Island Vegetation Research Articles

Corrigendum to Pristinity, degradation and replacement: the three dimensions of human impact on island vegetation

Corrigendum to Pristinity, degradation and replacement: the three dimensions of human impact on island vegetation

High C-and N-based soil fertility and microbial associations sustain the plant biodiversity of the campo rupestre in Brazil

The campo rupestre vegetation in the Serra do Rola Moça State Park (PESRM) grows on ironstone outcrops, forming vegetation islands where plant species establish belowground interactions. This area is circumscribed by several mining companies and, for mined land rehabilitation purpose, we assessed plant species composition, plat-microbial associations, and soil fertility patterns in a preserved campo rupestre. Aside from high plant biodiversity, we found elevated soil fertility in relation to soil CEC (~18 cmol/dm3), organic matter (~115 g/Kg), soil C (~ 53.3 g/Kg), humic (~12.5 g/Kg) and fulvic (~8.9 g/Kg) acids, soil N (~4 g/kg) and a low C:N ratio (~12). The overall nutrient levels were higher than or comparable to those of other preserved sites in Brazil. The prevalent legume Mimosa calodendron, hosting N-fixing and plant growth-promoting bacteria in its nodules, was considered an N source to the soil, as evidenced by the elevated leaf N content and the greater depletion of leaf δ15N compared to other families. However, leaf N was parsimoniously distributed among biogeochemical islands and within different plant species and families, which was attributed to a common mycorrhizal network (CMN) formed by arbuscular (AMF) and orchid mycorrhizal fungi (OMF), suggested by general root mycorrhizal colonisation and soil phospholipid fatty acid (PLFA) analyses. We revealed that a high C- and N-based soil fertility constitutes a natural pattern of fertility, which is maintained by below-ground associations and is sufficient to sustain plant biodiversity. For rehabilitation purposes, this natural soil fertility of preserved sites should be maintained by integrating the biogeochemical relations involving plant communities and microbial associations.

Nest site selection of White-tailed Hawks (Geranoaetus albicaudatus) on Texas barrier islands

The distribution of the White-tailed Hawk (Geranoaetus albicaudatus) in the United States is restricted to the prairies and savannas of the Gulf Coastal Plain of Texas. Although listed as a state threatened species, it remains one of the least studied raptors in North America. It appears to reach high densities on some Texas barrier islands despite the island vegetation communities being structurally simple and providing few nesting substrates. We compared vegetation and landscape characteristics for sets of White-tailed Hawk nest sites and random sites on 3 Texas barrier islands (Matagorda, Mustang, and North Padre) representing a gradient of low to high human presence and impact. We constructed model sets consisting of vegetation and landscape features measured at a random subsample of nest sites and random sites, then assessed model sets with logistic regression. Our best constructed model correctly differentiated 83% of nest sites from random sites on Matagorda Island, 70% on Mustang Island, and 50% on North Padre Island. Overall, it appears that the structure of nest substrates was important to White-tailed Hawk nest-site selection: shrubs categorized as densely structured with or without thorns accounted for 78% of nest substrates compared to only 13% of paired, random potential substrates. The most frequently selected nest substrates overall were yaupon (Ilex vomitoria; 43%) and Macartney rose (Rosa bracteata; 24%). If White-tailed Hawks are to be conserved on the barrier islands, a balance will need to be found between continued anthropogenic development, maintenance of habitat patches, and availability of suitable nesting substrates.

Vicu�a Poop Nourishes “Dung Gardens” High in the Andes

The excrement delivers nutrients like phosphorus and nitrogen, kick-starting islands of vegetation at the edge of the cryosphere.

Spatiotemporal Characteristics of Vegetation Net Primary Productivity on an Intensively-Used Estuarine Alluvial Island

Net Primary Productivity (NPP) can effectively reflect the characteristics and strength of the response to external disturbances on estuarine alluvial island ecosystems, which can provide evidence for regulating human development and utilization activities and improving blue carbon capacity. However, there are a few studies on NPP of estuarine alluvial islands. We established a model based on a Carnegie–Ames–Stanford Approach (CASA) to estimate NPP on Chongming Island, a typical estuarine alluvial island, by considering the actual ecological characteristics of the island. The NPP of different land-cover types and protected areas in different years and seasons were estimated using Remote Sensing and Geographic Information System as the main tools. Correlations between NPP and Remote Sensing-based spatially heterogeneous factors were then conducted. In the last 30 years, the mean NPP of Chongming Island initially increased and then slowly decreased, while total NPP gradually increased. In 2016–2017, Chongming Island total NPP was 422.32 Gg C·a−1, and mean NPP was 287.84 g C·m−2·a−1, showing significant seasonal differences. NPP showed obvious spatial differentiation in both land-cover and protected area types, resulting from joint influences of natural and human activities. Chongming Island vegetation growth status and cover were the main factors that positively affected NPP. Soil surface humidity increased NPP, while soil salinity, surface temperature, and surface aridity were important NPP limiting factors.

Spatiotemporal dynamics of urban climate during the wet-dry season transition in a tropical African city

The Urban Heat Island effect has been the focus of several studies concerned with the effects of urbanisation on human and ecosystem health. Humidity, however, remains much less studied, although it is useful for characterising human thermal comfort, the Urban Dryness Island effect and vegetation development. Furthermore, variability in microscale climate due to differences in land cover is increasingly crucial for understanding urbanisation effects on the health and wellbeing of living organisms. We used regression analysis to investigate the spatial and temporal dynamics of temperature, humidity and heat index in the tropical African city of Kampala, Uganda. We gathered data during the wet to dry season transition from 22 locations that represent the wide range of urban morphological differences in Kampala. Our analysis showed that the advancement of the dry season increased variability of climate in Kampala and that the most built-up locations experienced the most profound seasonal changes in climate. This work stresses the need to account for water availability and humidity to improve our understanding of human and ecosystem health in cities.

СТРАТИГРАФИЯ ВОДОРАЗДЕЛЬНОГО ТОРФЯНИКА И РАЗВИТИЕ ПРИРОДНОЙ СРЕДЫ ОСТРОВА БОЛЬШОЙ ШАНТАР В ПОЗДНЕЛЕДНИКОВЬЕ–ГОЛОЦЕНЕ

Continued record of paleogeographic events in the Shantar islands since the end of the Pleistocene was restored on the basis of a multy-proxy study of the stratigraphy of the blanket peatland. Biostratigraphical studies included botanical, diatom and pollen analyses. The age-depth model was built using 7 radiocarbon dates. For the first time, data of the environment development were obtained for the coldest part of the Sea of Okhotsk. Synchronicity and metachronicity of paleoclimatic events with regional data and global changes have been established. The Younger Dryas on the Shantar islands was much colder than in other areas around the Sea of Okhotsk. The climate became more maritime after the isolation of the islands at the early-middle Holocene. The influence of the cold sea and the presence of drifting ice were one of the main factors, why the early and middle Holocene optimums were poorly manifested here, and also determined the specifics of climatic rhythm. Models explaining alternation of relatively warm and cold periods with different humidity are proposed. The age of periods with heavy snowfalls has been established, as evidenced by the change in the role of shrub pine in island vegetation. Phases of development of local swamp and zonal landscapes are highlighted. Spruce appeared on the area ~11410–10345 cal. yr. BP, when there was a landbridge, and spruce trees became common in the middle Holocene and especially at the boundary of the middle-late Holocene. One of the controlling factors for the development of swamp landscapes was thermokarst processes. Significant changes in the environment occurred in the Little Ice Age, the most severe conditions were ~500–260 cal. yr. BP. In the last 210 years, the most significant changes in landscapes have been associated with anthropogenic fires.

Lagoon of Islands, Tasmania: Ecosystem response to dam wall removal

Lagoon of Islands was a rare wetland of high conservation value, supporting floating islands of vegetation before it was dammed to supply water for consumptive use downstream. After damming, water quality declined to such an extent that in 2013, the dam wall was removed and a wetland restoration project was commenced, resulting in immediate improvements in water quality and, within five years, regeneration of a plant community largely composed of dominant species of the original wetland.

Spatiotemporal Evolution Characteristics of Ecosystem Service Values Based on NDVI Changes in Island Cities

Vegetation plays a dominant role in and serves as the structural foundation of island-land ecosystems. Island cities, as sea-land ecological complexes, are able to somewhat reflect the general realities of island ecological environments. By using the Landsat series remote-sensing images and an ecosystem service value (ESV) evaluation system, in this paper, the temporal and spatial evolution characteristics of the NDVIs and ESVs of China’s 12 island counties over the past three decades are analyzed. According to the research results, (1) The average NDVI of China’s island counties dropped from 0.380 to 0.347 in 1990-2018, reflecting a continuous downtrend. The NDVIs of Changhai County and Changdao County show significant changes, with decreases of 45.24% and 37.57%, respectively. (2) The total ESV of China’s island counties showed a “V”-shaped change trend from 1990-2018; the minimum value reached USD 362 million in 2010, then essentially recovered to the 2000 level in 2018. (3) The high and low values of NDVI and ESV in island counties over the years were distributed with the spatial characteristics of high values in the center of the islands and low values at the edges of the islands. The island counties north of the Yangtze River showed the largest changes in NDVI and ESV. (4) Forest cover is the main factor that drives ESV reduction in China’s island counties, followed by grassland cover. This study provides an effective method to study the changes in the NDVI and ESV of island cities and proposes the strengthening of island vegetation protection and the promotion of sustainable development in the ecological environments and economies of island cities.

Horticultural species of the island of Lokrum in the period of archduke Maximilian of Habsburg (1859–1869) and their current state

This research, conducted within the ornamental gardens of the Island of Lokrum and based on the original archival documents from Trieste State Archives (AST) and Austrian State Archives (OeStA) in Vienna, was aimed at creating the first unique list of horticultural plant taxon planted on the island during the reign of the Archduke Ferdinand Maximilian Habsburg (1859-69). The research identified 213 taxa, including 184 species, 4 varieties, 8 hybrids and 17 cultivars. There were 193 allochthonous taxa, mostly originating from Central and South America (66), including 47 Asian species, 21 Australian species, 17 African species and 13 South American species. The Archive lists 20 taxa autochthonous in Croatia. While the number of the autochthonous taxa had apparently been higher, the historical documents have mostly recorded only the introduction of exotics. At that time, the following taxa were for the first time introduced in this part of the Adriatic, on the Island of Lokrum: Ananas comosus, Musa x paradisiaca, M. acuminata, Eucalyptus diversifolia, E. globulus, Araucaria araucana, A. columnaris, A. angustifolia, A. bidwillii, A. cunninghamii, Bougainvillea spectabilis and Citrus reticulata. At the location of the ornamental gardens, 51 ornamental allochthonous taxa and 20 autochthonous taxa were identified today. Within this number, only 21 allochthonous taxa and 9 autochthonous taxa remain present since the period of Maximilian. According to the 2018-2019 inventory, 71 taxa have been inventoried within the ornamental gardens on Lokrum, belonging to 43 families and 64 genera. Due to lack of intensive maintenance of the gardens, the majority of allochthonous, exotic species failed to survive within the autochthonous island vegetation. The list of taxa from Maximilian’s gardens presented in this paper and retrieved from the archival sources, will be the starting point of the restoration process that awaits these gardens.

Observations on different post-fire bio-engineering interventions and vegetation response in a Pinus canariensis C. Sm. forest

On the Canary Islands, during the 2007 (30 July - 2 August) wildfire, about 18.000 hectares of forest were destroyed. After the event, to avoid erosion, a series of mixed check dams (wooden elements and stones with a core filled with forest residues) were built in the gullies created by the surface runoff. This first study aims to investigate the different responses of vegetation and its recovery after fire, with three different types of structures. We analyzed the performance and evolution of the mixed check dams nine years after their construction and the post-fire response of vegetation with the different types of bio-engineering techniques applied. The effects of the mixed check dams are expressed in terms of plant density, frequency, and cover both in absolute and in relative terms and the same effects were compared with those of the rocks, check dams, wattle fences, and structure in the surrounding areas. Our observations show that fire adaptation in the Canary Islands vegetation (pyrophyte plants), coupled with selected bio-engineering techniques, facilitated resprouting, seeds germination and a quick restoration of the forest ecosystem. The study confirms that simple, nature-based and low cost bio-engineering measures, which use local materials and are consistent with traditional building experiences effectively contribute to site restoration.

Pristinity, degradation and replacement: The three dimensions of human impact on island vegetation

This paper presents three extreme examples of the potential consequences of human settlement on the vegetation of oceanic and continental islands. The Neotropical Pantepui continental archipelago of sky islands is an example of pristinity, due to the almost nonexistent human impact that results from the remoteness and inaccessibility of these islands as well as the lack of natural resources to exploit. Easter Island is used to illustrate total vegetation degradation by deforestation and the exhaustion of natural resources, which has transformed the island into badlands with no signs of recovery. The Azores Islands have been chosen to illustrate replacement as, after initial postsettlement deforestation and extractive practices, a further transformative phase consisting of creating an almost totally anthropogenic vegetation with mostly exotic species occurred. The paper describes in some detail the developments of each case and the historical context in which they took place using historical, archeological and paleoecological evidence. Many intermediate states are possible among these three extremes, which can be represented with a ternary diagram (the PDR diagram), which is useful for characterizing the state of each island or archipelago in terms of human impact on terrestrial ecosystems and informing conservation and restoration practices.

How lime-sand islands in the South China Sea have responded to global warming over the last 30 years: Evidence from satellite remote sensing images

As global warming threatens their existence, there are widespread concerns regarding the persistence of lime-sand islands and the future of mid-ocean atoll nations. To investigate how climate change has affected lime-sand islands, changes in vegetation and other characteristics of such islands in the South China Sea (SCS) were investigated from 1989 to 2019 using 67 satellite images. First, boundaries of the lime-sand islands and their vegetation were extracted using an active contour extraction procedure called the gradient vector flow snake model. Afterwards, the spatial extents were estimated by enclosing the extracted boundaries, and the digital shoreline analysis system was used to calculate beach widths. Finally, area growth rates and speeds were used to evaluate areal changes in the lime-sand islands and their respective vegetation. Based on the estimated area growth rates, area growth speeds, and beach widths, the lime-sand islands in SCS eroded over the past three decades whereas their vegetation expanded. Further analysis suggested that direct inundation caused by sea-level rise might not be clearly identified from the satellite images. However, other climate change-related factors were most likely responsible for the observed island erosions. These factors included higher wave energy, stronger typhoon intensity and destructiveness, and accelerated coral reef degradation. In addition, the observed expansion of vegetation on the lime-sand islands was likely due to the increase in precipitation in a warming world. The results show that 1) the lime-sand islands will continue to erode whereas vegetation will continue to expand; 2) As vegetation growth is significantly inhibited by salt water when it is adjacent to the ocean, vegetation areas on lime-sand islands may start to continuously decline. Overall, this study is the first to quantitatively examine changes in SCS lime-sand islands due to global warming.

New records of ectoparasites for Mexico and their prevalence in the montane shrew Sorex monticolus (Eulipotyphla: Soricidae) at Cerro del Mohinora, Sierra Madre Occidental of Chihuahua, Mexico.

The Flora and Fauna Protection Area (Área de Protección de Flora y Fauna-ÁPFF) Cerro del Mohinora, is the highest mountain in northern Mexico, reaching an elevation of 3,300 meters. It constitutes one of the last high-elevation islands of alpine and subalpine vegetation known in the Sierra Madre Occidental, in the extreme southwestern part of Chihuahua. The ÁPFF Cerro del Mohinora is located near the state border and limits with Durango and Sinaloa. This type of ecosystem located at high altitudes is in danger of disappearing since only 1% or less of its original extension remains; it is considered a refuge for species with boreal affinities (McDonald et al. 2011).

Do Bottom-up Effects Define The Structuring Of Ant (Hymenoptera: Formicidae) Communities In A Restinga Remnant?

Restingas are lowland sandy ecosystems located between mountain ranges and the sea. For living organisms in this ecosystem, restingas can be seen as habitats formed by islands of vegetation separated by a sandy matrix. These organisms are highly influenced by the environmental conditions and physical characteristics of the landscape, including size, connectivity and environmental heterogeneity. Given the recognized effectiveness of ants as bioindicators, this study uses these organisms as a model to assess how vegetation complexity affects ant communities. The study was carried out in the Parque das Dunas, Salvador - Bahia. Within this park, four categories of vegetation islands (Small, Medium, Large and Continuous) were delimited, where the ant fauna was sampled and the forms of vegetal life were analyzed, using the Raunkiaer analysis. A total of 69 ant species were collected from 31 genera and six subfamilies. We found a positive relationship between the diversity of plant life forms (H') and ant richness. In general, there was a significant difference in the composition of ant species in each microhabitat and between the areas of continuous vegetation and the different vegetation islands. There is a bottom up effect mediating the ant community associated with dune vegetation, the local richness of ant species responds to vegetation heterogeneity.

Sugarloaf Land in south-eastern Brazil: a tropical hotspot of lowland inselberg plant diversity

BackgroundIsolated monoliths of granitic and/or gneissic rock rising abruptly from the surrounding landscape are known as inselbergs. Dome-shaped inselbergs are common throughout the Atlantic Forest in south-eastern Brazil, a region known as Sugarloaf Land (SLL). This study aimed to create the first checklist of vascular plant species occurring on lowland inselbergs in SLL, with a focus on vegetation islands. We used information from online databases, our own field sampling and data from previously-published studies. We found 548 vascular plant species (505 angiosperms; 43 ferns and lycophytes) belonging to 69 families and 212 genera. Of all identified species, 536 are native and 12 are naturalised.New informationWe updated the information currently available in Flora do Brasil 2020, as 59% of the angiosperms and 63% of the ferns and lycophytes on our checklist were not previously characterised as occurring on rock outcrops. As a first step towards generating a Virtual Herbarium of lowland inselberg vascular plants, we added barcode vouchers with images available online for 75% of the total number of vascular species. In the official lists of endangered species, 115 angiosperms and five ferns and lycophytes are mentioned. However, the conservation status of many species have not yet been evaluated (77% angiosperms; 88% ferns and lycophytes), thus this list is an important step towards their conservation. The information provided herein is essential for management programmes related to rock outcrops in Brazil as they are facing serious threats to conservation.

Population dynamics of Hippophae rhamnoides shrub in response of sea-level rise and insect outbreaks.

The coastal vegetation of islands is expected to be affected by future sea-level rise and other anthropogenic impacts. The biodiverse coastal vegetation on the eastern part of the Dutch Wadden Island of Ameland has experienced land subsidence caused by gas extraction since 1986. This subsidence mimics future sea-level rising through increased flooding and raising groundwater levels. We studied the effects of this relative sea-level rise and other environmental factors (i.e. insect outbreaks, temperature and precipitation) on the population dynamics (i.e. cover and age structure and annual growth) of the shrub sea-buckthorn (Hippophae rhamnoides L.) in young (formed after 1950) and old (formed before 1950) dune areas over a period of 56 years (1959–2015). We found an increase in sea-buckthorn cover in the young dune areas since 1959, while over time the population in the old dunes decreased due to successional replacement by other species. With the increasing age of the young dunes, we found also a decrease in sea-buckthorn after 2009. However the sharp decrease indicated that other environmental factors were also involved. The most important determinant of annual shrub growth appeared to be five outbreaks of the brown-tail moth (Euproctis chrysorrhoea L.), in the last decade. Relative sea-level rise caused more frequent flooding and reduced growth at lower elevations due to inundation or soil water saturation. This study clearly indicates that sea-buckthorn is affected by relative sea-level rise, but that other ecological events better explain its variation in growth. Although shrub distribution and growth can be monitored with robust methods, future predictions of vegetation dynamics are complicated by unpredictable extreme events caused by (a)biotic stressors such as insect outbreaks.

Late Quaternary vegetation and climate dynamics in central‐eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome

ABSTRACTThe late Quaternary evolution of central‐eastern Brazil has been under‐researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi‐deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi‐proxy approach: stable isotopes (δ13C, δ15N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid‐Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp) and over (~16.5 to ~6.1 k cal a bp) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp.

Evaluating techniques for mapping island vegetation from unmanned aerial vehicle (UAV) images: Pixel classification, visual interpretation and machine learning approaches

We evaluate three approaches to mapping vegetation using images collected by an unmanned aerial vehicle (UAV) to monitor rehabilitation activities in the Five Islands Nature Reserve, Wollongong (Australia). Between April 2017 and July 2018, four aerial surveys of Big Island were undertaken to map changes to island vegetation following helicopter herbicide sprays to eradicate weeds, including the creeper Coastal Morning Glory (Ipomoea cairica) and Kikuyu Grass (Cenchrus clandestinus). The spraying was followed by a large scale planting campaign to introduce native plants, such as tussocks of Spiny-headed Mat-rush (Lomandra longifolia). Three approaches to mapping vegetation were evaluated, including: (i) a pixel-based image classification algorithm applied to the composite spectral wavebands of the images collected, (ii) manual digitisation of vegetation directly from images based on visual interpretation, and (iii) the application of a machine learning algorithm, LeNet, based on a deep learning convolutional neural network (CNN) for detecting planted Lomandra tussocks. The uncertainty of each approach was assessed via comparison against an independently collected field dataset. Each of the vegetation mapping approaches had a comparable accuracy; for a selected weed management and planting area, the overall accuracies were 82 %, 91 % and 85 % respectively for the pixel based image classification, the visual interpretation / digitisation and the CNN machine learning algorithm. At the scale of the whole island, statistically significant differences in the performance of the three approaches to mapping Lomandra plants were detected via ANOVA. The manual digitisation took a longer time to perform than others. The three approaches resulted in markedly different vegetation maps characterised by different digital data formats, which offered fundamentally different types of information on vegetation character. We draw attention to the need to consider how different digital map products will be used for vegetation management (e.g. monitoring the health individual species or a broader profile of the community). Where individual plants are to be monitored over time, a feature-based approach that represents plants as vector points is appropriate. The CNN approach emerged as a promising technique in this regard as it leveraged spatial information from the UAV images within the architecture of the learning framework by enforcing a local connectivity pattern between neurons of adjacent layers to incorporate the spatial relationships between features that comprised the shape of the Lomandra tussocks detected.

Discussion on Sampling Methods in Island Vegetation Survey of Species Richness and Biomass

Vegetation is an important part of island ecosystem. Due to the distinction of vegetation from mainland vegetation, the existing mainland sampling method cannot be entirely applied to the islands. Hence it is necessary to combine the existing mainland vegetation sampling methods, and to select different types of islands to test the key links of the methods, and to accumulate data for statistical analysis, so as to obtain the technical methods suitable for island vegetation sampling. Aiming at the application of quadrat method in island vegetation survey, this paper chooses two different survey areas of North Changshan Island as examples, compares different quadrat setting methods, clarifies how to set the quadrat in different kind of slope direction, slope position, and types of plant communities, how much the number of quadrat, and how much the area of quadrat can be set in order to represent the island more completely. Finally, the optimal principle of setting up the island quadrat is determined, which provides scientific basis for the effective selection of the quadrat setting in the investigation of island vegetation community.