Steep Sites Research Articles

Seismic response characteristics of offshore sites in the Sagami Bay, Japan—Part I: Comparison of spectral inversion and ratio under weak motions

Understanding offshore site amplification (AF) characteristics is crucial for marine engineering. Thus far, the spectral ratio (SR) has been widely used to analyze offshore AF characteristics, despite its reliability not yet being fully investigated. In this study, we used 826 ground-motion data recorded at 6 offshore and 19 onshore stations in the Sagami Bay region to reveal the source, path, and AF characteristics using the generalized inversion technique (GIT). The average stress drops for the shallow crustal, subduction interface, and subduction slab earthquakes were 3.55, 6.59, and 7.07 MPa, respectively. The offshore sites were categorized into flat and steep stations based on the local slope gradient (LSG), and systematic AF characteristics were observed. We found that the topography had a negligible influence on the flat free-field station KNG205. AFs obtained using the GIT and SR were analyzed and compared, revealing two main differences: (1) SR-obtained AF values were significantly larger than GIT-obtained AF values above 0.5 Hz and 5 Hz at the flat and steep sites, respectively; (2) resonant frequencies estimated using the SR drifted to lower and higher frequencies for flat and steep sites, respectively. The ineffectiveness of the SR for flat and steep stations was attributed to the effects of topography and seawater pressure on low- and high-frequency vertical ground-motions, respectively. These results suggest that the SR is only reliable for estimating AF curves at marine free-field sites and low-frequency AFs at steep sites. The LSG may play an important role in offshore ground-motion studies.

Határkő

A client's dream to have a Scandina - vian styled home in Budapest took form when remodelling an existing villa in the Buda Hills. Faced with the problems of an extremely steep site, hard to access by car, and the need for will lit spaces the designers adopted the idea of reversing the home: entrance, garage and living spaces sitting above the bedrooms and ancillary functions. Working with brick cladding, raw concrete, and daylighting as design tools a balance between exterior and interior has been achieved. Whether or not the home is Scandinavian in style is open for question as it seems to fit comfortably alongside its contemporaries found in modern Hungarian architecture.

Evaluating Variability of Ground Thermal Conductivity within a Steep Site by History Matching Underground Distributed Temperatures from Thermal Response Tests

The variability of ground thermal conductivity, based on underground conditions, is often ignored during the design of ground-source heat pump systems. This study shows a field evidence of such site-scale variations through thermal response tests in eight borehole heat exchangers aligned at a site on a terrace along the foothills of mountains in northern Japan. Conventional analysis of the overall ground thermal conductivity along the total installation length finds that the value at one borehole heat exchanger is 2.5 times that at the other seven boreholes. History matching analysis of underground distributed temperature measurements generates vertical partial ground thermal conductivity data for four depth layers. Based on the moving line heat source theory, the partial values are generally within a narrow range expected for gravel deposits. Darcy velocities of groundwater are estimated to be 74–204 m/y at the borehole with high conductivity, increasing in the shallow layers above a depth of 41 m. In contrast, the velocities at the other seven boreholes are one-to-two orders of magnitude smaller with no trend. These high and low velocity values are considered for the topography and permeability. However, the relatively slow groundwater velocities might not apparently increase the partial conductivity.

GIS-based spatial analysis of landslides in Rathnapura District, Sri Lanka

The levels of landslide hazards are dependent on land physical attributes, agriculture practices and other human activities. Landslides are a serious concern in steep land areas where intensive storms are common. Southwest monsoon brought heavy rains and strong winds to Sri Lanka. Rathnapura District is a landslide prone area in Sabaragamuwa Province, Sri Lanka due to southwest monsoonal rain. GIS technologies could provide a powerful tool to model the landslide hazards for their spatial analysis and prediction. This is because the collection, manipulation and analysis of the environmental data on landslide hazard can be accomplished much more efficiently and cost effectively. The objective of this study was to identify the spatial distribution of landslides in Rathnapura district. Four variables, slope, elevation, rainfall, soil type and land use, were evaluated as landslide inducing factors in the area. Eighteen Divisional Secretariat Divisions in Rathnapura district was the sampling area for the study. Four Landslide locations and risk areas in the area were identified by GPS coordinates and soil samples were collected in identified areas. Grain size distribution that was used to classify the soil was done by sieve analysis. Stream ordering was calculated by Shreve and Strahler method and the water volume, number of streams and slope gradient were analyzed to create classified layer of slope, rainfall intensity, land use, drainage and slope. Classified layers were weighted according to their contribution percentage for the landslides. By applying weighted overlaying method, study area was categorized into five groups as high-risk area, risk area, moderate risk area, low risk area and no risk area. Natural factors like slope, soil type and drainage density as well as man-made factors are caused for the landslides in the area. Landslide events in Rathnapura district are strongly correlated to many factors. As slope increased, the percentage of land affected by landslides, when the soils were saturated, increased sharply on land used for crop production, indicating that agricultural activity and the associated removal of deep-rooted permanent vegetation increased the landslide hazard on steep sites.

An Optical–Thermal Surface–Atmosphere Radiative Transfer Model Coupling Framework With Topographic Effects

Most surface–atmosphere radiative transfer models (RTMs) work only for flat surfaces, with the exception being time-consuming 3-D scene-based models. The deficiency of flat-surface RTMs that do not consider topographic effects is that their applications in earth observation and simulation studies are impaired because rugged terrains make up approximately 24% of the global land surface. Another deficiency of most surface–atmosphere RTMs is that they model reflected and emitted (i.e., solar and thermal) radiative transfer processes separately, which limits RTMs in applications, such as fire detection. This study proposes a unified optical–thermal RTM coupling framework (RTM-CF) that considers topographic effects based on the four-stream approximation theory. The framework couples surface–atmosphere RTMs and can simultaneously simulate a set of parameters at the top-of-atmosphere (TOA) and bottom-of-atmosphere (BOA) levels from optical and thermal spectral ranges. These parameters include the TOA directional radiance/reflectance, TOA exitance/albedo, TOA net radiation, surface radiance/reflectance/albedo, surface downward/upward/net radiation, and FAPAR/APAR. The RTM-CF with topographic effects is compared with the well-known 3-D discrete anisotropic radiative transfer (DART) ray-tracing model and validated by field measurements from three steep sites. The evaluation results show that the simulated reflectance, radiance, and radiation fluxes are consistent with the DART results and the field data, with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R^{2}&gt;0.93$ </tex-math></inline-formula> and scatter points close to the 1:1 line for all parameters. In this RTM-CF, atmospheric and topographic effects are simultaneously incorporated, and the surface anisotropy is also effectively considered. This framework is highly modularized, which enables it to be easily adapted to different submodels.

Fine Coregistration & Brunch-cut for Unwrapping Interferometric Phase

Earth observation and environmental control arebecoming more important where the realization of DEM by thetechnique of interferometry of RSO images facilitates thecontrol of terrestrial deformations, which is the subject of thispaper.The unwrapping phase is a very important step in theinterferometry process, especially to treat it carefully in steepdegraded and mountainous ground. We have focused on thereduction and sometimes the elimination of the residues in flatterrains and otherwise to keep the maximum of the residues inthe very steep sites. For this purpose, the methods developedand proposed are based on a transformation by the ISODATAwhich is based on KMEANS and the double passage of themedian filter, and this in order to limit the creation of thebrunch-Cut for the progress of the filtered interferogram(elimination of large black spot on The Brunch-Cut image).Thetests of this method were carried out on several sites, andshowed good results.

In-situ Observations of Infragravity Response during Extreme Storms on Sand and Gravel Beaches

Billson, O.J.; Russell, P.; Davidson, M.; Poate, T.; Amoudry, L.O., and Williams, M.E., 2020. In-situ observations of infragravity response during extreme storms on sand and gravel beaches. Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 382–386. Coconut Creek (Florida), ISSN 0749-0208.Infragravity waves (frequency = 0.005 – 0.05 Hz) play a key role in coastal storm impacts such as flooding and beach/dune erosion. They are known to dominate the inner surf zone on low-sloping sandy beaches during storms. However, in large wave conditions, their importance on different beach types, of variable swell and wind-waves dominance, is largely unknown. Here, a new dataset is presented comprising in-situ observations during storm wave conditions (significant wave height of 3.3 m, peak periods of 18 s and return periods up to 1 in 60 years) from two contrasting sites: a low-sloping sandy beach and a steep gravel beach. Wave measurements were collected seaward of the breakpoint by wave buoys and bed-mounted acoustic Doppler current profilers, and through the surf zone using arrays of pressure transducers. Wave spectra showed contrasting evolution from the shoaling zone to the inner surf zone at the two sites. At the sandy beach, gravity band energy dissipated gradually as depth reduced, while infragravity band energy simultaneously increased, resulting in strongly infragravity-dominated wave spectra in the inner surf zone. At the steep gravel site, a rapid drop in short wave energy was observed, with limited growth of infragravity energy so that inner surf zone spectra showed a low energy peak in the infragravity band. The normalized bed slope parameter indicated whether infragravity waves were generated by bound long wave release or breakpoint forcing, showing that the former (latter) was dominant on the sandy (gravel) beach. In spite of these differences, the shoreline wave spectra under storm wave conditions were infragravity-dominated on both the sandy and gravel beaches.

Environmental factors and management intensity affect in different ways plant diversity and pastoral value of alpine pastures

• 3839 vegetation surveys were carried out across pastures of Western Italian Alps. • Plant diversity (PD) and forage Pastoral Value (PV) were computed. • The effects of management intensity and environment on PD and PV were assessed. • PD was mostly affected by environmental factors rather than management intensity. • Management intensity had a larger effect on PV if compared to environmental factors. Based on a wide dataset of vegetation surveys carried out across the pastures of Western Italian Alps, the objective of the research was to determine the relative importance of management intensity and environmental factors (i.e. topography, climate, bedrock type) on 1) plant diversity and 2) forage quality and productivity (Pastoral Value - PV) of alpine summer pastures. Plant diversity (i.e. Shannon diversity index and species richness) and PV were affected in different ways by both factors, but they showed a hump-shaped relationship with pastoral management intensity. Plant diversity was mainly affected by environmental factors (elevation and total annual precipitation) rather than management intensity. Shannon index and species richness were lower at higher elevations and in locations with higher precipitation, and they were higher on steep sites and calcareous bedrock. However, management intensity had a noteworthy influence on plant diversity. PV was strongly affected by management intensity, whereas environmental factors had limited importance. Differently from plant diversity, PV was not elevation dependent as several vegetation communities with either a low and a high PV occurred within a large range of altitude. PV was higher on flattest sites, in sites with a low level of precipitation, and on calcareous bedrock. Our results highlighted that environmental factors are the main drivers of plant diversity in alpine pastures. Pastures are typically located at higher elevation, are less accessible, and lay in less homogeneous areas where the environmental constraints have a predominant effect on plant community development with respect to management intensity. Contrariwise, the influence of management intensity on PV suggests that an appropriate grazing management can enhance forage productivity and quality for livestock even in harsh environments.

SUAS-Based Remote Sensing in Mountainous Areas: Benefits, Challenges, and Best Practices

Small unmanned aircraft systems (sUAS) offer key benefits over manned aircraft and satellite platforms used for remote sensing research, such as high spatial resolution, portability, simplicity of implementing ground control, affordability, and lack of reliance upon third-party imagery providers. Mountainous areas, which we define as locations that are higher than 2500 m in elevation and that contain slopes greater than 25°, pose a number of challenges to sUAS mapping operations that other environments do not, including reduced aircraft performance, cold temperatures, high winds, and limited accessibility. The purpose of our paper is to identify these challenges and discuss workflows used to mitigate these difficulties to achieve greater logistical and operational efficiency. We used a DJI Inspire 2 multirotor aircraft to conduct mapping missions in remote, mountainous areas to support subalpine forest inventory and assessment in Nevada and southern Utah. We identified several potential obstacles to collecting high-quality aerial image data in environments with high topographic variability and landscape heterogeneity. We found that sUAS are very useful and practical when performing mapping missions in these circumstances when operators account for potential environmental limitations (e.g., poor weather, shortened flight times due to atmospheric conditions, line-of-sight challenges, difficulty implementing ground control across steep sites, ensuring applicable aviation regulations are observed) and technological capabilities (terrain following, flight duration, etc.). This work has implications for a wide variety of scientific and management disciplines that involve low-altitude remote sensing research in mountainous areas.

Remote sensing of ploidy level in quaking aspen (Populus tremuloides Michx.)

Abstract Ploidy level in plants may influence ecological functioning, demography and response to climate change. However, measuring ploidy level typically requires intensive cell or molecular methods. We map ploidy level variation in quaking aspen, a dominant North American tree species that can be diploid or triploid and that grows in spatially extensive clones. We identify the predictors and spatial scale of ploidy level variation using a combination of genetic and ground‐based and airborne remote sensing methods. We show that ground‐based leaf spectra and airborne canopy spectra can both classify aspen by ploidy level with a precision‐recall harmonic mean of 0.75–0.95 and Cohen's kappa of c. 0.6–0.9. Ground‐based bark spectra cannot classify ploidy level better than chance. We also found that diploids are more common on higher elevation and steeper sites in a network of forest plots in Colorado, and that ploidy level distribution varies at subkilometer spatial scales. Synthesis. Our proof‐of‐concept study shows that remote sensing of ploidy level could become feasible in this tree species. Mapping ploidy level across landscapes could provide insights into the genetic basis of species' responses to climate change.

Effects of forest residue harvesting on short-term changes in soil solution chemistry

ABSTRACTShort-term (three to four years) effects of forest harvesting on soil solution chemistry were investigated at two Norway spruce sites in southern Norway, differing in precipitation amount and topography. Experimental plots were either harvested conventionally (stem-only harvesting, SOH) or whole trees, including crowns, twigs and branches were removed (whole-tree harvesting, WTH), leaving residue piles on the ground for some months before removal. The WTH treatment had two sub-treatments: WTH-pile where there had been piles and WTH-removal, from where residues had been removed to make piles. Increased soil solution concentrations of NO3–N, total N, Ca, Mg and K at 30 cm depth, shown by peaks in concentrations in the years after harvesting, were found at the drier, less steep site in eastern Norway after SOH and WTH-pile, but less so after WTH-removal. At the wetter, steeper site in western Norway, peaks were often observed also at WTH-removal plots, which might reflect within-site differences in water pathways due largely to site topography.

Log house performance in the 2016 Kaikoura earthquake

This paper describes the performance of log houses in the 2016 Kaikoura earthquake. Most of these houses are in the Mt Lyford village 45 km south-east of Kaikoura.&#x0D; Typical log houses at Mt Lyford were built using 200mm diameter machined logs. A smaller number of log houses were built with much larger hand-hewn logs of less regular shapes, in traditional log house construction. Most houses were constructed on a concrete slab incorporating the foundations. A small number, especially those on steep sites, had timber poles supporting a timber ground floor platform.&#x0D; Most of the log houses suffered some lateral movement and subsequent damage. Very few of the houses were damaged beyond repair, and the overall performance was excellent considering the nature of the quake.&#x0D; One house close to Waiau suffered extreme near-fault shaking, leading to extensive damage, but this is considered to be the result of exceptional ground movement rather than any deficiencies in the design or construction.

Widespread latent infection of Cryptostroma corticale in asymptomatic Acer pseudoplatanus as a risk for urban plantations

SummarySooty bark disease (SBD) caused by the pathogen Cryptostroma corticale is currently one of the risks to the population of Acer pseudoplatanus in Europe. After a number of records of symptomatic and dead trees in Prague, assessment of the latent non‐symptomatic stage of SBD was questioned as a means to forecast the health risk of the A. pseudoplatanus population. We used two methods of early detection of C. corticale in non‐symptomatic trees: cultivation from wood tissue on agar plates and a culture‐free approach based on nested PCR with newly designed species‐specific primers. The pathogen was detected in 25% of 112 examined trees from seven localities in Prague, but the disease incidence might be higher if more A. pseudoplatanus trees in Prague were included and if the crown infections were considered. The presence of C. corticale was positively correlated with discoloured wood, but its presence did not depend on the occurrence of external symptoms. Infected trees were more frequently found in groups on steep sites at higher elevations. In addition, heavier NOx pollution combined with more paths and roads increased the incidence of C. corticale.

The Discovery of Great Basin Bristlecone Pine,Pinus Longaeva, in the Tushar Mountains of the Fishlake National Forest in Central Utah, USA

Abstract. In this paper, we provide the first documented evidence of Pinus longaeva from the Tushar Mountain range in central Utah. The P. longaeva trees, initially noticed at the end of September, and further surveyed during the first week of October 2016 are present on 6 small sites on the north-facing slopes of the North Fork of North Creek in the Tushar Mountains of the Fishlake National Forest. We estimate that there are currently up to 179 live individuals that range in age from seedlings to approximately 1400 years. Our data indicate these are particularly slow-growing specimens on very steep sites, in soil of igneous origin. Though many of the trees are infested with dwarf mistletoe, there is little indication that the population is currently at risk from fire, bark beetle attack, or many other common pathogens characteristic of other Pinus species. Nonetheless, there may be reasons for concern associated with future changes to the climate of southern Utah, as well as the impact of invasive specie...

Influence of soil and topography on defoliation intensity during an extended outbreak of the common pine sawfly (Diprion pini L.)

Abstract: Insect herbivore disturbances are likely to intensify as a consequence of climate change. In Finland, outbreaks of the common pine sawfly (Diprion pini L.), which feeds on Scots pine (Pinus sylvestris L.) needles, and resulting damage to forests have already increased. Although drivers of sawfly outbreak dynamics have been investigated, the effects of topography and soil fertility have not been fully elucidated. We studied the effect of elevation, slope and soil properties (carbon and nitrogen contents, C/N ratio, pH, texture and horizon thicknesses) on the defoliation intensity of 28 plots (227-531 m2), located in a 34.5 km2 forested area in eastern Finland suffering from an extended outbreak of D. pini. Plot elevation and slope (relative relief 35 m, maximum elevation 200 m a.s.l.) were derived from a digital elevation model and the soil properties from samples of the humus layer (Of+Oh), (Ah+)E and B horizons of podzol profiles. Defoliation was greater on the more fertile and flatter sites than on less fertile and steeper sites, but independent of elevation. The soil property most strongly correlated to plot mean defoliation was the C/N ratio of the humus layer (Spearman’s ρ = -0.68). However, logistic modelling showed that the thickness of the (Ah+)E-horizon had the highest classification accuracy in predicting the probability of a plot having moderate to severe (>20%) defoliation. Our study showed that forest damage caused by D. pini was related to topography and soil fertility. Taking these factors into account could help in understanding the population dynamics of D. pini, in modeling of insect outbreaks and in forest management planning.

Vegetation heterogeneity caused by an ecosystem engineer drives oviposition-site selection of a threatened grassland insect

Soil-disturbing ecosystem engineers play an important role in plant-species diversity in grasslands as they increase vegetation heterogeneity by creating gaps due to burrowing or mound-building activities. However, knowledge of the ecological importance of these microsites for arthropods is still rare. In this study, we analyse the role of ant-nest mounds of the yellow meadow ant (Lasius flavus) for oviposition-site selection of the silver-spotted skipper (Hesperia comma). Ant mounds were searched for H. comma eggs. Microclimatic and vegetation parameters were ascertained at occupied sites and control sites within the matrix vegetation. Furthermore, we analysed the habitat requirements of L. flavus by means of nest counting and the sampling of environmental parameters within different sites. L. flavus occurred most frequently in abandoned and less steep sites with deeper soils. Mean egg occupancy rates of H. comma on ant hills were 32 %, nearly twice as high as at control sites (18 %). In contrast to the surrounding vegetation, nest mounds were characterized by a lower vegetation cover and litter and a higher proportion of bare ground. Furthermore, they had a higher cover of host plants compared with control samples. These microhabitats offered the following essential key factors for the larval development of H. comma: (1) a suitable microclimate due to open vegetation and (2) a high amount of host plants. This study highlights the importance of L. flavus as an ecosystem engineer within central European grasslands because this species increases vegetation heterogeneity.

Tree species diversity promotes aboveground carbon storage through functional diversity and functional dominance.

The relationship between biodiversity and ecosystem function has increasingly been debated as the cornerstone of the processes behind ecosystem services delivery. Experimental and natural field‐based studies have come up with nonconsistent patterns of biodiversity–ecosystem function, supporting either niche complementarity or selection effects hypothesis. Here, we used aboveground carbon (AGC) storage as proxy for ecosystem function in a South African mistbelt forest, and analyzed its relationship with species diversity, through functional diversity and functional dominance. We hypothesized that (1) diversity influences AGC through functional diversity and functional dominance effects; and (2) effects of diversity on AGC would be greater for functional dominance than for functional diversity. Community weight mean (CWM) of functional traits (wood density, specific leaf area, and maximum plant height) were calculated to assess functional dominance (selection effects). As for functional diversity (complementarity effects), multitrait functional diversity indices were computed. The first hypothesis was tested using structural equation modeling. For the second hypothesis, effects of environmental variables such as slope and altitude were tested first, and separate linear mixed‐effects models were fitted afterward for functional diversity, functional dominance, and both. Results showed that AGC varied significantly along the slope gradient, with lower values at steeper sites. Species diversity (richness) had positive relationship with AGC, even when slope effects were considered. As predicted, diversity effects on AGC were mediated through functional diversity and functional dominance, suggesting that both the niche complementarity and the selection effects are not exclusively affecting carbon storage. However, the effects were greater for functional diversity than for functional dominance. Furthermore, functional dominance effects were strongly transmitted by CWM of maximum plant height, reflecting the importance of forest vertical stratification for diversity–carbon relationship. We therefore argue for stronger complementary effects that would be induced also by complementary light‐use efficiency of tree and species growing in the understory layer.

Sediment dynamics and their potential influence on insular-slope mesophotic coral ecosystems

Although sediment dynamics exert a fundamental control on the character and distribution of reefs, data on sediment dynamics in mesophotic systems are scarce. In this study, sediment traps and benthic photo-transects were used to document spatial and temporal patterns of suspended-sediment and bed-load dynamics at two geomorphically distinct mesophotic coral ecosystems (MCEs) on the upper insular slope of southwest Puerto Rico. Trap accumulation rates of suspended sediment were relatively low and spatiotemporally uniform, averaging <1mgcm−2 d−1 and never exceeding 3mgcm−2 d−1 over the sampled period. In contrast, trap accumulation rates of downslope bed-load movement were orders of magnitude higher than suspended-sediment accumulation rates and highly variable, by orders of magnitude, both spatially and temporally. Percent sand cover within photo-transects varied over time from ~10% to more than 40% providing further evidence of downslope sediment movement. In general, the more exposed, lower gradient site had higher rates of downslope sediment movement, higher sand cover and lower coral cover than the more sheltered and steep site that exhibited lower rates of downslope sediment movement, lower sand cover and higher coral cover. In most cases, trap accumulation rates of suspended sediment and bed load varied together and peaks in trap accumulation rates correspond to peaks in SWAN-modeled wave-orbital velocities, suggesting that surface waves may influence sediment dynamics even in mesophotic settings. Though variable, off-shelf transport of sediment is a continuous process occurring even during non-storm conditions. Continuous downslope sediment movement in conjunction with degree of exposure to prevailing seas and slope geomorphology are proposed to exert an important influence on the character and distribution of insular-slope MCEs.

The Eye of Reflection: Al-Nabulusi’s Spatial Interpretation of Ibn ʿArabi’s Tomb

Upon his takeover of Damascus in 1516, Sultan Salim hurriedly commissioned the building of a religious complex over the grave of the celebrated thirteenth-century Andalusian Sufi master Ibn ʿArabi, an act that was and still is shrouded with mystery and intrigue. The complex was constructed on a steep site at three levels, comprising a mosque, a tomb chamber, and an external garden. For 160 years following its construction, the building itself played no role in the intensifying debates over Ibn ʿArabi’s controversial, yet influential, teachings. In 1678, however, ʿAbd al-Ghani al-Nabulusi, a passionate follower and defender of Ibn ʿArabi, incorporated for the first time the architecture of the tomb in his multifaceted polemics. In a treatise titled Al-Sirr al-mukhtabī fī ḍarīḥ ibn al-ʿArabī, al-Nabulusi presented a sophisticated spatial interpretation of this rather humble building—its setting, design, and spatial layout—based on complex visual hermeneutics, according to which visible and invisible reality interplayed to construct a unique understanding of the tomb’s spatiality. This essay examines the sophisticated visual strategy with which al-Nabulusi interpreted the building to reveal its concealed mystery.

Responses of grazed New Zealand hill pastures to rates of superphosphate application

Effects of superphosphate application rates on pasture production were measured between 1975 and 1988 within 12 grazed farmlets on steep hill country at the Ballantrae Hill Country Research Station in southern Hawke's Bay. The low fertiliser (LF) treatment received 125 kg ha−1 superphosphate pa, and the high fertiliser (HF) an average 625 kg ha−1 pa from 1975 to 1979, then 375 kg ha−1 pa subsequently. No fertiliser was applied to one LF (LFNF) and one HF (HFNF) farmlet after 1980. Soil Olsen phosphorus (P) level declined slightly for the LF treatment as maintenance requirements exceeded P inputs; rose in response to increased fertiliser inputs in the HF treatment but more slowly than anticipated maybe because of the poor fertiliser application history and low starting Olsen P; and declined in the HFNF treatment after cessation of fertiliser inputs. Pasture production was 19% greater in HF than LF in year 1, and on average 39% greater in years 2 to 13. Size of earthworm populations measured up to 30 years after treatments commenced was highly related to level of pasture production, and there was no evidence of deleterious effects of superphosphate application on earthworm populations. Pasture production declined by 3% pa in HFNF after fertiliser application ceased. Variability of annual pasture production was large, year-to-year variation about the mean being 35% for HF and 47% for LF (CV = 8.5% and 12.7%, respectively). This suggests comprehensive farm system redesign will not be required in the near or medium term to cope with the gradual onset of climate change, as farmers already manage large year-to-year variability with existing systems and their careful implementation should suffice. Estimated maximum annual production with non-limiting P supply for low-slope (1–12°), medium-slope (13–25°) and steep (>25°) sites was estimated to be 14.8, 11.5 and 9.4 t DM ha−1 from curves derived using Bayesian statistics. The Olsen P level for 97% maximum pasture production was 18 µg g−1; converted to a volumetric basis this equates to about 15 µg mL−1 which is lower than the commonly accepted industry guideline for near maximum pasture production of 20 µg mL−1.