Tree species diversity and community composition in a human-dominated tropical forest of Western Ghats biodiversity hotspot,India

The structure, function, and ecosystem services of tropical forest depend on its species richness, diversity, dominance, and the patterns of changes in the assemblages of tree populations over time. Long-term data from permanent vegetation plots have yielded a wealth of data on the species diversity and dynamics of tree populations, but such studies have only rarely been undertaken in tropical forest landscapes that support large human populations. Thus, anthropogenic drivers and their impacts on species diversity and community structure of tropical forests are not well understood. Here we present data on species diversity, community composition, and regeneration status of tropical forests in a human-dominated landscape in the Western Ghats of southern India. Enumeration of 40 plots (50 m × 20 m) results a total of 106 species of trees, 76 species of saplings and 79 species of seedlings. Detrended Correspondence Analysis ordination of the tree populations yielded five dominant groups, along disturbance and altitudinal gradients on the first and second axes respectively. Abundant species of the area such as Albizia amara, Nothopegia racemosa and Pleiospermum alatum had relatively few individuals in recruiting size classes. Our data indicate probable replacement of rare, localized, and old-growth ‘specialists’ by disturbance-adapted generalists, if the degradation is continuing at the present scale.     

Ecological Footprint: Refining the carbon Footprint calculation

Within the Ecological Footprint methodology, the carbon Footprint component is defined as the regenerative forest capacity required to sequester the anthropogenic carbon dioxide emissions that is not absorbed by oceans. A key parameter of the carbon Footprint is the Average Forest Carbon Sequestration (AFCS), which is calculated from the net carbon sequestration capacity of forests ecosystems.The aim of this paper is to increase the clarity and transparency of the Ecological Footprint by reviewing the rationale and methodology behind the carbon Footprint component, and updating a key factor in its calculation, the AFCS. Multiple calculation options have been set to capture different rates of carbon sequestration depending on the degree of human management of three types of forest considered (primary forests, other naturally regenerated forests and planted forests). Carbon emissions related to forest wildfires and soil as well as harvested wood product have been included for the first time in this update of the AFCS calculation. Overall, a AFCS value range of 0.73 ± 0.37 t C ha⁻¹ yr⁻¹ has been identified. The resulting carbon Footprint and Ecological Footprint values have then been evaluated based on this value range. Results confirm that human demand for ecosystem services is beyond the biosphere's natural capacity to provide them.     

Defining quantitative stream disturbance gradients and the additive role of habitat variation to explain macroinvertebrate taxa richness

Most studies dealing with the use of ecological indicators and other applied ecological research rely on some definition or concept of what constitutes least-, intermediate- and most-disturbed condition. Currently, most rigorous methodologies designed to define those conditions are suited to large spatial extents (nations, ecoregions) and many sites (hundreds to thousands). The objective of this study was to describe a methodology to quantitatively define a disturbance gradient for 40 sites in each of two small southeastern Brazil river basins. The assessment of anthropogenic disturbance experienced by each site was based solely on measurements strictly related to the intensity and extent of anthropogenic pressures. We calculated two indices: one concerned site-scale pressures and the other catchment-scale pressures. We combined those two indices into a single integrated disturbance index (IDI) because disturbances operating at both scales affect stream biota. The local- and catchment-scale disturbance indices were weakly correlated in the two basins (r = 0.21 and 0.35) and both significantly (p < 0.05) reduced site EPT (insect orders Ephemeroptera, Plecoptera, Trichoptera) richness. The IDI also performed well in explaining EPT richness in the basin that presented the stronger disturbance gradient (R² = 0.39, p < 0.001). Natural habitat variability was assessed as a second source of variation in EPT richness. Stream size and microhabitats were the key habitat characteristics not related to disturbances that enhanced the explanation of EPT richness over that attributed to the IDI. In both basins the IDI plus habitat metrics together explained around 50% of EPT richness variation. In the basin with the weaker disturbance gradient, natural habitat explained more variation in EPT richness than did the IDI, a result that has implications for biomonitoring studies. We conclude that quantitatively defined disturbance gradients offer a reliable and comprehensive characterization of anthropogenic pressure that integrates data from different spatial scales.     

Role of ecosystem components in Cd removal process of aquatic ecosystem

An experiment was conducted using 15 glass aquariums to ascertain the pathways of removal of cadmium through numerical and compositional manipulation of ecosystem components and their role in Cd removal in different aquatic ecosystems. Each aquarium was provided with surface sediment @ 2 kg, filled with 15 L tap water and randomly distributed into five treatments having three replicates in each. Cadmium chloride (CdCl₂) of analytical grade was added @ 2 mg/L to the water of each aquarium and mixed gently. Except for the first one, the other four systems received unio (Lamellidens marginalis, 55 ± 2.5 g) @ 6 pieces/aquarium. Tilapia (Oreochromis mossambicus, 35 ± 3 g) was introduced @ 6 fish/aquarium in the third and fifth systems, whereas pistia (Pistia stratiotes) was introduced @ 50 g/aquarium in the fourth and fifth systems for a 28-day observation period. The samples of water, sediment, unio, fish and pistia were collected from different systems at 7-day intervals and analyzed. Results revealed that mean substantial reduction of Cd in water varied between 1.820 and 1.994 mg/L in different simulated ecosystems. Ecosystem efficiency of Cd removal varied in the different ecosystems and showed highest (11%) value in the ecosystem carrying five components, which suggested a cumulative effect of increasing number of components employed in different simulated aquatic ecosystems significantly facilitated the reduction of the level of Cd concentration in water column. Pistia exerted (12.88–547.5 times) higher rate of Cd accumulation over the other components employed in five simulated ecosystems of various component structures. Therefore, in the present study, it may be concluded that ecosystems carrying five components exhibited the best performance for optimum minimization of Cd removal from water column. It can also be concluded that ecosystem components showed a variable performance and pistia was the efficient component from the perspective of Cd removal.     

Diatoms as indicators of isolated herbaceous wetland condition in Florida,USA

Benthic, epiphytic, and phytoplanktonic diatoms, as well as soil and water physical–chemical parameters, were sampled from 70 small (average 0.86 ha) isolated depressional herbaceous wetlands located along a gradient of human disturbance in peninsular Florida to (1) compare diatom assemblage structure between algal types; (2) develop biological indicators of wetland condition; (3) examine synecological relationships between diatom structure and environmental variables, with the ultimate goal of developing an index of biological integrity using a single assemblage. Collected diatom samples were enumerated to 250 valves and identified to species or subspecies. An assessment of wetland condition was made using a landscape-scale human disturbance score (Landscape Development Intensity index, LDI), calculated for each site using land use maps and GIS.Assemblages from both impaired and reference sites were compared using blocked multi-response permutation procedures, the percent similarity index, and visually examined using non-metric multidimensional scaling (NMDS). No ecologically significant compositional differences were found within sites. Mantel's test (Mantel's r = 0.29, p < 0.0001) and NMDS (stress: 14.52, variance: 78.5%) identified epiphytic diatoms as the most responsive to human disturbance. Strong significant correlations (|r_s| > 0.50, p < 0.05) were found between epiphytic NMDS site scores and soil pH, specific conductivity, water total phosphorous, and LDI, while soil pH, water color, soil TP, and turbidity were also significantly correlated (p < 0.05).Metrics to assess wetland condition were developed using epiphytic abundance data. Epiphytic taxa sensitive or tolerant to human landscape modification were identified using Indicator Species Analysis, and autecological indices relating diatom sensitivity to nutrients, pH, dissolved oxygen levels, saprobity, salinity, and trophic status were calculated. Fourteen final metrics were identified, scored on an ordinal scale, and combined into the Diatom Index of Wetland Condition (DIWC). The DIWC was highly correlated with the disturbance score (Spearman's r_s = −0.71, p < 0.0001), although the results need to be validated.     

Quantifying human disturbance on antipredator behavior and flush initiation distance in yellow-bellied marmots

Human disturbance may differentially affect the behavior of wild animals and such behavioral perturbations may have fitness consequences. To understand the effects of specific types of human disturbance on antipredator behavior, a behavior whose performance enhances survival, we studied yellow-bellied marmots (Marmota flaviventris). We quantified both antipredator vigilance and the flight initiation distance of the marmots to an approaching human in six different colony sites where we also quantified the frequency and type of human visitation. We developed an analysis framework, using linear mixed models, and found that: (1) when the presence of motorized vehicles and bicycles was high, marmots increased the proportion of time spent vigilant (pseudo R² = 0.33 and 0.31 for motorized vehicles and bicycles, P < 0.05) and decreased the time spent foraging (pseudo R² = 0.29 and 0.23 for motorized vehicles and bicycles, P < 0.05), (2) there was no significant effect of the presence of pedestrians on the time allocated to vigilance and foraging (pseudo R² = 0.25 and 0.19, P > 0.05), (3) marmots decreased the flight initiation distance as disturbance of motorized vehicles (pseudo R² = 0.85) and pedestrians (pseudo R² = 0.84) increased (P < 0.05), and (4) when we considered bicycles as the disturbance, juveniles tolerated closer approaches than adults or yearlings (P < 0.001). Marmots thus responded to some human disturbance by adjusting time spent in foraging and shortening the tolerance distance. Since these behavioral responses could have significant implications for survival and reproduction, we should generally view human disturbance as something that can influence natural antipredator behavior. Importantly, based on an understanding of the differential effects of human activities on wildlife, reducing human disturbance should be taken into account for wildlife management. In addition, our approach will be useful to quantify differential effects of humans on wildlife and to enhance our ability to manage those impacts.     

Loss of aboveground forest biomass and landscape biomass variability in Missouri,US

Disturbance regimes and forests have changed over time in the eastern United States. We examined effects of historical disturbance (circa 1813 to 1850) compared to current disturbance (circa 2004 to 2008) on aboveground, live tree biomass (for trees with diameters ≥13 cm) and landscape variation of biomass in forests of the Ozarks and Plains landscapes in Missouri, USA. We simulated 10,000 one-hectare plots using random diameters generated from parameters of diameter distributions limited to diameters ≥13 cm and random densities generated from density estimates. Area-weighted mean biomass density (Mg/ha) for historical forests averaged 116 Mg/ha, ranging from 54 Mg/ha to 357 Mg/ha by small scale ecological subsections within Missouri landscapes. Area-weighted mean biomass density for current forests averaged 82 Mg/ha, ranging from 66 Mg/ha to 144 Mg/ha by ecological subsection for currently forested land. Biomass density of current forest was greater than historical biomass density for only 2 of 23 ecological subsections. Current carbon sequestration of 292 TgC on 7 million ha of forested land is less than half of the estimated historical total carbon sequestration of 693 TgC on 12 million ha. Cumulative tree cutting disturbances over time have produced forests that have less aboveground tree biomass and are uniform in biomass compared to estimates of historical biomass, which varied across Missouri landscapes. With continued relatively low rates of forest disturbance, current biomass per ha will likely increase to historical levels as the most competitive trees become larger in size and mean number of trees per ha decreases due to competition and self-thinning. Restoration of large diameter structure and forested extent of upland woodlands and floodplain forests could fulfill multiple conservation objectives, including carbon sequestration.     

Quantification and assessment of changes in ecosystem service in the Three-River Headwaters Region,China as a result of climate variability and land cover change

Rapid and periodic assessment of the impact of land cover change and climate variability on ecosystem services at regional levels is essential to understanding services and sustainability of ecosystems. This study focused on quantifying and assessing the changes in multiple ecosystem services in the Three-River Headwaters Region (TRHR), China in 2000–2012. Based on the widely used biophysical models including Integrated Valuation of Ecosystem Services and Trade-Offs (InVEST), Revised Wind Erosion Equation (RWSQ), and Carnegie-Ames-Stanford Approach (CASA) models, this study assessed the historical flow of regulating services, including soil conservation, water yield, and carbon sequestration, and provisioning service food provision. The soil conservation function of ecosystem was slightly enhanced as a whole, and water yield increased sharply, with both the soil conservation and water yield showing an increasing spatial homogenization. The net primary productivity (NPP) and food production increased substantially from 2000 to 2012. Ecosystem services are closely and complexly interlinked. The correlation analyses indicated a trade-off between the water yield and carbon sequestration, however, a synergy between soil conservation and carbon sequestration. Congruence between the three different ecosystem provisioning services, including pasture, meat, and grain, was found. There was also a synergy between food production and ecosystem carbon sequestration in the TRHR. Climatic variability and vegetation restoration are important for the ecosystem services flow. Correlation analyses showed that the increase in precipitation significantly enhanced the water yield (P < 0.01) and soil erosion (P < 0.01), while the temperature increase influenced positively the NPP (P < 0.1). The experience of ecological rehabilitation and the change in key ecosystem services in the TRHR exemplified the positive effects of environmental policies and the necessity of adopting an adaptive management approach. Thus the ecological construction and policy making should take climate variability into account, and facilitate synergies on multiple ecosystem services in order to maximize human well-being and preserve its natural ecosystems.     

Epilithon δ15N signatures indicate the origins of nitrogen loading and its seasonal dynamics in a volcanic Lake

The intensification of agricultural land use and urbanisation has increased nutrient loads in aquatic ecosystems. Nitrogen loads can alter ecosystem structure and functioning, resulting in increased algal productivity, algal blooms and eutrophication. The principal aim of the present paper is to extend the use of epilithic δ¹⁵N signatures to a lake ecosystem in order to evaluate the potential impact of anthropogenic nitrogen discharges (organic and inorganic) that can also reach coastal waters.Epilithic associations were collected from volcanic rocks in different seasons in shallow water along the entire perimeter of Lake Bracciano and analysed for their nitrogen stable isotope signatures. Furthermore, some stones were moved from an unpolluted site to a polluted one in order to verify the effect on the nitrogen signature of the epilithic association. The epilithon’s δ¹⁵N signatures provided strong evidence of the space-time variability of N inputs. The differing quality of nitrogen loads was reflected in high isotopic variation within the lake, especially at the beginning of summer (1.7‰ ≤ δ¹⁵N ≤ 13.3‰), while in winter, when anthropogenic pressure was lowest, the δ¹⁵N signature variation was less accentuated (3.1‰ ≤ δ¹⁵N ≤ 7.6‰). At all sampling times, spatial variability was found to be related to the various human activities along the lake shore (especially tourism and agriculture), while seasonal variation at all sampling sites was related to the intensity of anthropogenic pressures (higher in summer and lower in winter).Our results showed that epilithic algal associations and the physicochemical properties of the water did not influence the δ¹⁵N signature, which in contrast was strongly related to the site-specific effect of human activities around the lake. Thus, the distribution of δ¹⁵N across space and time can be used to direct nutrient reduction strategies in the region and can assist in monitoring the effectiveness of environmental protection measures.     

An advanced Index of Biotic Integrity for use in tropical shallow lowland streams in Costa Rica: Fish assemblages as indicators of stream ecosystem health

This paper presents an advanced version of the Index of Biotic Integrity (IBI), a multimetric index to indicate ecosystem health. The multimetric index has been adapted in such a way that it not only indicates overall condition but also specific causes of environmental disturbance. The newly developed index (a) uses data of tolerant as well as intolerant species in a single metric to indicate environmental disturbance, (b) does not require knowledge about species from the literature, and (c) can be applied to artificial landscapes.The metrics proposed here consist of indicator species assemblages that are selected directly for their relationship with an environmental component or specific type of environmental degradation. Thus, each metric indicates a type of environmental concern, which enables conservation practices to be targeted more effectively. Species assemblages for each single metric consist of a combination of species that can be negatively and positively related to environmental disturbances, providing a better indication of stream ecosystem health.The area studied was assumed to be too diverse for one single index. Canonical Indirect-Gradient Principal Component Analysis indicated that the optimal division of subindices based on stream typology was for streams with drainage basin sizes <10 km² and >10 km². Pearson Product-Moment Correlations were used to identify relationships between anthropogenic disturbances and the composition and abundance of fish species at impacted as well as undisturbed sites. This index proved to be useful for indicating overall stream ecosystem health as well as local onsite environmental disturbances or the environmental components of greatest concern. This index does require extensive information about measured levels of anthropogenic disturbances with the accompanying composition and abundance of fish species.     

Drivers of reptile and amphibian assemblages outside the protected areas of Western Ghats,India

Biodiversity conservation in forested landscapes outside protected areas is important to sustain populations of species with restricted ranges. However, such habitats face many anthropogenic threats, including logging, extraction of firewood and leaf-litter for mulch in plantations. In this study, we determined the effects of forest degradation on amphibians and reptiles in forests outside protected areas by measuring their species richness and community composition across a disturbance gradient from near pristine to highly degraded forests in Agumbe, Western Ghats, India. Twenty-one strip 15 m × 150 m transects were laid across the disturbance gradient and diurnal visual encounter surveys were conducted. Sampling was repeated three times per transect covering the dry, intermediate and wet seasons. Amphibian and reptile communities were affected by the decrease in canopy cover and leaf litter volume, respectively. Our results indicate that the collection of firewood and leaf-litter can severely affect amphibian and reptile populations. Structured conservation planning outside of protected areas is therefore imperative.     

Distribution characteristics and factors influencing the ecosystem in western Hubei

Western Hubei is the most concentrated area of forest resources in Hubei Province, and the knowledge of the distribution characteristics of ecosystem carbon density is important to understand the regional characteristics of carbon density and its mechanism of formation. Carbon density and factors influencing different layers in the ecosystem were studied by using field data. The average carbon density of ecosystems in western Hubei was 159.05 t/hm²; the carbon density of different forest types in descending order was Abies fargesii forests (362.25 t/hm²), mixed broadleaf-conifer forests (154.13 t/hm²), broad-leaved forests (146.09 t/hm²), and coniferous forests (135.76 t/hm²), and ecosystem carbon density increased with increasing age. The carbon density of the arborous layer, shrub layer, and soil layer of A. fargesii forests was significant higher than that of the other forests (P < 0.05), indicating the carbon storage per unit area of A. fargesii forests, which grow at higher elevations, was the greatest. The carbon density in arborous layers of broad-leaved forests, mixed broadleaf-conifer forests, and coniferous forests was 39.29 t/hm², 48.99 t/hm², and 48.39 t/hm², respectively. Those of the soil layer were 102.96 t/hm², 100.97 t/hm², and 82.37 t/hm², respectively, and there were no significant differences among them. Among the three forest types, carbon density in the litter layer was greater than that of the shrub layer, which indicated the litter layer plays an important role in carbon storage. The carbon density of mixed broadleaf-conifer forests was greatest, excluding A. fargesii forests, in medium (58.71 t/hm²) and mature forests (79.66 t/hm²). Thus, the carbon sink of mixed broadleaf-conifer forests had more potential than the others at the medium and mature forest stage. The soil layer carbon density in different forests constituted 60.67—70.48% of the entire ecosystem, and was 1.70—2.62 times greater than that of the arborous layer. There are many factors influencing ecosystem carbon density, which result from the interaction of environmental and topographical factors. The main explanatory variables of carbon density of the region were altitude, precipitation, and canopy density. The vegetation and soil layer carbon density increased as altitude increased, and the rate of change for every vertical 100 m was 1.3 t/hm² and 1.9 t/hm², respectively (P < 0.05). Although the annual average precipitation only affected the carbon density of the vegetation, it increased to 4 t/hm² (P < 0.01) when average precipitation was >100 mm.     

Long-term changes of ecosystem services at Solling,Germany: Recovery from acidification,but increasing nitrogen saturation?

Time series of values of ingenious parameters indicating ecosystem services from European beech and Norway spruce ecosystems at Solling, Germany, were evaluated with respect to resilient or adaptive behaviour. Studied indicators comprise the use of monitoring data with up to more than 40 years of observation on deposition of potential acidity, sulphate (SO₄²⁻) budgets, exchangeable base cation pools, Bc/Al ratio in soil solution, nitrogen (N) budgets, foliar nutrition as indicated by the foliar Bc/N ratio, and defoliation. Deposition of potential acidity decreased considerably at both ecosystems. SO₄²⁻ budgets reveal retention of sulphur in the soils affecting acid/base budgets. Exchangeable base cation pools decreased at both ecosystems by about 60%. Bc/Al ratio in soil solution in the mineral soil was mostly below critical limits indicating potential toxic stress to tree roots. N retention in the soils decreased from about 40 kg ha⁻¹ yr⁻¹ in the 1970s to currently very low rates of 0–20 kg ha⁻¹ yr⁻¹ indicating increasing N saturation. Foliar Bc/N ratio decreased at the spruce ecosystem indicating possible nutrient imbalances. Defoliation at both Solling ecosystems is on a high level compared to other forests in Germany, but reveals no distinct relation to soil acidification or N saturation. From the selected indicators, SO₄²⁻ and N budgets reveal resilient behaviour, whereas indicators related to the acid/base status tend to adaptive behaviour.     

Proton production from nitrogen transformation drives stream export of base cations in acid-sensitive forested watersheds

The biogeochemical cycles of nitrogen (N) and base cations (BCs), (i.e., K⁺, Na⁺, Ca²⁺, and Mg²⁺), play critical roles in plant nutrition and ecosystem function. Empirical correlations between large experimental N fertilizer additions to forest ecosystems and increased BCs loss in stream water are well demonstrated, but the mechanisms driving this coupling remain poorly understood. We hypothesized that protons generated through N transformation (PPR_N)—quantified as the balance of NH₄⁺ (H⁺ source) and NO₃⁻ (H⁺ sink) in precipitation versus the stream output will impact BCs loss in acid-sensitive ecosystems. To test this hypothesis, we monitored precipitation input and stream export of inorganic N and BCs for three years in an acid-sensitive forested watershed in a granite area of subtropical China. We found the precipitation input of inorganic N (17.71 kg N ha⁻¹ year⁻¹ with 54% as NH₄⁺–N) was considerably higher than stream exported inorganic N (5.99 kg N ha⁻¹ year⁻¹ with 83% as NO₃⁻–N), making the watershed a net N sink. The stream export of BCs (151, 1518, 851, and 252 mol ha⁻¹ year⁻¹ for K⁺, Na⁺, Ca²⁺, and Mg²⁺, respectively) was positively correlated (r = 0.80, 0.90, 0.84, and 0.84 for K⁺, Na⁺, Ca²⁺, and Mg²⁺ on a monthly scale, respectively, P < 0.001, n = 36) with PPR_N (389 mol ha⁻¹ year⁻¹) over the three years, suggesting that PPR_N drives loss of BCs in the acid-sensitive ecosystem. A global meta-analysis of 15 watershed studies from non-calcareous ecosystems further supports this hypothesis by showing a similarly strong correlation between ∑BCs output and PPR_N (r = 0.89, P < 0.001, n = 15), in spite of the pronounced differences in environmental settings. Collectively, our results suggest that N transformations rather than anions (NO₃⁻ and/or SO₄²⁻) leaching specifically, are an important mediator of BCs loss in acid-senstive ecosystems. Our study provides the first definitive evidence that the chronic N deposition and subsequent transformation within the watershed drive stream export of BCs through proton production in acid-sensitive ecosystems, irrespective of their current relatively high N retention. Our findings suggest the N-transformation-based proton production can be used as an indicator of watershed outflow quality in the acid-sensitive ecosystems.     

Uncertainty in detecting the disturbance history of forest ecosystems using dendrochronology

QuestionsUncertainty in detecting disturbance histories has long been ignored in dendrochronological studies in forest ecosystems. Our goal was to characterize this uncertainty in relation to the key parameters of forest ecosystems and sample size. In addition, we aimed to provide a method to define uncertainty bounds in specific forest ecosystems with known parameters, and to provide a required (conservative) minimal sample size to achieve a pre-defined level of uncertainty if no actual key forest parameters are known.LocationTraining data were collected from Žofínský Prales (48°40′N, 14°42′E, 735–830 m a.s.l., granite, Czech Republic).MethodsWe used probability theory and expressed uncertainty as the length (the difference between the upper and lower bounds) of the 95% confidence interval. We studied the uncertainty of (i) the initial growth of trees – if they originated under canopy or in a gap; and (ii) the responses to disturbance events during subsequent growth – on the basis of release detection in the radial growth of trees. These two variables provide different information, which together give a picture of the disturbance history. While initial growth date the existence of a gap in a given decade (recent as well as older gaps are included), release demonstrates the moment of a disturbance event.ResultsWith the help of general mathematical deduction, we have obtained results valid across vegetation types. The length of a confidence interval depends on the sample size, proportion of released trees in a population, as well as on the variability of tree layer features (e.g., crown area of suppressed and released trees).ConclusionsMost studies to date have evaluated the initial growth of trees with higher uncertainty than for canopy disturbed area. The length of the 95% confidence interval for detecting initial growth has been rarely shorter than 0.1 (error ± 5%) and has mostly been much longer. To reach 95% confidence interval length of 0.1 (error ± 5%) when detecting the canopy disturbed area, at least 485 tree cores should be evaluated in studied time period, while to reach a 0.05 interval length (error ± 2.5%) at least 1925 tree cores are required. Our approach can be used to find the required sample size in each specific forest ecosystem to achieve pre-defined levels of uncertainty while detecting disturbance history.     

Ecophysiological requirements on seed germination of a Mediterranean perennial grass (Stipa tenacissima L.) under controlled temperatures and water stress

Stipa tenacissima L. (alpha grass) steppes are one of the most representative ecosystems in arid Mediterranean ecosystems. On the one hand these steppes, which are perpetually exposed to climate and strong anthropogenic pressure, have undergone severe degradation. On the other hand, the ability of S. tenacissima to regenerate naturally is significantly reduced. In this study the germination response and seedling emergence of S. tenacissima are examined in relation to the main environmental factors (water stress and temperature) under laboratory-controlled conditions. The main aim of this paper was to investigate the influence of temperature over a temperature range (10 °C–30 °C) and water stress induced by the solutions of polyethylene glycol (PEG)-6000 (0 to − 1.6 MPa) for a period of 30 days, on the germination behavior of S. tenacissima seeds. The results showed that temperatures between 10° and 20 °C seem to be favorable for the germination of this species, with optimum temperatures among accessions found in 20 °C. When seeds were water-stressed, germination severely decreased at − 0.8 MPa, indicating that the accession resistance limits to the water stress, and was completely inhibited at − 1.6 MPa. Consequently, the final germination percentage (FGP) decreased and the mean time germination (MTG) increased. Based on the empirical data of the germination rate, we estimated that the parameters of the thermal time and hydrotime models showed different values in all accessions which proves the difference between accession adaptive capacities.     

Evaluating the performance of multiple remote sensing indices to predict the spatial variability of ecosystem structure and functioning in Patagonian steppes

Assessing the spatial variability of ecosystem structure and functioning is an important step towards developing monitoring systems to detect changes in ecosystem attributes that could be linked to desertification processes in drylands. Methods based on ground-collected soil and plant indicators are being increasingly used for this aim, but they have limitations regarding the extent of the area that can be measured using them. Approaches based on remote sensing data can successfully assess large areas, but it is largely unknown how the different indices that can be derived from such data relate to ground-based indicators of ecosystem health. We tested whether we can predict ecosystem structure and functioning, as measured with a field methodology based on indicators of ecosystem functioning (the landscape function analysis, LFA), over a large area using spectral vegetation indices (VIs), and evaluated which VIs are the best predictors of these ecosystem attributes. For doing this, we assessed the relationship between vegetation attributes (cover and species richness), LFA indices (stability, infiltration and nutrient cycling) and nine VIs obtained from satellite images of the MODIS sensor in 194 sites located across the Patagonian steppe. We found that NDVI was the VI best predictor of ecosystem attributes. This VI showed a significant positive linear relationship with both vegetation basal cover (R² = 0.39) and plant species richness (R² = 0.31). NDVI was also significantly and linearly related to the infiltration and nutrient cycling indices (R² = 0.36 and 0.49, respectively), but the relationship with the stability index was weak (R² = 0.13). Our results indicate that VIs obtained from MODIS, and NDVI in particular, are a suitable tool for estimate the spatial variability of functional and structural ecosystem attributes in the Patagonian steppe at the regional scale.     

From instantaneous to continuous: Using imaging spectroscopy and in situ data to map two productivity-related ecosystem services

Spatially well-informed decisions are essential to sustain and regulate processes and ecosystem services (ES), and to maintain the capacity of ecosystems to supply services. However, spatially explicit ES information is often lacking in decision-making, or exists only as ES maps based on categorical land cover data. Remote sensing (RS) opens new pathways to map ES, in particular biophysical ES supply. We developed an observation-based concept for spatially explicit and continuous ES mapping at landscape scale following the biophysical part of the ES cascade. We used Earth observations in combination with in situ data to map ecosystem properties, functions, and biophysical ES supply. We applied this concept in a case study to map two ES: carbon dioxide regulation and food supply. Based on Earth observations and in situ data, we determined the ecosystem property Sun-Induced chlorophyll Fluorescence (SIF) to indicate ecosystem state and applied scaling models to estimate gross primary production (GPP) as indicator for ecosystem functioning and consequently carbon dioxide regulation and food supply as ES.Resulting ES maps showed heterogeneous patterns in ES supply within and among ecosystems, which were particularly evident within forests and grasslands. All investigated land cover classes were sources of CO₂, with averages ranging from ‐66 to ‐748 g C m^‐2 yr^‐1, after considering the harvest of total above ground biomass of crops and the storage organ, except for forest being a sink of CO₂ with an average of 105 g C m^‐2 yr^‐1. Estimated annual GPP was related to food supply with a maize grain yield average of 9.5 t ha^‐1 yr^‐1 and a sugar beet root yield of 110 t ha^‐1 yr^‐1. Validation with in situ measurements from flux towers and literature values revealed a good performance of our approach for food supply (relative RMSE of less than 23%), but also some over- and underestimations for carbon dioxide regulation. Our approach demonstrated how RS can contribute to spatially explicit and continuous ES cascade mapping and suggest that this information could be useful for environmental assessments and decision-making in spatial planning and conservation.