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The Swiss National Forest Inventory (NFI) is expected to provide reliable data about the current state of the Swiss forests and recent changes. Since the first Swiss NFI (1982-1986) a deadwood assessment has been part of the inventory. However, the definition of deadwood used was restricted and only parts of the total deadwood volume were assessed. A broader definition was therefore used in the second NFI (1993-1995) and coarse wood debris (CWD) was also assessed using line intersect sampling in the third NFI (2004-2006). This paper discusses the development of the definition of deadwood from the first to the third Swiss NFI, as well as the tally rules and estimators used in assessing deadwood in the ongoing third NFI. Different definitions of deadwood were applied in two Swiss regions and the resulting volume estimates were compared. The definition of deadwood appears to be crucial for the estimate of deadwood volumes, which were significantly underestimated in the first and second Swiss NFI. The minimum diameter and other limits applied must be chosen with special care. Up to 30 m³/ha of deadwood was found in Swiss forests varying with the region. There was little evidence of significant correlations between deadwood volume and such forest parameters as management, site or stand attributes. The proposed target values for the volume of deadwood have been generally reached, whereas the number of snags per hectare has not.

Methiozolin is an isoxazoline herbicide that selectively controls annual bluegrass in cool-season turf and may control roughstalk bluegrass, another weedy Poa species that is problematic in many turfgrass systems. However, the majority of research to date is limited to evaluating methiozolin efficacy for annual bluegrass control in creeping bentgrass putting greens. Research was conducted comparing various application regimes of methiozolin and other herbicides for long-term roughstalk bluegrass control in creeping bentgrass golf fairways. Methiozolin-only treatments did not injure creeping bentgrass or reduce normalized difference vegetative index (NDVI) at 2 golf course locations based on 20 evaluation dates over a 2.5-yr period. The 2.5-yr average turf quality generally declined as roughstalk bluegrass control increased due to transient turf cover loss. At 1 yr after last treatment, methiozolin at 1500 g ai ha-1 applied four times in fall reduced roughstalk bluegrass cover 85%. This was equivalent to methiozolin at 1000 g ha-1 applied four times in fall, but greater than low rates of methiozolin applied four times in spring or twice in fall and spring. Amicarbazone, primisulfuron, and bispyribac-sodium alone either did not effectively reduce roughstalk bluegrass cover, or did so at the expense of increased creeping bentgrass injury. Results of this study suggest that methiozolin alone or tank-mixed with amicarbazone or primisulfuron is an effective long-term approach for selectively controlling roughstalk bluegrass in creeping bentgrass. Nomenclature: Amicarbazone; bispyribac-sodium; methiozolin; 5-(2,6-difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1; 2-isoxazoline; code names: EK-5229, SJK-03, and MRC-01, prmisulfuron, annual bluegrass, Poa annua L.; roughstalk bluegrass, Poa trivialis L.; creeping bentgrass, Agrostis stolonifera L.

A new method for sampling coarse woody debris (CWD) is presented, based on relascope sampling of CWD midpoint diameter. In this method, CWD is included in a sample if the angle subtended by the midpoint diameter viewed from plot center is greater than the critical relascope angle. The method is therefore referred to as diameter relascope sampling (DRS). Other methods for sampling CWD are reviewed and compared with DRS using sampling simulations and statistical power calculations. These are fixed area sampling, line intercept sampling, and point relascope sampling. DRS is shown to be have greater statistical power per unit sampling effort than other methods when CWD diameter and length are linearly or allometrically related, but results can vary with the diameter-length relationship employed. The relative benefits of different methods for sampling CWD are discussed.

Coarse woody debris (CWD) plays an important role in many terrestrial and aquatic ecosystem processes. In recent years, a number of new methods have been proposed to sample CWD. Of these methods, perpendicular distance sampling (PDS) is one of the most efficient methods for estimating CWD volume in terms of both estimator variance and field effort. This study extends the results for PDS to the estimation of the surface area of CWD. The PDS estimator is also compared to two line intersect sampling (LIS) estimators, where one of the LIS estimators requires the measurement of surface area on each log and the other estimates surface area using a single measurement of log circumference at the point of intersection between the log and the line. The first estimator approximates the true surface area by assuming either a conic or parabolic stem form and requires measurements of the end diameters of each log, which is more time consuming than a single measurement. The performance of the three estimators was compared using a computer simulation. The results of the simulation indicate that, given the same number of pieces of CWD sampled at each point, equal variances can be achieved with PDS using sample sizes that range from about 10% to in excess of 100% the size of a comparable LIS estimator. When the LIS estimators were compared, the estimator that required the measurement of surface area was only about 3%-6% more efficient than the alternative estimator, but the bias associated with assuming a conic or parabolic stem form ranged from roughly 5% to 15%. We conclude that PDS will generally outperform either of the LIS estimators. Another important conclusion is that the LIS estimator based on a measured surface area is likely to have a higher mean squared error than an LIS estimator that employs a single measurement of circumference. Thus, LIS sampling strategies that require the least amount of field work will often have the smallest mean square error.

Spatial patterning in the disturbance regime of a forest affects the vegetation dynamics. Therefore, the distribution of canopy gaps was examined in detail for a subalpine Abies-Picea forest in the northeastern United States. Gaps were not randomly distributed. The fraction of forest area in gaps and the abundance of gaps varied significantly with topographic position, elevation, and slope percent. On average, 15 % of the forest was influenced by gaps, but the gap fraction was greater near ridges (23 %) and near streams (27 %) than on the backslope (13 %). Also, gaps were larger and more abundant near streams and ridges. Gap fraction varied with elevation as well: more of the forest was disturbed at lower and higher elevations than at mid-elevations. Significantly more of the forest on steep slopes (≥ 30 %) was under gaps. As a result of this patterning, some parts of the Abies-Picea forest were predictably more disturbed than others. A remaining question is whether this patterning is sufficient to influence the regeneration environment and thus forest composition.

This chapter focuses on a relatively simple type of line intersect sampling (LIS) protocol that is readily adaptable to many forest inventory situations, so that the assumptions, field protocols, and estimating equations can be kept simple and clear. LIS is actually a probability proportional to size (PPS) design, and samples pieces of downed wood with probability proportional to their length. Moreover, the point on a piece where the sample line crosses is randomly selected along the length of the piece, and this offers opportunities to estimate properties such as volume per unit area with simplified measurements, and without any need to assume a specific taper or volume equation. One shortcoming of PPS sampling approaches such as LIS, point relascope sampling (PRS), and transect relascope sampling (TRS) is that sampling is proportional to a size that is correlated with volume, weight, and carbon or nutrient content but is not, in itself, of significant practical interest.

The spatial distribution of root length density (RLD) is important for water and nutrient uptake by plants and biomass allocation in the soil. Experimental root assessment is, however, mostly based on methods that encompass only small fractions of the soil volume. The aim of this study was to characterize the three dimensional (3D) spatial distribution of RLD in the soil of a maize crop for plots of 37.5 and 75 cm row spacing. At each plot, a 3D soil monolith of 70 x 40 x 30 (=84,000) cm³ was completely sampled in form of 84 cubic samples of 10 cm edge length. Roots were washed from the soil and RLD was determined using the line intersect method. In 2004, mean RLD values were 0.41 cm cm⁻³ for narrow and 0.34 cm cm⁻³ for wide row spacing at row closure (55 days after planting; DAP) and 0.74 cm cm⁻³ (1.37 cm cm⁻³ in 2003) for narrow and 0.77 cm cm⁻³ (0.96 cm cm⁻³ in 2003) for wide row spacing at tasseling (104 DAP). The CV values for RLD of 48% to 72% in 2004 were first higher for wide than for narrow row spacing but at the later growth stage (tasseling) lower for wide than for narrow. For individual vertical soil slices, CV values for RLD were about 40-60%, irrespective of the orientation of the slice. The results suggest that RLD was related mainly to the spatial location and the plant row structure, and not governed unambiguously by SBD or SWC. The spatially distributed maize root data suggest that variability of RLD parallel to plant rows is not negligible. Any simplified use of 1D or 2D vertical samples at separate locations may lead to erroneous estimations of RLD profiles.

Volume or biomass estimates of downed woody debris are crucial for numerous applications such as forest carbon stock assessment, biodiversity assessments, and more recently for environmental evaluations of biofuel harvesting practices. Both fixed-area sampling (FAS) and line-intersect sampling (LIS) are used in forest inventories and ecological studies because they are unbiased and accurate methods. Nevertheless, most studies and inventories take into account only coarse woody debris (CWD, >10 cm in diameter), although fine woody debris (FWD) can account for a large part of the total downed biomass. We compared the LIS and FAS methods for FWD volume or biomass estimates and evaluated the influence of diameter and wood density measurements, plot number and size. We used a Test Zone (a defined surface area where a complete inventory was carried out, in addition to FAS and LIS), a Pilot Stand (a forest stand where both LIS and FAS methods were applied) and results from 10 field inventories in deciduous temperate forest stands with various conditions and amounts of FWD. Both methods, FAS and LIS, provided accurate (in trueness and precision) volume estimates, but LIS proved to be the more efficient. Diameter measurement was the main source of error: using the mean diameter, even by diameter class, led to an error for volume estimates of around 35%. On the contrary, wood density measurements can be simplified without much influence on the accuracy of biomass estimates (use of mean density by diameter class). We show that the length and number of transects greatly influences the estimates, and that it is better to apply more, shorter transects than fewer, longer ones. Finally, we determined the optimal methodology and propose a simplification of some measurements to obtain the best time-precision trade-off for FWD inventories at the stand level.