Artificial Canopy Research Articles

EvaSprayViti: A flexible test bench for comparative assessment of the 3D deposition efficiency of vineyard sprayers at multiple growth stages

The main approach to protect grapes against diseases involves the use of plant protection products. Understanding the quantitative amount and the distribution of these products on the vines is essential to assess the effectiveness of spray equipment and to evaluate the relationship between dosage and response when targeting pathogens. Improving the targeting of sprayers is an important lever to reduce the quantities of phytosanitary inputs applied, taking into account various cropping systems and training. For this purpose, a regularly distributed artificial canopy, adjustable in height and width was designed to mimic three grapevine growth stages for two of the most common trellised training systems encountered in France for ‘wide row vineyards’ (Royat cordon and Guyot, inter-row width 2.5 m). This artificial canopy was evaluated with the perspective of using it as a testing facility for classifying sprayers. Using a dye tracer, spray deposits were directly recovered after the rinsing of artificial leaves. A first series of experiments defined the most adapted sampling strategy in the canopy according to the crop stage, with the comparison of two contrasted sprayers. A second series of experiments compared the quantities of deposits obtained from both the artificial and a real vine, for several sprayers at a full growth stage and for one sprayer at three growth stages. Deposition patterns and mean deposits on both targets were found comparable, allowing a realistic perspective for the classification of spray application modalities using the artificial vine. A third series of experiments compared deposition at three crop stages on artificial and real vines for one type of sprayer. A fourth series of experiments on the artificial vineyard discriminated between three behaviour classes within 65 spraying modalities that combined sprayer types and sprayer settings (such as nozzle types). The discrimination was achieved using a PCA analysis that confirmed the soundness of the sampling strategy used. Overall, these results highlight the ability of the EvaSprayViti test facility to assess and rank the performance of vineyard sprayers.

Recommendations for the establishment of a trans-island canopy bridge network to support primate movement across Langkawi Island, Malaysia

AbstractThe expansion of transportation and service corridors has numerous, well-documented adverse effects on wildlife. However, little research on this topic has been translated into mitigating the effects of habitat fragmentation caused by road development on primates. The establishment of canopy bridges has proven to be an effective conservation intervention. Of the completed primate canopy bridge projects reported in the literature, to our knowledge, all attempt to mitigate the impacts caused by singular, linear infrastructure routes. Here we provide recommendations for the establishment of a network of natural and artificial canopy bridges over roads throughout Langkawi Island, Malaysia, to reduce rates of roadkill and support the movement of primates and other arboreal animals across the island by identifying suitable sites and appropriate tree species to be planted (including Ficus racemosa and Ficus fistulosa), bridge materials and post-installation monitoring. The establishment of this pioneering trans-island canopy bridge network could function as a model to enhance connectivity for arboreal animals in other important wildlife habitat sites in Malaysia and beyond that are affected by fragmentation from linear infrastructure. We have begun discussions with relevant authorities, partners and other pertinent parties, focusing on the initiation of construction of the canopy bridge network in 2024.

Effects of artificial canopy shading on vegetative growth and ripening processes of cv. Nero d'Avola (Vitis vinifera L.).

The biology of the grapevine (Vitis vinifera L.) is clearly influenced by the climatic conditions of the growing environment, where temperature and light play a major role in modifying plant physiology. In the scenario of climatic changes, radiative excess, correlated to the increase in temperature, can concretely subject the photosynthetic apparatus to a condition of light saturation and cause a drastic reduction in photochemical efficiency, giving rise to chronic photoinhibition phenomena. Undoubtedly, the ripening behavior also undergo evident alterations; the problem of sugar ripening, which is often strongly accelerated, is induced not only by high temperatures but also by the excess concentration of carbon dioxide (CO2), which results in a higher ripening. In addition, high berry temperatures favor a reduction in the concentration of organic acids. The reported trends indicate that the need for urgent action is closely linked to the future environmental impacts that these changes could have on the entire wine sector. In recent years, shade treatments have been applied to the vine canopy to overcome this issue. The objective of this study was to determine how artificial canopy shading affects the vines vegetative growth and the ripening processes of Vitis vinifera cv. Nero d'Avola during the 2019-2020 vegetative seasons. Three treatments were established: shading treatment with a green net (shade factor 27%), shading treatment with a white net (shade factor 32%), and untreated vines, thus naturally exposed to light radiation. Artificial shading, applied at full fruit set, interfered with the microclimate of the vines, causing partial effects on the grape ripening processes. At harvest, significant differences were found between the treatments in terms of sugars, also shading treatments increased must acidity and decrease pH. Results obtained on vegetative parameters, suggest that the shading treatment delays leaf fall, with potentially positive effects on the starch accumulation on perennial reserve organs to be exploited at the following season's sprouting. Shading significantly reduced berry size, with obvious consequences on bunch weight and yield per vine. In 2020, shaded plants showed a delay in all the phenological phases. The total anthocyanins content was not changed by the shading treatment. The results obtained confirm the importance of net coverage on the microclimate of the vines, vegetative-productive activity, and grapes quality. From this point of view, the net covering technique can be a tool for controlling grapes ripening dynamics in the context of climate change.

A study of waterside microenvironmental factors and their effects on summer outdoor thermal comfort in a Cfa-climate campus

Outdoor thermal comfort (OTC) studies explore outdoor subjects’ responses to their thermal environment, usually evaluated using the neutral temperature (NT). This study investigated the influences of microenvironmental factors around a waterbody on thermal perceptions, using questionnaires and meteorological measurements at the Central Lake of Southwest University of Science and Technology (SWUST) in Mianyang. Microenvironmental factors included sky view factor (SVF) and distance from the lake (DFL). It was found that people felt most comfortable in the shade of trees although some volunteers voted artificial canopy as their preferred thermal adaptation element. In addition, a linear regression yielded an NT of 28.44 °C in Mianyang during the summer of 2022. There were NT variations among different measurement sites (e.g., on the east shore, it was 28.18 °C on the waterside, 27.11 °C away from the lake, and 25.53 °C far from the lake; while it was 27.57 °C under the tree crown, 25.11 °C on the lawn, and 29.13 °C in the square). This variation may be due to human adaptation towards microenvironmental factors and their effects on microclimate. The variation in thermal responses owing to microenvironmental differences (different NTs at various types of sites) might be a novel finding in the field of OTC. This study provides important directions for microenvironment design in the future for OTC improvement.

Group densities of endangered small apes (Hylobatidae) in two adjacent forest reserves in Merapoh, Pahang, Malaysia

Small ape habitat is rapidly declining due to anthropogenic activities but the current population status of this endangered primate family in Malaysia remains unknown. Group densities of Hylobates lar and Symphalangus syndactylus in two adjacent forest reserves across the Sungai Yu Ecological Corridor (SYEC) in Merapoh, a critical connectivity area of the Central Forest Spine, were assessed. Vegetation assessment and satellite imagery were used to identify habitat characteristics and fixed-point active acoustic triangulation at six listening areas was conducted to estimate small ape group densities. Small ape habitat quality was high in the forested areas of the SYEC. The mean group density of H. lar across these six areas was 3.55 ± 0.9 groups km-² while the mean group density of S. syndactylus was 2.75 ± 1.0 groups km-². The mean group densities of small apes at SYEC were moderately high, compared with densities at other sites in the region, which suggests that the forests here constitute good habitat for both species, despite some observed anthropogenic disturbances. Both species occurred in all listening areas. A nationwide population census for small apes and regular monitoring to inform conservation planning are recommended. Further improvement to connectivity across the SYEC by installing artificial canopy bridges for arboreal animals is important to support the movement of small apes across habitat fragments in Merapoh.

The Javan Gibbon (Hylobates moloch) Habitat Changes and Fragmentation in the Dieng Mountains, Indonesia

The endangered javan gibbon (Hylobates moloch) has been threaten by massive habitat loss and fragmentation in Java. The survival of the second largest population which inhabited unprotected Dieng mountains faced greater risk to habitat conversion and fragmentation. The landscape-level habitat monitoring using spatiotemporal quantification is crucial as a baseline data for javan gibbon conservation. Here, the land-use and land-cover (LULC) change of the Javan gibbon habitat during 1994–2009–2021 and its fragmentation in the Dieng mountains were quantified. This study revealed there were no significant decline in the total of forest. However, its quality was degraded in the interior of forest block. The forest has more fragmented from large patches into smaller patches and increased forest edge. The higher fragmentation happened in the areas that traversed by road. Six suitable forest blocks were identified with varying level of connectivity. Protection and restoration both in the forest and in the interior forest is immediate need, especially in the main forest block. The extra effort is also crucial in the connected forest but traversed by road. The blocks which closely isolated by road could be potentially reconnected by artificial canopy bridge, while the other distantly isolated block might need habitat restoration for corridor.

Improving the accuracy of timber volume and basal area prediction in heterogeneously structured and mixed forests by automated co-registration of forest inventory plots and remote sensing data

Accurate georeferencing is essential if forest indicators, such as timber volume, are to be modelled and predicted area-wide by establishing a linkage between local inventories and remote sensing data. Nevertheless, due to inaccuracies in global navigation satellite system (GNSS) measurements under a closed canopy, determining the exact position of sample-plots in a forest inventory is a major challenge. In this study different methods were evaluated, each of which is designed to improve the co-registration between field measurements and remote sensing data in a forest inventory. The methods were evaluated in two areas in Switzerland (Bremgarten and Zurich), all of which have heterogeneously structured and mixed forests. A simple algorithm that searches for the best match between tree-tops, detected in remote sensing data, and an inventory tree-top point-cloud led to unsatisfactory results. The failure of the algorithm was primarily related to the lack of accurate single-tree-identification (STI) methods in airborne laser scanning (ALS) data (10 points m−2) on deciduous and mixed forest stands. These inaccuracies hampered a successful co-registration of the two data sources. To omit the single-tree-identification (STI) step, methods that rely on the comparison between an artificial canopy height model (CHM) calculated from the inventory data and the CHM generated from ALS data were tested. Correlating the two CHMs made it possible to identify plausible positions within the search range. The quality of all co-registration methods was assessed by the leave-one-out cross-validated root-mean-squared error (RMSE) of the timber volume estimate of the subsequently calibrated regression model. The best results were achieved with a method that modelled inventory tree-crowns as spheres and that applied a correlation metric named SQDIFF_NORMED. Co-registration made it possible to increase the model accuracy of timber volume estimates in Bremgarten by 31 RMSE-%, i.e. from 134.4 m3 ha−1 (without co-registration) to 92.6 m3 ha−1 with co-registered positions. Additional testing of the identified superior method with a larger inventory dataset of the canton of Zurich, Switzerland confirmed these results. There, the RMSE of the basal-area estimate was improved by 10 RMSE-%, from 13.56 m2 ha−1 to 12.18 m2 ha−1. For these CHM-based methods, integrating the information from a deciduous–evergreen (DecEv) raster improved the positional accuracy but not the overall predictive power of the regression models.

The effectiveness of artificial canopy bridges for the diurnal primates within a hydroelectric project in North Sumatra-Indonesia

Abstract Primates that live within fragmented and disturbed habitat are facing population declines and a higher probability of extinction due to gene flow inhibition. To address this problem, land managers, practitioners, and primatologists have applied several approaches to enhance primates’ habitat quality and connectivity through habitat restoration and canopy bridge installation. In some cases, artificial canopy bridges have shown to be effective to facilitate movement between fragmented habitats for several primates’ taxa. However, while several types of canopy bridge designs are available, there is no clear evidence on which is the best for primates. Here we evaluated the effectiveness of three artificial canopy bridge designs within a hydroelectric project in Sumatra, Indonesia from 2019 to 2021. The hydroelectric project was located at the edge of a forest block within the Batang Toru Ecosystem which could disconnect the primate’s population from this protected forest to the other forest blocks. During 595 days of camera trapping, we captured 988 independent crossing events from six diurnal primate species (Pongo tapanuliensis, Hylobates agilis, Symphalangus syndactylus, Presbytis sumatrana, Macaca nemestrina, and Macaca fascicularis). Our initial observation finds the ladder canopy bridge design was commonly used by primates and Presbytis sumatrana was the species that often crossed the canopy bridge. These findings are important to improve species management plans and primate conservation in Indonesia.

Can electrical wires serve as canopy bridges? A case study of the dusky langur (Trachypithecus obscurus) in Thailand

Abstract In many parts of the world, primates and other arboreal and semi-arboreal species use electrical and telecommunication cables to cross open gaps. However, electrocutions can occur when the cables are uninsulated or damaged. Between 2001 and 2002, during a 12-month behavioural study of two dusky langur groups (Trachypithecus obscurus) at the Royal Thai Air Force Base in Prachuap Khiri Khan Province, peninsular Thailand, we recorded langur use of and mortality on electrical and telecommunications cables on an ad libitum basis. Before insulation of the cables in late 2001, five langurs died by electrocution; post insulation, that number decreased to only one case on March 5, 2002. In 2022, we returned to observe the langur groups and saw them continuing to use the cables for crossing and noted damage to the insulation, indicating the importance of maintenance. Electrical cables can provide canopy connectivity for langurs and prevent dangerous encounters with dogs on the ground, but cables must be insulated and inspected regularly. As additional mitigation measures, we suggest providing alternative substrates for travel such as planting more native trees and providing artificial canopy bridges.

Rush hour: arboreal mammal activity patterns in natural canopy bridges in the Peruvian Amazon

Abstract Canopy bridges are an increasingly popular method to mitigate linear infrastructure fragmentation impacts, but little is known about when, over the course of the day and night, they are used. Natural canopy bridges monitored with camera traps provide an excellent source of information on community-wide arboreal mammal activity patterns, which are otherwise challenging to document. Natural bridges represent a hotspot of activity, being bottleneck crossing points over linear infrastructure, and cameras provide 24-hour monitoring capability. We monitored 20 natural canopy bridges over pipeline clearings distributed at two sites in the Peruvian Amazon for over a year using camera traps. Across 11 492 camera trap nights, we recorded 5165 events of 27 arboreal mammal species and used these events to describe both overall mammal activity in natural canopy bridges and activity patterns for the most frequently registered species: Aotus nigriceps, Potos flavus, Bassaricyon alleni, Caluromys lanatus, Coendou ichillus, and Sapajus apella. The long duration of our study allowed us to investigate potential changes in activity patterns resulting from seasonality and disturbance associated with pipeline construction, and the inclusion of two study sites allowed comparisons between them. We found substantially more mammalian activity in bridges during the night (87.4%) than the day, with only one of the most frequently registered species being diurnal (S. apella). Changes in activity between disturbance phases and seasons were only apparent for C. ichillus, and comparisons across species revealed differences in activity peaks, such as a unique peak early in the night for A. nigriceps. Our data provide some of the first substantial activity information for the species evaluated and help elucidate temporal patterns of canopy bridge usage to be expected for arboreal Neotropical wildlife. Knowing when to expect bridge use helps both guide the design of mitigation plans for future projects that include natural and artificial canopy bridges and identify the best monitoring methods. Given the high rate of nocturnal activity we observed, we recommend mitigation plans consider limiting human activity on linear infrastructure at night, if possible, and consider the requirements of nocturnal species in bridge designs. We also recommend camera trapping for monitoring.

Movement dynamics of gibbons after the construction of canopy bridges over a park road

Abstract Gibbons (Hylobatidae) are species highly adapted to tree-top living. Thus, their movement can be compromised due to the negative impact roads have on canopy habitats. In this study, we built two single-rope artificial canopy bridges and a ladder bridge at two out of five locations where a group of white-handed gibbons (Hylobates lar) in Khao Yai National Park, Thailand were known to cross a main park road. We compared road crossing frequencies, home-range characteristics, and other ad libitum observations during the periods before and after bridge installation. After bridge construction was complete, the group took 10 weeks to use the single rope bridges to navigate over the road. During 442 group follow observation hours and 539 bridge observation hours, 131 crosses over the road were observed. The adult female usually crossed the road first, and the group showed a clear preference for the single-rope bridges over the ladder bridge (92 crossings versus 5). Gibbons crossed the road approximately once a day and crossed mostly at the bridge locations both before and after bridge construction. There were not significant changes in crossing rates from before (crossing between the tree branches and on the ground) to after bridge installation at both the places where bridges were installed (crossing using the bridges). Nonetheless, with more crossings being in the bridges than on the ground after bridge installation, crossings were presumably safer. These findings suggest that gibbons will cross a road on the ground, risking predation, encountering people, or being hit by a vehicle, but artificial canopy bridges provided a safer crossing option since gibbons no longer crossed on the road or jumped across wide gaps at the two locations where bridges were constructed. Maintaining canopy connectivity over roads using artificial bridges logically improves home range connectivity, potentially gene flow, and safety of canopy dwellers. However, connecting areas which were not previously connected should be considered carefully. The new connection could disrupt group dynamics, particularly for species that defend territories, such as gibbons.

Assessing the importance of artificial canopy bridge design for Costa Rican monkeys in an experimental setting

Abstract Although artificial crossing structures are increasingly implemented by conservationists and wildlife managers to connect fragmented wildlife habitat, the study of artificial crossing structure design, particularly of canopy bridges, is an emerging field of study in primatology. We address this issue by evaluating five competing bridge models with varying width, material stiffness, and substrate spacing. We assessed bridge preference and performance by sampling the behavior of three species of Costa Rican monkeys (Alouatta palliata: n = 4, Ateles geoffroyi: n = 3, Cebus imitator: n = 3). In a semi-wild setting, we used focal individual sampling with instantaneous recording once every minute for ten-minute intervals and all occurrences sampling whenever study subjects used the bridge. We hypothesized that monkeys prefer bridges that are more stable, and that are made of materials that resemble tree branches. During nearly 37 sampling hours we observed 119 crossing events. We found that study subjects prefer bridge models that are built using more rigid materials, such as the bamboo pole bridge, or wider bridges that offer more stability than narrower bridges. The bridge type and the materials used to build the bridges are both significant predictors of bridge use. While preference for bridges and their performance varies by species, the bamboo pole bridge model and the horizontal mesh bridge were preferred and performed best in our study. The simple liana bridge model was the least preferred by all species and performed poorly in comparison to the other models. Our findings will help us better understand how design and materials impact the use of canopy bridges by monkeys, which can help improve biological corridors and offer new information for the management and conservation of primates living near infrastructure corridors and other kinds of dangerous matrix.

Mitigating the effect of linear infrastructure on arboreal mammals in dense forest: A canopy bridge trial

SummaryRoads and other linear infrastructure create treeless gaps that can limit the movement of non‐flying, arboreal animals. These negative effects are particularly strong in dense forests, where even narrow infrastructure corridors represent a significant change in habitat structure. Artificial canopy bridges are an increasingly common approach to mitigating the barrier effect of roads and other linear infrastructure on the movement of arboreal mammals; however, questions remain about the success of various designs for different species. Here we conduct an experimental evaluation of the response of a critically endangered possum, Leadbeater's Possum (Gymnobelideus leadbeateri), to two artificial canopy bridge designs: single‐rope bridges and ladder bridges. We found that both bridges were used by Leadbeater's Possum and five other species of arboreal marsupial to cross narrow, forestry roads. However, Leadbeater's Possums crossed ladder bridges 13 times more often than the single‐rope design (average of 564.5 and 41.75 crossings per design respectively). Radiotelemetry conducted on four Leadbeater's Possums prior to bridge installation detected no road crossings, providing preliminary evidence that the bridges improved cross‐road movement. Ladder bridges appear to be the better design choice for a wider range of arboreal marsupials as they were used more frequently, offer greater stability, and provide better predator avoidance than single‐rope designs.

A study of subtropical park thermal comfort and its influential factors during summer

Outdoor thermal comfort is significantly relevant to human's quality of life. Thus, it has been frequently studied by investigators. This study explored people's thermal responses to environments and the subjective factors that might affect thermal comforts with respect to two urban parks in Xindu, a satellite city in the Chengdu Plain (CDP). CDP is located at the southwest of China, which has a subtropical climate. The environment from each of the two parks was studied using current micrometeorology and hoped-for landscape changes (tree canopies, artificial canopies, non-canopying plants, and water surfaces); subjective factors included gender, age, body mass index, clothing isolation, and physical activities. It was found that canopies were the most preferred objective cooling elements, while individual thermal perceptions varied subjectively by age. The highest proportion of volunteers voted for tree canopies as their favourite thermal adjusting element. It was observed that those aged above 55 showed low thermal sensitivity. The remaining group's neutral temperatures (indicated by physiologically equivalent temperature, PET) were close, at approximately 25 °C. This study provides significant direction for future urban planning and landscape design.

Exploring human factors of wildlife conservation along a forest gap using a participatory design-build canopy bridge

Abstract This paper reports the social-cultural findings from building an artificial canopy bridge for mantled howler monkeys (Alouatta palliata) and other arboreal mammals in Puerto Viejo, Costa Rica. We analyzed participatory observation results from participatory designing and building, and camera trap data from monitoring the bridge. This article also discusses how local perceptions towards monkeys, regional developments, and bridge functions inform primate conservation in that region. It examines a broader primate conservation strategy that addresses entangled values and bridge design in a human-centered, peri-urban, and coastal evergreen forest. We found that artificial canopy bridge design is a complex problem related to humans and targeted species. Connecting habitat with artificial canopy bridges in this context is part of a more significant urban planning problem. Bridge material and design are related to animal usage and existing infrastructure and can shape public views that build or jeopardize public trust.

Artificialcanopy bridge use by primates and other arboreal mammals in a fragmented tropical forest of northeast Bangladesh

Abstract Forest fragmentation has resulted in a breakdown in connectivity for arboreal species. Effects of fragmentation are particularly acute in forest patches in densely populated countries, resulting in high mortality in many species attempting to cross roads to travel between forest patches. We evaluated the use of three, single-line artificial canopy bridges made of polypropylene ropes in a forest patch in northeastern Bangladesh. Camera traps were used to determine the extent of bridge use by different species. A total of 1060 events of bridge use by mammals were observed using our artificial canopy bridges over the 157 camera trap days. Eight mammal species, including five primate species, two squirrel species and one palm civet species were recorded using the bridges at varying levels of frequency. The location of the bridge and season influenced bridge use. We did not observe mortality of mammals from road accidents or electrocution during the study period. We suggest that artificial canopy bridges increased connectivity between forest patches and reduced mortality from road accidents and electrocution. We strongly recommend the use of this and other, simple canopy bridges to prevent mortality of arboreal mammals.

Do spider monkeys use artificial canopy bridges to cross linear infrastructure?

Abstract Deforestation impacts canopy connectivity when landscapes are fragmented due to roads and other types of linear infrastructure. Natural canopy bridges become vital to arboreal animals, especially for animals that are reluctant to use the ground. When canopy regrowth cannot occur, artificial canopy bridges have been implemented to mitigate the consequences of linear infrastructure. The aim of our study was to evaluate the evidence for the use of artificial canopy bridges by spider monkeys (Ateles spp.) to cross linear infrastructure that interrupts canopy connectivity. We report details of five cases in which the absence of evidence for spider monkeys using artificial canopy bridges to cross linear infrastructure was based on systematic monitoring. We examined the factors that may constrain spider monkeys to use artificial faunal overpasses and made recommendations for effective artificial faunal overpasses for spider monkeys.

A Comparative Study of Cooling Performance and Thermal Comfort under Street Market Shades and Tree Canopies in Tropical Savanna Climate

Walking through street markets is the most popular outdoor activity in Thailand, promoting local economies and tourism. In the year-round hot and humid conditions, living outdoors with long heat exposure throughout the midday can result in heat-related illness. Artificial shade structures and tree shade canopies are typical cooling strategies to protect market sellers and pedestrians from direct sun exposure and improve outdoor human thermal comfort in the street market. This study investigates microclimate conditions and cooling benefits of typical street market shade structures with different settings—three roofing materials, two roof shapes, and surrounding trees with dense and sparse canopies. The dimension of the single artificial shade was 2 m × 2 m with heights varying 2–2.5 m. The vertical air temperature and sky view factor profiles were measured on winter and summer days. The calculated physiological equivalent temperatures (PET) and thermal comfortable hours beneath different shade structures were assessed using RayMan 1.2 software. A cluster of trees with a dense canopy provided more effective cooling (with a satisfied thermal condition of 9 h) than artificial shade structures. Thermal conditions under the galvanized steel roofing and HDPE tarpaulin plastic roofing shades were cooler than those of polycarbonate roofing shade. Meanwhile, the space beneath the sparse tree canopy had the warmest condition. The temperature reductions beneath the artificial shade structure varied throughout the day, with the maximum reduction occurring during midday and the lowest reduction found in the late morning and late afternoon. Our study demonstrates that the tree canopies and artificial shade structures had limited application for providing comfortable conditions throughout midday. To reduce such extreme heat, a combination of shade structures with other cooling techniques is suggested, which should be the focus for further studies.

Crop water stress index computation approaches and their sensitivity to soil water dynamics

There is a growing interest of using canopy temperature (Tc) based methods, including crop water stress index (CWSI), for irrigation management. However, different approaches exist to normalize Tc to microclimatic conditions, which can influence the accuracy and suitability of CWSI for irrigation scheduling. This study evaluated the performance of CWSI computation approaches and their sensitivity to changes in soil water depletion under different water stress levels. There were six different approaches – two empirical methods using developed lower baseline (i.e., CWSI-EB1, CWSI-EB2), two empirical methods using either artificial (CWSI-EA) or actual/natural (CWSI-EN) canopy reference surfaces, and two theoretical approaches which differ by how aerodynamic and canopy resistances are determined (CWSI-Th1, CWSI-Th2). Stationary infrared thermometers (IRTs) provided continuous Tc to calculate CWSI-EB, CWSI-Th, and CWSI-EN; whereas mobile IRTs and a thermal camera provided one-point-in-time Tc and temperatures of artificial canopy reference surfaces to calculate CWSI-EA. These measurements were all collected from full and deficit irrigated and rainfed maize plots in West Central Nebraska. Day-to-day variations within and across CWSI approaches were evident and their sensitivity to soil water depletion varied. Greater sensitivity and correlation strength to depletion (Dr,i) were observed with CWSI-Th and CWSI-EB under severe stress (i.e., Dr,i > 80%) at deeper soil depths of 1.8 and 2.1 m, producing r2 which ranged from 0.61 to 0.80 (slope: 0.03–0.05) and 0.69–0.79 (slope: 0.03–0.04), respectively. Observed differences in stress magnitudes among approaches and treatments, warrants a specific irrigation triggering threshold for each approach. Additionally, developing a robust index coupling both CWSI and soil water depletion is desirable to improve irrigation water management by accounting for both soil and plant water status.

Assessing soil organic carbon, N and P stocks and its relation to soil properties in artificial canopy gaps in a managed oriental beech (Fagus orientalis L.) forest#

AbstractBackgroundIn the Hyrcanian temperate forests, different canopy gaps sizes have been created by logging under silvicultural methods. Understanding the effects of gaps on forest ecosystems can help in the planning and decision‐making of forestry practices. Variations in ecological conditions caused by canopy gaps may have an impact on the forest stand, particularly soil nutrients.AimsThe purpose of the present research was to investigate the changes in soil organic carbon (SOC), total nitrogen (N) and phosphorus (P) stocks under different gap sizes in the Hyrcanian oriental beech forest.MethodsWe measured SOC, N and P stocks of soil at the depth of 0–20 cm among 15 artificial gaps along with adjacent closed stand which was created by single‐tree selection system in oriental beech stand, northern Iran. In the center and four cardinal positions of the edge of gaps as well as in the four adjacent closed canopy forests at the distance of 20 m from gaps, the soil sampling was performed.ResultsThe difference in C, N and P stocks among the artificial canopy gaps was statistically significant, and higher mean values were observed in large gaps. No significant difference was observed between gaps and adjacent closed stands with regard to soil C, N and P stocks. At artificial gaps and closed stands, the SOC stock was negatively correlated with clay and positively correlated with bulk density, sand, N and OC. With increasing bulk density, sand, N, P, and OC, N stock was increased in gaps. In gaps, SOC and P stocks were both positively related to soil microbial C and soil microbial P, respectively.ConclusionGenerally, it can be stated that there are similar relative ecological conditions between artificial gaps and closed stands, and the interaction among soil properties in gaps demonstrates gap dynamics in deciduous, broad‐leaved beech forest.