Habitat Mosaic, Wildlife Availability, and Hunting in the Tropical Forest of Calakmul, Mexico

Abstract: Habitat loss and subsistence hunting are two of the main activities that affect wildlife in frontier areas. We compared subsistence hunting patterns in four villages with different ethnic composition and degree of habitat disturbance in the vicinity of Calakmul Biosphere Reserve, Campeche, Mexico. We also compared differences between some of these villages in harvest composition and prey availability to determine hunting preferences. We used a Landsat TM satellite image to analyze the degree of disturbance around the villages. We conducted periodic surveys of subsistence hunting and prey availability. Wildlife availability was assessed monthly on nine transects (3000 m) established in the vicinity of three villages. The relative amount of disturbed habitat was smaller in an indigenous Maya village ( IV ) and larger in a mestizo village ( MV ). The two mixed-composition villages ( MCVs) had intermediate levels of disturbance. Ten species, four large and six small, of birds and mammals accounted for 97% of the hunting records. Hunting was more intense in IV and less intense in MCV1. The three village types had different hunting preferences. The habitat-mosaic composition in the vicinity of the villages influenced prey availability and subsistence-hunting preferences. Changes in the habitat mosaic were caused by the size of the holding and by ethnic composition. In spite of longer settlement time, the habitat mosaic in the vicinity of IV was less transformed than that of the other sites. Their larger holding size and greater diversity of economic activities may explain why the Mayas at IV have transformed the landscape less than the other groups and can hunt more and larger prey.     

Population Declines, Viable Breeding Areas, and Management Options for Flamingos in Southern Africa

Habitat rehabilitation or intervention to prevent species declines are rarely employed in Africa. I argue that despite protection in national parks, active intervention is necessary to halt declines in southern Africa's Greater ( Phoenicopterus ruber ) and Lesser ( Phoeniconaias minor ) Flamingo populations. Flamingos are long-lived species that breed sporadically at only two localities in southern Africa: the Makgadikgadi Pans in Botswana and Etosha National Park in Namibia. Despite well-publicized breeding on Etosha Pan, flamingos have experienced only three major breeding events in 40 years. Breeding failure occurs when high evaporation rates rapidly dry the pan, and up to 100,000 flightless chicks may starve. Consequently, pairs breeding in Etosha exhibit extraordinarily low recruitment (0.040 young pair/year) and extrapolations indicate that adults can replace themselves only if they breed for 38 to 50 years and all offspring survive. Because survival of offspring from fledging to adulthood (5 years) is about 46%, this breeding lifespan rises to an unrealistic 83 years, making Etosha a nonviable breeding site. Alternative, suitable flamingo habitats in Africa are being mined for soda-ash, are damaged by pollution, or are unprotected. Accordingly, continent-wide estimates and those from southern Africa alone suggest a population decline of about 40% in both species over the last 15 years. Because Namibia regularly supports 84% of the Greater and 93% of the Lesser Flamingos in southern Africa, conservation strategies are best focused there. Simple but effective management methods, based on those employed in western Europe, could reverse these downward trends. In Etosha a small island surrounded by a water-filled depression would allow up to 4000 pairs to breed annually. The benefits of enhancing the breeding of flamingos in Etosha include research opportunities, tourism revenue, and a safe haven for two Red Data species.     

Laboratory and field estimates of the rate of faecal pellet production by Antarctic krill,Euphausia superba

The time course of faecal pellet production (egestion) was monitored in January 1985 for a population of Antarctic krill, Euphausia superba Dana, maintained in flowing seawater aquaria at Palmer Station, Antarctica. Following transfer to filtered seawater, krill produced faecal strings for roughly 40 min, after which time faecal egestion virtually ceased. Similar results were obtained for freshly-trawled krill at sea in February and March 1985. There were wide daily variations in total faecal egestion rate; mean rates varied from 0.54 to 1.66 mg dry wt h^-1 and individual rates from 0.25 to 2.35 mg h^-1 (all data corrected to a standard krill of 600 mg fresh weight). Despite these wide fluctuations in total faecal egestion, the loss of organic matter showed no significant daily variation, with a mean value of 0.13 mgh^-1. The relationship between faecal egestion rate and faecal organic content suggested that feeding rate was governed by food quality; when inorganic load was high, feeding rate increased to ensure sufficient energy intake. The data suggest that superfluous feeding does not occur in krill and that values of gut-clearance time calculated from time intervals greater than about 40 min will not be representative of previous feeding history. the rates of faecal egestion observed in this study indicate that the flux of faecal pellets from krill is substantial. They imply an energy intake in E. superba of 17 to 28% body weight per day, much higher than estimated previously for this species by summing known energy losses, but similar to estimates for other euphausiids.     

Vaquita Bycatch in Mexico's Artisanal Gillnet Fisheries: Driving a Small Population to Extinction

Abstract: The world's most endangered marine cetacean, the vaquita (   Phocoena sinus ), continues to be caught in small-mesh gillnet fisheries throughout much of its range. We monitored fishing effort and incidental vaquita mortality in the upper Gulf of California, Mexico, from January 1993 to January 1995 to study the magnitude and causes of the incidental take. Of those factors studied, including net mesh size, soaktime, and geographic area, none contributed significantly to the incidental mortality rate of the vaquita, implying that the principal cause of mortality is fishing with gillnets per se . The total estimated incidental mortality caused by the fleet of El Golfo de Santa Clara was 39 vaquitas per year (95% CI = 14, 93), over 17% of the most recent estimate of population size. El Golfo de Santa Clara is one of three main ports that support gillnet fisheries throughout the range of the vaquita. Preliminary results indicate that fishing effort for San Felipe, Baja California, is comparable to that of El Golfo de Santa Clara, suggesting that this estimate of incidental mortality of vaquitas represents a minimum. We strongly recommend a complete and permanent ban on gillnets in the area. Alternative or supplemental mitigation strategies include (1) a maximum annual allowable mortality limit of vaquitas; (2) mandatory observer coverage of all boats fishing within the Upper Gulf of California and Colorado River Delta Biosphere Reserve; (3) extension of the Upper Gulf of California and Colorado River Delta Biosphere Reserve to encompass all known vaquita habitat; (4) rigorous enforcement of new and existing regulations; and (5) development of alternative sources of income for gillnet fishers.     

Wildlife Loss through Domestication: the Case of Endangered Key Deer

Abstract:  Wildlife extinction represents the ultimate failure of wildlife conservation. It has many causes, some of them natural, but is increasingly tied to anthropogenic factors. Wildlife loss via domestication, however, is rarely considered. We evaluated the potential for inadvertent domestication of wildlife by determining the effect of feeding and watering on Key deer ( Odocoileus virginianus clavium ) density, group size, and distribution. Key deer sightings were significantly higher in areas (42 ha) surrounding the households that provided food and water (0.18 deer/m;  n = 8   ) than in randomly selected areas (0.03 deer/m;  t = 3.82, 14  df, p = 0.002   ). Average distance to a household providing food and water decreased logistically as group size increased, and large groups (>2 individuals each) were observed more frequently in areas where food and water were provided (27.5%) than in the randomly selected areas (7.5%). The incidence of large groups outside feeding areas (7.5%), however, was similar to the incidence of large groups during early urbanization (5.1%; 1968–1973). Our results suggest illegal feeding caused changes in density, group size, and distribution indicative of domestication. Because fresh water and food were primary selective pressures for Key deer before illegal feeding and watering, genetic changes may occur in the future. For those who value "wildness" in wildlife, domestication of wildlife species is a serious problem that must be addressed.     

Cougar Dispersal Patterns, Metapopulation Dynamics, and Conservation

Abstract: We examined cougar (   Puma concolor ) dispersal, emigration, and immigration in the San Andres Mountains, New Mexico, from 1985 to 1995 to quantify the effects of dispersal on the local population and surrounding subpopulations. We captured, tagged, and radio-collared animals to detect the arrival of new immigrants and dispersal characteristics of progeny. We found that cougars in southern New Mexico exhibited a metapopulation structure in which cougar subpopulations were separated by expanses of noncougar habitat and linked by dispersers. Of 43 progeny (n = 20 males , 23 females ) studied after independence, only 13 females exhibited philopatric behavior. Males dispersed significantly farther than females, were more likely to traverse large expanses of noncougar habitat, and were probably most responsible for nuclear gene flow between habitat patches. We estimated that an average of 8.5 progeny (i.e., cougars born in the study area) successfully emigrated from and 4.3 cougars successfully immigrated to the San Andres Mountains each year. Concurrently, an average of 4.1 progeny were recruited into the San Andres cougar population. Protected cougar subpopulations can contribute to metapopulation persistence by supplying immigrants to surrounding subpopulations that are affected by fragmentation or offtake by humans. Cougar population dynamics and dispersal behavior dictate that cougar management and conservation should be considered on a regional scale.     

Fire Regime Changes in La Michilía Biosphere Reserve, Durango, Mexico

Abstract: The ability of reserves to maintain natural ecosystem processes such as fire disturbance regimes is central to long-term conservation. Fire-scarred tree samples were used to reconstruct fire regimes at five study sites totaling approximately 230 ha in pine (   Pinus spp.) and oak ( Quercus spp.) forests of La Michilía Biosphere Reserve on the dry east slope of the Sierra Madre Occidental, Durango, Mexico. Study sites covered a 20-km environmental gradient of elevation, topography, and human land uses. Plant communities ranged from oak-pine to mixed conifer forests. Fires were frequent at all sites prior to 1930, when large-scale grazing of domestic livestock was initiated. Widespread fires have been excluded from four of the five sites since 1945, with an essentially uninterrupted regime of frequent fires continuing only in the reserve core. Xeric sites had many, smaller fires, whereas mesic sites had fewer but larger fires. On a reserve-wide scale, a fire burned on at least one site nearly every year, usually in the dry spring or early summer season, but fire years were rarely synchronous among the sites. Fire occurrence was weakly related to the Southern Oscillation climate pattern; major reserve-wide fire years almost never coincided with wet Southern Oscillation extremes but only occasionally matched dry extremes. Maintenance of the long-term frequent-fire regime in the reserve core is one indicator that the biosphere reserve model has been successful in conserving natural processes, but the protected area is small ( 7000 ha). Because of the key role of frequent-fire regimes in regulating ecosystem structure and function, restoration of the ecological role of fire disturbance is a desirable conservation strategy.     

Linking movement, diving, and habitat to foraging success in a large marine predator

Establishing where and when predators forage is essential to understanding trophic interactions, yet foraging behavior remains poorly understood in large marine carnivores. We investigated the factors leading to foraging success in gray seals (Halichoerus grypus) in the Northwest Atlantic in the first study to use simultaneous deployments of satellite transmitters, time depth recorders, and stomach-temperature loggers on a free-ranging marine mammal. Thirty-two seals were each fitted with the three types of instrumentation; however, complete records from all three instruments were obtained from only 13 individuals, underscoring the difficulty of such a multi-instrument approach. Our goal was to determine the characteristics of diving, habitat, and movement that predict feeding. We linked diving behavior to foraging success at two temporal scales: trips (days) and bouts (hours) to test models of optimal diving, which indicate that feeding can be predicted by time spent at the bottom of a dive. Using an information-theoretic approach, a Generalized Linear Mixed Model with trip duration and accumulated bottom time per day best explained the number of feeding events per trip, whereas the best predictor of the number of feeding events per bout was accumulated bottom time. We then tested whether characteristics of movement were predictive of feeding. Significant predictors of the number of feeding events per trip were angular variance (i.e., path tortuosity) and distance traveled per day. Finally, we integrated measures of diving, movement, and habitat at four temporal scales to determine overall predictors of feeding. At the 3-h scale, mean bottom time and distance traveled were the most important predictors of feeding frequency, whereas at the 6-h and 24-h time scales, distance traveled alone was most important. Bathymetry was the most significant predictor of feeding at the 12-h interval, with feeding more likely to occur at deeper depths. Our findings indicate that several factors predict feeding in gray seals, but predictor variables differ across temporal scales such that environmental variation becomes important at some scales and not others. Overall, our results illustrate the value of simultaneously recording and integrating multiple types of information to better understand the circumstances leading to foraging success.     

Behavioral games involving a clever prey avoiding a clever predator: An individual-based model of dusky dolphins and killer whales

Faced with an intermittent but potent threat, animals exhibit behavior that allows them to balance foraging needs and avoid predators and over time, these behaviors can become hard-wired adaptations with both species trying to maximize their own fitness. In systems where both predator and prey share similar sensory modalities and cognitive abilities, such as with marine mammals, the dynamic nature of predator-prey interactions is poorly understood. The costs and benefits of these anti-predator adaptations need to be evaluated and quantified based on the dynamic engagement of predator and prey. Many theoretic models have addressed the complexity of predator-prey relationships, but few have translated into testable mechanistic models. In this study, we developed a spatially-explicit, geo-referenced, individual-based model of a prototypical adult dusky dolphin off Kaikoura, New Zealand facing a more powerful, yet infrequent predator, the killer whale. We were interested in two primary objectives, (1) to capture the varying behavioral game between a clever prey and clever predator based on our current understanding of the Kaikoura system, (2) to compare evolutionary costs vs. benefits (foraging time and number of predator encounters) for an adult non-maternal dusky dolphin at various levels of killer whale-avoidance behaviors and no avoidance rules. We conducted Monte Carlo simulations to address model performance and parametric uncertainty. Mantel tests revealed an 88% correlation (426 × 426 distance matrix, km²) between observed field sightings of dusky dolphins with model generated sightings for non-maternal adult dusky dolphin groups. Simulation results indicated that dusky dolphins incur a 2.7% loss in feeding time by evolving the anti-predator behavior of moving to and from the feeding grounds. Further, each evolutionary strategy we explored resulted in dolphins incurring an additional loss of foraging time. At low killer whale densities (appearing less than once every 3 days), each evolutionary strategy simulated converged towards the evolutionary cost of foraging, that is, the loss in foraging time approached the 2.7% loss experienced by evolving near shore-offshore movement behavior. However, the highest level of killer whale presence resulted in 38% decreases in foraging time. The biological significance of these losses potentially incurred by a dusky dolphin is dependent on various factors from dolphin group foraging behavior and individual energy needs to dolphin prey availability and behavior.     

Are anthropogenic factors affecting nesting habitat of sea turtles? The case of Kanzul beach,Riviera Maya-Tulum (Mexico)

Marine coast modification and human pressure affects many species, including sea turtles. In order to study nine anthropogenic impacts that might affect nesting selection of females, incubation and hatching survival of loggerhead (Caretta caretta) and green turtle (Chelonia mydas), building structures were identified along a 5.2 km beach in Kanzul (Mexico). A high number of hotels and houses (88; 818 rooms), with an average density of 16.6 buildings per kilometer were found. These buildings form a barrier which prevents reaching the beach from inland, resulting in habitat fragmentation. Main pressures were detected during nesting selection (14.19% of turtle nesting attempts interrupted), and low impact were found during incubation (0.77%) and hatching (4.7%). There were three impacts defined as high: beach furniture that blocks out the movement of hatchlings or females, direct pressure by tourists, and artificial beachfront lighting that can potentially mislead hatchlings or females. High impacted areas showed lowest values in nesting selection and hatching success. Based on our results, we suggest management strategies to need to be implemented to reduce human pressure and to avoid nesting habitat loss of loggerhead and green turtle in Kanzul, Mexico.     

Effects of feeding rate on conversion efficiency and chemical composition of the fish Tilapia mossambica

Average daily rations of 14, 35 or 58 mg Tubifex tubifex worm per gram of the fish Tilapia mossambica Peters represent maintenance, optimum or maximum feeding levels. At these levels, conversion efficiency (K ₁) is 5,9 or 24%. An amount of 65 mg worm/g fish/day, when fed under experimental conditions, is converted with the poorest conversion efficiency (4%). Test individuals fed at 11 to 49 mg worm/g fish/day show a decreasing trend in water content (78.1 to 74.8%), and an increasing trend in fat content (32.1 to 44.2%). Below or above this feeding rate range, water content increases, while fat content decreases. The range of individual variations in fat content is nearly 3 times greater than that of ash and 15 times greater than that of water. Test individuals starved for 60 days lose 2.1 mg dry body weight/g/day. This loss is contributed by calorifically equivalent amounts of fat and protein. The endogenous loss of nitrogen by these individuals averaged 0.18 mg N/g body weight/day.     

Land change in the southern Yucatán and Calakmul biosphere reserve: effects on habitat and biodiversity.

The southern Yucatán contains the largest expanse of seasonal tropical forests remaining in Mexico, forming an ecocline between the drier north of the peninsula and the humid Petén, Guatemala. The Calakmul Biosphere Reserve resides in the center of this region as part of the Mesoamerican Biological Corridor. The reserve's functions are examined in regard to land changes throughout the region, generated over the last 40 years by increasing settlement and the expansion and intensification of agriculture. These changes are documented from 1987/1988 to 2000, and their implications regarding the capacity of the reserve to protect the ecocline, forest habitats, and butterfly diversity are addressed. The results indicate that the current landscape matrix serves the biotic diversity of the reserve, with several looming caveats involving the loss of humid forests and the interruption of biota flow across the ecocline, and the amount and proximity of older forest patches beyond the reserve. The highly dynamic land cover changes underway in this economic frontier warrant an adaptive management approach that monitors the major changes underway in mature forest types, while the paucity of systematic ecological and environment-development studies is rectified in order to inform policy and practice.     

Mammal Diversity and Conservation in the Selva Lacandona, Chiapas, Mexico

The Selva Lacandona region of Chiapas, Mexico, has high biodiversity, represents the last large portion of tropical rainforest in México, and faces imminent destruction. Through fieldwork and literature searches I found a total of 112 mammal species (including 17 Middle-American endemics) on the Lacandona's 331,200 ha Montes Azules Biosphere Reserve. This inventory plus those from eight additional Neotropical localities show local mammal species richness in the Neotropics to be in the range of 70–116 species. Richness is primarily correlated with the amount of annual rainfall, but within rainforest areas species richness is probably not correlated with rainfall, latitude, altitude, or area size. Rather, above a certain limit of rainfall and below a critical level of latitude and altitude, mammal species richness seem to reach an asymptotic maximum. Areas covered with tropical rainforest and with a well-known, relatively intact fauna have about 112–116 mammal species. In the Montes Azules Reserve most mammals (57%) are bats. The most heavily occupied feeding guilds are frugivores/herbivores and insectivores/omnivores. Large species and carnivores appear most vulnerable to local extinction. Montes Azules (and thus the Selva Lacandona) is especially noteworthy because (1) it contains a greater proportion of species facing conservation problems than expected from a random draw of Mexican mammals; (2) it is probably the most diverse ecosystem in Mexico; (3) many species sustain their only Mexican populations in this area; and (4) it is the largest remnant of tropical rainforest in Mexico and is part of the largest expanse of that vegetation type in Central America.     

Variance and Uncertainty in the Expected Number of Occurrences in Reserve Selection

Abstract:  Reserve selection often concerns the design of reserve networks for the long-term maintenance of biodiversity. We considered uncertainty in the context of three common reserve-selection formulations, the expected number of populations, proportional coverage of land-cover types, and the probability of having at least one population. By uncertainty, we mean variance in the outcome of any probability-based reserve selection formulation. A typical reserve-selection formulation might ask for the least expensive set of sites that contains n populations per species. It is implicit here that this requirement concerns the expected number of populations, which actually is obtained only with a 50% chance. If the requirement is changed to select the least expensive set of sites that gives n populations per species with a 95% probability, the number of sites required in the solution increases and the identity of the sites is changed toward sites that have high probabilities of persistence (or occurrence) and low associated binomial variance. Anthropogenic threat is one factor that may cause probabilistic uncertainty in the context of proportional area coverage.     

上海市免费公园中老年游客行为及满意度特征调查

中老年游客是免费公园游客人群的主要群体,以上海市27座免费公园为例,分析中老年两年龄段游客行为特征,以及其对公园设施服务的重要性和满意度。结果表明:中年游客具有择园路程范围广,公共交通利用率高,来园频率低,入园时间晚,喜爱亲子活动,停留时间短等特征;而老年游客则表现出偏爱短距离公园,以步行为主,来园频率高,入园时间早,倾向运动健身,停留时间长等特征。两年龄段游客对公园满意度评价总体相近,均认为绿化、卫生状况和安全性,以及景点、厕所和无障碍设施设置是影响游客来园的关键因子,前3项令游客满意,而后3项却达不到期望。针对两年龄段游客不同的行为和满意度特征,对免费公园的经营管理提出建议。     

Energy substrates for eggs and prefeeding larvae of the dolphinCoryphaena hippurus

Changes in the chemical composition of developing dolphin (Coryphaena hippurus) eggs and prefeeding yolksac larvae were determined in order to estimate probable dietary requirements of first-feeding larvae. Daily dry matter, protein nitrogen (PN), non-protein nitrogen (NPN), lipid, gross energy content, fatty acid and amino acid profiles from Day 1 to Day 2 eggs and Day 1 to Day 3 larvae were compared. Lipid was the primary endogenous energy source accounting for the daily caloric deficit through both the egg and larval stages, except over the day of hatching. The catabolism of lipid by embryos (0.078 cal d^–1) was greater than that by yolksac larvae (0.036 cal d^–1). The higher demand for energy by embryos was related to a greater rate of protein synthesis during the egg stage. The ratio of PN:NPN increased during egg development without change in total nitrogen content, but was constant throughout the yolksac larvae period. The lipid content per embryo did not decrease over the hatching period (Day 2 to 3, postspawning). However, there was a loss in amino acid content not totally accounted for by sloughing of the chorion at hatching. This loss, as protein, accounted for 0.053 cal of gross energy, which represented 70% of the total estimated energy needs of the fish over this period. Loss of non-essential amino acids (25%) was higher than that of essential amino acids (13%). Proline and tyrosine accounted for 32% of the total loss of amino acids at this time. The only preferential use of fatty acids over any period was a small but significant drop in the content of C22:6n-3 prior to the onset of feeding (Day 5, postspawning). It is speculated that the pattern of energy-substrate use of first-feeding dolphin larvae will reflect the pattern of endogenous energy use during the egg and prefeeding yolksac larval stages. Diets or feeding regimens with lipid as the primary energy source, and containing a fatty acid profile similar to that of eggs or yolksac larvae, should be useful in culturing this species, at least during the early feeding stages.     

Thalassia testudinum productivity and grazing by green turtles in a highly disturbed seagrass bed

There has been an historical decline in the seagrass beds in Maho and Francis Bays, St. John, U.S. Virgin Islands: presently (1986) there are only five small seagrass beds in shallows water. These seagrass beds are highly disturbed by heavy boat usage and are intensively grazed by the green turtle Chelonia mydas L. Fifteen to 50 boats anchor each night in the bays: anchor scars cause a loss of up to 6.5 m² d^-1 or 1.8% yr^-1 of the seagrass beds. Seagrasses regrew into such scars only minimally within a period of 7 mo. The size of the green turtle population was estimated at 50 subadults and their feeding behavior was determined by direct observation and radiotelemetry. The behavior of the green turtles differed from other observations published on the species. Here, the turtles grazed all available Thalassia testudinum, their preferred seagrass food, rather than creating discrete grazing scars, and spent all their waking hours (9 h per day) feeding. Areal productivity of T. testudinum leaves (33 to 97 mg dry wt m^-2d^-1) in the bays was at least an order of magnitude lower than published values or than the productivity of another, lessdisturbed seagrass bed on St. John, despite having comparable leaf-shoot density. Leaf shoots were stunted, fragile, achlorotic, and had only two leaves as opposed to the five leaves per shoot more typically seen. The green turtle population was near the estimated carrying capacity of T. testudinum, based on the standing crop and productivity of T. testudinum and the grazing rate of the turtles. The effect of disturbance of T. testudinum from boats and turtles was assessed by excluding these with emergent fences. Within 3 mo of protection, the areal and shoot-specific productivity of T. testudinum leaves as well as leaf size increased significantly compared to unprotected areas. Conservation efforts are recommended in Maho Bays and Francis because seagrass productivity is low, disturbance rates are higher than recovery rates, the turtles cannot increase further their feeding rate in order to compensate for such factors, and there are few alternate sources of T. testudinum on the north shore of St. John.Contribution No. 175 from West Indies Laboratory, Teague Bay, Christiansted, St. Croix, U.S. Virgin Islands 00820, USA     

Avifaunal Use of Wooded Streets in an Urban Landscape

Abstract: Birds in urban landscapes primarily occupy parks (  forest fragments), wooded streets ( linear strips connecting fragments), or the urban matrix. I studied the effects of street location in the landscape, vegetation structure, and human disturbance ( pedestrian and automobile load) within wooded streets on bird species richness, temporal persistence, and density of feeding and nesting guilds, and on the probability of street occupation by individual species in Madrid during two consecutive breeding seasons. The number of species recorded increased from the least suitable (control streets without vegetation) to the most suitable habitats (urban parks), with wooded streets being intermediate landscape elements. Fourteen species, belonging to four of the eight guilds identified in this system, were recorded in wooded streets in both years. Streets that connected urban parks, along with vegetation structure, positively influenced the number of species within wooded streets, species persistence, guild density, and probability of occupation of streets by individual species. Human disturbance exerted a negative influence on the same variables. Wooded streets potentially could function as corridors, allowing certain species—particularly those feeding on the ground and breeding in trees or tree holes—to fare well by supporting alternative habitat for feeding and nesting. Local improvements in corridor quality, through increased vegetation complexity and reduced human disturbance, could exert a positive influence on the regional connectivity of the system. Because of differential use of corridors by species with different habitat requirements, however, corridor implementation should also take into account the target species of management.     

神农架林区不同类型植物的叶片特征与光合性能研究

以神农架林区木鱼镇茶山上生长的8种不同类型植物为试验材料,于晴天选择其植株上东南朝向的顶部成长叶,采用LI-COR6400便携式光合测定系统、调制叶绿素荧光成像系统(IMAGING-PAM M-Series)及双通道PAM-100测量系统(Dual-PAM-100)和常规方法研究了其叶片特征、光合性能及相互间的关系,将有助于了解神农架植物的光合生产力及其植被管理。结果表明,不同类型植物叶片的叶片特征和光合性能存在明显的物种差异。比叶重(SLW)为乔木灌木草本;气孔参数以气孔导度(Cond)差异最大;草本植物的光合能力明显高于灌木和乔木,而灌木和乔木间的差异不大;叶绿素含量(Chl)及其组分的差异较小,类胡萝卜素(Car)和花青素含量(Ant)及其与Chl的比值差异极大。不同类型植物叶片特征和光合性能指标的变异系数在7.3%～73.0%间,Chla/Chlb最小,Car/Ant最大;Chla/Chlb、基于叶温的蒸汽压亏缺(VpdL)和胞间CO2浓度(Ci)小于15%,Cond、单位鲜重Car、PSII实际量子产量和PSI非光化学能量耗散的量子产量为40%～50%,单位干重Car、Ant、Chl/Ant和Car/Ant则大于60%,其他指标在20%～40%。相关分析显示,Pn受Cond、叶片含水量和单位干重Chl的正向调控,Ant和Car对Pn无决定性作用;PSII和PSI的实际量子产量依赖于Ci和Chl,Car过高导致其降低;PSI的光保护受SLW的负调控及单位鲜重Chl和单位干重Car的正调控;光合机构的光损伤受Ci的负调控和Chl/Car的正调控。