Geology topics

Richard M. Engeman

Publications and source records attributed to Richard M. Engeman.

10 recordsLinked to original sources

USGS2023

Burmese pythons in Florida: A synthesis of biology, impacts, and management tools

Burmese pythons ( Python molurus bivittatus ) are native to southeastern Asia, however, there is an established invasive population inhabiting much of southern Florida throughout the Greater Everglades Ecosystem. Pythons have severely impacted native species and ecosystems in Florida and represent one of the most intractable invasive-species management issues across the globe. The difficulty stems from a unique combination of inaccessible habitat and the cryptic and resilient nature of pythons that thrive in the subtropical environment of southern Florida, rendering them extremely challenging to detect. Here we provide a comprehensive review and synthesis of the science relevant to managing invasive Burmese pythons. We describe existing control tools and review challenges to productive research, identifying key knowledge gaps that would improve future research and decision making for python control.

Florida↗

USGS2017

Can we save large carnivores without losing large carnivore science?

Large carnivores are depicted to shape entire ecosystems through top-down processes. Studies describing these processes are often used to support interventionist wildlife management practices, including carnivore reintroduction or lethal control programs. Unfortunately, there is an increasing tendency to ignore, disregard or devalue fundamental principles of the scientific method when communicating the reliability of current evidence for the ecological roles that large carnivores may play, eroding public confidence in large carnivore science and scientists. Here, we discuss six interrelated issues that currently undermine the reliability of the available literature on the ecological roles of large carnivores: (1) the overall paucity of available data, (2) reliability of carnivore population sampling techniques, (3) general disregard for alternative hypotheses to top-down forcing, (4) lack of applied science studies, (5) frequent use of logical fallacies, and (6) generalisation of results from relatively pristine systems to those substantially altered by humans. We first describe how widespread these issues are, and given this, show, for example, that evidence for the roles of wolves ( Canis lupus ) and dingoes ( Canis lupus dingo ) in initiating trophic cascades is not as strong as is often claimed. Managers and policy makers should exercise caution when relying on this literature to inform wildlife management decisions. We emphasise the value of manipulative experiments and discuss the role of scientific knowledge in the decision-making process. We hope that the issues we raise here prompt deeper consideration of actual evidence, leading towards an improvement in both the rigour and communication of large carnivore science.

Food Webs↗

USGS2017

Large carnivore science: non-experimental studies are useful, but experiments are better

We recently described the following six interrelated issues that justify questioning some of the discourse about the reliability of the literature on the ecological roles of large carnivores (Allen et al. In press): 1. The overall paucity of available data, 2. The reliability of carnivore population sampling techniques, 3. The general disregard for alternative hypotheses to top-down forcing, 4. The lack of applied science studies, 5. The frequent use of logical fallacies, 6. The generalisation of results from relatively pristine systems to those substantially altered by humans.

Food Webs↗

USGS1999

Evaluations of plastic mesh tubes for protecting conifer seedlings from pocket gophers in three western states

The efficacy of plastic mesh tubes for protecting conifer seedlings from pocket gopher damage was evaluated on three national forest lands in three states. In each area, cohorts of 640 protected seedlings and 640 unprotected seedlings (3,840 total) were individually monitored for damage, survival, and growth twice each summer for 5 yr after planting. Substantial differences were found between protected and unprotected seedlings for time until occurrence of damage, survival time, proportion damaged and proportion surviving, as well as differences in growth. Over the three forest study sites, the proportion of unprotected seedlings damaged ranged from 60-89%, whereas the proportion of protected seedlings damaged after 5 yr ranged from 18-27%. The proportion of unprotected seedlings that died of gopher damage over 5 yr ranged from 46-64%, versus 1-19% for protected seedlings. Height growth was 25% greater for protected seedlings. Even when only undamaged seedlings were considered, protected seedlings exhibited superior height growth, possibly due to a more favorable microclimate provided by the tubes. These results were reflected in the higher and more uniform stocking rates for protected seedlings.

Western Journal of Applied Forestry↗

USGS1998

Double-stocking for overcoming damage to conifer seedlings by pocket gophers

A 5-yr study was conducted on national forests in Idaho and Oregon to evaluate how doubling the seedling stocking rate of lodgepole pine ( Pinus contorta ) would relate to 5-year survival and the uniformity of distribution of seedlings in the presence of northern pocket gopher ( Thomomys talpoides ) damage. Either 4 or 8 seedlings were planted in 40-m 2 subplots (1000 or 2000 seedlings/ha) and monitored for gopher damage. We found that the number of seedlings attacked by gophers, and consequently, the number of seedlings surviving for 5 years, were directly proportional to the stocking rate, but the consistency of seedling distribution within each site (as measured by the proportion of 40-m 2 subplots with ≥ 2 surviving seedlings) did not double with stocking rate. In some situations, increasing the stocking rate should be considered as a method for overcoming pocket gopher damage.

Idaho, Oregon↗

USGS1998

Damage reduction to ponderosa pine seedlings from northern pocket gophers by vegetation management through grass seeding and herbicide treatment

2,4-D herbicide treatment was applied to 2 treatment units to remove the forbs that are the preferred food of pocket gophers. One of these units also was seeded with grasses prior to the 2,4-D treatment. The effect of 2,4-D and grass seeding plus 2,4-D treatments were compared to an untreated control unit. Long-term monitoring (7 yr) was conducted on the 3 units for vegetative cover (7 yr), pocket gopher activity, and individual survival times and time until gopher damage for 2 cohorts of seedlings (5 and 6 yrs). The 2,4-D treatments greatly reduced vegetative cover of the forbs and seeding increased grass cover on the unit receiving that treatment. Pocket gopher activity was reduced somewhat on the unit receiving only the 2,4-D treatment and more so on the unit receiving grass seeding and 2,4-D, although gophers remained active to some degree throughout the study. Both cohorts of seedlings for both treatments units showed greater average times until gopher damage over seedlings on the control unit. However, seedling survival from all sources of mortality was not positively affected by the treatments for the first cohort of seedlings. The 2,4-D treatment appeared to have killed some of the seedlings; however, seedlings that survived the treatment were in a situation where they were less likely to be damaged by gophers and seemed to have improved growth rates.

Oregon↗

USGS1997

The effects of Vexar® seedling protectors on the growth and development of lodgepole pine roots

The effects on the growth and development of lodgepole pine roots from the Vexar ® tubes used to protect seedlings from pocket gopher damage were studied in the Targhee National Forest, Idaho and the Deschutes National Forest, Oregon. At each site, Vexar-protected and unprotected seedlings, with and without above-ground gopher damage were examined after six growing seasons for root deformities and growth. Undamaged seedlings exhibited greater growth, reflecting the importance of non-lethal gopher damage as a deterrent to tree growth. Protected seedlings with similar damage history as unprotected seedlings had greater root depth than unprotected seedlings, although unprotected seedlings with no above-ground damage generally had the greatest root weight. In general, the percent of seedlings with root deformities was greater for the unprotected seedlings than for the Vexar-protectd seedlings, although this could be largely due to the greater care required to plant protected seedlings. Acute deformities were more common for unprotected seedlings, whereas root deformities with less severe bending were more common for protected seedlings. The incidence of crossed roots was similar for protected and unprotected seedlings on the Deschutes site, where enough occurrences of this deformity permitted analyses. Protected seedlings were similar in root abundance, root distribution, root size and vigor to the unprotected seedlings, with some indication from the Deshutes study site that root distribution was improved with Vexar protection.

Idaho, Oregon↗

USGS1997

Effect of vegetation management for reducing damage to lodgepole pine seedlings from northern pocket gophers

The effects of vegetation management on northern pocket gopher ( Thomomys talpoides ) activity and damage to lodgepole pine ( Pinus contorta ) seedlings were studied using 2,4-D herbicide to alter the habitat. Treatments were applied to a large (8.1 ha) treatment unit and observed effects were compared with an untreated control unit of the same size. The greatly reduced forb and grass cover on the treated unit was associated with a corresponding decrease in pocket gopher activity that persisted for 6 years after initial treatment. Times until seedlings first incurred gopher damage and overall survival of seedlings were greatly increased on the treated unit.

Oregon↗

USGS1995

Vegetation management for reducing mortality of ponderosa pine seedlings from Thomomys spp

The effects of vegetation management on Mazama pocket gopher activity and damage to ponderosa pine seedlings were studied using atrazine herbicide to alter the habitat. Atrazine treatments were applied to a large treatment unit and observed effects were compared to an untreated control unit. The greatly reduced forb and grass cover on the treated unit was associated with a corresponding decrease in pocket gopher activity. Times until seedlings first incurred gopher damage and overall survival of two cohorts of seedlings were greatly increased on the treated unit.

Crop Protection↗

USGS1989

Relationship of roof rat population indices with damage to sugarcane

Roof rats ( Rattus rattus ) cause substantial damage to sugarcane in South Florida (Samol 1972; Lefebvre et al. 1978, 1985). Accurate estimates of roof rat populations in sugarcane fields would be useful for determining when to to treat a field to control roof rats and for assessing the efficacy of control. However, previous studies have indicated that roof rats exhibit trap shyness, which makes capture-recapture population estimates difficult (Lefebvre et al. 1978, 1985; Holler et al., 1981). Until trapping methods are sufficiently improved to allow accurate population estimates, indices of population size that relate to damage need to be developed. The objectives of our study were to examine the relationship of several indices of roof rat populations to the percentage of sugarcane stalks damaged at harvest; to determine which population index would be most useful for sugarcane growers; and to report on a test of several types of live traps for roof rats.

Wildlife Society Bulletin↗