Shrub Canopy Research Articles

Assessment of Regulatory Ecosystem Services of Amasya University Hakimiyet Campus

Background: Population growth, increasing vehicle numbers, unplanned urbanization and rural-urban migration are reducing green spaces and exacerbating environmental problems such as air, water and noise pollution. In this context, university campuses serve as important small-scale urban models that play a crucial role in maintaining environmental and social well-being within urban ecosystems. Objectives: To evaluate the regulating ecosystem services provided by the tree canopy at Amasya University Hâkimiyet Campus (AUHC), such as air quality, energy savings, and carbon storage. Method: In this study, the land cover and ecosystem services of the AUHC were assessed using the i-Tree Canopy model. Six land cover classes defined for the study area (tree/shrub, grass/herbaceous vegetation, soil/bare ground, impervious buildings, impervious roads, other impervious surfaces) were assessed using 4000 random points and ecosystem services such as air quality were calculated. Results: The tree and shrub canopy covering 31.30% of the AUHC removes 261.53 kg of gaseous and particulate pollutants from the air annually, sequesters 36.57 tons of carbon, and stores a total of 918.42 tons of carbon. The economic value of these ecosystem services was calculated as $758 for air pollution removal and $44420 for carbon storage. The land cover distribution of the campus shows that 57.35% consists of impervious surfaces (buildings, roads) and 42.05% is green space. Conclusion: The tree canopy at the AUHC makes a significant contribution to ecosystem services such as improved air quality, carbon sequestration and storage, and these contributions and economic benefits could be further enhanced by increasing tree cover.

Assessing how Grazing Intensity Affects the Spatial Distribution of Soil Properties

AbstractGrazing activities occupy the largest land surface, making their management crucial for addressing key issues related to the sustainability of agroecosystems. This study seeks to identify the influence of grazing intensity and vegetation cover on the spatial distribution of soil properties in a farm located in a dehesa ecosystem (SW, Spain). To achieve this, 144 soil samples were collected at 0–5 and 5–10 cm depths across six grazing intensity classes (GIC) defined by the current spatial distribution of vegetation canopy. Leveraging 25 environmental covariates, five individual machine learning algorithms (MLAs) and an ensemble model were employed, to predict soil property values. Metrics such as R2, RMSE (root mean square error), and CCC (Lin’s concordance correlation coefficient) were used to determine the best-performing model. The results revealed that high-intensity grazing classes showed higher values of soil nutrients, and SOC (soil organic carbon)than low-intensity grazing classes. Nevertheless, there no significant differencesin areas with shrub and tree canopy cover. Also, the results reveld that different between depth interval were higher in high-intensity class than in low-intensity classes. The study highlights the importance of selecting environmental variables for accurate soil property prediction. The best model depend on soil property selected and depth interval. In conclusion, this studyoffers valuable insights into grazing intensity and vegetation’s influence on soil properties in dehesa ecosystems, guiding future studies in this field.

Characteristics and community stabilities of the resource islands formed by Salix paraplesia shrubs in the mobile sandy land of the upper reaches of the Yellow River in Sichuan Province

This study comprehensively analyzes the physical and chemical properties of soil across different layers under Salix paraplesia shrubs, comparing these properties inside and outside the shrub canopies. It also examines species diversity and community stability in these areas, discussing the impact of soil from resource islands at different formation stages on vegetation restoration. Focusing on Salix paraplesia shrubs over varying restoration periods (45 years, 25 years, and 13 years), with unrepaired mobile sandy land serving as the control, the results are as follows: (1) As vegetation restoration progresses, the content of soil organic matter (SOM) and alkali-hydrolyzable nitrogen (AN) significantly increase. After 45 years of restoration, SOM and AN contents are 250.08% and 442.43% higher than in the control. SOM, AN, and total phosphorus (TP) contents are greater under the shrubs than outside the canopies, indicating pronounced fertilizer accumulation. (2) The number of plant species increases during the restoration process, with 18 more species present after 45 years compared to the control. Community diversity is highest after 13 years of restoration, with greater overall diversity outside the canopies than under the shrubs. These differences decrease as restoration progresses. (3) The stability of Salix paraplesia shrub communities is higher outside the canopies compared to under the shrubs. As restoration proceeds, stability differences between these areas diminish. The Euclidean distances for community stability outside and under the canopies are 13.97 and 14.68, respectively, after 45 years, indicating relative stability. (4) In the early stages of restoration, soil carbon (C) and nitrogen (N) significantly impact species diversity, while in the later stages, phosphorus (P) content becomes more limiting. Resource islands enhance plant community stability and vegetation restoration, playing a crucial role in ecological protection and vegetation restoration in the alpine sandy land of the Yellow River's upper reaches.

The microclimatic effects of the native shrub Ephedra californica (Mormon tea) in California drylands.

The impacts of climate change can be profound in many ecosystems worldwide, including drylands such as arid and semi-arid scrublands and grasslands. Foundation plants such as shrubs can provide microclimatic refuges for a variety of taxa. These shrubs can directly influence micro6 environmental measures, and indirectly increase the local environmental heterogeneity as a result. We examined the hypothesis that, in comparison to an open gap, foundation shrubs improve the microclimate beneath their canopy and that microclimate is in turn a significant predictor of annual vegetation. The following predictions were made: 1) mean air temperature (NSAT), ground temperature (SGT), and vapour pressure deficit (VPD) will be significantly lower under the shrubs than in the open microsites; 2) shrub canopy size predicts microclimate; 3) site-level aridity estimates and percent shrub cover influence annual plant abundance and richness; and 4) the site13 level mean of NSAT and VPD predict annual plant abundance and richness. Our study took place in Southwestern California, U.S.A. We used a handheld device with a probe to measure microclimatic variables such as near-surface air temperature (NSAT), near-surface relative humidity (NSRH), and surface ground temperature (SGT) at the shrub species Ephedra californica and in the open gap, across six sites in California, United States. Air temperature and RH were then used to calculate VPD. The mean number of vascular plant species across each site was also recorded. Only SGT was significantly reduced under shrub canopies. Canopy volume was not a significant predictor of all three microclimatic variables, demonstrating that even small, low-stature shrubs can have facilitative effects. Furthermore, total shrub cover and aridity at sites significantly predicted mean plant richness and abundance. There were significantly more plants associated with shrubs and there were significantly more species associated with the open. Mean air temperature and VPD at the site-level significantly predicted vegetation abundance and richness, though microsite-level differences were only significant for richness. Foundation shrubs are a focal point of resiliency in dryland ecosystems. Understanding their impact on microclimate can inform us of better management, conservation, and restoration frameworks.

Shifts in light availability driven by dieback across a marsh‐forest gradient

AbstractEcological zonation in coastal forests is driven by sea level rise and storm‐surge events. Mature trees that can survive moderately saline conditions show signs of stress when soil salinity increases above its tolerance levels. As leaf burn, foliar damage, and defoliation reduce tree canopy cover, light gaps form within the crown. At the forest‐marsh edge, canopy cover loss is most severe; trunks of dead trees without canopies form “ghost forests.” Canopy thinning and light from the edge alter conditions for understory vegetation, promoting the growth of shrubs and facilitating establishment and spread of invasive species that were previously limited by light competition. In this research, we present an analysis of illuminance and temperature in a coastal forest transitioning to a salt marsh. Light sensors above the ground surface were used to measure light attenuation of trees and understory vegetation and to observe the effect of reduced canopies at the forest‐marsh edge. Farther from the marsh, where salinity is lower and trees are healthy, dense canopies attenuate light. We estimate that during the growing season, tree canopies intercept 50% of illuminance on average. Closer to the marsh, canopy thinning, and tree death allow greater light penetration from above, as well as from the adjacent marsh. These illuminance values are further increased by light penetration from the forest‐marsh edge (edge effect). Here, higher illuminance may permit Phragmites australis expansion. At intermediate locations, trees intercept between 32% and 49% of light and the understory shrub Morella cerifera intercepts a further 45% of penetrating light based on comparisons of illuminance above and below shrub canopies. Light penetration from the edge can also be felt. The presence of M. cerifera reduces the air temperature close to the soil surface, creating a cooler summer microclimate. The tree health state is reflected in the canopy size. The canopy patterns and the edge effect are responsible for light availability distribution along forest‐marsh gradients, consequently affecting the understory vegetation biomass. We conclude that during forest retreat driven by sea level rise, tree dieback increases light availability favoring the temporary encroachment of Ph. australis and M. cerifera in the understory.

A multiscale analysis of factors influencing Setophaga striata (Blackpoll Warbler) occupancy and abundance during the nonbreeding season in eastern Colombia

ABSTRACT Setophaga striata (Blackpoll Warbler), one of the few boreal-breeding migratory birds that migrates to the Orinoco and Amazon regions, is experiencing steep population declines. However, knowledge of the species’ distribution and habitat use during the nonbreeding season is limited. Here, we explore how stationary nonbreeding season (December to April) occupancy probabilities vary across regional and landscape scales, and with vegetation structure for S. striata in eastern Colombia. By running single-species, single-season hierarchical occupancy models and N-mixture models, we evaluated how regional (annual precipitation, nonbreeding season precipitation, driest month, elevation, and net primary productivity), landscape (habitat type and % forest in the landscape), and vegetation structure variables influenced occupancy by S. striata. In the regional analysis, occupancy was positively influenced by stationary nonbreeding precipitation and net primary productivity, and was predicted to peak at elevations between 500 and 1,000 m. At the landscape scale, occupancy and abundance were higher in agroforestry systems (in order of magnitude: shade-grown cacao, citrus plantations and silvopastures) than in forested habitats. In relation to vegetation structure, occupancy was negatively correlated with a principal component containing shrub density, canopy height, and canopy cover. Within the Orinoco region, a spatial prediction based on our results supported high occupancy rates in moister areas along and close to the Andean foothills and where the Orinoco grasslands transition into Amazonian forests. Our results highlight the importance of landscapes containing agroforestry systems as stationary nonbreeding habitats for S. striata in Colombia’s Orinoco region and the importance of promoting agroforestry systems, like shade-grown cacao, in areas with higher nonbreeding season precipitation and net primary productivity values in order to increase habitat availability for the species.

Thinning relationships of woody encroachers in a US southwestern shrubland

Thinning relationships of woody encroachers in a US southwestern shrubland

Carboxylation capacity is the main limitation of carbon assimilation in High Arctic shrubs.

Increases in shrub height, biomass and canopy cover are key whole-plant features of warming-induced vegetation change in tundra. We investigated leaf functional traits underlying photosynthetic capacity of Arctic shrub species, particularly its main limiting processes such as mesophyll conductance. In this nutrient-limited ecosystem, we expect leaf nitrogen concentration to be the main limiting factor for photosynthesis. We measured the net photosynthetic rate at saturated light (Asat) in three Salix species throughout a glacial valley in High-Arctic tundra and used a causal approach to test relationships between leaf stomatal and mesophyll conductances (gsc, gm), carboxylation capacity (Vcmax), nitrogen and phosphorus concentration (Narea, Parea) and leaf mass ratio (LMA). Arctic Salix species showed no difference in Asat compared to a global data set, while being characterized by higher Narea, Parea and LMA. Vcmax, gsc and gm independently increased Asat, with Vcmax as its main limitation. We highlighted a nitrogen-influenced pathway for increasing photosynthesis in the two prostrate mesic habitat species. In contrast, the erect wetland habitat Salix richardsonii mainly increased Asat with increasing gsc. Overall, our study revealed high photosynthetic capacities of Arctic Salix species but contrasting regulatory pathways that may influence shrub ability to respond to environmental changes in High Arctic tundra.

Wildfire effects on mercury fate in soils of North-Western Siberia

Arctic soils store 49 Gg mercury (Hg) - an extremely toxic heavy metal, whereas soil Hg can be released to the atmosphere by wildfires. For the first time we investigated the effects of wildfires on the fate of soil Hg in North-Western (NW) Siberia based on GIS maps of areas burned during the last 38years and a field paired comparison of unburned and burned areas in tundra (mosses, lichens, some grasses, and shrubs) and forest-tundra (multi-layered canopy of larch trees, shrubs, mosses, and lichens). These field surveys were deepened by soil controlled burning to assess the Hg losses from organic horizon and mineral soil. The soil Hg stocks in the organic horizon and in the top 10cm of the mineral soil were 3.3±0.6 and 16±3mg Hg m-2 for unburned tundra and forest-tundra, respectively. After the burning by wildfires, the soil Hg stocks decreased to 2.4±0.1 and 6.6±0.2mg Hg m-2 for tundra and forest-tundra, respectively. By the averages annual burned areas in NW Siberia 527km2, wildfires in tundra and forest-tundra released 0.19 and 2.9Mg soil Hg per year, respectively, corresponding to 28% and 59% of the initial soil Hg stocks. These direct effects of wildfires on Hg volatilization are raised by indirect post-pyrogenic consequences on Hg fate triggered by the vegetation succession and adsorption of atmospheric Hg on the surface of charred biomass. Charred lichens and trees accumulated 4-16 times more Hg compared to the living biomass. Blackened burned vegetation and soil reduced surface albedo and slowly increased soil temperatures in Arctic after wildfires. This created favorable conditions for seeding grasses and shrubs after wildfire and transformed burned high-latitude ecosystems into greener areas, increasing their capacity to trap atmospheric Hg by vegetation, which partly compensate the burning losses of soil Hg.

Recruitment responses of shade‐tolerant and heliophilous trees in degraded areas: The necessity of knowing the recruitment autecology of species for effective reforestation decisions

AbstractDirect seeding is a reforestation technique that allows introducing a great variety of tree species in degraded areas with less logistics, but tree establishment rates are usually low because developing plants do not tolerate the high sun exposure, extreme temperatures, and low soil moisture that prevail in these habitats. This leads to the proposal that seeds should be planted beneath shrubs or herbaceous plants that ameliorate harsh abiotic conditions, although this can also trigger interspecific competition and impair the performance of developing trees. This study aimed to test these proposals in dry forests in northwest Argentina. For this, seeds of two shade‐tolerant trees and a heliophilous tree, native to this region, were sowed beneath the canopy of pioneer shrubs and in open spaces with and without herbaceous plants. After 2 years, our findings indicated that shade‐tolerant trees performed better beneath shrub canopies, while the heliophilous tree achieved higher establishment rates in the open spaces. Nevertheless, it seems that herbaceous plants compete with the tree seedlings and, therefore, they should be removed before conducting reforestation programs. Thus, we propose that direct seeding could be an efficient reforestation strategy, but the regeneration autecology of the tree species selected for this task, as well as their competitive ability in the face of the pioneer vegetation, must be carefully evaluated before seeding.

Rainfall partitioning characteristics and simulation of typical shelter forest in Chinese Mu Us Sandy Land

Numerous shelter forests have been established to combat desertification in the Mu Us Sandy Land, China. Shelter forests modify the characteristics of the underlying surface and affect the regional water cycle by altering rainfall partitioning. Understanding the rainfall partitioning process and its controlling factors for indigenous and exotic species is crucial for vegetation restoration and sustainable soil water management. This study developed an event-based rainfall partitioning process for three typical shelter forests. Indigenous vegetation, Amygdalus pedunculata Pall. (A. pedunculata), and two exotic species, Amorpha fruticosa L. (A. fruticose) and Pinus sylvestris var. mongholica Litv. (P. sylvestris), were observed during the rainy seasons (July and August) of 2021 and 2022. The results showed that throughfall, stemflow, and interception loss constituted 71.01%, 8.23%, and 20.76% of rainfall, respectively, for A. pedunculata. The corresponding values were 74.65%, 8.47%, and 16.88% for A. fruticose and 73.27%, 1.44%, and 25.29% for P. sylvestris. Compared with the introduced P. sylvestris, the shrub canopy showed a greater funneling ratio and was conducive to recharging soil water by precipitation. The amount and intensity of rainfall were significantly correlated with the rainfall partitioning characteristics, whereas the correlation between rainfall duration and partitioning was insignificant. Based on the results of the revised Gash model, the stemflow was primarily influenced by the percentage of rainfall diverted to the stemflow. The interception loss for P. sylvestris was primarily influenced by the canopy storage capacity. However, the canopy storage capacity and the ratio of mean evaporation rate to mean rainfall intensity had significant effects on the interception loss in A. pedunculata and A. fruticose. It is necessary to comprehensively consider the vegetation type (tree/shrub and indigenous/exotic species) and the corresponding rainfall partitioning characteristics of shelter forests for the scientific construction and management of shelter forests in the Mu Us Sandy Land.

Soil macrofauna diversity and biomass associated with the “fertility islands” beneath oak trees in a semi-arid woodland

Soil macrofauna diversity and biomass associated with the “fertility islands” beneath oak trees in a semi-arid woodland

Comparative simulation of transpiration and cooling impacts by porous canopies of shrubs and trees

Comparative simulation of transpiration and cooling impacts by porous canopies of shrubs and trees

A comparison and development of methods for estimating shrub volume using drone‐imagery‐derived point clouds

AbstractShrub volume is used to calculate numerous, essential ecological indicators in rangeland ecosystems such as biomass, fuel loading, wildlife habitat, site productivity, and ecosystem structure. Field techniques for biomass estimation, including destructive sampling, ocular estimates, and allometric techniques, use shrub height and canopy widths to estimate volume and translate it to biomass with species‐specific allometric equations. These techniques are time‐consuming and pose challenges, including removal of plant material and training of observers. We compared canopy volume estimates from field‐based measurements with drone‐collected canopy volume estimates for seven dominant shrub species within mountain big sagebrush (Artemisia tridentata subsp. vaseyana) plant communities in southern Idaho, USA. Canopy height and two perpendicular width measurements were taken from 103 shrubs of varying sizes, and volume was estimated using a traditional allometric equation. Overlapping aerial images captured with a DJI Mavic 2 Professional drone were used to create a 3D representation of the study area using structure‐from‐motion photogrammetry. Each shrub was extracted from the point cloud, and volume was estimated using allometric and volumetric methods. The volumetric method, which involved converting point clouds to raster canopy height models with 2.5‐ and 5‐cm grid cells, outperformed the allometric method (R2 > 0.7) and was more reproducible and robust to user‐related variability. Drone‐estimated volume best‐matched field‐estimated volume (R2 > 0.9) for three larger species: A. tridentata subsp. tridentata, A. tridentata subsp. vaseyana, and Purshia tridentata. The volume of smaller shrubs (canopy widths <1 m) was slightly overestimated from drone‐based models. We argue that drone‐based models provide a suitable alternative to field methods, while having the added benefit of being less time‐consuming, with fewer limitations, and more easily scaled to larger study areas than traditional field techniques. Finally, we demonstrate a proof of concept for automating canopy volume estimates using point‐cloud‐based automatic shrub detection algorithms. These findings demonstrate that drone‐collected images can be used to assess shrub canopy volume for at least five upland sagebrush steppe shrub species and support the integration of drone data collection into rangeland vegetation monitoring.

Short and long-term fire effects on soil C and N in an African savanna

Short and long-term fire effects on soil C and N in an African savanna

Plant networks are more connected by invasive brome and native shrub facilitation in Central California drylands

Dominant vegetation in many ecosystems is an integral component of structure and habitat. In many drylands, native shrubs function as foundation species that benefit other plants and animals. However, invasive exotic plant species can comprise a significant proportion of the vegetation. In Central California drylands, the facilitative shrub Ephedra californica and the invasive Bromus rubens are widely dispersed and common. Using comprehensive survey data structured by shrub and open gaps for the region, we compared network structure with and without this native shrub canopy and with and without the invasive brome. The presence of the invasive brome profoundly shifted the network measure of centrality in the microsites structured by a shrub canopy (centrality scores increased from 4.3 under shrubs without brome to 6.3, i.e. a relative increase of 42%). This strongly suggests that plant species such as brome can undermine the positive and stabilizing effects of native foundation plant species provided by shrubs in drylands by changing the frequency that the remaining species connect to one another. The net proportion of positive and negative associations was consistent across all microsites (approximately 50% with a total of 14% non-random co-occurrences on average) suggesting that these plant-plant networks are rewired but not more negative. Maintaining resilience in biodiversity thus needs to capitalize on protecting native shrubs whilst also controlling invasive grass species particularly when associated with shrubs.

Evaluating methods for measuring the leaf area index of encroaching shrubs in grasslands: From leaves to optical methods, 3-D scanning, and airborne observation

Evaluating methods for measuring the leaf area index of encroaching shrubs in grasslands: From leaves to optical methods, 3-D scanning, and airborne observation

Peatland evaporation across hemispheres: contrasting controls and sensitivity to climate warming driven by plant functional types

Abstract. Peatlands store disproportionally large amounts of carbon per unit area, a function that is dependent on maintaining high and stable water tables. Climate change is likely to negatively impact carbon storage in peatlands, in part due to increases in vapour pressure deficit (VPD) driving higher evaporation (E) rates. However, the response of E to increasing VPD depends on the dominant vegetation type within peatlands. In this study, we used multiple years of eddy covariance (EC) measurements to compare E regimes at two peatlands with contrasting vegetation types – Kopuatai bog in Aotearoa / New Zealand, dominated by the vascular wire rush Empodisma robustum, and Mer Bleue bog in Canada, a “typical” shrub- and moss-dominated Northern Hemisphere peatland. We examined seasonal variability in E and equilibrium E (Eeq), energy balance partitioning, and the response of E, evaporative fraction (EF), and canopy conductance (gc) to VPD. Mean annual E was 45 % lower than mean annual Eeq at Kopuatai but only 16 % lower at Mer Bleue, demonstrating much greater limitations on E at Kopuatai. In addition, the mean midday (10:00–14:30 local standard time) dry-canopy Bowen ratio (β) at Kopuatai was 2.0 compared to 0.8 at Mer Bleue; therefore, the sensible heat flux (H) dominated over the latent heat flux (LE) at Kopuatai and vice versa at Mer Bleue. The responses of E, EF, and gc to increasing VPD at Kopuatai demonstrated stronger limitations on evaporative water loss for VPD > 0.7 kPa compared to Mer Bleue. The observed limitations at Kopuatai were attributed to strong stomatal control by E. robustum due to the rapid decrease in gc with increasing VPD; however, surface E could also be limited by its dense standing litter. At Mer Bleue, however, E was only weakly limited at VPD > 2 kPa, likely due to weak stomatal control over transpiration by the sparse shrub canopy and relatively large surface E from Sphagnum carpets. As such, the results of this study suggest that E. robustum drives a greater “hydrological resistance” to increasing VPD than the vegetation at Mer Bleue, leading to greater water retention at Kopuatai. This may enable greater resilience of the carbon sink function at Kopuatai to climatic warming and drying than at Mer Bleue.

‘Fertile island’ effects on the soil microbial community beneath the canopy of Tetraena mongolica, an endangered and dominant shrub in the West Ordos Desert, North China

BackgroundThe fertile islands formed by shrubs are major drivers of the structure and function of desert ecosystems, affecting seedling establishment, plant–plant interactions, the diversity and productivity of plant communities, and microbial activity/diversity. Although an increasing number of studies have shown the critical importance of soil microbes in fertile island formation, how soil microbial community structure and function are affected by the different fertile island effect intensities is still unknown. As an endangered and dominant shrub species in the West Ordos Desert, Tetraena mongolica was selected for further exploration of its fertile island effect on the soil microbial community in the present study to test the following two hypotheses: (1) T. mongolica shrubs with different canopy sizes exert fertile island effects of different strengths; (2) the soil microbial community structure and function beneath the T. mongolica canopy are affected by the fertile island, and the strength of these effects varies depending on the shrub canopy size.ResultsThe contents of soil total nitrogen (TN) and available phosphorus (AVP) were significantly greater beneath T. mongolica shrub canopy than outside the shrub canopy. With increasing shrub canopy size, the enrichment of soil TN and AVP increased, indicating a stronger fertile island effect. The structure and function of soil microbial communities, including fungal, archaeal and bacterial communities, are affected by the fertile island effect. An increase in canopy size increased the relative abundance of Ascomycota (Fungi) and Thaumarchaeota (Archaea). For the soil microbial functional groups, the relative abundance of endophytes in the fungal functional groups; steroid hormone biosynthesis, sphingolipid metabolism, and steroid biosynthesis genes in the bacterial functional groups; and nonhomologous end-joining and bisphenol degradation functional genes in the archaeal functional groups increased significantly with increasing T. mongolica canopy size.ConclusionsThese results revealed that T. mongolica had a fertile island effect, which affected the soil microbial community structure and functions, and that the fertile island effect might increase with increasing shrub canopy size. The fertile island effect may strengthen the interaction between T. mongolica shrubs and microbes, which may be beneficial to the growth and maintenance of T. mongolica.

Effects of different land-use planning instruments on urban shrub and tree canopy cover in Zurich, Switzerland

Effects of different land-use planning instruments on urban shrub and tree canopy cover in Zurich, Switzerland