Aboveground Deadwood Biomass and Composition Along Elevation and Land-Use Gradients at Mount Kilimanjaro

Deadwood is an important structural and functional component of forest ecosystems and biodiversity. As deadwood can make up large portions of the total aboveground biomass, it plays an important role in the terrestrial carbon (C) cycle. Nevertheless, in tropical ecosystems and especially in Africa, quantitative studies on this topic remain scarce. We conducted an aboveground deadwood inventory along two environmental gradients—elevation and land use— at Mt. Kilimanjaro, Tanzania. We used a huge elevation gradient (3690 m) along the southern slope of the mountain to investigate how deadwood is accumulated across different climate and vegetation zones. We also compared habitats that differed from natural forsts in land-use intensity and disturbance history to assess anthropogenic influence on deadwood accumulation. In our inventory we distinguished coarse woody debris (CWD) from fine woody debris (FWD). Furthermore, we calculated the C and nitrogen (N) content of deadwood and how the C/N ratio varied with decomposition stages and elevation. Total amounts of aboveground deadwood ranged from 0.07 ± 0.04 to 73.78 ± 36.26 Mg ha–1 (Mean ± 1 SE). Across the elevation gradient, total deadwood accumulation was highest at mid-elevations and reached a near-zero minimum at very low and very high altitudes. This unimodal pattern was mainly driven by the corresponding amount of live aboveground biomass and the combined effects of decomposer communities and climate. Land-use conversion from natural forests into traditional homegardens and commercial plantations, in addition to frequent burning, significantly reduced deadwood biomass, but not past selective logging after 30 years of recovery time. Furthermore, we found that deadwood C content increased with altitude. Our study shows that environmental gradients, especially temperature and precipitation, as well as different anthropogenic disturbances can have considerable effects on both the quantity and composition of deadwood in tropical forests.

Effects of In-Channel Structure on Chinook Salmon Spawning Habitat and Embryo Production

Adult salmonids are frequently observed building redds adjacent to in-channel structure, including boulders and large woody debris. These areas are thought to be preferentially selected for a variety of reasons, including energy and/or predation refugia for spawners, and increased hyporheic exchange for incubating embryos. This research sought to quantify in-channel structure effects on local hydraulics and hyporheic flow and provide a mechanistic link between these changes and the survival, development, and growth of Chinook salmon Oncorhynchus tshawytscha embryos. Data were collected in an eight-kilometer reach, on the regulated lower Mokelumne River, in the California Central Valley. Nine paired sites, consisting of an area containing in-channel structure paired with an adjacent area lacking in-channel structure, were evaluated. Results indicated that in-channel structure disrupts surface water velocity patterns, creating pressure differences that significantly increase vertical hydraulic gradients within the subsurface. Overall, in-channel structure did not significantly increase survival, development, and growth of Chinook salmon embryos. However, at several low gradient downstream sites containing in-channel structure, embryo survival, development, and growth were significantly higher relative to paired sites lacking such features. Preliminary data indicate that adding or maintaining in-channel structure, including woody material, in suboptimal spawning reaches improves the incubation environment for salmonid embryos in regulated reaches of a lowland stream. More research examining temporal variation and a full range of incubation depths is needed to further assess these findings.

Deforestation scenarios show the importance of secondary forest for meeting Panama’s carbon goals

Context Tropical forest loss has a major impact on climate change. Secondary forest growth has potential to mitigate these impacts, but uncertainty regarding future land use, remote sensing limitations, and carbon model accuracy have inhibited understanding the range of potential future carbon dynamics. Objectives We evaluated the effects of four scenarios on carbon stocks and sequestration in a mixed-use landscape based on Recent Trends (RT), Accelerated Deforestation (AD), Grow Only (GO), and Grow Everything (GE) scenarios. Methods Working in central Panama, we coupled a 1-ha resolution LiDAR derived carbon map with a locally derived secondary forest carbon accumulation model. We used Dinamica EGO 4.0.5 to spatially simulate forest loss across the landscape based on recent deforestation rates. We used local studies of belowground, woody debris, and liana carbon to estimate ecosystem scale carbon fluxes. Results Accounting for 58.6 percent of the forest in 2020, secondary forests (< 50 years) accrue 88.9 percent of carbon in the GO scenario by 2050. RT and AD scenarios lost 36,707 and 177,035 ha of forest respectively by 2030, a carbon gain of 7.7 million Mg C (RT) and loss of 2.9 million Mg C (AD). Growing forest on all available land (GE) could achieve 56 percent of Panama’s land-based carbon sequestration goal by 2050. Conclusions Our estimates of potential carbon storage demonstrate the important contribution of secondary forests to land-based carbon sequestration in central Panama. Protecting these forests will contribute significantly to meeting Panama’s climate change mitigation goals and enhance water security.

Regional Assessment of Carbon Pool Response to Intensive Silvicultural Practices in Loblolly Pine Plantations

Tree plantations represent an important component of the global carbon (C) cycle and are expected to increase in prevalence during the 21st century. We examined how silvicultural approaches that optimize economic returns in loblolly pine (Pinus taeda L.) plantations affected the accumulation of C in pools of vegetation, detritus, and mineral soil up to 100 cm across the loblolly pine’s natural range in the southeastern United States. Comparisons of silvicultural treatments included competing vegetation or ‘weed’ control, fertilization, thinning, and varying intensities of silvicultural treatment for 106 experimental plantations and 322 plots. The average age of the sampled plantations was 17 years, and the C stored in vegetation (pine and understory) averaged 82.1 ± 3.0 (±std. error) Mg C ha−1, and 14.3 ± 0.6 Mg C ha−1 in detrital pools (soil organic layers, coarse-woody debris, and soil detritus). Mineral soil C (0–100 cm) averaged 79.8 ± 4.6 Mg C ha−1 across sites. For management effects, thinning reduced vegetation by 35.5 ± 1.2 Mg C ha−1 for all treatment combinations. Weed control and fertilization increased vegetation between 2.3 and 5.7 Mg C ha−1 across treatment combinations, with high intensity silvicultural applications producing greater vegetation C than low intensity (increase of 21.4 ± 1.7 Mg C ha−1). Detrital C pools were negatively affected by thinning where either fertilization or weed control were also applied, and were increased with management intensity. Mineral soil C did not respond to any silvicultural treatments. From these data, we constructed regression models that summarized the C accumulation in detritus and detritus + vegetation in response to independent variables commonly monitored by plantation managers (site index (SI), trees per hectare (TPH) and plantation age (AGE)). The C stored in detritus and vegetation increased on average with AGE and both models included SI and TPH. The detritus model explained less variance (adj. R2 = 0.29) than the detritus + vegetation model (adj. R2 = 0.87). A general recommendation for managers looking to maximize C storage would be to maintain a high TPH and increase SI, with SI manipulation having a greater relative effect. From the model, we predict that a plantation managed to achieve the average upper third SI (26.8) within our observations, and planted at 1500 TPH, could accumulate ~85 Mg C ha−1 by 12 years of age in detritus and vegetation, an amount greater than the region’s average mineral soil C pool. Notably, SI can be increased using both genetic and silviculture technologies.

Modelling the disappearance of coarse woody debris, following a land clearing event

Background Land clearing generates coarse woody debris (CWD), much of which ultimately becomes atmospheric CO2. Schemes for greenhouse gas accounting must consider the contribution from land clearing, but the timing of the contribution will have large uncertainty, due to a paucity of knowledge about the rate of CWD disappearance. To better understand above-ground CWD disappearance following a land clearing event—through the actions of microorganisms, invertebrates, wildfire, or deliberate burning—we combined statistical modelling with an archive of semi-quantitative observations (units of CWD %), made within Queensland, Australia. Results Using a generalised additive mixed-effects model (median absolute error = 14.7%), we found that CWD disappearance was strongly influenced by the: (i) number of years elapsed since clearing; (ii) clearing method; (iii) bioregion (effectively a climate-by-tree species interaction); and (iv) the number of times burned. Years-since-clearing had a strongly non-linear effect on the rate of CWD disappearance. The data suggested that disappearance was reverse-sigmoidal, with little change in CWD apparent for the first three years after clearing. In typical conditions for Queensland, the model predicted that it will take 38 years for 95% of CWD to disappear, following a land clearing event; however, accounting for uncertainty in the data and model, this value could be as few as 5 years, or > 100 years. In contrast, due to an assumption about the propensity of land managers to burn CWD, the official method used to assess Australia’s greenhouse gas emissions predicted that 95% of CWD will disappear in < 1 year. Conclusions In Queensland, the CWD generated by land clearing typically takes 38 years to disappear. This ultimately implies that a key assumption of Australia’s official greenhouse gas reporting—i.e. that 98% of CWD is burned soon after a clearing event—does not adequately account for delayed CO2 emissions.

An unusual body colouration of Ceylon roughside snake (Aspidura ceylonensis)

The small sized, non-venomous, and fossorial colubrid snake genus Aspidura Wagler, 1830 is endemic to Sri Lanka. Aspidura ceylonensis (Günther, 1858) is rare and restricted to mid-elevation to montane and sub-montane forests at elevation of 500–1300 m a.s.l. in the Central Highlands and the Knuckles massif. It is found in cool and well-shaded forest areas, with thick moist leaflitter, woody debris, and loose soil. The usual adult body coloration on dorsum is dark reddish or dark orange, rarely yellowish, with a continuous black vertebral line and two rows of dorsolateral black spots along the body.