Climate and soil are among the most important factors determining variation in tree communities, but their effects have not been thoroughly elucidated to date for many vegetation features. In this study, we evaluate how climate and soil gradients affect gradients of vegetation composition, species diversity and dominance, structure and functional traits (seed mass and wood density) using over 327 000 trees in 158 sites distributed along environmental gradients in the transitions among the Atlantic forest, Cerrado and Caatinga in Minas Gerais State (MG), Brazil (nearly 600 000 km2).

Gradients in species, genus and family abundance in addition to basal area, stem density, species diversity (Fisher’s alpha), dominance percentage, seed mass and wood density were correlated using multiple regressions with environmental variables, as summarized in four principal component analysis axes (two climatic—precipitation seasonality and temperature range—and two edaphic—soil fertility and soil moisture). Additionally, ordinary kriging maps were used to better illustrate the gradients.

Multiple regression models indicate that all variables but dominance percentage were affected by one or more of the environmental gradients, but the average R2 was low (26.25%). Kriging maps reinforced the patterns observed in the regression models. Precipitation seasonality and soil moisture gradients were the most important gradients affecting vegetation features. This finding suggests that water availability is an important determinant of vegetation features in these vegetation transitions.

Epiphytes and hemiparasites do not have direct access to soil nutrients. Epiphytes acquire nutrients through symbiosis, foliar leachates and throughfall, whilst hemiparasites have specialized structures (haustoria) to acquire nutrients from their host. Irrespective of the green leaf nutrient concentrations of epiphytes, hemiparasites and their hosts, nutrient-resorption efficiency and proficiency are expected to be the greater in epiphytes than in their hosts and in hemiparasites. These hypotheses were tested.

Green and senescing leaves of epiphytes (n = 23), hemiparasites (n = 9) and their hosts were collected, and leaf area, leaf dry weight, nutrient (nitrogen-N, phosphorus-P, potassium-K, calcium-Ca) and sodium (Na) concentrations were measured, and resorption efficiency (%) and proficiency were calculated.

Concentrations of N, P, K, Ca and Na in green leaves of epiphytes and hemiparasites were either similar or greater than those of their hosts, except for lower green leaf N concentration in hemiparasites. Epiphytes resorbed N, P, K and Na, while their hosts resorbed only N, P and K. Hemiparasites and their hosts resorbed P, K and Na while N was not resorbed. Overall, resorption efficiency was greatest in epiphytes > hemiparasites = hosts, while the resorption proficiencies were similar or greater for epiphytes and hemiparasites compared with their hosts, except for N in hemiparasites. Relatively high nutrient concentrations in epiphytes were associated with greater resorption efficiency. Understanding contrasting nutrient concentrations in epiphytes, hemiparasites and their hosts will be important in recognising their contribution to ecosystem nutrient cycling.

While the influence of mistletoe–host interactions on each other’s evolution is well-recognized, the role of interactions between mistletoes and its mutualistic pollinators and seed dispersers mediated by host species is relatively unexplored.

Here, we examine the effects of host species (Mexican hawthorn Crataegus mexicana DC, black cherry Prunus serotina Ehrh., leather-leaf Mexican oak Quercus crassipes Bonpl.) on flower morphology, nectar production, pollinator visitation rate and female reproductive fitness in hemiparasitic Mexican mistletoe Psittacanthus calyculatus (DC.) G. Don (Loranthaceae) populations at three different locations. We first measured the lengths of corolla, style, stamen, exerted stamen and anther, the length and width of the ovary and nectar availability for mistletoe flowers in natural populations. Then, we evaluated flower visitation and measured (length and width) and weighed the fruits and its seeds of mistletoes growing on each of the three host species. Finally, we evaluated the effects of host species, location and flower traits on fruit or seed size variation (both as proxies of reproductive fitness).

We found mistletoes growing on natural hosts P. serotina and Q. crassipes produced larger flowers, fruits and seeds than mistletoes on cultivated C. mexicana. However, these differences varied across space. The amount of available nectar and hummingbird visitation rates in flowers of mistletoes on C. mexicana was higher at the three sites than in flowers of mistletoes on P. serotina or Q. crassipes. The effects of host species, study site and floral trait covariates affected significantly all fitness measures, indicating that mistletoes’ reproductive fitness is affected differently depending on the host species and their site of occurrence. These host-associated differences in reproduction might have implications for interactions with mutualistic vectors.

The productivity of forest plantations in temperate areas is often limited by nitrogen (N), but may shift towards phosphorus (P) limitation with increasing atmospheric N deposition. Nutrient resorption is a nutrient conservation strategy in plants. Although data on nutrient resorption are available for overstory trees, there are few data for understory vegetation.

We examined leaf N and P concentrations and N and P resorption efficiencies (NRE and PRE, respectively) in eight understory species in 11- and 45-year-old Larix principis-rupprechtii stands subjected to N supplementation over a 3-year period.

Leaf N concentrations and N:P ratios increased and P concentrations decreased, with N input in species within the 45-year-old stand, but not in the 11-year-old stand. NRE and PRE were not altered by N input in any of the species in either stand, but N resorption proficiency decreased and P resorption proficiency increased, in the species in the 45-year-old stand. Thus, the growth of understory species may be more P-limited in the 45- versus 11-year-old stand, and nutrient resorption proficiency was more sensitive to N addition than nutrient resorption efficiency. These results will improve the understanding of nutrient use strategies and their responses to N addition in understory vegetation. The contrasting effects of N addition on nutrient status between stand ages cannot be ignored when modeling ecosystem nutrient cycling under global N deposition conditions.

This study aimed to examine the changes in plant species richness, frequency and density along a habitat fragmentation gradient (with varied degrees of habitat fragmentation [DHFs]) in a desertified grassland of Horqin Sandy Land, northeastern Inner Mongolia, China.

In this study, six landscape plots (500 × 500 m each) along a habitat fragmentation gradient were established. A new fragmentation index was formulated to study the effects of habitat fragmentation on biodiversity indices (species richness, frequency and density). Regression analyses (linear- or non-linear regression) were conducted to assess the changes in species richness, frequency and density along the habitat fragmentation gradient at plant community, functional group and species scales, respectively.

There was a non-linear relationship (following a quadratic function) between total species richness and the DHF. Total species richness reached its peak when the DHF was 0.2, beyond which species richness decreased along the fragmentation gradient. Plant functional groups showed their specific responses to habitat fragmentation, and some non-linear relationships and thresholds existed. The relative richness of rare species also showed a non-linear response to habitat fragmentation, with the threshold being DHF = 0.6. Species became rarer (both some common species and rare species) with the intensifying habitat fragmentation. Our study demonstrates the importance of the non-linear relationships and plant functional groups in exploring the effects of habitat fragmentation on biodiversity and implementing effective biological conservation in sand dunes.

Riparian ecosystems play an important role in overall ecosystem function, including the global carbon cycle of terrestrial ecosystems, at both landscape and global scales. Yet few studies have reported in situ measurements of CO₂ in riparian areas where flooding is a unique disturbance to carbon cycling.

At multiple locations across riparian zones (RZ) with different water submergences in Xiangxi Bay (XXB), we studied seasonal variations of CO₂ exchange between this Cynodon-dominated community and the atmosphere for 2 years by using static chambers.

We found that the seasonal changes in CO₂ fluxes were apparent and dependent on the biophysical environment. In the beginning of spring, low gross primary productivity (GPP) in lightly flooded zones (LFZ) resulted in a positive net ecosystem exchange (NEE), indicating a net CO₂ source. With the increase in temperature, more species and vegetation abundance appeared, and the increased GPP turned the LFZ from a net CO₂ source into a sink. This transition seemed predominantly controlled by the physiological growth of vegetation. The mean NEEs, REs and the light-use efficiency (α) of the vegetation at HFZ and MFZ were significantly higher than those at LFZ and UFZ. Yet the coefficients of variation (CV) of NEE and RE at MFZ and HFZ were lower than those at LFZ and UFZ. Submergence promoted the emission and uptake of CO₂ to the atmosphere. Elongated submergence reduced the number of species and lowered the spatial variability of the RZ, further lowering the variation of the CO₂ exchange.

Studies along environmental gradients have shown that intraspecific trait variation (ITV) may contribute considerably to community-level trait variation. However, we lack knowledge about how the extent of ITV varies on a local scale and whether a varying extent of ITV is related to differences in local environmental site and plant community characteristics.

We investigated plant height, specific leaf area (SLA), leaf dry matter content (LDMC) and leaf greenness of three common grass species (Arrhenatherum elatius, Dactylis glomerata, Poa pratensis) in 12 mown grasslands in a local study area around Jena (Thuringia, Germany) across three spatially hierarchical sampling levels: between sites, between subplots within site and within subplots.

Arrhenatherum elatius and D. glomerata had higher means in plant height and a lower variation in leaf traits than P. pratensis. The major proportions of variation in leaf traits of P. pratensis and D. glomerata were found within subplots, while the traits of A. elatius varied mainly between sites. Trait correlations across the hierarchical sampling levels were highly consistent in A. elatius, but more variable in D. glomerata and P. pratensis. Environmental site and plant community characteristics mostly explained a larger proportion of variation in trait means in A. elatius than in D. glomerata and P. pratensis, while metrics of ITV were generally less predictable. Our results suggest that trait variation in P. pratensis and D. glomerata is more strongly related to within-site conditions (i.e. biotic interactions), while differences in local environmental conditions between sites have a strong impact on trait variation in A. elatius. Since our study was limited to three grass species, further studies with a greater number of species are required to make generalizations about the importance of biotic interactions and environmental conditions as drivers of ITV at local scale.

Optimizing water and fertilizer management for crops requires an understanding of root distribution. Maize (Zea mays L.) is currently the most widely planted cereal crop in China, yet the vertical distribution of maize roots across different regions remains unknown. The aims of this work were (i) to quantify the effects of climate and soil texture on the vertical distribution of maize roots, and (ii) to show the depth distribution of root biomass in China.

We used data of maize root biomass from 11 Chinese ecological stations with discontinuous observations from 2004 to 2014 to fit the regression coefficient β for an asymptotic equation Y = 1 – βd, where d is the soil depth and Y is the proportion of root biomass from the surface to depth d. A statistical model was then developed to quantify the effects of climate and soil texture on the fitted β values. Using the statistical model, we map the depth distribution of maize root biomass in China.

Maize root biomass in the 0–100 cm soil depth varied by an order of magnitude at different stations, from 64 to 268 g m?2. Maize planted in sandy soils and/or maize with high accumulated temperature for development had higher root biomass and deeper rooting systems. The fitted β values ranged from 0.785 to 0.977, which can be modeled by an integration of the accumulated temperature during the maize growing period and the soil clay and sand fractions (R2 = 0.66, n = 50, P < 0.001). Up to 82% of maize planting regions in China showed shallower rooting systems where more than 90% and 95% of the root biomass occurred in the top 20 and 30 cm soil layers, respectively. Deeper rooting systems occurred in some temperate arid and temperate semi-arid regions, with less than 80% of the root biomass in the top 20 cm soil. Our findings highlighted the vertical distribution of maize roots, and underlined the spatial variability in the vertical distribution of roots across China’s planting areas of maize.

Non-native invasive plants can alter soil chemistry through litter production and decomposition to facilitate their invasion. However, the important roles of these underlying processes in plant invasion remain poorly understood, particularly in tropical forest ecosystems. Here, we compared litter production, quality and decomposition of two invasive species (Broussonetia papyrifera and Cedrela odorata) and two co-occurring native species (Celtismildbraedii and Funtumia elastica), and soil properties under them to elucidate their roles in the invasion of a tropical forest in Ghana.

Leaf litter production rates were determined using 36 mesh traps installed in the study area, while litter quality and soil physicochemical properties were determined using standard protocols. A 6-month decomposition experiment using the litterbag technique was conducted to compare the decomposition rates of the species.

Litter production varied among the species and over time, with B. papyrifera producing 0.35–4.27 tons ha?1 y?1 from October to January; the other species produced 0.03–1.74 tons ha?1 y?1 over the same period. In the litterbag experiment, B. papyrifera recorded the lowest mass remaining (11–36%), followed by C. odorata (17–51%), F. elastica (31–55%) and C. mildbraedii (48–62%) in that order. Broussonetia papyrifera had the highest nitrogen (3.91%) and phosphorus (0.24%) but lowest lignin (12.20%) concentrations and the lowest C:N (10.87) ratio, indicating higher litter quality compared to the other species. Soil under B. paprifera was richest in phosphorus and nitrogen compared to the other species. Overall, our results indicate that the production of more nutrient-rich and rapidly decomposing leaf litter by B. papyrifera may constitute an important positive feedback mechanism driving its invasion and impacts in this tropical forest.

Species assembly is shaped by the interactions among ecological and evolutionary processes. By integrating the niche conservatism and evolutionary history, the tropical niche conservatism hypothesis (TCH) has clarified species latitudinal diversity gradient at large scales. One of the TCH’s central predictions, though lacking empirical evidence, implies that positive relationship between clade age and temperature along the altitudinal gradient should also be observed. Thus, we aim to test this prediction using a data set derived from forest communities of Mt. Taibai, central China.

We systematically established 49 plots (20 m × 30 m) along the north slope on Mt. Taibai, China. We calculated the mean family age (MFA) and its corresponding standardized values through rarefication and standardization, for woody and herbaceous angiosperm assemblages in each community respectively. Generalized linear models with Akaike weight and correlation analysis was used to evaluate the relationships between MFA with seven environmental predictors.

For both woody and herbaceous assemblages, the standardized MFA showed significant decreasing tendencies along the elevational gradient and positive associations with minimum temperature (measured as mean temperature of the coldest month). Additionally, minimum temperature is the dominant predictor compared with the others in the regression models. These findings are generally consistent with the age-related predictions of the TCH, but are contrary to the results of related studies conducted in tropical regions.