Partial Harvesting Research Articles

Conifer Regeneration After Experimental Shelterwood and Seed-Tree Treatments in Boreal Forests: Finding Silvicultural Alternatives.

Forest regeneration is a key element in achieving sustainable forest management. Partial harvest methods have been used extensively in temperate broadleaf and mixedwood ecosystems to promote regeneration on poorly stocked sites and to maintain forest composition and productivity. However, their effectiveness in promoting conifer establishment has yet to be demonstrated in unmanaged boreal forests, especially those dominated by black spruce (Picea mariana (Mill.) BSP) where constraints for regeneration differ from those found in more meridional regions. We aimed to evaluate conifer seedling density and dimensions, 10 years after the onset of a gradient of silvicultural treatments varying in harvesting intensities, and to identify the critical factors driving the regeneration process. Study blocks of even-aged black spruce stands in the eastern Canadian boreal forest were submitted to three variants of shelterwood harvesting: a seed-tree harvest, a clear-cut and an untreated control. Shelterwood and seed-tree harvesting were combined with spot scarification to promote regeneration. Shelterwood and seed-tree harvesting produced a density of conifer regeneration sufficient to maintain forest productivity, but they did not promote seedling growth. Black spruce was the predominant species in terms of regeneration density, with proportions 3–5× higher than that for balsam fir (Abies balsamea (L.) Mill.). Ten years after treatment, seed-origin black spruce seedlings were abundant in skidding trails, while layers dominated the residual strips. Balsam fir density was not influenced by treatment nor by tree position relative to skidding trails. Balsam fir and black spruce had different responses to treatment in terms of height and diameter, the former exhibiting a better growth performance and larger diameter in the residual strips. Spot scarification created micro-sites that had a significant impact on the regeneration process. Overall, our results support that shelterwood and seed-tree harvesting combined with scarification enable adequate regeneration in black spruce stands, confirming these treatments as viable silvicultural alternatives to clear-cutting when required by sustainable forest management objectives.

Postoperative motor deficits following elbow flexion reanimation by nerve transfer

We aimed to assess the rate and type of postoperative motor deficits that might be encountered following elbow flexion reanimation using ulnar- and/or median-based side-to-end nerve transfers in patients with brachial plexus injuries. All patients who underwent elbow flexion reanimation between November 2015 and October 2017 at our facility by nerve transfer based on partial harvests of the median and/or ulnar nerves were included. Postoperative clinical assessment was conducted the day after surgery to identify motor deficits in the territory of the harvested nerves. If a clinically noticeable deficit was present, the type and extent of the deficit were noted, and postoperative clinical evaluations were conducted monthly to determine its progression. After reviewing the charts of 27 consecutive patients, 4 patients were found to have a postoperative motor deficit (15%). In all four cases, the deficit was limited to the anterior interosseous nerve (AIN) territory in patients who underwent a double transfer (i.e., ulnar-to-biceps and median-to-brachialis). With clinical impairments of the flexor pollicis longus and/or the flexor digitorum profundus of the index and third fingers initially ranging from grade-0 to grade-3 strength, full recovery to preoperative strength levels occurred in all cases after a mean of 7 months’ follow-up. Transient motor deficits may be observed in the AIN territory following elbow flexion reanimation when a median-to-brachialis nerve transfer is associated with the original Oberlin procedure.

Partial harvesting effects on seedling growth and physiology of three hardwood species in mature pine (Pinusspp., Pinaceae)-hardwood mixtures1

Nonindustrial private forest (NIPF) landowners own a substantial amount of acreage within the southern USA. The NIPF landowners are usually less financially motivated and implement relatively less-intensive management options, such as partial harvesting, to pursue a variety of multiuse objectives. Understanding how developmental processes are influenced by partial harvesting is vital to constructing viable silvicultural prescriptions. Liquidambar styraciflua L., Quercus alba L., and Ostrya virginia (Mill.) K. Koch seedling (10–105 cm tall) growth and physiology were investigated in relation to different gap sizes and within-gap positions in a mixed Pinus L.–hardwood forest. The levels of photosynthetically active radiation that penetrated the overstory conditions allowed shade-intolerant Liquidambar styraciflua to produce greater (mean ± SE) monthly height and groundline diameter growth (12 ± 0.94 cm and 0.2 ± 0.02 cm, respectively) than Ostrya virginia (8 ± 0.87 cm and 0.1 ± 0.02 cm, respectively) and Quercus alba (4 ± 0.51 cm and 0.1 ± 0.01 cm, respectively), which was facilitated, in part, by significantly higher photosynthetic rates (P < 0.01). Solely manipulating the overstory conditions within mature, Pinus-hardwood mixtures may not be adequate for Quercus regeneration in those mixtures and is conducive to Liquidambar styraciflua obtaining a more-dominant canopy position in the future.

Structural Attributes of Old-Growth and Partially Harvested Northern White-Cedar Stands in Northeastern North America

Forestry practitioners often need to identify old-growth stands because of their high conservation value. To identify the structural and compositional characteristics potentially unique to old-growth northern white-cedar (Thuja occidentalis L.) stands, we compared 16 old-growth stands and 17 partially harvested stands in Maine, USA and New Brunswick, Canada. Potential old-growth predictors included common structural metrics such as basal area (BA), quadratic mean diameter (QMD), large tree (≥40 cm diameter at breast height) density, and volumes of coarse woody debris (CWD), along with six structural indices. Using generalized linear mixed-models, we identified two significant structural predictors that differentiate old-growth from partially harvested stands when used in combination: Volume of advanced-decay CWD and live tree QMD. None of the structural indices were useful in distinguishing between old-growth and partially harvested stands, nor did the two types differ with respect to tree species composition. Our results demonstrate that two metrics easily derived from standard inventory data—decayed CWD volume and QMD—effectively characterize the old-growth white-cedar stands sampled in this study. Taken together, these results can improve management decision making for white-cedar, particularly in the context of certification, while also shedding light on the effects of past partial harvesting on current forest structure.

Production method and cost of commercial-scale offshore cultivation of kelp in the Faroe Islands using multiple partial harvesting

The current work aimed to develop a cultivation method for macroalgae that can be applicable and economically profitable in the Atlantic Ocean. An offshore long-line macroalgal cultivation rig was designed by Ocean Rainforest Sp/f, tested in the Faroe Islands from 2010, and found suitable for cultivation in exposed and deep-water locations (water depth > 50 m). The economic risk related to lost cultivation structures was hereafter considered to be low. Saccharina latissima and Alaria esculenta were cultivated in commercial scale (5 km of growth lines). A high cost of seeding material and cost of deployment was reduced by testing multiple partial harvesting. Four non-destructive harvests were carried out in a two-year growth period without re-seeding of lines. In total, 3.2 t dry weight (dw) biomass was harvested and sold to customers within the food and cosmetic industries. The productivity was 1437.5 kg dw ha−1 yr−1 (including handling space). The 10-meter vertical growth lines had an average yield of 0.29 kg dw m−1 per harvest and four partial harvests were made over a 2-year period. An economic analysis showing the cost structure of important aspects of offshore macroalgae cultivation was conducted. The total cost per kg dw of cultivated S. latissima decreased when the number of possible harvests without re-seeding was increased (from € 36.73 to € 9.27). This work has demonstrated that large-scale kelp cultivation is possible using multiple partial harvesting in the Faroe Islands, and highlighted the need for further innovation to lower the cost per unit macroalgal produced.

Small scale fish farming in seasonal ponds in Brazil: technical and economic characterization

The inclusion of aquaculture in household agriculture has been related as an opportunity of product and income diversification as wells as to increase food security for farmers. Small-scale fish production has increased in Brazil, even in regions with a pronounced dry season. However, there is no information about the characteristics and technical and economic viability of aquaculture under these conditions. This study was carried out with the objective to characterize the production of tambatinga (Colossoma macropomum × Piaractus brachypomus) in water deficit conditions in Tocantins State, Brazil. The study revealed that it is technically possible and economically feasible to produce tambatinga in seasonal ponds. Worth noting was the adaptability of the hybrids which showed a suitable growth and tolerance to the poor water quality conditions. However, in order to achieve production success and financial returns, the adoption of the following procedures are suggested: a) fish stocking as soon as the rainy period starts, b) use of larger juveniles to achieve a higher final weight, c) adoption of pond liming and fertilizing practices previous to stocking, d) water quality monitoring, e) evaluate fish growing performance, f) partial harvesting during the production cycle, and g) total harvesting at the end of the rainy season.

Long-term survival of trees retained for hollow-using fauna in partially harvested forest in Tasmania, Australia

Hollow-using fauna are thought to be particularly vulnerable to timber harvesting, and habitat for these species is often managed by retaining single hollow-bearing trees or patches of hollow-bearing trees within the harvested area. This study examined tree retention, survival and use by arboreal mammals in 27 small clumps of trees (0.04–0.21 ha) retained at ten partial harvest sites and 24 clumps of trees in nearby unharvested sites in Tasmania, Australia. Harvested sites were assessed on three occasions (1999, 2005–06 and 2014) and unharvested sites on two occasions (2005–06 and 2014). Of the retained clumps in harvested areas, 96% contained at least two habitat trees at the time of first survey (one year after harvest) which is the minimum required under the Tasmanian Forest Practices Code. Loss of retained trees in clumps between 2005–06 and 2014 was higher in harvested sites (average of 11.7% of all trees and 1.5% of habitat trees per clump) than unharvested sites (average of 2.8% of all trees and 0.3% of habitat trees per clump), but was comparable to or lower than rates of loss in many other studies. Trees were more likely to fall if they were dead and had little burn damage at the time of last survey. Factors found to influence tree death included the interaction between burn damage and the size of the tree, with the likelihood of a heavily burnt, average sized tree dying being twice that of an unburnt tree. Scratch marks from arboreal mammals were more prevalent in large trees with visible hollows, particularly in the clumps in harvested areas. In conclusion, the Tasmanian Forest Practices Code provisions were generally implemented as required and the evidence suggests the retained clumps of trees survive and are effective to some degree at providing habitat and promoting recolonisation by fauna in partial harvest coupes. However, further work is required to assess the adequacy of the clump provisions, when combined with management for other values in production forests, for maintaining hollow-using fauna throughout their range.

TIMBER HARVESTING PATTERNS FOR MAJOR STATES IN THE CENTRAL, NORTHERN, AND MID-ATLANTIC HARDWOOD REGIONS

Timber harvesting is a major disturbance agent influencing the composition and structure of eastern hardwood forests. To better understand timber harvesting practices, we examined roundwood harvesting patterns in 13 eastern states in the Central, Mid-Atlantic, and Northern regions that contained high proportional volumes of hardwood in their forest inventories. Nearly 5400 Forest Inventory and Analysis sample plots in which timber was cut and assumed to be used were examined for the period 2009-2015. Nine patterns based on basal area removed were isolated and defined, of which six were partial removals and three were clear-cuts. Of the patterns observed, four involved primarily hardwoods, three involved primarily softwood, and two were mixed. Large diameter–influenced partial hardwood harvesting practices were found to be predominant in the Central hardwood region, but mixed diameter hardwood and softwood partial harvesting patterns were noted in Wisconsin, Michigan and Maine. Harvesting patterns examined in Pennsylvania and New York appeared to be a transition between the patterns found in the Central and three most Northern states. Large diameter–influenced harvesting also occurred less frequently in the Mid- Atlantic states. Clear-cuts were noted in all states examined but were associated with higher levels of removal in the Mid-Atlantic states. Softwood cuts were more common in the Northern and Mid-Atlantic states and pine thinning cuts were noted in Tennessee, Wisconsin, Michigan, Virginia, and North Carolina. Although this study provides insight into current timber harvesting processes, additional information is needed to determine how timber management practices can be developed to complement the economic considerations associated with harvests.

Susceptibility of Trees to Windthrow Storm Damage in Partially Harvested Complex-Structured Multi-Species Forests

In Canada and elsewhere, logging practices in natural-origin forests have shifted toward retention systems where variable levels of mature trees are retained post-logging to promote a diversity of values. We examine multiple sites that experienced a wide range of prior harvest regimes (0–76% basal area removal) to evaluate how harvest intensity and proximity to a logging-created edge affects susceptibility to windthrow for a suite of tree species in complex-structured mature and old-growth mixed-species stand types in British Columbia. We found no increased susceptibility to windthrow as a function of the level of partial harvesting. We observed a reduced susceptibility to windthrow of smaller trees after partial harvesting. There were clear differences in susceptibility to windthrow among different tree species close to the edge of gaps and small openings (&lt;1 ha in size) created by partial harvesting. Hemlock and redcedar, the two most common trees species, were unaffected by edge environments, whereas the less common conifers and deciduous species were more susceptible to windthrow along partial harvest edges. This suggests tree-marking guidelines should remove the species most prone to windthrow from edges around small openings in these forest types. Our study and others suggest use of retention systems in structurally diverse, multi-species forests does not lead to elevated risk of windthrow, especially if retention levels exceed 20–30%.

Variable-density Retention Promotes Spatial Heterogeneity and Structural Complexity in a Douglas-fir/Tanoak Stand

1. Abstract After harvesting the merchantable conifers decades ago, many secondary forests in northern California regenerated naturally and are now fully stocked with low value hardwoods intermingled with conifers. Partial harvesting to reduce hardwood densities and release conifers is expected to enhance tree vigor and reduce risk of stand-replacing wildfire. Planting a new cohort of merchantable conifers in the understory would enhance structural complexity and future value. A flexible new forest restoration treatment called variable-density retention (VDR) was designed to achieve these objectives. Desirable trees can be kept regardless of their location while the new cohort of conifers is planted among existing trees or in gaps created by removal of patches of undesirable trees. At our study site in northern California, 20 × 20 m (0.04 ha) squares each received one of five treatments (gap, low-/medium-/high-density retention, and no cut). This created a mosaic of different densities. Planted conifer seedlings exhibited variable growth rates. Different stand variables were associated with growth of seedlings of the native coast Douglas-fir ( Pseudotsugamenziesii var.menziesii ) versus coast redwood ( Sequoia sempervirens ) planted outside its natural range. We found no correlation between point counts of overstory basal area and either leaf area index or understory light at each seedling. The VDR system promoted heterogeneity in the spatial pattern of tree locations, restored conifer dominance, and enhanced structural complexity by introducing a new cohort of trees growing at different rates. 3. Keywords: Forest Restoration; Notholithocarpusdensiflorus ; Pseudotsugamenziesii ; Redwood; Sequoia sempervirens ; Variable-Density Thinning; Variable Retention

Is it necessary to use the entire root as a donor when transferring contralateral C7nerve to repair median nerve?

If a partial contralateral C7 nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C7 nerve is used to repair two nerves, both recipient nerves show good recovery. These findings seem contradictory, as the above two methods use the same donor nerve, only the cutting method of the contralateral C7 nerve is different. To verify whether this can actually result in different repair effects, we divided rats with right total brachial plexus injury into three groups. In the entire root group, the entire contralateral C7 root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C7 root was transected and transferred to the median nerve. In the entire root + posterior division group, the entire contralateral C7 root was transected but only the posterior division was transferred to the median nerve. After neurectomy, the median nerve was repaired on the affected side in the three groups. At 8, 12, and 16 weeks postoperatively, electrophysiological examination showed that maximum amplitude, latency, muscle tetanic contraction force, and muscle fiber cross-sectional area of the flexor digitorum superficialis muscle were significantly better in the entire root and entire root + posterior division groups than in the posterior division group. No significant difference was found between the entire root and entire root + posterior division groups. Counts of myelinated axons in the median nerve were greater in the entire root group than in the entire root + posterior division group, which were greater than the posterior division group. We conclude that for the same recipient nerve, harvesting of the entire contralateral C7 root achieved significantly better recovery than partial harvesting, even if only part of the entire root was used for transfer. This result indicates that the entire root should be used as a donor when transferring contralateral C7 nerve.

Effects of partial harvesting on species and structural diversity in aspen-dominated boreal mixedwood stands

Abstract Partial harvesting is thought to result in more structurally diverse forest stands, providing a promising alternative to clearcutting and helping balance timber production and biodiversity conservation. Evidence for this hypothesis is based mostly on understory vegetation communities, with little information available on how partial harvesting affects tree species and structural diversity. In this study, we examined overstory and understory tree species and structural diversity of boreal mixedwoods over 20 years in stands that were unharvested, partially harvested with 40% canopy removal, and clearcut. As expected, clearcutting reduced overstory tree species and structural diversity relative to that of unharvested stands; partial harvesting, however, did not affect neighbourhood (area of 4 trees including one subject tree and 3 neighbours) or stand diversity until after a forest tent caterpillar outbreak that occurred during years 3–5 post-harvesting. The insect-induced trembling aspen (Populus tremuloides Michx.) mortality was higher in the partially harvested than in the unharvested areas decreasing structural diversity at both neighbourhood and stand scales. In comparison, within-stand variations (horizontal complexity or spatial heterogeneity) in neighbourhood diversity values (Shannon species diversity, Shannon structural diversity by 2-m height class, and structural diversity by height variation) increased following the insect outbreak. The post-harvesting temporal dynamics of overstory diversity appeared time dependent and related to harvest removal, forest tent caterpillar defoliation, and growth of released balsam fir (Abies balsamea (L.) Mill.) and aspen regeneration. In all treatments, understory diversity was decreased by clearcutting, which stimulated profuse aspen suckering, and abundant balsam fir regeneration. We conclude that partial harvesting with 40% canopy removal did not significantly change tree species or structural diversity of boreal mixedwood stands in northeastern Ontario, Canada. Changes in overstory diversity following a forest tent caterpillar outbreak, however, suggest that partial harvesting that removes more of the canopy and reduces individual tree dominance may increase species diversity and within-stand structural variation but reduce structural diversity in the overstory.

Long-term effects of single-tree selection on the frequency and population structure of root and butt rot in uneven-sized Norway spruce stands

Abstract The goal of this study was to assess the long-term effects of partial harvesting and supplementary soil scarification on the frequency of root and butt rot in managed uneven-sized Norway spruce stands. Frequency of rot and the population structure of the rot fungi were assessed on 1353 stumps after clear-cutting 21 years after a selection harvesting experiment. The initial experiment was comprised of three harvest strength (low, intermediate and high) of single-tree selection, removing approximately 25, 45 and 65% of the stand basal area. Uncut control plots were established at the same time. Supplementary soil scarification was applied in subplots within the single-tree selection plots, using a medium-sized excavator. After clear-cutting the stumps were analyzed with respect to rot caused by Heterobasidion parviporum, Armillaria spp., Stereum sanguinolentum as well as other rot fungi. Rot caused by Armillaria spp. was most common (8.6% of the stumps), while infection by H. parviporum (2.9%) or S. sanguinolentum (3.0%) was less frequent. The group “other rot” (5.4%) comprised 21 identified taxa, each occurring in 1–15 stumps. Significantly lower rot frequencies were found for the uncut control (16.3%) and intermediate harvest strength (15.7%), compared with low harvest strength (23.6%). A rot frequency of 21.0% was found in the high harvest strength. In two of three harvest strengths, the rot frequency was higher than for the uncut control. As the observed rot frequencies did not increase consistently with increasing harvest strength, the results do not completely support the initial expectations of increased rot after single-tree selection compared with the uncut control. However, since the probability of rot in individual stumps on plots treated with single-tree selection was significantly affected by the distance to the nearest strip road (H. parviporum) as well as dependent on the size of and distance to the nearest stump of trees cut during the experimental harvest (H. parviporum, S. sanguinolentum and total rot), it is evident that the single-tree selection harvesting was partially responsible for some of the observed rot. One of the selection criteria in the initial harvest was a sanitary removal of trees of poor vitality. Varying degrees of sanitation felling may therefore have offset the effects of new infections in wounds or spread of rot fungi through adjacent stumps. Supplementary soil scarification in small gaps of the residual stand had no significant effect on the frequency of rot, suggesting that such treatment may be used to facilitate regeneration in uneven-sized spruce stands on similar sites.

Long-term effects of different forest regeneration methods on mature forest birds

Changes in forest structure that result from silviculture, including timber harvest, can positively or negatively affect bird species that use forests. Because many bird species associated with mature forests are facing population declines, managers need to know how timber harvesting affects species of birds that rely on mature trees or forests for breeding, foraging, and other purposes. We used generalized linear mixed models to determine effects of clearcutting, shelterwood, single-tree selection, and group selection on detection of 18 species of bird associated with mature forests in the Ouachita Mountains of Oklahoma and Arkansas. We surveyed birds for 16 years after harvest. Most species (67%) responded positively to partial harvest that retained some overstory. Less intensive harvests had positive effects on more species and negative effects on fewer species than more intensive harvests, but responses to different treatments varied among species. Five species showed a significant positive response to the most intensive harvest (clearcuts), whereas 2 species showed a negative response. For the second most-intensive harvest (shelterwoods), 7 species showed a significant positive response and 1 species showed a negative response. For the less-intensive harvests, 9 species showed a positive response and no species had negative responses to single-tree selection, whereas 7 species had positive and no species showed negative responses to group selection. Ovenbird (Seiurus aurocapilla) and scarlet tanager (Piranga olivacea) responded negatively to all timber harvests; ovenbird appeared to be particularly susceptible to timber harvest, especially more intensive harvests such as clearcut and shelterwood. A variety of regeneration methods, including some more intensive treatments, along with maintenance of mature forest stands that retain well-developed midstories can be used to maintain the full suite of forest birds.

Partial Costal Cartilage Harvest for Rhinoplasty.

Partial Costal Cartilage Harvest for Rhinoplasty.

Partial Costal Cartilage Harvest for Rhinoplasty.

Partial Costal Cartilage Harvest for Rhinoplasty.

Assessing uncertainty of semi-intensive production of whiteleg shrimp (Litopenaeus vannamei) using partial harvesting programs

We used stochastic models for analysis of the uncertainty involved in semi-intensive production of shrimp in Nayarit state, Mexico, incorporating partial harvests. Analysis of the database showed that increasing the number of harvests was associated with lower stocking densities, the use of larger ponds, longer cultivation periods, larger final weight of shrimp and total production. Equivalence tests showed that the models adequately fitted the primary data. Monte Carlo simulations indicated that improving management by controlling stocking density and the duration of cultivation increased mean production from 981 to 2573 kg/ha (one partial harvest), from 1808 to 3602 kg/ha (two partial harvests) and from 1364 to 3834 kg/ha (three partial harvests), closely approaching the yields reported in the database. When conducting one and three partial harvests, improved management increased production and the certainty in obtaining the crops, as indicated by diminishing values of the coefficient of variation in output probability distributions. When conducting two partial harvests, however, improved management increased yields, but also increased uncertainty because there was a lower control on production parameters. This does not necessarily imply more uncertainty when conducting two harvests, but that at this stage of knowledge, the primary data only allows detecting limited control on production. Results of a preliminary economic evaluation showed that net revenues ranged from USD$ 2361.1–3488.9, the benefit-cost ratio from 1.47 to 1.62 and that the best and worse results were obtained by conducting two and one partial harvests. We conclude that the models are useful for analysing uncertainty of semi-intensive shrimp production incorporating partial harvesting.

The role of advanced regeneration at time of partial harvest on tolerant hardwood stands development

In tolerant hardwood forests of eastern North America, multiple-aged silvicultural systems rely on advanced regeneration to restock the forests. Evaluation of the long-term influence of advanced regeneration on the mature stand is critical for improving management practices. We used a retrospective approach to evaluate the influence of advanced regeneration present at the time of harvest on the current (2012) stand structure and the quality of the growing stock. The study was carried out in partially harvested stands in northwestern New Brunswick, Canada. Trees were sampled from stands with varying degrees of harvest intensities, times since harvest, and site characteristics. Pre-existing advanced regeneration contributed the bulk of trees in the 10–19 cm diameter class across the stands. In stands with low-intensity harvest, the overstory was dominated by sugar maple (Acer saccharum Marsh.) that originated as advanced regeneration. In stands with high-intensity harvest, however, yellow birch (Betula alleghaniensis Britt.) pre-existing advanced regeneration dominated the overstory. The probability of sugar maple and yellow birch being acceptable growing stock peaked at a diameter at breast height (DBH) of about 30–40 cm, while other species combined peaked at a DBH of around 20–25 cm. Our results suggest that harvest intensities based on the dominant advanced regeneration composition and harvesting systems that minimize the risk of physical damage to advanced regeneration are required to achieve partial harvesting objectives.

Effect of partial root-zone irrigation system on seed quality changes of Persian clover (Trifolium resupinatum L.) during seed development and maturation

A field experiment was conducted in Aleshtar, Iran during 2015-16 growing season to evaluate the effect of limited water supply during seed filling period on seed quality changes of Persian clover. The experiment was carried out as a 2×6 factorial with three replications. Irrigation systems including conventional (all root system was irrigated) and partial root-zone irrigation (half of root system exposed to dry soil and the other half was watered) and harvest time (initiated from 10 days after flowering (DAA) and continued on six occasions at 5-day intervals) were used as treatments. Germination percentage, seedling dry mass, electrical conductivity and 1000-seed mass were used as seed quality traits. Seed quality attributes were significantly affected by harvest time and irrigation system, but the interaction of irrigation system × harvest time was not significant. While seed mass and electrical conductivity were not significantly affected by irrigation system, seedling dry mass and germination percentage were reduced under deficit irrigation. Partial root-zone irrigation reduced seed quality, Persian clover needs to experience no water deficit during seed formation and maturation period to produce high quality and quantity seeds.

Partial harvest to reduce occurrence of American beech affected by beech bark disease: 10 year results

Beech bark disease stunts American beech (Fagus grandifolia Ehrh.) to unmerchantable size, and promotes heavy sprouting that outcompetes more desirable sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.). We investigated whether selection harvest targeting removal of large beech can promote maple and birch regeneration while limiting beech competition. Forty plots were established in 2003 in north-western New Brunswick, Canada, with 26 plots harvested and 14 control plots. Harvested plots were re-measured the year after harvest and both harvested and control plots were re-measured 10 years later. Residual tree diameter increment doubled from 0.24 to 0.51 cm/year for maple, and 0.29 to 0.69 cm/year for birch. Harvest did not alter species composition of regeneration, with seedlings comprised of 88 per cent sugar maple in both treatments, 6 per cent beech in harvested plots vs 3 per cent in control plots, and other species ranging from 1 to 5 per cent. There were four times more beech seedlings/ha in control than in harvested plots, but beech still comprised ~60 per cent of the over 2000 stems/ha of saplings in harvested plots. Rapid growth from beech sprouts provided a strong competitive advantage. Residual tree mortality was negligible. Downed deadwood was 58 per cent greater and standing deadwood basal area 71 per cent lower in harvested plots. The harvest maintained strong overstory growth and survival, and did not benefit beech; however, beech remained a dominant species among the larger regenerating cohort. Our results suggest that similar treatments applied to stands with diseased beech can secure adequate regeneration of maple and birch, but will not control profuse regeneration of beech.