Intermediary disturbance increases tree diversity in riverine forest of southern Brazil

Floods are frequently associated with disturbance in structuring riverine forests and they lead to environmental heterogeneity over space and time. We evaluated the distribution of tree species, ecological groups, species richness and diversity from the point bar to the slope of a riverside forest in southern Brazil (Lat. 30°01′S, Long. 52°47′W) to analyze the effects of flooding on soil properties and forest structure. A plot of 50 × 200 m divided in five contiguous transects of 10 × 200 m parallel to the river was installed, where we measured all the individual trees with pbh ≥ 15 cm. A detailed topographical and soil survey was carried out across the plot and indicated significant differences in organic matter and most mineral nutrients through the topographical gradient. The 1,229 surveyed individuals belonged to 72 species and 35 families. We used Partial CCA and Species Indicator Analysis to observe the spatial distribution of species. Both analyses showed that species distribution was strongly related to the flooding gradient, soil properties and also by space and pure spatial structuring of species and environmental variables (spatial autocorrelation), although a large part of variation remains unexplained. The ecological groups of forest stratification, plant dispersal and requirements for germination indicated slight differences among frequently, occasional and non-flooded transects. Species richness and diversity were higher at intermediate elevations and were associated to the increased spatial–temporal environmental heterogeneity. Across the plot, the direct influence of flooding on tree species distribution created a vegetation zonation that is determined by predicted ecological traits.     

Plant species diversity in abandoned coppice forests in a temperate deciduous forest area of central Japan

We investigated plant species diversity as it related to stand structure and landscape parameters in abandoned coppice forests in a temperate, deciduous forest area of central Japan, where Fagus crenata was originally dominant. The species occurring in the study plots were classified into habitat types based on a statistical analysis of their occurrence bias in particular habitats (e.g., primary forest, coniferous plantation) in the landscape studied. The relationships between stand structure, which reflected the gradient of management, and forest floor plant species diversity (H and J) and richness (number of species per unit area) were not significant. However, these factors did influence the forest floor plant composition of the different types of habitat. According to the multiple regression analysis, species diversity and the richness of forest floor plants was affected by landscape parameters rather than by stand structure. For trees, species richness was mainly affected by the relative dominance of F. crenata, which is one of the stand structure parameters that decreases with intensive management. This is probably because many of the tree species that are characteristic of coppice forests increase after F. crenata have been eliminated by management; these species are not dominant in the original forest, where they are suppressed by F. crenata, the shade-tolerant dominant species. The species diversity (H and J) of trees was positively correlated with some landscape parameters, including the road density around the study plot, which may be associated with the intensity of management activity. The number of disturbance-tolerant species increased with increasing road density. Stand structure mainly affected disturbance-intolerant forest floor plant species and disturbance-tolerant tree species. Thus, the species diversity responses differed between forest floor plants and trees. The impact of forest management on species diversity was more prominent for forest floor plants.     

Effects of river level fluctuation on plant species richness, diversity, and distribution in a floodplain forest in Central Amazonia

River levels in Central Amazonia fluctuate up to 14 m annually, with the flooding period ranging from 50 to 270 days between the rising and falling phases. Vast areas of forest along the rivers contain plant species that are well adapted to annual flooding. We studied the effect of flooding level on tree species richness, diversity, density, and composition in lake, river, and stream habitats in Jaú National Park, Brazil. 3051 trees >10 cm diameter (at 1.3 m diameter at breast height, dbh) were measured and identified in 25 10 m × 40 m randomly selected plots in each habitat. Ordination methods and analysis of variance results showed that forested areas near lakes had significantly lower species richness of trees than riverine and streamside habitats. Plot species richness and diversity were strongly negatively correlated with the water level and duration of flooding. The drier (stream) habitat had more total species (54 species of trees) and more unique species of trees (6 tree species) than the riverine (52 tree species; 3 unique species) and lake (33 tree species; 3 unique species) habitats. Species composition overlap among habitats was surprisingly high (42.6–60.6% overlap), almost one-third of the species were found in all three habitat types, and few species were unique to each habitat. We conclude that: (1) duration of flooding has a strong impact on species richness, diversity and plant distribution patterns; (2) most species are adapted to a wide range of habitats and flood durations; and (3) while flood duration may decrease local diversity, it also creates and maintains high landscape-scale diversity by increasing landscape heterogeneity. Received: 20 April 1997 / Accepted: 14 January 1999     

Impact of four silvicultural systems on birds in the Belgian Ardenne: implications for biodiversity in plantation forests

Uneven-aged management of conifer plantations is proposed as a way to increase the value of these forests for the conservation of bird diversity. To test this assumption, we compared the impact of four common silvicultural systems on bird communities, defined by cutblock size (large in even-aged silvicultural systems/smaller in uneven-aged silvicultural systems) and tree species composition (spruce/beech) in the Belgian Ardenne where beech forests have been replaced by spruce plantations. The abundances of bird species were surveyed in young, medium-aged and mature stands in 3–5 forests per silvicultural system (66 plots in all). The effect of silvicultural systems on bird species richness, abundance and composition were analysed both at the plot and at the silvicultural system levels. In plots of a given age, beech stands were richer in species. The composition of bird species at the plot level was explained by stand age and tree composition, but weakly so by stand evenness. For the silvicultural systems, bird species richness was significantly higher in even-aged and in beech forests, and bird species composition depended on the silvicultural system. This study emphasises the importance of maintaining native beech stands for birds and suggests that uneven-aged management of conifer plantations does not provide a valuable improvement of bird diversity comparatively with even-aged systems.     

Tree species diversity and forest structure in relation to microtopography in a tropical freshwater swamp forest in French Guiana

Diversity of tree association and forest structure were analysed in relation to microtopography and flooding intensity in a tropical freshwater swamp forest in the Sinnamary river basin, French Guiana. A 530-m-long vegetation transect was established through a hummock-hollow terrain. Nine 10 m× 50 m sample plots, perpendicular to the main transect, were located so that each was as microtopographically uniform as possible. Trees with dbh (diameter at 1.3 m) 10 cm were censused in all plots and trees with 2 cm dbh < 10 cm in three plots. Sixty tree species belonging to 39 genera and 30 families were recorded. The study area was divided into low and high sites according to microtopography and flooding intensity. According to the Czekanowski similarity matrix, the tree association in low, most frequently flooded, sites differed from that in the high sites under intermediate or low flooding intensity. The low sites had higher stand density and lower species richness than the high sites. Trees with dbh 10 cm in low sites were small and stand basal area (SBA) was about the same in low (69.6 m² ha^–1) and high (64.3 m² ha^–1) sites. The low areas were dominated by Pterocarpus officinalis (38% of stems with dbh 10 cm and 36% of SBA) and Malouetia tamaquarina (26 and 15%). Diospyros guianensis (13.4% of stems with dbh 10 cm and 6.1% of SBA), a Caraipa sp. (14.0 and 7.9%), Lecythis corrugata (6.6 and 3.5%) and emergent Caryocar microcarpum (0.9 and 13.9%) were abundant in high sites. Nodulated legume trees, P. officinalis, Hydrochorea corymbosa and Inga disticha, comprised 44% of stems in the low sites. The abundant nodulation suggests that symbiotic dinitrogen fixation may be an adaptation to N-depleted waterlogged soils. Other adaptive responses were litter accumulation between the buttresses of P. officinalis, which formed hummocks above surface water, and clonal growth habit of M. tamaquarina, which resulted in formation of monospecific groves in low sites.     

Natural channeling in riverine forests determines variations in their floristic composition,structure, and land use in southern Brazil

Hydrological processes in riparian forests affect their geomorphology and drainage, and define their structure. Interactions among many environmental variables and the tree community in continuous riverine forests affect their formation and add to their complexity, making our understanding of these habitats particularly challenging. We evaluated the tree species diversity and richness in relation to relief and flooding regimes in the watershed of a riparian forest in southern Brazil. The environments of the topographic gradients were classified according to relief and soil. Canonical correspondence analysis and indicator species analysis were used for the environmental classification. A detailed soil survey showed that the organic matter content and pH are quite distinct among the environmental categories. Frequent flooding of low intensity on the floodplain was associated with incipient and shallow channels, greater frequency of livestock encroachment, and lower frequency of shade-tolerant species dominance in the deep relief of the valleys and the headwaters. We conclude that there is a dynamic flow of species migration between the flooded and non-flooded environments in small channels and that the narrow deep channels in the floodplain with less frequent and intense flooding favor an expansion of the upland tree species into riparian areas, with channel shape and depth important variables in the impact of cattle encroachment on vegetation. The greatest tree diversity was found in the ravine habitats in the intermediate landscapes.

     

Do lianas shape ant communities in an early successional tropical forest?

Almost half of lowland tropical forests are at various stages of regeneration following deforestation or fragmentation. Changes in tree communities along successional gradients have predictable bottom‐up effects on consumers. Liana (woody vine) assemblages also change with succession, but their effects on animal succession remain unexplored. Here we used a large‐scale liana removal experiment across a forest successional chronosequence (7–31 years) to determine the importance of lianas to ant community structure. We conducted 1,088 surveys of ants foraging on and living in trees using tree trunk baiting and hand‐collecting techniques at 34 paired forest plots, half of which had all lianas removed. Ant species composition, β‐diversity, and species richness were not affected by liana removal; however, ant species co‐occurrence (the coexistence of two or more species in a single tree) was more frequent in control plots, where lianas were present, versus removal plots. Forest stand age had a larger effect on ant community structure than the presence of lianas. Mean ant species richness in a forest plot increased by ca. 10% with increasing forest age across the 31‐year chronosequence. Ant surveys from forest >20 years old included more canopy specialists and fewer ground‐nesting ant species versus those from forests <20 years old. Consequently, lianas had a minimal effect on arboreal ant communities in this early successional forest, where rapidly changing tree community structure was more important to ant species richness and composition.     

Forest floor plant diversity drives the use of mature spruce forests by European bison

The distribution of large ungulates in space is in large extent driven by the availability of forage, which in temperate forests depends on light availability, and associated plant diversity and cover. We hypothesized that the increased number of GPS fixes of European bison (Bison bonasus L.) in usually avoided spruce forests was an effect of higher plant species richness and cover of the forest floor, which developed owing to increased light availability enhanced by spruce mortality. We carried out 80 forest floor plant surveys combined with tree measurement on plots chosen according to the number of GPS locations of GPS‐collared European bison. The mean plant species richness per plot was higher on intensively visited plots (IV) than rarely visited (RV) plots (30 ± 5.75 (SD) versus. 26 ± 6.19 (SD)). The frequency of 34 plant species was higher on IV plots, and they were mainly herbaceous species (32 species), while a significant part of 13 species with higher frequency on RV plots was woody plants (5 species). The species richness of forbs was higher on IV plots, while other functional groups of plants did not differ. Tree stem density on the IV plots was lower than on the RV plots (17.94 ± 6.73 (SD) versus 22.9 ± 7.67 (SD)), and the mean value of Ellenberg's ecological indicator for light availability for all forest floor plant species was higher on IV plots. European bison visiting mature spruce forests was driven by higher forest floor plant cover and species richness, and high share and species richness of forbs. The two latter features may be translated into higher quality and diversity of forage. In spite of morphological characteristics suggesting that European bison is a species of mixed (mosaic) habitats, it seems to be well adapted to thrive in diverse forests.     

Impact of Flooding on the Species Richness, Density and Composition of Amazonian Litter-Nesting Ants

Litter-nesting ants are diverse and abundant in tropical forests, but the factors structuring their communities are poorly known. Here we present results of the first study to examine the impact of natural variation in flooding on a highly diverse (21 genera, 77 species) litter-nesting ant community in a primary Amazonian forest. Fifty-six 3 × 3 m plots experiencing strong variation in flooding and twenty-eight 3 × 3 m terra firme plots were exhaustively searched for litter-nesting ants to determine patterns of density, species richness and species composition. In each plot, flooding, litter depth, twig availability, canopy cover, plant density, percent soil nitrogen, carbon, and phosphorus were measured. Degree of flooding, measured as flood frequency and flood interval, had the strongest impact on ant density in flooded forest. Flooding caused a linear decrease in ant abundance, potentially due to a reduction of suitable nesting sites. However, its influence on species richness varied: low-disturbance habitat had species richness equal to terra firme forest after adjusting for differences in density. The composition of ant genera and species varied among flood categories; some groups known to contain specialist predators were particularly intolerant to flooding. Hypoponera STD10 appeared to be well-adapted to highly flooded habitat. Although flooding did not appear to increase species richness or abundance at the habitat scale, low-flooding habitat contained a mixture of species found in the significantly distinct ant communities of terra firme and highly flooded habitat.
     

Seasonally flooded,and terra firme in northern Congo: Insights on their structure,diversity and biomass

In the Congo basin, considerable uncertainty remains about the amount and spatial variation of carbon stocks. We studied two types of seasonally flooded forests (dominated by Guibourtia demeusei and Lophira alata) and nearby terra firme forests in northern Congo. We sampled 1.25 ha per forest type and a total of 1,400 trees ≥5 cm diameter. AGB ranged from 207–343 Mg/ha, with no significant differences between forest types. Few significant differences were observed in vegetation structure or tree diversity between forest types. Species richness and stem density of small trees were lower, and dominance was higher in Guibourtia plots, which are subject to greater flooding than Lophira plots. Guibourtia was absent from smaller diameter class in Guibourtia forests; and Uapaca spp. were more abundant in terra firme than in seasonally flooded plots. We show that both types of seasonally flooded forests store important quantities of AGB and should also be considered in forest conservation programmes. We recommend more research on seasonally flooded forests, on larger geographical extent, which assesses flood depth and duration, and measures tree height in the field, as we took a conservative approach to AGB estimates, and AGB could be even greater than we report here.     

Whinchat Saxicola rubetra reproductive success according to hay cutting schedule and meadow passerine density in alluvial and upland meadows in France

In France, whinchat Saxicola rubetra populations now rarely breed at altitudes below 1,000 m except in flooded alluvial plains. Whinchat reproductive success, the timing of haymaking and meadow bird density were assessed in 2003 in six areas selected in three different flooded plains, in five areas from two massifs at altitudes ranging from 990 to 1,250 m, and in 2004 in six areas of three flooded plains, in seven areas from three massifs at altitudes ranging from 1,200 to 2,000 m. The percentage of whinchat territories in which juveniles were observed was negatively correlated with mown areas at the time when 80% of hatched broods (observation of prey carryings by adults) would theoretically be fledged. Additionally, assessed hatching success was negatively correlated with early haymaking in 2003 and with meadow passerine territory density in 2004. In upland meadows, whinchat populations exhibited either low reproductive success and low density (1,200 m) or high reproductive success and high density (1,200 m). In lowland flooded meadow however, high density could match low reproductive success and whinchat population then acts as a sink population. We conclude that adequate agri-environmental policy should not focus only on lowland meadows, even if the highest meadow bird diversity is often found there.     

Effects of population density on forest structure and species richness and diversity of trees in Kampong Thom Province, Cambodia

This study examined differences in stand structure, tree species richness, and tree species diversity in relation to population density in Kampong Thom Province, Cambodia. Tree data were obtained from a 1997 forest inventory involving 60 clusters (540 plots) systematically distributed over 30% of the provincial forest area. Spatially referenced population data were obtained from the 1998 national population census. The average number of trees per cluster was 356/ha, the average basal area, 23 m²/ha, the average stand volume, 217 m³/ha, and the average aboveground biomass, 273 Mg/ha for all trees of DBH 10 cm and larger. The average species richness per cluster was 37 species, while average species diversity was measured as 0.916 using Simpson’s index and 2.98 by Shannon’s index. Significant negative correlations were generally found between population density surrounding clusters and tree density, basal area, stand volume, aboveground biomass, and species richness and diversity for three examined diameter classes (DBH of 10–30, ≥30, and ≥10 cm). As the distance from clusters for calculating population density increased, the correlation levels increased up to 5 or 7 km, depending on the variables and diameter class, and then stayed relatively constant for stand structure variables and decreased for species richness and diversity. The results indicate that evidence of disturbance was more pronounced at higher population density up to around 5 to 7 km. We suggest that introduction of greater controls on human disturbance should be a high priority for resource management and conservation in Kampong Thom Province and, presumably, Cambodia as a whole.     

Tree species composition and diversity gradients in white-water forests across the Amazon Basin

Aim Attention has increasingly been focused on the floristic variation within forests of the Amazon Basin. Variations in species composition and diversity are poorly understood, especially in Amazonian floodplain forests. We investigated tree species composition, richness and α diversity in the Amazonian white‐water (várzea) forest, looking particularly at: (1) the flood‐level gradient, (2) the successional stage (stand age), and (3) the geographical location of the forests. Location Eastern Amazonia, central Amazonia, equatorial western Amazonia and the southern part of western Amazonia. Methods The data originate from 16 permanent várzea forest plots in the central and western Brazilian Amazon and in the northern Bolivian Amazon. In addition, revised species lists of 28 várzea forest inventories from across the Amazon Basin were used. Most important families and species were determined using importance values. Floristic similarity between plots was calculated to detect similarity variations between forest types and over geographical distances. To check for spatial diversity gradients, α diversity (Fisher) of the plots was correlated with stand age, longitudinal and latitudinal plot location, and flood‐level gradient. Results More than 900 flood‐tolerant tree species were recorded, which indicates that Amazonian várzea forests are the most species‐rich floodplain forests worldwide. The most important plant families recorded also dominate most Neotropical upland forests, and c. 31% of the tree species listed also occur in the uplands. Species distribution and diversity varied: (1) on the flood‐level gradient, with a distinct separation between low‐várzea forests and high‐várzea forests, (2) in relation to natural forest succession, with species‐poor forests in early stages of succession and species‐rich forests in later stages, and (3) as a function of geographical distance between sites, indicating an increasing α diversity from eastern to western Amazonia, and simultaneously from the southern part of western Amazonia to equatorial western Amazonia. Main conclusions The east‐to‐west gradient of increasing species diversity in várzea forests reflects the diversity patterns also described for Amazonian terra firme. Despite the fine‐scale geomorphological heterogeneity of the floodplains, and despite high disturbance of the different forest types by sedimentation and erosion, várzea forests are dominated by a high proportion of generalistic, widely distributed tree species. In contrast to high‐várzea forests, where floristic dissimilarity increases significantly with increasing distance between the sites, low‐várzea forests can exhibit high floristic similarity over large geographical distances. The high várzea may be an important transitional zone for lateral immigration of terra firme species to the floodplains, thus contributing to comparatively high species richness. However, long‐distance dispersal of many low‐várzea trees contributes to comparatively low species richness in highly flooded low várzea.     

Vegetation and environmental heterogeneity relationships in a Neotropical swamp forest in southeastern Brazil (Itirapina, SP)

Patterns in substrate, canopy openness, tree species composition and structure were studied in a swamp forest in southeastern Brazil (Itirapina, SP), using a fine spatial scale (∼0.05 km²). Sixty quadrats of 10 m × 10 m were divided into three sample plots, located in the centre and at both ends of the forest remnant (upstream and downstream), encompassing different environmental conditions. In each quadrat we quantified and identified individuals with CBH (circumference at breast height) ≥ 10 cm, the chemical properties of the soil, the drainage (flooded area) and the percentage of canopy openness. We keep 5124 individuals distributed over 37 species and 25 families. The downstream site presented a lower frequency of flooding, canopy openness, species richness (15 species) and density of individuals. In the central site we found different patterns of drainage and light incidence, the greatest species richness (31 species) and density of individuals, but smaller trees both in height and in diameter. The upstream site was subject to higher frequency of flooding, with intermediate values for density and species richness (27 species). Floristic and structural variation between and within sites reflects the different environmental conditions related to substrate and canopy openness. However, a larger number of species were correlated with drainage pattern (21 species) rather than with canopy openness (14 species), suggesting that the main factor responsible for the spatial organization of the plant community in swamp forests is soil drainage.     

Plant biodiversity and conservation of tropical semi-evergreen forest in the Shervarayan hills of Eastern Ghats, India

Species diversity, density, population structure and dispersion patterns of all trees and lianas (30cm gbh) were inventoried in a tropical semi-evergreen forest in the Shervarayan hills of Eastern Ghats, south India. Such data are necessary for ecosystem conservation of the under-studied Eastern Ghats, as extensive forests here have already been converted to coffee and orange plantations and the landscape changed due to aluminium ore mining and quarrying. Four 1-ha plots were established in Sanyasimalai (SM) reserve forest of the Shervarayan hills, one plot (SM1) located close to mining and quarrying area, two other contiguous plots (SM2 and SM3) located in selective felling area and the fourth (SM4) in a relatively undisturbed forest. These are 1 to 4km apart in the same semi-evergreen forest tract. In the four study plots a total of 3260 stems (mean density 815ha–1) covering 80 species in 71 genera and 44 plant families were recorded. Species richness was greatest in the undisturbed plot SM4 (50), while lowest (33) in the selectively felled site SM2. The forest stand (SM4) was also denser (986 stemsha–1) and more voluminous (basal area 44.3m2ha–1 as compared with the site mean of 35m2ha–1) than the other plots. Four trees, Chionanthus paniculata, Syzygium cumini, Canthium dicoccum and Ligustrum perrottetii dominated the stand, collectively contributing to >50% of the total density. Species richness and stand density decreased with increasing tree girths. The forest stand contained a growing population, but there was considerable variation in basal area distribution between the plots. Trends in species population structure varied, particularly for selective-felled species. Most species exhibited clumped dispersion of individuals both at 0.25ha and 1-ha scales. Variation in plant diversity and abundance are related to site attributes and human impacts.     

Flooding × tree fall gap interactive effects on blackwater forest floristics and physical structure in the Peruvian Amazon

To better understand how flooding and tree fall structure forests in the Amazon, I sampled vegetation plots within three blackwater forests (least flooded, medium flooded, highest flooded) and their tree fall gaps in the Peruvian Amazon. I found (1) increased flooding decreased family richness in the closed-canopy forests but increased it in their gaps, with no trends for no. of unique species, (2) flooding decreased stem size everywhere as did the number of stems as size increased especially for larger stems, (3) Green's index showed clumping only for least-flooded forests with the closed-canopy forest showing more than its tree fall gap, and (4) both flooding and tree fall gap creation decreased canopy coverage perhaps as an additive effect. Further among the stem size classes, only the smallest stems were significantly affected by openness and by type of forest, with a significant interaction term where flooding significantly decreased the number of these smaller stems in all forests and their gaps, except those with the highest level of flooding. Also tree fall gaps had significantly more, smaller stems than their forests in the two most-flooded forests, but not in the least-flooded forest. I conclude that flooding is a greater stressor and influence on the structure of these forests than tree fall, and so, in these forests, gradients and disturbances overlap in their traditional roles.     

Synthesis and characterization of a crosslinked chitosan derivative with a complexing agent and its adsorption studies toward metal(II) ions

A new chitosan derivative has been synthesized by crosslinking a metal complexing agent, [6,6′-piperazine-1,4-diyldimethylenebis (4-methyl-2-formyl) phenol] (L), with chitosan (CTS). The resulting material (CCTSL) was characterized by elemental (CHN), spectral (FTIR and solid-state NMR), thermal (TGA and DTA), and structural (powder XRD and SEM) analyses. Adsorption experiments (pH dependency, kinetics, and equilibrium) of CCTSL toward various metal ions such as Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II) were carried out at 25 °C. The results showed that the adsorption was dependent on the pH of the solution, with a maximum capacity between pHs 6.5 and 8.5. The kinetics was evaluated by applying the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The maximum adsorption capacity was 1.21 mmol g⁻¹ for Cu(II) and the order of adsorption capacities for the metal(II) ions studied was found to be Cu(II) > Ni(II) > Cd(II)  Co(II)  Mn(II)  Fe(II)  Pb(II).     

Plant communities affect the species–area relationship on Carex sempervirens tussocks

The species–area relationship (SAR) has been extensively studied in a wide range of plant communities, but very few studies have directly addressed how plant communities affect the SAR and what are the underlying mechanisms. Many graminoids form distinct tussocks where many other plant species grow, but no study has investigated whether the SAR holds true for the vegetation on tussocks. In four plant communities on an abandoned subalpine pasture in the Swiss National Park, we made releves on 600 tussocks of Carex sempervirens and measured tussock basal area and other tussock traits. In all four communities, species richness on C. sempervirens tussocks was strongly positively related to tussock basal area (R²0.74), while other tussock traits explained very little (R²<0.04). Slope and intercept of the SAR on C. sempervirens tussocks differed significantly among the four communities. This was because plant communities affected richness in smaller tussocks (basal diameter <10 cm) but not that in large tussocks (basal diameter10 cm). We conclude that the SAR holds true for vegetation on C. sempervirens tussocks and changes with plant communities. Changes in the SAR on C. sempervirens tussocks are very likely because smaller tussocks are less independent of the plant communities than the larger ones, regarding disturbance or nutrients.     

Disentangling Biodiversity and Climatic Determinants of Wood Production

Background

Despite empirical support for an increase in ecosystem productivity with species diversity in synthetic systems, there is ample evidence that this relationship is dependent on environmental characteristics, especially in structurally more complex natural systems. Empirical support for this relationship in forests is urgently needed, as these ecosystems play an important role in carbon sequestration.

Methodology/Principal Findings

We tested whether tree wood production is positively related to tree species richness while controlling for climatic factors, by analyzing 55265 forest inventory plots in 11 forest types across five European countries. On average, wood production was 24% higher in mixed than in monospecific forests. Taken alone, wood production was enhanced with increasing tree species richness in almost all forest types. In some forests, wood production was also greater with increasing numbers of tree types. Structural Equation Modeling indicated that the increase in wood production with tree species richness was largely mediated by a positive association between stand basal area and tree species richness. Mean annual temperature and mean annual precipitation affected wood production and species richness directly. However, the direction and magnitude of the influence of climatic variables on wood production and species richness was not consistent, and vary dependent on forest type.

Conclusions

Our analysis is the first to find a local scale positive relationship between tree species richness and tree wood production occurring across a continent. Our results strongly support incorporating the role of biodiversity in management and policy plans for forest carbon sequestration.