Vegetative and edaphic responses in a Northern mixed conifer forest three decades after harvest and fire: Implications for managing regeneration and carbon and nitrogen pools

Research Highlights: This experiment compares a range of combinations of harvest, prescribed fire, and wildfire. Leveraging a 30-year-old forest management-driven experiment, we explored the recovery of woody species composition, regeneration of the charismatic forest tree species Larix occidentalis Nutt., and vegetation and soil carbon (C) and nitrogen (N) pools. Background and Objectives: Initiated in 1967, this experiment intended to explore combinations of habitat type phases and prescribed fire severity toward supporting regeneration of L. occidentalis. At onset of the experiment, a wildfire affected a portion of the 60 research plots, allowing for additional study. Our objective was to better understand silvicultural practices to support L. occidentalis regeneration and to better understand the subsequent impacts of silvicultural practices on C and N pools within the vegetation and soil. Materials and Methods: We categorized disturbance severity based on loss of forest floor depth; 11 categories were defined, including controls for the two habitat type phases involved. We collected abundance, biomass, and C and N concentrations for the herbaceous layer, shrubs, and trees using nested quadrats and 6 to 10 experimental units per disturbance category plot. Moreover, we systematically sampled woody residue from transects, and forest floor, soil wood, and mineral soil with a systematic grid of 16 soil cores per disturbance category plot. Results: We found that (1) disturbance severity affected shrub species richness, diversity, and evenness within habitat type phases; (2) L. occidentalis regenerates when fire is part of the disturbance; (3) N-fixing shrub species were more diverse in the hotter, drier plots; (4) recovery levels of C and N pools within the soil had surpassed or were closer to pre-disturbance levels than pools within the vegetation. Conclusions: We confirm that L. occidentalis regeneration and a diverse suite of understory shrub species can be supported by harvest and prescribed fire, particularly in southern and western aspects. We also conclude that these methods can regenerate L. occidentalis in cooler, moister sites, which may be important as this species’ climate niche shifts with climate change

SB49-16/17: Resolution Amending Kaimin Personnel Policy

SB49-16/17: Resolution Amending Kaimin Personnel Policy passed 23Y-0N-0A at the January 25, 2017 meeting of the Associated Students of the University of Montana (ASUM)

Wood Decomposition After an Aerial Application of Hydromulch Following Wildfire in a Southern California Chaparral Shrubland

Severe wildfire can affect many soil processes, especially organic matter (OM) decomposition. Organic mulches are often applied on steep slopes to mitigate soil erosion, but little is known about how these surface organic additions affect subsequent soil OM decomposition. In 2003 the Cedar Fire burned 110,000 ha in southern California chaparral shrubland, after which hydromulch was aerially applied to reduce soil erosion. Subsequently, we established a 5-year study to assess the effect of hydromulch on OM decomposition at the burned soil surface and in the mineral soil using aspen (Populus tremuloides Michx.) and pine (Pinus taeda L.) wood stakes as standard substrates. Mass loss of both aspen and pine stakes in this dry Mediterranean ecosystem was lowest on the soil surface and increased with mineral soil depth. Decomposition was less in the hydromulched soil than in the untreated control, but the large loss of hydromulch from the soil surface within the first year after application make this result questionable. Subsequent analysis showed that subterranean termites had a major role in wood decomposition, but their variable activity in study replicates confounded the separation of hydromulch impacts on decomposition from other soil variables. Little is known on the role of termites in OM decomposition after wildfire, and they should be considered when designing studies in soils where termites are present. Our study results suggest that termite activity in mineral soil could also be a factor in root decomposition after a fire and affect soil stability on steep slopes

Grubbing by wild boars ( Sus scrofa L.) and its impact on hardwood forest soil carbon dioxide emissions in Switzerland

Interest in soil C storage and release has increased in recent years. In addition to factors such as climate/land-use change, vertebrate animals can have a considerable impact on soil CO2 emissions. To date, most research has considered herbivores, while the impact of omnivorous animals has rarely been investigated. Our goal was to determine how European wild boars (Sus scrofa L.), large omnivores that consume soil-inhabiting animals and belowground plant parts by grubbing in the soil, affect soil C dynamics. We measured soil respiration (CO2), temperature, and moisture on paired grubbed and non-grubbed plots in six hardwood forest stands for a 3-year period and sampled fine root and microbial biomass at the beginning and after 2years of the study. We also measured the percentage of freshly disturbed forest soil within the larger surroundings of each stand and used this information together with hunting statistics and forest cover data to model the total amount of CO2 released from Swiss forest soils due to grubbing during 1year. Soil CO2 emissions were significantly higher on grubbed compared to non-grubbed plots during the study. On average 23.1% more CO2 was released from these plots, which we associated with potential alterations in CO2 diffusion rates, incorporation of litter into the mineral soil and higher fine root/microbial biomass. Thus, wild boars considerably increased the small-scale heterogeneity of soil properties. Roughly 1% of Switzerland's surface area is similar to our sites (boar density/forest cover). Given the range of forest soil disturbance of 27-54% at our sites, the geographic information system model predicted that boar grubbing would lead to the release of an additional 49,731.10-98,454.74tCO2year−1. These values are relatively small compared to total soil emissions estimated for Swiss hardwood forests and suggest that boars will have little effect on large-scale emissions unless their numbers increase and their range expands dramaticall

Coarse Woody Debris and Carbon Stocks in Pine Forests after 50 Years of Recovery from Harvesting in Northeastern California

The long-term effects of harvesting on stand carbon (C) pools were assessed in a dry, interior pine-dominated forest at the Blacks Mountain Experimental Forest in northeastern California. Six 8-hectacre plots, established in 1938–1943, were treated as either an uncut control or a heavy-cut harvest (three-quarters of the stand volume removed). Response variables included C pools in overstory tree and shrub, coarse woody debris (CWD), forest floor, mineral soil (to 30 cm depth), cubicle brown root fragments of wood, fine roots, and ectomycorrhizal root tips. CWD was further classified as intact wood or more highly decayed brown rot or white rot types. CWD nutrient stocks (N, P, K, Ca, and Mg) and soil N content were also measured. In 1992, 50 years after harvest, total ecosystem C was 188 and 204 Mg C ha−1 in the harvest and control treatments or 8% lower (p = 0.02) in the harvest stands. There were changes in the distributions of C pools between the treatments. After 50 years of recovery, most C pools showed statistically non-significant and essentially no change in C pool size from harvests. Notable reductions in C with harvests were declines of 43% in CWD including standing snags (p = 0.09) and a decline of 9% of live tree C (p = 0.35). Increases in C pools after harvest were in a 3-fold build-up of fragmented brown cubicle rot (p = 0.26) and an 11% increase in soil C (p = 0.19). We observed strong evidence of C transfers from CWD to soil C pools with two- to three-fold higher soil C and N concentrations beneath CWD compared to other cover types, and lower CWD pools associated with elevated cubicle brown rot are elevated soil C in the harvests. Our results showed that while harvest effects were subtle after 50 years of regrowth, CWD may play an important role in storing and transferring ecosystem C to soils during recovery from harvesting in these dry, eastside pine forests of California. This poses a tradeoff for managers to choose between keeping CWD for its contribution to C sequestration and its removal as the hazardous fuels

Mechanical Characteristics of the Fine Roots of Two Broadleaved Tree Species from the Temperate Caspian Hyrcanian Ecoregion

In view of the important role played by roots against shallow landslides, root tensile force was evaluated for two widespread temperate tree species within the Caspian Hyrcanian Ecoregion, i.e., Fagus orientalis L. and Carpinus betulus L. Fine roots (0.02 to 7.99 mm) were collected from five trees of each species at three different elevations (400, 950, and 1350 m a.s.l.), across three diameter at breast height (DBH) classes (small = 7.5–32.5 cm, medium = 32.6–57.5 cm, and large =57.6–82.5 cm), and at two slope positions relative to the tree stem (up- and down-slope). In the laboratory, maximum tensile force (N) required to break the root was determined for 2016 roots (56 roots per each of two species x three sites x three DBH classes x two slope positions). ANCOVA was used to test the effects of slope position, DBH, and study site on root tensile force. To obtain the power-law regression coefficients, a nonlinear least square method was used. We found that: 1) root tensile force strongly depends on root size, 2) F. orientalis roots are stronger than C. betulus ones in the large DBH class, although they are weaker in the medium and small DBH classes, 3) root mechanical resistance is higher upslope than downslope, 4) roots of the trees with larger DBH were the most resistant roots in tension in compare with roots of the medium or small DBH classes, and 5) the root tensile force for both species is notably different from one site to another site. Overall, our findings provide a fundamental contribution to the quantification of the protective effects of forests in the temperate region

Asymmetrical copper root pruning may improve root traits for reforesting steep and/or windy sites

Our research demonstrates that plant material can be produced in the nursery with asymmetrical root systems, which may have utility for reforestation of difficult planting sites characterized by steep slopes and/or windy conditions. Such a root system can be generated using chemical root pruning by applying cupric carbonate (Cu) that can arrest the development of, or cause mortality to, root apical meristems resulting in the formation of new lateral roots with an overall increase in the biomass, length, and volume of the root system. Our objective was to investigate the effect of chemical root pruning on the morphological and architectural traits of adventitious roots produced by poplar cuttings (Populus nigra L.) grown in containers coated with Cu in various symmetrical (Side, Bottom, Side + Bottom) and asymmetrical (half side + half bottom) patterns. After six weeks, roots of the cuttings were extracted from different container depths (Top, Middle, and Bottom) and portions (non-coated, Cu-coated), and analyzed. The root systems reacted to all coating patterns by increasing length, biomass, volume, and average diameters, but magnitude of increase was further affected by depth. In particular, root growth was unaffected at the Top of the container, and length was the highest at the Bottom depth. The Middle depth had a significant increment in both biomass and volume. Also, the root population increased in diameter as a possible response to Cu exposure. Interestingly, in the asymmetrically coated containers this depth response in the non-coated portions was of higher magnitude than in the Cu-coated portions

Ongoing modifications to root system architecture of Pinus ponderosa growing on a sloped site revealed by tree-ring analysis

Abstract Our knowledge of the root system architecture of trees is still incomplete, especially concerning how biomass partitioning is regulated to achieve an optimal, but often unequal, distribution of resources. In addition, our comprehension of root system architecture development as a result of the adaptation process is limited because most studies lack a temporal approach. To add to our understanding, we excavated 32-year-old Pinus ponderosa trees from a steep, forested site in northern Idaho USA. The root systems were discretized by a low magnetic field digitizer and along with AMAPmod software we examined their root traits (i.e. order category, topology, growth direction length, and volume) in four quadrants: downslope, upslope, windward, and leeward. On one tree, we analyzed tree rings to compare the ages of lateral roots relative to their parental root, and to assess the occurrence of compression wood. We found that, from their onset, first-order lateral roots have similar patterns of ring eccentricity suggesting an innate ability to respond to different mechanical forces; more root system was allocated downslope and to the windward quadrant. In addition, we noted that shallow roots, which all presented compression wood, appear to be the most important component of anchorage. Finally, we observed that lateral roots can change growth direction in response to mechanical forces, as well as produce new lateral roots at any development stage and wherever along their axis. These findings suggest that trees adjust their root spatial deployment in response to environmental conditions, these roots form compression wood to dissipate mechanical forces, and new lateral roots can arise anywhere and at any time on the existing system in apparent response to mechanical forces

Early pine root anatomy and primary and lateral root formation are affected by container size: implications in dry-summer climates

Although the presence of root anatomical structures of young Pinus ponderosa seedlings grown in containers of contrasting volume (164 vs. 7000 cm3) was similar, seedlings reared 60 days in the large container had more vascular cambium although the xylem thickness was similar. In addition, seedlings in large containers had nearly twice as many resin ducts within the vascular cambium as their cohorts in small containers. Taproot length closely matched container depth. Though lateral root emission rates were similar between container sizes, large container seedlings had more than 2X the number of lateral roots as those from small containers. These differences in morphophysiological characteristics may be important to seedling establishment on sites that experience dry summer conditions, or for seedlings destined to drier, harsher sites. Further work to elucidate the ramifications of these morphophysiological differences on seedling establishment is warranted