Tree Basal Area Research Articles

Soil pH and Organic Carbon Properties Drive Soil Bacterial Communities in Surface and Deep Layers Along an Elevational Gradient.

Elevational gradients strongly affect the spatial distribution and structure of soil bacterial communities. However, our understanding of the effects and determining factors is still limited, especially in the deep soil layer. Here, we investigated the diversity and composition of soil bacterial communities in different soil layers along a 1,500-m elevational gradient in the Taibai Mountain. The variables associated with climate conditions, plant communities, and soil properties were analyzed to assess their contributions to the variations in bacterial communities. Soil bacterial richness and α-diversity showed a hump-shaped trend with elevation in both surface and deep layers. In the surface layer, pH was the main factor driving the elevational pattern in bacterial diversity, while in the deep layer, pH and soil carbon (C) availability were the two main predictors. Bacterial community composition differed significantly along the elevational gradient in all soil layers. In the surface layer, Acidobacteria, Delta-proteobacteria, and Planctomycetes were significantly more abundant in the lower elevation sites than in the higher elevation sites; and Gemmatimonadetes, Chloroflexi, and Beta-proteobacteria were more abundant in the higher elevation sites. In the deep layer, AD3 was most abundant in the highest elevation site. The elevational pattern of community composition co-varied with mean annual temperature, mean annual precipitation, diversity and basal area of trees, pH, soil C availability, and soil C fractions. Statistical results showed that pH was the main driver of the elevational pattern of the bacterial community composition in the surface soil layer, while soil C fractions contributed more to the variance of the bacterial composition in the deep soil layer. These results indicated that changes in soil bacterial communities along the elevational gradient were driven by soil properties in both surface and deep soil layers, which are critical for predicting ecosystem functions under future climate change scenarios.

Fruit trees drive small‐scale movement of elephants in Kibale National Park, Uganda

AbstractUnderstanding what motivates animal spatial behavior requires discerning the relationship between animals and the landscape in which they move. Many studies have focused on large scale trends that drive migrations and movement across broad landscapes, but few studies have focused on drivers of local movement within smaller areas based on fine‐scale landscape heterogeneity. This is especially true for African elephants (Loxodonta africana), whose movements in relation to landscape variables have frequently been studied across vast areas, but infrequently on a small scale. We report on how the local distribution of an important resource—fruit trees—shapes elephant movement patterns in Kibale National Park, Uganda. We hypothesized that the spatial location of elephant trails, and especially intersections in the network of trails, would be heavily associated with fruit trees, with trail density being higher in areas with greater fruit availability. Elephant trails and nearby fruit trees were mapped within a 64 km2 area within the interior of the Park. Trail and fruit tree sampling were conducted along 16 evenly spaced one‐km control transects and compared to 28.6 km of elephant trails arrayed throughout the park. Fruit tree basal area was higher along trails and at trail intersections. Trail density was also positively correlated with fruit tree density. Fruit trees may thus serve as a determinant of small‐scale elephant movement and could be used to predict patterns of elephant spatial behavior across forested habitat, which has potential implications for elephant management in the area.

Ericoid mycorrhizal shrubs alter the relationship between tree mycorrhizal dominance and soil carbon and nitrogen

Abstract Plant–fungal associations strongly influence forest carbon and nitrogen cycling. The prevailing framework for understanding these relationships is through the relative abundance of arbuscular (AM) versus ectomycorrhizal (EcM) trees. Ericoid mycorrhizal (ErM) shrubs are also common in forests and interactions between co‐occurring ErM shrubs and AM and EcM trees could shift soil biogeochemical responses. Here we test hypotheses that the effects of ErM shrubs on soil carbon and nitrogen either extend or are redundant with those of EcM trees. Using regional vegetation inventory data (>3,500 plot observations) we evaluated the frequency, richness and relative abundance of ErM plants in temperate forests in the eastern United States and examined their relationship with EcM plant cover. We then used surface soil (7 cm) data from 414 plots within a single forest to analyse relationships between ErM plant cover, relative EcM tree basal area and soil carbon and nitrogen concentrations while accounting for other biogeochemical controls, such as soil moisture. At both scales, we found a positive relationship between ErM and EcM plants, and the majority of ErM plants were in the shrub layer. Within the forest site, ErM plants strongly modulated tree mycorrhizal dominance effects. We found negative relationships between EcM relative basal area and soil carbon and nitrogen concentrations, but these relationships were weak to negligible in the absence of ErM plants. Both EcM relative basal area and ErM plant cover were positively associated with the soil carbon‐to‐nitrogen ratio. However, this relationship was driven by relatively lower nitrogen for EcM trees and higher carbon for ErM plants. As such, the functional effects of ErM plants on soil biogeochemistry neither extended nor were redundant with those of EcM trees. Synthesis. We found that ErM shrubs strongly influenced the relationship between tree mycorrhizal associations and soil biogeochemistry, and the effects of ErM shrubs and EcM trees on carbon and nitrogen were functionally distinct. Our findings suggest that ErM shrubs could confound interpretation of AM versus EcM tree effects in ecosystems where they co‐occur but also bolster growing calls to consider mycorrhizal functional types as variables that strongly influence forest biogeochemistry.

Further considerations concerning CAVAT

ABSTRACT The amenity tree valuation method CAVAT apparently gives reduced weight to future benefits, similarly to discounting. Discounting future conditions allows calculation of a value per year per square centimetre of tree basal area, on the premise that tree planting was rationally done. The resulting value ascribed to a target tree is much lower than that calculated by CAVAT. CAVAT’s value is the same as given by the “rational” procedure if trees were predicted not to grow. The “rational” perspective provides a reasoned estimate of CAVAT’s avowed objective of calculating a compensation replacement value for lost trees. CAVAT itself seemingly calculates over-generous compensation. The “rational” protocol’s apparently low value may be adjusted upwards to recognise incomplete planting survival, conditions of high cost, overheads and, sometimes, defective discounting. These, and any neglect of the value of subsequent replanting and of people’s particular associations with trees, may undervalue fair financial recompense, especially when no compensation planting is made. However, some of these factors would revise CAVAT values upwards too, so the gap between outcomes might remain. Neither protocol translates from a cost basis to a full amenity benefit of trees.

Natural factors but not anthropogenic factors affect native and non–native mammal distribution in a Brazilian National Park

Protected areas, designed for biodiversity conservation, are currently affected by invasive species as most of them have documented biological invasions. This study aimed to test whether non–native mammal species richness influences the local distribution of native mammals and how distance from human settlement, elevation and vegetation characteristics influence native and non–native mammal richness in a national park in Brazil.We recorded 20 mammal species in the park, 17 native species and three non–native species. Native mammal richness was higher at intermediate elevations and in forests with lower tree densities and tree basal area. Non–native mammal richness was greater at higher elevations and in forests with low tree densities. Non–native mammals did not influence native mammal presence. In conclusion, the distribution of both native and non–native mammal species was affected by elevation and vegetation but not by distance from human settlements or non–native mammal presence.

Growth Assessment of Tree Species Growing in the Amhara Region in Ethiopia

ABSTRACT Ethiopian mixed forests have multipurpose benefits and services. However, there is a gap of information in the entire Ethiopian highlands on forest growth needed for implementation of sustainable forest management and provision of ecosystem services. Therefore, main aim of this study was to identify main factors deriving tree growth in forest and woodland in Amhara Regional State of Ethiopia and to provide an individual tree basal area increment (BAI) model based on increment cores. The data came from 170 sampling plots in study area and cover 51 tree species. For each tree species, diameter at breast height (DBH), height, increment core measurement, tree location, and distance from subject tree measurements were recorded. Because of large number of trees species, it is difficult to develop growth functions for each individual tree species. Thus, classification of species groups provided a framework to organize information that differs between vegetation types. Our classification resulted in three groups. For each tree species group, an individual tree BAI model was calibrated. The tree species group of BAI differs by DBH class. The response to BAI depends on competitive condition of a tree. This growth model can be used to predict tree growth for Ethiopian mixed-species forests.

Interactions between local and global drivers determine long‐term trends in boreal forest understorey vegetation

AbstractAimGlobal change effects on forest ecosystems are increasingly claimed to be context dependent, indicated by interactions between global and local environmental drivers. Most examples of such context dependencies originate from temperate systems, while limited research comes from the boreal biome. Here we set out to test if interactions between climate warming, nitrogen deposition, land‐use change resulting in increasing forest density, and soil pH drive long‐term changes in understorey vegetation in boreal forests.LocationSweden.Time period1953–2012.Major taxa studiedVascular plants.MethodsWe used long‐term (50 years) National Forest Inventory data on forest understorey vegetation in Sweden to model the combined effects of climate warming, nitrogen deposition, increase in forest density (tree basal area), and soil pH.ResultsOur results identify increasing temperature, nitrogen deposition and denser, shadier forest conditions as the main drivers of understorey vegetation changes during this time period. More importantly, we found that these effects varied with local conditions, that is, that the change towards a more nitrophilic understorey vegetation was more pronounced at low than high soil pH. Forest density was an important modulator of nitrogen deposition and temperature increase, with effects generally decreasing with density. Decreased cover of ericaceous dwarf shrubs was driven by both forest density and nitrogen deposition, with a stronger effect at low than at high pH.Main conclusionsOur results highlight that to understand forest ecosystems’ response to global change, and to make adequate management decisions to mitigate the effects of global change, we need to understand how changes in local environmental factors (forest density and soil pH) interact with global‐scale drivers (nitrogen deposition and climate warming). Neglecting such interactions will lead to incorrect estimations of effects. In our case, we would for example, have underestimated the eutrophication effects on acid soils, which constitute a considerable part of the boreal biome.

Assessing fruit production and harvesting effects on Carapa procera DC. population, a threatened oil tree in Burkina Faso, West Africa

The exploitation of non-timber forest products contributes considerably to local livelihoods for subsistence in developing countries. The study aims to assess the structure and fruit production of C. procera natural populations in harvesting and non-harvesting sites and to compare the structure characteristics and fruits yields of the two sites.The study was carried out in Burkina Faso on both, harvesting and non-harvesting sites. Eighty fruits bearing trees (40 per site) were sampled, from each, all the fruits were counted. Dendrometric parameters were measured in 80 plots of 1000 m². In each plot, diameter at breast height (dbh) and total height of trees were measured. Density, basal area, mean diameter and height were computed for each site. Analyses of variance were performed to test differences between sites based on measured variables. Weibull theoretical model was used on size class distribution to analyze trees structure in both sites.The results showed that the production of fruits reaches a mean of 6462.73 ± 4237.51 fruits/ha and 9103.44 ± 7631.88 fruits/ha, respectively in non-harvesting and harvesting site. Significant differences (p < 0.05) were found for tree densities, basal area and tree height between sites with highest values in the harvesting site. The size class distribution of trees showed in both sites the existing of potential regeneration with the dominance of young trees (1 < c < 2) with some survival difficulties during the growth stages. C. procera populations exhibit a high potential of fruit production and natural regeneration but are influenced by pressures impact.

Exploring the biotic homogenization and diversity resistance hypotheses: The understorey of non‐native and native woodland canopies in three urban areas of Europe

AbstractAimExploring the biotic homogenization and diversity resistance hypotheses by assessing the effect of non‐native black locust canopy on understorey species turnover.LocationBerlin, the Venetian metropolitan area, and Rome.MethodsWe modelled the zeta (ζ) expression of diversity to compare the understorey species turnover between the non‐native black locust and native woodland canopies across multiple sites and through predictors of anthropogenic pressure (road and built‐up density) and interior conditions (tree basal area and mean height).ResultsIn Rome, black locust showed the lowest survivability and cover and did not produce any homogenization of the understorey. In Berlin and in the Venetian metropolitan area, black locust caused understorey homogenization, although with a lower intensity in Berlin. Under black locust canopies, distance between sites and road density was more consistently associated with species turnover, across urban areas and multiple sites. Under native canopies in Berlin, factors prominently associated with species turnover were road and built‐up density and mean tree height, while in the Venetian metropolitan area it was road density.Main conclusionsEvidence in support of the biotic homogenization in contrast to the diversity resistance hypothesis varied across urban areas. Species turnover was influenced by land use patterns more evidently under native tree canopies and where the non‐native tree had higher survivability. Similar analyses in other urban areas may confirm these relationships with other types of landscapes.

Tree-size dimension inequality shapes aboveground carbon stock across temperate forest strata along environmental gradients

It is generally well-explored that overstorey stratum regulates understorey stratum through the dominant role over the available resources in forests. However, the relationships amongst topography, soil nutrients, species diversity, tree-size dimension inequality and aboveground carbon (AGC) stock across forest strata remain debated in forest ecosystems. Here, we assumed that soil nutrients, species diversity and tree-size dimension inequality promote AGC stock in overstorey stratum, which in turn regulate AGC stock in understorey stratum in natural temperate forests. To do so, using several structural equation models (SEMs) on the data from 104 temperate forest plots in Northern Iran, we assessed the effects of tree-size dimension inequality as well as the individual effects of either inequality in tree diameter, height, basal area, crown volume, or crown area, species diversity, soil nutrients and topographic factors on AGC in each forest stratum and at whole-community level as well as the effects of overstorey on understorey (i.e., joint SEMs). Results show that AGC stock in overstorey stratum was mainly determined by tree-size dimension inequality rather than by species diversity on nutrient-rich soils but controlled by topographic factors related to light availability. In understorey stratum, only basal area inequality was the strong driver of AGC stock, but overstorey overruled the effects of understorey drivers on understorey AGC stock. Specifically, overstorey tree-size dimension inequality increased but AGC stock decreased the AGC stock of understorey. The observed mechanism and effects at overstorey stratum were nearly similar to whole-community level. This study shows that overstorey stratum regulates understorey through dominant occupancy on the light availability and soil nutrients. We suggest that integrative modeling of overstorey and understorey strata based on tree height, diameter and crown inequality may better enhance our understanding and extend the existing debate based on multiple drivers of forest functioning, which may help to provide specific guidelines for forest management.

Disentangling the Relationship between Tree Biomass Yield and Tree Diversity in Mediterranean Mixed Forests

Tree biomass and the diversity relationship in mixed forest have an impact on forest ecosystem services provisions. Tree biomass yield is driven by several aspects such as species identity, site condition, stand density, tree age and tree diversity expressed as species mingling and structural diversity. By comparing diverse degrees of tree mixtures in natural forests, we can gain insight into the ecosystem services provision level and dynamic. Two monitoring sites in the Castilian Northern Plateau (Spain) have been analyzed to disentangle the relationships between biodiversity levels and tree biomass yield. Two permanent one hectare (ha) squared plots were established at Llano de San Marugán and Valdepoza. In each plot, all individual trees were measured (diameter and height), georeferenced and its species identity defined. Tree species in the two sites were Pinus sylvestris, Pinus nigra, Pinus pinea, Quercus pyrenaica, Quercus ilex, Quercus faginea and Juniperus thurifera. From these datasets, ten diversity indices that fall in three categories (species richness indices, species compositional/mingling indices and vertical structural indices) were used as predictor variables to fit several candidate models. By merging the trees by site (without considering the species identity) selected models include individual tree basal area as an explanatory variable combining by addition or interaction with diversity indices. When species are analyzed independently, structural diversity impacts on biomass yield in combination (additive or multiplicative) with tree size is negative for Pinus nigra and positive for the other species.

Management and climate variability effects on understory productivity of forest and savanna ecosystems in Oklahoma, USA

AbstractThe productivity of herbaceous and understory woody vegetation is critical for wildlife habitat, livestock forage, and biodiversity, and is influenced by both annual weather patterns and tree dominance. With the goals to inform management and understand climate change implications, we determined the effects of tree harvest, prescribed fire, and 31 yr of climate variability on understory aboveground net primary productivity (ANPP) for ecosystems ranging from mature forest to grassland in a long‐term study in southeastern Oklahoma, USA. In 1984, starting with a mature forest dominated by Pinus echinata and Quercus stellata, replicated experimental units were created by various combinations of pine harvest, hardwood thinning, and subsequent fire return intervals (1–4 yr and none). Understory ANPP (forbs, grasses, and woody plants) was measured by clip plots at the end of each growing season. Stepwise regression models were developed between understory ANPP and tree basal area, litter accumulation, fire return interval, and monthly, seasonal, and annual weather variables. Understory ANPP was dominated by grasses and ranged from 27 g·m−2·yr−1 for the mature forest to 374 g·m−2·yr−1 for an annually burned grassland/savanna. In general, herbaceous ANPP was inversely related to tree dominance (basal area), litter accumulation, and early and late growing season temperatures, and positively related to June precipitation. Understory woody ANPP was influenced by tree basal area, positively influenced by precipitation, and negatively influenced by summer soil moisture deficits. Our results indicate that prescribed fire, through its negative influence on tree basal area and litter accumulation, is critical to maintaining highly productive understories and that a three‐year return interval is a threshold to stall redevelopment of forest. For herbaceous ANPP, timing of precipitation, especially mid‐growing season, appears more important than total precipitation, and higher temperatures within the range our site experienced did not have a large negative effect. In contrast, understory woody ANPP was negatively influenced by drought indicating climate change may have variable effects on different functional groups.

Multiple drivers of tree and soil carbon stock in the tropical forest ecosystems of Bangladesh

Tropical forest ecosystem act as a carbon sink and plays a vital role in climate change mitigation. The carbon storage capacity of tropical forest ecosystems is declining gradually in recent years. But studies regarding the multiple drivers of tree and soil carbon in the tropical forest ecosystems are scarce. Our study aims to quantify the tree and soil carbon storage capacity and to explore how these carbon storages are associated with both biotic (stand structure, anthropogenic disturbance) and abiotic drivers (climate, topography, and soil) simultaneously in tropical forest ecosystems. The present study was conducted in two forest-protected areas of Bangladesh, namely- Satchari National Park (SNP), and Khadimnagar National Park (KNP). Results showed that tree carbon stock was 72.9 t ha−1 and 58.2 t ha−1 in SNP and KNP, respectively. Besides, soil carbon was 77.1 t ha−1 in SNP and 130.5 t ha−1 in KNP. We found that tree carbon was positively correlated with all stand structure parameters. However, soil carbon was negatively correlated with tree richness, height, and basal area. Anthropogenic disturbance had a negative correlation with tree carbon and a positive correlation with soil carbon stock. No significant correlation was observed between tree carbon and local climatic parameters. But soil carbon had a positive correlation with annual precipitation and a negative correlation with annual mean temperature. Furthermore, tree carbon was positively associated with elevation and slope whereas soil carbon was negatively associated with elevation. Tree carbon was negatively correlated with silt% but positively with sand%. Conversely, soil carbon showed significant positive associations with soil moisture, bulk density, soil pH, and soil silt%. Our study provides a comprehensive insight on the understandings of key drivers of tree and soil carbon storage in the tropical forest ecosystem of Bangladesh. We concluded that anthropogenic disturbance and stand characteristics regulate tree carbon stock while soil carbon is mainly associated with local climate and soil properties in the studied tropical forest ecosystems.

Individual tree basal area increment model for sessile oak (Quercus petraea (Matt.) Liebl.) in coppice-originated stands.

In this study, the basal area increment models were developed to be both age dependent and independent with a stepwise multiple regression analysis for coppice-originated pure sessile oak stands in the Marmara region, which is located in north-western Turkey. Data was obtained from a total of 73 sample trees, which were sampled from coppice-originated pure sessile oak stands over different growth periods and in different site conditions. The most suitable competition variable was determined by examining the correlations between the 24 competition index values and calculated using different approaches and the basal area increment. The individual tree basal area increment models were obtained as functions of tree size, competition, age, and site characteristics. The most important variables that affect the basal area increment in the age-dependent model were the diameter at breast height (DBH) (36.1%), competition index (26.4%), and age (10%). For the age-independent model, the variables are the competition index (32.6%), DBH (30.3%), and the site index (3%), according to the relative importance values. The age-dependent model explained the increased variation of 10% and predicted a 13% decrease in error in the basal area increment than the age-independent model.

Disentangling direct and indirect effects of island area on plant functional trait distributions

AbstractAimSpecies diversity on islands generally increases with island area. This might arise either from direct effects of island area via neutral assembly processes or from indirect effects via habitat and structural differences between islands that scale positively with island area. Here, we tested whether community‐weighted functional trait means of woody plants are directly or indirectly affected by island area to elucidate how functional traits mediate the assembly on differently sized islands.LocationTwenty‐eight tropical islands (25 m2 – 12,000 m2) in the Raja Ampat archipelago, Indonesia.TaxonWoody angiosperms.MethodsStudied islands had a shared geological history but differed in terms of area, habitat quality expressed by soil depth, forest structure expressed by tree basal area and degree of isolation. Traits studied were seed and fruit mass, tree height, wood density, leaf mass per area, leaf nitrogen concentration and chlorophyll content (estimated from chlorophyll‐meter units) and summarised as community‐weighted means (CWM) for each island. Using liner regression, we tested whether CWMs were correlated to island area and basal area and structural equation models (SEMs) to test on direct and indirect effects of island area, basal area, soil depth and isolation on trait distributions.ResultsCWM of seed mass, tree height and chlorophyll content increased with both island area and basal area, whereas leaf nitrogen concentration decreased with increasing basal area. Fruit mass was not correlated to island area and basal area. SEMs revealed that the shifts in tree height, wood density, leaf nitrogen concentration and chlorophyll content were caused directly by basal area, which in turn was directly and positively affected by both island area and soil depth. Differences in seed mass among islands were explained by combined effects of basal area, island area and isolation, whereas fruit mass was only explained by isolation.Main conclusionsTrait values shifted systematically across islands of different sizes. Being small and having light seeds are prevailing trait combinations for establishing on small islands with simple forest structure. For establishment on larger islands with more complex forest structures, species are taller, have heavier seeds, higher chlorophyll content and lower leaf N concentrations. We conclude that mechanisms affecting CWM on islands directly link to ecological differences between islands like forest structure – and only indirectly to island area.

Site and species contribution to β-diversity in terrestrial mammal communities: Evidence from multiple Neotropical forest sites

In a scenario where escalating human activities lead to several environmental changes and, consequently, affect mammal abundance and distribution, β-diversity may increase due to differences among sites. Using the ecological uniqueness approach, we analyzed β-diversity patterns of ground-dwelling mammal communities recorded through comprehensive camera trap monitoring within eight tropical forests protected areas in Mesoamerica and South America under variable landscape contexts. We aimed to investigate whether the contribution of single sites (LCBD) and single species (SCBD) to overall β-diversity could be explained by community metrics and environmental variables, and by species metrics and biological traits, respectively. Total β-diversity was also partitioned into species replacement and richness difference. We related LCBD to species richness, total relative abundance, functional indices, and environmental variables (tree basal area, protected area size, NDVI, and precipitation seasonality), and SCBD to species naïve occupancy, relative abundance, and morphoecological traits via beta regression. Our findings showed that LCBD was primarily explained by variation in species richness, rather than relative abundance and functional metrics. Protected area size and tree basal area were also important in explaining variation in LCBD. SCBD was strongly related to naïve occupancy and relative abundance, but not to biological traits, such as body mass, trophic energy level, activity cycle, and taxonomic category. Local β-diversity was a result of species replacements and to a lesser extent differences in species richness. Our approach was useful in examining and comparing the ecological uniqueness among different sites, revealing the regional scale current status of mammal diversity. High LCBD values comprised sites embedded within smaller habitat extents, hosting lower tree basal areas, and harboring low species richness. SCBD showed that relatively ubiquitous species that occur at variable abundances across sites contributed most to β-diversity.

Low-intensity frequent fires in coniferous forests transform soil organic matter in ways that may offset ecosystem carbon losses.

The impact of shifting disturbance regimes on soil carbon (C) storage is a key uncertainty in global change research. Wildfires in coniferous forests are becoming more frequent in many regions, potentially causing large C emissions. Repeated low-intensity prescribed fires can mitigate wildfire severity, but repeated combustion may decrease soil C unless compensatory responses stabilize soil organic matter. Here, we tested how 30years of decadal prescribed burning affected C and nitrogen (N) in plants, detritus, and soils in coniferous forests in the Sierra Nevada mountains, USA. Tree basal area and litter stocks were resilient to fire, but fire reduced forest floor C by 77% (-36.4 Mg C/ha). In mineral soils, fire reduced C that was free from minerals by 41% (-4.4 Mg C/ha) but not C associated with minerals, and only in depths ≤ 5cm. Fire also transformed the properties of remaining mineral soil organic matter by increasing the proportion of C in a pyrogenic form (from 3.2% to 7.5%) and associated with minerals (from 46% to 58%), suggesting the remaining soil C is more resistant to decomposition. Laboratory assays illustrated that fire reduced microbial CO2 respiration rates by 55% and the activity of eight extracellular enzymes that degrade cellulosic and aromatic compounds by 40-66%. Lower decomposition was correlated with lower inorganic N (-49%), especially ammonium, suggesting N availability is coupled with decomposition. The relative increase in forms of soil organic matter that are resistant to decay or stabilized onto mineral surfaces, and the associated decline in decomposition suggest that low-intensity fires may promote mineral soil C storage in pools with long mean residence times in coniferous forests.

Tree canopy defoliation can reveal growth decline in mid-latitude temperate forests

Climate and weather fluctuations and changes are the most important environmental drivers of tree canopy defoliation, an indicator of forest health. We examined the relationship between tree defoliation and Basal Area Increment (BAI), a dimension of tree growth related to wood biomass increment and carbon sequestration and therefore to the climate change mitigation potential of forests. We analysed data from mostly even-aged, single-species permanent monitoring plots in France over two growing periods (1995–2004: 47 plots, 2008 trees; 2000–2009: 63 plots, 3116 trees) and for which precipitation deficit was identified as the main environmental driver of defoliation. Trees from ten different species were assessed annually for defoliation and measured periodically for growth, from which we derived periodical (10-year) BAI (BAIperiod). We investigated (i) direction and significance of defoliation-BAIperiod relationships and (ii) occurrence, size and significance of BAI deviation of progressively defoliated trees in proportion to the BAI of undefoliated trees (BAIrel). Analyses were first carried out at the level of individual plots, with results subsequently evaluated using meta-analysis and further aggregated at different levels (all species, functional groups, individual species). BAIperiod resulted negatively and significantly related to defoliation, with a significant reduction detected already at slight (15%) defoliation level. A generalized statistically significant reduction of BAIrel was obvious, leading to an estimated reduction of 0.7–0.8% per 1% increase in defoliation for conifers and 0.9% for broadleaves. Considering the observed distribution of trees along the defoliation range, our results indicate an overall growth reduction of ca. 42% in comparison to a theoretical population of undefoliated trees. Shifts in such a distribution can result into loss or gain of growth, which in turn may have cascading effects on carbon sequestration and therefore on land-climate interactions. In the context of the significant increase in defoliation observed in Europe in recent decades, our results suggest that even slight and moderate variations in defoliation may have had a significant impact on tree and forest growth.

The consequence of increasing tree diversity was reducing tree basal area at across different management of agroforestry system of Bangsri Wathershed

The Planting more trees in terrestrial ecosystem had provided on the increasing on many ecosystem services including carbon storage, water supply and soil cover. The relationship between the impact on increasing tree density on tree diversity across various land use type are limited. Using a survey and collecting field measurement within the plot in the size of (100 m × 20 m), we investigated the effect of different type land use on tree diversity, basal area, and species composition at Bangsri Watershed-East Java, comparing different agroforestry system to various young to old production forest of Mahogany (Sweitenia mahogany), Pines (Pinus merkusii) and Rekisi (Magnolia × alba (D.C.). The result showed that seedling population under complex agroforestry system was almost twice (389 individuha-1) higher that those simple agroforestry system or production forest. Young Mahogany (4-5 years) provide the highest number of poles, whilst old Mahogany and Pines production forest (30-40 years) were contributed the greatest tree population at (500 – 600) individuha-1 providing the highest value of basal area since the average of those tree diameter within the size of (25-40 cm). Tree population of complex agroforestry system were lower 50% than production forest. However, diversity indices (H’) of sapling, pole and tree under complex agroforestry system were between 1 to 2.5, while the others plot were<1, except for seedling diversity. In particular the increasing of tree population impact of greater basal area but however it reduced the diversity of, seedling, sapling, pole and tree as the consequences of the implementation of different tree and land management.

Multi-trophic communities re-establish with canopy cover and microclimate in a subtropical forest biodiversity experiment

Plant diversity affects multi-trophic communities, but in young regrowth forests, where forest insects are in the process of re-establishment, other biotic and also abiotic factors might be more important. We studied cavity-nesting bees, wasps and their natural enemies along an experimental tree diversity gradient in subtropical South-East China. We compared insect communities of experimental young forests with communities of established natural forests nearby the experiment and tested for direct and indirect effects of tree diversity, tree basal area (a proxy of tree biomass), canopy cover and microclimate on bee and wasp community composition, abundance and species richness. Finally, we tested if the trophic levels of bees, herbivore-hunting wasps, spider-hunting wasps and their natural enemies respond similarly. Forest bee and wasp community composition re-established towards communities of the natural forest with increasing tree biomass and canopy cover. These factors directly and indirectly, via microclimatic conditions, increased the abundance of bees, wasps and their natural enemies. While bee and wasp species richness increased with abundance and both were not related to tree diversity, abundance increased directly with canopy cover, mediated by tree biomass. Abundance of natural enemies increased with host (bee and wasp) abundance irrespective of their trophic position. In conclusion, although maximizing tree diversity is an important goal of reforestation and forest conservation, rapid closure of canopies is also important for re-establishing communities of forest bees, wasps and their natural enemies.