Bunchgrass Root Abundances and Their Relationship to Resistance and Resilience of Burned Shrub-Steppe Landscape

Invasion of exotic annual grasses (EAG) and increased wildfire have led to an emphasis on managing rangeland plant communities for resistance to invasion and resilience to disturbances. In sagebrush steppe and similar rangelands, perennial bunchgrasses and particularly their roots are hypothesized to be primary contributors to resistance and resilience. We asked how bunchgrass root abundance relates to annual grass invasion and aboveground indicators of bunchgrass vigor that are more readily measured, such as plant height. We used a standardized US Department of Agriculture protocol for root measurement in 445 excavations made in 2016 ? 2018 across a topographically and ecologically varied region of sagebrush steppe burned in the 2015 Soda fire in the Northern Great Basin, United States. Nearly all (99%) bunchgrasses, including seedlings, had deeper roots than the surrounding annual grasses (mean depth of annuals = 6.8 ± 3.3 cm), and 88% of seedlings remained rooted in response to the “tug test” (uprooting resistance to ~ 1 kg of upward pull on shoot), with smaller plants (mean height and basal diameters < 20 cm and < 2 cm, respectively) more likely to fail the test regardless of their root abundance. Lateral roots of bunchgrasses were scarcer in larger basal gaps (interspace between perennials) but were surprisingly not directly related to cover of surrounding EAG. However, EAG cover increased with the size of basal gaps and decreased with greater basal diameter of bunchgrass (in addition to prefire EAG abundance), albeit with a low r². These results provide some support for 1) the importance of basal gaps and bunchgrass diameters as indicators of both vulnerability to annual grass invasion and bunchgrass root abundance and 2) the need for more detailed methods for root measurement than used here in order to substantiate their usefulness in understanding rangeland resistance and resilience.     

Grazing and Songbird Nest Survival in Southwestern Saskatchewan

Grassland songbird populations are declining, and one reason for this might be livestock management practices in native prairies. Although cattle grazing is a common practice in native mixed-grass prairie, little research has been conducted to date to determine its impact on prairie songbird nest survival. During the summers of 2006–2007, we examined the effects of low- to moderate-intensity cattle grazing typical of the region and nest site vegetation structure on nest survival of five species of ground-nesting songbirds in native mixed-grass prairie in southwestern Saskatchewan, Canada. There was no significant effect of grazing (P > 0.10) on Sprague’s pipit (Anthus spragueii), Baird’s sparrow (Ammodramus bairdii), vesper sparrow (Pooecetes gramineus), lark bunting (Calamospiza melanocorys), or chestnut-collared longspur (Calcarius ornatus) nest survival. All five species used denser vegetation than was generally available (P ≤ 0.001). Sprague’s pipit nest survival was negatively correlated with vegetation density (P = 0.055) and litter depth (P = 0.033), and vesper sparrow nest survival was positively correlated with increased visibility from above (P = 0.056), but nest survival of the other species was independent of vegetation structure. Our results suggest that low- to moderate-intensity grazing is consistent with the conservation needs of ground-nesting songbirds in mixed-grass prairies of southwestern Saskatchewan.     

Relationships Among Growth Characteristics of Replacement Angus Heifers

Angus heifers (n = 88) were used over 3 yr to determine the relationship between two sets of traits considered to be indicators of growth. Data were collected at weaning (7 to 8 mo), yearling (10 to 11 mo), andprebreeding (13 to 14 mo) and included BW, hip height (HH), hip width (HW), pelvic height (PH), pelvic width (PW), lactate dehydrogenase (LDH) activity, longissimus area (LA), and backfat thickness (BKFAT). Measurements were grouped into two sets of traits; Set 1 included BW, HH, HW, and LDH activity; Set 2 included PH, PW, LA, and BKFAT. Weight was correlated (P < 0.01) with all variables studied except LDH activity. At weaning, heifers with lower LDH activity had a larger PH just prior to the breeding season. The first canonical variate between Set 1 measurements at weaning or yearling was correlated (r > 0.8; P < 0.01) with Set 2 measurements at prebreeding. Additional linear combinations of Set 1 traits at weaning and yearling were correlated (r > 0.48; P < 0.01) with Set 2 traits at prebreeding. These results suggest that the Set 1 measurements, as early as at weaning, could be used as indicators of Set 2 variables at prebreeding. The canonical coefficients of Set 1 traits were used to rank heifers as either above or below the mean. Ranking heifers based on Set 1 measurements at weaning resulted in a greater (P < 0.01) percentage of heifers calving as 2-yr olds. Correlations between Set 1 and Set 2 traits suggest that external measurements coupled with LDH activity could be used in identifying replacement beef heifers that have larger pelvic dimensions at breeding and a greater frequency of calving as 2-yr olds.     

冰川棘豆生长的生态环境特点

冰川棘豆主要分布西藏阿里地区,该地区所处纬度较低,海拔高,气温低,气温日差较大,降水稀少,空气稀薄、太阳辐射角度大,能接受较多的阳光照射,获得丰富的光能和热量.草原以高寒草原为主,土壤质地粗,土壤养分、含水量低,抗灾能力差,容易引起草场退化,使抗逆性强的冰川棘豆等伴生草种滋生蔓延,成为优势种.     

冰川棘豆生长的生态环境特点

冰川棘豆主要分布西藏阿里地区，该地区所处纬度较低，海拔高，气温低，气温日差较大，降水稀少，空气稀薄、太阳辐射角度大，能接受较多的阳光照射，获得丰富的光能和热量。草原以高寒草原为主，土壤质地粗，土壤养分、含水量低，抗灾能力差，容易引起草场退化，使抗逆性强的冰川棘豆等伴生草种滋生蔓延，成为优势种。     

梅花猪的生态分布及其品种特点

作者介绍了梅花猪的产区范围、产地自然生态条件、品种特点和种质资源现状,提出了梅花猪的开发利用策略,指出梅花猪是我国地方猪种中的一颗璀璨明珠,极具开发利用价值。