The Effects of Rehabilitation Treatments on Landscape Function Within a Softwood Plantation After Fire: Implications for Catchment Management

There is global interest in enhancing the ecosystem services provided by landscapes and catchments dominated by plantation (monoculture) forestry. Partial reversion of plantations to locally native species (reforestation) is one option. However, the ecological outcomes of this kind of plantation reversion are poorly known. The partial reforestation of a pine plantation (Pinus radiata D. Don 1836) in the Australian Capital Territory with native species following a wildfire provides a rare case study of the environmental consequences of such a reversion. We estimated changes in landscape functionality by measuring indices of water infiltration, nutrient cycling, and soil surface stability across five landscape-scale treatments after the 2003 Lower Cotter Catchment bushfire: (1) natural regeneration of a native forest burned in 2003, (2) burned pine plantation replanted to pines, (3) burned plantation replanted to native trees and shrubs, (4) burned plantation allowed to naturally regenerate, and (5) forest roads rehabilitated by planting native trees and shrubs. At 14 years after the fire, we found that the regenerating native forest had the highest indices of water infiltration, nutrient cycling, and soil surface stability. The burned pine plantation that was replanted to pines in 2005 had indices of functionality that were higher than the burned plantation areas that were either allowed to naturally regenerate to native eucalypt forest or were planted with native forest species. These two types of native forest rehabilitation treatments had only minor differences in functionality. The rehabilitated closed roads were the least functional. We found that a pine plantation at the closed canopy stage can supply regulating services of water infiltration, nutrient cycling, and soil surface stability comparable to a native forest at a similar stage postfire; however, a significant limitation of the plantation was its low ecosystem resilience. It required massive soil disturbance to replant postfire and long-term maintenance of an extensive unpaved road network. The active or passive rehabilitation of native forest is justified to improve the natural resilience to wildfire. However, this rehabilitation of a native forest following use as a pine plantation is a multidecade process in this relatively low-rainfall environment. Study Implications The 2003 Canberra bushfire destroyed the entire pine plantation at Lower Cotter Catchment, a water catchment in Australian Capital Territory, but also provided an opportunity to examine and quantify changes in ecosystem functions with different restoration treatments. Landscape Function Analysis, including three indices (water infiltration, nutrient cycling, and soil surface stability), was used in this study. Findings suggest that both native eucalyptus forests and pine plantations recovered to relatively high levels of functionality within just 15 years after the bushfire, compared with all other restoration treatments, but plantations of Pinus radiata are not resilient to wildfire from a commercial perspective. These results help to justify the controversial decision to restore the majority of the catchment with native species in 2005. However, long-term monitoring is needed to determine how long it will take for the replanted and natural regeneration treatments to approach the functionality of the native forest.

Spectral and Soil Quality Index for Monitoring Environmental Rehabilitation and Soil Carbon Stock in an Amazonian Sandstone Mine

Rehabilitation is the key factor for improving soil quality and soil carbon stock after mining operations. Monitoring is necessary to evaluate the progress of rehabilitation and its success, but the use of repeated field surveys is costly and time-consuming at a large scale. This study aimed to monitor the environmental/soil rehabilitation process of an Amazonian sandstone mine by applying spectral indices for predicting soil organic carbon (SOC) stock and comparing them to soil quality index. The studied area has different chronological rehabilitation stages: initial, intermediate, and advanced with 2, 10, and 12 years of onset rehabilitation activities, respectively. Non-rehabilitated (NR) and two native forest areas (RA) were used as controls. Soil samples were analyzed for physical, chemical, and biological attributes. After determination of Normalized Difference Vegetation Index and Bare Soil Index, simple regression analysis comparing these indices with SOC stock showed a good fit (R2 = 0.82). Rehabilitated areas presented higher soil quality index (~1.50-fold) and SOC stock (~10.6-fold) than NR; however, they did not differ of RA. The use of spectral indices was effective for monitoring the soil quality in this study, with a positive correlation between the predicted SOC stock and the calculated soil quality index.

Human land-use impacts viral diversity and abundance in a New Zealand river

Although water borne viruses have important implications for the health of humans and other animals, little is known about the impact of human land use on viral diversity and evolution in water systems such as rivers. We used metagenomic next generation sequencing to compare the diversity and abundance of viruses at sampling sites along a single river in New Zealand that differed in human land use impact, ranging from pristine to urban. From this we identified 504 putative virus species, of which 97% were novel. Many of the novel viruses were highly divergent, and likely included a new subfamily within the Parvoviridae. We identified at least 63 virus species that may infect vertebrates, most likely fish and water birds, from the Astroviridae, Birnaviridae, Parvoviridae and Picornaviridae. No putative human viruses were detected. Importantly, we observed differences in the composition of viral communities at sites impacted by human land use (farming and urban) compared to native forest sites (pristine). At the viral species level, the urban sites had higher diversity (327 virus species) than the farming (n=150) and pristine sites (n=119), and more viruses were shared between the urban and farming sites (n=76) than between the pristine and farming or urban sites (n=24). The two farming sites had a lower viral abundance across all host types, while the pristine sites had a higher abundance of viruses associated with animals, plants and fungi. We also identified viruses linked to agriculture and human impact at the river sampling sites in farming and urban areas that were not present at the native forest sites. Overall, our study shows that human land use can impact viral communities in rivers, such that further work is needed to reduce the impact of intensive farming and urbanization on water systems.

EFFECTS OF GLYPHOSATE ON GERMINATION AND PHOTOSYNTHESIS IN Prosopis alba G.: A BIOCHEMICAL APPROACH

In recent decades, the phytogeographic region of the Western Chaco has been subjected to heavy deforestation. The native forest was gradually replaced by agricultural crops using high doses of herbicides. Glyphosate is the most widely used herbicide, and its impact on the surrounding native flora is unknown. The aim of this work was to determine the effect of glyphosate on the germination of Prosopis alba seeds and the photosynthesis of seedlings. Seeds were placed between paper towels, moistened with solutions of 0, 10, 20, 20, 30 and 40 mg a.i. glyphosate l-1, in a growth chamber at 25 oC and a 12 h photoperiod. The percentage of germinated seeds and the mean germination time were calculated. The respiratory rate was measured in these seeds, and the activity of complexes I and III of the respiratory chain was quantified. The shikimate concentration and antioxidant response of the seeds were also quantified. Chlorophyll a fluorescence emission variables were measured in the cotyledons. It was concluded that glyphosate inhibits germination in P. alba seeds and decreases the speed of the process. This effect can partly be explained by inhibition of respiration, mainly at the level of complex III of the mitochondrial electron transport chain. It is also due to oxidative stress produced by the herbicide, since the antioxidant response of the seeds fails to compensate for the high production of reactive oxygen species. Glyphosate inhibits the photochemical stage of photosynthesis on P. alba cotyledons.

Interação dos atributos químicos do solo em área com floresta natural e com plantio de laranja (Citrus sinensis L Osb.)

Na região amazônica é comum a conversão de ambiente natural para o de cultivo, com isso o solo permanece em constantes modificações. As atividades agrícolas podem incrementar a heterogeneidade do solo provocando alterações nos atributos químicos do solo, decorrente principalmente das atividades de manejo e cultivo. Essas mudanças são mensuráveis e contribuem para caracterizar, avaliar e acompanhar as alterações ocorrida utilizando ferramentas estatísticas. Assim o estudo da variabilidade espacial dos atributos químicos dos solos é particularmente importante especialmente em áreas onde o solo está submetido a diferentes manejos, visando reduzir os efeitos da variabilidade na produção das culturas em função de determinadas práticas de manejo. Dessa forma, este trabalho tem por objetivo avaliar a variabilidade espacial dos atributos químicos em área de floresta natural e com cultivo de laranja em Colorado do Oeste, Rondônia. Foram selecionadas duas áreas de estudo, a primeira sendo a área de floresta nativa e a segunda sob cultivo de laranja em de Colorado do Oeste, Rondônia. Em cada área foi delimitada uma malha com 1.260 m² (42 x 30 m), com 48 pontos e espaçamento regular entre pontos de 6 m. Nos pontos de cruzamento da malha foram coletadas amostras em três profundidades (0,00-0,05; 0,05-0,10 e 0,10-0,20 m), correspondente ao horizonte diagnóstico do solo, perfazendo uma somatória de 144 amostras por área, logo, um total de 288. Serão determinados dos atributos químicos de pH em água, acidez potencial, alumínio trocável, fósforo e potássio disponível, e carbono orgânico. Com a obtenção dos dados, estes foram avaliados por meio de estatística descrita com teste de médias e a realização da análise multivariada. Houve diferença entre as duas áreas, a substituição da vegetação nativa por sistema de cultivo, ocasionou alterações nos atributos químicos do solo. O uso das técnicas multivariadas mostrou-se eficiente na distinção dos ambientes estudados. Interaction of the chemical attributes of the soil in an area with natural forest and with planting of orange (Citrus sinensis L. Osb.) A B S T R A C TIn the Amazon region it is common to convert from a natural environment to that of cultivation, with this the soil remains in constant modifications. Agricultural activities can increase the heterogeneity of the soil causing changes in the chemical attributes of the soil, mainly due to management and cultivation activities. These changes are measurable and contribute to characterize, evaluate and monitor the changes that have occurred using statistical tools. Thus, the study of the spatial variability of the chemical attributes of soils is particularly important, especially in areas where the soil is subjected to different managements, in order to reduce the effects of variability in the production of crops due to certain management practices. Thus, this work aims to evaluate the spatial variability of chemical attributes in an area of natural forest and with orange cultivation in Colorado do Oeste, Rondônia. Two study areas were selected, the first being the native forest area and the second under orange cultivation in Colorado do Oeste, Rondônia. In each area, a mesh of 1,260 m² (42 x 30 m) was delimited, with 48 points and regular spacing between points of 6 m. At the crossing points of the grid, samples were collected at three depths (0.00-0.05; 0.05-0.10 and 0.10-0.20 m), corresponding to the soil diagnostic horizon, making a sum of 144 samples per area, therefore, a total of 288. The chemical attributes of pH in water, potential acidity, exchangeable aluminum, available phosphorus and potassium, and organic carbon will be determined. Once the data were obtained, they were evaluated using statistics described with the means test and the multivariate analysis. There was a difference between the two areas, the replacement of native vegetation by a cultivation system, caused changes in the chemical attributes of the soil. The use of multivariate techniques proved to be efficient in distinguishing the studied environments.Keywords: Amazon soils, Use and management, Soil occupation.

Spatial variability of soil erodibility in pastures and forest areas in the municipality of Porto Velho, Rondônia

“Erodibility” is a characteristic of the soil that represents the susceptibility with which its particles from the most superficial layer are taken and transported to lower places by erosive agents, causing environmental and economic damages. This work estimated soil erodibility in pastures and forest areas in the municipality of Porto Velho-Rondônia. In the field, three areas with different types of vegetation were selected, one with brachiaria, another with mombaça grass, and a third in native forest. In areas with pastures, a sampling mesh of equal sizes was outlined (90 m x 60 m), and in the forested area an approximate sampling mesh (90 m x 50 m), with a regular spacing of 10 m between the samples points for both areas. The sampling was done at the crossing points of the mesh at a depth of 0.0-0.2 m, composing 70 sample points in the areas with pastures and 60 sample points in the forest area, totaling 200 samples. Then, laboratory analyzes were carried out to determine the texture followed by the fractionation of the sand, and the organic carbon followed by the estimate of the organic matter of the soil. The erodibility factors were calculated using indirect prediction models, and then, univariate, geostatistical and multivariate techniques were applied. The pastures’ environments differed from the forest environment. However, the mombaça grass area functions as an intermediate environment between the forest and the brachiaria, being closer to the forest environment. Keywords: erodibility, factors, kriging, principal components.

Soil Organic Carbon Dynamics in Two Rice Cultivation Systems Compared to an Agroforestry Cultivation System

After changes in tillage on croplands, it is necessary to assess the effects on soil organic carbon (SOC) dynamics in order to identify if soil is a sink or emitter of carbon to the atmosphere. This study was conducted in two plots of rice cultivation, where tillage and water management changes occurred. A third plot of native forest with Cacao trees was used as reference soil (agroforestry). For SOC balance estimation, measurement of organic carbon (OC) inputs was determined from necromass, roots, microbial biomass, and urea applications. CO2 and CH4 emissions were also measured. Results showed that the change in the use of irrigation and tillage in rice cultivation did not cause significant differences in OC inputs to soil or in outputs due to carbon emissions. Further-more, it was found that both irrigation and tillage management systems in rice cultivation com-pared with agroforestry were management systems with a negative difference between OC inputs and outputs due to CO2 emissions associated with intense stimulation of crop root respiration and microbial activity. The comparison of SOC dynamics between the agroforestry system and rice cultivation systems showed that an agroforestry system is a carbon sink with a positive OC dynamic.

Developing Multi-Source Indices to Discriminate between Native Tropical Forests, Oil Palm and Rubber Plantations in Indonesia

Over the last 18 years, Indonesia has experienced significant deforestation due to the expansion of oil palm and rubber plantations. Accurate land cover maps are essential for policymakers to track and manage land change to support sustainable forest management and investment decisions. An automatic digital processing (ADP) method is currently used to develop land cover change maps for Indonesia, based on optical imaging (Landsat). Such maps produce only forest and non-forest classes, and often oil palm and rubber plantations are misclassified as native forests. To improve accuracy of these land cover maps, this study developed oil palm and rubber plantation discrimination indices using the integration of Landsat-8 and synthetic aperture radar Sentinel-1 images. Sentinel-1 VH and VV difference (>7.5 dB) and VH backscatter intensity were used to discriminate oil palm plantations. A combination of Landsat-8 NDVI, NDMI with Sentinel-1 VV and VH were used to discriminate rubber plantations. The improved map produced four land cover classes: native forest, oil palm plantation, rubber plantation, and non-forest. High-resolution SPOT 6/7 imagery and ground truth data were used for validation of the new classified maps. The map had an overall accuracy of 92%; producer’s accuracy for all classes was higher than 90%, except for rubber (65%), and user’s accuracy was over 80% for all classes. These results demonstrate that indices developed from a combination of optical and radar images can improve our ability to discriminate between native forest and oil palm and rubber plantations in the tropics. The new mapping method will help to support Indonesia’s national forest monitoring system and inform monitoring of plantation expansion.

Trade-offs between environmental and economic factors in conversion from exotic pine production to natural regeneration on erosion prone land

Background: Some of New Zealand’s exotic pine (Pinus radiata D.Don) forests were planted for erosion mitigation but cultural, legislative, environmental, and profitability limitations in some parts of the landscape have led to reassessment of their suitability. There is limited information to support landowner decisions on the viability of natural regeneration of native forest post-pine-harvest. Methods: We evaluated scenarios of post-harvest natural regeneration, compared to remaining in pine production, using erosion susceptibility determined from historical occurrence of landslides, gullies and earthflows, biophysical growth modelling of mānuka–kānuka (Leptospermum scoparium-Kunzea ericoides (A.Rich) Joy Thomps.) shrubland using the process-based CenW model, and cost-benefit analyses using NZFARM with two land use change scenarios, at two levels of erosion mitigation ± honey profits. Results: In our study area, the Gisborne Region (North Island of New Zealand), ~27% of the land has moderate–very high susceptibility to landslides, 14–22% a high probability of contributing material to waterways, and 19% moderate–very high gully erosion susceptibility. Pines grow 10 times faster than naturally regenerating mānuka–kānuka shrubland, but mānuka–kānuka is used for honey not wood production. Natural regeneration resulted in losses of $150–250 ha-1 yr-1 compared to the current profitability of pine production. Honey production offset some reduction in pine revenue, but not fully. Thus, the viability of shifting from pines to native forest is highly dependent on landowner impetus and value for non-market ecosystem services (such as cultural and biodiversity values) provided by native forest. Conclusions: A mosaic of land uses within a property may sufficiently offset income losses with other benefits, whereby highly erosion-prone land is shifted from rotational pine forest production to permanent native forest cover with honey production where possible. At the regional scale in Gisborne, the conversion of the most highly susceptible land under production forestry (315–556 ha) to natural regeneration has the potential for wider benefits for soil conservation reducing erosion by 1–2.5 t yr–1 of sediment facilitating achievement of cleaner water aspirations and habitat provision.