查看更多>>摘要：Tree allometric models are crucial to accurate forest biomass assessment, but the acquisition of biomass data is one of the most important limitations in establishing biomass models. This study aims to propose an improved investigation method to quickly and practically obtain biomass data, establish species-specific allometric equations and evaluate the biomass allocation pattern for various tree species in a broad-leaved Korean pine forest in northeast China. Based on the non-destructive measurement and sampling of 390 trees from 15 tree species, partial and aggregate biomass models with DBH and DBH2 x H as predictors were established. Results indicated that all allometric models could effectively estimate the dependent variables, and almost no antilog correction was required. Specifically, for the stem and bark components of most tree species, using the DBH2 x H predictor improved the prediction performance of the model. However, DBH was the best predictor for branch and leaf biomass models. The biomass allocation of trees was affected by tree diameter. Small-diameter trees (DBH < 8) had more leaf investment than other size trees, medium-diameter trees (8 < DBH 20) increased the allocation of resources to stems, and large-diameter trees (DBH 20) paid more attention to the growth and accumulation of branches. Our allometric model and biomass allocation research based on the non-destructive measurement and sampling will help improve the accuracy of biomass assessment in broad-leaved Korean pine forests and advance our understanding of woody plant development and survival strategies.
Millward, Lindsay S.Wilson, Todd M.Weldy, Matt J.Rowland, Mary M....
15页
查看更多>>摘要：There is a growing interest and investment in restoring riparian areas in the Pacific Northwest to protect biodiversity and water quality, and to restore quality habitat for threatened fish species. However, these management activities change vegetation conditions and potentially impact terrestrial species in these ecosystems. Our objective was to estimate associations between small mammals and 4 broad cover types-conifers, shrubs, grasses, and forbs-in riparian areas within the Blue Mountains of northeast Oregon, USA. We estimated abundances and spatial association for 10 small mammal species using a multispecies hierarchical abundance model and mark-recapture data collected on 36 sites from 2014 to 2017. We predicted that forest-associated species would be more abundant with greater conifer cover, that increases in shrub cover would favor most species, and that increases in grass and forb cover would favor grassland-associated species. Yellow-pine chipmunks (Tamias amoenus) were positively associated with conifer cover, while long-tailed voles (Microtus longicaudus) and montane voles (Microtus montanus) were negatively associated with conifer cover. Associations with shrub cover were positive for bushy-tailed woodrats (Neotoma cinerea), deer mice (Peromyscus maniculatus), and yellow-pine chipmunks, but negative for montane voles. Bushy-tailed woodrats and montane voles were negatively associated with grass cover. This study is the first to characterize the riparian small mammal communities in this region and provides insights on the effects of restoration activities on riparian ecosystems in dry interior forests and grasslands. We suggest that riparian plantings, a ubiquitous restoration practice, will increase the relative abundances for some, but not all, small mammal species. We also demonstrate use of a new multi-species abundance model that can be a powerful tool for analyzing mark-recapture data because it allowed us to extend the scope of our analysis to data poor species by pooling information with data rich species.
Cansler, AlinaKane, Van R.Bartl-Geller, Bryce N.Churchill, Derek J....
14页
查看更多>>摘要：We evaluated the effects of postfire management on forest structure in mixed-conifer forests of northeastern Washington, USA. Postfire treatments were harvest-only, harvest combined with planting, planting-only, and postfire prescribed fire. We used aerial light detection and ranging (LiDAR) to measure vertical and horizontal components of postfire forest structure over a period of 2 to 32 years after fires. We compared treated areas to control areas with similar bioclimatic environments and past fire severity. We used niche overlap statistics to quantify distributions of individual forest structure components and PERMANOVA to assess forest structural response to the presence or absence of treatments, past fire severity, time since treatment, and bioclimatic setting. Harvest alone after fire decreased dominant tree height and reduced vertical canopy complexity and the cover of tall trees. Harvest combined with planting increased dominant tree height, vertical complexity, and cover in lower height strata. Planting and prescribed fires showed little difference in forest structure relative to untreated controls. Overall, the burn severity of the initial fire was the strongest influence on postfire structure, and many aspects of vertical and horizontal forest structure showed little difference with increasing time since fire.
Turczanski, KrzysztofDyderski, Marcin K.Andrzejewska, Agnieszka
14页
查看更多>>摘要：Ash disease caused by ascomycete fungus Hymenoscyphus fraxineus leads to the retreat of ash, particularly in ashdominated stands characterized by moist, fertile, and neutral soils. Thus, it has a more severe impact on species regeneration and survival in ash optimal sites. We aimed to investigate the joint effects of seed dispersal limitation triggered by the distance from seed source, as well as soil fertility, browsing, and understory vegetation on ash natural regeneration in optimal and neighboring suboptimal sites. We examined ash regeneration within 40 circular plots (25 m2) in Western Poland along soil fertility gradient and increasing distance from seed source (0-100 m). We confirmed the seed dispersal limitation of ash regeneration. We found that the increase of distance from seed source increases ash natural regeneration (both of <0.6 and 0.6-1.3 m height) survival by escaping distance-dependent mortality, referring to the Janzen-Connell effect. Moreover, soil drivers i.e. groundwater table level, CaCO3, and soil C:N influenced ash regeneration damage rate. Furthermore, we indicated that light availability can enhance ash regeneration. We found the highest browsing in sites with the highest ash natural regeneration density. Understory species composition was related to ash regeneration density, browsing, and damage proportion, indicating that species typical of mesic broadleaved forests can be considered as positive indicators of the ash regeneration niche. In conclusion, we state that suboptimal sites can act as refugees for ash, helping this species to persist over ash dieback. Therefore, we recommend broadening the scope of ash conservation and silviculture into suboptimal sites, that can host ash regeneration and allow it to emerge and reproduce. Such sites in the neighborhood of typical ash sites damaged by H. fraxineus can in the future serve as seed sources for forest regeneration and improve the resilience of the forest ecosystem.
查看更多>>摘要：Successional planting of Eucalyptus is known to significantly affect soil quality. However, the accompanying changes in the bacterial and fungal community structure, co-occurrence network pattern, and microbial functions are unclear. This prevents a full assessment of the impact of successional planting patterns on soil ecosystem services. In this study, we investigated the effect of replacing Pinus massoniana plantations with multigenerational successional planting of Eucalyptus on soil bacterial and fungal communities. The results showed that it elicited significant declines in soil multifunctionality and the diversity and richness of the fungal community, together with a significant increase in soil bulk density. The third and fourth-generation plantations had notably reduced microbial network complexity, robustness, and association between microbial taxa. Successional planting also significantly changed the relative abundance of dominant microbial groups at the phylum and order levels, which subsequently caused dramatic changes in microbial functions. With successive planting generations, the soil bacterial community shifted from carbon-using to nitrogen-using bacteria, and the fungal community shifted from saprophytic and pathogenic to symbiotic fungi. From the above results, we concluded that multi-generation plantation of Eucalyptus has a significant negative impact on soil multifunctionality and microbial community, and after two generations of successive planting, it should be considered to change the plantation management pattern. This work provides a theoretical reference for the sustainable management of Eucalyptus plantations.
Badik, Kevin J.Wilson, CodieKampf, Stephanie K.Saito, Laurel...
10页
查看更多>>摘要：Increasing fire activity in the American west heightens the need for natural resource managers to identify where risk associated with post-fire effects is greatest. This is particularly true for water resources, as many headwater forests are at risk for stand replacing fires. However, current methods to model post-fire erosion often have tradeoffs between model area and spatial resolution. We introduce a novel approach to combine a process-based erosion model and state-and-transition simulation modeling to estimate post-fire sediment yield and identify areas of high risk. We demonstrate how this method can be applied at three scales: large watershed, subwatershed, and single fire event. The combination of the erosion model and state-and-transition simulation model allowed us to identify areas of post-fire high sediment yield potential and increased likelihood of fire occurrence. This method can be used by land managers to prioritize pre-fire restoration practices or post-fire rehabilitation actions.
Tangney, R.Miller, R. G.Fontaine, J. B.Veber, W. P....
15页
查看更多>>摘要：Increasing extreme wildfire occurrence globally is boosting demand to understand the fuel dynamics and fire risk of fire-prone areas. This is particularly pressing in fire-prone, Mediterranean climate-type vegetation, such as the Banksia woodlands surrounding metropolitan Perth, southwestern Australia. Despite an extensive wildlandurban interface and frequent fire occurrence, fuel accumulation and the spatial variation in fuel risk is not well quantified across the broad extent of this ecosystem. Using a space for time sampling approach to generate a chronosequence of time since fire, we selected sites that spanned across two distinct sandy soil types (Spearwood and Bassendean sands) and a rainfall gradient (550 to 750 mm north-south). We examined 82 sites in Banksia woodlands, southwestern Australia. Of the 82 sites, 44 burnt during the measurement period (2016 to 2021), which provided the opportunity for fuel measurements following fire (resulting in total N = 126). We wanted to answer two key questions: 1) How do measures of fuel load (mass) and arrangement (structure and continuity) vary across space and time, particularly with respect to time since the last fire? 2) How do biophysical drivers, such as soil type and rainfall, influence fuel accumulation and arrangement, and do these covariates improve litter fuel modelling beyond traditional asymptotic models? We found that fine surface fuel loads (litter and small twigs) differed between sand types, accumulating faster and reaching a higher peak on Spearwood sands (7-9 Mg ha-1) compared to Bassendean sands (6-7 Mg ha-1). Shrub layer fuel loads also accumulated faster on Spearwood sands than on Bassendean sands. While shrub layer fuels on Spearwood sands peaked at 14 years and declined thereafter, those on Bassendean sand did not decline over time but have lower overall connectivity. Total fine fuels (fine surface plus fine shrub layer fuels) had no significant decline over the same time period, on either sand type. Total fine fuel loads reached a peak of 9-10 Mg ha-1 between 13- and 20-years following fire, depending on the underlying sand type. Our quantitative fuel accumulation models confirmed the strength of time since fire as a predictor of hazard, but nonetheless included up to 40% unexplained variance. Importantly, while components fluctuated over time, the combined total of fine fuels did not decline with the long absence of fire, suggesting fire risk does not necessarily decrease in long unburned vegetation.
查看更多>>摘要：Litter and understory play important roles in maintaining structure and functions of belowground ecosystems in forests. However, how litter and understory affect soil microbial community is unclear. As part of a three-year (2016-2018) manipulative experiment, this study was designed to evaluate the effects of litter and/or understory removal on soil microbial community in a coniferous-broadleaved mixed forest of the subtropical-warm temperate transition zone in Central China. The results showed that soil moisture, NO3- -N, NH4+-N, and dissolved organic carbon were decreased under litter removal, but remained unchanged under understory removal. Total, bacteria, and actinomycetes PLFAs were significantly reduced by 11.2%, 16.3%, and 11.0% under litter removal, and by 10.1%, 13.3%, and 12.5% under understory removal, respectively. Both litter and understory removal suppressed network complexity of soil microbial community, but litter removal showed much stronger impacts on the biomass (-14.9 mg kg- 1 vs. -10.9 mg kg- 1) and composition (-7.77% vs. -2.89%) of bacteria (including gram-positive and gram-negative bacteria) as well as fungi to bacteria ratio than understory removal. Changes of soil NH4+-N and moisture might be primarily responsible for the inhibitory effects of litter removal on soil gram-positive and gram-negative bacterial biomass, respectively. Our findings highlight the contrasting responses of soil microbial community to litter and understory removal and would facilitate the mechanistic understanding of these two management practices on belowground ecology in climate transitional forests.
NSTL
Elsevier