The interrelationship between productivity,plant species richness and livestock diet: a question of scale?

Question: What relationship exists between productivity, plant species richness and livestock diet? Are the results dependent on scale? Location: A sheep‐grazed Koelerio‐Corynephoretea sandy habitat of the northern upper Rhine (Germany) as a low productivity model system. Methods: The investigation was carried out for three years at a fine scale (2 m²) and for two years at a broad scale (79 m²). Productivity was measured by means of weighed above‐ground phytomass for fine scale and colour‐infrared (CIR) aerial photographs of the same system for fine and broad scales. For both scales, total numbers of vascular plant species and numbers of endangered vascular plant species were extracted from current vegetation relevés. Additionally, we obtained data on livestock diet (grazed phytomass, crude protein content). Results: Statistical analyses show an influence of the year on all variables; relationships between variables are not significant in every year. Species richness and number of endangered species are negatively related to productivity at fine scale while crude protein content and grazed phytomass are positively related to productivity. At the broad scale the diversity‐productivity relationship shows a ‘hump’ with highest species numbers in middle pioneer stages; numbers of endangered species are highest in all pioneer stages. Conclusions: We found a strong impact of scale and year on the diversity‐productivity relationship. It is inappropriate to analyse only small plots (2 m²), and it is necessary to study different years. This vegetation complex is dependent on grazing impact; thus there is an inversely proportional relationship between nature conservation value (high diversity) and livestock nutrition.     

Conifer Cover Increase in the Greater Yellowstone Ecosystem: Frequency,Rates, and Spatial Variation

Extensive fires in recent decades in the Greater Yellowstone Ecosystem (GYE) garnered much attention for causing a significant decrease in the extent of conifer forest cover. Meanwhile, conifer forests in unburned parts of the GYE have continued to increase in extent and density. Conifer cover increase has been well documented by repeat historical photography, but the average rate of increase and the spatial variation remain unquantified. We examined changes in conifer cover across biophysical gradients in the GYE based on stratified random samples from aerial photographs. The percent conifer cover for samples in 1971 and 1999 was quantified to determine the frequency and rate of conifer cover change. A slight majority of samples (56%) showed no change, whereas increases (22%) were balanced by decreases (22%). However, among samples that were not recently burned or logged, or already closed-canopy, nearly 40% increased in conifer cover, at an average annual rate of 0.22%. We quantified significant variability in the frequency and rate of conifer cover increase across gradients of elevation, aspect, vegetation type, and proximity to nearby conifer forest. The most dynamic locations were low density conifer woodlands on northerly aspects at lower elevations, with average annual rates of increase up to 0.51%. This study is significant because it demonstrates that rates of conifer cover increase vary across biophysical gradients, an important consideration for management of dynamic forest ecosystems. Improved understanding of this variability helps us to better understand what factors ultimately cause conifer cover increase. It is also a critical step towards accurate quantification of the magnitude of carbon uptake by conifer cover increase.     

Environmental dependence of population dynamics and height growth of a subalpine conifer across its vertical distribution: an approach using high‐resolution aerial photographs

Many studies have reported shifts in the altitudinal ranges of plant species in response to recent global warming. However, most studies of tree species have been conducted on a small scale and have focused on tree line ecotones by examining tree rings and age structure on account of the long life spans of the trees. To examine the impact of climate change on forest dynamics at a regional scale, we investigated differences in the population density and canopy height of a Japanese subalpine coniferous species, Abies mariesii, between 1967 and 2003 by analysis of high‐resolution aerial photographs of the Hakkoda Mountains, Honshu, Japan. In 712 plots within the photographs we analyzed which environmental variables (including elevation, aspect, wetness, and distance from moorlands) account for these changes. The population density of A. mariesii decreased below 1000 m a.s.l. and increased above 1300 m a.s.l. It also increased around moorlands, which may provide refugia at low elevations. The rate of increase in canopy height was lowest on the southeastern slopes and on the periphery of the moorlands. The distinct changes in the population density of A. mariesii at its distribution limits probably reflect the responses of the population to climatic changes during three decades. Areas surrounding the moorlands may offer refugia in spite of the poor growing conditions there.     

Using Resource Selection Functions to Improve Estimation of Elk Population Numbers

Abstract: Stratification is commonly used to improve sampling efficiency of aerial surveys of ungulate populations with strata typically based on a priori information, such as preflight animal observations or vegetation attributes as surrogates for animal densities. We evaluated the usefulness of stratifying survey units for elk (Cervus elaphus) in the Rocky Mountain foothills of Alberta, Canada, using a resource selection function (RSF). We compared precision and design efficiency (DEFF) of population estimates from stratification approaches based on an RSF model to the past approach using amount of forest cover. We used a sample of telemetry relocations taken over a 3-year period from 165 elk, rarified to times of the day and months of the year when aerial surveys are conducted, to develop the RSF. We then used the top RSF model, based on Akaike's Information Criterion, to derive the average RSF value for an 8-km² survey unit. Using survey data from the first year, we evaluated binning schemes to define RSF-oriented strata based on poststratification and showed that Jenks natural breaks in the RSF values provided the greatest improvement in DEFF and increased precision, compared to 2 other stratification schemes. We then used this approach with data from 2 additional surveys to find that stratification by RSF consistently improves relative precision and design efficiency of elk population estimates, whether we employ pre- or poststratification. Where a RSF is available it could be used as a surrogate for animal densities when conducting stratified sampling for population surveys.     

Estimation of Occupied and Unoccupied Black-Tailed Prairie Dog Colony Acreage in Colorado

Abstract: Black-tailed prairie dogs (Cynomys ludovicianus) are a species of concern and accurate estimates of occupied area are required to assess their status. We conducted aerial line-intercept surveys to estimate colony areas in Colorado, USA, 2006–2007. Optimal allocation based on results from a previous (2002) survey was used to distribute flight time to sample 28 counties. Uncorrected estimates of active and inactive colony areas from the aerial surveys were 329,529 (SE=16,841) ha and 18,292 (SE=2,366) ha, respectively. We attempted to ground-truth a randomly selected sample of 186 colony intercepts but gained complete access to only 150. Ground-truthing demonstrated that aerial surveys estimated only 96% of the true lengths of colony intercepts but overestimated the proportion of active colonies. Corrected estimates of active and inactive colony areas are 319,165 (SE = 20,105) ha and 42,422 (SE = 11,485) ha, respectively. Because ground-truthing was not conducted in the original 2002 survey, uncorrected estimates from this survey are the appropriate metric to be used for comparison to the 2002 data. Our estimates demonstrated a 29% increase (SE = 6.3) in area occupied since surveys were conducted in 2002. These results are useful to state and federal agencies and other conservation partners in determining the condition of the species when conducting status reviews.     

Observation on the initial inoculum source and dissemination of Entomophthorales-caused epizootics in populations of cereal aphids

A total number of 1092 migratory alates were trapped from air in wheat grown area of Yuanyang County, Henan Province from early April through May 2002 in order to confirm the source and dissemination of entomophthoralean inocula to cause epizootics of cereal aphids. Those included 415 Sitobion avenae, 642 Rhopalosiphum padi, 22 Metopolophium dirhodum, and 13 Schizaphis graminum. The trapped alates were daily collected and individually reared for 7 days on wheat plants in laboratory. Of those 341 alates died of fungal infection, taking 31.2% in the trapped alates. These included 224 S. avenae, 106 R. padi, 8 M. dirhodum, and 3 S. graminum. Deaths of all infected alates occurred during the first 5 days and 78.9% of the deaths occurred within the first 3 days. Individual examination under microscope proved that all deaths were attributed to entomophthoralean fungi. Of those Pandora neoaphidis accounted for 84.6%, Conidiobolus obscurus for 9.9%, and Entomophthora planchoniana for 5.5%. Four alate deaths die     

THE ABUNDANCE OF HARBOR SEALS IN THE GULF OF ALASKA

The abundance of harbor seals ( Phoca vitulina richardii ) has declined in recent decades at several Alaska locations. The causes of these declines are unknown, but there is concern about the status of the populations, especially in the Gulf of Alaska. To assess the status of harbor seals in the Gulf of Alaska, we conducted aerial surveys of seals on their haul-out sites in August-September 1996. Many factors influence the propensity of seals to haul out, including tides, weather, time of day, and time of year. Because these "covariates" cannot simultaneously be controlled through survey design, we used a regression model to adjust the counts to an estimate of the number of seals that would have been ashore during a hypothetical survey conducted under ideal conditions for hauling out. The regression, a generalized additive model, not only provided an adjustment for the covariates, but also confirmed the nature and shape of the covariate effects on haul-out behavior. The number of seals hauled out was greatest at the beginning of the surveys (mid-August). There was a broad daily peak from about 1100–1400 local solar time. The greatest numbers were hauled out at low tide on terrestrial sites. Tidal state made little difference in the numbers hauled out on glacial ice, where the area available to seals did not fluctuate with the tide. Adjusting the survey counts to the ideal state for each covariate produced an estimate of 30,035 seals, about 1.8 times the total of the unadjusted counts (16,355 seals). To the adjusted count, we applied a correction factor of 1.198 from a separate study of two haul-out sites elsewhere in Alaska, to produce a total abundance estimate of 35,981 (SE 1,833). This estimate accounts both for the effect of covariates on survey counts and for the proportion of seals that remained in the water even under ideal conditions for hauling out.     

The problem of precision and trend detection posed by small elephant populations in West Africa

The precision of elephant estimates from aerial sample surveys and dung counts is inversely proportional to abundance. West African elephant populations are already small, and the power of a monitoring programme to detect changes in abundance diminishes as the population shrinks in size. Thus it will be difficult to evaluate the effects on elephant numbers of new management policies in West Africa. The same will be true of monitoring schemes for antelope and primate populations that are hunted for bushmeat. Elephant estimates from dung counts are more precise than those from aerial sample surveys, and changes in elephant numbers are more likely to be detected in the subregion by dung counts than by aerial sample surveys.     

Size‐correlated morpho‐physiology of the aroid vine Rhodospatha oblongata along a vertical gradient in a Brazilian rain forest

In this work, we analyse morpho‐physiological modifications presented during the allomorphic growth of the aroid vine Rhodospatha oblongata Poepp throughout its ascent into the forest canopy. We test the hypothesis that morphological modifications in the root, shoot and leaf are followed by a gradual improvement of the xylem vascular system in order to increase water acquisition and transport as body size increases. The characterisation of these structural modifications was based on 30–35 specimens divided into six size classes. The dimensions of shoots, leaves and roots were quantified and qualified. The transition from the terrestrial to the epiphytic phase was followed by a simultaneous increase of leaf number and lamina area, together with increased length and diameter of the petiole. Furthermore, as the plant grows, the shoot internodes become shorter and thicker. However, occurrence of aerial roots is the most important characteristic in the ascending phase. In taller individuals, the increase in number of roots with wider xylem vessels guarantees an increased theoretical xylem hydraulic conductance for this growth phase. Along an acropetal direction of the same shoot, the diameter of xylem vessels increased, while the number of vessels per stele area decreased, in contrast with such allometric models as that of West, Brown and Enquist, showing that xylem vessel number and diameter taper in a reverse manner along the same direction. Such structural changes of R. oblongata allow improved foraging for light and water, facilitating the survival of bigger‐sized plants of this vine in the canopy.