Bird occurrence and trophic interactions vary across gradients of tree diversity and microclimate in a planted forest.

The human-induced loss of biodiversity from many ecosystems has led to increased interest in the relationship between biodiversity and ecosystem functioning. Research in this field is mostly focused on the producer level, i.e. the diversity of plants. Plant diversity can positively affect the diversity and abundance of higher trophic level organisms, for example insects. In addition, it has been shown that plant diversity can impact plant-insect interactions such as pollination and herbivory. Most studies on plant diversity effects have been conducted in grasslands, whereas forest ecosystems have received less attention so far. In particular, herbaceous plant communities of the forest understorey and their associated insect communities have rarely been the focus of biodiversity studies. In this thesis we investigated plant diversity effects in the herb layer of a near-natural temperate deciduous forest. We explored possible linkages between the plant diversity of the tree and the herb layer. In addition, we investigated how the diversity of tree and herb layer influence diversity, abundance and community composition of fly communities in the herb layer. Finally, we studied trophic interactions (herbivory, pollination-dependent seed production, seed predation) in relation to tree and herb diversity. The study was conducted on 100 plots along a gradient of tree diversity (2 9 species) and herb diversity (2 28 species) in the Hainich National Park (Central Germany). Vegetation surveys of the herb layer were performed in two consecutive years. Flies were sampled with pan traps and suction sampling. To study trophic interactions, potted individuals of the common understorey herbs Lathyrus vernus and Primula elatior were set out on 40 plots for three months in 2009. On these phytometer plants, we assessed invertebrate herbivore damage as well as seed production as a proxy for pollination success. Half of the L. vernus individuals had been treated with plant parasitic nematodes to investigate if links between belowground and aboveground herbivory are affected by the diversity of the surrounding plant community. Also in 2009, we performed a seed removal experiment using different predator exclusion treatments to study seed predation in the herb layer. Species richness and cover of the herb layer increased with increasing tree diversity. In addition, the environmental variables canopy cover and humus layer mass had a negative effect both on herb layer species richness and cover. Herb layer species richness was positively related to increasing soil pH and the distance to the forest edge. The proportion of forbs increased with increasing tree diversity, whereas the proportion of tree saplings decreased. The proportion of graminoids was not affected. Both tree and herb diversity influenced fly abundance, while abundances of the locally common fly taxa Empidoidea and Phoridae responded to herb diversity only. Relationships between fly abundance and tree and herb diversity were positive in the study location dominated by lime (Lindig), but absent or weakly negative in the beech-dominated location (Thiemsburg). Fly family richness and the species richness of Empidoidea and Phoridae were not affected by tree or herb diversity. In contrast, herb cover showed a strong and consistently positive association both with fly richness and abundance. Plots which were similar in their herb and tree layer composition also had more similar fly communities. In our phytometer experiment, foliar herbivore damage decreased with increasing tree diversity in P. elatior. In L. vernus, foliar herbivore damage only responded to belowground herbivory, with higher aboveground herbivory in nematode treated plants. Seed production per plant increased with increasing tree diversity in L. vernus and decreased with increasing herbivore damage in both species. The seed predation experiment showed that the seed removal rate was positively related to herb diversity for seeds of L. vernus, but only weakly so in the case of P. elatior. Predator exclusion treatments revealed that both vertebrates and invertebrates act as seed predators of L. vernus, while seed removal of P. elatior is mainly performed by invertebrates. Slugs appeared to be the dominant invertebrate seed predators in our study system. In conclusion, we found that the diversity of tree and herb layer affects plant and fly communities in the herb layer of Germany s largest connected deciduous forest. In addition, we demonstrated that several types of trophic interactions, namely herbivory, pollination-dependent seed production and seed predation, are related to tree or herb layer diversity. As a consequence, overall forest biodiversity and the functioning of trophic interactions are expected to benefit from forestry practises that promote high tree diversity, which goes along with a diverse and well-developed herb layer.

Species and processes in ecosystems are part of multi‐trophic interaction networks. Plants represent the lowest trophic level in terrestrial ecosystems, and experiments have shown a stabilizing effect of plant diversity on higher trophic levels. Such evidence has been mainly collected in experimental grasslands. Forests are structurally more complex than grasslands and support the majority of the global biodiversity, but studies on multi‐trophic interaction networks are missing in experimental tree diversity gradients. In a forest diversity experiment in southeast China, we examined how tree diversity affects the structure of trophobiotic networks. Trophobioses are tri‐trophic interactions between plants, sap‐sucking Hemiptera and honeydew‐collecting ants that can be subdivided into a largely mutualistic Hemiptera–ant and an antagonistic plant–Hemiptera network. We inspected almost 7000 trees in 146 plots ranging from monocultures to 16 tree species mixtures and found 194 trophobioses consisting of 15 tree, 33 Hemiptera and 18 ant species. We found that tree diversity increased the proportion of trees harboring trophobioses. Consistent with the prediction that mutualistic and antagonistic networks respond differently to changing environments, we found that the generality index of the mutualistic Hemiptera–ant but not the antagonistic plant–Hemiptera network increased with tree diversity. High generality, maintained by high tree diversity, might correspond to higher functional stability. Hence, our results indicate that tree diversity could increase via bottom–up processes the robustness of ant–Hemiptera associations against changing environmental conditions. In turn, the plant–Hemiptera network was highly complementary, suggesting that host‐specific Hemiptera species may be vulnerable to co‐extinction if their host plants disappear. Based on our results, we provide possible future research directions to further disentangle the bottom–up effect of tree diversity on the structure of trophobiotic networks.SynthesisIt is now widely accepted that plant diversity promotes ecosystem functionality and stability. However, it is still largely unknown how plant diversity affects interactions between trophic levels and if different interaction types are affected differently. Using a tri‐trophic study system consisting of plants, sap‐sucking Hemiptera, and ants we provide evidence that increasing local plant diversity stabilizes the mutualistic Hemiptera–ant but not the antagonistic plant–Hemiptera networks. Our results suggest that bottom–up effects of plant diversity on trophic interactions might generally depend on the type of interaction (mutualistic versus antagonistic) considered.

Habitat fragmentation is a major driver of species loss. Here we test the hypotheses that high tree diversity in a large deciduous forest enhances bird diversity and nest survival. We further expect that forest edges support higher bird diversity when different habitat types adjoin, whereas nest predation is not higher, because the large forest area mitigates potential edge effects. We studied how edge-centre differences and tree diversity (beech-dominated vs. tree-species rich) affect the bird community and survival rates of ground breeding birds’ nests based on an artificial nest predation experiment in the Hainich National Park, Germany. We surveyed birds three times during the breeding season. We selected six forest stands with low tree diversity (i.e. dominated by beech) and six with high tree diversity (i.e. tree-species rich). Each forest stand contained four bird survey plots (plot 1: 0–30m, plot 2: 60–90m, plot 3: 120–150m and plot 4: 180–210m distant from edge; altogether 48 bird survey plots). Additionally each plot corner contained one artificial ground nest baited with one Blue-breasted Quail egg and one plasticine egg for eight days of exposure in the middle of the breeding season. Bird abundance and diversity were higher in the first 30m of the forest. Bird diversity, including ground breeding birds, was also enhanced by higher percentages of bushes, which can provide enhanced food supply, perches as well as sheltering. Nest predation showed no edge effect, supporting the idea that small area of forest fragments causes more important negative effects than the edge in large forest remnants. Predation rates were higher in tree-species rich stands compared to beech-dominated stands, probably due to greater diversity and density of mammalian predators. Edge effects shaped the bird community composition and positively affected abundances of tree and shrub breeding birds, but did not affect ground breeders and the nest predation of ground nests. Shrub breeders accumulating in forest edges might, however, suffer more from nest predation in forest fragments. In conclusion, bird diversity and avian egg predation were affected by both forest edges and tree diversity in surprisingly different ways.

Structural and species diversity explain aboveground carbon storage in forests across the United States: Evidence from GEDI and forest inventory data

Urban academic greenspaces provide a protective environment for the conservation of plants and animals and ecological health benefits to human beings. Several anthropogenic activities and landscape practices lead to patches of natural and built-up areas; therefore, a better understanding of campus tree diversity and ecosystem services among natural and built-up areas may help in biodiversity management. Considering this, we assessed how landscape heterogenicity (i.e. the proportion of natural and built-up/paved surface area) and planning principles influence tree density and diversity patterns in three zones (buffer zone: natural/remnant woodland; transition zone: mixed open grassland and woody plantation; core zone: paved/built-up, grassland, and scattered woody plantation) in the Indian Institute of Science Education and Research (IISER) Mohali campus (Punjab) India. We found a total of 1,993 trees belonging to sixty-eight species, mostly native flora. We found that landscape planning principles significantly influenced tree diversity patterns, with the highest tree diversity in the B3 buffer zone (H: 2.9, PIE: 0.9), which integrated elements of the original landscape and new plantations to optimise ecological value and the lowest diversity in the B2 buffer zone (i.e. H: 0.4; PIE: 0.2) with a monoculture plantation of exotic agroforestry species. We also observed that tree density was negatively influenced by impervious surface area (r = -0.68, p < 0.05) in the core zones and by the plantation of exotic species in the natural areas. The campus diversity supports birds of different feeding guilds (insectivore: 41%, omnivore: 25%, carnivore: 25%, frugivore/nectarivore: 13%, graminivore: 4%, and piscivore: 2%). Additionally, academic buildings planned with high canopy cover and density (45% and 95 ha−1) had reduced the wall temperatures of academic buildings from 12°C to 6°C compared to neighbouring buildings without tree cover. This highlighted the importance of maintaining tree diversity in urban academic institutions to promote urban sustainability.

Tree diversity and density in agroforestry systems has been found to increase the diversity and density of soil macro-fauna. However, very little is known of the relationship between tree diversity and density in cocoa agroforests and soil macro-fauna diversity and density. This study was therefore undertaken to fill this knowledge gap. A mixed research approach was adopted and data analysis was done using descriptive and inferential statistics. From the findings, most cocoa farmers perceived that tree diversity in cocoa agroforests was either average, high or very high. Most cocoa farmers perceived that tree density on its part was either average or low. Concerning soil macro-fauna diversity in cocoa-based agroforestry systems, most of the cocoa farmers perceived that soil macro-fauna diversity was either average or high. For soil macro-fauna density in cocoa agroforests, most cocoa farmers perceived that soil macro-fauna density was either average, high or low. Through correlation and regression analyses, it was found that a statistically significant (p&lt;0.05) direct non-cause-effect and cause-effect relationship existed between the level of tree diversity and density in cocoa-based agroforestry systems (very high tree diversity, high tree diversity, average tree diversity, low tree diversity, very low tree diversity), and the level of soil macro-fauna diversity and density. This implies that increasing tree species diversity and density leads to increasing soil macro-fauna diversity and density in cocoa-based agroforestry systems. It is therefore recommended that policy makers take drastic measures to ensure greater tree diversity and density in cocoa agroforests in order to ensure higher soil macro-fauna diversity and density.

Tree diversity and abundance within an agroforestry system plays a crucial role in the provision of different ecosystem services. It was within this framework that this study sought to examine the contribution of tree diversity and abundance to soil fertility in cocoa-based agroforestry systems. A mixed research approach was adopted during data collection and data analysis was done through the use of descriptive and inferential statistical tools. From the findings of the study, it was revealed that most cocoa farmers perceive tree diversity in cocoa-based agroforestry systems to be between average (50%), high (15%) and very high (20%), while tree abundance was between average (40%), and low (30%). The main types of tree species integrated by cocoa farmers in cocoa-based agroforestry systems were fruit trees (100%), fuelwood trees (70%), trees for shade (52.7%) and trees for building materials (40%). A statistically significant direct relationship (p&lt;0.05) existed between different levels of tree diversity (very high tree diversity, high tree diversity, average tree diversity, low tree diversity, and very low tree diversity) and soil fertility in cocoa-based agroforestry systems, implying that the greater the diversity of tree species the greater the levels of soil fertility in cocoa-based agroforestry systems. Different levels of tree abundance in cocoa agroforests such as average tree abundance, low tree abundance and very low tree abundance had a statistically significant direct relationship (p&lt;0.05) with soil fertility in cocoa-based agroforestry systems, implying that the lower the level of tree abundance, the greater the level of soil fertility in cocoa-based agroforestry systems. Meanwhile levels of tree abundance in cocoa agroforests such as very high tree abundance and high tree abundance had a statistically significant inverse relationship (p&lt;0.05) with soil fertility in cocoa-based agroforestry systems, implying that the higher the tree abundance, the lesser the level of soil fertility. Thus, it is recommended that more diverse tree species should be integrated in cocoa-based agroforestry systems while tree abundance should be kept to an average level in order to sustain the level of soil fertility in cocoa-based agroforestry systems.

C and N stocks in silvopastoral systems with high and low tree diversity: Evidence from a twenty-two year old field study

Cacao (Theobroma cacao) cultivation maintaining a high proportion of shade trees in a diverse composition (agroforestry) is currently being viewed as a sustainable land use practice. Our research hypothesis was that cacao agroforests (AF) can support relatively high tree diversity, as compared to surrounding primary and/or secondary forests. The objective of this study was to assess the impact of forest conversion on tree communities by comparing tree composition, community characteristics (richness and diversity) and spatial structure (density, canopy height, basal area) among primary forest, secondary forest, and cacao AF. In total, we collected data from 30 25 × 25 m plots on three land use systems (20 in cacao AF, five in secondary, and five in primary forests) in San Alejandro, Peruvian Amazon. All trees with DBH ≥ 10 cm were counted, identified to species, and their height and DBH were recorded. Our results support the hypothesis that cacao AF present a relatively high tree species richness and diversity, although they are no substitute for natural habitats. We identified most common species used for shading cacao. Tree species composition similarity was highest between cacao AF and secondary forest. Vegetation structure (density, height, DBH) was significantly lower compared to primary and secondary forest. Species richness and diversity were found to be highest in the primary forest, but cacao AF and secondary forests were fairly comparable. The tree species cultivated in cacao AF are very different from those found in primary forest, so we question whether the relatively high tree diversity and richness is able to support much of the diversity of original flora and fauna.

Understanding spatial patterns of diversity in tropical forests is indispensable for their sustainable use and conservation. Recent studies have reported relationships between forest structure and α-diversity. While tree α-diversity is difficult to map via remote sensing, large-scale forest structure models are becoming more common, which would facilitate mapping the relationship between tree α-diversity and forest structure, contributing to our understanding of biogeographic patterns in the tropics. We developed a methodology to map tree α-diversity in tropical forest regions at 50 m spatial resolution using α-diversity estimates from forest inventories as response variables and forest structural metrics and environmental variables as predictors. To include forest structural metrics in our modelling, we first developed a method to map seven of these metrics integrating discrete light detection and ranging (LiDAR), multispectral, and synthetic aperture radar imagery (SAR). We evaluated this methodology in the Chocó region of Colombia, a tropical forest with high tree diversity and complex forest structure. The relative errors (REs) of the random forest models used to map the seven forest structural variables ranged from low (6%) to moderate (35%). The α-diversity maps had moderate RE; the maps of Simpson and Shannon diversity indices had the lowest RE (9% and 13%), followed by richness (17%), while Shannon and Simpson effective number of species indices had the highest RE, 27% and 47%, respectively. The highest concentrations of tree α-diversity are located along the Pacific Coast from the centre to the northwest of the Chocó Region and in non-flooded forest along the boundary between the Chocó region and the Andes. Our results reveal strong relationships between canopy structure and tree α-diversity, providing support for ecological theories that link structure to diversity via niche partitioning and environmental conditions. With modification, our methods could be applied to assess tree α-diversity of any tropical forest where tree α-diversity field observations coincident with LiDAR data.

Abstract. Khan MS. 2017. Effect of forest composition on bird species abundance in tropical dry deciduous forest: A case of Bhimbandh Wildlife Sanctuary, India. Biodiversitas 18: 78-85. The tropical dry deciduous forest (TDDF) with 38.2% of total forest cover in India forms the largest forest type of India. TDDF have been managed for centuries in the Indian subcontinent. However, so far it is not clear how different forest compositions and structures influence the abundance and the distribution patterns of faunal species vice versa. To provide further insights in this respect, we analysed how different habitat variables influence the abundance and diversity of forest birds. The difference in relative species abundances and habitat separation between forest specialist and generalist birds was also investigated. Different classes of bird density were discriminated with habitat variables. In general, it was found that higher bird densities were concentrated in the lower tree and shrub densities and diversities, however, high grass density and diversity with low tree density and diversity favoured the overall high bird density. Results further indicate the positive association of relative density of specialist bird species with the high grass density and diversity and low tree density and diversity. Specialists occurred in the lower relative densities (0.75±0.68) than that of generalists (0.86±0.69) and were found restricted to dense, pristine woody forest patches with high tree diversity.&#x0D; Keywords: Bhimbandh Wildlife Sanctuary, birds, Forest Composition, India, Tropical Dry Deciduous Forest

Among the obstacles to the native forests restoration in Brazil we find the high costs of planting high diversity of native trees. Searching for reduction of costs and vegetation recovery acceleration, the use of a fast growing exotic species (Pinus elliottii var. elliottii) as pioneer was tested in a riparian area in the cerrado domain, at Assis municipality, So Paulo State, Brazil. As observed in forest plantations with exotic species in the same region, we expected the natural regeneration of native species to occur under the planted exotic trees. In addition, the later exploitation of the exotic species could bring some profit to the land owner, surpassing the restoration costs, and thus stimulating forest restoration initiatives. Pinus was planted in three different spacings (treatments): 3 x 3 m, 3 x 2 m and 2 x 2 m, and a fourth treatment consisted of not planted plots (control). Every treatment had four replications in randomized blocks, the 16 plots (18 x 12 m each) settled along the stream, from 20 to 40m far from the margin. The experimental area had been used as pasture for at least two decades, mostly covered by African grasses. Some native species then existing were preserved when the Pinus trees were planted, in 1995, without revolving the soil. Basal area, crown cover and survival of planted trees, as well as floristic composition, density and crown cover of native species regenerating in every plot (minimum height 50 cm) were assessed in 1996, 1998, 1999, 2001 and

Soil C is the largest C pool in forest ecosystems that contributes to C sequestration and mitigates climate change. Tree diversity enhances forest productivity, so diversifying the tree species composition, notably in managed forests, could increase the quantity of organic matter being transferred to soils and alter other soil properties relevant to the C cycle.A ten‐year‐old tree diversity experiment was used to study the effects of tree identity and diversity (functional and taxonomic) on soils. Surface (0–10 cm) mineral soil was repeatedly measured for soil C concentration, C:N ratio, pH, moisture, and temperature in twenty‐four tree species mixtures and twelve corresponding monocultures (replicated in four blocks).Soil pH, moisture, and temperature responded to tree diversity and identity. Greater productivity in above‐ and below‐ground tree components did not increase soil C concentration. Soil pH increased and soil moisture decreased with functional diversity, more specifically, when species had different growth strategies and shade tolerances. Functional identity affected soil moisture and temperature, such that tree communities with more slow‐growing and shade‐tolerant species had greater soil moisture and temperature. Higher temperature was measured in communities with broadleaf‐deciduous species compared to communities with coniferous‐evergreen species.We conclude that long‐term soil C cycling in forest plantations will likely respond to changes in soil pH, moisture, and temperature that is mediated by tree species composition, since tree species affect these soil properties through their litter quality, water uptake, and physical control of soil microclimates.

Tree diversity, growth status, and spatial distribution affected soil N availability and N2O efflux: Interaction with soil physiochemical properties

Combining Eucalyptus wood production with the recovery of native tree diversity in mixed plantings: Implications for water use and availability