Economic utility of 3D remote sensing data for estimation of site index in Nordic commercial forest inventories: a comparison of airborne laser scanning,digital aerial photogrammetry and conventional practices

ABSTRACT

Forest productivity is a crucial variable in forest planning, usually expressed as site index (SI). In Nordic commercial forest inventories, SI is commonly estimated by a combination of aerial image interpretation, field assessment and information obtained from previous inventories. Airborne laser scanning (ALS) and digital aerial photogrammetry (DAP) data can alternatively be used for SI estimation, however the economic utilities of the inventory methods have not been compared. We compared seven methods of SI estimation in a cost-plus-loss analysis, by which we added the expected economic losses due to sub-optimal treatment decisions to the inventory costs. The methods comprised direct and indirect estimation from combinations of ALS, DAP and stand register data, and manual interpretation from aerial imagery supported by field assessment and information from previous inventories (conventional practices). The choice of method had great impact on both the accuracy and the economic value of the produced estimates. Direct methods using bitemporal ALS and DAP data gave the best accuracy and the smallest total cost. DAP was a suitable and low-cost data source for SI estimation. Estimation from single-date ALS and DAP data and age obtained from the stand register provided practical alternatives when applied to even-aged stands.     

Vegetational changes in the Galápagos Islands during the period 1966–1973

Analysis of 12 permanent sample plots established in the Galápagos showed that introduced mammals have had a destructive influence on the vegetation; closed forest and scrub have been changed into open vegetation. The plots provide information on the regeneration ability of various types of vegetation. Scalesia forest, dominated by the endemic Scalesia pedunculata Hook. f., might under certain circumstances regenerate rapidly. Miconia scrub, dominated by the endemic Miconia robinsoniana Cogn., regenerates slowly and is consequently more vulnerable to the activities of man and introduced mammals. Arid zone vegetation, characterised especially by endemic species of Opuntia, is able to regenerate, but it is still too early to estimate how the regeneration will proceed. The suggested conservation measures include a continuation of the programme for elimination or control of introduced mammals, and a stronger control with the National Park areas on inhabited islands. Financial support is needed for the Galápagos National Park Service and the Charles Darwin Research Station to continue and enlarge the activities necessary to preserve the unique wildlife of the Galápagos Islands.     

Heterogeneity of bacterial populations and pesticide degradation potentials in the unsaturated zone of loamy and sandy soils

Soil microbial processes play an important role in relation to pesticide pollution of groundwater, and may be strongly influenced by hydrological and geochemical properties. The consequences of such heterogeneous environments on bacterial biomass, enzymatic activities, carbon utilisation patterns, and pesticide mineralisation potentials in the unsaturated zone of a sandy loam and a coarse sandy soil profile were studied. In sandy loam soil profiles the number of bacteria decreased from 10⁹ cells g^-1 in the surface layers to about 10⁷ cells g^-1 at 1.5-5 m depth. Simultaneously, the hydrolysis of fluorescein diacetate and arylsulfatase activity decreased to below the detection limit at about 1.5 m depth, and carbon utilisation patterns showed that bacterial populations from surface soil were significantly different from those from 4 m depth. Bacterial biomass and activity in macropore soil tended to be slightly higher than in matrix soil, and the carbon utilisation patterns of bacterial populations extracted from macropore soil and from matrix soil seemed to be different. Maximally 3% of ¹⁴C-labelled mecoprop and isoproturon was mineralised in soil from the 1-1.5 m depth, and less than 1.5% was mineralised in soil from the 3.5-4 m depth. The macropore soil tended to have a higher degradation potential than the matrix soil. The total number of bacteria in the coarse sandy soil profile decreased from about 10⁸ in the plough layer to 10⁷ cells g^-1 at 0.4-2 m. The enzymatic activities and the degradation potentials of ¹⁴C-labelled mecoprop and isoproturon were significantly correlated (r² >0.79) and showed a distinct decrease at about 0.4 m. In addition to the depth variability, a horizontal heterogeneity in this soil was observed as horizons or compartments that differed in colour, i.e. with different chemical composition and concentrations of Fe and organic matter. Counts of viable bacteria and measurements of fluorescein diacetate hydrolysis and arylsulfatase activity confirmed a high variability of microbial biomass and activity in the sandy soil profile.     

Forms and plant-availability of sulfur in cattle and pig slurry

The contribution of animal slurry to the supply of S to plants was studied. The total-S content of cattle and pig slurry was significantly correlated to DM and nitrogen content and was composed of sulfide, sulfate and C-bonded S. During 42 weeks of storage sulfate concentrations decreased and sulfide and C-bonded S concentrations increased. In a pot experiment plant-availability of S in slurry was found to be low, 5 to 7% of total-S.     

Identifying, understanding, and describing spatial processes in agricultural landscapes — four case studies

To evaluate the quality of the ecosystem and for making resources and land management decisions landscapes have to be assessed quantitatively. For a better understanding of landscape processes and their characterization, the analysis of the inherent variability is a major factor. Four case studies in which problems associated with landscape analysis are discussed. Spatial processes remain a main focus, as their analysis provides information on the relation between relevant state variables in agricultural landscapes. Variogram analysis showed that mineral soil nitrogen (N_min) sampled in a field at different scales, domains, and times is an instationary spatial process. Spatial association of grain yield, soil index and remotely sensed vegetation index may not be identifiable from kriged contour maps as local coincidence may be obscured behind classified areas. Crop yield in subsequent years and remotely sensed information are not related if a unique response is assumed. An alternative data stratification procedure is described here for the identification of different response functions in agricultural ecosystems. Processes of crop yield and underlying variables are described in autoregressive state-space models. This technique incorporates both deterministic and stochastic relations between different variables and is based on relative changes in space.     

Composition of characteristic soils on the raised atoll Bellona,Solomon Islands

Knowledge is scarce about the composition of soils on Bellona and other Pacific atolls. Such knowledge is important as it is closely related to sustainable land use of these special soils formed on carbonatic/phosphatic materials. Therefore, the micromorphological, chemical and mineralogical composition of samples from genetic horizons in three dominant Bellonese soils (Malanga, Kenge Ungi and Kenge Toaha) and underlying rock (Tanahu) were investigated. Tanahu mainly consists of dolomite, but this mineral is absent in the three soils, which are dominated by phosphate-containing minerals. The Malanga soil is strongly dominated by Ca and P with minor amounts of Al, F and Fe present in fluorapatite, hydroxyapatite and crandallite. In contrast, Al, Fe and P dominate in the Kenge Ungi and Kenge Toaha soils in accordance with a mineralogy consisting of crandallite together with aluminum oxides (gibbsite/boehmite) and iron oxides, mainly goethite with minor contents of hematite. The observed carbonate for phosphate substitution in the apatites and crandallite is important as it indicates an increased phosphate availability in the soils. All three soil samples contain ≤ 1% Si and very little K and Mg. Total contents of essential microelements are considered adequate, but the rather high contents of Sr and U, especially in the Kenge Ungi soil may be problematic. Although the composition of the soils suggests substantial fertility and resilience, the lack of K-containing weatherable minerals (silicate minerals) is in line with a very low K (and low Mg) content and explains why fertilization may be needed to sustain future cultivation of these special soils. Due to a possible low bioavailability of Fe, Mn and maybe other micronutrients at the circumneutral pH of these carbonatic/phosphatic soils as well as the rather high contents of Sr and U, it may be recommended to test element availability using appropriate chemical soil tests supplemented by plant experiments to ensure safe and sustainable (optimal) soil use. However, according to the local farmers, the Malanga, Kenge Toaha and Kenge Ungi soils are considered well suited for production of the preferred crops.     

Spatial variation of tracer distribution in a structured clay field soil

Within the sensitive soils of the River Oder Basin (E Brandenburg, Germany), chloride‐tracer transport was studied with respect to soil‐surface conditions of the well structured clayey topsoil (disturbed vs. undisturbed) and irrigation mode (flooding vs. sprinkling). The spatial variation of chloride and dye distribution was sampled in a regular grid within different soil depths. Different methods were used for the analysis of spatial heterogeneity: a heterogeneity index HI derived from fitting parameters of the cumulative distribution function, semivariogram analyses to identify the spatial representativity of observations and to classify the spatial variation, and Spearman's rank correlations to examine the spatial similarity of tracer distribution across different soil depths. Soil aggregation was obvious throughout the soil profile, and macropores and fractures were preferred flow paths for the tracer. Flood irrigation resulted in more “uniform” distribution than sprinkling did. However, preferential flow was identified for all treatments, where, once established below the surface layer, flow paths led to heterogeneity indices manifesting nonuniform flow and reduced lateral mixing between macropores and soil matrix. Within the flooded plot, spatial structure of chloride concentration was moderate unlike the strongly structured variation within the sprinkled plots. For purposes to generalize and to assess regional risk of the water and solute transport within the topsoil of the River Oder Basin, spatial autocorrelation ranges of about 15 cm should be considered and included into concepts of soil protection and land‐use management, soil‐sampling strategies, or modeling approaches.     

Biodegradation of Monoethanolamine,Ethylene Glycol and Triethylene Glycol in Laboratory Bioreactors

The release of alkanolamines and glycols into the subsurface soils poses a potential hazard to the environment through impacted soil and groundwater. This study investigated aerobic and anaerobic biodegradability of monoethanolamine (MEA), ethylene glycol (MEG) and triethylene glycol (TEG). Significant levels of MEA (31 000 mg/kg), MEG (500 mg/kg) and TEG (2100 mg/kg) were successfully aerobically biodegraded in bioreactors. The aerobic slurry experiments suggested initial phosphate (P) limitation, as biodegradation rates increased by one order of magnitude after phosphate addition. Anaerobic decay of MEA, MEG and TEG was unaffected by P-addition. MEA, MEG and TEG degradation products such as acetate, ethanol and ammonium at about 75 000 mg/kg, 8100 mg/kg and 8800 mg/kg degraded completely and did not prevent aerobic biodegradation. This study confirms proposed biodegradation pathways of MEA, MEG, TEG and their breakdown products in natural soil and groundwater using indigenous microbes. Levels of contamination studied here are significantly higher than previously reported.