Uncleared Plots Research Articles

Increased diversity of the species pool via seeding augments establishment of native species in experimental vacant‐lot restorations

AbstractQuestionThe harsh geophysical template characterized by the urban environment combined with people's choices has led ecologists to invoke environmental filtering as the main ecological phenomenon explaining urban biodiversity patterns. Yet, dispersal is often overlooked as a driving factor, especially on expanding vacant land. Does overcoming dispersal limitation by seeding native species in urban environments and increasing the functional or phylogenetic diversity of the seeding pool increase native plant species diversity and abundance in urban vacant land?LocationBaltimore, Maryland, USA.MethodsWe took an experimental approach to learn how different dimensions of plant biodiversity within a regional species pool augmented via seed additions, can explain variation in community structure over a three‐year period. Vacant lots were cleared and manipulated with seeding treatments of high or low phylogenetic and functional diversities from a pool of 28 native species. Establishment success, total native cover and native‐species richness were followed and compared to cleared, unseeded control lots as well as unmanipulated lots.ResultsSeeding increased native plant abundance and richness over uncleared plots, as well as cleared and unseeded control plots. Phylogenetically diverse seed mixtures had greater establishment success than mixtures composed of closely related species. Diversifying seed mixtures increased the likelihood of including species that are better able to establish on vacant land. However, there were no differences in varying levels of either functional or phylogenetic diversity.ConclusionsAugmenting the regional species pool via diverse seed mixtures can enhance native plant cover and richness under the harsh environmental conditions conferred by land abandonment.

Feasible or foolish: Attempting restoration of a Parthenium hysterophorus invaded savanna using perennial grass seed

The annual herb Parthenium hysterophorus L. (Asteraceae), remains one of Southern Africa's most significant invasive weeds, commonly invading savannas, and their rangelands, causing severe losses to agriculture, livestock production and native biodiversity. Previous studies have suggested that perennial grasses may act as useful competitive species, capable of suppressing the growth and invasion of P. hysterophorus. To explore this, a total of 48 plots were established within an invaded savanna, using a randomised block design, and included treatments with and without the clearing of P. hysterophorus, as well as with and without the sowing of native perennial grass seed (Anthephora pubescens, Chloris gayana, Cynodon dactylon, Digitaria eriantha, Eragrostis curvula, Panicum maximum and Themeda triandra). Plots were assessed yearly in terms of P. hysterophorus density and growth as well as grass species composition, basal cover, and biomass over a three-year period. Clearing alone was found to exacerbate invasion, increasing P. hysterophorus density by 40%. Whereas the sowing of grass seed, in both the cleared and uncleared plots, increased the abundance of perennial grass species by 28%, subsequently reducing the size, reproductive output and density of P. hysterophorus over the three years. In addition, these sowing efforts contributed towards partial restoration of the plots, enhancing grass basal cover by ~15% and biomass production by 17%. Overall, this research suggests that sowing of native grass species, with or without clearing, may be a useful supplementary control or restoration tool towards the long-term management of P. hysterophorus invasions in managed savannas and rangelands in Southern Africa.

Reduced soil respiration beneath invasive Rhododendron ponticum persists after cutting and is related to substrate quality rather than microbial community

Invasive plants depositing recalcitrant, polyphenol-rich leaf litter may alter decomposition dynamics, leading to an accumulation of soil organic matter. Removing invasives is critical in restoring native habitats, but our understanding of its impacts upon soil processes remains limited. Here, we test the hypothesis that clearing of Rhododendron ponticum leads to increased soil respiration, at a site within Snowdonia National Park, Wales, UK. Soil samples were collected, and soil respiration was monitored over 32 weeks on plots cleared of R. ponticum, plots infested with R. ponticum which were left uncleared, and uninvaded plots of native vegetation. Soil respiration was significantly higher in native vegetation plots, relative to uncleared plots. Clearing R. ponticum led to a short-term (<four weeks) increase in soil respiration relative to uncleared plots and was related to elevated soil temperature post-clearance. However, this respiration response was transient, with no significant difference between cleared and uncleared plots over the whole growing season (32 weeks). Declining soil respiration responses to soil warming have been attributed to altered soil microbial communities and substrate limitation. Analysis of microbial phospholipid fatty acids (PLFAs) detected no differences among cleared, native and uncleared plots post-clearance. However, Fourier-transform mid-infrared spectroscopy detected a decline in organic matter aromaticity over the growing season in the native and uncleared plots, whilst there was no change in the cleared plots. The findings show that despite a pulse in soil respiration during the initial four weeks post-clearance, R. ponticum litter and associated soil organic matter in cleared plots continued to decompose at a similar rate to uncleared plots over the whole growing season. This was likely a result of substrate limitation and altered soil organic matter composition following R. ponticum clearing, with labile carbon becoming depleted and an enrichment of more recalcitrant aromatic structures.

Insights into the dynamics of Boletus edulis mycelium and fruiting after fire prevention management

Boletus edulis Bull. is among the most valuable mushroom species worldwide. Cistus ladanifer L. scrublands host an extraordinarily high production of this profitable fungus. Its fructification varies greatly among years depending on factors such as stand age and density along with climatic variables. Important information is missing, however, on the dynamics of this species, particularly at the below-ground level and its correlation with sporocarp production. We sought to improve understanding of the ecology of this species that could allow prediction of B. edulis production using faster and less expensive procedures under forest management scenarios.Under the hypothesis that fire prevention management influences the presence of Boletus edulis mycelium and thus, the production of sporocarps, different management treatments were performed. These consisted of different levels of fuel reduction: (controlled burning, total clearing, 50% clearing, and uncleared), established in scrublands of different ages/origins (young-fire, young-cleared and senescent). To analyse B. edulis mycelium in the soil, soil samples were taken at three different times during the year, quantifying B. edulis DNA by real-time PCR using specific primers and Taq-man probes. To analyse B. edulis production, all sporocarps were collected and weighed on a weekly basis during the autumn season.Our results confirmed that management significantly influence quantities of B. edulis mycelium in soil and sporocarp yields that were highest in the uncleared plots and lowest in total clearing plots. Fifty percent clearing plots showed a significant recovery for both mycelium quantity and B. edulis yields after three years.Concerning the origin of the stand, young-fire plots had the highest amounts of B. edulis mycelium in the soil. A positive correlation was detected between B. edulis fresh weight production and the amount of mycelium in the soil suggesting the ability to predict B. edulis yields using faster and less costly methods than weekly inventories carried out for several autumn seasons.

Ecological Requirements of the Zapata Bladderpod Physaria thamnophila, an Endangered Tamaulipan Thornscrub Plant

Abstract A significantly greater proportion of brush-cleared plots had the Zapata bladderpod Physaria thamnophila than did uncleared plots. However, density of P. thamnophila, especially density of seedlings, was correlated positively with a canopy-cover index on the four sites studied. These apparently contradictory results may have been due to facilitation of seeds and seedlings of P. thamnophila by litter. Litter, normally associated with shrubs, was spread across the site by brush-clearing. Beneficial effects of brush-clearing (without disruption of soil) on P. thamnophila suggest that fire may have been part of its environment in the past. The four populations of P. thamnophila that we studied fluctuated widely in size and in rates of reproduction and establishment from year to year.

Relationship Between Fecal Pellet Counts and Snowshoe Hare Density in Western Wyoming

ABSTRACT Snowshoe hares (Lepus americanus) are an important prey species for Canada lynx (Lynx canadensis) and are considered critical for lynx population persistence. Determination of snowshoe hare distribution and abundance is needed by land management agencies for lynx conservation. An accepted approach for estimating snowshoe hare abundance is the use of fecal‐pellet plot counts. Locally derived regression equations are preferred for accurate calibration of pellet counts to snowshoe hare density due to local differences in pellet deposition and decomposition. We used linear regression to examine correlations between snowshoe hare density, as determined by mark–recapture estimates, and pellet plot counts on both uncleared plots and annually cleared plots on the Bridger‐Teton National Forest, western Wyoming, USA. We found significant correlations between snowshoe hare density estimates and fecal pellet counts for both uncleared and annually cleared pellet counts; however, the relationship was stronger (higher r) when using pellet counts from annually cleared plots. In addition, we found that adjusting the buffer size by omitting hard habitat edges (not used by hares) around trapping grids improved correlations between snowshoe hare density and fecal pellet counts for both uncleared plots and annually cleared plots. Though precision is sacrificed when using uncleared plots, they may be useful as a coarse index of habitat use by snowshoe hares. Our derived regression equations may be useful to identify important foraging habitat for Canada lynx in western Wyoming. Land managers responsible for conserving snowshoe hare habitat in western Wyoming may use these equations to monitor changes in hare populations among habitats and during prescribed management actions.

Soil respiration rate and its sensitivity to temperature in pasture systems of dry-tropics

Tree clearing is a topical issue the world over. In Queensland, the high rates of clearing in the past were mainly to increase pasture production. The present research evaluates the impact of clearing on some soil biological properties, i.e. total soil respiration, root respiration, microbial respiration, and microbial biomass (C and N), and the response of soil respiration to change in temperature. In-field and laboratory (polyhouse) experiments were undertaken. For in-field studies, paired cleared and uncleared pasture plots were selected to represent three major tree communities of the region, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared sites were chosen to represent three different time-since-clearing durations (5, 11–13, and 33 years; n=18 for cleared and uncleared plots) to determine the temporal impact of clearing on soil biological properties. Experiments were conducted in the polyhouse to study in detail the response of soil respiration to changes in soil temperature and soil moisture, and to complement in-field studies for estimating root respiration. The average rate of CO2 emission was 964 g CO2/m2/yr, with no significant difference (P<0.05) among cleared and uncleared sites. Microbial respiration and microbial biomass were greater at uncleared compared with those at cleared sites. The Q 10-value of 1.42 (measured for different seasons in a year) for in-field measurements suggested a small response of soil respiration to soil temperature, possibly due to the limited availability of soil moisture and/or organic matter. However, results from the polyhouse experiment suggested greater sensitivity of root respiration to temperature change than for total soil respiration. Since root biomass (herbaceous roots) was greater at the cleared than at uncleared sites, and root respiration increased with an increase in temperature, we speculate that with rising ambient temperature and consequently soil temperature, total soil respiration in cleared pastures will increase at a faster rate than that in uncleared pastures.

Impacts of habitat disturbance on termites and soil water storage in a tropical Australian savanna

This study examines changes in the abundance and diversity of soil macroinvertebrate taxa and soil water storage across different disturbance treatments in a tropical savanna woodland in northern Australia. Nine plots representing three habitat disturbance treatments (uncleared savanna woodland; 25-year-old regrowth following past clearing; cleared areas) were sampled for macrofauna using soil pits in April 2003. Sub-surface soil moisture (0–0.4 m) was measured at 0.1 m intervals over the 2002/2003 wet season. Termites represented 55% of total individuals sampled. Abundance of soil macrofauna was greatest in uncleared plots and lowest in cleared plots, with the latter treatment also having the lowest taxon diversity. Mean abundances of termites, earthworms and ants were greatest in uncleared treatment plots. Five termite species from four genera were present, with Microcerotermes nervosus constituting 47% of termite species identified. Of the wood-, grass- and polyphagous-feeding termites present, wood-feeding species were restricted to uncleared treatment plots and grass-feeders to regrowth treatment plots. A shift in termite nesting habits from epigeal to hypogeal was observed from uncleared to cleared treatments. Soil water storage was lowest in the dry season and highest during the monsoon, and varied significantly across habitat disturbance treatments at the start and end of the wet season. Cleared plots were least effective in the capture of the first wet season rains, and uncleared treatment plots showed the greatest capacity to retain soil water during the transition from wet to dry season. The negative effects of habitat disturbance on soil water storage may have been partially mediated by the observed changes in soil macrofauna, especially termites.

DENSITIES AND COVER DATA FOR INTERTIDAL ORGANISMS IN THE GULF OF MAINE, USA, FROM 2003 TO 2007

Experimental clearings in macroalgal (Ascophyllum nodosum) stands were made in 1996 to determine if mussel beds and macroalgal stands on protected intertidal shores in New England represent alternative community states. Uncleared control plots and four sizes of circular clearings, which mimicked ice scour events, were established in A. nodosum stands at 12 sites on Swan's Island, Maine, USA. The purpose of this data set is to provide access to data on densities and percent cover in the 60 experimental plots from 2003 to 2007 and to update data from 1996 to 2002 that are already published in Ecological Archives. Data include densities of mussels (Mytilus edulis and Modiolus modiolus), an herbivorous limpet (Tectura testudinalis), herbivorous snails (Littorina littorea, Littorina obtusata), a predatory snail (Nucella lapillus), a barnacle (Semibalanus balanoides), and fucoid algae (Ascophyllum nodosum and Fucus vesiculosus), and percent cover by mussels, barnacles, fucoids, and other sessile organisms.

ASSESSMENT OF POTENTIAL BIAS WITH SNOWSHOE HARE FECAL PELLET-PLOT COUNTS

The fecal pellet-plot method has been used extensively for snowshoe hare (Lepus americanus) population studies across the species' range, but potential biases associated with the technique have not been addressed adequately. We studied hare pellet-plots in northern Idaho to quantify pellet decomposition rates across environmental gradients, and conducted feeding trials on captive hares to assess the role of diet on pellet production rates. We found that across our study area pellet numbers tended to be higher on plots with high vegetative cover, which likely was a reflection of hare habitat choice rather than lesser pellet decomposition in such habitat. A pellet decomposition experiment indicated that pellet persistence was negatively related to moisture level, and that pellets produced by hares during summer decomposed more quickly than those from winter. We found that only 19% of fecal pellets collected from plots located across northern Idaho were produced by hares during winter. There was a correlation between pellet numbers from plots that were pre-cleared 1 year earlier and estimated numbers of hares on 6 study areas. A similar correlation was lacking for pellet counts from uncleared plots, implying that hare population estimation via pellet-plot counts should involve plot pre-clearing. In captive studies, juvenile hares produced slightly fewer pellets per day per gram of food ingested than adults, but pellet production was similar across diets comprised of 10 different browse species. We conclude that for our study area the fecal pellet-plot method may be subject to notable pellet decomposition bias, and therefore recommend that use of the method elsewhere across the species' range be preceded by assessment of both the pellet-hare density relationship and pellet decomposition rates across habitats.

Snowshoe hare pellet-decay rates and aging in different habitats

Snowshoe hare (Lepus americanus) pellet surveys are an efficient tool for monitoring population trends, but there is no standard methodology used to conduct surveys. To assist researchers in developing protocols, we evaluated pellet-decay rates and aging in 3 snowshoe hare habitat types in Alaska during the peak and decline of the hare population from 1999–2002. We found significant differences in decay rates among habitat types and recommend measuring decay rates if pellet counts are to be compared among habitats or regions. Our experiments with known-age pellets indicated that pellets could not be aged reliably, but results from side-by-side comparisons of survey methods provided contrary evidence. Counts from uncleared plots, in which observers subjectively decided whether pellets were “new” (<1 year old), were not statistically different from counts on annually cleared plots. We evaluated 4 methods for conducting pellet surveys: 1) cleared plots with counts of “new” pellets; 2) cleared plots with counts of all pellets; 3) uncleared plots with counts of “new” pellets; 4) uncleared plots with counts of all pellets. Annual trends in pellet counts were similar using the first 3 methods, but counts from method 4 were inflated in 2002 due to a high prevalence of “old” pellets. We conclude that cleared plots are preferable to uncleared plots, and we suggest that using subjective criteria to age pellets may be useful if tallies are kept of both “new” and “old” pellets for each plot.

Butterfly diversity and silvicultural practice in lowland rainforests of Cameroon

Butterfly diversity and abundance were sampled across eight 1-ha silvicultural treatment plots in southern Cameroon. The plotsincluded a cleared and unplanted farm fallow, cleared and replanted forestplots, and uncleared forest plots. The replanted plots were line-planted withTerminalia ivorensis, but differed in the degree and methodof clearance. A total of 205 species of butterflies were collected over twodifferent seasons. Several sampling methods were used, including hand collecting andbaited canopy traps. Sites with the greatest degree of disturbance andlowest level of tree cover had the lowest number of individuals and species ofbutterflies. The farm fallow had substantially fewer individuals and species ofbutterflies than the other plots. The replanted plots were intermediate betweenthe farm fallow and uncleared forest in terms of abundance, richness andcomposition. With all three forms of multivariate analysis (Morisita similarityindex clustering, detrended correspondence analysis and two-way indicatorspecies analysis) largest differences were found between the farm fallow anduncleared forest plots. The butterfly fauna of the uncleared forest more closelyapproximated that of the manually cleared plot than that of the mechanicallycleared plot. We found that although, in general, young replanted forest plotsare a poor substitute for native forest, they do provide habitat for some forestspecies and that this may increase over time as the plots mature.

The effect of removing shrub cover on annual plants and small mammals in a coastal sand dune ecosystem

Populations of sand-living organisms in Israel have decreased due to the stabilization of the coastal dunes and their massive cover by a few shrub species. This study examined the impact of the removal of the above-ground shrub growth on sand-living (psammophile) annual plants and small mammals. After 3 years, the annual plant composition in the cleared plots was similar to the uncleared plots. However, several species specific to open sandy habitats were more abundant after clearing the scrub. This was expressed in the higher Shannon–Wiener diversity index obtained for the cleared plots. Likewise, the small rodents Mus musculus, Rattus rattus, and the shrew Crocidura russula avoided entering the cleared plots, while Gerbillus andersoni allenbyi (an endemic sand-living gerbil) and the Tristram's jird Meriones tristrami were well established there. The deliberate removal of dense shrub cover is proposed as part of the management of Mediterranean coastal dunes, with the intention of preserving the whole shifting dune ecosystem by cheap means and with lower level of human intervention.

Soil disturbance, flood management, and riparian woody plant establishment in the Rio Grande floodplain

The exotic saltcedar (Tamarix ramosissima) has become the dominant woody plant in many riparian systems in the southwestern United States. We evaluated the effects of saltcedar clearing and overbank river flooding on recruitment of cottonwood (Populus fremontii) and saltcedar vegetation in the Rio Grande floodplain of central New Mexico, USA in 1993 and 1994. Overbank flooding coincided with the natural river hydrograph. After two seasons of growth, cleared areas supported more 1993 cohort cotton-woods and saltcedar than uncleared controlled areas. There were no differences between cleared and uncleared areas for the 1994 cohort after one growing season. Although there was a 2-week difference in the date of peak river flows between 1993 and 1994, similar seedling densities of both species were recorded for both years. The descending limb of the 1993 hydrograph was more gradual than the 1994 hydrograph, however, resulting in a higher survival rate of 1993 seedlings. Soil texture, soil salinity, elevation, and soil moisture data were collected from all plots and compared with seedling densities for each seedling sample date. Elevation and soil moisture indices were the most influential variables on seedling density. Decreasing soil moisture variables resulted in consistent seedling mortality for all species in cleared and uncleared plots for both cohorts. Secondary channels developed as a result of vegetative clearing where natural river fluvial processes provided topographic relief and sediment deposition for seedling establishment. Greater densities of cottonwoods and coyote willows (Salix exigua) were found on these deposits compared with remaining portions of cleared plots. Saltcedar clearing in conjunction with peak river flows in late May or early June encourages recruitment of native riparian plants, particularly along sand deposits created as a result of secondary channel development. Receding flows correlated with a receding water-table level of about 2 cm/day enhances native seedling densities relative to saltcedar.

Limited effects of the sea urchin Echinometra mathaei (de Blainville) on the recruitment of benthic algae and macroinvertebrates into intertidal rock platforms at Rottnest Island, Western Australia

The sea urchin Echinometra mathaei occurs at densities of up to 100 per m 2 on intertidal rock platforms at Rottnest Island, Western Australia. Contrary to expectation, the experimental removal of these urchins from urchin-dominated areas at two sites on the Island produced little evidence to suggest that the presence of E. mathaei was either necessary for or specifically preventing the recruitment of any particular species of macroalga or macroinvertebrate. At Cape Vlamingh where urchins grazed extensively, removal of urchins was followed by a large increase in the cover of non-encrusting algae, which were the same species that occurred in lesser numbers in uncleared plots. At Radar Reef, where grazing was confined to the urchins' individual burrows, removal of urchins had little effect on the cover of the algae. Furthermore, there was no “keystone” effect of urchins on the algal composition at either site, as domination of the understorey by canopy species was prevented by the physical conditions at Radar Reef and the failure of the canopy species to recruit at Cape Vlamingh. The number of recruits of all species of macroinvertebrates was low (<10 per m 2), and there was no difference in the identity of the species that recruited into the cleared and uncleared plots at either site, although the presence of urchins did have an effect on the abundance and spatial distribution of recruits of conspecifics and the limpet Siphonaria zelandica, and on the distribution of adults of the mobile gastropod Turbo intercostalis. With such a limited effect on recruitment, E. mathaei is much less of a controlling factor in this intertidal community than has been reported for other species of sea urchins in subtidal communities. Processes affecting the supply of propagules to these platforms appear to be the more important determinants of community membership and structure.

Persistence of Black-Tailed Deer Fecal Pellets in Coastal Habitats

The persistence of fecal pellets from Columbian black-tailed deer (Odocoileus hemionus columbianus) was determined for 2 levels of 3 environmental factors: moisture, substrate, and canopy. Pellet persistence was least in moist, vegetated forest and greatest in dry, bare cutover. After 1 year, the mean number of pellets remaining in pellet groups on moist sites was between 16 and 48% of the original complement of 50 pellets. On dry sites between 50 and 70% of the pellets were present after 1 year. Similar trends occurred for visibility of pellet groups. After 2 years, 5-25% of the pellet groups were visible at moist, cutover sites, whereas 25-75% of the pellet groups were visible at dry, cutover sites. Rates of change of pellet group visibility indicate that the number of pellet groups counted on uncleared plots represent from 1 to 3 x the number of pellet groups that were deposited the previous year. J. WILDL. MANAGE. 51(1):33-37 Pellet group surveys are an established method for studying ungulate density in North America. There are, however, disagreements about the utility of pellet group counts (Collins and Urness 1981, Leopold et al. 1984). The assumptions made to interpret pellet group data are reviewed by Robinette et al. (1958) and Neff (1968) who evaluated pellet count techniques and offered improvements to statistical design. Assumptions made to interpret pellet counts (Neff 1968) are violated for some conditions, thereby invalidating results. Persistence and visibility of pellet groups are factors affecting counts (Wallmo et al. 1962, Fisch 1979) but are rarely attributed much importance. That pellet groups persist for the duration of the deposition period is commonly assumed. Persistence after the deposition period has been addressed by clearing plots or marking existing pellet groups. Methods developed to minimize the influence of differing persistence or visibility, such as clearing plots, are time consuming and sometimes impractical. Although problems are associated with pellet group counts, their simplicity makes them a desirable technique and ensures their continued use by wildlife managers. Our objectives were to measure pellet persistence and visibility in different habitats. Three factors are important in determining pellet group persistence: moisture, substrate, and canopy cover. Evaluation of the direction and magnitude of effects impos d by these factors on pellet group persistence and visibility should allow more reliable interpretation of past results, extension of present findings, and improved sampling design. The B.C. Fish and Wildl. Branch, Can. For. Products Co. Ltd., Univ. British Columbia, and This content downloaded from 157.55.39.177 on Sat, 19 Nov 2016 04:38:53 UTC All use subject to http://about.jstor.org/terms 34 PELLET PERSISTENCE * Harestad and Bunnell J. Wildl. Manage. 51(1):1987 Natl. Sci. and Eng. Res. Counc. provided support through grants to F. L. Bunnell. Simon Fraser Univ. provided computer support.

The effect of attack by Amblypelta cocophaga China (Hemiptera:Coreidae) on growth of Eucalyptus deglupta in the Solomon Islands

AbstractReduction in growth of saplings of Eucalyptus deglupta resulting from die-back caused by Amblypelta cocophaga China was studied in forestry plantations in the Solomon Islands. At a standard spacing of 10 × 3 m, a comparison was made of tree growth and incidence of A. cocophaga attack on saplings planted in strips 2 m wide cut through secondary forest, with those from which all inter-row vegetation was cut back prior to planting. Initially, a greater proportion of trees was infested on the cleared than the uncleared plots, but at the end of the first year, at which time the attack was at its peak, no differences could be detected. From the fifth to the thirteenth month after planting out, uninfested trees on the cleared plots increased in height at an average rate of 60 cm per month. For every week that at least one A. cocophaga was recorded on a tree, this rate was depressed by 1·3 cm. On the uncleared plots, the average rate of increase of uninfested trees was only 42 cm per month and this was reduced by 1·0 cm for every week that an insect was recorded. By the end of the first year, an estimated 37% (in cleared plots) and 41% (in uncleared plots) of the potential stand was rendered useless for future timber production due to A. cocophaga damage. In terms of total stem volume (not log production), about 1 m3/h out of a potential 3 m3/h was lost in the uncleared plots and 0·2 m3/h out of a potential 0·6 m3/h in the uncleared ones. Whilst clearing did not reduce the incidence of A. cocophaga attack, the advantage of clearing in terms of increased tree growth was considerable.

The Lodgepole Pine Zone in Colorado

Vegetation and habitat characteristics are described in lodgepole pine forests on the east slopes of the Colorado Front Range where invasion by Douglas fir, subalpine fir, or Engelmann spruce has not occurred after 65-100 years of pine dominance. Absolute mortality of Douglas fir seedlings on plots cleared of pine litter was observed in 1967, and absolute mortality on uncleared plots was observed in 1966 and 1967. The lack of advanced reproductive stages of trees normally considered climax in adjacent Douglas fir and Spruce-Fir forest zones suggests that a lodgepole pine zone can be recognized between these other zones. Stands of lodgepole pine occurring on deep soils and normal relief within this zone may be climax or in a prolonged seral stage under present environmental conditions.