Wildfire Effects on Understory Vegetation,Natural Regeneration,and Forest Floor Fuels in a Sierran Mixed Conifer Stand

Wildfire effects on understory shrubs and herbs, regeneration of the seedling and sapling size classes, and downed and dead fuels were assessed in a mixed conifer stand located in the Lake Tahoe Basin in which California white fir (Abies concolor var. lowiana [Gord.] Lemm.) was most abundant but with Jeffrey pine (Pinus jeffreyi Grev. & Balf.) also prevalent. In burned and unburned stand portions, prefire measurements served as a basis of comparison for the postfire measurements pertinent to each study component. Fire severely suppressed the understory vegetation, which was dominated by shrubs such as bush chinquapin (Chrysolepis sempervirens [Kellogg] Hjelmqvist) and antelope bitterbrush (Purshia tridentata [Pursh] DC.), while a tepid postfire recovery of most of the preexisting species in the burned stand portion was augmented by new ones, including shrubs such as snowbrush (Ceanothus velutinus Douglas ex Hook.) and whitethorn (Ceanothus cordulatus Kellogg) ceanothus and herbs such as Holboell's rockcress (Arabis holboellii Hornem.). Tree seedling abundance was also substantially reduced in the burned portion, but the postfire population was dominated by Jeffrey pine whereas white fir had been most prevalent originally. Sapling regeneration was eliminated from the burned stand portion regardless of species. Downed and dead fuel loading was severely diminished by the fire, especially regarding fine fuels, permitting subsequent sheet erosion to imperil new seedling regeneration. These results contribute to an understanding of the direction and pace of postwildfire succession on sites occupied by Sierra Nevada mixed conifer and similar forest cover types, which is critical in decisions concerning the need for, and extent of, postfire site rehabilitation measures.     

Effects of feeding bamboo vinegar and acidifier as an antibiotic substitute on the growth performance and intestinal bacterial communities of weaned piglets

Abstract

The experiment was designed to evaluate effects of feeding bamboo vinegar (BV) and acidifier to substitute antibiotic on the growth performance and intestinal bacterial communities of weaned piglets. Three hundred and sixty weaned piglets (body weight (BW) = 10 ± 2 kg) were allocated into three treatments for 25 days of experiment feeding, with three replicates (pen) per treatment. A basal diet was added with antibiotics (Control), 0.4% BV and 0.25% acidifier I (BVAI), or 0.4% BV and 0.25% acidifier II (BVAII), respectively. No significant differences were observed in feed intake, final weight, average daily gain and feed to gain ratio (P > 0.05) among different treatments. The species richness and bacterial community diversities in feces were higher for the pigs in treatment BVAI and BVAII than those of pigs in the Control (36.5 and 1.55, respectively), with a significant difference between BVAII and the Control (P < 0.05). The bacterial communities of pigs in BVAI and BVAII clustered together, forming a cluster we designated as Cluster C and separated from another cluster in pigs fed antibiotic designated as Cluster A in the Control treatment. The results indicate that the 0.4% BV and 0.25% acidifier can replace antibiotics in the diets for piglets without negative effects on production and allow for greater diversity of the intestinal bacterial community compared to antibiotics.     

DCA、CCA和DCCA三种排序方法在中国草地植被群落中的应用现状

排序是用来分析植被与环境之间生态关系的重要手段。该文主要是对除趋势对应分析（DCA）、典范对应分析（CCA）和除趋势典范对应分析（DCCA）这三种排序方法进行总结，讨论它们在中国草地植被群落研究中的应用现状，并得出除趋势对应分析与聚类分析结合使用效果比较好，主要是用来揭示群落之间的关系，并且在实际的应用中也比较多，而典范对应分析和除趋势典范对应分析在揭示种与环境关系方面具有明显的优势，但是由于某些条件的限制，在实际研究中应用的比较少。可见这几种排序方法在实际应用中具有一定的优势，所以应该加强这方面的应用，更加深入的研究草地植被群落，以期对草地生态学及草地植被群落生态关系的研究工作发挥重要的借鉴作用。     

北京百花山落叶阔叶林群落的物种多样性特征

应用物种丰富度、Simpson多样性指数、Shannon-Wiener多样性指数、Pielou均匀度指数、Alatalo均匀度指数研究北京百花山落叶阔叶林中3种群落的物种多样性特征。结果表明：1）群落总体的多样性特征为黑桦-柔毛绣线菊-野青茅＋矮紫苞鸢尾群丛的物种丰富度最大,核桃楸-绒毛绣线菊-蓝萼香茶菜＋大油芒群丛的多样性指数最大,辽东栎-小花溲疏-披针苔草群丛均匀度指数最大;2）不同生长型的物种多样性特征为,草本层的物种丰富度、多样性指数大于灌木层和乔木层,均匀度指数的变化规律为灌木层〉草本层〉乔木层;3）乔木层与草本层、灌木层与草本层间的丰富度指数、多样性指数均有极显著差异,乔木层与灌木层、乔木层与草本层间的Pielou均匀度指数有显著差异。     

Quantifying plant species diversity in a Natura 2000 network: Old ideas and new proposals

Assessing the effects of the spatial components on species diversity in a network of protected areas represents an important step for assessing its conservation “capacity”. A clear evaluation on how α-, β-, and γ-diversity are partitioned among and within spatial scales can help to drive manager decisions and provide method for monitoring species diversity. Moving from these concepts, a probabilistic sample of plant species composition was here applied for quantifying plant species diversity within the Sites of Community Importance (SCIs) of the Natura 2000 network in the Siena Province. All analyses were performed separately for all species and those species defined as “focal” (included in regional, national or continental “red” lists). The results indicated that species richness of the SCIs differed from one location to another one independently from the sampling efforts. Diversity partitioning indicated that most of the flora diversity within the network was given by larger-scale β-diversity, i.e. the differences in species composition among SCIs. β-diversity was then decomposed in two components: β_Area (due to the differences in area among SCIs) and β_Replacement (due to the compositional differences across SCIs). β_Area was particularly important for all species, while β_Replacement was the most important factor for focal species. The consequent implications for monitoring and nature conservation strategies are discussed.     

Effect of desert plant ecophysiological adaptation on soil nematode communities

Nutrient source limitation in desert ecosystems enhances competition among plant communities, leading to creation of microhabitats beneath the shrubs that can determine composition and abundance of soil organisms. The aim of the study was to determine the effect of plant ecophysiological adaptation on soil nematode communities in the rhizosphere of tightly interweaving shrubby communities. Soil samples were collected monthly under the canopies of three perennial desert shrubs: Artemesia herba-alba, possessing the allelopathic ability to dominate in relationships with other plants; Reaumuria negevensis, a salt-resistant plant; and Noea mucronata, a typical dry desert shrub. An inter-plant area was used as a control. The results demonstrated that soil water content (SWC) and total organic carbon (C_org) were significantly different under different plants and inter-plant areas, with the highest values found under R. negevensis (SWC) and N. mucronata and R. negevensis (C_org). Plant parasite and omnivore-predator nematodes were more sensitive to the ecophysiological individual features of observed plants versus the total number of nematodes and bacteria- and fungi-feeding nematodes. Generally accepted ecological indices such as Wasilewska (WI), trophic diversity (T), maturity (MI, MMI), basal (BI), enrichment (EI), structure (SI), and channel (CI), pointed to specific ecological conditions under canopies of the observed plants.     

Artificial neural network modeling of microbial community structures in the Atlantic Forest of Brazil

Microbial communities vary across the landscape in forest soils, but prediction of their biomass and composition is a difficult challenge due to the large numbers of variables that influence their community structures. Here we examine the use of artificial neural network (ANN) models for extraction of patterns among soil chemical variables and microbial community structures in forest soils from three regions of the Atlantic Forest of Brazil. At each location, variations in soil chemical properties and FAME profiles of microbial community structures were mapped at 20 × 20 m intervals within 10 ha parcels. Geostatistical analyses showed that spatial variability in soil physical and chemical variables could be mapped at scale distances of 20 m, but that FAME profiles representing the microbial communities were highly variable and had no spatial dependence at the same scale in most cases. RDA analysis showed that FAME signatures representing different microbial groups were positively associated with soil pH, OM, P and base cations concentrations, whereas microbial biomass was negatively associated with the same environmental factors. In contrast, ANN models revealed clear relationships between microbial community structures at each parcel location, and generated verifiable predictions of variations in FAME profiles in relation to soil pH, texture, and the relative abundances of base cations. The results suggest that ANN modeling provides a useful approach for describing the relationships between microbial community structures and soil properties in tropical forest soils that were not able to be captured using geostatistical and RDA analyses.     

Management and restoration of fish communities in Lake Taihu, China

The economic development of the cities around Lake Taihu, China, has caused both environmental changes and ecological succession. The biodiversity of Lake Taihu has declined since 1970. Migratory fish, including anadromous, catadromous and semi-migratory fish, are either extinct or on the verge of extinction in Lake Taihu. Only lake dwellers persist. Several measures have been taken, such as restocking, closed seasons, sanctuaries for enhancement and even introductions to restore some original fish communities. Although these measures have achieved a certain degree of success, increased fishing activities or over-fishing have offset the benefits obtained. Moreover, cultural eutrophication of the lake and the pollution of the waterways connected with the lake are getting worse. This jeopardizes the remaining economically valuable species in the lake. Measures are required not only to control eutrophication and pollution, and to reduce the intensity of fishing, but also to address the wider biodiversity issues.     

Preliminary assessment of shallow water fish in three small intermittently open estuaries in southeastern Australia

Abstract Small and juvenile fish from three intermittently open estuaries in south-eastern Australia were sampled with a seine net to investigate species richness and the effect of estuary openings on assemblages. A total of 7285 fish were captured, representing 29 species. The most numerous fish were hardyhead, Atherinosoma microstoma Günther, flathead gudgeon, Philypnodon grandiceps Krefft, and non-native mosquito fish, Gambusia holbrooki Girard. Economic species included sand whiting, Sillago ciliata Cuvier, and sand mullet, Myxus elongatus Günther. Significant differences in the numbers of species and the numbers of individuals were found between estuaries, but were not observed for individual estuaries before and after opening. However, fish assemblages changed after opening, with several species recruiting from the ocean. Small, intermittently open estuaries present a complex management problem. These waterbodies are easily degraded in terms of water quality and sedimentation, and are often opened mechanically as a result of flooding or health concerns. The importance of these areas as fish habitats and the recorded changes in fish assemblages after opening suggest that careful management is required, including improved assessment of the impact of entrance manipulation.