查看更多>>摘要：Chronic anthropogenic disturbances and climate change are the main threats to biodiversity, acting as potential drivers of assembly reorganization in human-modified tropical landscapes. We aimed to understand how the reproductive traits of edible fruit plant assemblages respond to chronic disturbances and aridity in the Caatinga, a dry forest in northeastern Brazil housing a human population that greatly depends on natural resources for subsistence and is threatened by increasing aridity. The study was carried out across 20 permanent plots of Caatinga, covering gradients of chronic disturbances (livestock grazing, wood extraction and non-timber product exploitation) and aridity (1051 mm to 664 mm). We registered 24 native plant species with fruits that are edible for humans, which were classified according to their flowering/fruiting pattern, floral size and reward, sexual and reproductive systems, pollination systems, and fruit types. They were also grouped into two categories of reproductive strategies (generalists and specialists). We documented that chronic disturbances and aridity pose more negative than positive effects on the reproductive traits of edible fruit plants in terms of trait richness (negative: 29% of the traits; positive: 3.2%) and abundance (negative: 19.3%; positive: 3.2%). In general, we observed that 79.2% of the studied species had at least one reproductive trait that was negatively reduced by increased chronic disturbance and/or aridity in terms of trait richness and abundance. Overall, 75% of the edible fruit species have specialized reproductive strategies that were negatively affected by chronic disturbances and/ or aridity. Specifically, individual or combined effects of chronic anthropogenic disturbances or aridity nega-tively impacted the richness and abundance of specialized reproductive traits such as supra-annual flowering and fruiting patterns and obligatory cross-pollinated edible fruit species. Also, in terms of richness, the reproductive functional diversity of specialized reproductive strategies was negatively affected by increasing aridity. Our findings indicate that in the expected future scenarios of increased land-use and climate change, the Caatinga could face a collapse in the offer of edible fruits to local human communities by impacting the provision of this ecosystem service.
Caduff, Marion E.Brozova, NatalieKupferschmid, Andrea D.Krumm, Frank...
13页
查看更多>>摘要：Large-scale bark beetle outbreaks in spruce dominated mountain forests have increased in recent decades, and this trend is expected to continue in the future. These outbreaks have immediate and major effects on forest structure and ecosystem services. However, it remains unclear how forests recover from bark beetle infestations over the long term, and how different recovery stages fulfil the capacity of forests to protect infrastructures and human lives from natural hazards.The aim of this study was to investigate how a bark beetle infestation (1992-1997) in a spruce dominated forest in the Swiss Alps changed the forest structure and its protective function against snow avalanches. In 2020, i.e. 27 years after the peak of the outbreak, we re-surveyed the composition and height of new trees, as well as the deadwood height and degree of decay in an area that had been surveyed 20 years earlier. With the help of remote sensing data and avalanche simulations, we assessed the protective effect against avalanches before the disturbances (in 1985) and in 1997, 2007, 2014 and 2019 for a frequent (30-year return period) and an extreme (300-year return period) avalanche scenario. Post-disturbance regeneration led to a young forest that was again dominated by spruce 27 years after the outbreak, with median tree heights of 3-4 m and a crown cover of 10-30%.Deadwood covered 20-25% of the forest floor and was mainly in decay stages two and three out of five. Snags had median heights of 1.4 m, leaning logs 0.5 m and lying logs 0.3 m. The protective effect of the forest was high before the bark beetle outbreak and decreased during the first years of infestation (until 1997), mainly in the case of extreme avalanche events. The protective capacity reached an overall minimum in 2007 as a result of many forest openings. It partially recovered by 2014 and further increased by 2019, thanks to forest regeneration. Simulation results and a lack of avalanche releases since the infestation indicate that the protective capacity of post-disturbance forest stands affected by bark beetle may often be underestimated.
查看更多>>摘要：Endemic plant pathogens are important agents of many forest processes and contribute to shaping forest ecosystem dynamics and diversity. However, Marssonina leaf spot of poplar is induced by a pathogenic fungus Drepanopeziza populi, causing increased damage to riparian poplars in recent years. And such endemic diseases have received little attention at the landscape scale, despite the key role of landscape features in the development and spread of certain emerging diseases. Moreover, few studies have sufficiently captured multiple ecological factors driving the infestation of an endemic pathogen acting at the landscape, stand, and individual scales. Here, we measured pathogen load, disease prevalence, and disease severity of Marssonina leaf spot in bitter poplars (Populus laurifolia) in riparian forests, and explored the direct and indirect effects of multiple ecological factors on pathogen infestation using structural equation models. Specifically, we first assessed the effects of landscape and stand-scale factors on leaf traits including leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC), and then examined the role of these factors in shaping disease dynamics. We found that forest cover had no direct impact on host leaf traits and pathogen infestation, but directly affected stand characteristics, with higher forest cover in a landscape increasing host density and tree diversity. Host density was the most important factor of pathogen load, with a higher density of host poplars resulting in greater symptomatic leaf count. Tree diversity had direct effects on disease prevalence, with host poplars growing in mixed forest stands far less infected by pathogens than in pure stands. Disease prevalence was also positively related to pathogen load. Moreover, tree diversity strongly reduced SLA but increased LDMC. Leaves with higher SLA was found to increase pathogen load and disease severity, but leaves with higher LDMC was found to reduce them. Our results show that landscape-scale forest cover indirectly affects Marssonina leaf spot dynamics via stand characteristics and leaf traits. Disentangling the effects of biotic and abiotic factors on pathogen infestation can provide crucial insights into multi-scale ecological factors in driving plant disease expression, and contribute to reducing the overall impact of endemic forest diseases.
查看更多>>摘要：The cultivation of Populus spp. on acid soils is difficult mainly due to low nutrient availability, limiting the distribution and use of this marketable tree species. In this paper we report the results of two experiments, in which a granulated highly reactive micronized calcium carbonate (CaCO3) was tested at increasing levels to improve the effect of NPKS fertilization on poplar growth. Twin field and pot experiments were carried out in 2017 using two different poplar clones, both of which are often used in Italy. In addition to analysing the data from the two experiments separately, common patterns were evaluated using a mixed-effect model with CaCO3 level and fertilization as fixed effects, and the experiment type as random effect. Growth was assessed in terms of total height, diameter and biomass. Taken together, the results from the two experiments showed that fertilization led to enhanced growth of poplar, but this effect was stronger when soil conditions in terms of pH and exchangeable Ca were at a sufficiently high level. Available nutrient concentrations in the soil and foliar nutrient concentrations in the plant suggested co-limitation of poplar growth by N and Ca. In conclusion, the results of this study on one hand emphasize the importance of adapting the level of CaCO3 to the given soil conditions, and on the other hand ask for further studies addressing the relative importance of elevated pH and improved Ca nutrition.
Patricio, Maria SameiroDias, Cremildo R. G.Nunes, Luis
10页
查看更多>>摘要：Height is a key variable for forest management. However, tree height measurements are expensive and timeconsuming, requiring more effort to measure in the forest than diameter breast height measurements. Indeed, height-diameter (h-d) models are increasingly used to overcome the difficulty in measuring tree heights. Therefore, more accurate h-d models are increasingly needed. The mixed-effects modeling approach is a mainstream method to estimate h-d models. This technique was used to model the h-d relationship in the first 24 years of growth of sweet chestnut (Castanea sativa Mill.) high-forest stands for timber production. A dataset of 10,868 h-d observations and 57 plots of local-inventory data were considered individually. Simple mixed-effects models considering a grouping structure in the data (plot-level) were obtained, and generalized mixed-effects models were developed by expanding the fixed structure of simple mixed-effects models with stand-level variables. Several alternative model forms were tested in terms of accuracy, applicability and measurement effort. Different alternatives for calibrated predictions of tree height at plot level were analyzed, and considerations on the tradeoff between easy-to-use equations in the field practice and high-accuracy equations for forest inventory were tested. The selected Richards M1a generalized mixed-effects model simultaneously provides fixed and random parameters to estimate the chestnut tree height from tree diameter and stand-level variables using the same model. The analysis showed that the inclusion of dominant height and dominant diameter as predictors improved the accuracy of the Richards model. The Draudt method was one of the best approaches to improve tree-level height prediction accuracy using mixed-effects. The applied approach is quite feasible in 100-500 m(2 )plots. The use of these models and the suggested calibration process will significantly reduce the effort and costs of fieldwork teams to measure heights for forest management planning while ensuring high accuracy. This effort is greater the greater the forest density and, therefore, greater for young stands than for adult stands.
Lobo, AlbinFind, Jens IverHansen, Jon KehletREbild, Anders...
7页
查看更多>>摘要：Epigenetic modification induced during embryogenesis can serve as a mechanism for rapid adaptation of plants to climate change, especially for long living organisms such as trees. Here, we test if temperature and osmotic stress during embryogenesis influences spring and autumn phenology, photosynthesis rate, growth and water stress tolerance in Abies nordmanniana. Somatic embryogenic plants (emblings) were developed under different temperatures to test if temperature influences the spring phenology. Our results show that 9 ? higher temperature during somatic embryogenesis advanced budburst by an average of 4 days, but with significant differences among different genotypes in their response. This reveals genetic variation in the observed phenological response to temperature during somatic embryogenesis. However, we did not observe an effect of differences in osmotic stress during somatic embryogenesis on the response of the emblings to water stress. Optimum temperatures for photosynthesis and maximal photosynthetic rates were not found to be influenced by the temperature during somatic embryogenesis. Both height and autumn senescence were significantly different among the genotypes, but the temperature during somatic embryogenesis did not affect these traits. The observed responses in our study complement findings from other species and support that epigenetic modification in phenology may help the species to cope with fluctuations in temperatures in future climate, and may have practical applications for reducing spring frost risk in plantations of the species.
NSTL
Elsevier