Disturbance and regeneration dynamics of a mixed Korean pine dominated forest on Changbai Mountain,North-Eastern China

We used dendrochronological methods to study disturbance history of a mixed Korean pine (Pinus koraiensis Siebold et Zuccarini) dominated forest on the northern slope of Changbai Mountain, North Eastern China, over 1770–2000. Frequent small-scale canopy gaps and infrequent medium-scale canopy disturbances dominated natural disturbance regime in the forest, which did not experience stand-replacing disturbances over the studied period. Percentages of growth releases in subcanopy trees were below 6% in most decades, suggesting that disturbances initiating these releases were of low intensity. Strong winds were likely cause of moderate disturbance events. Two episodes with increased disturbance rates (19% and 13%) were dated to the 1920s and 1980s, timing of the 1980s event was consistent with a hurricane occurred in 1986 on the western slope of the Changbai Mountain. Age structure and growth release analyses revealed species-specific regeneration strategies of canopy dominants. Shade-intolerant Olga bay larch (Larix olgensis Henry) recruited mainly before the 1860s. Recruitment of moderately shade-tolerant P. koraiensis occurred as several regeneration waves (1820s, 1850s, 1870–1880s, 1930s, and 1990–2000s) of moderate intensity. Shade-tolerant Jezo spruce (Picea jezoensis Carr. var. komarovii (V. Vassil.) Cheng et L.K.Fu) and Manchurian fir (Abies nephrolepis (Trautv.) Maxim.) regenerated continuously over the last 220 and 130 years, respectively. Enhanced recruitment of P. koraiensis, P. jezoensis, and A. nephrolepis was observed during the 1930s and 1990s, coinciding with increased growth release frequency in the 1920s and 1980s, and suggesting disturbance events of moderate intensity. Our results indicate that the current disturbance regime of the mixed Korean pine dominated forest maintains coexistence of light-demanding and shade-tolerant species and that change in wind climate may be particularly important for future forest composition.     

化感作用的研究意义及发展前景

对化感作用在生态学、林业、农业等领域的理论及实践意义进行综述与探讨,并分析了其今后的发展方向.化感作用有助于更加合理地解释生态系统中植物组成与分布、群落演替、协同进化和生物入侵等现象;在林业生产的森林更新、混交林培育中有时会起到决定性作用;在农业上,单作、轮作、覆盖等各种种植方式均受化感影响,此外,一些化感物质可用作杀虫剂和除草剂,从而减轻对环境的污染水体中同样存在化感作用.培育新的抗虫害、抑草品种,分离、鉴定新的化感物质,深入揭示化感作用的机制,是今后化感作用的研究重点.     

Pointer years revisited: Does one method fit all? A clarifying discussion

The identification of pointer years is central in tree-ring studies, for example, for crossdating or describing growth responses of trees to extreme events. Various methods exist to define pointer years. To these methods, a presumably new method was recently added, i.e. the standardized growth change (SGC) method (Buras et al., 2020; 2022), which was claimed by the authors to outperform existing methods. In this Communication, we perform a concise method review and compare the SGC method with existing pointer year detection methods using simulated tree-ring data that contain diverse signal patterns. We not only provide evidence that the SGC method has already been proposed in 1994, but furthermore show that each method for pointer year detection, including SGC, has its own strengths and weaknesses. Given that each method highlights different aspects of extraordinary growth, we repeat our conclusion from Jetschke et al. (2019), namely that no method can be substituted by others completely, and thus be claimed as being ‘best’. As applies to all methods for pointer year detection, SGC is a complementary but certainly powerful method. We request the dendro-community to provide clear explanations in future studies on how the term pointer year was used to prevent unnecessary confusion and misunderstanding.     

Characterizing growth rings in the trees of Perú: A wood anatomical overview for potential applications in dendroecological-related fields

Sustainable forestry requires accurate ecological information such as species composition, growth rates and recruitment dynamics. Tree growth rates are usually obtained through long-term periodic re-measurements of individual trees or through the analysis of tree growth rings in stem cross sections. However, tree growth ring analysis was traditionally thought to be only possible in biomes with strong seasonality such as those found in high latitude temperate regions. A lack of data on the occurrence and characteristics of tree rings in tropical trees may be due to a lack of investigations. Here we characterise the growth rings of 183 tree species from seven forest types across an altitudinal gradient in northern and central Perú at macro- and microscopic levels. A correspondence analysis showed an association between phylogenetic relatedness and the level of distinctiveness in the growth rings. Deciduous species of seasonally dry tropical forests were associated with distinct growth rings and mainly delimited by marginal parenchyma, while indistinct growth rings were associated with evergreen trees from lowland Amazonian and pre-montane wet forests. Additionally, for the first time the presence of growth ring boundaries defined by marginal phloem is reported in two tropical tree species, Gallesia integrifolia (Spreng.) Harms and Vochysia mapirensis Rusby. This contribution represents the most exhaustive record to date of the occurrence and anatomy of growth rings in trees of the Peruvian tropics, which can be used to inform future dendrochronological studies.     

PERSISTENCE OF A THREE INTERACTING PREY-PREDATOR MODEL WITH REFUGES

IIntroductionWeknowthataveryimportantconceptInmathematicalecologyIsperslstenceorpermanence．Themodelingofthreeormorespedeshasbeendiscussedbysomeauthors．FreedmanandWaltman［‘·’JdlscussedtheperslstenceofthreeInteractingKolmogorovtypemodelsformedbyprey－predatorandthreecompectltlvepopulations．HutsonandLaw［’Jstudledthesimilarmodeltoo．ItIsshownthataKolmogorovthree－spedessystemwithvariouscasescanbepersistent．TheecologymodelsInwhichthepreyspedeshasdlffuslonbehaviorsorrefugeshavebeendi…     

Il Conte G. B. Samaritani (1821–1894) e le Sue Raccolte Botaniche in Egitto ed in Oriente

Abstract

Bryophytes are excellent indicator organisms for monitoring environmental changes to which they could be more sensitive than vascular plants but our knowledge on their adaptation to alpine conditions is still very poor. Research programmes were set up to establish the ecological parameters for bryophyte distribution along the altitudinal gradient as well as for a better understanding of the population biology of alpine bryophytes.     

Seasonality matters—The effects of past and projected seasonal climate change on the growth of native and exotic conifer species in Central Europe

Norway spruce is one of the economically most important tree species in Central European forestry. However, its high susceptibility to droughts poses a strong challenge to its cultivation under future conditions with likely more frequent and prolonged droughts and shifts in the seasonal climate. To compensate for expected losses of forest areas suitable for the cultivation of spruce, more drought-tolerant species are required. Silver fir and Douglas fir are two potential candidates, which promise lower drought susceptibility and equal or even higher yield when compared to Norway spruce.Using the Black Forest as a regional case study, we assessed the effects of seasonal climate change, including drought stress, on tree-ring width formation of these three economically relevant conifer species over the last 60 years. In addition, we projected potential species-specific growth changes under different climate change scenarios until 2100.Our results suggest that both silver fir and Douglas fir will possibly experience growth increases in a warmer future climate, as predicted under the 4.5 and 8.5 Representative Concentration Pathway (RCP) climate change scenarios, whereas growth of spruce is expected to decline. Moreover, drought susceptibility in silver fir and Douglas fir is lower than in spruce, as shown for past drought events, and their ability to benefit from milder winters and springs could play a major role in their capacity to compensate for drier summers in the near to mid-term future. This study highlights the need to advance our understanding of the processes that drive drought resistance and resilience in tree species to guide management strategies in the face of climate change.     

Predicting and mapping the spatial distribution of Chamaecyparis formosensis in central Taiwan in a GIS with species distribution models

Analyzing the relationship between species and environment is always a focal question of ecological research. In recent years species distribution models (SDMs) has been widely used to predict the spatial distribution of species. SDMs are numerical tools that combine observations and species occurrence or abundance with environmental variables to predict the spatial distribution of species across landscapes, sometimes requiring extrapolation in space and time. Chamaecyparis formosensis (Taiwan red cypress, TRCs) is a coniferous species endemic to Taiwan, where it natural grows in the central mountains at moderate to high altitudes of 800–2800 m, and most stands in the range of 1500–2150 m. It is threatened by habitat loss and over-cutting for its valuable timber. To preserve TRCs species and achieve sustainable use of biological resources, we choose TRCs as a target for the study to predict its distribution in central Taiwan.The pure forests of TRCs in the study area were mainly located in Pachsienshan (P), Shouchentashan (S) and Baigou Mountain (B) in central Taiwan, and the distribution data were originally obtained by The Third Survey of Forest Resources and Land Use in Taiwan. Elevation, slope, aspect, and three vegetation indices were derived from both SPOT-5 satellite images and DEM. GIS technique was used to overlay those factors. Discriminant analysis (DA), decision tree (DT) and maximum entropy (MAXENT), three commonly used SDMs, were applied based on above-mentioned six variables to predict the suitable habitat of TRCs, and to evaluate which the best model is in terms of accuracy and efficiency. Three experiment designs (ED1, ED2 and ED3) with different combinations of samples were used for model building and validation. The 200 target samples were collected from the site P–B, B–S and P–S for model building under ED1, ED2 and ED3 respectively, while the 100 samples were collected from the site S, P and B for model validation. All experiment designs had same 1350 background samples. The results showed that the overall accuracy and kappa coefficient of DT (96%, 0.88) was higher than that of MAXENT (91%, 0.70), and their accuracies were better than that of DA (84%, 0.58). All the three models were highly efficient in implementation of model construction and evaluation, while the DT model was difficult for generating the entire predicted map of potential habitat due to its complex conditional sentence. Vegetation indices derived from SPOT-5 satellite images could not improve model accuracy because of its insufficiency of spectral resolution and spatial resolution. High spatial resolution and spectral resolution remotely sensed imagery should be used in our future research to improve model performance and reliability.     

Impacts of global changes and extreme hydroclimatic events on macroinvertebrate community structures in the French Rhône River

We assessed the temporal changes in and the relationships between the structures of the macroinvertebrate communities and the environmental conditions of the French Rhône River (the river from Lake Geneva to the Mediterranean Sea) over the last 20 years (1985–2004). Multisite environmental and biological datasets were analysed using multiple CO-inertia analysis (MCOA) and Procrustean analysis. Changes in environmental conditions were mainly marked by an improvement in water quality between 1985 and 1991 and by an increase in water temperature from 1985 onwards due to climate change. Improvement in water quality seemed to delay changes in community structures under global warming. We then observed trends in community structures coupled with high temperatures and a decrease in oxygen content. Interestingly, we observed both gradual changes and rapid switches in community states. These shifts seemed coupled to extreme hydroclimatic events (i.e. pulse disturbances). Floods and the 2003 heatwave enhanced the development of eurytolerant and invasive taxa which were probably able to take advantage of gradual warming environmental conditions. Despite various site-specific “press” constraints (e.g. hydropower schemes, nuclear power plants), similar changes in community structures were observed along the French Rhône River. Such consistency in temporal processes at large geographical scales underlined the strength of hydroclimatic constraints on community dynamics compared to specific local disturbances. Finally, community structures did not show any sign of recovery, and their relative sensitivities to extreme hydroclimatic events seemed to increase with time. Thus, our results suggest that global changes may reduce the resilience of current community states.     

Reducing competition vs. improving resistance to disturbances in the environment

 We study a metapopulation model for competition between two species in environments affected by regular disturbances. We give precise conditions for the coexistence of both species. We show that both species are more likely to coexist under an intermediate disturbance frequency. Since the rates of interspecific competition, as well as the frequency of the disturbances in the environment are given explicitly, it is possible to analyze the role they play in determining the final equilibrium level of the species involved. Special interest is given to comparing the effect of increasing resistance of the weak species to the environmental disturbances versus reducing the competition rate. It turns out that reducing the competition rate is never the better strategy under these conditions. Received: 29 April 1999