Reduced Vegetation Cover Research Articles

The Impacts of the Dust Radiative Effect on Vegetation Growth in the Sahel

AbstractMany studies have been conducted on the effects of dust on rainfall in the Sahel and generally show that African dust weakens the West African Monsoon, drying the region. This drying is often assumed to produce a positive dust‐precipitation feedback by reducing vegetation cover for the region. We directly test this relationship for the first time by using a model that explicitly simulates vegetation growth and its impact on dust emission. There are several competing effects of dust that affect plant growth: changes to rainfall, downwelling solar radiation, surface temperature, and resultant changes in surface fluxes. Our model finds that the combined effect of these processes decreases vegetation cover and productivity of the Sahel and West Africa. We determine this by comparing experiments with radiatively active dust to experiments with radiatively invisible dust. In modern conditions, the dust radiative effect decreases leaf area by 12%, productivity by 14%, and increases bare soil area by 3% across the Sahel, and by much higher amounts locally. Experiments where the vegetation experiences preindustrial rather than modern CO2 levels show that without stomatal closure, the reductions would be approximately 20–40% stronger. In preindustrial conditions the vegetation response is weaker, despite the dust‐induced rainfall and temperature anomalies being similar. We interpret this as the vegetation being less susceptible to drought in a less evaporative climate. These vegetation responses to dust are evidence of a dust‐vegetation feedback loop whose strength varies with the mean state of the climate and which may grow stronger in the future.

Chronostratigraphy, depositional patterns and climatic imprints in Lake Acigöl (SW Anatolia) during the Quaternary

A 601 m long sedimentary sequence was drilled in Lake Acigol, located in the lakes region of SW Anatolia, near the Denizli travertine from which the oldest hominin of Turkey was unearthed. Among all dating methods applied to the sedimentary sequence, paleomagnetism, through the recognition of geomagnetic chrons, was the most successful and led to a quasi linear age model, with the 601 m long sedimentary record covering the last 2.3 Ma. An attempt to use the atmospherically deposited 10 Be as a dating method was not very successful but provides interesting clues on this new method. Long-term lake level changes are depicted through lithological variations, in particular the carbonates and evaporites abundance. This change could be influenced by both long term cooling during the last 2 Ma and tectonic activity, which may in particular be responsible for a maximum water depth at around 1.8 Ma. Despite active tectonic influence, the sedimentary facies description and the magnetic susceptibility record (cleaned from tephra intervals) show that climate fluctuations (i.e., glacial-interglacial alternations) are likely recorded in the sedimentary succession, with warm periods marked by enhanced carbonate precipitation and cold and dry periods characterized by more detrital input linked to reduced vegetation cover and consequently more erosion in the catchment area. Preliminary pollen data, used to interpret magnetic susceptibility fluctuations, show that an average dry and open landscape prevailed around Acigol lake during the whole record.

Spatio-temporal pattern of soil degradation in a Swiss Alpine grassland catchment

Soil degradation on Alpine grasslands is triggered mainly by extreme topography, prevailing climate conditions and land use practices. Suitable monitoring tools are required to assess soil erosion with high temporal and spatial resolution. In this study, we present an unprecedented and comprehensive approach based on object-based image analysis (OBIA) to map and assess all occurring erosion processes within a catchment (Urseren Valley, Switzerland). Five high-resolution (0.25−0.5m) orthophotos with RGB spectral information (SwissImage) produced during a 16-yr period were analyzed. Soil erosion sites are classified according to their type (shallow landslide or sites with reduced vegetation cover affected by sheet erosion) or the triggering land use management impacts (haying, trampling) with the Overall Accuracy ranging between 78 and 88% (Kappa 0.65–0.81) for the different years. The area affected by soil erosion increases for all classes during the study period (2000–2016) by a total of 156 ± 18% (increase consisting of 3% shallow landslides, 5% livestock trails, 46% sheet erosion and 46% management effects). Slopes at lower elevations (<1800masl) are increasingly affected by livestock trails and sheet erosion caused by trampling and grazing as well as other management practices. For areas located above the agricultural land use, an increase in shallow landslides, as well as sheet erosion, can be observed. This points to climate change as a triggering factor of soil degradation, which has not been identified so far as a factor for soil erosion in the Urseren Valley. While OBIA yields conservative estimations mainly due to limitations of spatial resolutions, the method facilitates a comprehensive overview of the ongoing temporal and spatial development regarding soil degradation within the Urseren Valley.

Historical Trajectory in Vegetation Cover in Northeastern Namibia Based on AVHRR Satellite Imagery (1982–2015)

The negative impact of the reduction of vegetation cover is already being felt in the Zambezi Region in northeastern Namibia. The region has been undergoing various land cover changes in the past decades. To understand the historical trend of vegetation cover (increase or decrease), we analyzed 8-km resolution Global Inventory Monitoring and Modeling Studies (GIMMS) from the Advanced Very High Resolution Radiometer (AVHRR) and 0.25° × 0.25° (resampled to 8 km) resolution Global Precipitation Climatology Center (GPCC). We used the Time Series Segmented Residual Trends (TSS-RESTREND) method. We found that the general trajectory of vegetation cover was negative. Pixel-wise analysis and visual interpretation of historical images both revealed clear signs of vegetation cover change. We observed a single breakpoint in the vegetation trajectory which correlated to the 1991–1992 drought in southern Central Africa. Potential drivers of land cover change are the (il)legal expansion of subsistence farming, population growth, and wood extraction. These findings will serve as a reference for decision makers and policymakers. To better understand the human-induced land cover change at the micro scale and sub-regional level, we recommend using higher resolution remote sensing datasets and historical documents to assess the effect of demographic change, disease, civil unrest, and war.

Drought monitoring and assessment using Landsat TM/OLI data in the agricultural lands of Bandar-e-Turkmen and Gomishan cities, Iran

Investigating agricultural drought is very important in semiarid areas, and it has a significant impact on people’s livelihood, which depends on farming. This research tried to examine the capability of six Landsat surface reflectance bands, vegetation indices (VIs), and drought indices (DIs) for drought monitoring in the agricultural lands of Bandar-e-Turkmen and Gomishan cities in 1986 and 2015. Statistical analysis, Pearson correlation analysis, and correlation matrices between the VIs and DIs with land surface temperature (LST) were monitored separately for each date. In addition, the spatial and temporal drought extents using the Standardized Evapotranspiration Precipitation Index (SPEI) and the Vegetation Health Index (VHI) approaches were determined and compared for both study periods. The correlations between the LST and VIs were negative and significant in both study periods. The range of VI values decreased with increasing temperature in 2015 compared to 1986. The mean surface reflectance of the visible bands (blue, green, red), NIR (near-infrared), SWIR (shortwave infrared), and MWIR (mid-wave infrared) increased in 2015 compared to 1986. A higher spectral reflectance of the visible bands indicated a reduction in vegetation cover or increase in stress in 2015 compared to 1986. Meanwhile, the SWIR and MWIR bands showed that the average surface reflectance increased in 2015, while they showed a lower reflectance in 1986. The results of the Water Supplying Vegetation Index (WSVI) implied that the crop water stress in 2015 was more than that in 1986. The VHIs were separately compared with the NDVI and LST in each period of study. The maximum LST increased from 38 °C in 1986 to 44 °C in 2015. The moderate drought extent was 65% in 2015, while the study area did not experience any drought in 1986. The SPEI maps showed that the entire study area experienced moderate drought in 2015, while no drought was observed in 1986. The results showed that the DIs and VIs and the visible, SWIR and MWIR surface reflectance bands can be effectively used by sampling plots in future drought assessment studies. The present study also emphasizes that there is a similarity between traditional and remote sensing methods and indicates that remote sensing data can be effectively used instead of traditional approaches when there is no meteorological station. The results would be useful in food security and sustainable agriculture management plans.

Digging mammal reintroductions reduce termite biomass and alter assemblage composition along an aridity gradient.

Invasions can trigger cascades in ecological communities by altering species interactions. Following the introduction of cats and foxes into Australia, one tenth of Australia's terrestrial mammal species became extinct, due to predation, while many continue to decline. The broader consequences for Australian ecosystems are poorly understood. Soil-dwelling invertebrates are likely to be affected by the loss of fossorial native mammals, which are predators and disturbance agents. Using reintroductions as a model for ecosystems prior to species loss, we tested the hypothesis that mammal reintroduction leads to reduced vegetation cover and altered termite assemblages, including declines in abundance and biomass and changed species composition. We hypothesised that the magnitude of mammal reintroduction effects would diminish with increasing aridity, which affects resource availability. We compared six paired sites inside and outside three reintroduction sanctuaries across an aridity gradient. We sampled termite assemblages using soil trenches and measured habitat availability. Reintroductions were associated with increased bare ground and reduced vegetation, compared with controls. Aridity also had an underlying influence on vegetation cover by limiting water availability. Termite abundance and biomass were lower where mammals were reintroduced and the magnitude of this effect decreased with increasing aridity. Termite abundance was highest under wood, and soil-nesting wood-feeders were most affected inside sanctuaries. Ecological cascades resulting from exotic predator invasions are thus likely to have increased termite biomass and altered termite assemblages, but impacts may be lower in less-productive habitats. Our findings have implications for reserve carrying capacities and understanding of assemblage reconstruction following ecological cascades.

Increased precipitation offsets the negative effect of warming on plant biomass and ecosystem respiration in a Tibetan alpine steppe

The Tibetan Plateau has become warmer and wetter in recent decades, and the warming of more than 2 °C has been considered as a risk threshold that may lead to irreversible changes in arid and semi-arid grassland ecosystems. However, few data have examined the extent to which the projected increase of precipitation may offset the negative effect of 2 °C warming on aboveground biomass (AGB) and ecosystem respiration (Re) in the vast alpine grasslands. We conducted a field manipulative experiment to investigate the combined effects of 2 °C warming plus 15% and 30% increased precipitation on AGB and Re in an alpine steppe. We observed vegetation cover, AGB, Re, soil temperature (ST), soil moisture (SM), and soil organic carbon (SOC) in the growing seasons of 2013 and 2014. Thornthwaite moisture index (MI) in the growing season (May–September) was calculated for each experimental treatment. Experimental warming generally increased ST and reduced SM and MI, and consequently caused significant reductions in vegetation cover, AGB and Re. Increased precipitation typically stimulated AGB and Re. Compared to the control, relative changes in AGB and Re increased from a negative value under warming with ambient precipitation to a positive value under warming plus 15% and 30% increased precipitation. In pooled data across treatments and years, the changes of AGB and Re showed a positive linear relation to the warming/watering induced variation of MI. The structural equation modeling indicated that AGB and SM rather than ST and SOC were the major factors driving Re during the growing season. In addition, experimental warming decreased the temperature sensitivity of Re (Q10), whereas increased precipitation had a positive effect on Q10. Our data demonstrate that the water deficit induced by 2 °C warming and its negative effect on AGB and Re can be offset by >15% increased precipitation in a semi-arid alpine grassland on the Tibetan Plateau. The change in balance of precipitation and evapotranspiration is an ecologically meaningful metric for generally describing the spatiotemporal variability of soil water availability and ecosystem function under climate change.

Stress-tolerant ants and the impact of quarries on an ant community in Patagonia

Aggregate extraction is an activity that has increased considerably in recent years in Patagonia, providing raw material for road paving and construction industry. This activity deeply impacts soil composition and the biota. Ants are among the most important inhabitants of soils, and are useful indicators of the impact of human activities on ecosystems. This study determines the effect of aggregate extraction activities on a community of ants in a semiarid area of Argentinean Patagonia. In two abandoned quarries, disturbed and nearby control areas were delimited; ants were sampled using pitfall traps and different environmental variables were measured. Our analysis show that many environmental variables were altered in disturbed sites, with a reduction in vegetation cover, modification of percentage of fine grain and soil humidity, and an increase in soil pH and temperature. Thirteen ant species were identified. The Opportunists predominated in disturbed sites, in particular the species Dorymyrmex tener. The results reveal for the first time the behaviour of the ant community of this semiarid region in the face of a disturbance that directly impacts the soil. The focus on stress-tolerant species for restoration purposes deserves further study.

Altered leaf elemental composition with climate change is linked to reductions in photosynthesis, growth and survival in a semi‐arid shrubland

Abstract Climate change will increase heat and drought stress in many dryland areas, which could reduce soil nutrient availability for plants and aggravate nutrient limitation of primary productivity. Any negative impacts of climate change on foliar nutrient contents would be expected to negatively affect the photosynthetic capacity, water use efficiency and overall fitness of dryland vegetation. We conducted a 4‐year manipulative experiment using open top chambers and rainout shelters to assess the impacts of warming (~2°C, W), rainfall reduction (~30%, RR) and their combination (W + RR) on the nutrient status and ecophysiological performance of six native shrub species of contrasting phylogeny in a semi‐arid ecosystem. Leaf nutrient status and gas exchange were assessed yearly, whereas biomass production and survival were measured at the end of the study. Warming (W and W + RR) advanced shoot growth phenology and reduced foliar macro‐ (N, P, K) and micronutrient (Cu, Fe, Zn) concentrations (by 8%–18% and 14%–56% respectively), net photosynthetic rate (32%), above‐ground biomass production (28%–39%) and survival (23%–46%). Decreased photosynthesis and growth in W and W + RR plants were primarily linked to enhanced nutritional constraints on carbon fixation. Poor leaf nutrient status in W and W + RR plants partly decoupled carbon assimilation from water flux and led to drastic reductions in water use efficiency (WUEi; ~41%) across species. The RR treatment moderately decreased foliar macro‐ and micronutrients (6%–17%, except for Zn) and biomass production (22%). The interactive impacts of warming and rainfall reduction (W + RR treatment) on plant performance were generally smaller than expected from additive single‐factor effects. Synthesis. Large decreases in plant nutrient pool size and productivity combined with increased mortality during hotter droughts will reduce vegetation cover and nutrient retention capacity, thereby disrupting biogeochemical processes and accelerating dryland degradation with impending climate change. Increased macro‐ and micronutrient co‐limitation of photosynthesis with forecasted climate change conditions may offset any gains in WUEi and productivity derived from anthropogenic CO2 elevation, thereby increasing dryland vegetation vulnerability to drought stress in a warmer and drier climate. The generalized reduction in leaf nutrient contents with warming compromises plant nutritional quality for herbivores, with potential cascading negative effects across trophic levels.

An assessment of soil salinity and vegetation cover changes for a part of An-Najaf governorate using remote sensing data

This paper deals with assessing and detecting the changes of soil salinity and vegetation cover for a part of An-Najaf Governorate and verification regarding the impression of soil salinity on the change of vegetative regions, over the period from 2001 to 2015. The results demonstrated a clear reduction in vegetative cover with salinity rates increased. The normalized difference vegetation index (NDVI) and Soil Salinity Index (SI) were applied for each date using the multispectral images derived from Landsat ETM+ and OLI data. Then image differencing technique was utilized to detect the change/no-change for vegetation and salinity for the two study periods. The results revealed that soil salinity increased from 6.36 in 2001-2009 period to 10.59% in 2009-2015, whereas the vegetation cover deteriorated to 9.95 % for the same period. Finally, the strong inverse correlation which found in this paper between NDVI and SI emphasizes that vegetation cover on long term is heavily and directly affected by changes of soil salinity.

Natural background and anthropogenic drivers of vegetation cover changes in pasture landscape: the case of Central Mongolia

The article analyzes natural, first of all, geomorphological and lithological-edaphic conditions and anthropogenic (increase in livestock and change in the structure of the herd) factors determining the degradation of vegetation in the landscapes of the desert steppes of Mongolia. The sources for the assessment of vegetation cover were the images of Landsat 5 and 8 by which were calculated NDVI index, a joint index of the BSI + LDI and the synthesis of channels for 7—5—3 (Landsat 8) and 7—4—2 (Landsat 5). To assess the role of natural conditions in ArcMap package was built model of geotopes, containing data on the absolute height of the area, its position in the system of landscape levels, the genesis and the type of ground. The analysis of the contribution of anthropogenic factors is carried out on the basis of statistics on somons. It was revealed that in 1990—2015 the number of cattle varied from 1.1 to 2.8 million heads, and in all somons (districts) of Srednegobiisky aimag (region) the increase in the number was due to sheep and goats. It was found that a 47 % of the area of aimag has reduced vegetation cover, and to the greatest extent these processes are typical for different formations of the desert steppe subzone in the Northern and Central parts of aimag. Verification of the obtained results was carried out according to the data of field studies of the Russian-Mongolian complex biological expedition of RAS and AMS. Landscapes potentially susceptible to degradation occupy 60 % of the aimagʼs territory. Among the already transformed landscape sites eluvial and transeluvial geotopes of the socle plains on rocks of mixed composition prevail. It is shown that under similar trends of livestock changes pasture ecosystems of somons with predominance of such landscape sites are more prone to degradation than others.

Analysis of Impacts of Land Use Changes in Kitengela Conservation Area on Migratory Wildlife of Nairobi National Park, Kenya

Nairobi National Park (NNP) in Kenya was established in 1946 to conserve the abundance and diversity of wildlife in the Kitengela-Athi-Kaputei plains, from excessive exploitation. It is currently fenced except on the Kitengela side across the Mbagathi River due to the sub-division of the group ranches, which commenced in the 1980s, limiting access of wildlife to the migratory corridor and dispersal areas. This paper is based on a study conducted to assess the impacts of the resultant land use changes in the Kitengela dispersal area/ migratory corridor on the migratory fauna of NNP, and to identify appropriate mitigation measures. The findings indicated that increased human settlement, led to changes in land uses which resulted into multiple negative impacts on the migratory wildlife of Nairobi National Park, mainly due to loss of dispersal area and blockage of migratory routes, leading to wildlife confinement, decreased wildlife tolerance and increased incidences of human wildlife conflicts. Data analysis indicated decline in migratory wildlife population thus negative effect (F=, 6.066, p&lt;0.05). The findings also indicated that loss of migratory routes/dispersal area and reduced vegetation cover was regarded by 55% of the local community respondents as one of the main consequences of the land use changes resulting from the subdivision of the group ranches leading to decreased wildlife tolerance (β = 0.246) and wildlife confinement (β = 0.371) in NNP (p= 0.021, &lt; 0.05, F= 2.678; R=0.179, R2= 0.032). The paper also discusses the mitigation measures for the longtime sustainability of the park, the dispersal area and migratory corridor, including holistic implementation of the Kitengela-Isinya-Kipeto Local Physical Development Plan, mapping and protection of the vital wildlife areas within the migratory range, including the wildebeest calving area in North Kaputiei.

Fire resilience of a rare, freshwater crustacean in a fire‐prone ecosystem and the implications for fire management

AbstractUnderstanding species’ responses to fire regimes, particularly rare or threatened species, is important for land managers tasked with managing for biodiversity. Hickman's Allanaspides (Allanaspides hickmani, Anaspidesidae) is a rare, primitive, shrimp‐like crustacean, with high conservation value. It is restricted to a single catchment in the island state of Tasmania, Australia, where it occurs within moorland pools typically containing crayfish (Ombrastacoides spp.) burrows. Although its moorland habitat has a long history of firing, adverse fire regimes are a potential threat to the species. A large part of its range is subject to planned burning to help manage the detrimental effects of high‐intensity wildfires. The resilience of A. hickmani to low–moderate‐intensity fires was investigated over 13 years using a replicated before‐after‐control‐impact design. The fires resulted in an initial reduction in vegetation cover and surface water and an increase in water temperature. There was no effect of fire on A. hickmani captures 4 months after small‐scale, low‐intensity autumn burns. However, 5 months later, following an unintended larger‐scale, medium‐intensity spring burn, there was an 80–90% reduction in A. hickmani captures and their numbers did not recover until 6–9 years post‐fire. It is not known whether the reduced catch was due to a reduction in the number of A. hickmani or their movement from pools into crayfish burrows. These findings together with evidence of a varied fire history, including high‐intensity wildfires, within their range suggests that A. hickmani and its habitat are resilient to a range of fire frequencies and intensities provided that the fire regime does not degrade or lead to a complete loss of peat. Climate change predictions for warmer and drier summers in western Tasmania will increase the risk of peat loss. Planned burning is likely to be important for the protection of A. hickmani habitat from predicted adverse fire regimes.

Quad bike impacts on vegetation and soil physicochemical properties in an arid ecosystem

The increase use of Off-Road Vehicles (ORVs) coupled with the absence of control strategies have led to extensive use of natural areas for the creation of recreational trails. We assessed the effects of quad bikes on vegetation and soils in an arid ecosystem subjected to intensive quad bike use. We selected randomly eight traffic sites (disturbed sites) and eight adjacent control sites (undisturbed sites). Plant cover and composition were assessed with the point-intercept method and phytosociological census. In each site, we collected soil samples to assess soil physicochemical properties, including apparent specific weight (ASG), actual specific weight (RSG), porosity, texture, electric conductivity (EC) and pH. Soil compaction was measured at 30 spaces points per site. Plant cover and richness was significant lower in disturbed sites, with only four species present in areas subjected to disturbance. There were also changes in species dominance, with native perennial shrubs and grasses characterizing the undisturbed sites while the disturbed sites were mainly dominated by the invasive exotic herb Salsola kali. ORVs traffic also affected soil physicochemical properties including soil compaction, ASG, EC and soil pH. Soil compaction was more than double in disturbed sites and ASG tended to be higher under this condition. The EC was significantly higher and soil pH was significantly lower in the disturbed sites. Reduced vegetation cover and changes to soils physicochemical properties on quadbike trails highlights the impacts of ORVs in the landscape and the need to develop management strategies to minimize disturbance from ORVs on vegetation and soils.

Effect of land use-land cover change on the regimes of surface runoff-the case of Lake Basaka catchment (Ethiopia).

In this study, the effect of land use-land cover change (LULCC) on surface (direct) runoff was estimated for Lake Basaka catchment using the soil conservation services-curve number model in the geospatial information system (ArcInfo), assisted by remote sensing. The result indicated that Lake Basaka catchment experienced a significant LULCC. About 86% of forest coverage and 46% of grasslands were lost over the study period (1973-2015), which were shifted to open bushy woodlands, farms, lake water and wetlands. The runoff responses were observed to be increasing since 1970s, especially after the inception of large-scale irrigation schemes to the region. The highest increase of surface runoff was observed to occur after mid-1980s, which is in line with the significant LULCC and the corresponding increment of lake level in that period. The reduction in vegetation cover has resulted in an increase of runoff coefficient (rc) from 0.07 in the 1960s to about 0.23 in 2000s. The sensitivity analysis result indicated that about 70% of the increase runoff rate in the lake catchment is attributed to LULCC, and the remaining proportion is due to rainfall. However, the effect of extreme rainfall on runoff process could not be underemphasized since it has significant impact especially during extreme events (observed rc of 0.33 in 2008). Overall, when predicting the runoff response of the lake catchment, it is importance to take into account possible future LULCC and evolution.

No evidence of a demographic response to experimental herbicide treatments by the White-crowned Sparrow, an early successional forest songbird

AbstractEarly-successional forest birds, which depend on disturbance events within forested landscapes, have received increased conservation concern because of long-term population declines. Herbicides are often used to control vegetation within early-successional forests, with unknown effects on avian vital rates. We used a large-scale experiment to test how nest and post-fledging survival were influenced by herbicide intensity within managed conifer plantations across 2 breeding seasons. We created a gradient of 4 stand-scale herbicide treatments (light, moderate, and intensive, and no-spray control) and evaluated the reproductive response of the White-crowned Sparrow (Zonotrichia leucophrys), a declining songbird in managed forest landscapes of the Pacific Northwest. Against initial predictions, we found no evidence that either daily nest survival (n &amp;gt; 760 nests across all treatments) or post-fledging survival (n = 70 individuals reared in control and moderate treatments) were influenced by herbicide application intensity. Increased herbicide intensity resulted in an extensive reduction in vegetation cover at both stand and nest-patch scales; in contrast, vegetative cover at nest sites did not differ across herbicide treatments, nor was nest survival related to vegetation concealment measures. As the largest experimental investigation to assess forest herbicide effects on songbird demography, our study indicates that components of sparrow reproductive success were not influenced by experimental vegetation control measures, although additional work on other early-successional species will be useful to evaluate the generalities of our findings.

The Sensitivity of Urban Heat Island to Urban Green Space—A Model-Based Study of City of Colombo, Sri Lanka

Urbanization continues to trigger massive land-use land-cover change that transforms natural green environments to impermeable paved surfaces. Fast-growing cities in Asia experience increased urban temperature indicating the development of urban heat islands (UHIs) because of decreased urban green space, particularly in recent decades. This paper investigates the existence of UHIs and the impact of green areas to mitigate the impacts of UHIs in Colombo, Sri Lanka, using UrbClim, a boundary climate model that runs two classes of simulations, namely urbanization impact simulations, and greening simulations. The urbanization impact simulation results show that UHIs spread spatially with the reduction of vegetation cover, and increases the average UHI intensity. The greening simulations show that increasing green space up to 30% in urban areas can decrease the average air temperature by 0.1 °C. On the other hand, converting entire green areas into urban areas in suburban areas increases the average temperature from 27.75 °C to 27.78 °C in Colombo. This demonstrates the sensitivity of UHI to vegetation cover in both urban and suburban areas. These seemingly small changes are average grid values and may indicate much higher impacts at sub-grid levels.

Responses of soil organic carbon and nutrient stocks to human-induced grassland degradation in a Tibetan alpine meadow

Alpine meadow degradation is a major environmental problem in the Qinghai-Tibetan Plateau of China. While it is expanding at a rapid pace, quantitative information on the effect of grassland degradation on soil properties remains largely unavailable. This study aimed to evaluate the effect of vegetation cover reduction on soil organic carbon (SOC) and nutrient stocks. A degraded alpine meadow with vegetation cover gradients of 90% ± 6.6% to 70% ± 8.3% and 45% ± 8.7% was selected, and soil samples were collected at two soil depths (0–20 and 20–40 cm depths). The reduction in vegetation cover decreased soil sand, SOC, total nitrogen (N), available phosphorus (P), inorganic N, microbial biomass carbon and N, soil moisture, and the ratio of SOC to available P, but increased soil pH, bulk density, the ratio of SOC to total N, and clay and silt contents. The decline in vegetation cover from 90% to 45% significantly affected SOC, total N, total P, and available P stocks at 0–40 cm soil depths (p < 0.05, respectively), with losses as high as 3.89 kg m−2 for SOC, 0.47 kg m−2 for total N, and 1.05 g m−2 for available P. These values corresponded to depletion rates at 28.7%, 39%, and 21%. The increases were as high as 39 g m−2 for total P and corresponded to an increase rate of 15%. The structural stability index had a linear decrease trend with decreasing vegetation cover. The index was >9% at the COV90 site and was close to 5% at the COV45 site for 0–20 cm soil depth. These results confirmed that vegetation cover reduction is a key factor that influences the soil nutrient stocks and structural stability of the alpine meadow. The losses in SOC and nutrients by vegetation cover reduction on the alpine meadow can have a remarkable influence on a large scale. Meanwhile, the alpine meadow may have huge carbon and N sequestration potentials duo to the potential increase of vegetation productivity in this area.

High-resolution record reveals climate-driven environmental and sedimentary changes in an active rift

Young rifts are shaped by combined tectonic and surface processes and climate, yet few records exist to evaluate the interplay of these processes over an extended period of early rift-basin development. Here, we present the longest and highest resolution record of sediment flux and paleoenvironmental changes when a young rift connects to the global oceans. New results from International Ocean Discovery Program (IODP) Expedition 381 in the Corinth Rift show 10s–100s of kyr cyclic variations in basin paleoenvironment as eustatic sea level fluctuated with respect to sills bounding this semi-isolated basin, and reveal substantial corresponding changes in the volume and character of sediment delivered into the rift. During interglacials, when the basin was marine, sedimentation rates were lower (excepting the Holocene), and bioturbation and organic carbon concentration higher. During glacials, the basin was isolated from the ocean, and sedimentation rates were higher (~2–7 times those in interglacials). We infer that reduced vegetation cover during glacials drove higher sediment flux from the rift flanks. These orbital-timescale changes in rate and type of basin infill will likely influence early rift sedimentary and faulting processes, potentially including syn-rift stratigraphy, sediment burial rates, and organic carbon flux and preservation on deep continental margins worldwide.

Chemical alarm cues allow prey to adjust their defensive behaviour to cover abundance

Aquatic prey species show sophisticated mechanisms to adjust their antipredator behaviours to the level of risk, which they estimate either by direct experience with predators or from indirect indicators such as chemical alarm cues released by injured conspecifics. For instance, evidence suggests that the alarm cues of tadpoles exposed to high levels of background predation risk elicit a stronger antipredator response compared to alarm cues of tadpoles exposed to low risk. Similarly, the alarm cues of tadpoles from environments with reduced vegetation cover might cause a stronger response than alarm cues of tadpoles from environments with abundant vegetation because tadpoles suffer high predation when vegetation is scarce. I tested this hypothesis in the edible frog, Pelophylax esculentus, by comparing the response of focal tadpoles (not exposed to vegetation manipulation) to alarm cues of donor tadpoles raised from eggs in either high- or low-vegetation treatment. I also tested the alarm cues of donor tadpoles switched from high- to low-vegetation treatments and vice versa after hatching because this would enable understanding whether an eventual difference in alarm cues occurred due to the embryonic or larval environments and whether the treatments at the two developmental stages had interactive effects. Alarm cues from the low-vegetation, and thus the high-risk, treatment elicited stronger antipredator response in focal tadpoles in comparison to the alarm cues from the high-vegetation, low-risk treatment. Results from switching donor tadpoles between vegetation treatments after hatching suggested that the observed effect was due to the vegetation treatment experienced by donor tadpoles during the larval stage, with no interactive effects. Chemical alarm cues convey information about cover abundance, an environmental factor that indirectly covaries with predation risk.