Trees In Mixed Forest Research Articles

Urban Treetop Detection and Tree-Height Estimation from Unmanned-Aerial-Vehicle Images

Individual tree detection for urban forests in subtropical environments remains a great challenge due to the various types of forest structures, high canopy closures, and the mixture of evergreen and deciduous broadleaved trees. Existing treetop detection methods based on the canopy-height model (CHM) from UAV images cannot resolve commission errors in heterogeneous urban forests with multiple trunks or strong lateral branches. In this study, we improved the traditional local-maximum (LM) algorithm using a dual Gaussian filter, variable window size, and local normalized correlation coefficient (NCC). Specifically, we adapted a crown model of maximum/minimum tree-crown radii and an angle strategy to detect treetops. We then removed and merged the pending tree vertices. Our results showed that our improved LM algorithm had an average user accuracy (UA) of 87.3% (SD± 4.6), an average producer accuracy (PA) of 82.8% (SD± 4.1), and an overall accuracy of 93.3% (SD± 3.9) for sample plots with canopy closures less than 0.5. As for the sample plots with canopy closures from 0.5 to 1, the accuracies were 78.6% (SD± 31.5), 73.8% (SD± 10.3), and 68.1% (SD± 12.7), respectively. The tree-height estimation accuracy reached more than 0.96, with an average RMSE of 0.61 m. Our results show that the UAV-image-derived CHM can be used to accurately detect individual trees in mixed forests in subtropical cities like Shanghai, China, to provide vital tree-structure parameters for precise and sustainable forest management.

Competition intensity affects growing season nutrient dynamics in Korean pine trees and their microhabitat soil in mixed forest

Exploring the response mechanisms of the understorey replanted target trees to competitive pressure from upper neighbouring trees in mixed forests is the scientific basis for growth promotion of the target trees. Taking a mixed forest of artificial planted Korean pine trees (target species) and natural broadleaved trees as the studying case, six competition intensity gradients to Korean pine trees were established according to the Hegyi competition index and the responses of growth, hormones and nutrition status of the target Korean pine trees to different competition intensities were analysed. Competition intensities had significant effect on the growth of Korean pine trees, and the more significant the competition intensity was, the more pronounced the inhibition effect. When the Hegyi competition index was greater than 15, the neighbourhood trees had a significant inhibition effect on the growth of Korean pine trees. With the increase of the competition intensity, the content of gibberellin and indoleacetic acid in Korean pine trees decreased; the content of abscisic acid increased; the moisture content of needles, the soluble sugar content and C/N ratio of needles and roots decreased; the chlorophyll, P and K and starch content, and total non-structure carbohydrates (NSC) of needles and roots increased at first and then decreased; the P and K content and C/N ratio in Korean pine microhabitat soil decreased. Excessive adjacent tree competition reducing the living space, the endogenous hormone content, nutrient content, and NSC of the target Korean pine trees, resulting in the growth of the target trees and subsequent nutrient synthesis to be inhibited. Appropriate adjacent tree competition increased the target tree chlorophyll, NSC, and nutrient content and had no excessive inhibitory effect on the growth of the target Korean pine trees. There was certain trait correlationship between Korean pine needles and fine roots, but there was an endostatin equilibrium mechanism for changes in the surrounding soil of the target trees. The above results indicated that competition intensity of the upper neighbourhood trees significantly influenced the growth and internal nutrient situation of the replanted target trees and their microhabitat soil conditions. In this case, when the Hegyi competition index of neighbouring trees in the surrounding area of the understorey planted target Korean pine trees was greater than 15, the growth space of target trees should be regulated to ensure their healthy development.

Effect of Different Plant Communities on Fine Particle Removal in an Urban Road Greenbelt and Its Key Factors in Nanjing, China

Determining the relationships between the structure and species of plant communities and their impact on ambient particulate matter (PM) is an important topic in city road greenbelt planning and design. The correlation between the distribution of plant communities and ambient PM concentrations in a city road greenbelt has specific spatial patterns. In this study, we selected 14 plant-community-monitoring sites on seven roads in Nanjing as research targets and monitored these roads in January 2022 for various parameters such as PM with aerodynamic diameters ≤10 µm (PM10) and PM with aerodynamic diameters ≤2.5 µm (PM2.5). We used a spatial model to analyze the relationship between the concentrations of ambient PM10 and PM2.5 and the spatial heterogeneity of plant communities. The consequences revealed that the composition and species of plant communities directly affected the concentrations of ambient PM. However, upon comparing the PM concentration patterns in the green community on the urban road, we found that the ability of the plant community structures to reduce ambient PM is in the order: trees + shrubs + grasses > trees + shrubs > trees + grasses > pure trees. Regarding the reduction in ambient PM by tree species in the plant community (conifer trees > deciduous trees > evergreen broad-leaved trees) and the result of the mixed forest abatement rate, coniferous + broad-leaved trees in mixed forests have the best reduction ability. The rates of reduction in PM10 and PM2.5 were 14.29% and 22.39%, respectively. We also found that the environmental climate indices of the road community, temperature, and traffic flow were positively correlated with ambient PM, but relative humidity was negatively correlated with ambient PM. Among them, PM2.5 and PM10 were significantly related to temperature and humidity, and the more open the green space on the road, the higher the correlation degree. PM10 is also related to light and atmospheric radiation. These characteristics of plant communities and the meteorological factors on urban roads are the foundation of urban greenery ecological services, and our research showed that the adjustment of plant communities could improve greenbelt ecological services by reducing the concentration of ambient PM.

Climate-sensitive tree height-diameter models for mixed forests in Northeastern China

Models based on height-diameter (H-D) are helpful for estimating forest biomass and carbon storage on a large scale. Climate change has an impact on allometric height-diameter growth. H-D models explaining climatic effects are still inadequate due to the complexity of mixed forests. This paper developed climate-sensitive mixed-effects models for 14 tree species based on 316 natural mixed forest plots in Northeastern China and compared the response of tree height growth to environmental gradients for multiple species. The results showed that the species heterogeneity leads to the differences in scaling exponents in varying degrees. The analysis revealed that incorporating mean annual temperature (MAT), mean annual precipitation (MAP), dominant tree height (HT), basal area of the larger trees (BAL), and Shannon diversity index significantly enhanced the predictive ability of the model. By exploring the tree height change patterns of each tree species under different gradients of environmental factors, we found that increases in temperature, precipitation, site quality, and competition intensity positively affected height growth in mixed forests. In contrast, increases in species diversity inhibited height growth. The degree to which environmental factors regulate the H-D allometric growth of trees in mixed forests is related to species specificity. This paper provides theoretical support for tree height estimates of major tree species in mixed forests under global climate change by introducing environmental factors to improve the H-D model of 14 tree species.

Mixed forest suffered less drought stress than pure forest in southern Siberia

Hotter droughts are becoming a major threat to forest growth in water-limited regions. Species interactions have long been acknowledged as an important component modulating ecosystem functions, including mediating their vulnerability to climate-related stresses. However, quantifying the impact of species interactions on forest growth in response to drought remains a challenge. Using the tree ring data of two species in two pure forests and two coniferous and broad-leaved mixed forests with different degrees of mingling in southern Siberia within the period of 1960–2017, we found that mixed forests with higher mingling have a higher ability to withstand the effect of extreme drought events, which is especially beneficial to the resistance and resilience of broad-leaved trees. Larch trees showed a remarkable consistency in their resistance and resilience to extreme drought events in both pure and mixed stands, suggesting their ability to promote the growth of neighboring white birch without reducing their own growth. The growth of white birch trees was enhanced in mixed forests and showed a significant trend of increasing resistance and resilience with increasing mingling. Our results provide further evidence of a decreasing duration of the legacy effect with increasing mingling for both coniferous and broad-leaved trees, which might explain the improved tolerance to drought of trees in mixed forests compared to those in pure forests in water-limited hemiboreal southern Siberia. Our study implies that changes in forest structure might help forests respond to hotter droughts in water-limited regions.

Cell characteristics of Larix principis-rupprechtii on the edge of different stand types

To analyze the effects of forest edge on radial growth and cell characteristics in different stand types of Larix principis-rupprechtii, we investigated the differences on radial growth, cell size and numbers between edge trees and inner trees of L. principis-rupprechtii in pure L. principis-rupprechtii forests and mixed forests of L. principis-rupprechtii and Betula platyphylla in Saihanba mechanical forest farm, China. The results showed that radial growth of the edge trees was significantly faster than that of the inner trees in pure forests, with the total ring width, earlywood width and latewood width of edge trees being 48.9%, 58.9% and 29.6% higher than those of inner trees, respectively. However, there was no difference in radial growth between edge trees and inner trees in mixed forest. The total number of earlywood cells, the number of large cells and small cells in earlywood of edge trees were increased by 63.3%, 55.6% and 70.0%, while the total number of latewood cells, the number of large cells and small cells in latewood of edge trees were increased by 35.4%, 37.5% and 28.5% compared with those of inner trees. There was no significant difference in the cell sizes between edge trees and inner trees. The cell numbers of earlywood and latewood of edge trees were not significantly different from those of inner trees in mixed forest, but the cell size in the earlywood of edge trees was 50.0% larger than those of inner trees in mixed forest. The sizes of the largest cells, the smallest cells, the large cells and the small cells in the earlywood of edge trees were increased by 28.6%, 33.3%, 16.6% and 25.0% compared with those of inner trees, respectively. The fast growth of edge trees and slow growth of inner trees in the pure forests could be effectively alleviated by cultivating mixed forests.

Light Competition Contributes to the Death of Masson Pines of Coniferous-Broadleaf Mixed Forests in Subtropical China

In the process of subtropical forest succession, it has long been recognized that population decline of Masson pines in coniferous-broadleaf mixed forest is caused by shading from broadleaf trees. However, little is known about the mechanism underlying the interaction between them. Here, we first chose two sets of Masson pine plots approximately aged 60 years in subtropical mountainous areas in eastern China (i.e., pure coniferous forest vs. coniferous-broadleaf mixed forest). Then, we measured and compared tree height, diameter at breast height, first branch height (FBH), live crown ratio (LCR) of Masson pines between the two sets of plots, and also determined the difference in growth performance of Masson pines relative to their neighboring broadleaf trees in the mixed forest stand. Compared with plots in pine forests, Masson pines in mixed plots had lower tree height and crown breadth, higher FBH, lower LCR, and leaf area. Furthermore, the difference of mean FBH between reference trees (Masson pines) and their neighboring trees (i.e., broadleaf trees) in mixed forest plots was greater than that in pine forest plots, and the ratio of LCR between Masson pines and their neighbors (0.46) in mixed forest was significantly smaller than in pine forest (1.05), indicating that those broadleaf trees around Masson pines probably affected their growth. The mean distance between Masson pines and neighboring trees (1.59 m) in mixed forest plots was significantly shorter than in pine forest plots (2.77 m) (p < 0.01), suggesting that strong competition may occur between reference trees and their neighbors. There was a significant difference in the ratio of crown volume between reference tree Masson pine and its neighboring trees in mixed forests (p < 0.01), indicating that the ratio of biomass synthesis to consumption of pines was much lower than their nearby broadleaf trees in mixed forest. Our results have demonstrated for the first time that Masson pines’ population decline is affected by shade-tolerant broadleaf late-successional species, which can be primarily attributed to the distinctive light transmittance of dominant species nearby (pure pine vs. mixed forest). This study provides a new perspective for future studies on the mechanism of forest succession.

Structural characteristics of mixed plantation of pinus massoniana and oak in danjiangkou reservoir area

In this paper, the frequency distribution of DBH and DBH of masson pine and oak trees in mixed forest was simulated by using normal distribution, and the relationship between DBH and tree height was fitted by 11 common curve models. The power model can well simulate the relationship between DBH and tree height.

Bat Community Responses to Structural Habitat Complexity Resulting from Management Practices Within Different Land Use Types — A Case Study from North-Eastern Germany

In the present study we evaluated how management practices, structural habitat parameters and arthropod availability affect bat activity, species richness and species diversity (estimated by Shannon's diversity index H') in a cultural landscape composed by a mosaic of different habitats in Brandenburg (Germany). Over a study period of two years (2012–2013), a standardised acoustic monitoring was conducted on 12 sampling sites comprising different land use types in forests (pine, mixed and deciduous forest) and agricultural areas (arable land and grassland). The focus was on the effect of small-scale changes in structural habitat parameters resulting from management practices within one-and-the-same land use type. We applied a paired sampling design and compared two (forest) and three (agricultural areas) sampling sites (complexity categories) per land use type. An effect of structural complexity was tested using parametric and non-parametric analyses. Sampling sites differ in a complexity index derived from vegetation measurements related to: a) vertical vegetation structure (pine forests), b) tree species composition (mixed forests), c) tree age (deciduous forests), d) crop type (arable land), and e) management intensity (grassland). Within the pine and mixed forest, management practices leading to an increase in structural habitat complexity were associated with a significant increase in bat activity, species richness, and species diversity (H'). This effect is only partially explained by increased prey abundance. On grassland, increased bat abundance is associated with low-intensity management practices. This effect is explainable by an increase in arthropod abundance associated with structural complexity but no additional effect of structural complexity beyond that. On arable land, the difference in structural complexity among different crops (and not prey abundance) significantly affects bat communities. Our approach employed proxy measures of habitat quality to estimate which management practices within the study area theoretically result in suitable and available habitats to meet the requirements of local bat species. Thus, our findings have implications for forest and agricultural management. Even minor changes in silvicultural management (understory development in pine monocultures and increased percentage of deciduous trees in mixed forests) may lead to a significant increase in forest habitat quality for bats. The findings also stress the importance of extensive management practices in grassland, as well as structure-rich crops on arable land to achieve a more environmentally sustainable farmland management.

Distinct growth responses to drought for oak and beech in temperate mixed forests

PurposeDroughts are expected to become more intense and frequent. Mixed forests can be more resilient to extreme events, but are the individual trees in mixed forests also more resilient to drought? MethodsWe sampled 275 trees in 53 temperate forest stands in northern Belgium: monocultures, two-species mixtures, and the three-species mixture of Fagus sylvatica, Quercus robur, and Q. rubra. We related the annual basal area increment of individual trees to drought severity from 1955 to 2015 and calculated growth resistance, recovery, and resilience for six contrasting drought episodes (spring, summer, or full-year drought). ResultsTree growth of the diffuse-porous F. sylvatica was more sensitive to drought, summer drought in particular. The ring-porous Q. robur and Q. rubra were mainly affected by spring drought. In general, a tree's growth response to drought was not affected by tree species diversity, but some identity effects emerged. ConclusionThe asynchrony in drought responses among the tree species (a large and immediate decrease in growth followed by swift recovery in F. sylvatica vs a smaller delayed response in Quercus) might stabilize productivity in forests in which both are present. The impact of the predicted increasing drought frequency will depend on the timing of the droughts (spring vs summer).

Detecting the Competition between Moso Bamboos and Broad-Leaved Trees in Mixed Forests Using a Terrestrial Laser Scanner

The growth of individual trees in a forest is affected by many factors, a crucial one being the intensity of competition among trees, because it affects the spatial structure of the forest and is in turn influenced by silvicultural practices. In a mixed forest in particular, the growth of trees is affected by multiple interactions. To analyse the competition between moso bamboo (Phyllostachys pubescens (Pradelle) Mazel ex J.Houz.) and broad-leaved trees in a mixed forest, data were extracted by sampling six spots within such a forest using terrestrial laser scanning (TLS). The convex hull algorithm was used for calculating the overlap volume between the crowns of the broad-leaved trees and the bamboo canopy. Bamboos growing at least 3 m away from any of the broad-leaved trees were the most numerous and the diameter at breast height (DBH) is larger than those growing closer than that, which suggests that broad-leaved trees suppressed the growth of bamboo if they are closer but promote it beyond 3 m up to a point at which the distance is too great for any such effect. The modified Hegyi’s competition index was constructed based on the canopy factor, which may better describe the competitive interaction among the trees and bamboos. Using TLS can enhance our understanding of the competition among trees in mixed forests and help in planning the spatial structure of such forests in general and provide a benchmark for choosing planting distances in particular.

Differential hydric deficit responses of Robinia pseudoacacia and Platycladus orientalis in pure and mixed stands in northern China and the species interactions under drought

The differential responses to water deficit would be the key factors to cause black locust decline and to drive a change in the forest composition in the mixed forest. This study was conducted in arborvitae (Platycladus orientalis)–black locust (Robinia pseudoacacia) mixedwood plantations with various compositions ranging from pure black locust to pure arborvitae to mixtures of the two located in semi-arid rocky hill area in northern China. In current years, black locust tends to decline and the forest composition is changing in favor to arborvitae. A dendroecological investigation and δ13C measurement of tree rings were applied to assess the relationships between water relations and growth in response to water deficits. Black locust in mixed forest had smaller tree-ring growth than that in pure forest in recent years, while arborvitae trees in mixed forest had bigger tree-ring width than those in pure stand. The δ13C values suggested that black locust in mixed forest had severer drought stress than that in pure forest, and arborvitae showed an opposite scenario. In early growth season, the soil was the driest in pure arborvitae, followed by mixed and then black locust forest. Black locust was more sensitive to drought than arborvitae with quickly closing stomata and reducing photosynthesis. Thus, the soil water regime in mixed forest was worse than that in pure forest for black locust, and was opposite for arborvitae. As a result, black locust in mixed forest had lower stomatal conductance and photosynthesis than that in pure black locust forest, whereas arborvitae had an opposite scenario. In summary, the results suggest that the differential responses to water deficit and the species interactions would be the key factors to cause black locust decline.

Evidence of short-term belowground transfer of nitrogen from Acacia mangium to Eucalyptus grandis trees in a tropical planted forest

The short-term belowground transfer of nitrogen from nitrogen-fixing trees to companion trees has never been studied in the field. A 15N pulse-labeling study was conducted in a mixed plantation of Acacia mangium and Eucalyptus grandis at the peak of leaf area, 26 months after planting. 15N–NO3− was injected into the stem of one big Acacia tree in three plots. 15N was traced over 2 months in the labeled Acacia tree as well as in neighboring Eucalyptus trees. For both species, young leaves were sampled, as well as fine roots and the rhizosphere at a distance of 0.75 m and 2.25 m from the labeled tree. The 15N atom% was also determined in the wood, bark, branches and total foliage of the 3 labeled Acacia trees and 9 Eucalyptus trees, 60 days after labeling. Most of the leaves, fine roots and rhizosphere samples of both species were 15N enriched from 5 days after labeling. The δ15N values were higher at a distance of 0.75 m than at 2.25 m in Acacia roots, but were similar at both distances in Eucalyptus roots and the rhizospheres. The wood and bark of Eucalyptus trees sampled at a distance of 6.2 m from the labeled Acacia trees were 15N enriched. This shows belowground N transfer from Acacia to Eucalyptus trees in the field during the first few days after labeling. This facilitation process may provide a significant amount of the nitrogen requirements of trees close to N-fixing trees in mixed forests.

Tree diversity in 30-year chronosequences of cool-humid forests

Tree data collected in four inventories of twelve permanent sampling plots during 30 years were analyzed to determine to what extent the abundance of the ubiquitous balsam fir (Abies balsamea) drives tree diversity in mixed stands of Eastern Cape Breton Island, Canada. Dominant deciduous species comprised yellow birch (Betula allegheniensis), sugar maple (Acer saccharum), and American beech (Fagus grandifolia). Tree species richness ranged from 2 to 6. The Shannon–Wiener diversity index indicated that high fir proportion decreased tree species diversity (H’) and structural evenness (J’). The basal area ratio for year 30 over year 1 provided an index of resilience (R) for forest stands subject to natural self-thinning and epidemic insect infestations. There was no significant effect of fir admixture on R since basal area losses due to fir decline were offset within the 30-year period largely by hardwood increases. Stand dynamics were however, structurally stratified due to low R-values for low-diameter trees. The indices H’, J’, and R are recommended for assessing the naturalness and apparent resilience function of tree diversity and large trees in mixed forests of low species richness.

Conservation of native flora and fauna of agro-biodiversity park in ANGRAU, Hyderabad, Andhra Pradesh, India

Deccan plateau region in India is unique due to presence of diversified geography and ecosystems with rich agricultural diversity including wild flora and fauna. However, it was over exploited by several anthropogenic activities. Acharya N.G. Ranga Agricultural University, Hyderabad has established first Agro-biodiversity Park in August, 2008 and is the first of its’ kind in India with a main objective of preserving, conserving and promoting the rich biodiversity of Deccan plateau region of Hyderabad. The park site is naturally spread with hillocks, boulders, undulated terrain with sloppy lands covered diverse vegetation besides a natural water tank. In the initial stage, the dangerous invasive alien species such as Partheniumhysterophorous, Lantana camera and Prosopis juliflora present in the vicinity were removed. Subsequently, several block plantations were developed with Teak and Mahua (70%) and forest mixed tree species (30%). Besides, separate generic blocks viz., palm and medicinal tree, mixed forest tree gardens and Ficus species diversity block were also developed. Of late, a rare, endemic, endangered and globally threatened species Ceropegia was identified in 2009. Since then, utmost care was taken for conservation in agro-biodiversity park. Water ponds and bodies were also created as a source of water for all resident and migratory bio-creatures for promotion of faunal genetic resources. At present, 24 species of insects, 5 species of fish and 8 species of reptiles were recorded. Out of 120 species of butterflies present in the Andhra Pradesh, 56 were found in this park.

Evaluating competitive interactions between trees in mixed forests in the Western Carpathians: Comparison between long-term experiments and SIBYLA simulations

The competition interactions between trees and species have already been thoroughly studied, but most often for mono-species and even-aged forests. Several recent studies have been undertaken, prompted by changes in forest management objectives, which now favour mixed-species forests to increase biodiversity. However, there have been no studies focused on the competition interactions for the mixed-species forests in the Western Carpathians. Recently, the single tree-based growth simulator SIBYLA has been developed for use in the forests of this area. The development of this model was based upon the growth simulator SILVA. Since there were no data available from long-term experiments for the Western Carpathian forests, SIBYLA was only calibrated using large-scale data from the Slovakian forest monitoring network. The aim of this study was (i) to define the potential maximum radial growth of silver fir (Abies alba L.), European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L. Karst.) in mixed forests, (ii) to test the above-ground competition effects on the radial increment of these species using a competition index based on competition light cone, and (iii) to evaluate the simulator SIBYLA using seven long-term experimental plots established in the 1960s, in the mixed-species uneven-aged forests of the Western Carpathians. These plots were repeatedly measured between five to eight times at intervals of 5–16years, from 1967 to 2010. Long-term climatic records were obtained to allow simulation of tree growth in real climatic conditions. The results showed the differences in potential maximum radial growth between the species. The results also suggested that the competition effect on radial increment predicted by the SIBYLA is an overestimate compared to the real observed effect on silver fir, Norway spruce, and European beech. This, together with other factors, is suggested to be the cause of the observed bias between measurements and SIBYLA simulations, which ranged from −2.2% to −11% for silver fir, −0.2 to −3.7% for Norway spruce, and 0.9% to 13.9% for European beech (average bias for the measurement periods).

Development of Fir Trees in Mixed Forests of Spruce, Fir and Beech (Piceeto-Abieti-Fagetum) on Mt. Ljubišnja

Development of Fir Trees in Mixed Forests of Spruce, Fir and Beech (Piceeto-Abieti-Fagetum) on Mt. Ljubišnja

Comparative study of additive basal area of conifers in forest ecosystems along elevational gradients

AbstractWe examined the basal area of two life forms (conifers vs. broadleaf trees) along elevational gradients on Yakushima Island, Japan and on two series of geological substrate on Mount Kinabalu, Borneo. On Yakushima, total stand basal area abruptly increased from 700 to 1,050 m in accordance with the high dominance of conifers, indicating the presence of additive basal area of conifers in conifer–broadleaf mixed forests at higher elevations (1,050–1,300 m). Along two substrate series on Kinabalu, some forests at higher elevations (1,860–3,080 m) showed relatively high dominance of conifers, but conifer basal area did not appear to be additive. Conifers were emergents above the canopy of broadleaf trees in mixed forests on Yakushima, but two life forms usually coexisted in the single‐story canopy in mixed forests on Kinabalu. Litterfall rate as a surrogate of productivity decreased with decreasing temperature along elevation on both the sites, but the rate of decrease was slower on Yakushima, where mixed forests at higher elevations showed relatively high rates. Thus, we suggest that additive basal area of conifers was linked to their emergent status, and that it enhanced productivity by complementary use of light by two life forms that occupy different stories. On Yakushima, typhoons are a major disturbance, but do not severely limit the height growth of conifers, allowing the development of two‐story mixed forests. On Kinabalu, a major disturbance is El Niño‐driven drought, and hydraulic limitation to tree height may explain the non‐additive and non‐emergent nature of conifers.

The in situ root chamber: A novel tool for the experimental analysis of root competition in forest soils

Summary Competition between the roots of mature trees in mixed forests is not well understood because adequate methods for studying this interaction under field conditions are not yet available. We present a novel root chamber (size: 90×70×30 mm) that allows growth monitoring of individual tree fine roots in the soil while altering root competition situations experimentally. Fine roots of mature trees that were carefully uncovered from the soil were allowed to grow for several months in the chamber which contained soil material from the root's close proximity. Fine root increment was quantified by optical root length determination at the beginning and the end of the experiment. By placing individual fine roots of a tree species together with a second conspecific or allospecific root, the chamber allows one to simulate conditions of intra- and interspecific competition, and to test hypotheses on intensity and direction of root competition in the soil of mixed forests. We investigated the applicability of the root chamber in a mature beech–oak mixed forest in which beech is known to be a superior competitor above-ground. One-hundred and six chambers with different combinations of beech and oak fine roots were exposed in the soil for 180 or 438 d. In two-species chambers, which contained one beech and one oak root allowing for interspecific competition, beech fine roots grew significantly faster than oak roots. Furthermore, beech roots tended to show a higher growth rate in two-species chambers than in single-species chambers (two beech roots: intraspecific competition). In contrast, oak roots tended to grow slower when placed together with beech than when growing together with oak. By expressing the competitive strength of beech and oak roots with the relative competition intensity (RCI) index, evidence of asymmetric interspecific root competition in favour of beech was obtained. The potentials of this technique are related to the fact that replicated experiments with fine roots of adult trees can be conducted in the field; a certain artificiality, which is inherent to all rhizosphere experiments, represents the main limitation. From this study we conclude that while there are some limitations, in situ root chambers represent an important step towards the experimental analysis of root competition in forests.

Analysis of forest vegetation of Morni hills in northeast Haryana

Morni hills which form a part of Siwaliks are located in north-east Haryana (30° 35′ to 34° 45′N and 70° 00′ to 75° 15′E) at an altitude of 1000 to 1200 m above the mean sea level. Vegetation analysis was undertaken in 3 forest types, i.e.Pinus roxburghii, mixed-deciduous forest and scrub.Anogeissus latifolia andLannea coromandelica were the dominant tree species in the mixed forest.Pinus roxburghii forest was monospecific andFlacourtia indica was dominant in scrub. Bioedaphic conditions influenced the performance of tree and shrub species, density of seedlings and saplings and herb layer composition. The density of trees in mixed forest,Pinus forest and scrub forest was 890, 1070 and 170 trees ha−1, respectively. Total basal cover of trees (m2 ha−1) was: 54·59, mixed forest; 42·05,Pinus forest; 8·20, scrub forest. The density of shrub varied from 8250–11050 plants ha−1.