Phylogenetic congruence between subtropical trees and their associated fungi.

Recent studies have detected phylogenetic signals in pathogen-host networks for both soil-borne and leaf-infecting fungi, suggesting that pathogenic fungi may track or coevolve with their preferred hosts. However, a phylogenetically concordant relationship between multiple hosts and multiple fungi in has rarely been investigated. Using next-generation high-throughput DNA sequencing techniques, we analyzed fungal taxa associated with diseased leaves, rotten seeds, and infected seedlings of subtropical trees. We compared the topologies of the phylogenetic trees of the soil and foliar fungi based on the internal transcribed spacer (ITS) region with the phylogeny of host tree species based on matK, rbcL, atpB, and 5.8S genes. We identified 37 foliar and 103 soil pathogenic fungi belonging to the Ascomycota and Basidiomycota phyla and detected significantly nonrandom host-fungus combinations, which clustered on both the fungus phylogeny and the host phylogeny. The explicit evidence of congruent phylogenies between tree hosts and their potential fungal pathogens suggests either diffuse coevolution among the plant-fungal interaction networks or that the distribution of fungal species tracked spatially associated hosts with phylogenetically conserved traits and habitat preferences. Phylogenetic conservatism in plant-fungal interactions within a local community promotes host and parasite specificity, which is integral to the important role of fungi in promoting species coexistence and maintaining biodiversity of forest communities

Linking Aboveground Traits to Root Traits and Local Environment: Implications of the Plant Economics Spectrum.

The plant economics spectrum proposes that ecological traits are functionally coordinated and adapt along environmental gradients. However, empirical evidence is mixed about whether aboveground and root traits are consistently linked and which environmental factors drive functional responses. Here we measure the strength of relationships between aboveground and root traits, and examine whether community-weighted mean trait values are adapted along gradients of light and soil fertility, based on the seedling censuses of 57 species in a subtropical forest. We found that aboveground traits were good predictors of root traits; specific leaf area, dry matter, nitrogen and phosphorus content were strongly correlated with root tissue density and specific root length. Traits showed patterns of adaptation along the gradients of soil fertility and light; species with fast resource-acquisitive strategies were more strongly associated with high soil phosphorus, potassium, openness, and with low nitrogen, organic matter conditions. This demonstrates the potential to estimate belowground traits from known aboveground traits in seedling communities, and suggests that soil fertility is one of the main factors driving functional responses. Our results extend our understanding of how ecological strategies shape potential responses of plant communities to environmental change

Arbuscular mycorrhizal fungi counteract the Janzen-Connell effect of soil pathogens

Soilborne pathogens can contribute to diversity maintenance in tree communities through the Janzen-Connell effect, whereby the pathogenic reduction of seedling performance attenuates with distance from conspecifics. By contrast, arbuscular mycorrhizal fungi (AMF) have been reported to promote seedling performance; however, it is unknown whether this is also distance dependent. Here, we investigate the distance dependence of seedling performance in the presence of both pathogens and AMF. In a subtropical forest in south China, we conducted a four-year field census of four species with relatively large phylogenetic distances and found no distance-dependent mortality for newly germinated seedlings. By experimentally separating the effects of AMF and pathogens on seedling performance of six subtropical tree species in a shade house, we found that soil pathogens significantly inhibited seedling survival and growth while AMF largely promoted seedling growth, and these effects were host specific and declined with increasing conspecific distance. Together, our field and experimental results suggest that AMF can neutralize the negative effect of pathogens and that the Janzen-Connell effect may play a less prominent role in explaining diversity of nondominant tree species than previously thought

Community Compensatory Trend Prevails from Tropical to Temperate Forest

Community compensatory trend (CCT) is thought to facilitate persistence of rare species and thus stabilize species composition in tropical forests. However, whether CCT acts over broad geographical ranges is still in question. In this study, we tested for the presence of negative density dependence (NDD) and CCT in three forests along a tropical-temperate gradient. Inventory data were collected from forest communities located in three different latitudinal zones in China. Two widely used methods were used to test for NDD at the community level. The first method considered relationships between the relative abundance ratio and adult abundance. The second method emphasized the effect of adult abundance on abundance of established younger trees. Evidence for NDD acting on different growth forms was tested by using the first method, and the presence of CCT was tested by checking whether adult abundance of rare species affected that of established younger trees less than did abundance of common species. Both analyses indicated that NDD existed in seedling, sapling and pole stages in all three plant communities and that this effect increased with latitude. However, the extent of NDD varied among understory, midstory and canopy trees in the three communities along the gradient. Additionally, despite evidence of NDD for almost all common species, only a portion of rare species showed NDD, supporting the action of CCT in all three communities. So, we conclude that NDD and CCT prevail in the three recruitment stages of the tree communities studied; rare species achieve relative advantage through CCT and thus persist in these communities; CCT clearly facilitates newly established species and maintains tree diversity within communities across our latitudinal gradient

Spatiotemporal Variability of Land Surface Phenology in China from 2001–2014

Land surface phenology is a highly sensitive and simple indicator of vegetation dynamics and climate change. However, few studies on spatiotemporal distribution patterns and trends in land surface phenology across different climate and vegetation types in China have been conducted since 2000, a period during which China has experienced remarkably strong El Niño events. In addition, even fewer studies have focused on changes of the end of season (EOS) and length of season (LOS) despite their importance. In this study, we used four methods to reconstruct Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) dataset and chose the best smoothing result to estimate land surface phenology. Then, the phenophase trends were analyzed via the Mann-Kendall method. We aimed to assess whether trends in land surface phenology have continued since 2000 in China at both national and regional levels. We also sought to determine whether trends in land surface phenology in subtropical or high altitude areas are the same as those observed in high latitude areas and whether those trends are uniform among different vegetation types. The result indicated that the start of season (SOS) was progressively delayed with increasing latitude and altitude. In contrast, EOS exhibited an opposite trend in its spatial distribution, and LOS showed clear spatial patterns over this region that decreased from south to north and from east to west at a national scale. The trend of SOS was advanced at a national level, while the trend in Southern China and the Tibetan Plateau was opposite to that in Northern China. The transaction zone of the SOS within Northern China and Southern China occurred approximately between 31.4°N and 35.2°N. The trend in EOS and LOS were delayed and extended, respectively, at both national and regional levels except that of LOS in the Tibetan Plateau, which was shortened by delayed SOS onset more than by delayed EOS onset. The absolute magnitude of SOS was decreased after 2000 compared with previous studies, and the phenophase trends are species specific

Long-range Dependence Characteristics of Forest Biological Disasters in China against the Background of Climate Change

Forest biological disasters (FBD) seriously impact energy flow and material cycling in forest ecosystems, while the underlying causes of FBD are complex. These disasters involve large areas and cause tremendous losses. As a result, the occurrence of FBDs in China (CFBD)threatens the country’s ability to realize its strategic target of increasing both forested area (40 million ha) and forest volume (1.3 billion m3) from 2005 to 2020. Collectively, China has officially named this effort to increase forest area and volume the “Two Increases” as national goals related to forestry. Based on Hurst index analysis from fractal theory, we analyzed the time series of the occurrence area and related data of FBDs from 1950 to 2007 to quantitatively determine the patterns of the macro occurrence of FBDs in China. Results indicates that, the time series of (CFBD) areas is fractal (self-affinity fractal dimension D=1.3548), the fluctuation of (CFBD) areas is positively correlated (auto-correlation coefficient C=0.2170), and the occurrence of the time series of (CFBD) is long-range dependent (Hurst index H=0.6416), showing considerably strong trend of increases in FBDC area. Three different methods were further carried out on the original time series, and its two surrogate series generated by function surrogate in library tseries, and function SurrogateData in library in WaveletCo on software R, so as to analyze the reliability of Hurst indexes. The results showed that the Hurst indices calculated using different estimation methods were greater than 0.5, ranging from 0.64 to 0.97, which indicated that the change of occurrence area data of FBDs was positively autocorrelated. The long-range dependence in forest biological disasters in China is obvious, and the spatial extent of FBDs tended to increase during this study period indicating this trend should be expected to persistent and worsen in the future

Data from: Habitat effects on intra-species variation in functional morphology: evidence from freshwater fish

Biotic-environment interactions have long been considered an important factor in functional phenotype differentiation in organisms. The differentiation processes determining functional phenotypes can reveal important mechanisms yielding differences in specific functions of animal traits in the ecosystem. In the present study we examined functional morphological variations in relation to increasing geographic altitude. Six fish species were examined for how environment factors affect intra-specific functional morphology in the subtropical Pearl River in southern China. Functional morphology traits revealed variable effects due to geographic elevation, although spatial autocorrelation existed among the species tested. The results showed that high-elevation individuals had a more narrow-bodied morphology, with more flexible manoeuvrability when swimming, and more evenly distributed musculature than low-elevation individuals. Low-elevation individuals preyed upon larger food sources than high-elevation individuals in some species. Fish functional morphology was strongly affected by regional environmental factors (such as elevation and water temperature) and physical characteristics of local rivers (such as flow velocity, river fractals and coefficients of fluvial facies). In addition, the effects of the regional factors were stronger than those of the local factors in the Pearl River. Furthermore, it was found that morphological traits associated with locomotion were primarily effected by the river’s physical characteristics. While morphological traits associated with food acquisition were primarily affected by water chemical factors (such as DO, water clarity, NH4-N concentration and TDS). These results demonstrated that habitat has an influence on the biological morphology of fish species, which further affects the functioning of the organism within the ecosystem

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