Soil microbial community response to ectomycorrhizal dominance in diverse neotropical montane forests.

Ectomycorrhizal (EM) associations can promote the dominance of tree species in otherwise diverse tropical forests. These EM associations between trees and their fungal mutualists have important consequences for soil organic matter cycling, yet the influence of these EM-associated effects on surrounding microbial communities is not well known, particularly in neotropical forests. We examined fungal and prokaryotic community composition in surface soil samples from mixed arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) stands as well as stands dominated by EM-associated Oreomunnea mexicana (Juglandaceae) in four watersheds differing in soil fertility in the Fortuna Forest Reserve, Panama.

Bacterial denitrification drives elevated NO emissions in arid southern California drylands.

Soils are the largest source of atmospheric nitrous oxide (NO), a powerful greenhouse gas. Dry soils rarely harbor anoxic conditions to favor denitrification, the predominant NO-producing process, yet, among the largest NO emissions have been measured after wetting summer-dry desert soils, raising the question: Can denitrifiers endure extreme drought and produce NO immediately after rainfall? Using isotopic and molecular approaches in a California desert, we found that denitrifiers produced NO within 15 minutes of wetting dry soils (site preference = 12.8 ± 3.

Wetting-induced soil CO emission pulses are driven by interactions among soil temperature, carbon, and nitrogen limitation in the Colorado Desert.

Warming-induced changes in precipitation regimes, coupled with anthropogenically enhanced nitrogen (N) deposition, are likely to increase the prevalence, duration, and magnitude of soil respiration pulses following wetting via interactions among temperature and carbon (C) and N availability. Quantifying the importance of these interactive controls on soil respiration is a key challenge as pulses can be large terrestrial sources of atmospheric carbon dioxide (CO ) over comparatively short timescales. Using an automated sensor system, we measured soil CO flux dynamics in the Colorado Desert-a system characterized by pronounced transitions from dry-to-wet soil conditions-through a multi-year series of experimental wetting campaigns.

Precipitation legacies amplify ecosystem nitrogen losses from nitric oxide emissions in a Pinyon-Juniper dryland.

Climate change is increasing the variability of precipitation, altering the frequency of soil drying-wetting events and the distribution of seasonal precipitation. These changes in precipitation can alter nitrogen (N) cycling and stimulate nitric oxide (NO) emissions (an air pollutant at high concentrations), which may vary according to legacies of past precipitation and represent a pathway for ecosystem N loss. To identify whether precipitation legacies affect NO emissions, we excluded or added precipitation during the winter growing season in a Pinyon-Juniper dryland and measured in situ NO emissions following experimental wetting.

Hierarchical detection of diverse Clade II (atypical) nosZ genes using new primer sets for classical- and multiplex PCR array applications.

The reduction of nitrous oxide (NO) to N represents the key terminal step in canonical denitrification. Nitrous oxide reductase (NosZ), the enzyme associated with this biological step, however, is not always affiliated with denitrifying microorganisms. Such organisms were shown recently to possess a Clade II (atypical) nosZ gene, in contrast to Clade I (typical) nosZ harbored in more commonly studied denitrifiers.