Treeline Research Articles

Tree line shifts, changing vegetation assemblages and permafrost dynamics on Galdhøpiggen (Jotunheimen, Norway) over the past ~4400 years

An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late-Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species’ local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting a warmer climate suitable for Scots pine ( Pinus sylvestris) growth at this altitude. Scots pine retreated to lower altitudes between c. 3400 and 1700 cal. yr BP, accompanied by the descent of the low-alpine shrub-dominated belt, in response to cooling climatic conditions. The colder period covered c. 1700–170 cal. yr BP, and an open downy birch ( Betula pubescens) woodland became widespread at 1000 m a.s.l., whilst pine remained sparse at this altitude. From c. 170 cal. yr BP onwards, warming allowed pine to re-establish its local presence alongside downy birch at 1000 m a.s.l.

Soil water, nutrient distribution and use efficiencies under different water and fertilizer coupling in an apple–maize alley cropping system in the Loess Plateau, China

Soil water and nutrients are the main factors that restrict the stable development of alley cropping systems in the Loess Plateau of west Shanxi, China. Field experiments were conducted during 2014–2016 to investigate the effects of water and fertilizer coupling regulation on soil water, nutrient distribution and their use efficiencies in a typical apple–maize alley cropping system in the area. There were three upper limits for irrigation according to appropriate ranges of soil moisture for apple and maize, 50% (W1), 65% (W2) and 85% (W3) of field capacity (Fc) for the 0–60 cm soil layer, coupled with three nitrogen/phosphorus/potassium compound fertilizer levels of F1 (289.0/118.0/118.0 kg∙ha−1), F2 (421.4/168.8/168.8 kg∙ha−1), and F3 (537.0/219.0/219.0 kg∙ha−1) and a CK (rain fed, no irrigation or fertilizer) as a control, making a total of 10 treatments. The results indicated that the horizontal and vertical soil water content (SWC) increased with distance from the tree row and with soil depth, respectively. The SWC near the maize belts was greater than near the tree line, and this was reversed with the increase of intercropping years. In the horizontal direction, the soil nutrient content (SNC) for each indicator increased with distance from the tree row, with the maximum value occurring at 2.5 m. In the vertical direction, SNC decreased with soil depth, with the maximum value at 0–20 cm. The 85% Fc combined with 70% empirical fertilizer application amount resulted in the maximum grain yield and partial factor productivity (PFP). Irrigation water use efficiency (IWUE) was highest for the F1 level. Multivariate and spatial analyses showed that a range of 50–65% Fc combined with 70% empirical fertilizer application was suitable for optimal irrigation and fertilization management of this alley cropping system considering the integrated benefits of maize yield, IWUE and PFP.

Decreased bee emergence along an elevation gradient: Implications for climate change revealed by a transplant experiment.

Bees experience differences in thermal tolerance based on their geographical range; however, there are virtually no studies that examine how overwintering temperatures may influence immature survival rates. Here, we conducted a transplant experiment along an elevation gradient to test for climate-change effects on immature overwinter survival using movement along elevational gradient for a community of 26 cavity-nesting bee species in the family Megachilidae along the San Francisco Peaks, Arizona elevational gradient. In each of three years, we placed nest blocks at three elevations, to be colonized by native Megachilidae. Colonized blocks were then (1) moved to lower (warmer) elevations; (2) moved to higher (cooler) elevations; or (3) left in their natal habitat (no change in temperature). Because Megachilidae occupy high elevations with colder temperatures more than any other family of bees, we predicted that emergence would decrease in nest blocks moved to lower elevations, but that we would find no differences in emergence when nest blocks were moved to higher elevations. We found three major results: (1) Bee species moved to lower (warmer) habitats exhibited a 30% decrease in emergence compared with species moved within their natal habitat. (2) Habitat generalists were more likely than habitat specialists to emerge when moved up or down in elevation regardless of their natal life zones. (3) At our highest elevation treatment, emergence increased when blocks were moved to higher elevations, indicating that at least some Megachilidae species can survive at colder temperatures. Our results suggest that direct effects of warming temperatures will have negative impacts on the overall survival of Megachilidae. Additionally, above the tree line, low availability of wood-nesting resources is a probable limiting factor on bees moving up in elevation.

Land Use Changes in the Alpine Tree Line Ecotone in the Hrubý Jeseník Mountains (Czech Republic)

Abstract Currently, we expected a altitudinal shift of forest vegetation upward under predicted climate changes impacts to European mountains ecosystems. In this context can be very interesting, that changes in alpine tree line ecotone in high European mountains were induced by human activities relatively often also in history. Probably one of the most important driver in land-use changes in high mountains was grazing, which significantly have influenced both mountain spruce forests and open alpine grasslands in central-Europe. This paper deals with historical changes of land-use in Hruby Jesenik Mountains (Czech Republic) during 19th and 20th centuries. Results revealed consequences of former grazing in mountain grasslands above alpine tree line ecotone in the frame of land-use analyses based on historical maps and other sources. These results, based on historical data, support our better understanding to current dynamic changes in European mountain landscapes.

An isotopic proxy for nitrogen redistribution from Alnus acuminata to wheat intercrop

SummaryDirect belowground nitrogen (N) transfer has often been reported where plants with contrasting nutrients acquisition strategies (N2-fixing and non-fixing) co-occur, and there is still a gap in the knowledge of the extent of this transfer in the top soil under the field conditions. However, assessment under field conditions is challenging. We hypothesized a practical application of the analysis of natural abundance of δ15N supplemented with an isotopic mixing model ‘IsoSource’ to understand the relative direct contribution of N2-fixing Alnus acuminata to wheat intercrop (non-fixing) N isotopic signatures. A field experiment was conducted in an andic soil of high lands in northern Rwanda to quantitatively determine the proportional contribution of nitrogen by Alnus acuminata to wheat vegetative tissue isotope signatures at different distances from the trees (1 m, 3 m, 5 m, and 7 m). The study involved the measurements and analyses of natural abundance of stable isotopes δ15N and isotopic mixing modeling by IsoSource. Leaf samples were collected from twigs of 10 years old Alnus acuminata grown on the terrace-risers, along with soil samples (0–20 cm) and wheat flag leaf samples across terrace at 1 m, 3 m, 5 m, and 7 m from trees for isotopic measurement. The chlorophyll content index of wheat flag leaf at the four points across terrace was estimated by means of SPAD meter 502. The δ15N proportional contribution by Alnus acuminata to wheat was obtained through IsoSource analysis. We noted a significant (p < 0·01) gradient in depletion of wheat δ15N signatures moving further away from the tree line of Alnus acuminata. The wheat at 1 m from the trees exhibited the δ15N values closer to that of the tree, while at 7 m, the crop δ15N signature was significantly different from that of the tree. An isotopic mixing model ‘IsoSource’ indicated that the tree N may have provided 33·6 ± 4·3 % of the wheat intercrop N at 1 m distance from the trees. Therefore, this study shows that the understanding of field-based crop N and nutrient transfer in agroforestry may be enhanced by analysis of the physiological basis of stable isotopes signatures.

Longer Growing Seasons Cause Hydrological Regime Shifts in Central European Forests

In this study, we present evidence for a hydrological regime shift in upland central European forests. Using a combination of long-term data, detailed field measurements and modelling, we show that there is a prolonged and persistent decline in annual runoff:precipitation ratios that is most likely linked to longer growing seasons. We performed a long term (1950–2018) water balance simulation for a Czech upland forest headwater catchment calibrated against measured streamflow and transpiration from deciduous and coniferous stands. Simulations were corroborated by long-term (1965–2018) borehole measurements and historical drought reports. A regime shift from positive to negative catchment water balances likely occurred in the early part of this century. Since 2007, annual runoff:precipitation ratios have been below the long-term average. Annual average temperatures have increased, but there have been no notable long term trends in precipitation. Since 1980, there has been a pronounced April warming, likely leading to earlier leaf out and higher annual transpiration, making water unavailable for runoff generation and/or soil moisture recharge. Our results suggest a regime shift due to second order effects of climate change where increased transpiration associated with a longer growing season leads to a shift from light to water limitation in central European forests. This will require new approaches to managing forests where water limitation has previously not been a problem.

Spatial Distribution of Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) in Rice.

Rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is a destructive insect pest of rice in the United States. The pruning of rice roots by L. oryzophilus larvae can cause up to 25% yield loss. Currently, insecticidal seed treatments are used in the Louisiana rice industry as a pre-emptive means of controlling this weevil species. Our objective was to gain a better understanding of the spatial distribution of L. oryzophilus in Louisiana rice fields. Thirteen untreated commercial rice fields in Louisiana were mapped using GPS software, and surveyed for L. oryzophilus larvae over two years (2017 and 2018). An ANOVA, spatial interpolation, hotspot analysis, and multiple linear regression were used to determine where populations of L. oryzophilus were concentrated and whether distributions of the pest were related to edge effects. The results showed that L. oryzophilus larvae are typically aggregated along the edges of rice fields, with populations decreasing toward the center of rice fields. Lissorhoptrus oryzophilus densities were 3.3- and 2.2- fold greater along field edges than in field centers in 2017 and 2018, respectively. Hotspot spatial analysis revealed 59% and 32% of low-density clusters occurred at or near field centers, respectively. Multiple linear regression revealed larval densities decline with increasing distance from overwintering sites and alternative habitats (such as tree lines and levees containing bunch grasses and other alternative noncrop plants). These results suggest potential for insecticidal seed treatments to be applied selectively within rice fields to control this pest.

Assessment of the relationship between soil properties in an old tree line and its relation to tree density and tree trunk circumference

Soil organic carbon (SOC) is known as a vital ecosystem service, resulting from interactions of ecological processes. It is important for its contributions to food production, mitigation, and adaptation to climate change. In this study, we investigated the relationship between tree density and tree trunk circumference with the soil chemical properties in the small tree line area located in Józsefmajor, Hungary. The interrelation between different chemical soil properties also was measured. For this purpose, samples were taken in 24 plots (6 m×13m) from 0–10 soil depths. Tree density and tree trunk circumference in each plot were measured. The Near-Infrared spectroscopy technique (Wavelength Range: 1300–2600nm MEMS (micro-electromechanical systems) technology) was used to estimate the chemical properties of the soil. Pearson and Spearman correlation analysis was applied to study the interrelationships between two multivariate data sets, tree density and trunk circumference were compared with soil properties. The results showed a significant relationship between some soil chemical parameters, especially between soil organic carbon (SOC) and total N and also the cation exchange capacity (CEC) with SOC and total N. Besides, this study shows that the plots containing more trees and with a higher trunk circumference provide higher SOC and total N concentrations. Trunk circumference has a slightly stronger correlation with these two soil properties compared to those of tree density.

Effect of mature spruce forest on canopy interception in subalpine conditions during three growing seasons

AbstractThe interception process in subalpine Norway spruce stands plays an important role in the distribution of throughfall. The natural mountain spruce forest where our measurements of throughfall and gross precipitation were carried out, is located on the tree line at an elevation of 1,420 m a.s.l. in the Western Tatra Mountains (Slovakia, Central Europe). This paper presents an evaluation of the interception process in a natural mature spruce stand during the growing season from May to October in 2018–2020. We also analyzed the daily precipitation events within each growing season and assigned to them individual synoptic types. The amount and distribution of precipitation during the growing season plays an important role in the precipitation-interception process, which confirming the evaluation of individual synoptic situations. During the monitored growing seasons, precipitation was normal (2018), sub-normal (2019) and above-normal (2020) in comparison with long-term precipitation (1988–2017). We recorded the highest precipitation in the normal and above-normal precipitation years during the north-eastern cyclonic synoptic situation (NEc). During these two periods, interception showed the lowest values in the dripping zone at the crown periphery, while in the precipitation sub-normal period (2019), the lowest interception was reached by the canopy gap. In the central crown zone near the stem, interception reached the highest value in each growing season. In the evaluated vegetation periods, interception reached values in the range of 19.6–24.1% of gross precipitation total in the canopy gap, 8.3–22.2% in the dripping zone at the crown periphery and 45.7–51.6% in the central crown zone near the stem. These regimes are expected to change in the Western Tatra Mts., as they have been affected by windstorms and insect outbreaks in recent decades. Under disturbance regimes, changes in interception as well as vegetation, at least for some period of time, are unavoidable.

Strong Interactive Effects of Warming and Insect Herbivory on Soil Carbon and Nitrogen Dynamics at Subarctic Tree Line

Warming will likely stimulate Arctic primary production, but also soil C and N mineralization, and it remains uncertain whether the Arctic will become a sink or a source for CO2. Increasing insect herbivory may also dampen the positive response of plant production and soil C input to warming. We conducted an open-air warming experiment with Subarctic field layer vegetation in North Finland to explore the effects of warming (+3°C) and reduced insect herbivory (67% reduction in leaf damage using an insecticide) on soil C and N dynamics. We found that plant root growth, soil C and N concentrations, microbial biomass C, microbial activity, and soil NH4+availability were increased by both warming and reduced herbivory when applied alone, but not when combined. Soil NO3–availability increased by warming only and in-situ soil respiration by reduced herbivory only. Our results suggest that increasing C input from vegetation under climate warming increases soil C concentration, but also stimulates soil C turnover. On the other hand, it appears that insect herbivores can significantly reduce plant growth. If their abundance increases with warming as predicted, they may curtail the positive effect of warming on soil C concentration. Moreover, our results suggest that temperature and herbivory effects on root growth and soil variables interact strongly, which probably arises from a combination of N demand increasing under lower herbivory and soil mineral N supply increasing under higher temperature. This may further complicate the effects of rising temperatures on Subarctic soil C dynamics.

14,500 years of vegetation and land use history in the upper continental montane zone at Lac de Champex (Valais, Switzerland)

Forests in the upper continental montane zone are important ecotones between lowland and subalpine forest ecosystems. A thorough understanding of the past vegetation dynamics at mid elevation is crucial to assess past and future altitudinal range shifts of tree species in response to climate change. Lake sediments from Lac de Champex (1,467 m a.s.l.), a small lake in the Canton Valais in the Central Swiss Alps were analysed to reconstruct the vegetation, land use and fire history for the last 14,500 years, using pollen, macrofossils, non-pollen palynomorphs and charcoal. The record indicates that the tree line had already reached the Champex area during the Allerød (14,000 cal bp) but dropped below the lake’s catchment during the Younger Dryas cooling (12,750–11,550 cal bp). Reforestation started again with Betula and Pinus sylvestris in the Early Holocene at 11,500 cal bp in response to rapid climate warming. Temperate tree species (Ulmus, Tilia, Quercus, Acer) may have reached the altitude of the lake during the Holocene Thermal Maximum (ca. 10,000–5,000 cal bp). Mixed forests with mesophilous Abies alba were dominant between 7,500 and 5,000 cal bp. The mass expansions of Picea abies after 5,000 cal bp and Alnus viridis thickets after 4,500 cal bp were directly linked to increasing human disturbance. High values of coprophilous Sporormiella fungal spores and cereal pollen suggest pastoral and arable farming at the site from the Late Neolithic/Early Bronze Age onwards (5,000 cal bp). Our data imply that vegetation at intermediate elevation was less affected by human activities than at higher or lower elevations but that these areas served as important stations between the permanent settlements in the valleys and the seasonally occupied alpine huts at higher elevations. We argue that future climate warming will lead to drastic reorganizations of mountain ecosystems.

Current state of populations of Rhodiola rosea L. (Crassulaceae) in East Kazakhstan

BackgroundBased on world experience, first, a modern assessment of the flora is needed to develop strategies for the conservation of ecosystems of rare and endangered plant species. A regional and global biodiversity strategy should focus on assessing the current state of bioresources. To preserve the biodiversity of the species and its habitat, we evaluated botanical features, ontogenetic phases, the ecological and phytocenotic structure of the rare and endangered of Rhodiola rosea L. (golden rose root) populations from the highlands of Eastern Kazakhstan.ResultsR. rosea in the study region lives on damp mossy rocks, rocky slopes, overgrown moraines and along the banks of mountain rivers in the upper limit of cedar-larch forests, subalpine and alpine belts, in the altitude limit of 1700–2400 m. In the studied region, R. rosea begins to vegetate in May–June, blooms in June–July, the fruits ripen in August. The species is encountered in the high mountain ranges of the Kazakh Altai and Saur-Tarabagatai. Unfavorable habitat conditions for the species are overgrown by sedge-grass and birch-moss communities. The most common species at sites with R. rosea are: Schulzia crinita, Achillea ledebourii, Doronicum altaicum, Macropodium nivale, Hylotelephium telephium, Rhodiola algida, Carex capillaris, C. aterrima. Ontogenetic study revealed that all age-related phases were present, with the exception of the senile states. Individual life expectancy shown to be 50–55 years. The analysis of the species composition in the communities with R. rosea showed that the leading families in terms of the number of accompanying species are Poaceae, Ranunculaceae, Asteraceae, Rosaceae and Caryophyllaceae, Apiaceae, Fabaceae; while the most dominant genera are: Carex, Aconitum, Dracocephalum, Festuca, Pedicularis, Poa, Salix; the ecological groups are dominated by psychrophytes, mesophytes mesopsychrophytes; the Asian, Eurasian, and Holarctic groups are the most represented groups. Dominant life forms according to Serebyakov were rod-rooted, brush-rooted, short-rooted and long-rooted grasses, while based on Raunkiaer’s groups the overwhelming majority consisted of Hemincryptophytes (74%).ConclusionsThe R. rosea populations of Kazakhstan represent an important gene stock of the species. Our study provides new insights into the species’ biology thus contributes to the conservation of biodiversity on a wide spatial scale.

High Leaf Respiration Rates May Limit the Success of White Spruce Saplings Growing in the Kampfzone at the Arctic Treeline.

Arctic Treeline is the transition from the boreal forest to the treeless tundra and may be determined by growing season temperatures. The physiological mechanisms involved in determining the relationship between the physical and biological environment and the location of treeline are not fully understood. In Northern Alaska, we studied the relationship between temperature and leaf respiration in 36 white spruce (Picea glauca) trees, sampling both the upper and lower canopy, to test two research hypotheses. The first hypothesis is that upper canopy leaves, which are more directly coupled to the atmosphere, will experience more challenging environmental conditions and thus have higher respiration rates to facilitate metabolic function. The second hypothesis is that saplings [stems that are 5–10cm DBH (diameter at breast height)] will have higher respiration rates than trees (stems ≥10cm DBH) since saplings represent the transition from seedlings growing in the more favorable aerodynamic boundary layer, to trees which are fully coupled to the atmosphere but of sufficient size to persist. Respiration did not change with canopy position, however respiration at 25°C was 42% higher in saplings compared to trees (3.43±0.19 vs. 2.41±0.14μmolm−2 s−1). Furthermore, there were significant differences in the temperature response of respiration, and seedlings reached their maximum respiration rates at 59°C, more than two degrees higher than trees. Our results demonstrate that the respiratory characteristics of white spruce saplings at treeline impose a significant carbon cost that may contribute to their lack of perseverance beyond treeline. In the absence of thermal acclimation, the rate of leaf respiration could increase by 57% by the end of the century, posing further challenges to the ecology of this massive ecotone.

Green Areas in the City as an Element of Noise Protection

From the dawn of history, humanity created communication routes in order to move efficiently. Trees were planted along the roads connecting towns and villages so that travellers could rest in their shade. The line of trees also played an informative, strategic and sometimes aesthetic role. Currently, a line of tall vegetation along the street provides shade and relief in cities during hot weather. It is also worth emphasizing that greenery reduces stress factors in large cities. One of the stressors in cities is noise. In an urbanized environment, noise is perceived as unpleasant and bothersome. Appropriate planting of greenery in the city can reduce this phenomenon. The article not only analyses the possibilities of reducing noise through appropriate planting of greenery, but also provides guidelines for the correct design of greenery along streets and at crossroads. It is worth emphasizing here that the correct design of greenery in the vicinity of communication arteries is not only a matter of ethics or landscape legibility, but also a matter of safe use of infrastructure. The article also deals with the issue of legal acts relating to the design of urban greenery. The former and current legal acts contain provisions related to the classification of green areas, their protection and shaping. These regulations apply to various fields (construction, spatial planning, environmental protection) and therefore there are discrepancies in the legal interpretation of this term. All these doubts will be clarified.

Constraints on the temperature-density relation of the intergalactic medium with non-negligible absorber spatial structure

We investigate evolution of physical parameters of the intergalactic medium using an analysis of Lya forest lines detected towards distant quasars. We used the enlarged sample of 98 quasars obtained with Keck/HIRES and VLT/UVES. We show that taking into account a finite spatial size of absorbers, regulated by pressure smoothing, significantly affects the inferred thermal parameters of the intergalactic gas, such as the hydrogen photoionization rate and parameters of the temperature-density relation. Using Bayesian framework we constrained for the first time the scale parameter between the Jeans length and characteristic size of the absorbers. We also discuss limitations of the method based on the analysis of the minimal broadending of Lya lines, which stem from the patchy nature of He II reionization.

La calle proyectada en el planeamiento urbanístico reciente. Murcia, 2001-2016

The 'prodigious decade' of Spanish urbanism caused a large expansion of urban lands, but also a much greater amount of planned but undeveloped land. The planning for this 'expectant city' is a challenge for the future of our cities. In this work, the streets proposed in these plans are analysed by evaluating their dimensional characteristics (surface and width) and their habitability (pedestrian-cyclist space and previsions of tree lines). The research is focused on the city of Murcia, paradigmatic case of the expansive urbanism typical of the real estate bubble. We have studied 2,096 streets from 92 partial plans approved during the period 2002-2013. The results show how the analysed variables change according to the use and density of the sectors and can be useful to evaluate the improvement of the habitability of these streets before their execution.

Topography modulates effects of nitrogen deposition on microbial resource limitation in a nitrogen-saturated subtropical forest

BackgroundNitrogen (N) saturation theory proposes that an ecosystem might switch from N limitation to carbon (C), phosphorus (P), or other nutrient limitations if it receives continuous N input. Yet, after N limitation is removed, which nutrient is the most limited and whether topography modulates such change is rarely tested at a microbial level. Here, we conducted a two-year N addition experiment under two different topography positions (i.e. a slope and a valley) in a N-saturated subtropical forest. Soil enzyme activity was measured, and ecoenzymatic stoichiometry indexes were calculated as indicators of microbial resource limitation.ResultsIn the valley, two-year N addition changed the activity of all studied enzymes to various degrees. As a result, microbial C limitation was aggravated in the valley, and consequently microbial decomposition of soil labile organic C increased, but microbial P limitation was alleviated due to the stoichiometry balance. On the slope, however, N addition did not significantly change the activity of the studied enzymes, and did not alter the status of microbial resource limitation.ConclusionsThese results indicate that C is a more limited element for microbial growth than P after removing N limitation, but we also highlight that topography can regulate the effect of N deposition on soil microbial resource limitation in subtropical forests. These findings provide useful supplements to the N saturation theory.

Population ecology and habitat suitability modelling of Betula utilis D. Don in the sub-alpine ecosystem of Great Himalayan National Park, North-Western Indian Himalaya: a UNESCO World Heritage site

Betula utilis is a native tree and important tree line species in the Indian Himalayan Region (IHR). Due to various natural and anthropogenic factors, the population of the species has become dwindling. Therefore, study was conducted to; assess population, regeneration, habitat suitability model, size class distribution and physico-chemical properties of the soil in sub-alpine ecosystem of Great Himalayan National Park. Total 64 populations assessed to determine the density, Total Basal Area, Species diversity index, Concentration of dominance and regeneration pattern of seedlings and saplings. Amongst the identified populations, total trees density ranged from 10–730 Ind ha−1; total basal area 0.00–43.32 m2 ha−1; total shrubs density 340–3490 Ind ha−1; total herbs density 8.54–152.77 Ind m−2; total saplings density 9–3050 Ind ha−1 and total seedlings density 10–1840 Ind ha−1. Species diversity of trees was ranged from 0.00 to 0.37; Concentration of dominance ranged from 0.00 to 1.00. Size class distribution revealed that maximum number of individuals was fallen in the range of 52.6–73.5 cm whereas lowest numbers of individuals were fallen in the range of 136.6–157.5 cm and ≥ 220.6 cm. The model calibration test for B.utilis yielded satisfactory results (AUC Mean = 0.91 ± 0.02) indicated that MaxEnt could be used to predict the potentially suitable habitats for in-situ or ex-situ conservation. The model predicted 268 km2 area suitable for reintroduction. Frequent monitoring of populations for understanding the dynamics and identifying natural habitats for the in-situ conservation of the species are suggested.

The Mangrove Forests of the Cameroon Coast and its Socio-Economic Significan


 
 
 The study analyses anthropogenic influence on the mangrove forests of the Cameroon coast and focuses on the development and improvement of the constructive- geographical foundations of rational nature management for the conservation and possible renewal of its natural resources base. The exploitation of mangrove forest landscapes has yielded significant benefits to the local population living within the mangrove forest limits, but the beneficiaries have not made commensurate investments in their sustainability and rational use. Therefore, this habitat must be carefully conserved or protected from wanton anthropogenic activities for the development purpose. The study made use primary and secondary data in establishing the facts analysed in this work. The secondary data comprised of materials of prominent authors who have contributed much to the findings related to coastal mangroves. Primary data collection was field visits carried out by the author in 2016. Questionnaires and semi- structural questions were used to collect information from mangrove exploiters. The findings confirm that the coastal mangrove forests in Cameroon have multiple functions beneficial to the communities adjacent to the coast, but, unfortunately, the beneficiaries have not made commensurate efforts to their sustainability and rationale. The Mangrove forests covered a surface area of 200 000 km2, but Cameroon lost 30 % of its mangrove forest cover in 1980–2006. If projected under ceteris paribus, Cameroon lost approximately 45 % of its mangrove forest cover in1980–2020. Haven understood that man has raped huge surfaces of mangrove forest for his selfish economic gains, the study proposed an urgent need for environmentally sustainable adaptive strategies like those earmarked in the Ramsay agreement and the ICZM (Integrated Coastal Zone Management) for the rational management of coastal mangroves in Cameroon.
 
 

Drying conditions in Switzerland – indication from a 35-year Landsat time-series analysis of vegetation water content estimates to support SDGs

ABSTRACT Exacerbated by climate change, Europe has experienced series of hot and dry summer since the beginning of the 21st century. The importance of land conditions became an international concern with a dedicated sustainable development goal (SDG), the SDG 15. It calls for developing and finding innovative solutions to follow and evaluate impacts of changing land conditions induced by various driving forces. In Switzerland, drought risk will significantly increase in the coming decades with severe consequences on agriculture, energy production and vegetation. In this paper, we used a 35-year satellite-derived annual and seasonal times-series of normalized difference water index (NDWI) to follow vegetation water content evolution at different spatial and temporal scales across Switzerland and related them to temperature and precipitation to investigate possible responses of changing climatic conditions. Results indicate that there is a small and slow drying tendency at the country scale with a NDWI mean decreasing slope of −0.22%/year for the 23% significant pixels across Switzerland. This tendency is mostly visible below 2000 m above sea level (m.a.s.l.) and in all biogeographical regions. The Southern Alps regions appear to be more responsive to changing drying conditions with a significant and slight negative NDWI trend (−0.39%/year) over the last 35 years. Moreover, NDWI values are mostly a function of temperature at elevations below the tree line rather than precipitation. Findings suggest that multi-annual and seasonal NDWI can be a valuable indicator to monitor vegetation water content at different scales, but other components such as land cover type and evapotranspiration should be considered to better characterize NDWI variability. Satellite Earth Observations data can provide valuable complementary observations for national statistics on the ecological state of vegetation to support SDG 15 to monitor land affected by drying conditions.