 °C−1, respectively. By using these two determinants and data of meteorology and forest resource, the emission of monoterpenes from C. japonica stand was estimated to be 1.13 mg m−2 h−1 in July in Xitou area. Taken together, the results provide valuable information for estimation of BVOCs from tree species in Taiwan for the first time.

Design of Enclosure for Subway Station Foundation Pit in Southward Extension Line of Chengdu Metro Line One

This paper summarizes the design of open-cut subway station in Chengdu Metro line one. The station is built by cut and cover method and divided into three special parts with four different cross-sections used for main line and transfer track. Such retaining techniques as bored piles, steel pipe struts, soil nails, rock-bolts, steel-meshes, shotcrete and anchored steel cables are comprehensively used to maintain the stability of foundation pit. The anti-buoyancy coefficient of the open cut station is also derived and attains the requirement of safety and stability for the foundation pit after the utilization of these enclosure measures. The application of the design and construction technique for the subway station may provide guidance for the building of analogous subway station under similar geological and hydrogeological conditions in Chengdu.

Contribution of leaf and needle litter to whole ecosystem BVOC fluxes

Biogenic volatile organic compound (BVOC) emissions come from a variety of sources, including living above-ground foliar biomass and microbial decomposition of dead organic matter at the soil surface (litter and soil organic matter). There are, however, few reports that quantify the contributions of each component. Measurements of emission fluxes are now made above the vegetation canopy, but these include contributions from all sources. BVOC emission models currently include detailed parameterization of the emissions from foliar biomass but do not have an equally descriptive treatment of emissions from litter or other sources. We present here results of laboratory and field experiments to characterize the major parameters that control emissions from litter.Litter emissions are exponentially dependent on temperature. The moisture content of the litter plays a minor role, except during and immediately following rain events. The percentage of carbon readily available for microbial and other decomposition processes decreases with litter age. These 3 variables are combined in a model to explain over 50% of the variance of individual BVOC emission fluxes measured. The modeled results of litter emissions were compared with above-canopy fluxes. Litter emissions constituted less than 1% of above-canopy emissions for all BVOCs measured. A comparison of terpene oil pools in litter and live needles with above-canopy fluxes suggests that there may be another canopy terpene source in addition to needle storage or that some terpene emissions may be light-dependent.Ground enclosure measurements indicated that compensation point concentrations of BVOCs (equilibrium between BVOC emission and deposition) were usually higher than ambient air concentrations at the temperature of the measurements.

Qualitative and Quantitative Characterization of Volatile Organic Compound Emissions from Cut Grass

Mechanical wounding of plants triggers the release of a blend of reactive biogenic volatile organic compounds (BVOCs). During and after mowing and harvesting of managed grasslands, significant BVOC emissions have the potential to alter the physical and chemical properties of the atmosphere and lead to ozone and aerosol formation with consequences for regional air quality. We show that the amount and composition of BVOCs emitted per unit dry weight of plant material is comparable between laboratory enclosure measurements of artificially severed grassland plant species and in situ ecosystem-scale flux measurements above a temperate mountain grassland during and after periodic mowing and harvesting. The investigated grassland ecosystem emitted annually up to 130 mg carbon m(-2) in response to cutting and drying, the largest part being consistently represented by methanol and a blend of green leaf volatiles (GLV). In addition, we report the plant species-specific emission of furfural, terpenoid-like compounds (e.g., camphor), and sesquiterpenes from cut plant material, which may be used as tracers for the presence of given plant species in the ecosystem.

Determination and potential importance of diterpene (kaur-16-ene) emitted from dominant coniferous trees in Japan

Reactive volatile organic compounds (VOCs) are known to affect atmospheric chemistry. Biogenic VOCs (BVOCs) have a significant impact on regional air quality due to their large emission rates and high reactivities. Diterpenes (most particularly, kaur-16-ene) were detected in all of the 205 enclosure air samples collected over multiple seasons at two different sites from Cryptomeria japonica and Chamaecyparis obtusa trees, the dominant coniferous trees in Japan,. The emission rate of kaur-16-ene, was determined to be from 0.01 to 7.1μgdwg−1h−1 (average: 0.61μgdwg−1h−1) employing branch enclosure measurements using adsorbent sampling followed by solid phase–liquid extraction techniques. The emission rate was comparable to that of monoterpenes, which is known major BVOC emissions, collected from the same branches. In addition, total emission of kaur-16-ene at 30°C was estimated to exceed that of total anthropogenic VOC emissions.