Forest Layer Research Articles

Impact of Land use Changes on Landslides Occurrence in Urban Area: The Case of the Constantine City (NE Algeria)

The city of Constantine (NE Algeria), the third largest city of the country (2.374 inhabitants/km2) is facing frequent damaging landslides that constitute a constraint to future development and land use planning. The main goals of this study are to evaluate the effect of land use changes on the spatial distribution of landslide hazard occurrence and give an example of landslide hazard assessment as useful tool within the context of long-term land use planning in the urban area of Constantine. For this purpose, the adopted methodology requires four steps: (i) Data collection and construction of a spatial database related to the historical landslides, land use, building and population inventory; (ii) landslide inventory and land use mapping for the period of 1970 to 2011 based on the analysis of aerial photographs, high resolution satellite images, historical records verified and completed by extensive field observations, (iii) analysis of the effects of land use changes on the spatial distribution of landslide occurrence for different periods 1970 and 2011; (iv) landslide hazard map, obtained by using the frequency ration (FR) under GIS and (v) evaluate the impact of human-induced land use changes on hazard occurrence. For that, we, firstly, compared the landslide inventory map with land use maps of different periods of 1970 and 2011 that showed that since 1970, the density of landslides increases with increasing of urban areas. In 2011, the high landslide density is concentrated on the following four layers: the urban area layer (41%), the agriculture land layer (39%), the grass area layer (15%) and the forest land layer (5%). The effect of the expansion of urban zone in agriculture, grass and pasture area have increase landslide densities over time. Secondly, we compared the landslide hazard map to these land use maps and we found that 40% of the high hazard zones and 50% of the moderate hazard zones fall in the urbanized area. The obtained results show a clear impact of the changed land use where human action is an important triggering and/or accelerating factor of landslides in the urban area of Constantine. Nowadays, about 72,749 inhabitants and 25,255 buildings are located in landslides threatened area. Therefore, landslide hazard maps should, always, guide the land use and urbanization in landslides prone areas.

Changes in water‐soluble nitrogen and organic carbon in the post‐fire litter layer of Dahurian larch forests

Boreal forests account for one third of terrestrial carbon stock. Wildfires are an important perturbation of this carbon pool, affecting in particular the litter layer. After forest fires, the litter layers may possess shifting chemical property and decomposition dynamics due to the changes in post-fire vegetations succession and abiotic factors. We measured water-soluble organic carbon (WSOC) and water-soluble nitrogen (WSN) in the litter layers of Oi and Oe horizons in boreal forests along a gradient of fire history in northeastern China. We found that WSOC and WSN concentrations in the Oi layer were higher than those in the Oe layer. The concentrations were markedly altered by fires and showed different responses to the ecological succession. The time since fire had significant positive correlations with WSOC in Oi and Oe layers. Interestingly, the distance-based redundancy analysis and the structural equation model analysis indicated that factors additional to the time since fire also strongly influenced the litter water-soluble matter (WSM) properties. Biotic factors were more strongly correlated with the litter WSM properties in the Oe layer than in the Oi layer. Although biotic factors contributed less than abiotic factors to the WSM properties, they still play significant roles in litter WSM in burned area. Our results show that manipulating biotic factors can be an important management strategy for litter WSM restoration, which can assist the overall ecological restoration in burned forests faced with the increasing danger of wildfires in the changing global climate.

Quantifying Understory Complexity in Unmanaged Forests Using TLS and Identifying Some of Its Major Drivers

The structural complexity of the understory layer of forests or shrub layer vegetation in open shrublands affects many ecosystem functions and services provided by these ecosystems. We investigated how the basal area of the overstory layer, annual and seasonal precipitation, annual mean temperature, as well as light availability affect the structural complexity of the understory layer along a gradient from closed forests to open shrubland with only scattered trees. Using terrestrial laser scanning data and the understory complexity index (UCI), we measured the structural complexity of sites across a wide range of precipitation and temperature, also covering a gradient in light availability and basal area. We found significant relationships between the UCI and tree basal area as well as canopy openness. Structural equation models (SEMs) confirmed significant direct effects of seasonal precipitation on the UCI without mediation through basal area or canopy openness. However, annual precipitation and temperature effects on the UCI are mediated through canopy openness and basal area, respectively. Understory complexity is, despite clear dependencies on the available light and overall stand density, significantly and directly driven by climatic parameters, particularly the amount of precipitation during the driest month.

Additivity of stand basal area predictions in canopy stratifications for natural oak forests

Stand basal area is an important variable for evaluating forest productivity. In this study, four types of growth models were used for modeling the stand basal area of natural oak forests in Hunan Province, China. The results showed that the Schumacher model (Eq. (3)) performed the best. Because of different canopy layers in natural oak secondary forests, it is important to develop stand basal area models considering canopy stratification. Three widely used canopy stratification methods were used for natural oak forests: the clustering analysis of tree height, classification scheme of the International Union of Forest Research Organizations (IUFRO) standard, and canopy competition cut-off height (CCH) method. According to the standards set forth in the National Standards of the People’s Republic of China (GB/T 26424-2010), the forests were divided into two layers: upper and lower. Among the three canopy stratification approaches, the IUFRO method was selected as the best. In addition, it should be noted that the sum of the basal area predictions at different layers can generate inconsistent results, as compared to predictions from the total stand basal area model. To solve the additivity of stand basal area predictions, the additive stand basal area growth model was established by nonlinear seemingly unrelated regression (NSUR). Comparing with the whole stand basal area growth model without stratification, the R2 values of basal area growth models with stratification increased by 4.78% (from 0.9277 to 0.9721). In addition, compared with equations estimated separately, the NSUR method increased R2 by 0.82% (from 0.9721 to 0.9801). The results reveal that the NSUR method can be applied to solve the additivity of stand basal area predictions at each layer and can improve model precision, which provides helpful insights into developing stand growth models in natural forests.

Effects of thinning and stand types on litter stock and soil water-holding capacity

Objective This study aims to explore the effects of thinning and stand types on forest litter stock and soil water-holding capacity, and to provide scientific basis for evaluating water conservation function of different forest stands. Method Two forest types (Cunninghamia lanceolata forest and broad-leaved forest) and two types of thinning (thinning C. lanceolata forest and thinning broad-leaved forest) in three small river basins in Jiande City, Zhejiang Province were taken as the research objects. Litter and soil (0−10, 10−30, 30−60 cm) were collected in the field, and the water immersion method was used to analyze the influence of thinning on the forest litter stock and water-holding capacity of different forest stands. Three standard plots (20 m×20 m) were selected in each forest stand for litter collection and soil sampling. The litter stock, water-holding capacity and water absorption rate, as well as the soil bulk density, porosity and water-holding capacity were determined. The statistic data of litter and soil characteristics were analyzed using one-way ANOVA and Duncan. Result The litter stock of thinning C. lanceolata forest decreased by 25.2% (P＜0.05), while the maximum water-holding rate and effective retention rate of litter increased by 24.4% and 47.1%, respectively (P＜0.05). Thinning had no significant effect on litter stock in broad-leaved forests, but the maximum water-holding capacity and effective retention capacity of litter increased by 42.5% and 42.2% (P＜0.05) respectively, compared with those without thinning. The overall water-holding capacity of litter in thinning forest was higher than that in normal forest. Thinning significantly increased non-capillary pores porosity and water-holding capacity of non-capillary pores in 10−60 cm soil layer of C. lanceolata forest (P＜0.05). Thinning significantly increased soil non-capillary pores porosity and non-capillary water-holding capacity in 30−60 cm soil layer, as well as those in 0−10 and 30−60 cm soil layer of broad-leaved forest (P＜0.05). The maximal water-holding capacity of each soil layer in the thinning C. lanceolata forest was significantly higher than that in the thinning broad-leaved forest, and the maximal water-holding capacity of 0−60 cm (3 775.19 t·hm−2) of the thinning C. lanceolata forest was higher than that of other forest stands. Conclusion Thinning significantly improves the water-holding capacity of forest litter and soil, and the water conservation function of litter and soil in the thinning C. lanceolata forest is the strongest among the four treatments for two stands. [Ch, 3 fig. 5 tab. 24 ref.]

Effects of Urban Forest Types and Traits on Soil Organic Carbon Stock in Beijing

Forests can affect soil organic carbon (SOC) quality and distribution through forest types and traits. However, much less is known about the influence of urban forests on SOC, especially in the effects of different forest types, such as coniferous and broadleaved forests. Our objectives were to assess the effects of urban forest types on the variability of SOC content (SOC concentration (SOCC) and SOC density (SOCD)) and determine the key forest traits influencing SOC. Data from 168 urban forest plots of coniferous or broadleaved forests located in the Beijing urban area were used to predict the effects of forest types and traits on SOC in three different soil layers, 0–10 cm, 10–20 cm, and 20–30 cm. The analysis of variance and multiple comparisons were used to test the differences in SOC between forest types or layers. Partial least squares regression (PLSR) was used to explain the influence of forest traits on SOC and select the significant predictors. Our results showed that in urban forests, the SOCC and SOCD values of the coniferous forest group were both significantly higher than those of the broadleaved group. The SOCC of the surface soil was significantly higher than those of the following two deep layers. In PLSR models, 42.07% of the SOCC variance and 35.83% of the SOCD variance were explained by forest traits. Diameter at breast height was selected as the best predictor variable by comparing variable importance in projection (VIP) scores in the models. The results suggest that forest types and traits could be used as an optional approach to assess the organic carbon stock in urban forest soils. This study found substantial effects of urban forest types and traits on soil organic carbon sequestration, which provides important data support for urban forest planning and management.

Post-harvest forest herb layer demography: General patterns are driven by pre-disturbance conditions

Timber harvesting constitutes extensive anthropogenic disturbance in temperate forests, producing a broad range of ecological impacts that most often enhance the demographic processes of vegetation. This study monitored post-harvest herb layer demography over a 6-year period in mesic Dinaric fir-beech forests (Slovenia), a vascular plant diversity hotspot among European forests. Three experimental harvesting intensities, i.e. full harvest (FH), partial harvest (PH) and a control treatment (NH), were each applied over a circular area of 4000 m2 and replicated three times at each of three study sites. Vegetation sampling was conducted before harvesting (in 2012), and two (2014) and six (2018) years following it, in a 400 m2 circular plot positioned in the centre of each treatment area. We focused on identifying general demographic patterns and evaluating the effects of various pre-disturbance abiotic and biotic predictors on compositional responses to disturbance. Two years after harvest (2012–2014), compositional shifts were larger than those in the next 4-year period (2014–2018), confirming the general theoretical prediction that species turnover rate decreases along a successional gradient. The degree of compositional shifts in gaps (FH) and thinned stands (PH) was affected by local abiotic factors (geomorphology of karst sinkholes) and community attributes, such as pre-harvest species richness. Our results indicate that compositional stability is positively associated with pre-disturbance species richness. Over the whole study period, increases in plot-level species richness (alpha diversity) and overall enrichment of the species pool (gamma diversity) were accompanied by compositional convergence, i.e. a decline in floristic dissimilarity (beta diversity) between and within study sites. However, the observed tendency towards homogenization was rather weak and would have been even more pronounced if the demographic type of persistent resident species had not shown a high degree of resistance, thus leaving a strong imprint on post-harvest vegetation development by preserving the forest characteristics of the herb layer community.

Carbon accumulation by Pinus sylvestris forest plantations after different periods of afforestation in a semiarid sandy ecosystem

AbstractThe carbon pool is changing in afforestation ecosystems, which vary in their duration since establishment, in many semiarid sand regions. Understanding this is important for the management of the planted forest. The present study explored the dynamics of afforested forest carbon pool in a semiarid sandy ecosystem, northwest China. We studied afforested forests of pine (Pinus sylvestris) of five afforestation ages (20, 30, 40, 50, and 60 years since planting, and bare sand as control), the carbon storage and carbon sequestration rate of the forest aboveground biomass layer, surface litter layer, and soil layer (0–50 cm) were calculated, and the soil water content and soil organic carbon of 0–400 cm soil depth were measured. The results showed that the carbon sequestration rate was highest after 20–30 years, with 0.58 Mg C ha−1 yr−1 in the soil layer (0–50 cm). We found a rate of 0.13 Mg C ha−1 yr−1 in the surface litter layer, and a rate of 20.79 Mg C ha−1 yr−1 in the forest aboveground biomass layer. The carbon storage of the forest aboveground biomass layer was highest after 30–40 years, and the carbon storage of the surface litter increased with time. In the soil layer, the carbon storage at 0–10 cm depth was highest after 60 years, the carbon storage at 20–50 cm depth increased soon after afforestation and then decreased afterward with increasing afforestation ages with the maximum for 20‐50 cm occurring after 30–40 years. The total carbon storage [the forest aboveground biomass layer, surface litter layer and soil layer (0‐50 cm)] was higher when afforestation ages reached around 30 years, after that it decreased with increasing afforestation age. Our research improves the understanding of the P. sylvestris forest ecosystem carbon sequestration in a semiarid sandy area.

Quantitative Assessment of Vegetation Layers in Tropical Evergreen Forests of Arunachal Pradesh, Eastern Himalaya, India

The present study deals with first-hand information on quantitative assessments of different vegetation layers (viz. trees, saplings, seedlings, shrubs and herbs) collected from 57 permanent plots (size 400 m2), established for long-term monitoring of biodiversity and study of functional aspects in Namdapha National Park (NPP), Arunachal Pradesh, Eastern Himalaya, India during 2017. We grouped all the plots into six clusters as study sites. A total of 60 taxa of trees, 67 shrubs and 81 herbs were recorded within 57 plots during the study. The average species richness per site for trees was 20.83 ± 1.62, saplings 16.0 ± 1.15, seedlings 15.83 ± 1.35, shrubs 23.83 ± 1.58 and herbs 32.67 ± 0.92. Total stem density varied from 117.5 to and 181 ha –1 (152.58 ± 10.04 ha –1 ) for trees (circumference m31.5 cm), 881 to 3000 ha –1 (1652.17 ± 317.61 ha –1 ) for shrubs and from 76750 to 98545 ha –1 (92032.17 ± 3246.60 ha –1 ) for herbs. Tree regeneration status at all the six study sites was ‘good’ (i.e. density of seedlings > saplings > trees). The distribution of tree stems (circumference m31.5 cm) into different size classes showed highest relative density in the lowest stem size class (10–20 cm diameter) which also indicates good tree regeneration in the study area. Dipterocarpus retusus Blume was the most dominant tree species in the core zone area of NNP with ‘good’ regeneration status.

Spatial–temporal variations of absorptive fine roots in the organic and soil layers of a Larix gmelinii forest

In the organic layer, absorptive fine roots of Larix gmelinii represent a significant proportion of the total fine-root biomass and can morphologically adjust during the growing season to optimize resource acquisition. Larix gmelinii is a foundational tree species in forests of northern China and Far-East Russia. A better understanding of the species’ belowground resource acquisition strategy is important for soil nutrient and carbon estimates. Here, we investigated seven traits of absorptive fine-roots at four depth levels, from the organic layer (organic, decomposed litter from dead plants) down to a soil depth of 30 cm in May, July and September of 2016. Biomass and functional traits of absorptive fine roots varied significantly, indicating the species ability to adjust its resource acquisition across the four depth layers. From the organic layer to deeper mineral soil layers, root diameter and tissue density increased, while specific root length decreased, in other words, roots become longer and thinner with increasing values of soil water and nutrient concentrations. At the same time, the average biomass and length of absorptive fine roots in the organic layer accounted for 14% and 16% of the total, respectively. With increasing soil depth, the averaged proportion of biomass and length density of absorptive fine roots to the total fine roots decreased significantly from almost 57 to 32%, and 80–62%, respectively. Finally, total soil nitrogen concentration showed the strongest link with absorptive fine-root traits, such as root diameter, specific root length, root standing biomass and length density. Our results indicate that absorptive fine roots in the organic layer play a crucial role in belowground resource acquisition and carbon cycle in a common and economical important species.

How do invasive trees impact shrub layer diversity and productivity in temperate forests?

• Key messageInvasive tree species alter taxonomic diversity and functioning of forest shrub layers: Prunus serotina increases shrub layer biomass two to three times but decreases its biodiversity, Robinia pseudoacacia slightly increases shrub layer biomass and has no effect on its biodiversity, while Quercus rubra both biomass and biodiversity of the shrub layer.• ContextAlthough the impact of invasive trees on understory biodiversity is known, very little data exist about their influence on shrub layer biodiversity and productivity.• AimsTo assess impacts of Prunus serotina Ehrh., Quercus rubra L., and Robinia pseudoacacia L. on shrub layer aboveground biomass, species composition, and alpha diversity.• MethodsWe measured stand structures in a set of 168 study plots established in Wielkopolski National Park (W Poland), and we compared biomass and diversity metrics using generalized mixed-effects linear models.• ResultsWe found the lowest aboveground biomass of shrub layers in Q. rubra forests. P. sylvestris forests invaded by P. serotina had two to three times higher aboveground biomass than non-invaded forests. R. pseudoacacia forests had 27.8% higher shrub layer biomass than Quercus-Acer-Tilia forests. We found negative impacts of Q. rubra and negligible impacts of R. pseudoacacia on shrub layer alpha diversity metrics. However, the effect of Q. rubra was similar to native F. sylvatica. P. serotina negatively affected functional diversity, but its effects were lower in rich P. sylvestris forests than in poor P. sylvestris forests.• ConclusionThe introduction of alien tree species alters ecosystem services and species diversity of shrub layers. The direction and magnitude of these alterations are alien species-specific and context-dependent. Therefore, their management should account for their impacts.

Positive interactions between great longhorn beetles and forest structure

Great longhorn beetles (GLBs) may affect forest structure, because their larvae colonize trees and create networks of cavities further exploited by other species, resulting in dead or broken branches and tree mortality. At the same time, tree size, condition and location are known to affect the likelihood of tree colonization by GLBs. Here, we study the relationship between GLBs and the structure of old-growth holm oak Mediterranean forests in Sardinia, Italy. Generalized linear models were used to relate presence of GLBs with structural parameters that can be affected by or can affect these ecosystem engineers. We found a strong positive relationship between GLBs and the number of trees with cavities, while the relationships between GLBs and the number of dead wood decaying classes, amount of coarse woody debris, stand basal area, forest canopy layer complexity were positive but weak. Overall, our results suggest that larval activity of GLBs could be responsible for increased tree cavity and dead wood formation, enhancing forest structure. On the other hand, forests with larger and older trees could be more likely to be colonized by GLBs. While it is not possible with observational studies to disentangle to what extent GLBs affect forest structure or vice versa, it seems likely that reciprocal interactions may enhance the structure of holm oak forests. Therefore, parasitism from native GLBs should be seen and understood more as a key ecological process that enhances the structure of Mediterranean holm oak forest habitats.

Understory vegetation contributes to microclimatic buffering of near-surface temperatures in temperate deciduous forests

Accurately predicting microclimate is considered a high priority for understanding organismal responses to climate change at biologically relevant scales. However, approaches to developing robust microclimate datasets and understanding of the biophysical processes altering microclimatic regimes are limited. We developed and evaluated an approach for predicting microclimatic temperatures in montane forests that incorporates the influence of complex vegetation structure and landscape physiography. Additionally, we determined spatiotemporal mismatches between free-air and microclimatic temperatures to highlight the location, phenology, and magnitude of differences in predicted temperature. We combined temperature datalogger measurements with LiDAR-derived vegetation and GIS-derived landscape physiographic characteristics to downscale free-air temperatures to microclimatic (3 m2 spatial resolution) temperatures in the Great Smoky Mountains. We assessed the contribution of forest vegetation layers in altering microclimatic temperatures and model accuracy, and compared coarse-grain temperature maps with microclimatic temperature maps. Understory vegetation structure contributes to microclimatic buffering of near-surface, forest temperatures and enhances the accuracy of maximum temperature predictions during the growing season by altering the effects of solar insolation and topographic convergence index on microclimatic temperatures. Elevation and solar insolation covaried with spatiotemporal mismatches between free-air and microclimatic temperatures, suggesting that these landscape physiographic characteristics may contribute to deviations between macro- and micro-scale temperature. Our findings demonstrate the importance of including complex vegetation characteristics and biophysical interactions as climate forcing factors in microclimate modeling. We also demonstrate the plausibility of accurately predicting microclimatic temperatures over broad extents, an important step in predicting potential organismal responses to climate change.

Differential equations application in progress prognosis of the pyrogenic succession process of grass and shrub layer of pine forest

This article is devoted to the differential equations system application of the Morino – Voight mathematical model for predicting the process of pyrogenic succession of a pine forest. For the first time, the results of predicting the process of pyrogenic succession according to the Morino – Voight model were compared with real data characterizing the restoration of a pine forest after a fire.

A Technique to Evaluate Agricultural Landscape Changes on the Basis of GIS-Processed 1861 Demarcation Plans and Current Description of Kenozero National Park

In many Russian nature reserves traditional landscapes are objects of important historical and cultural heritage. To preserve and restore them one needs to deeply understand their development, formation and degradation processes. In the north of European Russia agricultural landscapes are often covered with forests and lose their features when agricultural activity decreases. However, structural characteristics of these forests as a rule tell us about their development and peculiarities of successions. The study aims at creating a technique to estimate the scope of former agricultural land development, model historical transformation of agricultural landscapes and identify plots of slash and burn, shifting, two and three field agriculture judging by structural characteristics of post-agrarian forests. Aided by GIS the study compares raster analogs of land demarcation plans of the second half of the 19th century and vector layers of present day forests with attributive data on the forest structure. The use of cartographic forest data and inventory forest characteristics to compare with former land management documents related to the plot named have not been found in studies before. High precision of present day land management provides for permitted comparability with old demarcation plans and allows one to use inventory data for inter-landscape differentiation of agricultural landscapes in the 19th century. The study covers a model plot within Kenozero National Park (Arkhangelsk Region) addressing 1861 demarcation plans and 2014 forests GIS developed by Arkhangelsk branch of Roslesinforg. GIS processing of 19th century and present day demarcation plans provides for modeling agricultural landscape changes in relation to separate plots, trace the influence of soil conditions and elements of agrarian use on topological and inventory changes of emerging forests and reconstruct the biodiversity of ecosystems in the past.

Drivers of understorey biomass: tree species identity is more important than richness in a young forest

Abstract Aims Positive biodiversity–ecosystem functioning relationships have been widely reported, predominately from grassland ecosystems. However, this does not necessarily have to apply accordingly in more complex situations such as in forests across different vertical strata. For instance, overstorey tree species richness has been shown to be associated with a lower understorey productivity. Whether or not tree species richness effects add to understorey productivity by increasing (i.e. due to habitat heterogeneity) or reducing resource availability (i.e. through increasing competition) and whether understorey productivity is indeed being governed more strongly by tree species identity are likely to change over time. Moreover, studies also suggested that richness–productivity relationships change with the environmental context. Using an experimental forest plantation with manipulated tree species richness, this study examined these temporal and environmental dynamics across strata. Methods In the context of the Biodiversity-Ecosystem Functioning project in subtropical China (BEF-China), we made use of understorey biomass samples repeatedly collected over a time period of 3 years along a tree species richness gradient. The effects of tree species richness, tree species identities and time were studied across different environmental treatments for their impact on understorey biomass. Important Findings While we found significant and consistent tree layer identity effects on understorey biomass, no such effect was encountered for tree species richness. Our results also indicate that among structural layers in forests, there might not be a single, generalizable overstorey species richness–understorey productivity relationship, and that the extent as to which overstorey-related environmental factors such as light transmittance contribute to understorey productivity change with time. Overall, we demonstrate that temporal dynamics should be considered when studying relationship among structural layers in forests.

New Topsoil Sampler for the Assessment and Monitoring of Forest Soil Contamination

The forest litter and underlying mineral topsoil are typically sampled and analyzed separately although they are in a dynamic balance, which ensures macro- and microelement cycling in the forest ecosystem, including the flux and accumulation of xenobiotics in the contaminated sites. Although the national legal regulations specify single limits of element concentration for the entire “topsoil” layer, irrespectively of the kind of materials resting at the earth surface down to the specified depth, the direct analysis of bicomponent forest topsoil (litter + mineral topsoil) was problematic because of the lack of a suitable sampler. The paper presents a comparative analysis of Cu, Pb, and Zn concentrations in the forest topsoil layers (0–25 cm), sampled using a new construction sampler invented for a joint collection of the litter layer and underlying mineral layer (to the specified depth). Litter samples (using a steel frame), mineral topsoil samples (0–25 cm, using gouge auger after litter removal), and mixed topsoil samples (0–25 cm, including litter) were collected in 16 replicates from four variably contaminated plots (copper mining and smelting area) afforested with poplar or pine. Pseudo-total concentration of Cu, Pb, and Zn was analyzed after sample digestion in aqua regia. The concentration of elements in the samples consisting of jointly collected litter and mineral layer was noticeably higher than in the samples consisting of the mineral topsoil only, which confirmed the effective inclusion of the litter. The concentrations of trace elements measured in the samples of jointly collected litter and mineral topsoil did not differ (NIR Fisher test at p < 0.05) from the concentrations calculated using the data for litter and mineral soil separately collected and analyzed, which confirmed the usefulness of the new sampler for reliable collection of the forest topsoil samples without skipping any material which may influence the results of soil contamination assessment and risk assessment.

Studies on soil physico-chemical properties at different locations and elevations of Quercus leucotrichophora forests

The present investigation entitled “Studies on soil physico-chemical properties at different locations and elevations of Quercus leucotrichophora forests” was carried out during the year 2018-19 to know the soil physico-chemical properties in Chail forests of district Solan, Kufri forests of district Shimla, Sarahan and Churdhar forests in Sirmaur district of Himachal Pradesh with three elevations i.e., E1 (1800 m) in each. Composite samples were collected from 15 cm depth for soil and biochemical analysis. Among locations, the thickness of forest litter layer, microbial activity, available K and P content showed a decreasing trend as: Kufri forest soils > Chail forest soils > Churdhar forest soils > Sarahan forest soils. Among elevations, the thickness of forest litter layer and Organic C followed the trend as: E3 > E2 > E1 whereas, soil pH, bulk density, available N, P and K content fell as E1 > E2 > E3. Maximum available N, soil EC and Bulk density was found in Chail forest. Kufri forest soils have shown best results for all soil parameters.

天目山常绿落叶阔叶林群落垂直结构与群落整体物种多样性的关系

以浙江省天目山1 hm²常绿落叶阔叶混交林样地调查数据为基础，运用K-means聚类方法将DBH≥1 cm的个体根据树高划分为不同林层，研究比较了各个林层的物种多样性特点；利用通径分析方法和决策系数定量计算各个林层物种多样性对群落整体物种多样性的直接作用和间接作用，天目山常绿落叶阔叶林垂直结构对群落物种多样性构成的影响。结果表明：（1）天目山常绿落叶阔叶林群落层次结构丰富，树高由1.4-36.5 m依次可分为灌木层、亚冠层、林冠下层、林冠中层和林冠上层。（2）天目山常绿落叶阔叶林群落从灌木层依次往向上，物种丰富度、多度、特有种数量、Shannon-Weiner指数和Simpson指数均呈下降趋势。（3）灌木层对群落物种多样性的贡献最大且远高于其他四个林层，其中灌木层对群落整体物种多样性Shannon-Wiener指数、Pielou指数以及Simpson指数的决策系数分别为0.850、0.651、0.755。（4）林冠下层、林冠中层和林冠上层密度的大小对灌木层的物种数目有明显的影响，林冠层密度越大，灌木层群落的物种数目越少，复杂程度越低；偶见种和稀有种对群落物种多样性的维持具有特殊作用。综上，研究认为森林群落的垂直结构在维持森林群落整体物种多样性中具有关键作用，而灌木层在群落整体物种多样性构成中具有决定作用，森林群落中稀有种、偶见种多少在群落物种多样性构成中具有特殊作用。;Based on the survey data of 1 hm² deciduous and evergreen broadleaved forest plot in Tianmu Mountain of Zhejiang Province, we assessed species biodiversity by K-means clustering method, the individuals with diameter at breast height(DBH) ≥ 1 cm was divided into different forest layers according to tree height, and the features of species diversity in each layer were computed, compared, and contrasted. In addition, the direct and indirect biodiversity impacts also evaluated by using path analysis, namely, the quantity of decision coefficients. The objective of the study was to reveal the influence of vertical structure on community species diversity in an evergreen deciduous broad-leaved forest community. The results demonstrated that:(1) the forest community had multiple-layered vertical structure, which could be divided into five layers:shrub layer (1.4-4.2 m), sub-canopy layer (4.3-7.6 m), lower canopy layer (7.7-13.4 m), middle canopy layer (13.5-21.5 m), and upper canopy layer (21.6-36.5 m). (2)The species richness,abundance,the number of endemic species, Shannon-Weiner index and Simpson index of the community appeared a downward trend from bottom to top layers. (3)Shrub layer was the largest contributors to the community overall species diversity index and was much higher than the other four forest layers. And the decision coefficient of shrub layer towards overall species diversity of community that Shannon-Wiener index, Pielou index and Simpson index was 0.850, 0.651, and 0.775, respectively. (4) The density of lower canopy, middle canopy, upper canopy had a negative impact on the species number of the shrub layer. The larger density of the forest canopy was, the less the number of species would become in the shrub community as well as the complexity. In addition, the occasional and rare species in the shrub layer also played a key role in maintaining the species diversity of the shrub layer. In conclusion, the vertical structure of the community was critical in maintaining the overall species diversity of the given forest community. The shrub layer played a decisive role in the composition of overall species diversity, besides the number of occasional and rare species also played a key role on the composition, thus, species diversity of the community.

桂林岩溶石山常绿落叶阔叶混交林乔木层优势物种生态位研究

采用样方法对不同资源位群落进行调查，通过冗余分析（RDA）结合Monte Carlo随机置换检验筛选出对桂林岩溶石山常绿落叶阔叶混交林乔木层优势物种分布影响显著的土壤资源轴（土壤有机质、土壤水溶钙、土壤速效氮、土壤全氮、土壤pH值和土壤厚度）。利用Levins生态位宽度指数和Pianka生态位重叠指数对桂林岩溶石山常绿落叶阔叶混交林乔木层14个优势物种在土壤有机质、土壤水溶钙、土壤速效氮、土壤全氮、土壤pH值和土壤厚度6个土壤资源轴上的生态位特征进行研究。结果表明：（1）在土壤有机质和土壤水溶钙资源轴上，生态位宽度最大值为常绿物种檵木（0.89、0.94）；在土壤pH值资源轴上，生态位宽度最大值为常绿物种粗糠柴（0.96）；在土壤速效氮、土壤全氮和土壤厚度资源轴上，生态位宽度最大值为落叶物种南酸枣（0.87、0.99、0.97）。（2）14个优势物种在6个土壤资源轴上，生态位重叠均值由大到小依次为土壤厚度 > 土壤全氮 > 土壤水溶钙 > 土壤速效氮 > 土壤pH值 > 土壤有机质，且均表现为常绿物种与常绿物种形成的种对生态位重叠均值（0.84） > 常绿物种与落叶物种（0.74） > 落叶物种与落叶物种（0.66）。（3）综合6个土壤资源轴，生态位重叠值≥0.5的种对高达480对，占总种对数的87.91%，暗示桂林岩溶石山常绿落叶阔叶混交林乔木层优势物种在资源匮乏且资源异质性高的特殊生境中存在激烈竞争，且乔木层种间关系相对不稳定。;The sample method was employed to investigate the communities with different resource positions. The soil resource axes (soil organic matter, soil water-soluble calcium, soil available nitrogen, soil total nitrogen, soil pH value, and soil depth) which have significant influence on the distribution of dominant species in arbor layer of evergreen deciduous broad-leaved mixed forest in karst hills of Guilin were selected by Redundancy analysis (RDA) with Monte Carlo random replacement test. Niche characteristics of 14 dominant species which in the arbor layer of evergreen deciduous broad-leaved mixed forest in karst hills of Guilin along soil organic matter, soil water-soluble calcium, soil available nitrogen, soil total nitrogen, soil pH value and soil depth were analyzed by Levins niche breadth index and Pianka niche overlap index. The results showed that:(1) on the soil organic matter and soil water-soluble calcium resource axis, the maximum niche width was evergreen species, which were Loropetalum chinense (0.89, 0.94); on the soil pH value resource axis, the maximum niche width was the evergreen species Mallotus philippensis (0.96); on the soil available nitrogen, soil total nitrogen and soil depth resource axis, the maximum niche width was deciduous species, which were Choerospondias axillaris (0.87, 0.99, 0.97). (2) The 14 dominant species composed 91 species pairs on 6 soil resource axes, and their niche overlap averages in descending order were as follows:soil depth > soil total nitrogen > soil water-soluble calcium > soil available nitrogen > soil pH value > soil organic matter. And the six soil resource axes were all showed as the mean niche overlap of species pair between evergreen dominant species and evergreen dominant species (0.84) > evergreen dominant species and deciduous dominant species (0.74) > deciduous dominant species and deciduous dominant species (0.66). This showed that the 14 dominant species have the most intense competition on the soil depth resource axis, followed by soil total nitrogen resource axis, and soil organic matter resource was axis relatively small. Furthermore, the competition between evergreen species was the most intense, followed by competition between evergreen and deciduous species, and between deciduous species competition was relatively small. (3) Based on the six soil resource axes, there were 480 species pairs with niche overlap value ≥ 0.5, accounting for 87.91% of the number of total species pairs. It implies that the dominant species in the arbor layer of the evergreen and deciduous broad-leaved mixed forest in the karst hills in Guilin have fierce competition in the special habitats with scarce resources and high resource heterogeneity, and the interspecific relationship of arbor layer is relatively unstable.