Search Results (6)

In terrestrial ecosystems, the decomposition of early spring ephemeral plant litter (ESPL for short) is one of the important processes in the carbon and nutrient cycles during the early spring stage. The current study focused on four typical spring ephemeral plant species in three forest types of Northeast China and investigated the decomposition characteristics of herb litters, using litterbag decomposition experiments. The study results indicate that the mass loss rate of ESPL decomposition after 50 days can be as high as 73.15% to 80.44%. Throughout the entire decomposition period, there is a significant correlation between the decomposition of ESPL and time, with initial decomposition relatively fast and later decomposition slowing down. Overall, Hylomecon japonicum exhibits slightly faster decomposition, and Cardamine leucantha decomposes relatively slowly, while Cardamine leucantha shows the highest mass loss rate in the first 10 days, reaching 38.71%. The mass loss rates of the four types of ESPL are significantly correlated with the litter nutrient conditions, as are the stage-specific mass loss rates. Furthermore, there are distinct differences in the nutrient composition affecting the decomposition of different types of ESPL. Across different forest stands, influenced by different decomposition environments, such as soil conditions, the decomposition of ESPL is fastest in the deciduous broad-leaved forest, with decomposition reaching 50% and 95% in only 15–18 days and 63–88 days, respectively. In the broad-leaved forest, it takes 18–23 days and 78–110 days, while, in the birch forest, it takes 22–32 days and 99–136 days. Full article

Deliblato Sands is the single largest expanse of sand in Europe. It is the most fire-prone area of Serbia due to the absence of surface water, sandy soils, specific microclimate conditions, and vegetation composition. Post-fire regeneration is a long-term process that includes many aspects of vegetation regrowth and habitat recovery. In the third year following one of the disastrous fires, the growth dynamics of two geophyte species in unburned and burned sites were studied. During the growing season, burned and unburned populations of Crocus reticulatus Steven ex Adam and Iris pumila L. were assessed for growth parameters (biomass production, specific leaf area, leaf area index) and leaf-level ecophysiological traits (photosystem II efficiency, chlorophyll amount, relative water content). Species acclimated differently to changed abiotic and biotic site conditions after the fire event. C. reticulatus burned and unburned populations differed significantly in terms of flowering phenology and ecophysiological traits, whereas I. pumila burned and unburned populations differed significantly in terms of growth parameters. The findings support the assertion that geophytes are generally well adapted to environmental disturbances. Species, however, responded differently to fire-induced changes in the physicochemical and biotic environment, depending on their ecological requirements and adaptive capacity. Full article

Future climate is projected to increase in the intensity and frequency of extreme precipitation events, and the resulting ecological consequences are often more serious than those of normal precipitation events. In particular, in desert ecosystems, due to the low frequency and strong fluctuation of extreme precipitation, the destructive consequences for desert plants caused by extreme precipitation have not received enough attention for some time. Based on statistics of extreme precipitation events (1965–2018) in the Gurbantunggut Desert, we investigated the effects of extreme precipitation (+0%, CK; +50%, W1; +100%, W2; +200%, W3; maintenance of field capacity, W4) on the plant life-history of the spring-germinated (SG) and autumn-germinated (AG) ephemeral plant Erodium oxyrhynchum by monitoring seedling emergence, survival, phenology, organ size, biomass accumulation, and allocation. The results showed that extreme precipitation caused about 2.5% seedling emergence of E. oxyrhynchum in autumn 2018 and 3.0% seedling emergence in early spring 2019, which means that most seeds may be stored in the soil or have died. Meanwhile, extreme precipitation significantly improved the survival, organ size, and biomass accumulation of SG and AG plants, and W3 was close to the precipitation threshold of SG (326.70 mm) and AG (560.10 mm) plants corresponding to the maximum individual biomass; thus, AG plants with a longer life cycle need more water for growth. Conversely, W4 caused AG plants to enter the leaf stage in advance and led to death in winter, which indicates that extreme precipitation may not be good for AG plants. Root and reproduction biomass allocation of SG and AG plants showed a significantly opposite trend under extreme precipitation treatments, which might be related to their different life-history strategies. Therefore, when only taking into account the changing trend of extreme precipitation from the Coupled Model Intercomparison Project 6 (CMIP6) climate projections data, we speculate that extreme precipitation may promote the growth of SG and AG plants from the beginning to the middle of this century, but extreme precipitation in autumn exceeding a certain threshold may adversely affect the survival of AG plants at the end of the century. Full article

Fire exclusion has dramatically altered historically fire adapted forests across western North America. In response, forest managers reduce forest fuels with mechanical thinning and/or prescribed burning to alter fire behavior, with additional objectives of restoring forest composition, structure, and ecosystem processes. There has been extensive research on the effects of fuel reduction and restoration treatments on trees, fuels, regeneration, and fire behavior; but less is known about how these treatments influence understory vegetation, which contains the majority of vascular plant diversity in many dry conifer forests. Of particular interest is how understory vegetation may respond to the season and interval of prescribed burning. The season and interval of prescribed burning is often determined by operational constraints rather than historical fire regimes, potentially resulting in fire conditions and burn intervals to which native plants are poorly adapted. In this study, we examined how understory vegetation has responded to season and interval of prescribed burning in ponderosa pine (Pinus ponderosa) forests in the Blue Mountains of northeastern Oregon, USA. Using over a decade (2002–2015) of understory vegetation data collected in stands with different intervals (5 versus 15 year) and seasons (spring versus fall) of prescribed burning, we quantified how season and interval of prescribed burning has influenced understory vegetation compositional trajectories and indicator species over time. Season of prescribed burning resulted in different understory communities and distinct trajectories of understory composition over time, but interval of burning did not. Indicator species analysis suggests fall burning is facilitating early seral species, with native annual forbs displaying ephemeral responses to frequent burning, while invasive cheatgrass (Bromus tectorum) increased in abundance and frequency across all treatments over time. These findings indicate that understory vegetation in these ecosystems are sensitive to seasonality of burning, but the responses are subtle. Our findings suggest season and interval of prescribed burning used in this study do not result in large changes in understory vegetation community composition, a key consideration as land managers increase the pace and scale of prescribed fire in these forests. Full article

Spring ephemeral plants (SEP) are a particular component of flora that take full advantage of water resources and temperature conditions to rapidly complete their life cycle in about two months. In China, they are mainly distributed in northern Xinjiang. They play important roles in dune stability and are precious food for the livestock and wild animals in the early spring. Northern Xinjiang is under dramatic climate changes and land-use/land-cover changes, which can affect the growth of SEP in this region. To explore how the distribution of SEP have varied under these changes, Moderate-Resolution Imaging Spectrodiometer (MODIS) Enhanced Vegetation Index (EVI) time series of two years (2000 and 2014) were applied to detect SEP in each period. The TIMESAT software was used to extract the seasonality information from the EVI data. The results show that SEP in northern Xinjiang are mainly located in the south of the Gurbantunggut desert and along the Ili Valley and piedmont hills of the mountains. In 2000, its total area was 3.83 × 10⁴ km², accounting for 10% of the entire region. By 2014, the total area was about 2.74 × 10⁴ km², with a decrease of 28.5% relative to 2000. Land-use/land-cover datasets can be used to determine whether changes in SEP over time are caused by human activities or natural factors. Combing the SEP maps with the synchronous land-use/land-cover datasets indicates that the decrease is mainly caused by natural factors, which are possibly related with the temperature and precipitation changes in this region. Human activities only contributed 4% to the decrease, with most SEP areas being replaced by croplands. The observed SEP dynamics and changes pertain only to the years with below-average precipitation. Full article

While negative impacts of invasive species on native communities are well documented, less is known about how these communities respond to the removal of established populations of invasive species. With regard to invasive shrubs, studies examining native community response to removal at scales greater than experimental plots are lacking. We examined short-term effects of removing Lonicera maackii (Amur honeysuckle) and other non-native shrubs on native plant taxa in six mixed-hardwood forests. Each study site contained two 0.64 ha sample areas—an area where all non-native shrubs were removed and a reference area where no treatment was implemented. We sampled vegetation in the spring and summer before and after non-native shrubs were removed. Cover and diversity of native species, and densities of native woody seedlings, increased after shrub removal. However, we also observed significant increases in L. maackii seedling densities and Alliaria petiolata (garlic mustard) cover in removal areas. Changes in reference areas were less pronounced and mostly non-significant. Our results suggest that removing non-native shrubs allows short-term recovery of native communities across a range of invasion intensities. However, successful restoration will likely depend on renewed competition with invasive species that re-colonize treatment areas, the influence of herbivores, and subsequent control efforts. Full article