Shrub Canopy Research Articles

Shrubs alter alpha and beta diversity of soil fauna in a semiarid grassland

Shrubs are widely distributed in semi-arid and arid ecosystems. Understanding shrub effects on alpha and beta diversity of soil fauna in arid and semiarid ecosystems could lead to promotion of biodiversity conservation and sustainable management. Yet the extent to which shrubs can influence beta diversity of soil fauna and different body size in arid and semiarid ecosystems is unknown. An investigation of soil fauna, macrofauna, and mesofauna beneath shrub canopy and in open spaces was conducted in the Donddashan Nature Reserve (a semiarid grassland ecosystem in China). Shrubs significantly increased the alpha diversity (richness and Shannon index), but significantly decreased the beta diversity and the nestedness component. Moreover, shrub effects differed among soil fauna of different body size. Shrubs significantly increased the abundance and Shannon index of mesofauna, whereas there were no significant effects on macrofauna between shrubs and open spaces. Shrubs significantly decreased the beta diversity of mesofauna, but significantly increased beta diversity and the turnover component of macrofauna. Piecewise structural equation modelling (SEM) showed that shrubs had an indirect effect on soil fauna diversity through mesofauna diversity. Results highlighted the crucial role that shrubs have in maintaining alpha diversity of soil fauna in arid ecosystem, and also demonstrated the divergent shrub effects on beta diversity of soil fauna, mesofauna, and macrofauna. This suggests a need to examine different taxonomic groups to gain a better understanding of ecological consequences of shrubs.

Response of soil microbial compositional and functional heterogeneity to grazing exclusion in alpine shrub and meadows in the Qinghai-Tibet Plateau.

Soil microorganisms found in shrub-meadow ecosystems are highly heterogeneous and extremely sensitive to grazing, but changes in microbial compositional and functional heterogeneity during grazing exclusion (GE) have been largely overlooked compared to community diversity. We collected soil samples from heavily grazed plots (6.0 sheep/ha) and GE plots (matrix and patch areas in both), and used a combination of next-generation sequencing, vegetation features, and the associated soil property data to investigate the effect of GE on the composition and function of microbial communities (bacteria fungi, and archaea) in 0-10 cm soils. Regarding community composition, the proportions of species in bacteria, fungi, and archaea were 97.3, 2.3, and 0.4%, respectively. GE significantly affected the species diversity of fungi and archaea but not that of bacteria. GE decreased the heterogeneity of bacteria (2.9% in matrix and 6.2% in patch) and archaea (31.1% in matrix and 19.7% in patch) but increased that of fungi by 1.4% in patch. Regarding community function, enzyme diversity and heterogeneity were increased by 10.4 and 9.4%, respectively, in patch after 6 years of fencing, exemplifying a high level of microbial functional redundancy. The Kyoto Encyclopedia of Genes and Genome pathways-cell growth and death, translation, digestive system, and nucleotide metabolism-were functional biomarkers (linear discriminant analysis effect size method) in matrix-non-grazed plots, whereas lipid metabolism, xenobiotics biodegradation and metabolism, and metabolism of terpenoids and polyketides, cell motility, cancer: overview, endocrine system, and membrane transport were biomarkers in patch-non-grazed plots. Additionally, GE improved the capacity for fatty acid metabolism but decreased the abundance of methane-producing archaea by 42.9%. Redundancy analysis revealed that the factors that affected microbial composition the most were soil aggregates, soil moisture, and the number of plant species, whereas those that affected microbial function the most were soil available phosphorus, soil temperature, and shrub canopy diameter. Our results quantified soil microbial heterogeneity, emphasizing the different responses of the composition and function of bacteria, fungi, and archaea to GE in alpine shrubs and meadows.

Evaluating the effects of vegetation and land management on runoff control using field plots and machine learning models.

Excess surface water after heavy rainfalls leads to soil erosion and flash floods, resulting in human and financial losses. Reducing runoff is an essential management tool to protect water and soil resources. This study aimed to evaluate the effects of vegetation and land management methods on runoff control and to provide a model to predict runoff values. Filed plot data and three machine learning (ML) methods, including artificial neural network (ANN), coactive neuro-fuzzy inference system (CANFIS), and extreme gradient boosting (EGB), were used in a test site in the north of Iran. In this regard, plots with various vegetation and land management treatments including bare soil treatment, rangeland cover treatment, forest litter treatment, rangeland litter treatment, tillage treatment in the direction of slope, tillage treatment perpendicular to the slope, and repetition of treatments under forest canopy were constructed on a hillslope. After each rainfall event, the amount of rainfall and corresponding runoff generated in each plot was recorded. Three ML models (ANN, CANFIS, and EGB) were used to establish relationships between amounts of recorded runoff and its controlling factors (rainfall, antecedent soil moisture (A.M.C), shrub canopy percentage and height, tree canopy percentage and height, soil texture (clay, silt, and sand percent), slope degree, leaf litter percentage of soil, and tillage interval). These data were normalized, randomized, and divided into training and testing subsets. Results showed that the ANN performed better than the other two models in predicting runoff in training (R2 = 0.98; MSE = 0.004) and the test stages (R2 = 0.90; MSE = 0.95). Statistical analysis and sensitivity analysis of inputs factors showed that rainfall, rangeland cover, and A.M.C are the three most important factors controlling runoff generation. The adopted method can be used to predict the effect of different vegetation and land management scenarios on runoff generation in the study area and the areas with similar settings elsewhere.

Forest canopy and mistletoe infestation alter the facilitative effects of Juniperus oxycedrus s.l. on woody seedlings on Mount Lebanon (Lebanon)

AbstractQuestionsIn this study we investigated the direct effect of the shrub Juniperus oxycedrus s.l. on Mediterranean woody species regeneration, and how this interaction can be modified by the juniper habit, the forest canopy and/or infestation of the juniper by the plant parasite Arceuthobium oxycedri. We also aimed at identifying species response groups in relation to their ecological requirements and successional strategies.LocationNorth of Mount Lebanon, in Horsch Ehden natural reserve, a humid montane Mediterranean forest.MethodsWe compared the regeneration of all occurring woody species below and outside 111 Juniperus oxycedrus canopies using the random pair sampling method. We calculated eight relative interaction intensity indexes (RIIJuniper) corresponding to the eight treatment combinations of the three factors: forest canopy (forest/gap), mistletoe infestation (with/without) and juniper habit (spreading/erect). We analyzed the RII values at three different levels: community (all species grouped), species group and species.ResultsOverall, the regeneration of the woody community was facilitated by Juniperus oxycedrus. However, the forest cover significantly reduced the facilitative effect of Juniperus oxycedrus when the latter was not infested by Arceuthobium oxycedri. We identified three species response groups (A: highly facilitated; B: slightly facilitated to neutral; and C: neutral) determined by their response to both Juniperus oxycedrus canopy and forest cover. The most facilitated species were shade‐tolerant/drought‐intolerant late‐successional species.ConclusionsThe results suggest the importance of shade tolerance in the complex mechanism of forest regeneration that is also affected by a parasite plant (Arceuthobium oxycedri), which boosts regeneration dynamics under forest cover by reducing shrub canopy cover.

The influence of grass competition and soil moisture on the growth and phenology of Karoo shrubs in the Eastern Upper Karoo

Rainfall in the Nama-Karoo is sporadic and a plant’s ability to access and utilise available soil moisture will determine its ability to persist in the system and to successfully recruit. When summer rainfall in the Eastern Karoo increases, grassiness increases at the expense of shrub canopy cover. This may drive a transition from shrubland toward grassland. The effect of grass–shrub competition on shrub growth and phenology in the Eastern Karoo is not adequately explained by the root–niche separation hypothesis or the succession hypothesis. In an experiment, we measured shrub growth and phenology in the absence (clipping treatment) and presence (control treatment) of grass over the 2017/2018 rainfall season. Grass clipping changed grass species composition over this period, but grass clipping did not benefit shrubs. We found no competitive effect of grasses on shrubs. However, shrub canopy cover showed a strong linear response to soil moisture, as did canopy cover to temperature. Similarly, soil moisture and temperature were important for stem growth and shrub phenology. Patterns of shrub growth and phenology in response to summer and winter rainfall provide important insight for land managers for optimising production while enabling phenological processes that allow recruitment to take place.

Invasive Urban Mammalian Predators: Distribution and Multi-Scale Habitat Selection.

Simple SummaryRestoration of biodiversity in urban green spaces frequently requires eradication or management of invasive species. We aimed to identify fine- and landscape-scale habitat features associated with the presence of five invasive urban mammals (Rattus species, European hedgehogs, mice, and brushtail possums) in three urban green space types (forest fragment, amenity park, residential garden) across three New Zealand cities, and across two seasons, to identify where management effort should be focused. All species were detected in all greenspace types; however, rodents were detected least in residential gardens, possums were detected most often in forest fragments, and hedgehogs least in forest fragments. Proximity of amenity parks to forest patches was positively associated with possum and hedgehog presence and negatively with rats. Conversely, proximity of residential gardens to forest patches was positively associated with rat presence. Management of rats should focus on sites with shrub and lower canopy cover and of mice on sites with herb layer cover, while micro-habitat features were not important for hedgehogs and possums. Rats were most likely to be found in residential gardens with compost heaps. The wide distributions of these species suggest that in order to be successful, ecological restoration must be coordinated, target all green space types, and engage urban residents.A barrier to successful ecological restoration of urban green spaces in many cities is invasive mammalian predators. We determined the fine- and landscape-scale habitat characteristics associated with the presence of five urban predators (black and brown rats, European hedgehogs, house mice, and brushtail possums) in three New Zealand cities, in spring and autumn, in three green space types: forest fragments, amenity parks, and residential gardens. Season contributed to variations in detections for all five taxa. Rodents were detected least in residential gardens; mice were detected more often in amenity parks. Hedgehogs were detected least in forest fragments. Possums were detected most often in forest fragments and least often in residential gardens. Some of this variation was explained by our models. Proximity of amenity parks to forest patches was strongly associated with presence of possums (positively), hedgehogs (positively), and rats (negatively). Conversely, proximity of residential gardens to forest patches was positively associated with rat presence. Rats were associated with shrub and lower canopy cover and mice with herb layer cover. In residential gardens, rat detection was associated with compost heaps. Successful restoration of biodiversity in these cities needs extensive, coordinated predator control programmes that engage urban residents.

Soil nutrients mediate the indirect effects of shrub canopy removal: How distance from shrubs affects the herbs and grasses community in a shrub‐encroached grassland

AbstractUnderstanding community processes is essential to predict community dynamics and succession processes. To explore how shrub canopy removal frequency (hereafter ‘removal frequency’) and distance from shrubs affect herbs and grasses community assembly in a shrub‐encroached grassland, we carried out a 4‐year shrub canopy removal experiment with three removal frequencies (no removal, removal once, and removal twice per year) in a Caragana microphylla shrub‐encroached grassland, and assessed community assembly mechanisms directly beneath shrubs (0 m from shrubs, i.e., in the centre of the shrub) and in shrub interspaces (at least 2 m from shrubs) under each removal frequency treatment using both functional trait‐based and phylogenetic‐based approaches. Removal frequency positively affected standard effect sizes (SESs) of the mean pairwise distance (MPD) for multi‐trait, specific leaf area (SLA) and leaf dry matter content (LDMC), denoted by SES.MPDMulti‐trait, SES.MPDSLA, and SES.MPDLDMC, indirectly via regulating soil nitrogen (N) and soil carbon (C) content, while it negatively affected SES.MPDHeight indirectly via regulating soil available phosphorus (P) content. Distance from shrubs negatively affected SES.MPDHeight indirectly via regulating soil available P content, and negatively affected SES.MPDLDMC indirectly via regulating soil C content. The trait‐based approach was more powerful than the phylogenetic‐based one in explaining the responses of community assembly processes to environmental changes. These findings highlight the importance of shrub canopy removal and distance from shrubs in affecting soil nutrient status and consequently community assembly processes, which provides a new insight into how canopy removal or fertile island effects affect community assembly in the shrub‐encroached grassland regions.

Modeling habitat use and potential distribution of kit fox in the Trans‐Pecos, Texas

AbstractManagement of a species requires knowledge of their distribution and the environmental factors that influence their use of an area. The kit fox (Vulpes macrotis) is a small fox species endemic to the threatened desert grasslands of the western United States and northern Mexico. Little information exists on the status and distribution of kit fox in Texas, USA; however, researchers have documented population declines in the closely related swift fox (Vuples velox) in the Texas Panhandle. Therefore, our objectives were to survey areas of potential kit fox habitat using remote trail cameras to determine use and detection rates for kit fox, evaluate and quantify environmental effects on habitat use, and map potential distribution of kit fox habitat throughout the Trans‐Pecos using results from the preceding occupancy analysis. We conducted camera surveys at 732 baited sites from March 2018 to March 2020, with each survey lasting 14 days on average (~10,248 camera‐days). We detected kit fox at 99 of 732 camera survey sites. We divided surveys into 3‐day sampling occasions and fit single‐season occupancy models to test for an effect of sampling occasion and season on detection and for effects of slope, elevation, shrub height, shrub canopy cover, percent litter, percent herbaceous cover, and bare ground on habitat use. Overall detection was 0.31 ± 0.001 (SE) and was influenced by sampling occasion and season, with detection being highest during November to February and earlier in the survey. Mean probability of use for sites was 0.17 ± 0.01 (range = 0.00–0.85) and was influenced by 4 environmental covariates, with the greatest probability of use in areas with gentler slopes, lower elevations, shorter shrubs, and a greater percentage bare ground. We used the most supported model to make a map of predicted habitat use across the Trans‐Pecos region and showed evidence of model fit. Our work provides detailed baseline information on the distribution and environmental relationships of kit fox in the region and can be used to assist with future research and monitoring efforts.

Fire effects on soil seed banks under different woody plant species in Mazandaran province, Iran

Soil seed banks play a major role in the post-fire regeneration of semi-arid mountain grasslands. Plant species present before fire can determine the soil seed bank (SSB) characteristics in fire-prone ecosystems. However, it remains unclear how the density and species composition of the SSB under the canopy cover of specific shrub species may be affected by fire. Therefore, we designed a study to test the effects of prescribed burning on the viable SSBs under the canopies of two shrub species: Berberis integerrima (with open canopies) and Onobrychis cornuta (with dense canopies). We selected 20 study sites that included separate patches of the two shrub species and nearby herbaceous patches as control. Soil sampling was carried out pre- and post-burning of shrub canopies and the control patch. Soil samples were collected at two depths: 0–5 cm and 5–10 cm, and transported to the greenhouse for germination experiments. The results showed that canopy fire of shrubs decreased SSB density and species richness. However, the effects of shrub burning on SSB were species-specific and these reductions were more pronounced for canopy burning of O. cornuta than for B. integerrima. Total SSB densities decreased by 61% for B. integerrima and 71% for O. cornuta after canopy fire at soil depth of 0–5 cm. At soil depth of 5–10 cm, total SSB density decreased by 45% under O. cornuta after canopy fire, while canopy fire of B. integerrima did not affect SSB density. Herbaceous patch burning had no statistically significant effects on SSB density at soil depths of 0–5 cm and 5–10 cm. The comparison of quantitative and qualitative similarity indices between pre- and post-fire species composition of shrub canopy showed that the statistically significant effect of B. integerrima burning on SSB composition was less pronounced compared with O. cornuta. This study indicated that seeds stored within the soil under certain shrub species are at a high risk of mortality during fire. Thus, successful post-fire recovery does not rely on the seed bank reservoir under these shrubs.

Fuel reduction treatments reduce modeled fire intensity in the sagebrush steppe

AbstractIncreased fire size and frequency coupled with annual grass invasion pose major challenges to sagebrush (Artemisia spp.) ecosystem conservation, which is currently focused on protecting sagebrush community composition and structure. A common strategy for mitigating potential fire is to use fuel treatments that alter the structure and amount of burnable material, thus reducing fire behavior and creating access points for fire suppression resources. While there is some recent information on the impacts of fuel treatments on ecological communities, we have little information on fuel treatment effectiveness at modifying fire behavior in sagebrush ecosystems. We present 10 years of data on fuel accumulation and the resultant modeled fire behavior in prescribed fire, mowed, herbicide (tebuthiuron or imazapic), and untreated control plots in the Sagebrush Treatment Evaluation Project (SageSTEP) network in the Great Basin, USA. Fuel data (i.e., aboveground burnable live and dead biomass) were collected in each treatment plot at Years 0 (pretreatment), 1, 2, 3, 6, and 10 posttreatment. We used the Fuel and Fire Tool fire behavior modeling program to test whether treatments impacted potential fire behavior. Prescribed fire initially removed 49% of the total fuel load and 75% of shrubs, and fuel loads remained reduced through Year 10. Mowing shifted fuels from the shrub canopy to the ground surface but did not change the total fuel amount. Prescribed fire and mowing increased herbaceous fuel by the second posttreatment year and that trend persisted through Year 10. Tebuthiuron treatments were ineffective at altering fuel loads. Imazapic suppressed herbaceous vegetation by 30% in Years 2 and 3 following treatment. The modified fuel beds in fire and mow treatments resulted in modeled flame lengths that were significantly lower than untreated control plots for the duration of the study, with shorter term reductions in reaction intensity and rate of spread. Understanding fuel treatment effectiveness will allow natural resource managers to evaluate trade‐offs between protecting wildlife habitat and reducing the potential for high‐intensity wildfire.

Drought and shrub cover differentially affect seed bank composition within two sagebrush steppe communities

Soil seed banks are critical biodiversity repositories for dryland plant communities. Understanding how environmental factors alter seed bank composition provides valuable information on ecological processes within a community and can be useful for creating land management strategies. We assessed seed bank response to drought and microsite within an Artemisia arbuscula dominated community and a directly adjacent (∼60m apart) A. cana dominated community, and characterized the similarity between these two seed banks and the corresponding aboveground vegetation. We found that drought increased exotic grass seed density and decreased seed species diversity and evenness within the A. arbuscula community, whereas shrub microsites enhanced seed species diversity and native forb seed density. In contrast, there were only minor drought effects within the A. cana community. Within both plant communities, there was low similarity between the seed bank and existing vegetation (<28%), and both seed banks were comprised of over 50% exotic annual grass seeds. Our study suggests that seed banks of drylands similar to A. arbuscula dominated plant communities (with heterogenous landscapes and low soil moisture availability) may experience more drought induced impacts than adjacent sagebrush communities, and highlights the role of shrub canopies as beneficial microsites for seeds in some drylands.

Differential responses of ground-active arthropod abundance and diversity to shrub afforestation in heterogeneous textured soils in desertified grassland ecosystems, North China

Shrub afforestation is an effective way for restoration of soil communities and desertification control in desertified regions. However, little is unknown about how heterogeneous textured soils influence the effectiveness of shrub afforestation on the activities and diversity of ground-active arthropods. In the present study, ground-active arthropods were examined by pitfall trapping as well as by herbaceous performances and soil properties investigated in two shrub microhabitats (the shrub canopy and open spaces) in afforested sandy soil and sandy loam soil of northwestern China. The adjacent shifting sandy land, not covered by shrub plantations, served as a control. Total abundance in the open spaces in afforested sandy soil was significantly (p < 0.05) higher than those in the shrub canopy microhabitats in the same soil type and was also higher than those in both shrub microhabitats (open space and shrub canopy) in afforested sandy loam soil. A consistently (p < 0.05) greater taxa richness and the Shannon index as well as taxa richness of trophic groups (phytophages and predators) was found in shrub microhabitats in both soil types compared to the shifting sandy land. However, no significant differences (p > 0.05) were observed in taxa richness, Shannon index, and the Simpson index of ground-active arthropods, and in the abundance and richness of both trophic groups among the four shrub microhabitats in both soil types. In conclusion, soil textural heterogeneity in terms of soil type had a significant effect on the abundance, but not on the biodiversity distribution and trophic relationship, of ground-active arthropods between shrub microhabitats. The facilitative effect of shrubs benefited a stable biodiversity distribution and thus a stable trophic relationship within ground-active arthropod communities through afforestation practices, regardless of soil type.

Structure and function of soil microbial communities in fertile islands in austral drylands

AbstractFertile islands are an important determinant of ecosystem functioning in drylands. These resource‐rich patches are maintained by complex interactions among biotic and abiotic factors. Soil microorganisms are responsible for essential ecosystem processes and could affect the ability of fertile islands to capture and cycle nutrients, both directly and indirectly enhancing the fertile island effect. In this context, we aimed to evaluate the attributes of soil microbial communities (abundance and activity), elucidate key drivers of the fertile island effect and analyze relationships with a range of soil parameters (physicochemical). The soils under shrub canopies had higher values of microbial biomass carbon (MBC) and soil basal respiration (SBR) rates than soils from intercanopy spaces. However, no differences were observed in Soil Organic Carbon (SOC) or in fungal and bacterial abundances between the microhabitats. Soil nutrient stocks (NPK) and pH values had a positive correlation with MBC and SBR. Also, a positive correlation was observed for fungi abundance and the K content of the soil. We also observed a positive correlation between the bacterial abundance and soil N content. This study suggests thatM. tridenscan be considered a keystone species that generates fertility islands, critical for biodiversity and ecosystem functioning. The keystone role thatM. tridensplays in this system underscores the importance of improving our understanding of these interactions (plant–soil‐microorganisms), especially important as drylands expand and aridity increases due to climate change in the second half of this century.

Specific microbiome signatures under the canopy of Mediterranean shrubs

Shrub encroachment (SE) is a phenomenon in which grasses and herbaceous vegetation are replaced by woody shrubs. Many previous studies have highlighted the effects of SE on soil respiration rates and nutrient storage, but little is known about impacts on soil microbiota. While previous work considered shrubs to be non-species specific or as a single intervening species, we selected an Ampelodemsos mauritanicus grassland and six coexisting shrubs (i.e. Pistacia lentiscus L., Juniperus phoenicea L., Myrtus communis L., Rosmarinus officinalis L., Olea europaea L., and Euphorbia dendroides L.) to investigate the effects of their encroachment on soil microbiota. We used high-throughput sequencing, coupled with soil chemical analyses and litter using 13C CPMAS NMR spectroscopy. Results showed a strong influence of shrub species on bacterial and fungal community diversity, species richness and overall community composition in the soil. Litter chemistry was dominated by O-alkyl-C, with the highest content in Ampelodesmos and E. dendroides, but richer of aromatic C in P. lentiscus and R. officinalis. Bacterial diversity was highest under J. phoenicea and E. dendroides, while lowest under R. officinalis and grassland. Conversely, fungal diversity was highest under O. europaea and E. dendroides, while lowest under M. communis and grassland. Moreover, soil C and N contents were highest under O. europaea, P. lentiscus and M. communis compared to the other shrub species. In addition, grassland and R. officinalis had the highest Fe content. Structural equation model (SEM) analysis ascertained that the shifts of bacterial and fungal community composition and diversity were closely related with the changes of litter and soil chemical properties. Our results suggest that the individual effect of each shrub on the grassland matrix depends mainly on the chemical properties of the shrub litter, which alters the chemical profile of the soil and, in cascade, shapes the associated microbiota.

Shrub facilitative effects on the plant litter arthropod community shifts with decreasing precipitation in desertified ecosystems in northwestern China

Understanding shrub effects on plant litter arthropod community structure in contrasting semiarid and arid grassland ecosystems could lead to the promotion of biodiversity conservation and sustainable management in afforested plantations. An investigation of litter arthropod abundance and diversity beneath the shrub canopy and in open spaces between shrubs was conducted via a litterbag field experiment during two consecutive years in a semiarid and an arid grassland ecosystem. Litter arthropod diversity and abundance were significantly higher in the shrub understory than in open spaces in the arid grassland. Furthermore, a similar abundance of both total mites and predatory mites was found in the shrub understory. However contrasting trends were found in the semiarid grassland. Significantly higher detritivorous mite abundance was found in the open areas between shrubs with no clear facilitation effects on the detritivore community. In conclusion, shrub facilitation could expand biodiversity conservation towards open spaces in extreme arid grasslands. The increasing drought expected for the region under climate change scenarios strengthens the importance of conserving shrub cover in these ecosystems to sustain biodiversity and ecosystem functioning.

自然降雨下黄土丘陵区草灌植物垂直覆盖结构的减流减沙效应

黄土高原是我国水土流失和生态环境问题最为严重的地区之一，植被恢复是防治水土流失的重要措施。植物垂直覆盖结构包括地上冠层、地表枯落物和地下根系，各组分具有不同的水土保持作用，是研究植被与水土流失关系的基本单元。目前，关于植物垂直覆盖结构不同组分对土壤侵蚀影响的研究主要是基于人工模拟降雨，缺少自然降雨条件下不同植物的垂直覆盖结构对产流、产沙和入渗等多过程影响的系统研究。本研究以黄土丘陵区典型的草本（须芒草）、半灌木（铁杆蒿）和灌木（绣线菊）为研究对象，每种植物进行三种处理（自然状态、去除枯落物和仅留根系）以及裸地对照，观测2015-2016年降雨事件的产流产沙量和入渗量，分析植物不同垂直覆盖结构的减流减沙效益及其相对贡献。结果表明：三种植物均具有较好的减流（45.9%-73.2%）、减沙效益（87.5%-94.6%）和增加入渗作用（4.7%-10.8%），灌木的减流效果（73.2%）显著高于草本（45.9%）和半灌木（63.5%），但三种植物间的减沙效益没有显著性差异。冠层的减流作用最大，贡献率接近一半（48%-50%），草本枯落物的减流贡献率与根系基本一致，而半灌木和灌木枯落物的减流贡献率略高于根系。冠层、枯落物和根系的减沙贡献率基本一致（36%、30%和34%），相对而言，草本的根系对控制侵蚀具有更大作用，减沙贡献率达到39%，而半灌木和灌木的冠层减沙贡献率要略高于枯落物和根系。本研究表明，冠层是减流的重要因子，而冠层、枯落物和根系在减沙方面均发挥了重要作用，植物垂直覆盖结构各组分在不同植物间减流减沙能力的差异主要与植物功能性状有关。上述结果将为黄土丘陵区坡面植被恢复和水土流失治理提供科学依据。;The Loess Plateau is one of the areas with the most serious soil erosion and ecological environment problems in China. Vegetation restoration is an important measure to prevent and control soil and water loss. The plant vertical cover structure includes aboveground canopy, surface litter, and underground root system. Each component has a different role in soil and water conservation. It is the basic unit to study the relationship between vegetation and soil erosion. At present, the research on the effects of different components of plant vertical cover structure on soil erosion in loess hilly areas is mainly based on artificial rainfall, and there is a lack of systematic research on the effects of different plants vertical cover structure on runoff, sediment and infiltration under the condition of natural rainfall. The research objects of this study were the typical grass (Andropogon yunnanensis), sub-shrub (Artemisia sacrorum) and shrub (Spiraea pubescens) in loess hilly areas. Each plant was treated with three different vertical cover structure compositions (e.g., intact condition, removing litter and only roots) and bare land control treatment. The runoff, sediment yield and infiltration of rainfall events from 2015 to 2016 were observed. The runoff and soil loss reduction and relative contributions of different vertical cover structures were analyzed. The results showed that the three types of plants had great runoff reduction (45.9%-73.2%), soil loss reduction (87.5%-94.6%), and increased infiltration (4.7%-10.8%). The runoff reduction of shrub (73.2%) was significantly higher than that of grass (45.9%) and sub-shrub (63.5%). However, there was no significant difference in soil loss reduction among the three plants. The canopy had the greatest effect of reducing runoff, with a contribution rate close to half (48%-50%). The contribution of grass litter to runoff reduction was basically the same as that of the roots, while the contribution of sub-shrub and shrub litter was slightly higher than that of the roots. The contribution of canopy, litter and roots to soil loss reduction was basically same (36%, 30% and 34%). In specific, the roots of grass had a greater effect on controlling erosion, and the contribution to soil loss reduction rate reached 39%, while the contribution of sub-shrub and shrub canopy to soil loss reduction rate was slightly higher than that of litter and roots. The study shows that the canopy is an important factor in runoff reduction, while the canopy, litter and roots all play an important role in reducing soil loss. The differences in the ability of the vertical cover structure to reduce runoff and soil loss among different plants mainly related to plant functional traits. The above results will provide a scientific basis for vegetation restoration and soil erosion control on slopes in the loess hilly region.

Shading decreases and delays NDVI and flowering of prostrate Arctic shrubs

Increases in shrub growth and canopy cover are well documented community responses to climate warming in the Arctic. An important consequence of larger deciduous shrubs is shading of prostrate plant species, many of which are important sources of nectar and berries. Here, we present the impact of a shading experiment on two prostrate shrubs, Vaccinium vitis-idaea L. and Arctous alpina L., in northern Alaska over two growing seasons. We implemented three levels of shading (no shade, 40% shade, and 80% shade) in dry heath and moist acidic tundra. Plots were monitored for soil moisture content, surface temperature, normalized difference vegetation index (NDVI), and flowering. Shading was shown to, on average, lower surface temperature (0.7 °C to 5.3 °C) and increase soil moisture content (0.5% to 5.6%) in both communities. Both species- and plot-level NDVI values were delayed in timing of peak values (7 to 13 days) and decreased at the highest shading. Flower abundance of both species was lower in shaded plots and peak flowering was delayed (3 to 8 days) compared with controls. Changes in timing may result in phenological mismatches and can impact other trophic levels in the Arctic as both the flowers and resulting berries are important food sources for animals.

Application of L-band SAR for mapping tundra shrub biomass, leaf area index, and rainfall interception

Rapid shrub expansion has been observed across the Arctic, driving a need for regional-scale estimates of shrub biomass and shrub-mediated ecosystem processes such as rainfall interception. Synthetic-Aperture Radar (SAR) data have been shown sensitive to vegetation canopy characteristics across many ecosystems, thereby potentially providing an accurate and cost-effective tool to quantify shrub canopy cover. This study evaluated the sensitivity of L-band Advanced Land Observing Satellite 2 (ALOS-2) data to the aboveground biomass and Leaf Area Index (LAI) of dwarf birch and alder in the Trail Valley Creek watershed, Northwest Territories, Canada. The σ°VH /σ°VV ratio showed strong sensitivity to both LAI (R2 = 0.72 with respect to in-situ measurements) and wet aboveground biomass (R2 = 0.63) of dwarf birch. Our ALOS-2-derived maps revealed high variability of birch shrub LAI and biomass across spatial scales. The LAI map was fed into the sparse Gash model to estimate shrub rainfall interception, an important but under-studied component of the Arctic water balance. Results suggest that on average across the watershed, 17 ± 3% of incoming rainfall was intercepted by dwarf birch (during summer 2018), highlighting the importance of shrub rainfall interception for the regional water balance. These findings demonstrate the unexploited potential of L-band SAR observations from satellites for quantifying the impact of shrub expansion on Arctic ecosystem processes.

Potensi Vegetasi Semak di Kelurahan Bangkal, Palam dan Sungai Tiung, Kecamatan Cempaka, Banjarbaru

A good urban structure and activity need a green spaces to increase its ecological function. However, trees will not fully be able to fill an important space in urban areas while the shrub woody vegetation has the potential to fill that space. Therefore, the aim of this study is to determine the potential of shrub as a constituent of urban vegetation so it can be used as material information about the planning of land use in the district of Cempaka. This sudy was conducted by determining the three sampling stations and 3 plots of 4m x 4m in wide on each station with data based on a map of shrub green space in District of Cempaka using purposive sampling method, the analysis performed includes the analysis of shrub canopy, measured environmental parameters, and data were analyzed with analysis of canopy volume, Pearson correlation analysis and analysis of Importance Value Index (IVI). Shrub vegetation estimation results indicate that the shrub canopy volume in the district of Cempaka is up to 22,462,878.50 m3 in the bush land area of 5675.116 hectares. Pearson correlation analysis showed that the shrub canopy volume in the district Cempaka effect on changes in environmental factors. Besides the most dominant species is Ficus fistulosa Reinw. ex Bl with IVI of 56.1%. Based on the results obtained can be concluded that the shrub has potential as a constituent of vegetation in urban green space.

Legacies of forest harvesting on plant diversity and plant community composition in temperate deciduous forest

AbstractAimsTo conserve forest natural heritage, sustainable forest harvesting requires the recovery of plant diversity and ecosystem functions following management. There is a need to clarify the temporal dynamics of plant diversity following harvesting, for both even‐aged and uneven‐aged silvicultural systems. To achieve this goal, the temporal dynamics of plant diversity in the herb layer were measured in unmanaged forests (control) and along a chronosequence (&lt;5 years, 15 years and 30 years after harvesting) for even‐aged and uneven‐aged managed forests.LocationHardwood forest of southern Quebec, Canada.MethodsPlant diversity, plant community composition and ecosystem functioning were investigated using metrics exploring richness, evenness and disparity diversity components, and included two scales of diversity partitioning (alpha and beta). Shrub–canopy layer, forest tree species composition and structure, and total forest basal area were also measured.ResultsIn both uneven‐aged and even‐aged managed forest stands, we found: (a) a substantial decrease in mean plant phylogenetic diversity compared with unmanaged forest, even 30 years after harvesting (i.e., decrease of 16% and 22%, respectively); and (b) lowest plant alpha‐diversity in the herb layer 15 years after harvesting. Modification of community composition based upon dissimilarity (beta‐diversity) metrics demonstrated more numerous effects of even‐aged management than uneven‐aged management. For forest composition and structure, plant community and plant traits, dissimilarity relative to the unmanaged control was highest 5 years after even‐aged management. Trait‐based communities were more similar to unmanaged forest at the intermediate levels of forest density (i.e., ~20 m2/ha) that were found 5 years after uneven‐aged management.ConclusionsForest management clearly affected diversity, community composition and ecosystem functions along the chronosequence, highlighting the strongest effects of more intensive management (i.e., even‐aged) and the need to improve the sustainability of forest management.