Natural Forest Sites Research Articles

Development of Polymorphic Index Model for Assessing Subtropical Secondary Natural Oak Forest Site Quality Under Complex Site and Climate Variables

Site and climate conditions are the key determinants controlling dominant height growth and forest productivity, both independently and interactively. Secondary natural oak forests are a typical forest type in China, especially in Hunan Province, but little is known about the site index of this forest under the complex site and climate variables in the subtropics. Based on survey data of dominant trees and site variables from 101 plots in Hunan oak natural secondary forests and climate data obtained using spatial interpolation, we used the random forest method, correlation analysis, and the analysis of variance to determine the main site and climate factors affecting oak forest dominant height and proposed a modeling method of an oak natural secondary forest site index based on the random effect of site–climate interaction type. Of the site variables, elevation affected stand dominant height the most, followed by slope direction and position. Winter precipitation and summer mean maximum temperature had the greatest impact on stand dominant height. To develop the modeling method, we created 10 popular base models but found low performance (R2 ranged from 0.1731 to 0.2030). The optimal base model was Mitscherlich form M3 (R2 = 0.1940) based on parameter significance tests. Since site and climate factors affect the site index curve, the dominant site and climate factors were combined into site types and climate types, respectively, and a nonlinear mixed-effects approach was used to simulate different site types, climate types, site–climate interaction types, and their combinations as random effects. Site–climate interaction type as a random factor enhanced model (M3.4) performance and prediction accuracy (R2 from 0.1940 to 0.8220) compared to the optimum base model. After clustering the 62 site–climate interaction types into three, five, and eight groups using hierarchical clustering, a mixed-effects model with the random effects of eight groups improved model performance (R2 = 0.8265) and applicability. The modeling method developed in this study could be used to assess a regional secondary natural oak forest site index under complex site and climate variables to evaluate the forest productivity.

Features of Consistent Powassan Virus Lineage II Focus in Southern Maine, United States.

Powassan virus lineage II or deer tick virus (DTV) is a rare but increasingly reported human infection in the United States transmitted by Ixodes scapularis ticks. The virus is thought to be maintained in environmental foci that are optimal for tick and vertebrate reservoirs, but details on DTV ecology are poorly understood. We investigated DTV tick infection rates and reservoir host abundance in a focus of consistent DTV activity in Maine, USA. Host and tick abundance, vegetation, and microclimate conditions were measured in three forest sites representing increasing invasive understory infestation. Sites were selected representing native understory, mixed vegetation with some invasive Japanese barberry (Berberis thunbergii), and a highly invasive site dominated by Japanese barberry. Japanese barberry in the mixed vegetation site averaged 1 m in height with space between plants, whereas the highly invasive site had impenetrable Japanese barberry over 1.5 m. The DTV infection rate was greater in the highly invasive site. Density of I. scapularis ticks were significantly lower in the native forest site, and no DTV was found. Another feature of the DTV focus was more stable humid microclimate throughout the year compared with the other sites and a nearby continuous section of forest, consistent with reports from Connecticut, USA. We conclude that invasive Japanese barberry stands provide favorable and consistent microclimate conditions to maintain high DTV infection rates annually among questing I. scapularis ticks. Understanding environmental and landscape features that support high infection rates could lead to the identification of high-risk habitats for contracting DTV.

Changes in soil organic carbon in native forests of Argentina related to land use change and environmental factors

AbstractNative forests host important pools of soil organic carbon (SOC). This is a key element not only for ecosystem functioning but also for the global carbon cycle. Globally, and particularly in Argentina, native forests are being rapidly replaced by other land uses, raising questions about the impact of these transformations on SOC and its environmental controls. Based on the construction of the largest SOC database in Argentina to date, we investigated the patterns and controls of changes in SOC stocks associated with the replacement of native forests by other land uses. We constructed the database with a total of 818 sites with SOC data (0–30 cm depth), covering the main ecoregions, to which we added environmental information (e.g. satellite data, soil database and climate database), to study the environmental controls on SOC change after deforestation and on the original SOC content of native forests. Considering all ecoregions and all land use alternatives together, we found an average decrease in SOC stock of 18.2 Mg C ha−1, which represents a loss of more than a quarter of the original SOC stock of the native forest sites. A boosted regression tree explained 89% of the variation in SOC stock change and indicated that the initial forest SOC stock and the post‐deforestation land use were the most important variables explaining this variation (relative influence of 30.9% and 18.2%, respectively). The replacement of native forests by rainfed annual crops resulted in the largest decrease in SOC (−28 Mg C ha−1), which was twice as large as the decrease observed in rangelands (−14 Mg C ha−1). On the contrary, neither irrigated croplands nor tree plantations of fast‐growing species caused a decrease in SOC stocks (p > .10). Climate and soil texture had an indirect effect on SOC changes through a strong influence on the initial SOC stocks in native forests (p < .01). Our study highlighted the significant impact of land use change on SOC stocks, overshadowing other relevant environmental controls. Understanding how the SOC pool responds to land use change, environmental conditions and management practices is essential to increase the effectiveness of practices implemented to improve soil properties and mitigate climate change.

THE REMEDIATION METHOD AS A FACTOR SHAPING THE PIGMENT PROFILE OF SCOTS PINE ON TECHNOGENIC LAND

Background. It is important to study how the remediation method influences the formation of the pigment complex in Scots pine, Pinus sylvestris L., growing on technogenic land. Thorough understanding of the influence produced by a heterogeneous environment on the content and distribution of pigments in conifers enables us to study the adaptive mechanisms of the species more comprehensively. In turn, information about these mechanisms can be used to create new methods for improving the quality and stability of tree stands. Purpose. The study was designed to explore the effect of the remediation method on the pigment complex forming in Scots pine during a post-technogenic succession in southern Karelia. Material and methods. Surveys were carried out in adjacent sample plots located in a decommissioned sand-and-gravel quarry and in a natural lingonberry-type pine forest site in July 2021 and 2022. The study objects were Scots pine trees growing in a natural forest site and in quarry sites remediated by forest planting. The optical density of the solutions was determined using SF-2000 spectrophotometer. Statistical data processing was done using Statistica 10 software (StatSoft Inc., USA). Results. During the two years of the study, the pigment content was the highest in needles of the trees growing on more fertile soils compared to those on poor man-made soils. The of Cl a /Cl b ratio in the needles of trees growing on poor soil was higher than in the fertilized area of the quarry or in the natural forest site in both years of the study, indicating that the plants’ pigment complex adapted to the unfavorable environmental conditions by increasing the proportion of Cl a among green pigments. Conclusions. The findings prove that the remediation method has a significant shaping effect on the pigment profile of Scots pine during post-technogenic successions.

Aridity affects soil organic carbon concentration and chemical stability by different forest types and soil processes across Chinese natural forests

Forest soils play a critical role in carbon (C) reservoirs and climate change mitigation globally. Exploring the driving factors of soil organic carbon (SOC) concentration and stability in forests on a large spatial scale can help us evaluate the role of forest soils in regulating C sequestration. Based on SOC quantification and solid-state 13C nuclear magnetic resonance spectroscopy, we investigated the SOC concentration and SOC chemical stability (indicated by alkyl-to-O-alkyl ratio and hydrophobic-to-hydrophilic ratio) in top 0–5 and 5–10 cm soils from 65 Chinese natural forest sites and explored their driving factors. Results showed that SOC concentration in 0–5 cm soils were highest in mixed forests but SOC chemical stability in 0–5 cm soils were highest in coniferous forests, while SOC concentration and chemical stability in 5–10 cm soil layers did not differ across forest types. SOC concentration in 0–5 cm was directly related to soil pH and soil bacterial diversity. Structural equation models showed that aridity indirectly affected SOC concentration in 0–5 cm by directly affecting soil pH. While SOC chemical stability in 0–5 cm soils was higher with increased aridity. According to the correlations, the potential mechanisms could be attributed to higher proportion of coniferous forests in more arid forest sites, lower relative abundance of O-alkyl C, higher MgO and CaO contents, and higher bacterial diversity in soils from more arid forest sites. Our study reveals the important role of aridity in mediating SOC concentration and chemical stability in top 0–5 cm soils in Chinese natural forests on a large-scale field investigation. These results will help us better understand the different mechanisms underlying SOC concentration and stability in forests and assess the feedback of forest SOC to future climate change.

Linking phosphorus fertility to soil microbial diversity and network complexity in citrus orchards: Implications for sustainable agriculture

Continuous input of chemical fertilizers causes soil acidification, land degradation, and water eutrophication, but its impact on soil microbial communities and co-occurrence patterns of microboes is unclear. In this study, we evaluated the impact of chemical fertilizer on bacterial community diversity and ecological network at 75 citrus sites in a watershed where chemical fertilizer is continuously applied. In addition, 25 natural forest sites adjacent to citrus sites were used as references to compare the potential effects of land conversion from natural forests to citrus orchards on soil bacterial diversity and microbial network. The results showed that the cultivation of citrus results in soil phosphorus (P) accumulation, with significantly higher available and mineral-bound phosphate contents than those found in soils of natural forests. Citrus soil average soil available P was 73.2 mg/kg, which was 20 times higher than that in forest soils. As the P content accumulates, soil bacterial Shannon index linearly decreases from 7.06 to 5.93 and is significantly lower than that of adjacent natural forest soils (7.13). Low P fertility soils have higher microbial network complexity and stability, containing more microbial communities and tighter relationships between microbes compared to higher P fertility soils. Soil P content and soil pH regulates soil microbial network complexity and stability. In addition, soil bacterial community structure in soils of natural forests is significantly different from that in citrus soils, and the bacterial community structure in high P soils is different from that in medium and low P soils. Soil P fertility reduces the relative abundance of dominant communities including Proteobacteria, Bacteroidetes, and Gemmatimonadetes, and also changes the relative abundance of some functional microbial communities, such as some phosphorus cycling microorganisms, including Acetobacteraceae and Beijerinckiaceae. In conclusion, soil phosphate accumulation severely alters soil bacterial community diversity, complexity, stability, and functionality. This could have negative impacts on soil functional stability and the sustainability of citrus orchards.

Soil mycobiomes in native European aspen forests and hybrid aspen plantations have a similar fungal richness but different compositions, mainly driven by edaphic and floristic factors.

The cultivation of short-rotation tree species on non-forest land is increasing due to the growing demand for woody biomass for the future bioeconomy and to mitigate climate change impacts. However, forest plantations are often seen as a trade-off between climate benefits and low biodiversity. The diversity and composition of soil fungal biota in plantations of hybrid aspen, one of the most planted tree species for short-rotation forestry in Northern Europe, are poorly studied. The goal of this study was to obtain baseline knowledge about the soil fungal biota and the edaphic, floristic and management factors that drive fungal richness and communities in 18-year-old hybrid aspen plantations on former agricultural soils and compare the fungal biota with those of European aspen stands on native forest land in a 130-year chronosequence. Sites were categorized as hybrid aspen (17-18-year-old plantations) and native aspen stands of three age classes (8-29, 30-55, and 65-131-year-old stands). High-throughput sequencing was applied to soil samples to investigate fungal diversity and assemblages. Native aspen forests showed a higher ectomycorrhizal (EcM) fungal OTU richness than plantations, regardless of forest age. Short-distance type EcM genera dominated in both plantations and forests. The richness of saprotrophic fungi was similar between native forest and plantation sites and was highest in the middle-aged class (30-55-year-old stands) in the native aspen stands. The fungal communities of native forests and plantations were significantly different. Community composition varied more, and the natural forest sites were more diverse than the relatively homogeneous plantations. Soil pH was the best explanatory variable to describe soil fungal communities in hybrid aspen stands. Soil fungal community composition did not show any clear patterns between the age classes of native aspen stands. We conclude that edaphic factors are more important in describing fungal communities in both native aspen forest sites and hybrid aspen plantation sites than forest thinning, age, or former land use for plantations. Although first-generation hybrid aspen plantations and native forests are similar in overall fungal diversity, their taxonomic and functional composition is strikingly different. Therefore, hybrid aspen plantations can be used to reduce felling pressure on native forests; however, our knowledge is still insufficient to conclude that plantations could replace native aspen forests from the soil biodiversity perspective.

Quantifying the Threshold Effects and Factors Impacting Physiological Health Benefits of Forest Exposure

The growing awareness of the health advantages offered by forests has underscored the significance of forest exposure as an upstream preventive measure against disease. While numerous studies have confirmed the physical and mental health benefits associated with forests, there is still a lack of quantitative understanding regarding the relationship between forest exposure and physiological health benefits (PHB). Particularly, there is insufficient knowledge about the threshold effects derived from short-term forest exposure. In this study, we propose a PHB threshold model for assessing forest exposure that introduces the concepts of efficiency threshold and benefits threshold. A pilot study was conducted in three typical natural forest sites to validate the proposed model. Electroencephalogram (EEG) was continuously measured as the physiological indicator, while meteorological, environmental, and demographic factors were simultaneously collected. The results show that: (1) the proposed PHB threshold model is applicable in a natural forest environment; (2) despite the longer time required to reach the PHB thresholds, forest exposure yielded more significant and prolonged health benefits compared to urban green spaces; (3) meteorological factors, such as temperature and relative humidity, play a crucial role in impacting the PHB threshold model; and (4) exposure to forests is better for deep thinking and relaxation than urban green spaces. These findings emphasize the potential of forests to offer a respite from the stresses of modern life and promote holistic well-being.

Ecological filtering shapes the impacts of agricultural deforestation on biodiversity.

The biodiversity impacts of agricultural deforestation vary widely across regions. Previous efforts to explain this variation have focused exclusively on the landscape features and management regimes of agricultural systems, neglecting the potentially critical role of ecological filtering in shaping deforestation tolerance of extant species assemblages at large geographical scales via selection for functional traits. Here we provide a large-scale test of this role using a global database of species abundance ratios between matched agricultural and native forest sites that comprises 71 avian assemblages reported in 44 primary studies, and a companion database of 10 functional traits for all 2,647 species involved. Using meta-analytic, phylogenetic and multivariate methods, we show that beyond agricultural features, filtering by the extent of natural environmental variability and the severity of historical anthropogenic deforestation shapes the varying deforestation impacts across species assemblages. For assemblages under greater environmental variability-proxied by drier and more seasonal climates under a greater disturbance regime-and longer deforestation histories, filtering has attenuated the negative impacts of current deforestation by selecting for functional traits linked to stronger deforestation tolerance. Our study provides a previously largely missing piece of knowledge in understanding and managing the biodiversity consequences of deforestation by agricultural deforestation.

Variation in pollen load composition carried by wild bee species in native and nearby agricultural environments in south‐eastern Australia

Abstract Understanding the mechanisms by which wild bees survive in modified landscapes is important for their conservation and management as pollinators. Pollen is a critical resource for the completion of bee life cycles, so we investigated how the pollen loads carried by native bee communities change between natural forests and farms dominated by exotic crops and weeds in an agricultural region of south‐east Australia. We found that individual bees tended to carry higher proportions of exotic pollen on farms compared with forests (after accounting for whether they were captured on exotic or native flowers), and the diversity of pollen carried by bees did not differ significantly between native forest and farm sites or along native forest cover gradients. This suggests that the native bees found on farms, which are predominantly different species compared with those found in native forests, are not disadvantaged by the dominance of exotic plants in these habitats (though impacts on larval nutrition were not investigated). While some native bees carried crop pollen, others almost exclusively carried the pollen of agricultural weeds (e.g., Arctotheca and Brassica species), such that some native bee species may pollinate and benefit from crops, whereas others may only persist on farms if agricultural weeds are tolerated.

Comparison of soil quality assessment methods for different vegetation eco-restoration techniques at engineering disturbed areas.

Scientific assessment of soil quality is the foundation of sustainable vegetation eco-restoration in engineering disturbed areas. This study aimed to find a qualitative and comprehensive method for assessing soil quality after vegetation eco-restoration in engineering disturbed areas. Sixteen soil indicators were used at six vegetation eco-restoration sites as the potential soil indicators. A minimum data set (MDS) and revised minimum data set (RMDS) were determined by principal component analysis. Six soil quality indices (SQIs) of varying scoring functions based on different data sets were employed in this study. Significant positive correlations were observed among all six SQIs, indicating that the effects of different vegetation eco-restoration measures on soil quality could be quantified by all six SQIs. The SQI values of the vegetation concrete eco-restoration slope (VC), frame beam filling soil slope (FB), thick layer base material spraying slope (TB), and external-soil spray seeding slope (SS) were all significantly higher than the SQI value of the abandoned slag slope (AS). It is noteworthy that the SQIs of the VC and TB sites were also significantly higher than the SQI of the natural forest (NF) site. These results indicate that the application of artificial remediation measures can significantly improve the soil quality of the disturbed area at the Xiangjiaba hydropower station. The results of this study also indicate that the SQI-NLRM method is a practical and accurate quantitative tool for soil quality assessment and is recommended for evaluating soil quality under various vegetation eco-restoration techniques in disturbance areas at the Xiangjiaba hydropower station and in other areas with similar habitat characteristics.

Response of the soil microbial communities to forest ground cover manipulation in a boreal forest

In eastern Canada, boreal forests are locally experiencing a shift between two alternative stable states, productive closed-canopy feather moss (Pleurozium schreberi (Brid.) Mitt.) forests to low-productivity open lichen (Cladonia spp.) woodlands. While this shift has important consequences for ecosystem structure and productivity, little is known about the changes occurring in the diversity and composition of the soil microbial community which may be driven by this process. We evaluated the effects of 10-year moss transplantation on soil microbial communities in an open-lichen woodland. Treatments included: 1) removal of the lichen cover, 2) removal of the lichen cover followed by transplantation of a feather moss cover, 3) a control with the lichen cover kept in place (lichen control), and 4) a natural forest site with a feather moss cover (moss control). We found that changing the forest ground cover has a significant impact on the diversity, composition and function of soil microbial communities. Fungal alpha diversity was more sensitive to changes in lichen and moss cover, compared to bacterial diversity. Soil microbial community composition showed significant differences among all forest ground covers, but with greater similarities between the moss transplantation and control moss treatments. More importantly, changes of forest ground cover significantly affected the structure of microbial communities and fungal functional groups. Moss transplantation significantly increased the relative abundance of the organic nitrogen-scavenging fungal genus, Piloderma. Furthermore, moss transplantation significantly increased the overall relative abundance of ectomycorrhizal fungi and decreased the proportion of ericoid mycorrhizal fungi. Soil moisture and temperature were the main environmental variables associated to the shift in microbial community composition. Our study points out that moss transplantation in open-canopy lichen woodlands contributes to regulate and modify the composition, structure, and function of the soil microbial communities with potential implications for explaining the changes in ecosystem processes associated with these two forest ecosystems.

Impacts of land use change on native plant-butterfly interaction networks from central Mexico.

Land use change is a key catalyst of global biodiversity loss and ecosystem degradation. Deforestation and conversion of natural habitats to agricultural or urban areas can profoundly disrupt plant-flower visitor interactions by altering their abundances and distribution. Yet, specific studies analyzing the effects of land use change on the structure of networks of the interactions between particular groups of flower visitors and their plants are still scarce. Here, we aimed to analyze how converting native habitats affects the species composition of butterfly communities and their plants, and whether this, in turn, leads to changes in the structure of interaction networks in the modified habitats. We performed bi-monthly censuses for a year to record plant-butterfly interactions and assess species diversity across three habitat types, reflecting a land-use change gradient. From original native juniper forest to urban and agricultural zones in central Mexico, one site per land use type was surveyed. Interactions were summarized in matrices on which we calculated network descriptors: connectance, nestedness and modularity. We found highest butterfly diversity in native forest, with the most unique species (i.e., species not shared with the other two sites). Agricultural and urban sites had similar diversity, yet the urban site featured more unique species. The plant species richness was highest in the urban site, and the native forest site had the lowest plant species richness, with most of the plants being unique to this site. Butterfly and plant compositions contrasted most between native forest and modified sites. Network analysis showed differences between sites in the mean number of links and interactions. The urban network surpassed agriculture and native forest networks in links, while the native forest network had more interactions than the agriculture and urban networks. Native plants had more interactions than alien species. All networks exhibited low connectance and significant nestedness and modularity, with the urban network featuring the most modules (i.e., 10 modules). Converting native habitats to urban or agricultural areas reshapes species composition, diversity and interaction network structure for butterfly communities and plants. The urban network showed more links and modules, suggesting intricate urban ecosystems due to diverse species, enhanced resources, and ecological niches encouraging interactions and coexistence. These findings emphasize the impacts of land use change on plant-butterfly interactions and the structure of their interaction networks.

Nutritional Status of Wood Melick (Melica uniflora Retz.) in a Natural Forest Stand in South-Western Poland

Melica uniflora Retz., commonly known as wood melick, is a grass species that is native to most of Europe. Melica uniflora grows in hardwood forests near Fagus species, providing vital food and shelter for forest wildlife. The nutritional status of wood melick is not sufficiently recognized. The study aims to identify the intrapopulation variability of Melica uniflora plants collected from natural forest habitats in Poland in terms of nutritional status variability in relation to stage development and the course of weather conditions. The research was conducted for two consecutive years: 2021 and 2022, in the area of the Ślęża Massif, near the town of Sobótka in Lower Silesia voivodeship (Poland). The material for analyses was collected from 10 natural forest sites twice: in July (I) and October (II). The content of nutritive components: crude protein (CP), crude ash (CA), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), and water-soluble carbohydrates (WSC) was evaluated. Relative feed value (RFV), dry matter digestibility (DDM), dry matter intake (DMI), cellulose (CL), and hemicellulose (HCL) content were calculated based on ADF and NDF. Melica uniflora plants contained 75.2 g·kg−1 DM of CP, 290.6 g·kg−1 DM of CF, 120.0 g·kg−1 DM of CA, and 25.9 g·kg−1 DM of WSC. The content of NDF was 637.6 g·kg−1 DM, ADF 407.5 g·kg−1 DM, and ADL 58.0 g·kg−1 DM. The nutritional status of wood melick depended on the course of weather conditions in the following years and its location, which changed during the growing season. Plants collected in the first year of the study contained more CL, NDF, and ADF fractions and less CA, ADL, and WSC. Melica uniflora plants harvested in June were characterized by higher CP (102.1 g·kg−1 DM) and WSC (30.1 g·kg−1 DM) content and lower content of remaining nutrients. It can be concluded that Melica uniflora plants can be a valuable source of these nutrients in the forage of forest animals.

Maintaining the protective function of mountain forests under climate change by the concept of naturalness in tree species composition

In Swiss mountain areas, the protective function of forests is the predominant ecosystem service having high cultural and economic significance. It is assumed that natural forests or close-to-natural forests, i.e., forests being in the equilibrium with environmental conditions are the most resilient and resistant in regard to disturbances and hence best protecting people and assets on the long run. Here, we estimated the naturalness of the tree species composition by comparing Swiss National Forest Inventory (NFI) data with current and future potential Natural forest Site Types (NST). Based on this analysis, we identified species that are under or over-represented in protective mountain forests and derived the subsequent potential for management interventions. The urgency of management interventions is expected be small if all predominant tree species of the idealized potential natural forests are present and only their relative portions in the stand need adjustment. In contrast, interventions are advisable, if predominant tree species of the current and future potential natural forests are absent. Based on NFI data, the tree species composition of 47% of the protective mountain forests were classified as “natural” or “close-to-natural,” while the remaining 53% were classified as “not natural” or “partly natural.” Norway spruce [Picea abies (L.) H. Karst.] and European larch (Larix decidua Mill.) were the two most over-represented species under current and even more so under predicted future climatic conditions. To date, silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) were the two species most frequently absent in protective mountain forests, in which they should prevail. Apart from European beech, the most prominent increase in prevalence is predicted for oak (sessile oak and pubescent oak; Quercus petrea Liebl., Q. pubescens Willd.) and small-leaved lime (Tilia cordata Mill.). These species were currently missing from more than 75% of the stands, in which they are expected to be dominant under future conditions. Our analysis indicates the need to transform tree species compositions of protective mountain forests to optimize fitness under future climates. Some of these transformations will take place naturally, incited by disturbances, others—the majority of them—will need active management interventions.

Aggregation Stability and Carbon Pools in Extremely Kaolinitic Soils from the East Coast of Brazil as Affected by Land Use Changes

The aim of this study was to evaluate the differential response to land use changes between native forest and croplands regarding the quantitative soil variables of aggregate weight classes and different carbon pools in extremely kaolinitic soils from the east coast of Brazil. In the soil A horizon, the total (TOC) and dissolved (DOC) organic carbon contents were analyzed. In the 0–0.08 m soil layer, the weight and the organic carbon content (Cag) were determined for six size aggregate classes. The mean differential (Δ) of each property for each area was calculated. Overall, the TOC and DOC were greater in the native forest sites over the counterpart cultivated sites within each area. The ΔDOC of all the five areas were negative. The ΔCag of the 1–2 mm and 0.053–0.105 mm soil aggregate classes of Sooretama were the only ones with mean positive values. The ordination of the five areas by the ΔCag in the six soil aggregate size classes isolated Coruripe as the area with the most negative differentials, because of the forest conservation and management of the cropland. The differentials of organic carbon between forest and agricultural use of the analyzed properties did not reveal a possible effect of soil texture.

Interaction of site, spacing, weed control and fertiliser in Pinus radiata plantations in southeast New South Wales

ABSTRACT Two trials addressing soil preparation, weed control, fertiliser application and planting density were established on dry, high-elevation sites as part of a program to develop site-specific management. The sites differed in soils and the level of pasture improvement. The objectives included identifying treatment combinations that had greatest productivity and best stem and branch form, considering that poor stem form is an issue on pasture sites. The trials were assessed at 13 years of age. Volume production was high compared with a plantation established earlier on a native forest site, but it was not possible to determine whether this was a result of higher survival, higher nutrition, improved weed control or improved genetics. There was little difference in the effects of soil preparation treatments, and there was no effect at 13 years of the small early-fertiliser application. Weed control was important, with effects on volume production varying between sites and having a greater effect on the highly improved pasture site. Increasing stocking from 1000 stems ha−1 to 1500 stems ha−1 increased volume production by about 24% where weed control was applied. There were differences in stem and branch form between sites, and the highly improved pasture site had a higher level of multi-leaders, probably attributable to low boron. The study shows the value of small, standardised silvicultural trials in the development of site-specific management.

Assessment of Litter Input, Decomposition and Elements Dynamics in Yatta Tropical Forest in Western Equatoria State, South Sudan

This study characterized soils, assessed litter input, litter decomposition and elements release in Yatta forest, Western Equatoria State, South Sudan during May 2008 and March 2010. The soil was described and sampled. Litter was collected weekly from plots of 16 m2 under the forest cover with forty replicates. Seventy five litter bags were buried at 15-30 cm soil depth to assess decomposition and elements' release. Twenty fife bags were withdrawn at every 6, 12 months periods Fallen litter, remaining decomposed litter and soil samples were analyzed in the Laboratory of the Department of Soil and Environment Sciences, Faculty of Agriculture, University of Khartoum. The soil was characterized as Oxisols, sandy clay loam, acidic, rich in organic matter, and amply furnished with nutrients. Litter input was 1791 kg/ha/year; with concessive seasonal maxima and minima in dry and wet months. Losses of dry matter were high, ranging of 52.2 % to 96.8 % during the tested periods. The elements K, N, P, Ca, Mg were rapidly released with successive rates ranges of 37 %-62 %, 56 %-72 % and 62 %-90 % during 6, 12 and 18 months observation periods. The results showed a high potential fertility of this natural forest site which will support the sustainability of the growing stock and utilization of the forest for high yielding food crops.

Bird abundance and diversity in shade coffee and natural forest in Kenya

Coffee, one of the major traded commodities in the world, has economic value for rural livelihood and potentially as habitat for forest wildlife. Previous work in Central Kenya has demonstrated that when cultivated with shade trees, coffee farms can host high levels of bird diversity. However, questions of how the African bird communities in shade coffee farms compares to those in natural forest remained unanswered. Using three visits to each of 160-point count locations in natural forest (80) and shade coffee sites (80) in Central Kenya, we estimated bird abundance and species richness in natural forest and shade coffee. Specifically, we tested hypotheses that the abundance and diversity of birds in shade-coffee and natural forests varies by feeding guilds and forest-association status. We found that, compared to natural forest, shade coffee had higher bird abundance and species richness of carnivores, granivores, omnivores, and insectivores, including understory forest insectivores specifically. Frugivores and nectivores had similar abundance in forest and coffee, but were more species rich in forest and coffee, respectively. The abundance and species richness of forest specialists and forest visitors were higher in natural forest than in shade coffee, whereas forest generalists and birds with no forest association status were more abundant and species rich in shade coffee. Our study confirms the value of remnant native trees within coffee plantations for the persistence and conservation of avian communities, while also clarifying that some groups of birds are reliant on natural forests and unlikely to be conserved in shade coffee farms.

How do assemblages of epigeal Araneae and Coleoptera respond to changes in habitat structure caused by sugar cane crops in Northern Argentina?

ABSTRACT In Northwest Argentina, nothing is known about the relationship of Araneae and Coleoptera with sugar cane crops. Using pitfall traps in three continuous native forest sites (N) and three native forest windbreaks surrounded by sugar cane crops (W) in the province of Salta, we assessed a)- whether the native diversity of epigeal Araneae and Coleoptera in the Chaco Serrano forest changes as a result of the fragmentation of the habitat caused by the sugar cane plots, and b)- whether the diversity of predatory species increases in native forest windbreaks as a consequence of the contribution of species that come from crops. In the spring of 2006 and the summer of 2007, we collected 599 Araneae and 555 Coleoptera, with community W (S = 132, N = 535) containing much more species but fewer individuals than community N (S = 111, N = 619). We found that the spatial and phenological patterns of the alpha and beta diversities of N were altered in W communities. Thus, habitat fragmentation generated by sugar cane plots led to the local extinction of native Araneae and Coleoptera species. The abundance of generalist Araneae and herbivorous Coleoptera increased in W habitats, but the coprophagous and detritivorous beetles decreased. The diversity of predatory species (Araneae and some Coleoptera) increased in W habitats, although their abundance declined relative to N habitats. Species turnover determined beta diversity between N and W sites; however, between the W sites, nestedness increased and spiders showed a greater loss of species. The spatial heterogeneity between sites, seasons, and habitats had a substantial effect on the composition of the Araneae and Coleoptera assemblages, hence influencing regional diversity. Eight species were habitat indicators, particularly Leprolochus birabeni (Zodariidae), which responds unfavourably to perturbations in the agricultural landscape, and could be deployed as environmental monitors in the Chaco Serrano.