Removal Plots Research Articles

Changes in plant resource inputs lead to rapid alterations in soil dissolved organic matter composition in an old-growth tropical forest

Alterations in plant resource inputs to soil affect soil organic matter (OM) dynamics. However, it remains unclear how to alter soil dissolved OM (DOM) composition. Here, we used UV/fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry to analyze soil DOM’s optical and molecular characteristics after eight months of detritus input and removal in an old-growth tropical forest. Changes in plant inputs significantly altered soil DOM’s optical properties, and the most pronounced changes were observed in the humification index and fluorescent components. In litterfall removal and no-input plots, molecular characteristic values increased greatly, such as O/C, double-bond equivalent, aromaticity index, and proportion of carboxyl-rich alicyclic molecules, while biolabile compounds decreased. The abundance of lignin-like and tannin-like compounds was more than 20 % higher in litter removal plots than in no-input plots. Our findings indicate that changes in plant resource inputs can lead to rapid alterations in soil DOM composition.

Response of soil microbial diversity and functionality to snow removal in a cool-temperate forest

Climate-induced changes in thinning snowpack can greatly impact soil freeze-thaw patterns and water supply. These effects may influence the soil microbial diversity and the key ecological functions mediated by microorganisms, thereby altering the cycling of nutrient in the ecosystem. A snow-exclusion experiment to explore the effects of snow removal on soil microbial diversity and functionality in Larix gmelinii forest. Control (natural snowfall), SR (complete snow removal) and SR-SR (complete snow removal, with snow returned for water supplementation at the end of winter) were represented three experimental treatments. The results showed that: snow removal resulted in more severe soil frost in winter. Soil nitrogen availability was higher in the snow removal plots compared to control plots in freeze-thaw period. Fungal diversity was not affected by snow removal, neither the α diversity of bacteria. However, snow removal did alter the bacterial community structure. These changes of the above did not persist into the growing season. SR-SR significantly reduced soil multifunctionality during freeze-thaw period, whereas SR did not. However, SR and SR-SR resulted in significantly higher soil multifunctionality than was observed in control during early growing season. Additionally, a widespread increase in the abundance of nitrogen cycling genes was observed in the SR and SR-SR plots during the freeze-thaw period and the early growing season, respectively. Snow removal significantly affected soil multifunctionality, which can be explained by changes in the microbial biomass, bacterial community structure and network complexity. Furthermore, snow removal significantly altered soil water content, temperature, and dissolved carbon, nitrogen. dbRDA and random forest analysis showed that soil water content, temperature, and total nitrogen as drivers of soil microbial community structure and multifunctionality. This study highlights that snow removal altered soil nitrogen availability, microbial community diversity, and multifunctionality during freeze-thaw period. However, these changes did not result in cross-seasonal legacy effects.

Restoring the threatened Scalesia forest: insights from a decade of invasive plant management in Galapagos

Island forests are becoming increasingly fragmented and colonized by invasive species, which can eventually lead to local species extinctions. In the Galapagos Islands, invasive species pose a serious extinction threat to the endemic daisy tree Scalesia pedunculata, formerly the dominant habitat-forming species of the unique Scalesia forest. This forest has been reduced to fragments due to land use changes in the past and is now increasingly invaded by introduced plants. We conducted a field experiment on Santa Cruz Island to assess the impacts of blackberry (Rubus niveus) and two other invasive plant species, Cestrum auriculatum and Tradescantia fluminensis, as well as the effects of the removal of two of these (R. niveus and C. auriculatum) on cover, composition and diversity of the resident plant communities. Particular attention was paid to effects of the invasive species on the S. pedunculata population. Annual vegetation monitoring was carried out in a total of 34 permanent plots (10 m × 10 m) over 10 years (2014–2023), using the line-intercept method. Seventeen of these plots were established in an invaded area and 17 plots in an area with continuous invasive plant removal since 2014. Results indicated that there were significant changes in both the species composition of the plant communities and average percent cover of species over time, comparing removal plots with invaded plots. Species composition in removal plots changed significantly more than in invaded plots, towards a plant community with greater percent cover of endemic species. A significant negative relationship between the three invasive species and cover of S. pedunculata suggested that multiple invader species may have additive negative impacts. Natural recruitment of S. pedunculata by seeds was observed in the removal but not in the invaded plots. These results, as well as the striking decrease of 71% in cover of adult S. pedunculata in the invaded plots indicate that this threatened species will be driven to local extinction on Santa Cruz Island, Galapagos, in less than 20 years if invasive plant species are not removed on a large scale.

Rice residue management alternatives in rice–wheat cropping system: impact on wheat productivity, soil organic carbon, water and microbial dynamics

In the Indo-Gangetic Plains (IGP), rice–wheat cropping system (RWCS) predominates, producing large quantity of crop residue and its management is major concern. Farmers usually burn the residue to clear the field for succeding crop, and burning damages soil microbes, resulted in loss of soil organic matter. Hence, current study was conducted to assess the impact of different Happy seeder based residue management options on changes in microbial dynamics, enzyme activities and soil organic matter content and also to know that alternative method for attaining sustainable wheat productivity in sandy loam soils of Haryana, India. Results revealed that Zero tillage wheat (ZTW) with partial and full residue retention treatments sown with Happy seeder (after using chopper and spreader), and ZTW with anchored stubbles significantly enhanced soil microbial count by 47.9–60.4%, diazotropic count by 59.0–73.1% and actinomycetes count by 47.3–55.2%, grain yield by 9.8–11.3% and biomass yield by 7.4–9.6% over conventional tilled (CT) residue burning and residue removal plots. ZTW sown with surface retention of rice crop residue increased the organic carbon by 0.36–0.42% and the soil moisture content by 13.4–23.6% over CTW without residue load. Similarly, ZTW sown with Happy seeder with full residue enhanced alkaline phosphatase activity from 95.3 µg TPF g−1 soil 24 h−1 in 2018–2019 to 98.6 µg TPF g−1 soil 24 h−1 in 2019–2020 over control plots. Likely, microbial population and enzymatic activity showed strong positive correlation under variable residue retention practices. However, increased microbial population reduced the soil pH from 7.49 to 7.27 under ZTW with residue retention plots. The wheat yield enhanced by 9.8–11.3% during 2018–2019 and 2019–2020 under ZTW with Happy seeder with full residue load over residue burning and residue removal plots. ZTW sown with Happy seeder under full residue retention, achieved maximum net return 43.16–57.08 × 103 ₹ ha−1) and B-C ratio (1.52 to 1.70) over CTW without residue. Therefore, rice residue needs to be managed by planting wheat using appropriate machinery under ZT for sustaining higher productivity in RWCS and improve soil health and environment under IGP regions.

Effect of seaweed canopy disturbance on understory microbial communities on rocky shores

IntroductionThe collapse of macroalgal habitats is altering the structure of benthic communities on rocky shores globally. Nonetheless, how the loss of canopy-forming macroalgae influences the structure of epilithic microbial communities is yet to be explored. MethodsHere, we used experimental field manipulations and 16S-rRNA-gene amplicon sequencing to determine the effects of macroalgal loss on the understory bacterial communities and their relationship with epiphytic bacteria on macroalgae. Beds of the fucoid Hormosira banksii were exposed to different levels of disturbance resulting in five treatments: (i) 100% removal of Hormosira individuals, (ii) 50% removal, (iii) no removal, (iv) a procedural control that mimicked the removal process, but no Hormosira was removed and (v) adjacent bare rock. Canopy cover, bacterial communities (epilithic and epiphytic) and benthic macroorganisms were monitored for 16 months.ResultsResults showed that reductions in canopy cover rapidly altered understory bacterial diversity and composition. Hormosira canopies in 50% and 100% removal plots showed signs of recovery over time, but understory epilithic bacterial communities remained distinct throughout the experiment in plots that experienced full Hormosira removal. Changes in bacterial communities were not related to changes in other benthic macroorganisms.DiscussionThese results demonstrate that understory epilithic bacterial communities respond rapidly to environmental disturbances at small scales and these changes can be long-lasting. A deeper knowledge of the ecological role of understory epilithic microbial communities is needed to better understand potential cascading effects of disturbances on the functioning of macroalgal-dominated systems.

Sea‐weeding: Manual removal of macroalgae facilitates rapid coral recovery

Abstract Coral reef ecosystems globally are under threat, leading to declining coral cover and macroalgal proliferation. Manually removing macroalgae (i.e. ‘sea‐weeding’) may promote local‐scale coral recovery by reducing a biological barrier, though the impact of removal on community composition of benthic reef organisms has not been quantified. In this three‐year study (2018–2021), fleshy macroalgae (predominantly Sargassum spp.) were periodically removed from 25 m2 experimental plots on two inshore fringing reefs of Yunbenun (Magnetic Island) in the central Great Barrier Reef. By the end of the study, coral cover in removal plots (n = 12 plots) assessed through in‐field transects increased by at least 47% (2019 mean: 25.5%, 2021 mean: 37.4%), and macroalgal cover decreased by more than half. In contrast, in control plots (n = 12 plots), there was no change in macroalgal cover while coral cover remained stable (2019 mean: 16.4%, 2021 mean: 13.6%). Changes in benthic cover were supported by photoquadrat data, with Bayesian probability modelling indicating a 100% likelihood that coral cover more than doubled in removal plots over the study period, compared to only a 29% chance of increased coral cover in control plots. Synthesis and applications. Manual macroalgal removal can provide rapid benefits and enhance inshore coral reef recovery. Through involvement of community groups and citizen scientists, larger scale removal of macroalgae is a low‐tech, high‐impact, and achievable method for local reef management.

Community structure and recovery in cryptic intertidal communities reflects dynamics on open‐surface communities

AbstractResearch on intertidal community structure and recovery in the California Current System has largely focused on macrophytes and invertebrates occupying two‐dimensional, readily studied “open” rock surfaces. However, most rocky shores have a “third” dimension that includes channels, cracks, crevices, and overhangs whose organismal assemblages, termed “cryptic communities,” are poorly studied. Cryptic communities not only share many species with those on more accessible surfaces but also include high abundances of colonial invertebrates such as tunicates, sponges, bryozoans, and hydrozoans. We investigated species abundance and diversity of cryptic communities and tested their recovery from disturbance by comparing removal plots to undisturbed controls for ~1.5 years. Additionally, we tested whether community structure and recovery varied with contrasting large‐scale levels of ecological subsidies (invertebrate recruitment, nutrients, and phytoplankton) and local‐scale microhabitat differences (emersion and solar irradiation) on the Oregon Coast. We compared cryptic recovery rates to recovery rates on open‐surface communities. In cryptic communities, site explained most (92%) variance in community structure of undisturbed plots, while microhabitat metrics had little (1.2%) effect. Further, recovery rates were faster at a site with higher subsidy inputs than one with lower subsidies in both cryptic and noncryptic communities. Hence, larger scale environmental drivers appeared more important than local‐scale drivers within cryptic communities. Our research provides novel insight into intertidal cryptic surge channel community structure and dynamics.

Droplets impact against the random rough surface with a liquid film

Aero-engine fouling will affect the economy and safety of aircraft, and online washing is the main method to solve the problem of aero-engine fouling. Online washing is considered to be the removal of fouling particles by the impingement of droplets on a flowing liquid film. Here, we simulate a flowing liquid film of droplets impinging on a randomly rough surface to predict the removal of fouling particles. We considered the situation that the horizontal flow velocity of the liquid film is between 5 and 20 m/s and the thickness of the liquid film is 5–20 μm. An analysis of the droplet impact velocity field, radial velocity, and extension length shows that the vortex strength, radial velocity, and extension length all increase with increasing liquid film flow velocity, while increasing liquid film thickness inhibits the growth. Moreover, we constructed a fouling particle detachment model to evaluate the effects of different liquid film flow velocities and film thicknesses on particle removal. A particle removal plot shows the dominance of liquid film flow velocity stations. This study not only reveals the removal process of fouling particles on random rough surfaces but also provides insight into the optimization of spray cleaning process parameters.

Residual effect of shredded cotton (Gossypium species) stalks and fertility levels on productivity, quality parameters and economics of sweet corn (Zea mays)

A field experiment was carried out during the winter (rabi) season of 2020–21 on sandy clay loam soil of College of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, to study the effect of incorporation of cotton (Gossypium sp.) stalk on soil-fertility status and yield of succeeding sweet corn (Zea mays L.). The treatments comprised 2 levels of residue management, viz. shredded cotton stalks incorporation and no incorporation, and 5 fertility levels, viz. control, 75% Recommended dose of fertilizer (RDF), 100% RDF, 125% RDF and 150% RDF, making 10 treatment combinations. There was no significant impact of residue incorporation on yield and quality parameters of sweet corn over the residue removal but NPK uptake was enhanced with cotton-stalk incorporation. However, higher net returns and benefit : cost (B : C) ratio were obtained with residue removal plots. An application of 150% RDF (300 : 90 : 75 kg NPK/ha) resulted in the significant increase in yield and was at par with 125% RDF (250 : 75 : 62.5 kg NPK/ha). Quality parameter, viz. crude protein (11.6%), was higher with the application of 150% RDF, being at par with 125% RDF. The higher gross returns, net returns and B : C ratio were obtained with 150% RDF. It would be, therefore, advisable to apply 125% RDF (250 : 75 : 62.5 kg NPK/ha) to sweet corn. The interaction effect between residue management and fertility levels was non-significant for all the parameters of sweet corn.

Restoration Contributes to Maintain Ecosystem Services and Bio-Cultural Linkages Between Wetlands and Local Communities: a Case from a Botanical Diversity Hotspot in Japan.

The online version contains supplementary material available at 10.1007/s13157-022-01639-2.

Litter removal impacts on soil biodiversity and eucalypt plantation development in the seasonal tropics

The little layer of tree plantations provides primary nutrients for uptake, buffers changes in soil moisture, and provides habitat and substrate to soil epigeic fauna. However, this layer in eucalypt plantations is often removed to reduce fuel load during the fire season in the Brazilian savanna (Cerrado). Therefore, it is necessary to quantify the effects of changes in litter dynamics on the function of these plantations, on key nutrient cycling processes and on epigeic fauna diversity and abundance. In two adjacent stands (one juvenile and one mature), the consequences of two years of litter removal were quantified as monthly litterfall, leaf and fine wood litter decomposition, epigeic fauna abundance and diversity, soil biogeochemical variables, and tree diameter and basal area increments. Monthly litterfall rates in juvenile and mature stands did not change with litter removal over the study period. Annual litterfall ranged from 4.1 to 4.9 Mg ha−1a−1 in litter removal plots and from 3.9 to 4.8 Mg ha−1a−1 in control plots. Fine wood litter decomposition was slower in litter removal plots compared to controls, while leaf decomposition rates were similar in both. Two years of litter removal in the juvenile stand did not affect topsoil biogeochemical parameters but decreased available phosphorus at 20–40 cm depth relative to controls. In the mature stand, total cation exchange capacity (0–20 cm) was higher in controls (6.4 cmolc dm−3) relative to litter removal plots (6.3 cmolc dm−3), while soil moisture (0–40 cm depth) was lower in litter removal (25.45 m3 m−3) compared to control plots (26 m3 m−3) in the dry season. A non-metric multidimensional scaling ordination revealed an increased homogeneity in epigeic fauna where litter was removed. Litterfall, decomposition, diameter increment, four soil physical parameters and fourteen chemical parameters at 0–20 and 20–40 cm depth explained the differences in soil epigeic fauna composition between litter removal and control plots. Diameter increment decreased with litter removal only in the juvenile stand, which had reached its growth peak. The results indicate that removing excess litter to decrease fuel volume can alter soil biodiversity and edaphic conditions that negatively affect nutrient cycling and tree growth.

Wrack enhancement of post-hurricane vegetation and geomorphological recovery in a coastal dune

Coastal ecosystems such as sand dunes, mangrove forests, and salt marshes provide natural storm protection for vulnerable shorelines. At the same time, storms erode and redistribute biological materials among coastal systems via wrack. Yet how such cross-ecosystem subsidies affect post-storm recovery is not well understood. Here, we report an experimental investigation into the effect of storm wrack on eco-geomorphological recovery of a coastal embryo dune in north-eastern Florida, USA, following hurricane Irma. We contrasted replicated 100-m2 wrack-removal and unmanipulated (control) plots, measuring vegetation and geomorphological responses over 21 months. Relative to controls, grass cover was reduced 4-fold where diverse storm wrack, including seagrass rhizomes, seaweed, and wood, was removed. Wrack removal was also associated with a reduction in mean elevation, which persisted until the end of the experiment when removal plots had a 14% lower mean elevation than control plots. These results suggest that subsides of wrack re-distributed from other ecosystem types (e.g. seagrasses, macroalgae, uplands): i) enhances the growth of certain dune-building grasses; and ii) boosts the geomorphological recovery of coastal dunes. Our study also indicates that the practice of post-storm beach cleaning to remove wrack–a practice widespread outside of protected areas–may undermine the resilience of coastal dunes and their services.

The organic layer reduces water repellency of surface mineral soil under a humid-temperate forest

Surface soil under forests often shows soil water repellency (SWR). The organic (O) layer (e.g., litter layer) and SWR are both well known to affect water movements on hillslopes, yet little is known about their interaction. In this research, we established five O-layer removal (no O layer; NO) plots and seven O-layer remaining (with O layer; WO) plots on the same slope, which had developed thick O layers, and repeatedly measured in situ SWR and moisture content of surface mineral soil at multiple points in each plot. We calculated the percentage of water repellent points (SWRarea) in each plot and found lower SWRarea and higher soil moisture content in WO plots. SWR in WO plots was more spatially heterogeneous; some measurement points frequently showed SWR, and other points were frequently wettable. The frequently water repellent points were drier than those frequently wettable. NO plots, on the other hand, showed large SWRarea more often than did WO plots. These findings imply that O layers could reduce surface runoff via decreasing in situ SWR and cause preferential water flow by maintaining both SWR and wettable regions.

Macroalgal canopies provide corals limited protection from bleaching and impede post-bleaching recovery

Coral bleaching, the result of loss of endosymbiotic dinoflagellates, as well as post-bleaching recovery can be exacerbated or mitigated by a range of local factors such as depth, turbidity, and natural or artificial shading providing protection for corals during thermal anomalies. On many reefs, losses in coral cover coincide with increases in upright macroalgae growth. Such shifts in benthic communities are generally viewed as negative, whereby macroalgae can outcompete corals for space, and affect adult coral health and fitness. However, the canopy provided by upright macroalgae could reduce solar irradiance and provide refuge for understorey corals during heat events, decreasing coral bleaching and subsequent mortality. To test this hypothesis, this study manually removed macroalgae from experimental plots on a macroalgae-dominated fringing reef at Magnetic Island in the central inshore region of the Great Barrier Reef, comparing the subsequent bleaching during and recovery following a severe heat stress event. In March 2020, sea surface temperature at Magnetic Island reached 31.4 °C, leading to bleaching. Surveys of coral communities undertaken at the peak of accumulated severe heat stress (DHW of 9.3 °C-weeks) in control and macroalgae removal plots showed that, averaged across coral morphological groups, there was no overall difference in bleaching prevalence in algal-removal and control plots (21.1% and 20.8% of the community bleached; respectively). However, bleaching prevalence varied within morphological groups, with massive morphology corals demonstrating higher probability of bleaching in removal plots compared to controls (0.26 and 0.09, respectively). Bleaching severity (i.e. percent of the colony tissue bleached) was consistent across control and removal plots (83.2% and 80.4% of colony area, respectively, averaged across morphologies), with branching corals demonstrating the lowest severity. Surveys were repeated in July after heat stress had dissipated, with coral communities in algal-removal plots displaying greater recovery than controls (i.e. 86.1% and 75.6% healthy, respectively, model estimated mean averaged across morphologies). Encrusting corals in control plots were the slowest to recover. We conclude that macroalgae provided limited refuge for branching and encrusting corals at the height of the thermal event, likely due to the severity of the accumulated heat stress, while massive corals enjoyed some degree of protection from the canopy. Greater recovery of coral communities in removal plots may potentially be explained by reduced competition with adjacent macroalgae. This study provides important insights into the interactions between these two dominant benthic groups and supports previous work finding macroalgae inhibits coral recovery after severe bleaching events.

Characterization of Soil Pores Through X-Ray Computed Microtomography and Carbon Mineralization Under Contrasting Tillage and Land Configurations in the Indo-Gangetic Plains of India

Contrasting tillage and land configuration have important roles in porosity and pore size distribution (PSD), which in turn affects the carbon mineralization in soil. Information on the effects of these treatments on PSD and subsequent carbon mineralization is very limited. Hence, an attempt was made to evaluate the long-term impact of soil tillage and land configurations on the distribution of soil pores and its relationship with soil carbon mineralization under a maize (Zea mays)-wheat (Triticum aestivum) rotation. There were five treatments, that is, conventional tillage, (CT); permanent broad bed, (PBB); PBB + residue (R); zero tillage, (ZT); and ZT + R. Soil pores were quantified by X-ray computed tomography (μ-CT). The conversion of CT to ZT and PBB with or without residue retention (+R) resulted in the reduction of pores >60 μm diameter and was mostly due to a reduction in the number of larger size macro-pores (>110 μm). This resulted in restricted drainage. However, under these practices, pores with larger diameters (60–110 μm) facilitated soil aeration. The total organic carbon (TOC) was 15–48% and 17–47% higher under PBB, PBB + R, ZT, and ZT + R than that under CT in the 0–5 and 5–15 cm layers. The highest MWD (1.01 mm) was in the plots under PBB + R, and the lowest was in the CT plots, and all residue-retained plots (ZT + R and PBB + R) had a higher MWD than residue removal plots (ZT and PBB). Relative to CT, soil C mineralization rates in 0–5 and 5–15 cm soil depths were 63 and 55% higher in the alternate tillage practices, respectively, and the highest value occurred in PPB + R treatments. Increased labile C concentrations were indicative of greater mineralization and were correlated with pores >60 μm, particularly in the size range 110–500 μm and TOC concentrations of 0–15 cm soil layer. Thus, the transition to alternate tillage from the conventional tillage enhanced soil organic carbon concentration (16–47.5%), improved soil structure, reduced the diameter of pores up to >60 μm, and facilitated C mineralization by altering the pore size distribution of soil under a maize-wheat system in the IGP.

Diversity and Seasonal Occurrence of Native and Nonnative Ants (Hymenoptera: Formicidae) in Long-Term Experimental Chinese Privet (Lamiales: Oleaceae) Plots in Georgia, USA

Diversity and Seasonal Occurrence of Native and Nonnative Ants (Hymenoptera: Formicidae) in Long-Term Experimental Chinese Privet (Lamiales: Oleaceae) Plots in Georgia, USA

Reinvasion of Native Invasive Trees After a Tree-Thinning Experiment in an African Savanna

Woody plant encroachment has serious negative consequences for ranchers because of the reduction in herbaceous fodder for domestic livestock. A long-term monitoring of a tree-thinning experiment was established near Magudu (northern KwaZulu-Natal, South Africa) in 1990. The objective of this experiment was to determine the optimal tree density that would maximize grass production while benefiting grasses from nitrogen fixation, hydraulic lift, and/or shade from the leguminous trees. The initial dominant species was the nitrogen-fixing tree, Dichrostachys cinerea. There were 12 plots (6 pairs) with trees removed to approximate 0, 179, 277, 428, and 625 trees ha−1, with 1 pair left as a control (unmanipulated). One plot of each replicate (except the controls) was treated with short-acting herbicide (picloram) once in 1990. We collected data on herbaceous cover and species composition, tree species composition, sizes, and mortality. We also used remote sensing to examine the patterns of herbaceous cover. Herbaceous biomass decreased as tree density increased. After 30 yr, the same dominant tree species (D. cinerea) had reinvaded all the removal plots despite the fact that several encroaching species (Vachellia karroo, V. tortilis, V. nilotica) occurred in these plots. These D. cinerea trees were mostly less dense and contained many more juvenile individuals in the cleared and partially cleared plots than those in the control plots after 30 yr. Should maximizing herbaceous cover be the goal, repeated brush management would be necessary to maintain adequate control of woody plants in these savannas.

Effects of snow manipulation on larch trees in the taiga forest ecosystem in northeastern Siberia

Changes in winter precipitation (snow) may greatly affect vegetation by altering hydrological and biochemical processes. To understand the effects of changing snow cover depth and melt timing on the taiga forest ecosystem, a snow manipulation experiment was conducted in December 2015 at the Spasskaya Pad experimental larch forest in Eastern Siberia, which is characterized by a continental dry climate with extreme cold winters and hot summers. Variables including soil temperature and moisture, oxygen and hydrogen isotope ratios of soil moisture and stem water, foliar nitrogen and carbon contents and their isotopes, phenology, and soil inorganic nitrogen were observed at snow removal (SNOW−), snow addition (SNOW+), and CONTROL plots. After snow manipulation, the soil temperature at the SNOW− plot decreased significantly compared to the CONTROL and SNOW+ plots. At SNOW− plot, snowmelt was earlier and soil temperature was higher than at other plots during spring because of low soil moisture caused by less snowmelt water. Despite the earlier snowmelt and higher soil temperature in the SNOW− plot in the early growing season, needle elongation was delayed. Leaf chemistry also differed between the CONTROL and SNOW− plots. The needle nitrogen content in the SNOW− plot was lower in the middle of July, whereas no difference was observed among the three plots in August. The soil inorganic nitrogen content of each plot corresponded to these results. The amount of soil ammonium was lower in the SNOW− plot than in the other plots at the end of July, however, once production started in August, the amount of soil ammonium in the three plots was comparable. Extremely low soil temperatures in winter and freeze–thaw cycles in spring and dry soil condition in spring and early summer at the SNOW− plot may have influenced the phenology and production of soil inorganic nitrogen.

LATE PLANTING SHORTENS THE FLOWERING PERIOD AND REDUCES FECUNDITY IN LASTHENIA CALIFORNICA

Modifications in the timing of life-history events can alter the biotic and abiotic environments experienced during an organism's lifetime. In plants, germination timing plays a critical role in relation to seasonal environmental conditions, pollinator availability, competitive dynamics, etc. Individuals can compensate for a change in timing of germination by modifying their growth and flowering time. However, biotic and abiotic factors may affect these compensatory responses. In this study we assess how biotic and abiotic differences due to planting date influence the timing of flowering, survival, and reproduction. To do this we manipulated germination timing of the annual California Goldfields (Lasthenia californica DC. ex Lindl., Asteraceae) in a serpentine grassland in northern California, by seeding three times during the growing season (November, January, and March). Neighbor removal plots were compared with control plots to examine influences of close neighbors and seasonal priority effects (due to early individuals pre-empting resources) on flowering time and duration, growth, and reproductive success (survival to reproduction and inflorescence production). Both planting date and neighbor removal treatments significantly impacted flowering time and duration, growth, and reproduction in this species. Later planting dates did delay flowering time, but this delay was minimal as flowering time was constrained within set biotic and abiotic boundaries. In addition, we find that a mixture of planting times and levels of neighbor removal can extend the duration of flowering on the landscape. Inflorescence production and survival declined with later planting dates, but neighbor removal counteracted this decline. We find that L. californica exhibits graded growth allocation, as well as plasticity in flowering time in response to planting date. This study has implications for the timing of restoration projects, as planting time influences both the timing of flowering as well as the overall reproductive success of planted individuals. Our results suggest that practitioners should aim to plant earlier in the season, but that neighbor removal may counteract some of the costs of late planting.

Understanding the Long-Term Impact of Bamboos on Secondary Forests: A Case for Bamboo Management in Southern Brazil

As secondary forests become more common around the world, it is essential to understand successional pathways to ensure their proper forest management. Despite optimism about secondary forests in terms of landscape restoration, the influence of invasive species on their development has been poorly explored. Here, forest plots in the Araucaria Forest, Southern Brazil, are used to compare forest dynamics over a 14-year period between unmanaged bamboo forest development (control) and the removal of bamboo. Six control plots (15 × 15 m) were monitored for all adult trees since 2007 alongside six adjacent removal plots; after the initial measurement of the control in 2007, all plots were measured bi-annually from 2010 to 2020. Comparisons were based on tree species diversity, composition, and structure parameters. Removal plots show a trend towards developing a forest composition with more secondary and late successional species while the control plots demonstrate succession restricted to the pioneer trees that regenerated immediately after bamboo die-off (2005–2006). Without the presence of bamboos, removal plots are mirroring the well-known successional pathway typical of the Araucaria Forest. Conversely, bamboos are effectively arresting successional development in the control, resulting in lower levels of diversity and less complex forest structure. For the first time, this study presents a direct analysis of the influence of bamboos on forest succession, providing evidence on which practices to manage bamboo forests can be developed so these secondary forests can fulfill their ecological and economic potential.