Are coffee agroforestry systems suitable for circa situm conservation of indigenous trees? A case study from Central Kenya

Coffee agroforestry systems (CAFS) are often considered to be species-rich, potentially contributing to the conservation of indigenous trees. To investigate the conservation capacity of a Kenyan CAFS, all tree species on 62 smallholder coffee farms (covering 39 ha in total) in the Aberdare Mountains of Central Kenya were recorded. In total, 6,642 trees of 59 species were enumerated, with a mean density of 256 trees per ha and a mean species richness of 11.2 species per farm. Indigenous species represented 63 % of the richness but only 31 % of the abundance. For individual farms, as expected, farm size had a positive correlation with tree species richness, but more interestingly there was a negative correlation with tree density. Cluster analysis based on densities of the 18 most important species (defined by an importance value index) revealed two groups of farms: one cluster represented small farms (mean size = 0.4 ha) with high tree species diversity and individual density, particularly of indigenous trees; the other cluster represented large (mean size = 1 ha) and less diverse farms with low tree densities, particularly regarding indigenous species. Tree individuals were unevenly distributed within farms, being more frequent in living fences (38 % of all individuals), the garden zone (20 %) and in coffee plots (18 %). The relative occurrence of indigenous species was also uneven, being greater in living fences and the garden zone. Most adult trees (83 %) were planted, but only 46 % of seedlings were, revealing the active removal of volunteer seedlings by farmers as trees mature. Surveyed coffee farms harboured 20 % of the 135 tree species of the potential natural vegetation for the region, but only 3.6 % of the on-farm tree individuals belonged to the most valuable types of dominant and forest vegetation. Thus, although a source of significant tree cover and heterogeneity at landscape level, the value of these CAFS as circa situm reservoirs of forest tree species is questionable.     

Is there a trade-off between species diversity and genetic diversity in forest tree communities?

The two most important components of biodiversity, species diversity and genetic diversity, have generally been treated as separate topics, although a coordination between both components is believed to be critical for ecosystem stability and resilience. Based on a new trait concept that allows for the assessment of genetic diversity across species, the relationship between species diversity and genetic diversity was examined in eight forest tree communities composed of different tree genera including both climax and pioneer species. It was intended to check whether a trade-off exists between the two diversity components as was found in a few studies on animal species.Using several isozyme-gene systems as genetic markers, the genetic diversity across species within each of the tree communities was determined by two measures, the commonly used intraspecific genetic diversity averaged over species and the recently developed transspecific genetic diversity per species. Both data sets were compared with the corresponding community-specific species diversity resulting in a positive relationship between the two diversity components. A statistically significant positive correlation was established between the transspecific genetic diversity per species and the species diversity for three isozyme-gene systems. Beyond that, consistent results were obtained using different parameters of the diversity measure which characterize the total, the effective and the number of prevalent variants. The number of prevalent variants reflected most significantly the non-randomness of the observed diversity patterns.These findings can be explained by the observation that the pioneer tree species reveal a by far higher genetic diversity than the climax tree species, which means that an increase in species diversity, due to the addition of several pioneer species at the expense of one or two climax species, goes along with an increase in the level of genetic diversity. Forest tree communities with the highest degree of species diversity exhibit therefore the highest transspecific genetic diversity per species. This result was discussed with regard to the particular composition and stability of forest tree communities.     

Do living ex situ collections capture the genetic variation of wild populations? A molecular analysis of two relict tree species,Zelkova abelica and Zelkova carpinifolia

Botanic gardens and arboreta, particularly in regions where iconic relict trees naturally occur, play a vital role in the conservation of these species. Maintaining well-managed living ex situ collections of rare and threatened relict tree species provides an immediate insurance policy for the future species conservation. The aim of this research was to investigate the origin, representativeness and genetic diversity of relict trees kept in botanic gardens and arboreta. We used as a model two ecologically and biogeographically distinct members of the prominent relict genus Zelkova (Ulmaceae), which survived the last glaciation in disjunct and isolated refugial regions: Z. carpinifolia in Transcaucasia and Z. abelicea endemic to Crete (Greece) in the Mediterranean. Our study revealed substantial differences in the genetic diversity and the origin of living ex situ collections of the two investigated taxa. The living ex situ collections of Z. carpinifolia have relatively high representativeness compared with the global genetic variability of natural stands identified in a previous study. In contrast, Z. abelicea, which possesses an extraordinarily high genetic variability in natural populations, is clearly underrepresented in botanic garden collections. Moreover, all Z. abelicea trees investigated in this study most probably originated from a single region, the Levka Ori in western Crete. Thus, the ex situ conservation of Z. abelicea requires major planning and coordination efforts, including the establishment of well-documented collections in botanic gardens in Greece and especially on Crete. New living ex situ collections should be created using plant material collected from all of the mountain regions where Z. abelicea still occurs. Our study highlights the need for re-evaluating the existing living ex situ collections of trees and the development of new strategies for future conservation efforts in botanic gardens and arboreta. The coordination of conservation efforts between gardens must be enhanced to prioritize actions for the most threatened relict tree species.     

Could taxonomic misnaming threaten the ex situ conservation and the usage of plant genetic resources?

Ex situ conservation of plant germplasm, especially seed banking, is a favourable and widely used method for the conservation of plant genetic resources (PGR). The long-term conservation of these resources is fundamental for food security and plant breeding in order to stem the losses in agrobiodiversity and to meet the global challenges that agriculture is facing. The conservation and accessibility of PGR relies on their correct taxonomic labelling and on the building of a searchable database that links ex situ collections together. In the current study, we analysed the impact of taxonomic misnaming in the two major PGR databases (Genesys PGR, EURISCO), listing accessions conserved worldwide. The aim was to understand if taxonomic misnaming issues prevent PGR conservation. We chose as a case-study seed collections of accessions of the genus Citrullus (watermelon genepool), the taxonomy and nomenclature of which have been largely revised in recent times. We observed that taxonomic misnaming greatly limits PGR conservation with only 3% of the accessions listed in the databases correctly named; moreover, 28% were affected by taxonomic errors that prevent the establishment of the accessions’ taxonomic identity, with consequences on their conservation and exploitation. The existence of the problem was also confirmed by the experimental propagation of three misnamed accessions. We suggest herein a series of actions that, put in place, could solve the extant misnaming issues in the databases and prevent their reoccurrence, allowing the correct conservation and the usability by the stakeholders of all the accessions.     

Can we predict carbon stocks in tropical ecosystems from tree diversity? Comparing species and functional diversity in a plantation and a natural forest

? Linking tree diversity to carbon storage can provide further motivation to conserve tropical forests and to design carbon-enriched plantations. Here, we examine the role of tree diversity and functional traits in determining carbon storage in a mixed-species plantation and in a natural tropical forest in Panama. ? We used species richness, functional trait diversity, species dominance and functional trait dominance to predict tree carbon storage across these two forests. Then we compared the species ranking based on wood density, maximum diameter, maximum height, and leaf mass per area (LMA) between sites to reveal how these values changed between different forests. ? Increased species richness, a higher proportion of nitrogen fixers and species with low LMA increased carbon storage in the mixed-species plantation, while a higher proportion of large trees and species with high LMA increased tree carbon storage in the natural forest. Furthermore, we found that tree species varied greatly in their absolute and relative values between study sites. ? Different results in different forests mean that we cannot easily predict carbon storage capacity in natural forests using data from experimental plantations. Managers should be cautious when applying functional traits measured in natural populations in the design of carbon-enriched plantations.     

What is the optimal number of leaves when measuring leaf area of tree species in a forest community?

植物形态性状叶面积简单易测, 能够反映植物对环境的适应与响应, 指示生态系统的功能与过程。在野外测定叶面积时, 叶片取样数量往往采用约定俗成的10-20片, 但到底采集多少叶片才是最优和最具代表性, 却少有探究。该研究以浙江金华山常绿落叶阔叶混交林的优势树种木荷(Schima superba)与枫香树(Liquidambar formosana)为研究对象, 通过对5个胸径等级植株和每个植株6个方位开展大批量叶片取样(>2 500个), 分析两个树种的叶面积变异特征, 探讨叶片取样数量为多少才能最代表该森林类型的叶片大小性状规律。结果表明, 常绿乔木木荷平均叶面积与变幅均小于落叶乔木枫香树。木荷叶面积与胸径无显著相关性, 而枫香树叶面积与胸径有较显著相关性, 但两个树种均在中胸径等级(15-20 cm)差异不显著; 两个树种的叶面积与采样方位无显著相关性, 但在东、西和底部的差异不显著。因此, 综合考虑代表性与野外可操作性, 叶片采集首选中胸径成树的底部叶片。随机抽样统计可知, 树木叶面积测定的最适叶片采集数量因物种而异, 木荷的最适叶片采集数量为40, 而枫香树最少为170片。因此, 在叶面积测定时, 叶片采集的数量应该不能只局限在10-20片, 在人力、物力和时间等条件允许的情况下, 应该尽可能多地测定较多叶片的叶面积。     

Biomass and morphology of fine roots in temperate broad-leaved forests differing in tree species diversity: is there evidence of below-ground overyielding?

Biodiversity effects on ecosystem functioning in forests have only recently attracted increasing attention. The vast majority of studies in forests have focused on above-ground responses to differences in tree species diversity, while systematic analyses of the effects of biodiversity on root systems are virtually non-existent. By investigating the fine root systems in 12 temperate deciduous forest stands in Central Europe, we tested the hypotheses that (1) stand fine root biomass increases with tree diversity, and (2) ‘below-ground overyielding’ of species-rich stands in terms of fine root biomass is the consequence of spatial niche segregation of the roots of different species. The selected stands represent a gradient in tree species diversity on similar bedrock from almost pure beech forests to medium-diverse forests built by beech, ash, and lime, and highly-diverse stands dominated by beech, ash, lime, maple, and hornbeam. We investigated fine root biomass and necromass at 24 profiles per stand and analyzed species differences in fine root morphology by microscopic analysis. Fine root biomass ranged from 440 to 480 g m⁻² in the species-poor to species-rich stands, with 63–77% being concentrated in the upper 20 cm of the soil. In contradiction to our two hypotheses, the differences in tree species diversity affected neither stand fine root biomass nor vertical root distribution patterns. Fine root morphology showed marked distinctions between species, but these root morphological differences did not lead to significant differences in fine root surface area or root tip number on a stand area basis. Moreover, differences in species composition of the stands did not alter fine root morphology of the species. We conclude that ‘below-ground overyielding’ in terms of fine root biomass does not occur in the species-rich stands, which is most likely caused by the absence of significant spatial segregation of the root systems of these late-successional species.     

What is the role of disturbance in catalyzing spatial shifts in forest composition and tree species biomass under climate change?

Mounting evidence suggests that climate change will cause shifts of tree species range and abundance (biomass). Abundance changes under climate change are likely to occur prior to a detectable range shift. Disturbances are expected to directly affect tree species abundance and composition, and could profoundly influence tree species spatial distribution within a geographical region. However, how multiple disturbance regimes will interact with changing climate to alter the spatial distribution of species abundance remains unclear. We simulated such forest demographic processes using a forest landscape succession and disturbance model (LANDIS-II) parameterized with forest inventory data in the northeastern United States. Our study incorporated climate change under a high-emission future and disturbance regimes varying with gradients of intensities and spatial extents. The results suggest that disturbances catalyze changes in tree species abundance and composition under a changing climate, but the effects of disturbances differ by intensity and extent. Moderate disturbances and large extent disturbances have limited effects, while high-intensity disturbances accelerate changes by removing cohorts of mid- and late-successional species, creating opportunities for early-successional species. High-intensity disturbances result in the northern movement of early-successional species and the southern movement of late-successional species abundances. Our study is among the first to systematically investigate how disturbance extent and intensity interact to determine the spatial distribution of changes in species abundance and forest composition.     

Island area and species diversity in the southwest Pacific Ocean: is the lizard fauna of Vanuatu depauperate?

One island group suggested to be an exception to the species–area Relationship is the Vanuatu Archipelago, a group of 13 large and 80 small islands in the southwest Pacific Ocean. To test the hypothesis that the lizard fauna of the Vanuatu Archipelago does not meet the predictions of the species-area relationship, and thus is depauperate, we compare diversity among several island groups in the southwest Pacific: Fiji, the Loyalty Islands, New Caledonia, Samoa, the Solomon Islands, Tonga, and Vanuatu. We found that the lizard diversity of Vanuatu meets the pattern of diversity predicted by the species-area relationship. The Solomon Islands, the largest and least isolated oceanic archipelago considered, has the greatest species diversity and endemism of the oceanic islands. Inclusion or exclusion of island groups based on factors such as geologic history or faunal source affects the strength of the relationship between diversity, area, and history of emergence, and influences perceptions of diversity within individual archipelagos. In addition to island size, factors such evolutionary time scale, speciation, and archipelago complexity influence species richness on islands.     

What is the time scale of magnetic field interaction in biological systems?

An experimental test constraining the intrinsic time scale of a primary physical mechanism that detects extremely-low-frequency (ELF) magnetic fields in biological systems is proposed. The suggested test postulates that a transductive mechanism operating on time scales much shorter than the period of an applied magnetic field cannot obtain any information about the exposure conditions other than the absolute magnitude of the field. By generating field exposures that differ in their vector properties but are equivalent in their time-varying absolute amplitude, it is possible to differentiate between two broad classes of mechanisms: 1) those with intrinsic time scales comparable with or longer than those of the external influence, and 2) those that are much faster than the period of the applied field. The hypothesis assumes an experimental model proven to respond to magnetic fields and sensitive to a change of about a factor of two in one of the field parameters (AC, DC amplitude or frequency). The case of general linearly polarized fields is discussed, and an analytical solution for the case of perpendicular AC/DC fields is given. Bioelectromagnetics 18:244–249, 1997 © 1997 Wiley-Liss, Inc.     

Are rare species useful species? Obstacles to the conservation of tree diversity in the dry forest zone agro‐ecosystems of Mesoamerica

Aim To test the potential to conserve rare dry forest tree and shrub species circa situm. Location Oaxaca, Mexico and Southern Honduras. Methods Local uses (timber, posts and firewood) of species were determined principally through semistructured interviews with 20 rural householders in each of four communities in Honduras and four in Oaxaca. Tree and shrub diversity inventories were carried out in a total of 227 forest patches and parcels of farmland in those eight communities. Species’ conservation priorities were determined using the star system of Hawthorne (1996) and IUCN listings. Results Despite a large number of useful species, remarkably few were also conservation priorities. Useful species were found to be substitutable as is illustrated by Bombacopsis quinata, Cordia alliodora, Guaiacum sanctum and G. coulteri. Conclusions In these areas, circa situm conservation is inhibited by the lack of species that are both rare and useful. Usefulness must be interpreted as a function of substitutability. Natural regeneration provides an abundance of diversity, farmers are unlikely to invest in the management of a species when suitable substitutes are freely available. The key to conserving rare species may be in maintaining or enhancing the value of the landscape elements in which they are found.     

What is the optimal number of leaves when measuring leaf area of tree species in a forest community?北大核心CSCD

Aims Leaf size, as one of the easier measured plant morphological traits, reflects response and adaptation of plants to environment and indicates functions and processes of ecosystem. When measuring leaf size (the leaf area, LA) on the field, the common accepted practice considers that the number of leaves picked off is often 10–20. However, what is the optimal number of leaves remains unknown. In this study, we attempt to determine how many leaves should be investigated when the leaf size of a tree is measured. Methods This study selected two dominant tree species (Schima superba, Ss and Liquidambar formosana, Lf) from a broadleaved evergreen and deciduous mixed forest in Jinhua Mountain of Zhejiang Province, eastern China. On the basis of sampling (>2 500 leaves for each tree) in five classes of the diameter of breast height (DBH) of tree species and at six directions for each individual, variations of LA in the two tree species are statistically analyzed. The optimal number of leaves, which can mostly represent the common leaf size feature, is further investigated. Important findings Mean LA of the evergreen tree Ss was smaller than that of the deciduous tree Lf. The former was (41.60 10.88) cm2 (16.74–100.80 cm2) and the latter was (57.65 19.35) cm2 (11.31–129.51 cm2). LA of Lf was significantly related to the DBH, but LA of Ss was not. LA of both trees in the middle DBH class (15–20 cm) was not significantly different from their means. LA of two trees have no significant correlations with the sampling directions, but LA at the east, west and bottom had no significant relationships with their means. Considering the representativeness and practicality in the field sampling, the priority of selecting leaves can target the bottom direction of middle diameter mature trees. Random sampling analysis indicated that, the optimal number of leaves for tree LA measurement is species specific. The optimal number of leaves for Ss is 40 and for Lf is at least 170, respectively. Therefore, when measuring leaf area in a forest community, the optimal sampling number of leaves should not be limited to 10–20 leaves. Under sufficient labor, material and time, more leaves should be measured. © Chinese Journal of Plant Ecology.     

How competitive is the ‘pioneerclimax’ tree species Nothofagus alpina in pristine temperate forests#br#of Chile?

AimsNothofagusspecies are constitutive elements of the temperate forests along the Southern Andes Mountains. The deciduousNothofagus alpinais a fast-growing, but long-lived opportunistic pioneer species (‘pioneer-climax species’) and co-occurs with the evergreenN. dombeyi. We tested whetherN. alpinais competitively superior toN. dombeyiin mature stands and whether intra-specific competition inN. alpinais stronger than inter-specific competition withN. dombeyi.     

Historical plant records enlighten the conservation efforts of ferns and Lycophytes’ diversity in tropical China

Historical records, e.g., herbarium vouchers, contain information about species distribution since the early days of the scientific exploration of floras until today. These data provide crucial evidence to map the biodiversity of the area of interest and most importantly enable the evaluation of the conservation effectiveness for a given group of organisms. This study aimed to explore the ferns and lycophytes’ diversity of Xishuangbanna Dai Autonomous Prefecture in tropical China with special emphasis on conservation efforts provided by the currently established protected areas (PAs). Instead of relying exclusively on current observation, the database was compiled from digitalized herbarium vouchers and publications being explored with special attention on the temporal and spatial dimensions of collecting efforts. Utilizing the indices including species richness, weighed endemism, corrected weighted endemism, and beta diversity, hotspots of ferns and lycophytes’ diversity were identified. In turn, the proportion of hotspots located outside PAs was estimated as a measure of conservation gaps in Xishuangbanna. Our results revealed a long collecting history of ferns and lycophytes in Xishuangbanna and this prefecture accumulated a considerable number of historical records covering 20.2 % of Chinese and 3.6% of global fern diversity. The accumulation of historical records showed strong parallelism to the historical events shaping modern China. The spatial distribution of ferns and lycophytes in Xishuangbanna was characterized by a concentration of species richness in southern valleys and endemism in western and northern mountains. In terms of conservation, existing PAs showed higher effectiveness in the protection of species richness, whereas lower effectiveness was observed in the protection of endemism and beta diversity. Our research provided a key reference for understanding the diversity and conservation of ferns and lycophytes in Xishuangbanna, as well as highlighting the locality for future collecting and conservation efforts.     

Tree distribution pattern and fate of juveniles in a lowland tropical rain forest – implications for regeneration and maintenance of species diversity

Three analyses of species diversity in a lowland dipterocarp forest were conducted to examine whether the nature of forest community dynamics are determined by density-dependent recruitment and mortality of saplings with a data set obtained in a 50 ha plot in Pasoh Forest Reserve. The first analysis examined whether sapling density varied as a function of distance from the nearest conspecific adult. The second analysis assessed the relationship between the spatial distribution patterns of saplings and adult trees. A third analysis examined sapling recruitment and mortality based on data from 2 censuses, taken in 1985 and 1990. Four hundred forty-four species (each with more than 100 individuals) out of the total of 814 species recorded in the plot, were chosen for the analyses. Of these selected species, 56 species showed significant reduction in sapling densities close to the conspecific adults. Within this group, 11 species were in the emergent layer (29.0% of the total species in this layer), 17 were in the canopy layer (10.5%), 18 were in the understory layer (11.3%), and 10 were in treelet and shrub layer (11.8%). In contrast, the sapling densities of 53 species decreased with increasing distance from conspecific adults; 2 of these species were in the emergent layer (5.2% of the total species in this layer), 14 were in the canopy layer (8.6%), 21 were in the understory layer (13.2%), and 16 were in the treelet and shrub layer (18.8%). The saplings of 35 of the 444 total selected species were clumped, while adults were regularly or randomly distributed. Of the remaining species, in 183 species (41.2%), the distributions of both adults and saplings were clumped. Thus, these 2 analyses do not support the prediction that most of the species of lowland tropical forests fail to produce new adults in their vicinity and as a result of this, adult trees are more regularly distributed than their conspecific juveniles (Janzen 1970). In the third analysis, the recruitment of saplings of species in the emergent and canopy layers increased significantly and in proportion with mortality, suggesting that the dominant species suffer higher mortality than do less common species. This trend is not so apparent in the understory, and the treelet and shrub layers. The results imply that a dynamic equilibrium process, which prevents competitive exclusion and maintains space for minor species, may be active among the species in the upper layers (particularly the emergent layer); however, such a dynamic equilibrium condition is not due exclusively to the reduced recruitment of saplings near conspecific adults, and the dynamic equilibrium condition is not prevalent among the lower story species.     

Extrapair paternity and egg hatchability in tree swallows: evidence for the genetic compatibility hypothesis?

Tree swallows (Tachycineta bicolor) show one of the highestlevels of extrapair paternity in birds, and there is evidencethat females have control over who fathers their offspring.However, it is unclear which benefits female tree swallows obtainfrom mating with multiple males. Using microsatellite DNA fingerprinting,we studied extrapair paternity in relation to nesting successand male, female, and offspring characteristics. More than 70%of all nests contained extrapair young, and more than half ofall offspring were extrapair. Within broods, the extrapair youngwere often fathered by several males. Despite screening allresident and some floater males, we could identify the biologicalfather of only 21% of all extrapair offspring. All identifiedextrapair males were close neighbors. Extrapair males did notdiffer from within-pair males in any of the measured characteristics,except that the former had larger cloacal protuberances than thelatter. Extrapair males were equally successful in gaining paternityin their own broods as males that did not father extra young.In nests with mixed paternity, extrapair young did not differfrom within-pair young in body size or mass. However, nestswith extrapair young had higher hatching success than nestswithout extrapair young. All examined unhatched eggs were fertilizedand thus hatch failure resulted from embryo mortality. The availabledata are in accordance with the genetic diversity and the geneticcompatibility hypothesis, but not with the good genes hypothesis.