Root biomass and shoot to root ratios of perennial forage crops in eastern Canada

Shoot to root ratios (S:R) at peak standing crop are commonly used to estimate the annual crop residue C inputs to the soil from the root biomass left in the soil at harvest. However, root biomass has often been neglected in field studies and estimates of S:R for many commonly grown forage species are not available. Our objective was to determine root biomass and S:R of seven perennial grass species and two perennial legume species under eastern Canadian soil and climatic conditions. Root biomass in three soil layers (0–15, 15–30 and 30–45 cm) was measured shortly after the second harvest in the first (1995) and second (1996) year of production. Two harvests of aboveground DM were taken each year. The total root biomass (0–45 cm) in the second year of production (average of 1437 g m-2) was twice that measured in the first year of production (average of 683 g m-2). This temporal variation was mainly explained by the increase of root biomass in the 0- to 15-cm layer. The proportion of total root biomass (0–45 cm) in the 0- to 15-cm layer increased from 54 to 71% while that in the 15- to 30-cm layer decreased from 37 to 21%; the proportion of roots in the 30- to 45-cm layer remained constant at about 10% in both years. The S:R of alfalfa for the 0- to 15-cm depth was significantly higher than that for most of the grasses. No significant difference in S:R was observed among grass species. Recognizing that S:R may vary with locations and climatic conditions, our results suggest that average S:R of about 1.30 (values ranged from 1.01 to 1.72) in the first production year and 0.60 (values ranged from 0.43 to 0.87) in the second production year could be used as a first approximation to estimate the amount of root biomass left in the soil to a depth of 45 cm from forage crops in eastern Canada. The S:R of forage crops, particularly grasses, were lower than those of annual crops such as small-grain cereals and corn. Key words: Forage, annual C inputs, soil organic matter, root biomass, shoot to root ratios

Comparing nondestructive measures of forage structure and phytomass

Nondestructive radiative transfer and canopy volume methods were compared with the destructive hand-clipping method to determine forage structure and phytomass. On a native range site, fifteen 1-m2 circular plots were located at each of five microsites. On a crested wheatgrass site, thirty 1-m2 plots were located in grazed and in ungrazed areas. At peak standing crop, all plots were measured with a LI-COR Plant Canopy Analyzer to determine leaf area index (LAI), diffuse non-intercepted radiation (DNIR), and mean tilt angle (MTA) of leaves. Then, plants within plots were measured with a ruler to determine volume. Finally, all phytomass within plots was harvested. At the native range site, plant volume was related with LAI and DNIR on four of five microsites. Phytomass was related with LAI and DNIR on two microsites. At the crested wheatgrass site, volume and phytomass were related with LAI, DNIR, and MTA on grazed plots. Only phytomass was related with LAI and DNIR on ungrazed plots. The Plant Canopy Analyzer measures canopy structure and phytomass; it is fast, and its data are transferred directly to a computer. Measuring plant volume is inexpensive and requires minimal training. Determining phytomass by clipping is accurate and requires minimal training, but it is time-consuming and destructive. Key words: Leaf area, canopy, volume, phytomass, radiative transfer

A Possible Relict Population of Mesodesma deauratum (Turton):Bivalvia (Mesodesmatidae) from the Southeast Shoal, Grand Banks of Newfoundland

Extremely dense, localized concentrations of Turton's wedge clam Mesodesma deauratum (Turton) were found in quantitative grab samples on poorly sorted, medium to fine, low organic content sands (total organic carbon < 0.05%) at depths of 44–51 m at a single location on eastern Southeast Shoal of the Grand Banks of Newfoundland. Mean densities ranged from 24 to 5890 individuals∙m−2 and wet weight standing crop from 0 to 21.4 kg∙m−2. A peak standing crop of 69.4 kg∙m−2 was observed in one grab. There was a strong bimodal size distribution (17–27 and 34–56 mm shell length) at the site, but the two size groups never occurred together. Based on external growth checks, the smaller individuals were 4–5 yr old and the larger ones 10 to more than 15 yr. This population is suggested to be a relict of shallow littoral populations which probably existed in the area in the late Wisconsinan glacial period.

Estimating above- and below-ground macrophyte production in Scirpus tidal marshes

Different methods to estimate primary production of Scirpus marshes of the St. Lawrence estuary were compared. Quadrats 25 × 25 cm and cores 10 cm in diameter were found to be the optimal size to sample above- and below-ground standing crops, respectively. Ash content for different plant parts of various species was measured to obtain more accurate estimates of organic matter. A series of allometric equations relating stem height and mass were developed to estimate aerial standing crop from permanent nondestructively sampled plots. This method, however, overestimated standing crop compared with the destructive (harvest) method. The relationship between the above- and below-ground standing crop was also determined for the dominant species and used to predict belowground biomass without destructive sampling. Finally, the Smalley method provided the best estimates of net annual above- and below-ground production when losses attributed to decomposition were not considered. For less intensive studies, however, the methods based on peak standing crop and on the difference between maximum and minimum biomass would yield good approximations of above- and below-ground production.

Effect of Fire on Mixed-Grass Plant Communities in Badlands National Park

This research has the objective of determining the influence of fire on density and peak standing crop of the major grass species of the Badlands National Park mixed-grass prairie. An important goal is to evaluate the potential of prescribed fire for the control of Japanese brome (Bromus japonicus).

Effect of Fire on Mixed-Grass Plant Communities in Badlands National Park

This research has two principle objectives. The first of these is to determine the influence of fire on the density and peak standing crop of the major grass species of the Badlands National Park mixed-grass prairie. The second major objective is to develop burning prescriptions that would favor native plant species over exotics. Preemergent herbicide treatments have been added to provide an alternative method of controlling exotic annual plants.