Plant Functional Groups Research Articles

Differences in background environment and fertilization method mediate plant response to nitrogen fertilization in alpine grasslands on the Qinghai-Tibetan Plateau

Grassland degradation threatens ecosystem function and livestock production, partly induced by soil nutrient deficiency due to the lack of nutrient return to soils, which is largely ascribed to the intense grazing activities. Therefore, nitrogen (N) fertilization has been widely adopted to restore degraded Qinghai-Tibetan Plateau (QTP) grasslands. Despite numerous field manipulation studies investigating its effects on alpine grasslands, the patterns and thresholds of plant response to N fertilization remain unclear, thus hindering the prediction of its influences on the regional scale. Here, we established a random forest model to predict N fertilization effects on plant productivity based on a meta-analysis synthesizing 88 publications in QTP grasslands. Our results showed that N fertilization increased the aboveground biomass (AGB) by 46.51 %, varying wildly among plant functional groups. The positive fertilization effects intensified when the N fertilization rate increased to 272 kg ha−1 yr−1, and decreased after three years of continuous fertilization. These effects were more substantial when applying ammonium nitrate compared to urea. Further, a machine learning model was used to predict plant productivity response to N fertilization. The total explained variance and mean squared residuals ranged from 49.41 to 75.13 % and 0.011–0.058, respectively, both being the highest for grasses. The crucial predictors were identified as climatic and geographic factors, background AGB without N fertilization, and fertilization methods (i.e., rate, form, and duration). These predictors with easy access contributed 62.47 % of the prediction power of grasses' response, thus enhancing the generalizability and replicability of our model. Notably, if 30 % of yak dung is returned to soils on the QTP, the grassland productivity and plant carbon pool are predicted to increase by 5.90–6.51 % and 9.35–10.31 g C m−2 yr −1, respectively. Overall, the predictions of this study based on literature synthesis enhance our understanding of plant responses to N fertilization in QTP grasslands, thereby providing helpful information for grassland management policies.Conflict of interest: The authors declare no conflict of interest.

A sequence of multiyear wet and dry periods provides opportunities for grass recovery and state change reversals

AbstractMultiyear periods (≥4 years) of extreme rainfall are increasing in frequency as climate continues to change, yet there is little understanding of how rainfall amount and heterogeneity in biophysical properties affect state changes in a sequence of wet and dry periods. Our objective was to examine the importance of rainfall periods, their legacies, and vegetation and soil properties to either the persistence of woody plants or a shift toward perennial grass dominance and a state reversal. We examined a 28‐year record of rainfall consisting of a sequence of multiyear periods (average, dry, wet, dry, average) for four ecosystem types in the Jornada Basin. We analyzed relationships between above ground net primary production (ANPP) and rainfall for three plant functional groups that characterize alternative states (perennial grasses, other herbaceous plants, dominant shrubs). A multimodel comparison was used to determine the relative importance of rainfall, soil, and vegetation properties. For perennial grasses, the greatest mean ANPP in mesquite‐ and tarbush‐dominated shrublands occurred in the wet period and in the dry period following the wet period in grasslands. Legacy effects in grasslands were asymmetric, where the lowest production was found in a dry period following an average period, and the greatest production occurred in a dry period following a wet period. For other herbaceous plants, in contrast, the greatest ANPP occurred in the wet period. Mesquite was the only dominant shrub species with a significant positive response in the wet period. Rainfall amount was a poor predictor of ANPP for each functional group when data from all periods were combined. Initial herbaceous biomass at the plant scale, patch‐scale biomass, and soil texture at the landscape scale improved the predictive relationships of ANPP compared with rainfall alone. Under future climate, perennial grass production is expected to benefit the most from wet periods compared with other functional groups with continued high grass production in subsequent dry periods that can shift (desertified) shrublands toward grasslands. The continued dominance by shrubs will depend on the effects that rainfall has on perennial grasses and the sequence of high‐ and low‐rainfall periods rather than the direct effects of rainfall on shrub production.

Bryophytes dominate plant regulation of soil microclimate in alpine grasslands

Soil temperature and moisture are important regulators of a broad range of biotic and abiotic processes in terrestrial ecosystems. Vegetation can, in turn, play a role in regulating soil microclimate, which creates potential for powerful and interactive feedbacks from soil and vegetation on the atmosphere. Although the regulatory effect of vegetation on soil microclimatic conditions has been quite extensively and empirically assessed, most studies have determined the net effect of intact woody vegetation versus bare ground. However, for other plant functional groups we lack a clear understanding of their role and any climate‐context dependency in controlling microclimatic conditions.We investigated the role of three major plant functional groups – graminoids, forbs and bryophytes – in regulating soil microclimate in semi‐natural alpine grasslands. Using a fully factorial above‐ground biomass removal experiment, we assessed the role of these plant functional groups in regulating soil temperature amplitude, soil moisture, and number of freezing days. The experiment was replicated across orthogonal temperature and precipitation gradients in Norway to assess whether the effects of functional group abundance varied with climate.The effect of plant biomass on soil microclimate varied among functional groups across the climatic gradients. Bryophytes reduced growing season soil temperature, whereas graminoids and forbs did not (0.5ºC compared to 0ºC), and with a stronger effect in colder climates at higher elevations and on days with high solar radiation. Bryophyte biomass further reduced the number of soil freezing days at boreal and sub‐alpine sites. Finally, graminoid biomass partly explained variation in soil moisture: soils dried more under graminoids at drier sites.Our findings highlight that functional group identity plays a key role in regulating soil microclimate in alpine grasslands across seasons. The strong effect of bryophytes on soil temperature points to their importance in the plant community for a variety of ecosystem functions, some of which may be indirectly vulnerable to future warming via biomass reductions of bryophytes.

Long-term livestock exclusion increases plant richness and reproductive capacity in arid woodlands.

Herbivore exclusion is implemented globally to recover ecosystems from grazing by introduced and native herbivores, but evidence for large-scale biodiversity benefits is inconsistent in arid ecosystems. We examined the effects of livestock exclusion on dryland plant richness and reproductive capacity. We collected data on plant species richness and seeding (reproductive capacity), rainfall, vegetation productivity and cover, soil strength and herbivore grazing intensity from 68 sites across 6500 km2 of arid Georgina gidgee (Acacia georginae) woodlands in central Australia between 2018 and 2020. Sites were on an actively grazed cattle station and two destocked conservation reserves. We used structural equation modeling to examine indirect (via soil or vegetation modification) versus direct (herbivory) effects of grazing intensity by two introduced herbivores (cattle, camels) and a native herbivore (red kangaroo), on seasonal plant species richness and seeding of all plants, and the richness and seeding of four plant groups (native grasses, forbs, annual chenopod shrubs, and palatable perennial shrubs). Non-native herbivores had a strong indirect effect on plant richness and seeding by reducing vegetative ground cover, resulting in decreased richness and seeding of native grasses and forbs. Herbivores also had small but negative direct impacts on plant richness and seeding. This direct effect was explained by reductions in annual chenopod and palatable perennial shrub richness under grazing activity. Responses to grazing were herbivore-dependent; introduced herbivore grazing reduced native plant richness and seeding, while native herbivore grazing had no significant effect on richness or seeding of different plant functional groups. Soil strength decreased under grazing by cattle but not camels or kangaroos. Cattle had direct effects on palatable perennial shrub richness and seeding, whereas camels had indirect effects, reducing richness and seeding by reducing the abundance of shrubs. We show that considering indirect pathways improves evaluations of the effects of disturbances on biodiversity, as focusing only on direct effects can mask critical mechanisms of change. Our results indicate substantial biodiversity benefits from excluding livestock and controlling camels in drylands. Reducing introduced herbivore impacts will improve soil and vegetation condition, ensure reproduction and seasonal persistence of species, and protect native plant diversity.

Understanding the drivers of ecosystem multifunctionality in the Mongolian steppe: The role of grazing history and resource input

Predicting the comprehensive driver of ecosystem multifunctionality is crucial for effective grassland management. However, the underlying biotic and abiotic mechanisms of ecosystem multifunctionality under global change and land use remain poorly understood. In this study, a 3-year field experiment was conducted in a semi-arid steppe in Inner Mongolia to investigate the relative importance of different biotic and abiotic factors in regulating aboveground ecosystem multifunctionality (AEM) and belowground ecosystem multifunctionality (BEM) in response to resource input after long-term grazing. The experiment involved three grazing intensities (1.5 low, 4.5 moderate, and 9.0 high sheep/ha) with a 7-year difference in grazing history. Precipitation (W) and nitrogen deposition (N) were manipulatively increased during the growing season. The study focused on exploring the effects of various biotic factors (e.g. species richness, functional diversity, plant functional groups) and abiotic factors (e.g. soil environment variables) on AEM and BEM. The results revealed asymmetric responses of AEM and BEM to resource input. Resource input enhanced AEM, but not BEM. However, increasing grazing intensity substantially reduced BEM, though we noted that AEM and BEM decreased the most under moderate grazing. Interestingly, the study found consistent responses of single ecosystem functions and ecosystem multifunctionality to resource input across the three grazing blocks. Structural equation modeling (SEM) analysis indicated that species richness primarily enhanced AEM, while soil environment played a major role in promoting BEM across different grazing history intensities and the whole grazed system. Multiple biotic and abiotic factors with varying relative importance in different grazing history scenarios controlled AEM and BEM. Species richness exhibited a strong influence on AEM and BEM, but within a narrow effect threshold range, whereas soil environment had a lesser effect size but a wider threshold range. This study provides the first evidence that grazing history and resource enrichment jointly regulate AEM and BEM. The findings highlight the importance of considering biodiversity conservation, soil health, and land use history in management practices aimed at maintaining ecosystem multifunctionality under climate change and human activities scenarios.

Adaptive Relationships in Hemi-Boreal Forests: Tree Species Responses to Competition, Stress, and Disturbance.

European Union forest policy calls for closer-to-nature forest management, but natural disturbances and forest succession are ecological phenomena that are difficult to characterize and integrate into sustainable forest management practices. Therefore, the aim of this study is to explore the adaptive properties of Lithuania's hemi-boreal forest ecosystems. To accomplish this, we first reviewed (i) the potential natural forest communities, (ii) the successional dynamics, and (iii) adaptive strategies of forest trees, and second, we synthesised the adaptive relationships using these three reviews. The results firstly identified that Lithuania's potential natural forests are broadly divided into two climatically based zonal formations: (i) mesophytic and hygromesophytic coniferous and broadleaved forests and (ii) mesophytic deciduous broadleaved and coniferous-broadleaved forests. Secondly, the review of successional dynamics showed that each tree species can be categorised into various end communities and plant functional groups. Using the differences in tree establishment and phenological development modes we identified four forest dynamic types of tree adaptive strategies: stress-resistant ruderals, competitive stress-sensitive ruderals, ruderal stress-sensitive competitors, and stress-resistant competitors. Such functional redundancy leads to a variety of tree responses to competition, stress, and disturbance, which reduces the risk of loss of forest ecosystem functioning. Finally, the synthesised review on the adaptive relationships of each forest tree community shows both the niche position of each hemi-boreal forest tree species and how they should be managed in the organization of plant communities. We believe that this research can serve as a guide for future relevant research and the development of appropriate methods for sustainable forest management.

Mechanical forest restoration treatments stimulate understory plants in the Colorado Front Range

Restoration efforts are underway in dry conifer forests across the western United States to increase their resilience to wildfire and other disturbances. Because such treatments typically decrease overstory density and homogeneity, they can also drive changes in the understory plant community. Past studies of post-treatment changes in understories have found variable results over short time frames and across regions, highlighting the need to study longer-term, region-specific responses. We investigated whether mechanical restoration treatments benefited understory plants in dry conifer forests of the Colorado Front Range, and what biotic and abiotic variables modified understory plant responses in treated areas. We analyzed data collected 1–2 years pre-treatment, 1–2 years post-treatment, and 4–6 years post-treatment in 168 plots, which were distributed across 8 sites and 16 pairs of treated and nearby untreated areas. Treatments were implemented by removing trees with heavy machinery or hand tools (i.e., thinning). By the time treatments were 4–6 years old, native understory plant cover was 1.7 times higher in treated compared to untreated plots, and native richness was 1.1 times higher. Heightened cover and richness values in treated plots were not driven by a single native plant functional group, but by a large portion of the native community; long-lived, graminoid, vegetatively spreading, and non-vegetatively spreading plants all had higher cover in treated plots, while short-lived, long-lived, forb, graminoid, and non-vegetatively spreading plants had higher richness in treated plots. Non-native plants showed 3.1 times higher cover and 4.4 times higher richness in treated compared to untreated plots at 4–6 years post-treatment, but were present at very low levels (e.g., ≤ 0.5% mean cover in either treatment). Greater native plant cover and richness at 4–6 years post-treatment were associated with lower overstory basal areas that resembled 19th-century forest structural conditions for the landscape. Contrary to expectations, a long-term measure of moisture availability (i.e., 30-year average climatic water deficit) was not a strong predictor of native cover or richness in treated plots 4–6 years post-treatment; rather, they were better predicted by moisture availability during the spring months prior to sampling. Overall, the consistent and enduring stimulation of cover and richness of native understory plants after mechanical treatments, with only limited invasion from non-native species, illustrates the important benefits of ongoing restoration activities in dry conifer forests of the Colorado Front Range.

Ecological adaptation strategies of plant functional groups in the upper reaches of the Tarim River based on leaf functional traits

Plant functional traits can reflect plants' long-term adaptive responses to the environment. However, the ecological adaptation strategies adopted by desert plants in plant functional groups to cope with extreme environments remain unclear. Therefore, in this study, plants belonging to 16 common desert species were collected to measure leaf chemical and physiological traits in the extremely arid region along the northern edge of the Tarim Basin. Cluster analysis was used to divide the plants into different functional groups to reveal the response and adaptation mechanisms of plants to environmental and resource changes at a higher level. The results showed that (1) based on plant leaf functional traits, the 16 desert plants could be divided into three plant functional groups, showing significant differences in chemical element contents and ratios, osmoregulatory substance content, and water use efficiency (p＜0.05). (2) Functional group 1 (FG1) had the highest leaf nutrient and water use efficiency and soluble sugar content, lower N and P content and the lowest soluble protein content, indicating a passive strategy of high consumption. Plants in functional group 2 (FG2) were poor in leaf N, rich in P and had the lowest organic carbon content, soluble sugar content, and water use efficiency, indicating a relatively conservative strategy. Members of functional group 3 (FG3) were rich in leaf C, N and P, and their proline, soluble protein and sugar content were all high, indicating a rapid resource acquisition and growth strategy. (3) There were significant correlations among most leaf traits of each functional group (p＜0.05); although the relationships were inconsistent, extremely significant correlations existed between the organic carbon and nonstructural carbon contents in FG1, C/P and soluble sugar contents in FG2, and total N and proline contents in FG3 (p＜0.01). These results indicate that desert plant functional groups adopt different ecological strategies and contribute to a comprehensive understanding of how plants adapt and respond to extremely arid environments, providing a scientific basis for the protection of desert vegetation.

Calcareous grassland restored by clearance and subsequent sheep grazing show fast recovery of plant functional traits – Results from a 25-year-long experiment

In this study, the long-term restoration success of calcareous grasslands was investigated using a functional trait approach. The study site is located in the Swabian Alb, Germany, where a former calcareous grassland patch was restored in the 1990s by clearance of a spruce (Picea abies (L.) H. Karst.) afforestation and subsequent reintroduction of sheep grazing as mobile dispersal vector. Vegetation development was monitored over a period of 25 years, both on the restored and an adjacent never afforested ancient grassland which is still managed by traditional sheep grazing. Changes in the functional composition of fifteen ecological meaningful traits were investigated by comparing the respective attribute expressions of the restored with the ancient reference grassland for each year of observation. A RLQ-analysis was conducted in order to identify plant functional groups. The comparison of attribute expressions showed that differences between restored and ancient grassland decreased rapidly over time. The greatest differences were found in persistence-related traits (e.g., life span and growth form) while dispersal- and establishment-related traits recovered faster. The clustering of plant functional groups showed similarities with Grime’s CSR-strategy, as cluster analysis grouped species with either ruderal, competitive or stress-tolerant trait attributes. 20 years after restoration, stress-tolerators dominated, while the ruderal cluster could not longer be detected and only a small group of competitive, mostly woody species remained. In 2018, RLQ analysis revealed no differences in the functional composition between restored and ancient grassland. The quick functional recovery is most likely attributed to the reestablishment of the traditional low-intensive grazing management but also to the close vicinity of the ancient grassland as no spatial isolation prevented dispersal of plant species. Hence, the functional trait approach showed that restoration by clearance and subsequent sheep grazing was a suitable management in our study.

Underground trees inhabit varied environmental extremes across the Afrotropics.

Geoxyles, a distinctive feature of Afrotropical savannas and grasslands, survive recurrent disturbances by resprouting subshrub branches from large below-ground woody structures. Underground trees are a type of geoxyle that independently evolved within woody genera of at least 40 plant families in Africa. The environmental limits and determinants of underground tree biogeography are poorly understood, with the relative influence of frost and fire debated in particular. We aim to quantify variability in the niche of underground tree species relative to their taller, woody tree/shrub congeners. Using occurrence records of four Afrotropical genera, Parinari (Chrysobalanaceae), Ozoroa (Anacardiaceae), Syzygium (Myrtaceae) and Lannea (Anacardiaceae), and environmental data of nine climate and disturbance variables, the biogeography and niche of underground trees are compared with their open and closed ecosystem congeners. Along multiple environmental gradients and in a multidimensional environmental space, underground trees inhabit significantly distinct and extreme environments relative to open and closed ecosystem congeners. Niche overlap is low among underground trees and their congeners, and also among underground trees of the four genera. Of the study taxa, Parinari underground trees inhabit hotter, drier and more seasonal environments where herbivory pressure is greatest. Ozoroa underground trees occupy relatively more fire-prone environments, while Syzygium underground trees sustain the highest frost frequency and occur in relatively wetter conditions with seasonal waterlogging. Lannea underground trees are associated with the lowest temperatures, highest precipitation, and varying exposure to disturbance. While underground trees exhibit repeated convergent evolution, varied environments shape the ecology and biogeography of this iconic plant functional group. The multiplicity of extreme environments related to fire, frost, herbivory and waterlogging that different underground tree taxa occupy, and the distinctiveness of these environments, should be recognized in the management of African grassy ecosystems.

Time, climate, and soil settings set the course for reclamation outcomes following dryland energy development

AbstractSoil attributes, climate, and time since reclamation have important implications for oil and gas reclamation success on drylands. It is uncertain if reclaimed well pads, on highly degraded drylands, can successfully regain ecological function or meet indicator benchmarks for reclamation. Here, our goals were to assess patterns in reclamation outcomes relative to (1) soil attributes, climate, and time since reclamation; and (2) plant and soil reference benchmarks. We collected a suite of plant, soil, and landscape characteristics from 134 reclaimed well pads on the Colorado Plateau that spanned climate and soil gradients and ranged from 2 to 20 years post‐reclamation, then compared characteristics to those from 583 reference plots. On the reclaimed pads, less saline soils, more mesic climates, and longer time since reclamation were associated with favorable reclamation outcomes based on metrics of plant species richness and diversity, plant structure, and cover of important plant functional groups. However, most pads had major departures in 1/4 indicators, suggesting unsuccessful reclamation. Arid warm locations with shallow soils had the greatest percentage of major departures, and noxious plant richness had the greatest departures across soil and climate settings. Our assessment indicates reclamation is failing in key metrics for most pads, and the results highlight the role of environmental conditions in driving reclamation outcomes. These new insights are valuable for ascertaining possible reclamation outcomes and success rates following energy related disturbance, including orphaned wells and renewable energy development. Importantly, the approach used here has applicability for setting benchmarks and outcome standards.

Different responses of functional groups to N addition increased synchrony and shortened community reproductive duration in an alpine meadow

Abstract Flowering and fruiting phenology of plants is sensitive to environmental cues, and changes in reproductive phenology of individual plant species under climate change have been widely reported. However, how species‐level phenological responses scale up to affect community‐level reproductive phenology patterns (synchrony and reproductive duration) are still unclear. An experiment on the effects of nitrogen (N) addition and precipitation changes on reproductive phenological traits of 52 species was conducted in an alpine meadow on the eastern Tibetan Plateau to determine the influence of the phenological response in different functional groups on community‐level reproductive phenology. N addition significantly delayed the onset date of reproductive phenology of sedges (early‐flowering species) and advanced the end date of reproduction of forbs (late‐flowering species). Meanwhile, N addition reduced the number of individuals involved in reproduction of sedges and forbs, but it increased that of grasses (late‐flowering species). Furthermore, N addition increased reproductive synchrony, delayed the onset and shortened the duration of reproductive phenology at the community level. However, precipitation changes and their interaction with N addition had no significant effect on reproductive phenology of the alpine plant community. Synthesis. These results suggested that differences in the direction and magnitude of response of different species to N enrichment lead to compression of reproductive duration at the community level, increasing the degree of overlap between reproductive events, which could change future species diversity, trophic interactions and productivity accumulation in alpine meadows on the Tibetan Plateau. Overall, knowledge of phenological responses from plant functional groups to the community level contributes to robust prediction and mechanistic understanding of community structure and function in response to future climate change.

Testing a novel pasture quality index using remote sensing tools in semiarid and Mediterranean grasslands

Estimating the nutritional value of herbage is a core aspect of livestock pasture management. Quantitative information related to significant findings is essential for assessing nutritional provision and preventing pasture degradation. Here, we developed a new Pasture Quality Index (PQI) that indicates the nutritional quality of pastures based on their nutritional value and the composition of plant functional groups of the vegetation. We applied the model on a regional scale using VENμS satellite data, collected more than 450 plant samples, and applied pasture quality parameters analysis. Pasture samples were collected from paddocks under two different grazing intensities in Israel in a semiarid and a Mediterranean grassland. Pasture quality was estimated five times over two years at mid- and peak vegetation growth stages. The PQI included: protein content, fiber content, dry matter digestibility and the proportion of unpalatable spiny thistles. A support vector machine regression model was used to train statistical models that relate ground truth PQI data to the reflectance values of the VENμS satellite. Large-scale forage quality maps at 5 m spatial resolution were created. Fine-resolution drone orthomosaics were used to enhance the satellite-based predictions accuracy, resulting in a model accuracy of R2 = 0.86. We observed that nutritional quality showed strong dependence on seasonality and the grazing regime, with higher quality observed during mid-growth compared to peak growth. Higher quality was also observed under grazing compared to ungrazed paddocks. The occurrence of unpalatable thistles in grazed paddocks significantly reduced the pasture quality at the Mediterranean grassland. To summarize, the PQI enables the integration of several quality indicators into an index that helps in detecting the effects of grazing management on rangelands. In addition, high accuracy was achieved in relating the overall PQI and high spatiotemporal resolution satellite imagery data. Our developed methodology enables site-specific, spatially explicit, frequent, and area-extensive pasture quality assessment that can aid in optimizing livestock management in various ecosystems.

Vegetation, topography, and soil depth drive microbial community structure in two Swedish grasslands.

Soil microbial diversity and community composition are shaped by various factors linked to land management, topographic position, and vegetation. To study the effects of these drivers, we characterized fungal and bacterial communities from bulk soil at four soil depths ranging from the surface to below the rooting zone of two Swedish grasslands with differing land-use histories, each including both an upper and a lower catenary position. We hypothesized that differences in plant species richness and plant functional group composition between the four study sites would drive the variation in soil microbial community composition and correlate with microbial diversity, and that microbial biomass and diversity would decrease with soil depth following a decline in resource availability. While vegetation was identified as the main driver of microbial community composition, the explained variation was significantly higher for bacteria than for fungi, and the communities differed more between grasslands than between catenary positions. Microbial biomass derived from DNA abundance decreased with depth, but diversity remained relatively stable, indicating diverse microbial communities even below the rooting zone. Finally, plant-microbial diversity correlations were significant only for specific plant and fungal functional groups, emphasizing the importance of functional interactions over general species richness.

Soil macrofauna correlations with soil chemical and physical properties and crop sequences under no-tillage

ABSTRACTSoil macrofauna is an important indicator of soil quality, as it is sensitive to changes in the environment as a result of soil management, which includes soil chemical and physical properties and the diversity of cultivated species. This study aimed to evaluate the composition and structure of soil macrofauna under a no-tillage system in different crop sequences, with and without crop rotation, over two growing seasons: a rainy summer and a dry winter. The crop sequences were soybean/corn rotation in the summer and corn in the winter; soybean/corn rotation in the summer and sunn hemp in the winter; soybean monoculture in the summer and sunn hemp in the winter; and corn monoculture in the summer and corn monoculture in the winter growing season. The nutrient content of the crop residues left on the soil surface, soil chemical and physical properties, and soil macrofauna were determined. Functional plant groups (grasses or legumes) individually influenced the composition of soil macrofauna more significantly than the effect of crop sequence, with or without rotation, and growing season. Grasses favored an increased density of groups such as Oligochaeta, Isoptera, and Formicidae. In contrast, legumes contributed to the variation in the total density of individuals and Diplura and Coleoptera groups. Furthermore, the influence of functional plant groups (grasses or legumes) on the composition and density of soil macrofauna were related to soil chemical (P and N content) and physical properties (particulate organic carbon and soil moisture), which determined the composition of soil macrofauna groups.

Plant diversity on islands in the Anthropocene: Integrating the effects of the theory of island biogeography and human activities

Understanding how the complexities of biodiversity are maintained on islands has long been one of the central issues studied in conservation biology. With the global onset of anthropogenically driven biodiversity changes, the influence of anthropogenic activities challenges the applicability of the widely accepted Equilibrium Theory of Island Biogeography (ETIB). This study aimed to test how island area, isolation (MD: distance to the mainland, and ND: distance to the nearest island), and human activities (habitat heterogeneity, and proportion of road area relative to island area to refer to the human impact on island) separately and jointly affect the species diversity of vascular plants. The number of plant species with different growth forms (woody plants, herbs, and lianas) was calculated on 35 islands in Sanyang Wetland, which is a human-dominated wetland near the highly populated city of Wenzhou, China. We also evaluated the relative importance of these variables on the number of species using a random forest analysis. The number of species increased with increasing island area and habitat heterogeneity and decreased with increasing isolation for different growth forms. A significant, positive relationship was observed between the number of species and the proportion of road area for herbs, but not for woody plants and lianas. Habitat heterogeneity was the most important predictor for all plants, the proportion of road area was the most important predictor for herbs, and MD was the most important predictor for woody plants and lianas. These results indicate that ETIB remains relevant in the context of human disturbance, but the relative importance of ecological processes on species diversity differs significantly among plant growth forms. Therefore, we should consider plant functional groups when testing multifactorial effects on species diversity on human-dominated islands.

Thermography captures the differential sensitivity of dryland functional types to changes in rainfall event timing and magnitude.

Drylands of the southwestern United States are rapidly warming, and rainfall is becoming less frequent and more intense, with major yet poorly understood implications for ecosystem structure and function. Thermography-based estimates of plant temperature can be integrated with air temperature to infer changes in plant physiology and response to climate change. However, very few studies have evaluated plant temperature dynamics at high spatiotemporal resolution in rainfall pulse-driven dryland ecosystems. We address this gap by incorporating high-frequency thermal imaging into a field-based precipitation manipulation experiment in a semi-arid grassland to investigate the impacts of rainfall temporal repackaging. All other factors held constant, we found that fewer/larger precipitation events led to cooler plant temperatures (1.4°C) compared to that of many/smaller precipitation events. Perennials, in particular, were 2.5°C cooler than annuals under the fewest/largest treatment. We show these patterns were driven by: increased and consistent soil moisture availability in the deeper soil layers in the fewest/largest treatment; and deeper roots of perennials providing access to deeper plant available water. Our findings highlight the potential for high spatiotemporal resolution thermography to quantify the differential sensitivity of plant functional groups to soil water availability. Detecting these sensitivities is vital to understanding the ecohydrological implications of hydroclimate change.

Vegetation response to a natural gas pipeline rupture fire in Canada’s montane cordillera

Pipelines are critical for energy distribution, but incidents causing rupture fires are hazardous. While wildland fires are a natural disturbance, rupture fires are a potential risk and novel disturbance given the greater heat yield constants for fossil fuels, fuel volume, and flaming concentration and duration. We quantified vegetation response to a 2018 rupture fire case study in the montane cordillera of Canada. Plant species, functional groups, ground cover, and live vegetation height were sampled in 2018, 2019, 2020, and 2021 [0, 1, 2, and 3 years since fire (YSF)] in permanent plots stratified by burn severity and compared to the unburned reference plots sampled in 2019. Woody plant species and forb cover in burned plots recovered to levels similar to unburned plots. Litter and bare soil changes relative to YSF suggest trajectories to return to levels similar to unburned plots within 3 to 5 years post-rupture. Plant species richness, evenness, and diversity had also recovered to levels statistically similar to unburned comparisons by the final year of sampling in this study. Plots closest to the rupture epicenter that experienced ‘extreme’ burn had greater botanical dissimilarity from other burn severities or unburned comparisons. Vegetation structure showed significant (p < 0.0001) recovery with additional growth expected as the overstory re-establishes. The multiple metrics of ecological recovery on 3–5 year trajectories are comparable to published responses to wildland fire in the literature for this ecosystem’s response to fire. The recovery of conifers and soil microbiota should be assessed in the next decade.

Beyond the Hydro-Regime: Differential Regulation of Plant Functional Groups in Seasonal Ponds

Plant community assembly can be influenced by many environmental factors. In seasonal wetlands, most studies focus on the considerable variation that occurs from the hydro-regime (patterns of inundation and desiccation). Other factors and their interactions also influence plants but are seldom studied, including nutrient and thatch levels. Furthermore, the responses of aquatic and terrestrial functional groups can provide important insights into patterns of cover and richness. The aim of this study was to evaluate how algae and plant functional groups (aquatic and terrestrial plants) respond to variation in hydro-regime (stable and unstable), nutrient addition (none and added), and thatch (none, native plants, and exotic plants) addition. We measured algal cover, total species richness, and the cover of the functional groups over two years. Algal cover increased with unstable hydroperiods and the addition of nutrients. Algae were also negatively associated with aquatic plant cover and positively associated with terrestrial plant cover. Aquatic plant cover increased with a stable hydro-regime and decreased with increased thatch. Terrestrial plant cover increased with an unstable hydro-regime and decreased with thatch addition. Thatch accumulation and excess nutrients can be linked to human activities, which directly and indirectly alter plant community composition. The interactions of these factors with the hydro-regime should be considered when evaluating a plant community’s response to changing environmental conditions. Overall, these results are necessary for the conservation and management of essential wetland functions and services.

Restoration of invaded temperate grasslands: species phenology adds to microsite and seed availability

AbstractQuestionsRestoring diversity in temperate grasslands requires eliminating invaders and recovering different native phenological groups. Clipping and seed addition promote native grass recovery, but these effects could depend on the phenological overlap between invaders and native species. We evaluated the importance of the interaction between two types of clipping, species phenology and sowing to restore temperate grasslands invaded by the cool‐season forage species Festuca arundinacea (tall fescue).LocationFlooding Pampa grassland (Buenos Aires, Argentina).MethodsWe applied selective and non‐selective clipping on tall fescue during the peak growing season, combined with the sowing of native cool‐ and warm‐season grasses. Plant species cover was estimated visually for 3 years; species were categorized by functional groups. Moreover, through emergence trials, we evaluated whether the soil seed bank had been impoverished by invasion.ResultsRegardless of selectivity, clipping decreased tall fescue cover by 12%/year, which reduced microsite limitation. Consequently, total native richness increased by 5 spp./year and cover increased from 3% to 50% by the last experimental year, independent of clipping type. Moreover, native warm‐season grasses, the group with the least phenological overlap with invaders, increased by nearly 25% in cover and by 5 spp./m2 with clipping and independently of sowing. Contrarily, native cool‐season grasses, with more phenological overlap with invaders, increased 5% with propagule addition. Furthermore, the seed bank was enriched with tall fescue and depleted of cool‐season grasses.ConclusionsOur results reveal that overcoming microsite limitation is a necessary condition to restore plant diversity in grassland invaded by tall fescue. Nevertheless, seed limitation and phenological overlap may be particularly important to restore the diversity of some native functional groups of plants. Considering the phenology of species can help to identify either clipping targets or phenological groups to be sown when restoring native diversity.