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721.
Peter Torstensson 《Plant Ecology》1987,68(3):169-172
The population dynamics of the annual Spergularia marina was studied during four years on three different sites on a Baltic seashore meadow. The population density varied significantly both between years and between sites. At one of the sites the average population density was higher than at the two other sites. Both differences in reproductive capacity and in density-independent mortality caused differences in population size. Variation in population seed yield or loss of seed or both, between years, to a large extent determined the variation in the population density between years. 相似文献
722.
Ecosystem Recovery Across a Chronosequence of Restored Wetlands in the Platte River Valley 总被引:1,自引:0,他引:1
Wet meadows in the Platte River valley (PRV) consist of linear wetlands in mesic prairie matrix systems that have been degraded
and diminished for agriculture. Restoration in this region is a widespread practice that involves land contouring and seeding
native species, however ecosystem recovery following restoration has never been examined. We quantified recovery trajectories
and rates of above- and belowground plant biomass, soil physical and chemical properties, and C and N pools in a chronosequence
of six restored wet meadows in relation to three natural wetlands. Within each site, we sampled sloughs (deeper habitats)
and adjacent margins (slightly higher elevation) for three consecutive years. Varying hydrologic regimes between habitats
resulted in differential patterns in ecosystem measurements (bulk density, C mineralization) in both natural and restored
wetlands. Total aboveground biomass (TAB), root biomass, root C and N storage, total soil C and N, microbial N, and extractable
N increased with years restored in both margins and sloughs. The model predicted rates of increase did not differ between
habitats, but elevations of linear regressions were higher in sloughs than margins for root N, total soil C, total soil N,
MBN, and extractable total N (P < 0.05). Our results suggest that bulk density and soil organic matter (SOM) represent two useful, easily measured indices
of ecosystem recovery, because they were correlated with many pools and fluxes of C and N. Furthermore, we conclude that most
change in ecosystem structure and function during the first decade following restoration occurs in shallow soil depths, and
ecosystem recovery varies with subtle differences in elevation and associated plant community structure. 相似文献
723.
724.
725.
Sabina Avosani Pietro Franceschi Marco Ciolli Vincenzo Verrastro Valerio Mazzoni 《Journal of Applied Entomology》2021,145(6):518-529
The meadow spittlebug Philaenus spumarius, vector of the bacterium Xylella fastidiosa, relies on vibrational communication to accomplish mating: the female calls to establish a duet with a male. A deeper knowledge of the species’ reproductive biology and behaviour would provide useful information for developing control techniques based on principles of ‘biotremology’, which studies the vibrational behaviour of animals. Playback tests were conducted on single females and male–female pairs of P. spumarius from June to October 2018, and the features of the recorded calling signals were analysed using a wavelet decomposition. Dissections were performed on females to evaluate the relationship between calling activity and ovarioles development. From August onwards, females started to emit calling signals and to develop ovarioles. Female calling activity, duration of their chirps and their responsiveness to mating increased as the season progressed, and they were correlated with ovarioles’ development and presence of mature eggs. Hence, the ovarian maturation represents a key factor in association with the development of the sexual behaviour of P. spumarius females. Conversely, males produced advertisement signals soon after adult eclosion in May, but these signals were not involved in the pair formation process. Mating was achieved only when males produced courtship signals in response to female calling signals and established with them vibrational duets starting from August. Here, we provide new information regarding the P. spumarius’ ethology and hypothesize that potential mating disruption techniques should consider the insect physiology and be applied when both sexes are responsive to mating signals. 相似文献
726.
R. C. Sundriyal 《植被学杂志》1992,3(1):15-20
Abstract. Structure, primary production and energy flow were studied in ungrazed and grazed alpine meadows in the Garhwal Himalaya, India. In grazed grasslands, the cover of graminoids increased, the biomass of palatable species was reduced by about 50%, but the biomass of unpalatable species increased, due to reduced competition from the better-foraged species. Generally, 32% of live shoot and root biomass was consumed during a growing season. Also, above-ground plant productivity increased as a result of plant regrowth, while below-ground productivity decreased. Flow and storage of energy in ungrazed and grazed alpine grasslands showed an accumulation of 10.1 and 8.5 kJ/yr with energy conversion efficiencies of 0.7 and 0.6% respectively. Ca. 46% of the net energy accumulated was consumed by herbivores on the grazed grassland. Only 26% of the net captured energy disappeared from the system in the growing season, mainly via root and litter decomposition. 相似文献