Pure Evergreen Research Articles

Vegetation Type Mapping in Southern Patagonia and Its Relationship with Ecosystem Services, Soil Carbon Stock, and Biodiversity

Vegetation Type (VT) mapping using Optical Earth observation data is essential for the management and conservation of natural resources, as well as for the evaluation of the supply of provisioning ecosystem services (ESs), the maintenance of ecosystem functions, and the conservation of biodiversity in anthropized environments. The main objective of the present work was to determine the spatial patterns of VTs related to climatic, topographic, and spectral variables across Santa Cruz province (Southern Patagonia, Argentina) in order to improve our understanding of land use cover at the regional scale. Also, we examined the spatial relationship between VTs and potential biodiversity (PB), ESs, and soil organic content (SOC) across our study region. We sampled 59,285 sites sorted into 19 major categories of land cover with a reliable discrimination level from field measurements. We selected 31 potential predictive environmental dataset covariates, which represent key factors for the spatial distribution of land cover such as climate (four), topography (three), and spectral (24) factors. All covariate maps were generated or uploaded to the Google Earth Engine cloud-based computing platform for subsequent modeling. A total of 270,292 sampling points were used for validation of the obtained classification map. The main land cover area estimates extracted from the map at the regional level identified about 142,085 km2 of grasslands (representing 58.1% of the total area), 38,355 km2 of Mata Negra Matorral thicket (15.7%), and about 25,189 km2 of bare soil (10.3%). From validation, the Overall Accuracy and the Kappa coefficient values for the classification map were 90.40% and 0.87, respectively. Pure and mixed forests presented the maximum SOC (11.3–11.8 kg m−2), followed by peatlands (10.6 kg m−2) and deciduous Nothofagus forests (10.5 kg m−2). The potential biodiversity was higher in some shrublands (64.1% in Mata Verde shrublands and 63.7% in mixed shrublands) and was comparable to those values found for open deciduous forests (Nothofagus antarctica forest with 60.4%). The provision of ESs presented maximum values at pure evergreen forests (56.7%) and minimum values at some shrubland types (Mata Negra Matorral thicket and mixed shrubland) and steppe grasslands (29.7–30.9%). This study has provided an accurate land cover and VT map that provides crucial information for ecological studies, biodiversity conservation, vegetation management and restoration, and regional strategic decision-making.

Combined effects of tree canopy composition, landscape location, and growing season on Nothofagus forest seeding patterns in Southern Patagonia

The ecological mechanisms that regulate seeding processes in temperate forests are poorly understood especially in the Southern Hemisphere. We studied the effect of different growing season metrics determined by the Normalized Difference Vegetation Index (NDVI) across eight annual periods between 2012 and 2020. We analyzed the seed production and biomass of two Nothofagus species in Tierra del Fuego (Argentina) to develop new tools for ecological forest management strategies. We focused on three forest types in coast and mountain landscapes: (i) pure deciduous N. pumilio, (ii) pure evergreen N. betuloides, and (iii) mixed forests with a similar proportion of both species. We performed generalized linear models for each species to analyze the influence of the growing season metrics and regional climate patterns (temperature and rainfall) considering forest types on coasts and mountains as main factors and analyzing seed production and biomass. Seed production and biomass annually varied with tree species growing at different landscape locations, with marked synchrony for each forest type, but not between different species or landscape locations (e.g. deciduous and evergreen species presented different synchrony among years). Seed production and biomass were higher when NDVI-peak was high in N. pumilio and when the growing season end was late in N. betuloides. For N. pumilio, the seed production and biomass were significantly leaded by growing season minimum temperature and growing season rainfall in coastal and mountain forests. For N. betuloides, the higher seed production and biomass were significantly influenced by non-growing season maximum temperature, growing season rainfall and non-growing season rainfall in coastal and mountain forests. These outputs highlight the importance of considering the fluctuation of the growing season in the modeling of seed production and biomass. Forest management guidelines should forecast rainy years that may benefit seedling recruitment after stand management or conservation efforts of target species (e.g. simulations of population dynamics at stand-level, decisions about passive vs active restoration in degraded forests for recover of the natural ecosystem functions).

Forest canopy-cover composition and landscape influence on bryophyte communities in Nothofagus forests of southern Patagonia.

Bryophytes (liverworts, mosses and hornworts) are one of the most diverse plant groups worldwide but one of the least studied in temperate forests from an ecological perspective. In comparison to vascular plants, bryophytes have a broader distribution and a longer altitudinal gradient, and their influence on the landscape is poorly understood. The objective was to evaluate environmental drivers that can influence bryophyte cover, richness, diversity, and nestedness in different forest canopy compositions in two typical landscapes across the natural distribution of bryophytes in Tierra del Fuego (Argentina). Three natural Nothofagus forest types (pure deciduous, pure evergreen, and mixed deciduous-evergreen) in two landscapes (coasts < 100 m.a.s.l. and mountains > 400 m.a.s.l.) were selected (N = 60 plots). In each plot, we established one transect (10 m length) to measure bryophyte cover (point-intercept method). Data were evaluated using generalized linear mixed models and multivariate analyses. The studied environmental drivers were mainly explained by the microclimate, with higher effective annual precipitation and relative air humidity in the coastal forests and higher soil moisture in the mountain forests. Greater liverwort richness was found in evergreen forests at the mountain (9 species) than at the coastal, while mosses showed higher richness in mixed deciduous-evergreen forests at the coastal (11 species) than at the mountain. However, the expected richness according to the rarefaction/extrapolation curves suggested that it is possible to record additional species, except for liverworts in pure deciduous forests on the coasts. Similarities and differences among the studied forest types and among plots of the same forest type and landscape were detected. These differences in the studied indexes (similarity that varied between 0 and 1) ranged from 0.09–0.48 for liverworts and 0.05–0.65 for mosses. Moreover, these results indicated that pure evergreen and mixed deciduous-evergreen forests presented higher moss cover (10.7% and 10.0%, respectively), mainly in the mountains than on the coast. These outputs highlight the need to explore differences at greater altitudinal ranges to achieve sustainability objectives conservation planning for bryophytes in southernmost forests.

The influence of canopy-layer composition on understory plant diversity in southern temperate forests

BackgroundUnderstory plants represents the largest component of biodiversity in most forest ecosystems and plays a key role in forest functioning. Despite their importance, the influence of overstory-layer composition on understory plant diversity is relatively poorly understood within deciduous-evergreen broadleaved mixed forests. The aim of this work was to evaluate how tree overstory-layer composition influences on understory-layer diversity in three forest types (monospecific deciduous Nothofagus pumilio (Np), monospecific evergreen Nothofagus betuloides (Nb), and mixed N. pumilio-N. betuloides (M) forests), comparing also between two geographical locations (coast and mountain) to estimate differences at landscape level.ResultsWe recorded 46 plant species: 4 ferns, 12 monocots, and 30 dicots. Canopy-layer composition influences the herb-layer structure and diversity in two different ways: while mixed forests have greater similarity to evergreen forests in the understory structural features, deciduous and mixed were similar in terms of the specific composition of plant assemblage. Deciduous pure stands were the most diverse, meanwhile evergreen stands were least diverse. Lack of exclusive species of mixed forest could represent a transition where evergreen and deciduous communities meet and integrate. Moreover, landscape has a major influence on the structure, diversity and richness of understory vegetation of pure and mixed forests likely associated to the magnitude and frequency of natural disturbances, where mountain forest not only had highest herb-layer diversity but also more exclusive species.ConclusionsOur study suggests that mixed Nothofagus forest supports coexistence of both pure deciduous and pure evergreen understory plant species and different assemblages in coastal and mountain sites. Maintaining the mixture of canopy patch types within mixed stands will be important for conserving the natural patterns of understory plant composition in southern beech mixed forests.

Flowering and seeding patterns in pure and mixed Nothofagus forests in Southern Patagonia

Variation in reproductive phenology among species is an important mechanism for maintaining species coexistence. In mixed forests, the impact of limiting (biotic and abiotic) factors on tree reproductive success regulates the maintenance of species in balanced proportions or the conversion towards monospecific forests. This study offer a significant first approach to the reproductive phenology of mixed forests, assessing flowering, seeding and loss factors on reproductive success in three forest types (pure deciduous Nothofagus pumilio (Np), evergreen Nothofagus betuloides (Nb) and mixed (M) forests), comparing also between two geographical locations (coast and mountain), during one growing season. Flowering falling started early in Np. Seed fall occurred first and more concentrated in Np, while in Nb, it was progressive during autumn. Phenology in M combined both patterns, but with better reproductive performance of both species. Seed production was greater in Nb (42,900,000 ha−1) than in Np (710,000 ha−1), while M presented intermediate values (31,900,000 ha−1). Abortion was greatest in Np (19% of female flowers and 10% of immature fruits), while fruit predation was low (7–9%) in all forest types. Empty seed was the main loss factor, but with low net values for each species in M. Regarding geographical location, sea proximity generated a quick starting of the growing season in coast compared to mountain sites. However, we detected forest types × location interactions in flowering and seeding patterns (e.g. in male flower production and in empty and viable seeds), with differences in species response according to location. Both deciduous and evergreen species have reproductive advantages in mixed compared to pure forests. However, mixed were more similar to pure evergreen forests in their reproductive traits and the incidence of the limiting factors. The study of only one growing season does not allow us to conclude whether mixed forests are stable communities, but we contribute to understand the roles of reproductive phenology in mixed forest dynamics.

The impact of juvenile tree species canopy on properties of new forest floor

To keep forest soils fertile, forest practitioners plant mixed stands that are composed of both economically efficient trees such as conifers and soil-improving broadleaves. This is a mandated practice in the Czech Republic. As the new forest grows, it creates a dense canopy. The canopy is a principal source of organic matter to the forest soil. The formation of new forest humus is particularly important in first-generation forests on the former agricultural soil. Former meadow is a suitable site for forest floor and soil investigation since forest-floor humus covering the surface of the soil is a completely new layer.&amp;nbsp; Both pure evergreen conifer and mixed treatments were planted in 2001. The experimental plot was established in order to investigate performance of tree species and restoration of forest-site conditions. We sampled dead-plant material and 0&amp;ndash;10 cm topsoil to investigate their properties under the 10-year-old stands. We compared the treatments by descriptive statistics using both univariate and multivariate techniques. Dry mass (medians of weight) varied among the treatments from 11 to 19 Mg&amp;middot;ha&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;. The forest floor nutrient concentrations appeared to be dependent on the presence of admixed deciduous tree species (sycamore maple, small-leaved linden and European larch) as these forest floors (EL1, EL2, NS3, SM) were higher in base cations and phosphorus compared to pure spruce (NS1, NS2) and pure Douglas fir (DF) treatments. The first axis of PCA ordination plot revealed 45% of total variability and showed a clear distinction between evergreen coniferous and mixed species treatments. Young plantations produced forest floors of different quality; however it was not reflected in the topsoil properties. &amp;nbsp;

Ecological behavior of Quercus suber and Quercus ilex inferred by topographic wetness index (TWI)

The ecological behaviors of a network of pure evergreen oak stands (Quercus suber L. and Quercus ilex L.) in the Central-Western Mediterranean Basin were investigated toward climatic and edaphic factors implemented with the application of topographic wetness index (TWI). A Categorical Principal Component Analysis (Catpca) using climatic and soil physico-chemical parameters was performed on 23 cork oak and holm oak pure stands with the aim to understand better the effectiveness of TWI for characterizing soil ecology of the two species. Catpca pointed out that, although cork oak and holm oak are able to growth in similar Mediterranean conditions, they show different behaviors in terms of needs and tolerance to soil water content. TWI confirmed such results at local scale, allowing highlighting some interesting features of the species differential ecology. Although both species confirmed to be drought-tolerant, the heliophilous cork oak revealed to dominate the landscape on wettest soils with high TWI values—indicating the capacity to tolerate stresses due to periods of waterlogging—, while the shade-tolerant holm oak prevails for low-medium TWI values—drier and mesophilous sites. Despite the application of TWI to vegetation science and ecology is relatively recent, results are encouraging and suggest considering this user-friendly and synthetic index in ecological investigations and modeling.

Basal rates of soil respiration are correlated with photosynthesis in a mixed temperate forest

AbstractMany field studies have demonstrated that soil temperature explains most of the temporal variation in soil respiration (SR). However, there is increasing evidence to suggest that SR is also influenced by current, or recent, photosynthate. Accordingly, seasonal changes in SR nominally attributed to temperature may, in part, be due to seasonality in photosynthesis. Within a mixed coniferous–deciduous temperate forest, we measured SR and used the process model SECRETS to test whether seasonal changes in photosynthesis influence seasonal differences in SR. Measurements were made in six adjacent plots (from pure evergreen to pure deciduous) that exhibited a gradient in the seasonality of photosynthesis. Within all six plots, we found strong correlations between the basal rate of SR (BR; defined as the SR at 10°C) and modeled photosynthesis (i.e. gross primary productivity; GPP). Moreover, we observed larger seasonal changes in BR in those plots that exhibited larger seasonal changes in photosynthesis, as compared with plots with smaller changes in photosynthesis. This is relevant because estimates of the Q10 of SR (Q10 is the relative change in a process rate per temperature change of 10°C) typically assume a constant BR. Our results therefore support the hypothesis that differences in the apparent Q10 of SR (apparent Q10=Q10 derived from field measurements of SR and temperature) among studies may, in large part, be related to seasonal differences in photosynthesis. We suggest that variation in stand structure and species composition and, thus, in the photosynthetic signatures, induce different seasonal changes in BR via differences in the belowground supply of labile carbon. If these seasonal changes in BR are not properly accounted for, fitted apparent Q10 values may not express the temperature response of respiratory processes in the soil.

Annual Q10 of soil respiration reflects plant phenological patterns as well as temperature sensitivity

AbstractThe temperature sensitivity of soil respiration (SR) is often estimated from the seasonal changes in the flux relative to those in soil temperature, and subsequently used in models to interpolate or predict soil fluxes. However, temperature sensitivities derived from seasonal changes in SR (from here on denoted seasonal Q10) may not solely reflect the temperature sensitivity of SR, because seasonal changes in SR can also be affected by other seasonally fluctuating conditions and processes. In this manuscript, we present a case study of how the seasonal Q10 of SR can be decoupled from the temperature sensitivity of SR. In a mixed temperate forest, we measured SR under vegetations with different leaf strategies: pure evergreen, pure deciduous, and mixed. Seasonal Q10 was much higher under deciduous than under evergreen canopies. However, at a shorter time scale, both vegetation types exhibited very similar Q10 values, indicating that the large differences in seasonal Q10 do not represent differences in the temperature sensitivity of the soil metabolism. The seasonal Q10 depends strongly on the amplitude of the seasonal changes in SR (SRs), which, under the particular climatic and edaphic conditions of our forest study site, were significantly larger in deciduous forest. In turn, SRs was positively correlated with the seasonal changes in leaf area index (LAIs), a measure of the deciduousness of the vegetation. Thus, in this temperate maritime forest, seasonal Q10 of SR was strongly influenced by the deciduousness of the vegetation. We conclude that the large differences in seasonal Q10 were not entirely due to different temperature sensitivities, but also to different seasonal patterns of plant activity in the evergreen and deciduous plants of this site. Some coniferous forests may be more seasonal than the one we studied, and the deciduous–evergreen differences observed here may not be broadly applicable, but this case study demonstrates that variation of plant phenological process can significantly contribute to the seasonality of SR, and, hence, calculated Q10 values. Where this occurs, the seasonal Q10 value for SR does not accurately represent temperature sensitivity. Because the strong seasonal correlation between SR and temperature does not necessarily imply a causal relationship, Q10 values derived form annual patterns of SR should be used with caution when predicting future responses of SR to climatic change.

A study of Paridae community in Japan

1. Censuses of Japanese tits were made intensively at Tenryu River basin ca. 500m of altitude (102 times, 1957-'60) and Keito Mt. region below 1000m (95 times, 1963-'65), in Nagano Prefecture, Central Honshu. Supplemental censuses were made at: lowland Hokkaido (Sarobetsu, Kawayu, Gojukkoku and Onuma), subalpine Central Honshu (Kamikochi, Shiga), Shikoku (Kurokawa), Kyushu (Mt. Hiko, Ishiwara) and Tsushima (four places). These places had different vegetational environment and species composition of tits, but they were absent in pure evergreen broadleaved woods of southern Japan.2. The species of tits studied are: Aegithalos caudatus (Aegithalinae), Parus major, P. ater, P. varies, P. montanus and P. palustris (Parinae).3. At peripheral parts (Tenryu, Kurokawa, Ishiwara) of Paridae habitat of simple woods around human habitation, P. major and Ae. caudatus were main species; and only the former was found at the extreme periphery. P. varius joined them if there was a good amount of broad-leaved desiduous woods; P. ater occurred as a main member only during winter in Central Honshu where there was a mixed forest (Keito region); the main members were replaced in summer by P. ater and P. montanus at wet subalpine mixed forest (Kamikochi, Shiga); while in swampy lowland broadleaved forests of Hokkaido (Kawayu, Onuma, Gojukkoku), Ae. caudatus, P. major and P. palustris formed the main members, the last species becoming dominant in the more swampy part. P. varius and P. montanus occurred always in small numbers, but they may be more plentiful (dominate the others) elsewhere where they are best adapted respectively.4. The following three types of sympatry and ecological segregation among tits could be concluded:a. Two main species may coexist in similar abundance, but their types of social population fluctuation is different: Ae. caudatus concentrates into a compound family flock after breeding, while in P. major families are become dispersed. Thus, the two abundant species can coexist at peripheral areas.b. Two species may coexist in similar numbers and show parallel seasonal fluctuations, but the degree of fluctuation is different: Fluctuations of P. major and P. ater at Keito area were parallel but the wintering population of the latter species greatly increased, becoming very scarce in breeding season.c. One of the coexisting two species may dominate the other in number: P. montanus and P. varius in studied areas were decidedly few in number, although they coexisted with P. major and fluctuated parallel with it.5. Ae. caudatus is different from Parus species in the type of social population fluctuation and thus can be sympatric at such a peripheral part where P. major is abundant. Other Parus species may be similar in social fluctuation type, but coexist with each other by their different degrees of abundance in species composition due to different habitat preference or particular seasonal movement. P. montanus and P. varius, for example, are entirely allopatric in habitat, while P. ater is partly and seasonally sympatric with P. major and others.