Mechanisms behind soil N dynamics following cover restoration in degraded land in subtropical China

Purpose

Nitrogen (N) is an important nutrient for re-vegetation during ecosystem restoration, but the effects of cover restoration on soil N transformations are not fully understood. This study was conducted to investigate N transformations in soils with different cover restoration ages in Eastern China.

Materials and methods

Soil samples were collected from four degraded and subsequently restored lands with restoration ages of 7, 17, 23, and 35 years along with an adjacent control of degraded land. A ¹⁵N tracing technique was used to quantify gross N transformation rates.

Results and discussion

Compared with degraded land, soil organic carbon (SOC) and total N (TN) increased by 1.60–3.97 and 2.49–5.36 times in restoration land. Cover restoration increased ammonium and nitrate immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) by 0.56–0.96, 0.34–2.10, and 0.79–3.45 times, respectively, indicating that restoration was beneficial for N retention. There were positive correlations between SOC content and ammonium and nitrate immobilization and DNRA, indicating that the increase in soil N retention capacity may be ascribed to increasing SOC concentrations. The stimulating effect of SOC on ammonium immobilization was greater than its effect on organic N mineralization, so while SOC and TN increased, inorganic N supply did not increase. Autotrophic and heterotrophic nitrification increased with increasing SOC and TN concentrations. Notably, heterotrophic nitrification was an important source of NO₃^??N production, accounting for 47–67% of NO₃^??N production among all restoration ages.

Conclusions

The capacity of N retention was improved by cover restoration, leading to an increase in soil organic carbon and total N over time, but inorganic N supply capacity did not change with cover restoration age.

     

Soil organic carbon allocation and dynamics under perennial energy crops and their feedbacks with soil microbial biomass and activity

The cultivation of perennial instead of annual energy crops has received growing interest. Previous studies identified numerous beneficial effects of perennial energy crop (PEC) cultivation for the agricultural landscape such as promotion of agrobiodiversity, reduced requirements for agrochemicals and fertilizers as well as a large potential for carbon accumulation in soil. However, the mere presence of soil organic matter (SOM) accumulation gives no indication about the persistence of the SOM for example after a recultivation of the stands. Therefore, this study focused on SOM pools of different density fractions and soil microbial parameters. Six different PECs were tested against a typical benchmark system as feedstock for anaerobic digestion. The study has shown that all PEC species increased soil microbial activity and provided an insight how they sequester carbon in soil. Moreover, significant modifications in basic soil properties caused by plant growth were observed. For example, the cultivation of giant knotweed has lowered the soil pH by more than 0.5 pH units compared to the benchmark system. After 5 years of PEC cultivation, total soil organic carbon stocks were increased between 1,500 ± 400 and 4,500 ± 1,500 kg C ha^-1 for the upper 10 centimetres of soil. The distribution among different soil fractions showed species-specific patterns. Tall wheatgrass and Virginia mallow showed particular high accumulation rates in the mineral-associated SOM fraction which indicates long residence times of the SOM after a possible recultivation of the fields.     

Surgical treatment of a complicated distal tibia epiphyseal Salter–Harris type I fracture in a yearling

This article describes the management of a complicated distal epiphyseal Salter–Harris type I fracture of the left tibia in a yearling horse. Closed reduction and internal fixation was attempted in the first surgery using tension band wires. Due to fracture instability 2 weeks after surgery, a full-limb transfixation pin cast was applied to the tibia and maintained for 7 weeks to prevent further fracture displacement and to achieve axial alignment. The full-limb cast was maintained for a total of 12 weeks, including the time with the transfixation pin cast. Cast sores and tendon laxity resolved without further complications. Ten months after the first surgery, the fracture had radiographically healed, and the horse was sound at the walk and trot in a straight line.     

Drinking water sources,availability, quality,access and utilization for goats in the Karak Governorate,Jordan

Goat production is an important agricultural activity in Jordan. The country is one of the poorest countries in the world in terms of water scarcity. Provision of sufficient quantity of good quality drinking water is important for goats to maintain feed intake and production. This study aimed to evaluate the seasonal availability and quality of goats’ drinking water sources, accessibility, and utilization in different zones in the Karak Governorate in southern Jordan. Data collection methods comprised interviews with purposively selected farmers and quality assessment of water sources. The provision of drinking water was considered as one of the major constraints for goat production, particularly during the dry season (DS). Long travel distances to the water sources, waiting time at watering points, and high fuel and labor costs were the key reasons associated with the problem. All the values of water quality (WQ) parameters were within acceptable limits of the guidelines for livestock drinking WQ with exception of iron, which showed slightly elevated concentration in one borehole source in the DS. These findings show that water shortage is an important problem leading to consequences for goat keepers. To alleviate the water shortage constraint and in view of the depleted groundwater sources, alternative water sources at reasonable distance have to be tapped and monitored for water quality and more efficient use of rainwater harvesting systems in the study area is recommended.

     

Connectedness of habitat fragments boosts conservation benefits for butterflies,but only in landscapes with little cropland

Landscape Ecology - Global change pressures (GCPs) imperil species and associated ecosystem functions, but studies investigating interactions of landscape-scale pressures remain scarce. Loss of...     

Consequences of a large-scale fragmentation experiment for Neotropical bats: disentangling the relative importance of local and landscape-scale effects

Context

Habitat loss, fragmentation and degradation are widespread drivers of biodiversity decline. Understanding how habitat quality interacts with landscape context, and how they jointly affect species in human-modified landscapes, is of great importance for informing conservation and management.

Objectives

We used a whole-ecosystem manipulation experiment in the Brazilian Amazon to investigate the relative roles of local and landscape attributes in affecting bat assemblages at an interior-edge-matrix disturbance gradient.

Methods

We surveyed bats in 39 sites, comprising continuous forest (CF), fragments, forest edges and intervening secondary regrowth. For each site, we assessed vegetation structure (local-scale variable) and, for five focal scales, quantified habitat amount and four landscape configuration metrics.

Results

Smaller fragments, edges and regrowth sites had fewer species and higher levels of dominance than CF. Regardless of the landscape scale analysed, species richness and evenness were mostly related to the amount of forest cover. Vegetation structure and configurational metrics were important predictors of abundance, whereby the magnitude and direction of response to configurational metrics were scale-dependent. Responses were ensemble-specific with local-scale vegetation structure being more important for frugivorous than for gleaning animalivorous bats.

Conclusions

Our study indicates that scale-sensitive measures of landscape structure are needed for a more comprehensive understanding of the effects of fragmentation on tropical biota. Although forest fragments and regrowth habitats can be of conservation significance for tropical bats our results further emphasize that primary forest is of irreplaceable value, underlining that their conservation can only be achieved by the preservation of large expanses of pristine habitat.

     

Review of ground-based methods to measure the distribution of biomass in forest canopies

? Context

Ecological research and an effective forest management need accurate information on the structure of the forest canopy to understand the biochemical, physiological and biogeochemical processes within a forest.

? Research question

This paper reviews the currently available instruments for measuring the distribution of biomass within forest canopies. We compare the most well-established approaches and present the different measurable parameters. A special focus lies on the resolution of the obtained data.

? Results

It was found that only 3D laser scanners offer data with the resolution required by ecologists, private landholders, the forest industry and the public to detect trends in tree growth patterns and canopy interactions in all three spatial dimensions. But data validation, data analysis and parameter extraction are still under development, and the price of the instrument is quite high.

? Conclusion

Research should focus on the parameter extraction from terrestrial laser scanner data as this could allow the calculation of functional attributes for different sections of a canopy on a high spatial resolution. It could also help ecologists characterize the structure of forest stands in a quick and precise way.     

Root architecture might account for contrasting establishment success of <Emphasis Type="Italic">Pseudotsuga menziesii</Emphasis> var. <Emphasis Type="Italic">menziesii</Emphasis> and <Emphasis Type="Italic">Pinus sylvestris</Emphasis> in Central Europe under dry conditions

Key message

Pinus sylvestris seedlings quickly expand their roots to deeper soil layers while Pseudotsuga menziesii concentrates its root system in the topsoil, thereby running the risk of desiccation during long dry spells, as indicated by lower survival after simulated summer drought.

Context

Pseudotsuga menziesii (Douglas-fir) is regarded as a promising species to maintain the productivity of Central European lowland forests given the projected increase of long dry spells.

Aims

Will the species be able to regenerate from seed and spread outside plantations in a drier temperate Europe?

Methods

We measured the relative growth rate, biomass allocation, root architecture, and phenotypic plasticity of Pseudotsuga menziesii seedlings sown in a common garden and grown under current precipitation and prolonged drought, respectively. The species’ competitive ability with respect to Pinus sylvestris L., the most drought-tolerant native conifer in Central Europe, was assessed during three growing seasons.

Results

Pinus sylvestris seedlings had higher relative growth rates than did Pseudotsuga menziesii seedlings, first in terms of aboveground biomass and later in terms of shoot height. This resulted in heavier and taller seedlings after three growing seasons under both moist and dry conditions. Shorter vertical roots corresponded with lower survival of Pseudotsuga menziesii seedlings under dry conditions.

Conclusion

Fast root proliferation allows Pinus sylvestris seedlings to reach deeper water pools that are less rapidly depleted during transient drought. By contrast, the shallow root system might put Pseudotsuga menziesii seedlings at the risk of desiccation during prolonged dry spells.