Carbon stock densities of semi-deciduous Atlantic forest and pine plantations in Argentina

Unraveling impacts on carbon, water and energy exchange of Pinus plantations in South American temperate ecosystems

Tree plantations are expanding in southern South America and their effects on ecosystem services, particularly climate regulation, are still not well understood. Here, we used remote sensing techniques and a paired design to analyze ≈33,000 ha of Pinus plantations along a broad geographical and environmental gradient (26-43° South latitude, 54-72° West longitude). Radiation interception, surface temperature, evapotranspiration, and albedo were assessed both in tree plantations stands and in adjacent uncultivated areas. Additionally, the climatic impact of tree plantations was quantified by analyzing changes in atmospheric radiative forcing and its carbon (C) equivalent. Tree plantations intercepted more radiation when replacing steppes, grasslands, and shrublands but not when replacing forests. The control exerted on radiation interception by precipitation decreased in both space and time after tree plantation. Furthermore, evapotranspiration notably increased in tree plantations. The lower albedo of tree plantations compared to uncultivated adjacent areas induces global warming through the biophysical pathway. Thus, the climate benefits of afforestation through C sequestration can be counteracted by 18 to 83 % due to albedo changes. It is necessary to fully consider the biophysical effects and water footprint of tree plantations in public policies that promote them, as well as in international carbon accounting mechanisms.

Impact of soil from monoculture pine plantations on two anuran species from the Atlantic Forest: Odontophrynus reigi and Leptodactylus luctator

Monoculture tree plantations reduces landscape heterogeneity and the number and diversity of habitats available for species. Physical-chemical changes in soil may affect the ponds where tadpoles develop. This work aimed to study the effect on tadpoles of two species of frogs, Leptodactylus luctator (Ll) and Odontophrynus reigi (Or) exposed to soils from a pine plantation (PP), which were compared to tadpoles exposed to soils from Atlantic Forest, the native forest (NF). The impact of soils from both places on growth, development, antioxidant system and genetic damage of Ll and Or tadpoles were observed. A composite sample (5 kg) of soil was taken from the top 10 cm stratum in a 200 m transect in each site, with random plots of 50x50cm. In collected soil samples Organic Matter (OM), Organic Carbon (OC), and Total Nitrogen (TN) were determined. We conducted laboratory experiments, from 23 until 38 Gosner stages. During the experiment, pH and ammonium in the water were determined. Soil from NF presented higher content of OM, OC and TN, and water pH in PP was 0.2 units lower than in NF. Both species showed ≈60 % increase of catalase activity in PP, and ≈40 % increase of lipid peroxidation in NF. Ll tadpoles presented 10 times higher protein oxidation in PP than in NF, but Gosner stage was higher in NF. In NF the higher OM and OC in both species causes the increase of lipid peroxidation; and Ll responds to a stressor in PP that in Or is not observed. Or presented lower stress response towards PP soils, which indicates a tolerance towards this soil. The changes observed in soil chemistry, although not big from a physical-chemical point of view, affects the growth, development and oxidative stress of two species of anuran tadpoles from the NF, which can affect future populations and anuran diversity.

Network analysis reveals the regulatory effect of mixed stands on ecosystem structure and functions in the Loess Plateau, China

Afforestation, an important measure for ecological restoration, has been implemented all over the world, but fragile ecosystem structures and climate change endanger its ecological functions. One major obstacle to optimizing ecological function has been quantifying and characterizing a complex ecosystem structure. Here, the structure and functions of six types of land-use restoration were investigated in the hilly-gully region of the Loess Plateau, China. In total, 44 ecological factors from canopy, understory and soil were determined. We constructed the related network of reforestation ecosystems, quantified the structure of ecosystem through network topology, and explored the relationships between structure and functions. The results showed that changes in plantation type altered the network hubs, but some nodes, such as species height, breast-height diameter and understory biomass, were often keystone hubs. Mixed plantations enhanced the connectivity among different modules. In addition, we found that closeness of network connectivity was an important factor influencing ecological functions, while soil erodibility was the main limiting factor for reforestation ecosystem structure in this region. Moreover, mixed plantations tended to have more balanced topological metrics and ecological functions. Overall, this study suggests that mixed plantations or monoculture plantations should be designed according to the characteristics and ecological demands of the regional ecological environment. Although monoculture plantations may support local ecosystems, mixed plantations offer more resilience to a landscape because they were help to achieve a balance among the ecological functions.

Deforestation for Agriculture Temporarily Improved Soil Quality and Soil Organic Carbon Stocks

Deforestation for agricultural development or extension is a common land-use problem that may cause a series of changes in the ecological environment and soil carbon stock in planting systems. However, the response of soil physical, chemical properties and carbon stocks in agricultural systems in the initial period after deforestation have not been thoroughly examined, especially in the subsoil. We investigated the variations in the soil physicochemical properties and organic carbon stocks to a depth of 100 cm in a poplar (Populus deltoides cv. 35) plantation, a summer maize (Zea mays L.) followed by winter wheat (Triticum aestivum L.) field after 1 year of deforestation of a poplar plantation, and a wheat–maize rotation field used for decades. The soil bulk density and pH decreased, and the soil total nitrogen (TN), total phosphorus, and total potassium contents increased considerably. The soil organic carbon (SOC) content and stocks (to 100 cm) increased by 32.8% and 20.1%, respectively. The soil TN content was significantly (p < 0.001) positively correlated with the SOC content, and the C:N ratio increased for the field following deforestation. Furthermore, the nitrogen in the poplar plantation and the field following deforestation was limited. We recommend increasing the amount of nitrogen fertilizer following deforestation to improve fertility and this will be beneficial to SOC storage.