Forest Ecology and Management最新文献

Species that arrive first influence community assembly. This “priority effect” has been extensively applied in ecological restoration through the removal of invasive plants and subsequent introduction of native species, assuming that recolonization by invaders will be hindered by introduced natives. Nonetheless, often the target community is very prone to reinvasion, which might be partially due to poor early growth of natives. This study examines this phenomenon and potential underlying mechanisms in a woodland restoration area in southwestern Australia, considering both, the response and effect of sown native species in relation to a nonnative community re-emerging relatively late due to its initial removal. We aimed to elucidate the effects of a range of factors including phylogenetic relatedness of the seed mixes to annual grasses on nonnative community, seed mass, soil moisture and other soil variables linked to it. We sowed three natives seed mixes in an old field following removal of the nonnative annual grass community broadly dominated by annual grasses. We examined the direction and intensity of the interaction between these and the nonnative community. The seed mixes included (1) monocultures of the native grass Rytidosperma caespitosa, (2) monocultures of six woody species and (3) cultures mixing the native grass with each woody species. Overall, nonnative species dominated by annual grasses emerging late did not affect woody natives but suppressed native grass Rytidosperma, both as a monoculture and mixed with woody species. When growing alongside late nonnatives, the survival of woody natives was favored by woody species seed mass and soil moisture, while the depth of the sandy layer on the soil surface limited the response of Rytidosperma. These results suggest that phylogenetic distance or relatedness might be key to optimizing priority response and effects when restoring ecosystems. The other variables found to enhance native species’ competitive abilities (seed mass, seeding density of Rytidosperma and possibly soil moisture) indicate the importance of considering a variety of factors to optimize restoration based on priority effects.

The interaction between high fire frequency and long flooding seasons maintains open vegetation in floodplains, while low fire frequency and no flooding can lead to forest development. In the Kadiwéu Indigenous Territory (IT), in the ecotone between the Cerrado and the Pantanal biomes in Brazil, the diversified spatio-temporal patterns of fire activity affect the diversity of floral functional traits and plant phenological strategies. Given this scenario, we sampled tree and non-tree species abundance data in 156 plots subject to different flood levels and fire frequencies in the Kadiwéu IT. Based on flooding regimes and fire frequency data series from 2001 to 2021, we classify the sample sites as floodable or flood-free areas under high (annual or biennial burn), moderate (three-yearly burn), or low (burning at four-year intervals or more) fire frequency. We analyzed the effects of flooding and fire frequency on plant species richness, abundance, and beta diversity (β). In general, tree density did not affect non-tree species richness. The species richness on the patches with different fire frequency category was generally similar, especially regarding the tree species. However, the combined effect of fire and flooding shifted the species composition. Variability in fire frequency across the landscapes support β-diversity maintenance in ecotonal vegetation between tropical wetlands and savannas. Furthermore, the similarity in species composition between floodable and flood-free areas at the same fire frequency category is low due to differences in abundance and species replacement. As part of adaptive fire management, we suggest maintaining a heterogeneous mosaic of fire frequencies in the landscape.

Understory woody plants are increasing in open Mediterranean oak open woodlands as a result of a number of factors, including land abandonment and/or less active management. This change in vegetation cover has many implications—such as increased fire hazard, changes in plant and animal biodiversity, reduced ability of oak trees to regenerate, and altered soil infiltrability. Until now little work has been done to assess the effects of understory woody plants on soil infiltrability in these ecosystems. The goal of this study was to explore those effects in areas that have experienced heavy grazing vs. areas that have been protected from grazing. We found that (1) In heavily grazed areas, soil infiltrability was dramatically lower than in areas protected from grazing—except in soils under shrubs, where infiltrability was comparable;(2) In areas protected from grazing, there was little difference in soil infiltrability between shrub-covered areas and open areas; and (3) In grazing-protected areas, soil infiltrability progressively increased over a 23-year period of test measurements. Our results suggest that where open oak woodlands are heavily grazed, shrub patches may provide benefits in terms of improved soil health, likely because shrubs protect the soil from trampling (reducing soil compaction). There may be some benefit in managing open oak woodlands to maintain heterogeneous vegetation cover—a mosaic of herbaceous and woody patches.

Deciphering the mechanisms driving biomass mean annual increment (MAI) in planted and natural forests subject to complex environmental constraints is useful for understanding carbon cycling in forest ecosystems. Based on a large-scale biomass growth dataset, this study used partial least squares path modeling to quantify the differential impacts of the coupling effects of climate, soil properties, site conditions, stand characteristics, and species richness on the MAI of planted and natural forests in China. The results showed that the degree of regulation of MAI by the stand and environmental factors was related to the specificity of forest origin. Increases in leaf area index, clay, and pH had a direct positive effect on MAI in natural and planted forests, while latitude had an indirect negative effect. In contrast, MAI in natural forests was indirectly negatively affected by increases in clay and pH, whereas MAI in planted forests was indirectly positively affected by them. Increases in temperature and precipitation had a positive effect on MAI in natural forests but an indirect negative effect on MAI in planted forests. Furthermore, MAI in natural forests was positively influenced by species richness, both directly and indirectly. We recommend deep plowing and fertilization to increase clay content and neutralize soil pH during intensive forest management practices and implementing multi-species silvicultural regulations to mitigate biodiversity loss and improve productivity.

Fire is a key trigger for the germination of serotinous plants in Mediterranean environments. Despite the availability of ample investigations into how fire contributes to plant fitness and germination patterns in pyriscent plants, there is no published content on how fire and associated heat and smoke factors influence germination of the group of plants successfully invading a particular biome. In this meta-analytic study, 29 studies were collated regarding the effects on germination of the temperature range corresponding to Mediterranean subsoil fire temperatures (50–99 °C), and a further 29 experiments were used to reveal the effects on germination of soil surface temperatures (100–120 °C) during Mediterranean fires. 24 studies were selected to investigate the effects of smoke during a shorter and longer exposure duration to reveal the boundaries of imbibition and toxicity associated with fire smoke. The chosen experiments performed heat shocks or smoke treatments on the invasive species found in the Mediterranean biome- a part of the globe that experiences periodic, extensive fire regimes. These experiments were then subsequently categorized into herbaceous or ligneous plants to study whether type of serotiny is associated with morphology life history. The results showed that generally, soil fire temperatures have a positive effect on the germination rate of invasive plants but only significantly in the case of invasive ligneous plants. Additionally, subsoil fire temperatures trigger invasive plant germination significantly, whereas soil surface fire temperatures do not. Only short exposure periods (c.a. 5 min) to smoke produced a positive effect in the germination of invasive plants. Longer exposures can be toxic and prevent germination. Herbaceous invasive plants responded positively to smoke treatments and ligneous invasive plants responded positively to heat shock. Our results highlight the importance of fire components (high temperature and smoke) in the success of many invasive plant species in Mediterranean environments.

Dendrolimus pini is a severe pest of Scots pine forests in many European countries. The area and frequency of its outbreaks in Poland has increased since 1990s. Outbreak probability is predicted to increase in yet non-outbreak parts of Europe due to climate change. Several studies have focused on the effect of meteorological factors favorable for D. pini outbreaks. However, tree stand, soil, site, and topographic characteristics have been rarely considered, particularly at a fine spatial level (subcompartment, which delimits an individual stand). Therefore, our study aimed to determine the characteristics of D. pini primary outbreak foci (POF). Topographic variables were calculated from a digital terrain model. All the other variables originated from forest inventory and are available to foresters at the stand level for daily management. Random Forest (RF) procedure was applied to analyze two data sets: with and without topographic variables. The analysis revealed that the most important variables common for both models were soil type/subtype and diameter-to-age ratio, with poor Albic Podzols (Ochric) and Albic Brunic Arenosols (Protospodic) and low values (0.27–0.38) of diameter-to-age ratio characterizing POF. The other most important factors in the RF model with all variables were three topographic variables indicating that flat and hilly terrains are typical for POF. In the RF model without topographic variables, additional important variables were site moisture (dry and fresh sites) and site class (I–V). Out of other variables, stand age and tree density also deserve consideration, with older (over 60 years) and denser (above 0.8) stands being more predisposed to the D. pini outbreaks. For pine stands growing on poor soils and in sites with water shortages, stand density seems to be the only factor that foresters can modify to improve conditions for tree growth. The relatively high overall accuracy of RF models with and without topographic variables (0.75 and 0.68, respectively, based on training and test data subsamples) and their high sensitivity in particular (0.94 for both models) make them a useful and easy-to-implement tool for detecting and mapping outbreak foci of D. pini and subsequent planning a distribution of monitoring plots.

In Mediterranean climates, drought is recognized as the main abiotic stress negatively affecting plant survival and growth after establishment. However, several factors besides water scarcity interact to affect plant performance, including stocktype, field establishment techniques, environmental variability, and the inherent ecological requirements of the target species. To fully comprehend the extent each of these factors influences plant performance, we analyzed plant survival, growth, and physiological performance of contrasting stocktypes of Nothofagus glauca seedlings, a shade-intolerant tree species from Mediterranean central Chile, established under different environmental conditions characterized by a shrubland versus a forest canopy cover. We hypothesize that nitrogen-loaded plants will have higher survival and growth during establishment, and that higher performance will be observed under the shrubland conditions, despite the presence of water constraints that are usually observed in more open canopies. Our experimental design induced contrasting environmental conditions in which the forest canopy was characterized by lower irradiance and water availability during summer versus the shrubland condition. As expected, bigger and nutrient-loaded N. glauca plants had better field performance in terms of survival and growth. After three years of assessment, we did not observe differences in survival between canopy conditions, but plants established under shrubland canopy presented significantly higher biomass accumulation and better water status. According to our relative importance analysis, we observed that soil water availability was the most relevant factor for plant survival, but plants showed more growth when established under a condition of increased irradiance. Considering that plant performance is explained by the combined response of survival and growth, we suggest that under Mediterranean conditions, each response could be independently affected by separate environmental factors as well as by target species biology (i.e., shade tolerant or shade-intolerant).

Vegetation structural complexity has been identified as a vital factor for forest ecosystem function, stability, and resilience. However, agricultural land with much reduced structural complexity has largely replaced natural forests in the tropics. Therefore, restoring structural complexity in large-scale plantation monocultures by introducing agroforestry systems may counteract the loss of biodiversity and ecosystem functions. However, we still have limited knowledge of how the structural complexity of agroforests develops under different restoration treatments. We established a large-scale biodiversity enrichment experiment in a conventional monoculture oil palm plantation in Sumatra, Indonesia. In this experiment, agroforests were implemented by planting clusters of native trees (“tree islands”) within the oil palm plantation, systematically varying initially planted tree richness ranging from 0–6 (0 corresponding to natural regeneration only) and plot area (25–1600 m²). We tested the effect of the experimental treatments on nine years of the development of local structural complexity using a stand structural complexity index (SSCI) derived from terrestrial laser scanning. We found that tree planting and natural regeneration treatments promoted structural complexity by creating denser and more complex vegetation structures. Plots with a tree planting treatment tended to show greater structural complexity than plots with natural regeneration only. However, during the study period, oil palms still dominated heights, and the temporal change in structural complexity among plots with or without a tree planting treatment did not differ. As for plot area, our results indicate that structural complexity looking from the center of plots did not necessarily depend on the area during the study period, and even small tree islands can increase local structural complexity in a monoculture oil palm plantation. Initially planted tree richness did not significantly affect the development of structural complexity. Nine years after establishment, not planted trees but regenerated woody plants strongly positively affected vegetation density and structural complexity. Our findings highlight that sustaining vegetation density below oil palm canopies is a key strategy to increase the structural complexity of oil palm landscapes.

Forests, especially in the northern latitudes, are vulnerable ecosystems to climate change, and tree-ring data offer insights into growth-climate relationships as an important effect. Using the National Forest Inventory plot network, we analysed these correlations for the two dominant conifer species in Norway – Norway spruce and Scots pine – for the 1960–2020 period. For both species, the June climate was an important driver of radial growth during this period. Countrywide, the climate-growth correlations divided the Norwegian forests into spatial clusters following a broad shift from temperature- to water-sensitivity of growth with latitude and altitude. The clusters were delineated by a mean 1960–2020 June temperature of ca. 12°C for Norway spruce and Scots pine. The annual mean growing season and July temperatures – but not June temperature – has increased by 1.0 °C between the 1960–1990 and 1990–2020 periods, with a slight increase in precipitation. Despite this warming and wetting trend, the long-term growth-climate relationship has remained relatively stable between 1960 and 1990 and 1990–2020 for both species. The threshold between temperature and water-sensitive growth has not changed in the last two 31-year periods, following the stability of the June temperature compared with other months during the growing season. These findings highlight geographically coherent regions in Norway, segregating between temperature- and water-sensitive radial growth for the two major conifer species, temporally stable in the long-term for the 1960–2020 period studied.