珠江流域植被覆盖时空变化分析

为阐明珠江流域植被覆盖变化的整体状况,基于RS与GIS技术,应用美国国家航天航空局最新的全球植被指数变化研究数据(GIMMS),对珠江流域1982~2003年间的地表植被覆盖的空间分布及时间序列变化进行了综合分析。结果表明:(1)22年来,珠江流域大部分地区的NDVI都呈现不同程度的下降趋势,表明珠江流域植被活动在减弱;(2)从季节变化来看,珠江流域平均植被覆盖除春季呈不显著上升外,其余各季均呈不显著下降趋势;(3)空间上,中下游地区都呈现不同程度的下降趋势,其中珠江三角洲地区达到了极显著水平;而上游南、北盘江流域、右江、左江及郁江流域则呈不显著增加趋势。这种空间异质性是由于城市化过程、农业生产活动、区域气候特征等综合因素作用的结果。     

Environmental controls of NDVI dynamics in Patagonia based on NOAA-AVHRR satellite data

Abstract. Variation in vegetation in extra-Andean Patagonia (Argentina) was analyzed using spectral data derived from AVHRR/NOAA satellite. The study of seasonal dynamics of the Normalized Difference Vegetation Index (NDVI, i.e. a combined index of the reflection in the red and infrared bands) highlighted similarities in functional aspects between regional vegetation units which are dissimilar in a geographical, physiognomical and/or floristical way, and also suggested that gross primary production is correlated with mean annual rainfall. The first axis in a Principal Component Analysis of NDVI data was correlated (r² = 0.90) with NDVI as integrated for the study period. The second axis was correlated (r² = 0.50) with the differences in NDVI during the growing season, reflecting seasonality. Mean annual rainfall accounted for 60% of integrated NDVI variability among vegetation units. Much of the residual variance (62%) was accounted for by the inverse of the distance to the Atlantic Ocean, which is interpreted as an ocean effect on vegetation functioning in the extra-Andean Patagonia.     

A hot-spot of biodiversity in Northern Patagonia,Argentina

Located along the Argentine coastline of northern Patagonia, are San Matías (SMG) and San José (SJG) gulfs; although they are regarded as an area with a high-priority conservational status, knowledge on their diversity is currently fragmentary. Studies on molluscs from this area have been historically centred in economic resources and few works have referred to non-commercial species. The present study aims to document the biological diversity of molluscs at the SMG/SJG area, in order to determine the significance of these two gulfs in the context of the Argentine marine fauna; to evaluate how well represented is this fauna in three protected areas; and to compare the fauna present in the protected areas with that of a non-protected area. For that purpose, molluscs coming from 132 sampling stations, ranging from the intertidal to 170 m depth, were studied, and a thorough bibliographic compilation was performed. A total of 196 species of molluscs are reported for the area. Surprisingly, almost one third of these species lacked previous records for SMG/SJG, including several new/possibly new species. The three studied protected areas contain 88.3% of the species recognised for the entire SMG/SJG area. Although several species appear as exclusive from one of these three areas, many of them are also present in an intermediately located, non-protected area. Molluscan diversity at the SMG/SJG area is greater than previously thought, comprising about 41.4% of the bivalves and 37.8% of the gastropods present in the Argentine shelf; thus suggesting that the area may be considered as a hot-spot of diversity in the Argentine Sea.     

Bayesian Space-Time Patterns and Climatic Determinants of Bovine Anaplasmosis

The space-time pattern and environmental drivers (land cover, climate) of bovine anaplasmosis in the Midwestern state of Kansas was retrospectively evaluated using Bayesian hierarchical spatio-temporal models and publicly available, remotely-sensed environmental covariate information. Cases of bovine anaplasmosis positively diagnosed at Kansas State Veterinary Diagnostic Laboratory (n = 478) between years 2005–2013 were used to construct the models, which included random effects for space, time and space-time interaction effects with defined priors, and fixed-effect covariates selected a priori using an univariate screening procedure. The Bayesian posterior median and 95% credible intervals for the space-time interaction term in the best-fitting covariate model indicated a steady progression of bovine anaplasmosis over time and geographic area in the state. Posterior median estimates and 95% credible intervals derived for covariates in the final covariate model indicated land surface temperature (minimum), relative humidity and diurnal temperature range to be important risk factors for bovine anaplasmosis in the study. The model performance measured using the Area Under the Curve (AUC) value indicated a good performance for the covariate model (> 0.7). The relevance of climatological factors for bovine anaplasmosis is discussed.     

Risks of Neglecting Phenology When Assessing Climatic Controls of Primary Production

Ecosystems - We evaluated the effect that integrating annual aboveground net primary production (ANPP) along different 12-month periods has on temporal models of productivity (ANPP as a linear...     

Contrasting Climatic Controls on the Estimated Productivity of Global Terrestrial Biomes

Net primary productivity (NPP) represents the greatest annual carbon flux from the atmosphere to the biosphere, is an important component of seasonal fluctuations in atmospheric CO₂ concentrations, and is the most critical biotic component of the global carbon cycle. NPP measures products of major economic and social importance, such as crop yield and forest production. Given that global NPP can not be measured directly, model simulations must provide understanding of its global spatial and temporal dynamics. In this study, we used the biogeochemical model BIOME-BGC to simulate global terrestrial NPP and assessed relative importance of climatic controls (temperature, water availability, and radiation) in limiting NPP in the array of climatic combinations found globally. The degree of limitation on NPP by climatic controls was defined by using an empirical membership function. Results showed that temperature or water availability limited NPP over larger land areas (31% and 52%, respectively) than did radiation limitation (5%). Climatic controls appeared to be important in limiting productivity in most vegetation biomes, except for evergreen broadleaf forests. Nevertheless, there were areas of the globe (12%) where none of the climatic factors appeared to limit NPP. Our research has suggested that other environmental controls, such as nutrient availability or biological constraints, should then be considered. The wide distribution of NPP between zero and the upper boundary values in the correlation plots indicated that multivariate environmental balances, not single limiting factors, controlled biospheric productivity. Received 27 August 1997; accepted 19 November 1997.     

Biotic and Abiotic Controls Over Canopy Function and Structure in Humid Hawaiian Forests

Foliar nitrogen (N) plays a key role in ecosystem function and dynamics, including processes such as photosynthesis, productivity, and decomposition. Aboveground carbon density (ACD Mg C ha^?1) represents a cumulative functional outcome of these and other ecosystem processes and is an important metric for monitoring current carbon stocks. Despite their importance, multiple interacting controls over landscape-level variation in foliar N and ACD are poorly understood. We assessed the relative importance of individual ecologically important state factors (climate, substrate, age, vegetation, and topography) associated with canopy foliar N and ACD throughout a humid forest landscape. We combined high-resolution remotely sensed data, machine learning, and field data to map and assess canopy foliar N and ACD patterns across a 5016-ha forest reserve in Hawai‘i. Distance to non-native forests had the largest relative influence on canopy foliar N concentration, followed by mean annual temperature (MAT), vegetation type, precipitation, soil, canopy height, and substrate age. In contrast, soil type was the strongest determinant of spatial variability in ACD, followed by precipitation, MAT, and vegetation type. Similar to foliar N, climate and vegetation variables were associated with ACD. However, soil type was found to be much more important in the ACD model (30%) than in the foliar N model (4%). Landscape-scale patterns in canopy foliar N and ACD are the result of shifts in vegetation type and composition, most likely due to species’ responses to past disturbances, current climate conditions, and available nutrients. Degradation of native forests and future climate changes could result in highly altered biogeochemical cycles.     

Dietary analysis of Homonota darwini (Squamata:Gekkonidae) in Northern Patagonia

<正> Our study investigated the diet of the southernmost gecko in the world, Homonota darwini. Fifty-three specimenswere captured during spring and summer in four locations in Patagonia, Argentina. The stomach contents of the specimens wereidentified, and we found that prey consisted of six main groups: Coleoptera, Hymenoptera, Homoptera and Araneae, and theadults and larvae of moth Lepidoptera. Lepidoptera was the major dietary component. The presence of ants and moths as commonprey suggests an ambush feeding strategy. In spring, females consumed more ants than males although no other dietary differencesbetween males and females were evident. We found nine geckos with empty stomachs and six parasitized by nematodes.Presence of empty stomachs corroborates previous observations of other nocturnal geckos and non-gecko lizards. Reduced foragingsuccess of nocturnal lizards could be due to difficulty in prey detection due to dim light, reduced or erratic activity of insectprey at night, or shorter activity times of geckos relative to diurnal success. Sex and season were not associated with the incidenceof empty stomachs. Principal component analysis showed that four food alternatives correlated with season. The constraint ofnocturnality, coupled with low night-time temperatures restricting feeding to only a few hours after sunset, appear to have causeda generality of diet which may limit energy acquisition. We conclude that H. darwini is an arthropod generalist and likely an ambushforager, as are many other nocturnal gekkonids     

Spatio-temporal patterns in the copepod community in Malangen, Northern Norway

The objective of this study was to identify the key copepodspecies and their life cycles, and provide evidence for anyseasonal and spatial changes in the copepod community in Malangen,a fjord located 30 km to the south of Tromsø in NorthernNorway (69°30'N, 18°21'E). As a result of high levelsof freshwater run-off in May, the fjord became highly stratifiedwith a sharp pycnocline at 10–30 m depth from May to August.The generation patterns of six copepod species are described.Calanusfinmarchicus produced one generation during the spring thatyear, whereas two generations appeared to be produced by bothPseudocalanus acuspes and P.minutus: one in spring (March-June)and the other in autumn (August-December). However, it is uncertainto what extent P.minutus regularly produces a second generation.Two peaks of CI-CIII Metridia spp. were found; there were differencesalong the length of the fjord in the timing of these, but therelative contributions of M.longa and M.lucens are uncertain.Chiridius armatus CI-CIII peaked in abundance in the spring,which indicates that one main generation was produced at theouter station of the fjord. The copepod community in Malangencould be grouped into three entities according to their numericalabundance during the year one group of highly abundant forms,generally with maxima >50 000 individuals m^–3 (C.finmarchicus,Microcalanus sp., Oithona similis , Oithona spinirostris, Acartiasp. and Pseudocalanus spp.), a second group of less abundantspecies with a clear seasonality in abundance, varying from500 to 50 000 individuals m^–3 (M.longa, M.lucens, Calanushyperboreus, Carmatus, Tenwra longicornis, Oncaea sp., Euchaetanorvegica and Scolecithrwella minor), and a third group of 14holoplanktonic species, sporadically occurring in the fjord.The study demonstrates clear gradients in the abundance of fivespecies along the length of the fjord: the recruiting generationof C.finmarchicus occurred in higher abundances at the outerstation in May and June compared to the other inner sites. Laterin the season, the reverse situation appeared, in which thepopulation was more abundant in the inner part of the fjorcCalanw hyperboreus increased abruptly in abundance from lowwinter levels to a maximum in April-May, and declined steadilyduring the season (except at the innermost station). Metridialucens, M.longa and C.armatus demonstrated different distributionpatterns in Malangen that matched their preferred areas of distribution.Both M.lucens and C.armatus are known as oceanic and deep-waterspecies, respectively, and these were prevalent at the two outersites in Malangen. Metridia longa is a more nentic species andwas found in highest numbers at the two innermost sites. Themechanisms for the differences in abundance among these specieswithin the fjord are discussed.     

A Meta-analysis of Climatic and Chemical Controls on Leaf Litter Decay Rates in Tropical Forests

Although tropical forests occupy a small fraction of the earth’s total land area, they play a disproportionately large role in regulating the global carbon cycle. Yet controls on both primary productivity and decomposition in tropical forests are not well-studied in comparison with temperate forests and grasslands, despite their extreme biogeochemical heterogeneity. To evaluate the relative importance of climate and foliar chemical variables in driving decomposition in tropical forests, I performed a meta-analysis of reported leaf litter decay rates throughout tropical forest ecosystems. Using a model selection procedure based on Akaike’s Information Criterion, I found that temperature and precipitation played little direct role in regulating decomposition rates, except in montane forests where cool temperatures slowed decay. Foliar concentrations of calcium, magnesium, nitrogen, phosphorus, and potassium were important predictors of mass loss rates, although each of these factors explained a very small amount of variance when considered in isolation. The large amount of unexplained variation in decomposition rates observed both within and across tropical forest sites may be due to other factors not explored here, such as soil biota or complex plant secondary chemistry. Carbon cycling in tropical forests seems to be modulated by the availability of multiple nutrients, underscoring the need for additional manipulative experiments to explore patterns of belowground nutrient limitation across the biome. Because models of decomposition developed in temperate ecosystems do not appear to be generalizable to wet tropical forests, new biogeochemical paradigms should be developed to accommodate their unique combination of climatic, edaphic, and biotic factors.     

Patterns of use and damage by exotic deer on native plant communities in northwestern Patagonia

Ungulate overabundance can strongly alter composition and structure of forest communities through selective damage independently of the herbivory history of the recipient system. In the early 1900s, red and fallow deer (Cervus elaphus and Dama dama, respectively) were introduced to northwestern Patagonia. We studied patterns of relative habitat use, damage, and species selection by introduced deer populations in three major plant communities that have the longest history of invasion in the region. We also evaluated community structure and composition characteristics as possible explanatory factors for the observed patterns of browsing, fraying, and bark-stripping. At the species level, exotic deer browsed more than expected on two evergreen species (Austrocedrus chilensis and Schinus patagonicus) and two spiny species (Colletia hystrix and Dasyphyllum diacanthoides), while one dominant shrubland tree (Lomatia hirsuta) was selected for fraying and bark-stripping. Browsing was the more widespread damage in all plant communities, while fraying and bark-stripping occurred at low incidence. Furthermore, species identity was found as the main driver of deer damage over plant community type. Finally, variation in damage and in habitat use was explained by community structure and composition characteristics. Bark-stripping and fraying are best predicted by community composition, whereas browsing and habitat use are best predicted by structural properties including understory cover, cover of fallen logs, and tree density. The patterns of damage and the association with community structure characteristics reported here provide insight for developing management strategies.     

Macroecological Patterns of Climatic Niche Breadth Variation in Lacertid Lizards

Measuring climatic niche position and breadth may help to determine where species can occur over space and time. Using GIS-based and phylogenetic comparative methods, we investigated global patterns of variation in climatic niche breadth in lacertid lizards to test the following three hypotheses about climatic niche widths. First, does a species' temperature or precipitation niche breadth relate to its temperature or precipitation niche position(the mean value of annual mean temperature or annual precipitation across sampled localities in the range of each species)? Second, are there trade-offs between a species' temperature niche breadth and precipitation niche breadth? Third, does a species' temperature or precipitation niche breadth relate to altitude or latitude? We expect that:(1) species distributed in cold regions are specialized for low-temperature environments(i.e. narrow niche breadth center around low temperatures);(2) a negative relationship between species niche breadth on temperature and precipitation axes according to the tradeoff hypothesis(i.e. species that tolerate a broad range of precipitation regimes cannot also tolerate a broad range of temperatures);(3) precipitation niche breadth decreases with altitude or latitude, whereas temperature climatic niche breadth increases with altitude or latitude. Based on the analytical results we found that:(1) temperature niche breadth and position are negatively related, while precipitation niche breadth and position are positively related;(2) there is no trade-off between temperature and precipitation niche breadths; and (3) temperature niche breadth and latitude/altitude are positively related, but precipitation niche breadth and latitude/altitude are not significantly related. Our results show many similarities with previous studies on climatic niche widths reported for amphibians and lizards, which provide further evidence that such macroecological patterns of variation in climatic niche breadths may be widespread.     

Tree-ring records from Nothofagus dombeyi: A preliminary chronology network in Northern Patagonia,Argentina

Most of the dendrochronological efforts in northern Patagonia have been invested in long-lived conifer species, whereas several broadleaf species have received less attention. This is the case for Nothofagus dombeyi, a dominant species in the mesic temperate and rainforests in the region. The aim of this study was to develop the first tree-ring chronologies for N. dombeyi in northern Patagonian and contribute to the future dendroecological and dendroclimatological studies in the region. Using standard dendrochronological techniques, six tree-ring-width chronologies were obtained encompassing the east–west precipitation gradient of this species in the Argentinean sector of the northern Patagonian Andes. Chronology statistics indicated that N. dombeyi records are highly reliable and a good source of information on tree-growth variability in the region. Stands located in the xeric sectors of the gradient showed higher inter-site variability. Also, results presented here showed that N. dombeyi has a large potential for the study of climatic variability in northern Patagonia.     

Forest Structure Affects the Stoichiometry of Periphyton Primary Producers in Mountain Streams of Northern Patagonia

Riparian zones are major components of stream ecosystems that influence the physical, chemical, and biological parameters. In particular, the distribution of vertical foliage and the structure of riparian vegetation determine light availability in canopied streams. Here, we analyzed how forest structure will modify light availability and thus affect primary producers’ photosynthetic parameters and the periphyton stoichiometry of mountain streams. We carried out field sampling in four streams with different canopies located in the North-Patagonian Andes and conducted a field experiment in which light conditions were manipulated for four months. Then, we linked our results to qualitative climate change scenarios for North-Patagonian forest predicting how future climate change will affect primary producers and periphyton stoichiometry in low-order streams through modifications in the structure of canopied zones. Finally, we found that biomass, photosynthetic parameters and the elemental content of periphyton exhibited a bell-shaped relationship with light availability which was, in turn, dependent on canopy cover. These trends are characterized by an increase from low light up to 250 μmol m^?2 s^?1 and a decline when light is over 750 μmol m^?2 s^?1. Thus, intermediate light resulted in optimal conditions for primary producers’ photosynthesis; however, these intermediate canopied zones are predicted to decrease in the future. Therefore, we predict changes in stream ecosystem stoichiometry due to variations in primary producers’ photosynthesis, and, consequently, periphyton elemental composition as an outcome of forest structure modifications due to climate change.     

Volcanic and environmental impacts on subfossil chironomids from Northern Patagonia (Argentina) over the last 700 years

Limnology - Southern South America, especially Patagonia, presents numerous glacial lakes holding proxies of past environmental and climate changes. This is useful to reconstruct past environmental...     

Co-occurrence Patterns in Carnivorans: Correspondence Between Morphological and Ecological Characteristics of an Assemblage of Carnivorans in Patagonia

We searched for correspondence between morphology and trophic habits in an assemblage of six species of coexisting carnivorans from Patagonia to confirm the predictive power of the study of the trophic morphology as an approach to the study of resource partitioning, which is often utilized in paleontological studies. The six species were assigned to four morphoguilds and to four trophic guilds, although the species composition of both spaces was only coincident during one of the two studied time periods. The most obvious explanation for this lack of correspondence is based on the assumption that species can change from one ecological guild to another, while their relative positions in the morphospace will be fixed. Therefore, the observed lack of correspondence could be searched in the context of differences between the ecological and evolutionary scales. Although morphological specialization toward some type of diet has been corroborated in our assemblage, the inference of interactions in ecological time among species from the past from its morphology must be considered with caution.