查看更多>>摘要：Successful invasions of non-native plants often depend on establishing mutualistic interactions with native organisms. Animal seed dispersers can greatly enhance the spread of invasive plants. Emerging seed dispersal mutualisms might also result in indirect interactions between non-native and native plants, mediated by shared dispersal agents. We investigated tripartite interactions between Eurasian jays (Garrulus glandarius), non-native northern red oaks (Quercus rubra), and native pedunculate oaks (Q. robur) in a lowland forest of Central Europe. We estimated the probability of acorn removal for both oak species in single vs. mixed treatment, and the effects of acorn length, width, and weight. We also radio-tracked removed acorns to determine their fate. While jays preferred to harvest the native acorns, they also removed almost all offered acorns of the invader. The removal rate of non-native acorns increased when the two oak species co-occurred, and was modulated by acorn traits: jays selected red oak acorns that were long and narrow. In comparison to pedunculate oak acorns, those of red oak were transported shorter distances and were more likely to be consumed rather than cached. Altogether, dispersal of red oaks by jays was less intense and brought smaller benefits relatively to the dispersal of pedunculate oak. Yet, these differences were moderate, and jays provided effective dispersal of both oaks. Our results highlight the role of keystone native seed dispersers in the expansion of non-native plants. Furthermore, they illustrate how dispersal quantity of non-native plants can be facilitated by the presence of native plants that attract shared seed dispersers.
Bigelow, Seth W.Hiers, J. KevinJack, Steven B.Cannon, Jeffery B....
13页
查看更多>>摘要：Natural disturbance-based silviculture emphasizes harvest methods that emulate the timing and structural changes of natural disturbances. Longleaf pine woodlands are ecologically important ecosystems of the southeastern U.S. that support high biodiversity. Options for multi-aged silviculture include individual tree and group selection methods to promote regeneration-the latter method may be modified by retention of reserve trees. To explore the extent to which selection methods are congruent with natural disturbance regimes, we evaluated how treatments in mature second-growth longleaf pine woodlands affected overstory structure, pattern, and dynamics, and we made comparisons to an old-growth longleaf stand. In 2010, stands were harvested using individual tree selection, group selection, or group selection with reserves. We compared treatment effects on spatial pattern of residual trees, recruitment of trees into the 10 cm diameter class (hereafter "recruitment"), and tree mortality 8 years after harvest. Basal area and residual volume were similar among treatments, but the individual tree selection treatment had lower density and a unimodal rather than bimodal diameter distribution compared to other treatments. Group selection and group selection with reserves increased spatial aggregation, compared to individual tree selection which reduced aggregation. Recruitment was similar across treatments but usually occurred near existing trees in the group selection treatments and was further from existing trees in the individual tree selection treatment. Tree mortality primarily occurred as single trees rather than tree groups for all treatments. These results indicate that natural disturbance-based treatments vary in their effects on overstory spatial pattern and alter forest dynamics. In longleaf pine woodlands, the rationale for individual tree selection emphasizes maintaining a continuous input of needles as fine fuels for control of resprouting hardwoods with prescribed fire. This method, may simplify overstory spatial structure and alter forest dynamics after initial harvest. Maintenance of vertical and horizontal complexity is a central tenet of natural disturbance-based management, thus attention to spatial pattern must be given when individual tree selection methods are used. In longleaf pine woodlands, natural disturbance-based techniques such as group selection with reserves may better mimic spatial patterns seen in old-growth stands while preserving continuity of fine fuels.
查看更多>>摘要：Forestation is a key strategy to mitigate climate change caused by anthropogenic carbon dioxide emissions. However, the impacts of forestation on soil pH remain unclear, despite critical roles of soil pH in regulating key soil biogeochemical processes. Here, we collected a global dataset of soil pH change after forestation, which included 1082 observations from 171 published papers. Results showed that soil pH declined significantly by 0.23 after forestation over the globe. Soil pH consistently declined after forestation, no matter the forest was established naturally or by planting, on croplands or grasslands. The decline of pH after forestation was generally larger in neutral soils (pH 6-7) than in acidic soils (pH < 6) and alkaline soils (pH > 7), and larger in boreal and temperate forests than in tropical forests. Soil pH decreased significantly in humid areas but not in arid regions. Random forest analysis showed that climate was the most important regulatory factor to influence soil pH change after forestation. Mean annual temperature and precipitation probably affected soil pH both directly and indirectly via altering soil physiochemical properties. Given vital roles of soil pH in regulating carbon and nutrient dynamics, our findings have important implications for the long-term impacts of forestation on carbon and nutrient dynamics.
Chaves, Jimena E.Lencinas, Maria, VCellini, Juan M.Peri, Pablo L....
12页
查看更多>>摘要：Estimation of biomass and nutrient contents in tree components are essential for evaluating the impact of harvesting on carbon fixation capacity, bio-element recycling, and long-term effect on the balance that influence over net primary productivity. In many reports, fixed values were roughly considered at tree and stand level; however, the nutrient contents can vary across natural gradients (e.g. site quality and crown class) and according tree components (e.g. leaves, branches, bark, wood); and also, can be related to their fibre contents. The objective was to determine these changes in one tree species (Nothofagus pumilio) growing in Southern Patagonia (Argentina), comparing carbon (C), nitrogen (N) and fibre tissue contents of above-ground biomass across site quality and crown class gradients. We found that C, N and fibre (cellulose, hemicellulose, lignin) at different tree compartments varied with the site quality and crown class gradients (dominant, codominant, intermediate, suppressed). High tree growth rate (better site qualities and dominant trees) affected tissue density and fibre content by increasing C content (e.g. lignin generated higher carbon content). Also, we found the same trend for N content, which was more evidently related to some tissues (e.g. leaves). The use of fixed values in the modelling for tree or stand approaches in C or N estimations can generate significant biases in N. pumilio trees, being necessary consider specific values for the different natural gradients that influence over this tree growth species. Calculating accurately the stored and sequestered C or N contents can improve management strategies and modelling of the natural forest stands. The information provided in the present study suggests the need of incorporate the natural gradients into the tree models for C sequestration and N storage estimations.
查看更多>>摘要：The safety of genetically modified forest trees is an important ecological issue worldwide, and concerns about genetic modification are one factor hindering in-depth research and large-scale planting of genetically modified trees. This study evaluated the impact of transgenic poplars on the ecosystem by analyzing differences in arthropod communities, target arthropods, and nontarget arthropods in transgenic (BtCryIAc) and non-transgenic experimental forests of Populus x euramericana cv. "74/76" (hereafter, tPE and ntPE, respectively). Five years of dynamic monitoring showed that the tPE had stable and lasting insect resistance to Lepidoptera, especially Arctiidae. However, the insertion of exogenous genes also had a negative impact on certain tPE line. The principle response curves (PRC) indicated that the genetic modification contributed much less to the community difference than the year factor (7% vs. 60%, respectively), and nontarget arthropods may be more sensitive to interannual variations. Nontarget arthropods that respond sharply to the PRC curve include Aphididae and Tenthredinidae (species weight > 0.5), but this difference appears only in certain years or lines. Our research shows that the tPE had no obvious adverse effects on nontarget arthropods. In areas with severe lepidopteran pests, the tPE could help to increase the diversity and stability of arthropod communities, while providing greater ecological and economic benefits than non-transgenic poplars.
查看更多>>摘要：Catastrophic wind disturbance affects not only forest structure and regeneration, but also functional and compositional dynamics of the herbaceous layer. However, the issue of changes in functional diversity and functional trait values of the understory layer in response to wind disturbance has not been addressed so far. This study aims at investigating the patterns of variations in functional diversity, trait values and species richness of herbaceous species following wind disturbance. The study was carried out in the Piska Forest, a woodland complex in northern Poland, which was almost completely destroyed by a windstorm in 2002 and part of which was successively set aside to study the effects of natural disturbance on forest ecosystems. Vegetation surveys were conducted at 112 sample plots between 2014 and 2015. Four forest habitat types were identified and individually examined. The degree of disturbance severity was assessed as percentage of dead trees on all trees per surface unit. A set of twelve functional traits was assigned to the recorded species. Three functional diversity metrics (richness, evenness and divergence) were calculated based on the selected functional traits. We assessed the relationship between each of such metric and disturbance severity for each habitat type. The relationship between species richness and disturbance severity was also determined. We then estimated the relative importance of habitat type and disturbance severity on both functional diversity and species richness. Lastly, we examined the response of functional trait values to both disturbance severity and habitat type. Our results showed that wind disturbance effects on functional diversity are not univocal and that they strongly depend on habitat type. In fact, while in coniferous stands disturbance determined a decrease of functional divergence and left functional richness unaltered, in mixed-coniferous habitats it enhanced functional richness and did not affect functional divergence. In mixed-deciduous habitats, both functional richness and divergence decreased. In swamp habitats no major changes in functional diversity were observed. Changes in functional evenness were not significant. At the same time, disturbance significantly enhanced species richness in all forest habitats, but the coniferous one. It was not possible to clearly disentangle the relative contribution of disturbance and habitat type, since the two are strictly correlated. Out of the tested functional traits, only SLA, seed releasing height and share of stress-tolerant species exhibited significant response along the tested disturbance gradient. Most of the other traits reacted only to variations in the habitat type.
Casado, Monica RivasBellamy, PatriciaLeinster, PaulBurgess, Paul J....
7页
查看更多>>摘要：This study investigates changes in soil carbon under woodland combining data from the National Soil Inventory of England and Wales with data from the National Inventory of Woodlands and Trees to create a unique dataset with woodland management information at the sites where soil carbon was measured in 1980 and 2003. Three woodland management stages were compared: first rotation (i.e. recently planted on land not previously under woodland and not yet harvested), second rotation (i.e. harvested at least once), and historic woodlands. Woodlands in their first rotation demonstrated a reduction (p 0.01) in topsoil organic carbon content typically losing over 2% per year, whereas no change (p 0.10) was observed for the other two woodland types. This large reduction in organic carbon could not be statistically explained by a higher inherent soil carbon, as the mean soil carbon content of the first rotation and second rotation woodlands were not (p > 0.50) different. The average age of the woodlands under first rotation was 42 years, indicating that the period of significant soil carbon loss could go on for about 40 years after planting.
查看更多>>摘要：Moso bamboo (Phyllostachys edulis) forests are widely distributed in southern China and have expanded rapidly in recent years. Although some studies have explored bamboo biomass, there are great uncertainties regarding regional-and national-scale estimations of the total biomass of bamboo forests due to a lack of systematic surveys and root biomass sampling. We investigated 322 bamboo stand plots at 48 sites across all distributed areas (15 provinces) in China in 2017-2019. We further measured the biomass of 147 individual shoots and 132 whole plants in Jiangxi Province, and determined the above-and belowground biomass in 11 sample plots using the complete harvesting method. At individual-level, the average biomass of whole-bamboo and shoot were estimated as 15.6 +/- 8.3 and 12.8 +/- 6.9 kg per individual, respectively. The stand mean aboveground and below ground biomass values were 60.3 +/- 25.7 and 21.0 +/- 5.6 Mg ha(-1), with a total stand biomass of 81.4 +/- 31.3 Mg ha(-1) and an average root-to-shoot ratio of 0.37 +/- 0.07. Using these data, combined with the 9th National Forest Inventory (NFI) dataset, we estimated that the total bamboo biomass of China was 283.0 +/- 6.0 Teragrams (Tg) by using individual mean biomass and 349.5 +/- 8.3 Tg by using stand mean biomass, which accounted for 1.7-2.1% of the national total forest biomass carbon pool (i.e., 8.5 Pg C). Our results provide an accurate estimation of bamboo forest biomass based on direct field measurements, and these estimates are essential to the parameterization of forest carbon models in China.
查看更多>>摘要：Forest management is one of the important nature-based solutions for climate mitigation. Thinning can indirectly influence tree physiology by changing the microclimate and directly change the stand biomass, which can impact forest carbon sequestration. However, previous results about how thinning might influence carbon stocks remain inconsistent regarding post-thinning carbon accretion. In this study, crop tree release (CTR) thinning in four intensities (CK: 0% of basal area removal, LT: 17.25%, MT: 34.73%, and HT: 51.87%) were conducted in a temperate deciduous forest in Jiaohe, northeastern China in 2011. Plot inventories in 2011, 2013, 2015, 2018 and 2021 and tree cores collected in 2017 and 2018 offered the opportunity to examine how are the interannual carbon sequestration ability of Korean pine and Manchurian ash responded to CTR thinning in four intensities. We quantify the carbon sequestration ability of trees by calculating individual stem carbon stock and annual carbon stock rate to examine whether the previous inconsistency was attributed to different responses of species, and the ignorance of frozen carbon content. The results show: (1) after thinning, the underestimation of carbon stocks of Manchurian ash decreased with the increasing thinning intensity. The greatest underestimation of Manchurian ash reaches 2922 kg ha-1, while that of Korean pine only reaches 283 kg ha-1. Compared with Manchurian ash, the conventional carbon fraction of 0.5 for Korean pine is more appropriate, and the misestimation of Korean pine didn't show an obvious pattern with the intensity of thinning. (2) Under light thinning, both species maintained a stable carbon stock growth, and the frozen carbon content of Korean pine was significantly increased. During the 10 years after light thinning, the individual stem carbon of Korean pine increased from 57 kg to 81 kg, and Manchurian ash increased from 201 kg to 268 kg. The average rate of increase of individual stem carbon is positively related to tree size. Removing such large-diameter trees from the stand is likely to decrease carbon stock rate. Therefore, it is essential to design carbon-friendly silviculture prescriptions worldwide under the consideration of species, sizes, and intensities.
Fairman, Thomas A.Nitschke, Craig R.Bennett, Lauren T.
13页
查看更多>>摘要：Forests play a key role in mitigating global climate change through carbon storage and sequestration. Wildfire affects forest carbon through combustion and by influencing forest mortality and regrowth, which are also influenced by a forest's growth environment. Wildfires are becoming more severe and frequent in many temperate regions but the impacts of such changes-in association with projected warmer, drier climates-on forest carbon stocks, remains under-quantified in many temperate biomes. We compare the impacts of a single high-severity wildfire and two high-severity wildfires within a short interval (six years) on carbon stocks 2-3 years after the last wildfire in multiple carbon pools of fire-tolerant eucalypt forests in temperate, south-eastern Australia. These forests are assumed to contain relatively resistant carbon stores because the dominant eucalypts are rarely killed by fire, reliably resprouting after most fires. Mean carbon stocks in the principal aboveground pools were decreased by one, and particularly two, high-severity wildfires after controlling for site aridity, which was negatively related to aboveground carbon stocks. On average, the percentage of aboveground carbon stocks in live biomass decreased from 76% at Unburned sites to 62% at Single-burned and 47% at Double-burned sites, contributing to increases in standing deadwood carbon stocks from 11% at Unburned sites to 42% at Double burned sites. As such, the proportion of carbon in large, living trees (an indicator of carbon stability and carbon-recovery capacity) was decreased after short-interval wildfires. Soil carbon stocks to 10-cm depth were also significantly reduced at all wildfire sites (likely due to erosion), which could also delay post-fire recovery of productivity. Overall, our findings indicate that both single and short-interval wildfires can significantly reduce the amount of carbon stored in fire-tolerant eucalypt forests, and that the potential for carbon-stock recovery could be compromised by predicted warmer and drier (i.e., more arid) future climates, and by soil feedbacks to productivity. Actively managing carbon stocks in fire-tolerant eucalypt forests could be required in the coming decades to mitigate these risks.
NSTL
Elsevier