A Study of Hilda Asteroids

Dahlgren, M.; Lahulla, J. F.; Lagerkvist, C. I.; Lagerros, J. S. V.; Mottola, S.; Erikson, A.; Gonano-Beurer, M.; Martino, M. Di

doi:10.1006/icar.1998.5919

Cited by 18 publications

(12 citation statements)

References 31 publications

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“…This study provides basic information related to the combination of hydro-thermal soil characteristics and plant community structure for different slope aspects. According to our results, we found that each slope has a particular hydro-thermal and soil combination (Table 1), and different vegetation composition (Tables 2 and 3), suggesting that slope aspect influences insolation, which affects soil moisture and temperatures regimes in ways that can directly influence the development of vegetation [34][35]. As Van de Water [64] noted, vegetation properties in semi-arid regions depend on both moisture availability and heat load.…”

Section: Resultssupporting

confidence: 50%

“…In general, for mountain environments slope aspect plays a key role in regulating insolation, which in turn affects soil moisture and temperature regimes in ways that can directly influence the development of local vegetation and ecosystems [32][33][34][35]. Slope aspect influences almost all properties of vegetation, such as species composition and distribution, plant performance and photosynthetic efficiency, cover and productivity, species diversity and functional diversity, plant invasion, leaf δ13 C, distribution of C 3 and C 4 plants, and nutrient dynamics [6,33,[36][37][38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Slope Aspect on Plant Community Composition and its Implications for Restoration of a Chinese Mountain Range

Qin¹,

Holden²,

Feng³

et al. 2017

Pol. J. Environ. Stud.

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Excessive human disturbance (e.g., overgrazing, deforestation) has degraded the environment in the Qilian Mountains in China. Vegetative restoration is likely to be a crucial tool to restore these biologically significant habitats, but it is impossible to achieve this goal if the baseline plant community composition and its variation with local environmental conditions were not understood fully. To assess plant community composition by slope aspect, four different aspects -south-facing slope (SF), southwest-facing slope (SW), northwest-facing slope (NW), and north-facing slope (NF) -were surveyed on three almost non-degraded mountains. The results showed that each slope aspect has different abiotic environments. From SF to NF, soil water content has an increasing trend, but it shows no difference between SF and SW; and daily soil temperature and pH have a decreasing trend, while the former shows no difference between SF and SW, and SW and NW; and the latter shows no difference between SW and NW; and soil organic carbon was significantly increased, but soil bulk density was significantly decreased. Herbaceous plants were dominant on SF, SW, and NW, and trees (Picea crassifolia) were dominant on NF. From SF to NW, the dominant herbaceous plants were Agropyron cristatum and Stipa grandis, Agropyron cristatum and Carex aridula, and Kobresia humilis and Carex crebra, respectively, while on NF they were Carex spp. and Polygonum macrophyllum. The baseline survey points to the need to consider underlying patterns in abiotic conditions when planning restoration programs in these degraded mountain habitats, and to select native plants similar to the original vegetation. The survey provides a vital milestone for the development of policy-based funding initiatives and for ongoing vegetation monitoring during restoration to assess if these vegetative targets have been met.

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Section: Resultssupporting

confidence: 50%

Section: Introductionmentioning

confidence: 99%

Influence of Slope Aspect on Plant Community Composition and its Implications for Restoration of a Chinese Mountain Range

Qin¹,

Holden²,

Feng³

et al. 2017

Pol. J. Environ. Stud.

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“…Large (diameters 10 km) Hilda asteriods have a range of V − R colors, 0.38-0.49 (Dahlgren et al 1998), which is similar to those colors of comets (Hainaut & Delsanti 2002). In particular, ecliptic comets (ECs) span the same narrow range of V − R (Lamy & Toth 2009) as the Hildas and are thought to have originated as outer solar system Centaurs which were subsequently scattered into the inner solar system due to gravitational interactions with Jupiter.…”

Section: Introductionmentioning

confidence: 88%

ALBEDOS OF SMALL HILDA GROUP ASTEROIDS AS REVEALED BYSPITZER

Ryan

Woodward

2011

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We present thermal 24 μm observations from the Spitzer Space Telescope of 62 Hilda asteroid group members with diameters ranging from 3 to 12 km. Measurements of the thermal emission, when combined with reported absolute magnitudes, allow us to constrain the albedo and diameter of each object. From our Spitzer sample, we find the mean geometric albedo, p V = 0.07 ± 0.05, for small (D < 10 km) Hilda group asteroids. This Spitzer-derived value of p V is greater than and spans a larger range in albedo space than the mean albedo of large (D 10 km) Hilda group asteroids which is p V = 0.04 ± 0.01. Though this difference may be attributed to space weathering, the small Hilda group population reportedly displays greater taxonomic range from C-, D-, and X-type whose albedo distributions are commensurate with the range of determined albedos. We discuss the derived Hilda size-frequency distribution, color-color space, and geometric albedo for our survey sample in the context of the expected migration induced "seeding" of the Hilda asteroid group with outer solar system proto-planetesimals as outlined in the "Nice" formalism.

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“…Our study of the Cybele asteroids completes an ongoing investigation of the physical properties of the OBAs, starting with the Hildas (Dahlgren and Lagerkvist 1995, Dahlgren et al 1997, 1998 and with the Trojan population well in progress (Mottola et al, private communication). The aim of both the Hilda and the Trojan studies, as well as the result presented here for the Cybele asteroids, has been to derive spin properties from photometric observations and surface compositions from spectroscopic observations in order to establish a complete framework of the physical properties of OBAs and an integrated model of their evolution.…”

Section: Introductionmentioning

confidence: 93%

“…The Hilda group was studied extensively by photometric and spectroscopic observations by Dahlgren and Lagerkvist (1995) and Dahlgren et al (1997Dahlgren et al ( , 1998Dahlgren et al ( , 1999, showing that the Hilda population is dominated by the small asteroids belonging to taxonomic type D. A difference was found in the composition between small and large Hilda asteroids in the sense that large objects were of type P while the small ones mainly consisted of taxonomic type D. They found that the spin rate distribution of the Hildas is markedly non-Maxwellian and that the smaller Hildas have significantly larger mean lightcurve amplitudes than main belt asteroids of similar sizes. The spin properties of the Trojans are to a large extent unknown, as seen in Binzel and Sauter (1992) and Zappalà et al (1989).…”

Section: Introductionmentioning

confidence: 99%