Forest Ecology and Management最新文献

Theoretical and empirical studies have suggested that climate, soils, and topography are the primary drivers of aboveground biomass in forests. Yet, the direct effects of these drivers may be mediated by indirect effects, such as species diversity and structural diversity. This study investigates the relationships between climate, topography, soil fertility, species diversity, structural diversity, and aboveground biomass (AGB) using Structural Equation Modeling (SEM) to distinguish indirect and direct causal relationships. We conducted this study in longleaf pine (Pinus palustris)-dominated forests in the southeastern United States (SEUS), using United States Department of Agriculture Forest Service inventory data from 2015 to 2019. The longleaf pine ecosystems of the SEUS are of great importance due to their rich biodiversity and unique ecological functions, but they also provide an opportunity for scientific studies across a large ecological gradient because they exist across a wide range of edaphic conditions. However, studies in longleaf pine have primarily focused on stand structure, regeneration processes, prescribed fire practices, and groundcover restoration, leaving a knowledge gap regarding AGB in this ecosystem. We hypothesized that (1) climate, topography, and soil fertility would influence AGB through positive indirect effects; (2) structural diversity rather than species diversity would strongly mediate the response of AGB to climate, topography, and soil fertility; and (3) species diversity and structural diversity would be positively correlated, with structural diversity positively impacting AGB across coarse scale ecological gradients. Structural diversity could be important in predicting AGB because it reflects the horizontal complexity of the forest stand. Our results show that mean annual temperature and slope had considerable direct negative and positive impacts on AGB, respectively. Additionally, soil fertility, elevation, and precipitation indirectly impacted AGB by affecting species diversity. Specifically, AGB decreased in highly fertile soils, whereas elevation and precipitation led to an increase in tree species diversity. Structural diversity had a direct positive influence on AGB, while species diversity played an indirect role by promoting structural diversity. While there are diverse objectives for managing longleaf pine, management that promotes high levels of stand structural diversity may strengthen the stock of longleaf pine forest AGB, which could be especially important in the face of changing climatic conditions. Our findings emphasize the importance of integrating climate resilience and carbon storage goals into forest management practices.

Cacao is the most important agricultural product in the southern region of Bahia state, Brazil, with 70 % of its production occurring under the traditional agroforestry where cacao is mostly shaded by native trees. This traditional system allows to reconcile the production with the maintenance of the portion of original biodiversity. However, increased deforestation and intensified agroforestry management aimed at boosting productivity may impact the diversity of native species and the services they provide. In this context, our aim was to disentangle the role of landscape forest cover and the local vegetation complexity on predation of caterpillars and herbivory of cacao plants located in agroforestry systems. The study was conducted across 18 cacao agroforest sites in southern Bahia located in landscapes with different amounts of forest cover. We assessed predation rate using dummy caterpillars, sampling understory birds and arthropods and collected leaves of cacao trees to analyze damage by herbivory. We also measured shading levels and the abundance of cacao trees in each agroforestry. Predation pressure on dummy caterpillars was positively influenced by the abundance of total predators and the level of landscape forest cover and negatively by the number of cacao trees. Even so, we found no evidence that landscape, local features or the actual invertebrate assemblages (predators or herbivores) influenced the cacao leaf damage. The findings highlight the multifaceted interactions between ecological factors, predation pressure, and leaf damage within cacao agroforestry systems.

Addition of nitrogen (N) to forest soil may alter wood decay rates and fungal community structure and richness. In a northern Sweden Pinus sylvestris L. forest, two levels of ammonium nitrate were applied annually from 1971 to 2008. In 2007 we initiated an investigation into wood decay (assessed through mass loss) and fungal responses using stakes of trembling aspen (Populus tremuloides Michx.) and loblolly pine (Pinus taeda L.) wood installed at different soil depths in plots where zero (N0), low (34 kg; N1), or high (68 kg; N2) levels of N were applied. Stakes were located either horizontally on the surface of the organic horizon, at the interface between the mineral and organic horizons, or vertically in the mineral soil. For litter and mineral soil, fertilizer treatment was not significant for any soil chemical or physical property. Overall, pine and aspen wood stake mass loss was less than 35 % three years after deployment. Notably, the N1 treatment had the most pronounced effect on wood decay, and significantly accelerated aspen decomposition at the organic horizon surface in the second and third years. Analysis of fungal DNA extracted from the wood stakes revealed fluctuations in fungal richness and community composition depending upon stake location and duration since deployment. Fungal richness was notably higher in surface aspen stakes under N0 and N1 treatments and in surface pine stakes under N0 in the second year, though richness generally decreased with time as stake decay increased. Fungal community composition also varied by stake location and time since deployment. These results indicate that prolonged N addition can affect fungal richness, which may in turn affect wood decomposition rates. Further research is needed to clarify the nature and persistence of long-term soil N-addition effects on organic matter decomposition and soil microbial communities.

Fire disturbances and atmospheric nitrogen (N) deposition can significantly soil nutrient dynamics and plant nutrient uptake, thereby influencing on biogeochemical cycles within forest ecosystems. Despite these known effects, the combined impact of burning and N addition on leaf nutrient characteristics and the underlying mechanisms remains largely unexplored, particularly within forest ecosystems. This study presents a three-year field experiment designed to assess the responses of leaf N and phosphorus (P) concentrations, N:P ratios, and nutrient resorption in six dominant species (comprising two tree species and four understory species) to burning and N addition in a coniferous-broadleaved mixed forest located within a subtropical-warm temperate transition zone in Central China. The findings revealed that burning did not affect N concentrations in either green or senesced leaves, nor did it influence N or P resorption across any of the tree or shrub species. However, it did increase P concentrations in green leaves and reduce N:P ratios in shrub species. N addition elevated the N concentrations and N:P ratio in green and/or senesced leaves (with the exception of Quercus acutissima Carruth.), without affecting N or P resorption. These results suggest that shrubs enhanced P uptake due to increased soil P availability but maintain consistent internal P cycling (i.e., nutrient resorption) following low-severity fires. Additionally, most shrub species exhibited lower N:P ratios compared to tree species post-burning, indicating distinct nutrient requirements and fire responses based on life form. This study provides essential insights, demonstrating that burning mitigates P limitation on plant growth in subtropical–warm temperate ecotonal forests. Furthermore, the differential responses of leaf nutrient traits and associated stoichiometry across diverse life forms to environmental disturbances may influence plant diversity and community composition within these forests.

Laminated Root Rot caused by the fungal pathogen Coniferiporia sulphurascens is a damaging disease within many Douglas-fir forests of the Pacific Northwest of North America. Management of these forests in a changing climate and fire regime will require changes to silvicultural practices. A long-term study (ca. 30 years) in Oregon, USA provides an opportunity to investigate the effects of thinning on disease dynamics in an area of historically high laminated root rot incidence. The effects of three thinning prescriptions on tree mortality caused by C. sulphurascens were compared on ca. 160 ha within the Siuslaw National Forest. Observations were compared with predictions from the Forest Vegetation Simulator and its Western Root Disease Model extension. No significant effect of thinning treatment on mortality (p = 0.981), or annual basal area increment (p = 0.372) was observed. In contrast to observations, the Forest Vegetation Simulator over estimated growth, while the Western Root Disease Model extension was consistent with field measurements. Thinning treatments appear to have minimal impacts on laminated root rot induced mortality but also do not result in the expected increase in growth rate typically associated with a thinning treatment.

Climate change-related extreme drought events already have a significant impact on the productivity and mortality of Central European forests. European beech (Fagus sylvatica ssp. sylvatica), one of the most important European broadleaved species, has responded to such drought periods with increasing mortality and reduced volume increment. This has raised concerns about its suitability and adaptive capacity in relation to future climatic conditions and motivated the search for alternative tree species that are suitable for assisted migration into European beech forests. One of the candidates is the Oriental beech species complex (F. sylvatica ssp. orientalis), whose range extends from the Balkan to Iran and, at least in some parts of its range, grows under a warmer and drier climate. In order to evaluate whether Oriental beech is more drought tolerant, we compared the radial growth response to droughts between 1920 and 2018 of a total of 138 European and 122 Oriental beeches growing under identical site conditions in eight different locations in Germany and France. The species identity of all analysed trees was verified by microsatellite analyses, and the origin of the introduced Oriental beech was traced to the Greater Caucasus (7 stands) and the Black Sea coast (1 stand). The drought responses of radial growth were quantified using the indices resistance, resilience, and recovery as suggested by Lloret et al. (2011) and growth recovery time (GRT) (Thurm et al., 2016) and used as response variables in generalized linear mixed effect models.

Considering only the average radial growth response to severe and extreme drought events, both the different Lloret indices and the GRT did not show prominent difference between Oriental and European beech. However, the mixed model analyses, which also included interaction terms, revealed interspecific differences in drought tolerance, depending on the intensity and timing of the drought. In extreme summer drought years, values of resistance predicted by the mixed-effect models were significantly higher in Oriental beech than in European beech, whereas its resilience was only slightly better than in European beech, regardless of drought intensities. In contrast, Oriental beech was much more susceptible to spring drought with significantly weaker growth recovery and distinctly longer growth recovery times.

Based on these results, Oriental beech provenances from the Caucasus do not appear to be sufficiently more drought tolerant than European beech to justify an assisted migration approach to adapt Central European forests to climate change. To analyse the drought tolerance of Oriental beech more comprehensively, introduced trees representing other genetic clusters need to be analysed, as well as the effects of repeated drought events on growth and mortality.

Numerous factors influence the frequency and intensity of forest fires. Forest fire damage and recovery are influenced by the species composition of the forests. This study assessed forest fire damage vulnerability and forest fire resistance according to the species composition of the forest stand (i.e., the proportion of needle leaf trees (NTs) versus broadleaved trees (BTs) within the forest stand). Following a forest fire event in South Korea, fire damage severity was determined by comparing the pre- and post-event normalized burn ratio obtained from Sentinel-2 imagery. In addition, using 3 m PlanetScope images, we were able to quantify (1) the species composition between NTs and BTs within 30 m of Sentinel-2 pixels and (2) the extent of fire damage and recovery based on changes in phenological timing events and the vegetation index. The results showed that the NT-dominated forest stands underwent more fire damage than the BT-dominated stands, and the differences increased with increasing fire severity. In NT-dominated forest stands, an increase in BT proportion led to a decrease in fire damage, whereas in BT-dominated forest stands, no such correlations were observed. Furthermore, the NT-dominated stands showed more delayed phenological events at the beginning and end of the growing season than the BT-dominated stands, implying slow post-fire recovery in the NT-dominated stands. Our results showed differences in fire damage vulnerability and recovery depending on species composition and demonstrated that the increased fire resistance of BT could improve the fire resistance of a forest stand. These results suggest that considering tree species biodiversity is critical for restoring fire-damaged areas, particularly in the context of climate change, where wildfire frequency is expected to increase.

Nutrient limitation of forest growth, especially nitrogen (N) deficiency, is widespread in the boreal region. N fertilisation has thus become a common silvicultural practice in Fennoscandian Norway spruce stands, but to what extent phosphorus (P) is co-limiting productivity and how initial basal area affects the growth response to N addition remains unresolved. To address these questions, two experiments were established in mid-rotation Norway spruce stands in southern Sweden where decades of high atmospheric N deposition have reduced the severity of N-limitation. In a P experiment initiated in 2011, we tested P addition alone (two applications of 200 kg P ha⁻¹) and in a second study also starting in 2011 (NP experiment), a single dose of N was administered alone (200 kg ha⁻¹ in thinned and unthinned stands, hereafter called N and N-unthinned treatments) and in combination with P (N+P = one-time 200 kg N ha⁻¹, two applications of 200 kg P ha⁻¹ in thinned stands). P addition alone increased PAI (periodic annual increment) significantly by 21 % during the first, moister assessment period up to 2014 and by 18 % in the drier 2015–2019 period, resulting in a 10 % increase in final stem volume yield. In the NP experiment, significant PAI increases under favourable meteorological conditions up to 2014 occurred in all fertilisation treatments. The strongest effects were seen in the N-unthinned treatment while no significant additive effect resulted from the joint addition of N and P (N: +20 %, N-unthinned: +38 %, N+P: +23 %). In the drier 2015–2019 period, only the N+P treatment caused significantly greater PAI (+29 %). Final stem volume yield in the NP experiment significantly increased by 10 %, 39 % and 16 % in the N, N-unthinned and N+P plots, respectively. In both experiments, foliar P and thus P/N rose drastically in response to P addition alone or in combination with N. Minor increases in leaf area index (LAI) only occurred in P-containing treatments. Our findings indicate that Norway spruce productivity in southern Sweden is constrained to a similar extent by both N and P. Sustainable nutrient management in Norway spruce growing regions with high N loading (like southern Sweden) should prioritise P over N supply.

In response to the combined impacts of the climate and biodiversity crises, as well as for timber security and increased recreational access to green spaces, there is a global drive to increase tree cover. In the UK, an estimated 1.5 million ha of afforestation are required to meet its carbon net-zero emissions targets (Committee on Climate Change, 2018). Despite the potential benefits, careful consideration must be given to the impacts of woodland creation on species adapted to open habitats. To investigate potential risks and mitigation for the IUCN Near Threatened Eurasian curlew Numenius arquata, a national spatially extensive field-scale dataset was used to investigate the relationships between curlew presence during the breeding season and a range of forest and landscape variables at two different spatial scales (0.5 km and 1 km). Variables included forest extent and configuration, and interaction between forests and extent of semi-natural open habitats, moorland management and topography. At both spatial scales, a negative relationship existed between extent of forest and the probability of curlew presence, and at 1 km, between probability of presence and the number of forest patches. However, these negative patterns depended on landscape context and were reduced where there was a greater quantity of semi-natural open habitat, such as moorland or rough grassland, and moorland management present. Overall, the findings emphasise the need to consider the impacts of woodland creation projects on species adapted to open habitats. However, the results suggest that these impacts can be influenced by landscape. These results could help inform decisions regarding the appropriateness of woodland creation in different landscapes and possible mitigation measures that could be applied against the risks created by afforestation.