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Soil carbon stocks and land use change: A meta analysis
Abstract
The effects of land use change on soil carbon stocks are of concern in the context of international policy agendas on greenhouse gas emissions mitigation. This paper reviews the literature for the influence of land use changes on soil C stocks and reports the results of a meta analysis of these data from 74 publications. The meta analysis indicates that soil C stocks decline after land use changes from pasture to plantation (−10%), native forest to plantation (−13%), native forest to crop (−42%), and pasture to crop (−59%). Soil C stocks increase after land use changes from native forest to pasture (+ 8%), crop to pasture (+ 19%), crop to plantation (+ 18%), and crop to secondary forest (+ 53%). Wherever one of the land use changes decreased soil C, the reverse process usually increased soil carbon and vice versa. As the quantity of available data is not large and the methodologies used are diverse, the conclusions drawn must be regarded as working hypotheses from which to design future targeted investigations that broaden the database. Within some land use changes there were, however, sufficient examples to explore the role of other factors contributing to the above conclusions. One outcome of the meta analysis, especially worthy of further investigation in the context of carbon sink strategies for greenhouse gas mitigation, is that broadleaf tree plantations placed onto prior native forest or pastures did not affect soil C stocks whereas pine plantations reduced soil C stocks by 12–15%.
... Similarly, sapling recruitment was expressed as the number of saplings with DBH less than 1 cm in 2010 but who grew to be greater than 1 cm DBH by the second sample in 2015 (Condit et al., 1999;Bin et al., 2016). We assumed that the stock of organic carbon in soil was equivalent to that in the 0-10 cm soil layer (Guo and Gifford, 2002;Li et al., 2015;Bleam, 2016) and calculated it by soil bulk density, soil organic carbon and soil sampling depth (Mann, 1986). Similarly, we assumed ecosystem soil nitrogen and phosphorus stock were equivalent to nitrogen and phosphorus stock in the 0-10 cm soil layer (Guo and Gifford, 2002;Tuo et al., 2019). ...
... We assumed that the stock of organic carbon in soil was equivalent to that in the 0-10 cm soil layer (Guo and Gifford, 2002;Li et al., 2015;Bleam, 2016) and calculated it by soil bulk density, soil organic carbon and soil sampling depth (Mann, 1986). Similarly, we assumed ecosystem soil nitrogen and phosphorus stock were equivalent to nitrogen and phosphorus stock in the 0-10 cm soil layer (Guo and Gifford, 2002;Tuo et al., 2019). After removing samples which were missing data or obvious outliers, we were left with 163 subplots (with traps in their center) as the research object. ...
Forest functionality is generally considered a byproduct of forest diversity. Perhaps unsurprisingly, many researchers associate increasing multi-functionality with increasing diversity. Diversity, however, is an often-overused word that may describe a host of features, including the diversity of species, functional trait and structure. Furthermore, variable environmental features (such as topography) influence the interaction between forest plants and their function. Incorporating complex topography (like that associated with tropical and subtropical forests) into estimates of forest functionality is challenging and highly uncertain. In this paper, we applied structural equation models to disentangle the relative importance of topography and different components of what might be considered “plant diversity” to forest multifunctionality using repeated census of a 20-ha subtropical forest plot. We found that multifunctionality was principally influenced by structural diversity more so than either species composition or functional trait diversity. In our SEM model approach, we observed variations in topography could account for about 30% of variation in multifunctionality. Furthermore, variations in topography could indirectly influence forest multifunctionality by changing species composition, functional trait diversity, and structural diversity. Our work highlights the importance of topography and forest structure in regulating subtropical forest multifunctionality on the local scale. This suggests future subtropical forest management should focus on regulating forest structure. Namely, our results suggest land managers must take topography (and the complex interaction between topography and plant diversity) into account in order to build robust and multifunctional forests.
... As quoted by Wiesmeier et al. (2019), natural factors that affect SOC dynamics include soil properties, climate characteristics, and geographic factors. Besides natural indicators, the impact of human activities on SOC stock comes through land use (arable land, meadow, forest) and the case of intensive soil management (Guo and Gifford 2002, Barančíková et al. 2013, Maillard and Angers 2014, Poeplau and Don 2015. Loss of SOC stock after the conversion of natural ecosystems into agricultural land has been confirmed by many authors (Guo and Gifford 2002, Poeplau and Don 2015, Ledo et al. 2020. ...
... Besides natural indicators, the impact of human activities on SOC stock comes through land use (arable land, meadow, forest) and the case of intensive soil management (Guo and Gifford 2002, Barančíková et al. 2013, Maillard and Angers 2014, Poeplau and Don 2015. Loss of SOC stock after the conversion of natural ecosystems into agricultural land has been confirmed by many authors (Guo and Gifford 2002, Poeplau and Don 2015, Ledo et al. 2020. ...
... The C content of the plants was determined by multiplying the respective biomass by its C content. The total stock of soil was calculated based on its C content, sample depth, and bulk density [42]. C concentrations of both plant and soil samples were determined using the elemental analyzer vario MACRO cube ( Figure 3). ...
... BD is the soil bulk density (g/cm 3 ), Cc is the soil C concentration (%), and D is the soil sampling depth (cm). The ecosystem carbon storage was calculated by summing the total of each component (aboveground, roots, and soil) [42]. ...
Ecological restoration has a positive impact on global climate change. How plant-soil stores carbon in degraded grassland ecological restoration requires long-term monitoring and support. To reveal the dynamics of plant-soil carbon storage in the succession process of ecological restoration, compare the effects of artificial interference and natural restoration, and determine the impact of climate change and biodiversity on vegetation soil carbon storage, we conducted a study in National Grassland Natural Park, which is located on the southern foot of the Yinshan Mountains in Hohhot, Inner Mongolia, China. Based on long restoration chronosequences (2012–2022), using a space-for-time substitution approach and one-way ANOVA tests, Pearson correlation and structural equation modeling were used to investigate the interactions among these various factors. The results indicated that the carbon storage of aboveground vegetation first increased, and then, decreased with time. The underground root carbon storage and soil carbon storage at 0–10 cm and 20–30 cm first increased, then decreased, and finally, stabilized. The highest soil carbon storage (0–30 cm) was 102.11 t/ha in 2013, which accounted for 96.61% of the total organic carbon storage. The Shannon–Wiener index, individual number of species, and surface root carbon storage (0–10 cm) significantly increased the carbon storage of surface soil (0–10 cm) (p < 0.05). Compared to natural restoration, artificial restoration over seven years decreased soil carbon storage at 0–30 cm and underground root carbon storage at 0–10 cm (p < 0.05). Consequently, combining artificial restoration with natural restoration can help in establishing a more stable ecosystem faster and in increasing the carbon storage of the ecosystem. It is an effective management measure to promote grassland restoration in arid areas. Also, climate (MAT, MAP) change was closely correlated with plant-soil carbon storage.
... Even when arable soils are below the saturation level, the high C content in such soils is commonly considered to be a factor preventing further C accumulation. The removal of C from the atmosphere in managed terrestrial ecosystems-C sequestration and storage-has been the subject of numerous articles in recent years [6][7][8][9][10][11][12][13]. As noted by Chenu et al. [6], the term «sequestration», representing negative emission technology, denotes a relatively long duration period, at least 20 years based on the recommendations of the Intergovernmental Panel on Climate Change (IPCC). ...
... The application of manure makes it possible to achieve a maximum accumulation of 7-10 Mg·ha −1 C (Figures 2c and 3c), i.e., not more than 25% of the lost SOC stocks by native soils, although this accumulation may be unstable under the conditions of the future climate scenario RCP8.5, and part of the additionally accumulated SOC will be lost later. However, if we divide graphs 2c and 3c into two time periods, then the first characterizes a linear relationship between C inputs and SOC stocks during the first two decades, while the second resembles the potential SOC storage [19] more, assuming the saturation behavior described by RothC [8,16]. Against this background, the interannual variability in C stocks in alternative crop rotations can be 4-5 Mg·ha −1 , even in the absence of a fallow field. ...
Arable Chernozems with high SOC contents have the potential to be significant sources of GHGs, and climate change is likely to increase SOC losses, making the issue of carbon sequestration in this region even more important. The prospect of maintaining SOC stock or increasing it by 4‰ annually under planned management practice modifications for the period up to 2090 was evaluated using a long-term experiment on Haplic Chernozem in the Rostov Region, Russia. In this study, we used the RothC model to evaluate SOC dynamics for three treatments with mineral and organic fertilization under two adaptation scenarios vs. business-as-usual scenarios, as well as under two climate change scenarios. The correction of crop rotation and the application of organic fertilizers at high rates are essential tools for maintaining and increasing SOC stocks. These methods can maintain SOC stock at the level of 84–87 Mg∙ha−1 until the middle of the 21st century, as the first half of the century is considered to be the most promising period for the introduction of adaptation measures for the additional accumulation of SOC on Chernozems. Part of the additional accumulated SOC is expected to be lost before 2090.
... Murty et al., (2002) reported the decline in SOC stock in crop land soils as 16%. It has been shown that about 42% SOC is lost in soil when forest land is turned to crop land and about 59% SOC is lost in soil when grassland is turned to crop land (Guo and Gifford, 2002). For a Mollisol in central Ohio, Puget and Lal (2005) reported that cultivated farm lands had 51+ 4 (equivalent mass) Mg ha -1 lesser SOC and lesser 3.5 + 0.3 (equivalent mass) Mg ha -1 N within 30 cm soil layer of soil than under forested land. ...
... For example, Kern and Johnson (1993) and Murty et al. (2002) evaluated the decrease of SOC stock in the major US cropland soils at approximately 16% and 22 -25% respectively upon conversion from forest to crop. Similarly, Guo and Gifford (2002) reported that soils lost 42% of their SOC stock upon forest conversion. Carter et al. (1998) reported that cultivation decreased the mass of organic C (35%) and total N (10%) in the soil profile of Podzolic soils. ...
This study investigates changes in soil properties, specifically soil organic carbon (SOC) and total nitrogen (TN), associated with different land use systems derived from forests in the rainforest zone of Nigeria. The land use systems examined include mature oil palm plantation (OP), bush fallow or secondary forest (BF), alley cropping with multi-purpose trees (AC), and continuous cassava cropping with and without fertilizer (FC and UC). Converting forests to cultivated land led to a decrease in SOC and TN content and storage across all soil depths (0-10 cm, 10-20 cm, and 20-40 cm). In the top 0-10 cm depth, the average decrease in SOC and TN storage was 63% and 62%, respectively, while for 0-40 cm, the decrease was 48% and 46%, respectively, for all land use systems derived from forests. Furthermore, the study reveals that even after 5, 10, and 30 years of secondary forest regrowth (BF), alley cropping (AC), and oil palm plantation (OP), respectively, the fertility levels were not restored to those observed in the primary forest. These findings underscore the capacity of forest soils to conserve and enhance soil SOM (soil organic matter), which in turn plays an essential role in SOC sequestration, TN storage, and soil nutrient conservation.
... La fertilisation ou le chaulage des sols agricoles ainsi que les pratiques qui avaient lieu en forêt comme l'essartage, le soutrage ou le pâturage ont pu accentuer les différences de fertilité entre les sols agricoles et forestiers. Par exemple, le travail du sol en milieu agricole et l'exportation de la matière organique empêchent l'accumulation du carbone organique dans le sol ; la mise en culture de sol forestier ferait ainsi chuter le taux de carbone organique de près de 40 % (Guo & Gifford 2002). A l'inverse, les sols forestiers étant peu travaillés, ils présentent généralement une stratification des horizons marquée par rapport aux sols agricoles constamment homogénéisés par le labour. ...
... Ces différents modes de gestion des terres agricoles sont donc susceptibles d'impacter durablement les sols et les communautés végétales. Les anciennes pâtures présentent ainsi une teneur plus élevée en carbone, moins d'azote et de phosphore et un pH plus bas ainsi qu'une plus grande variation de la microtopographie que les anciennes cultures Guo & Gifford 2002 ;. Il a également été observé une plus grande richesse spécifique d'arbustes et d'herbacées et une composition fonctionnelle différente dans les forêts anciennement pâturées que les forêts anciennement cultivées Dyer 2010). ...
In France, the forest area decreased continuously until the middle of the 19th century, then increased rapidly following the industrial revolution. This forest minimum marks the limit between pre-existing "ancient forests" and the "recent forests" that were established later, because it makes it possible to assume a much longer forest continuity and to estimate precisely the historic forest areas thanks to the existence of complete historical maps (Napoleonic cadastre and Ordnance Survey maps among others). This temporal continuity of ancient forests induces a stability likely to favor the presence of particular species with low dispersal capacity and sensitive to disturbances.If the French forest area has almost doubled since 1850, it is estimated that 15 % of the forests present in 1840 has disappeared today at a national scale. Despite IUCN recommendations to protect ancient forests, conservation actions are still poorly defined and fall under the precautionary principle. This thesis project is part of a partnership with five French national parks located in mountain areas (Pyrenees, Cevennes, Mercantour, Ecrins and Vanoise) which have already vectorised and identified ancient forests on their territory. It aims to answer three main research questions :1- What is the role of ancient forests for the conservation of threatened species?2- Does the type of ancient land use influence the biodiversity of recent forests?3- Does forest management impact the biodiversity of ancient forests?The first question was addressed through statistical analysis of naturalist data collected by different networks of observers in the areas of adhesion of the five national parks in our study area. This work showed that threatened spermaphytes, pteridophytes, bryophytes, and forest beetles were more responsive to historical forest area than to current forest area, highlighting a 150-year lag in response to landscape change. The second part of the study was based on botanical surveys carried out in the forests of the Vanoise national park on four types of ancient use: forest, pasture, hay meadow and crop. This study showed that there was no difference in edaphic conditions between ancient forests and recent forests developed on former pastures and hay meadows, whereas forests located on former cropland had richer soils. On the other hand, differences in taxonomic and functional composition of understory plant communities were also smaller between ancient forests and former pastures than between ancient forests and former cropland. Finally, the third question was treated using metabarcoding surveys of fungal communities in the public forests of Vanoise with a gradient of time elapsed since the last harvest from one to 75 years. This study showed that the low-intensity silvicultural management of the Vanoise forests had little impact on soil fungal communities and confirmed the weak long-term traces left by grazing in recent forests.This work therefore highlights the importance of old-growth forests for the conservation of biodiversity, particularly forest species, but also emphasizes that the type of ancient land use is important to consider in recent forests. Former pastures in particular, which represent an important part of recent forests in mountain areas, have a lower impact than other land uses.
... Proportion of SOC stocks in the top 20 cm varies by land use type, with 42% of SOC stock in the top 20 cm in grassland soils compared to 50% for forest soils (Jobbagy and Jackson 2000;Lal 2022). Conversion of crop to pasture land has been documented to increase SOC stocks, with conversion from pasture to crop leading to a loss of SOC (Guo and Gifford 2002;Lal 2022). However, globally, there continues to be a conversion of grazing lands to cultivated crops (Ramankutty et al. 2008). ...
... The higher SOC stocks in grassland soils are corroborated by other studies that have documented increased SOC stocks when land is converted to perennial crops. Converting crop to pasture was associated with an increase of 19% in SOC stocks in Australia and the USA (Guo and Gifford 2002). However, grassland versus cropland SOC stock comparisons have been limited in the Canadian Prairies. ...
A three-dimensional predictive soil mapping approach for predicting soil organic carbon (SOC) stocks (t/ha) at high spatial resolution (30 m) for Alberta for 2020–2021 is described. A remote sensing data stack was first prepared covering Alberta’s agricultural lands. A total of 404 sampling locations were distributed across Alberta using 2-scale sampling: (1) 22 pilot farms representing main climatic zones and (2) conditioned Latin hypercube sampling at each farm. Soil samples were taken at four standard depths (0–15, 15–30, 30–60, 60–100 cm) using soil probes and analyzed for SOC. Predictive models for SOC content and bulk density were built separately and then used to predict at 0, 15, 30, 60, and 100 cm and calculate aggregated SOC stocks per pixel. The SOC content and bulk density models had R squares of 0.61 and 0.68, respectively. Based on these mapping results, grassland soils were consistently associated with higher SOC stocks across all soil types as compared to croplands. The average SOC stocks for grassland soils were 2.1 Mg per hectare, ranging from 2.17 to 6.09 Mg per hectare depending on soil type. Results also showed that >15 % of total SOC stocks were located in subsoil, which was higher than expected.
... Foundational knowledge of OC storage and sequestration rates is needed to inform decision-making and help develop strategies and policy to both protect and manage OC within these intertidal environments. Currently, the order of magnitude difference in global saltmarsh organic carbon stock estimates are the product of paucity in empirical observations, gaps in global saltmarsh areal extent (McOwen et al., 2017;Worthington et al., 2023), and a lack of national OC stock assessments which are now common in terrestrial environments (e.g., Guo and Gifford, 2002;Pan et al., 2011). To date, only the United States of America and Australia have quantified saltmarsh OC stocks at the national scale (Macreadie et al., 2017;Holmquist et al., 2018). ...
Coastal wetlands, such as saltmarshes, are globally widespread and highly effective at capturing and storing 'blue carbon' and have the potential to regulate climate over varying timescales. Yet only Australia and the United States of America have national inventories of organic carbon held within saltmarsh habitats, hindering the development of policies and management strategies to protect and preserve these organic carbon stores. Here we couple a new observational dataset with 4,797 samples from 26 saltmarshes across Great Britain to spatially model organic carbon stored in the soil and the above and belowground biomass of Great British saltmarshes. Using average values derived from the 26 marshes, we deliver first-order estimates of organic carbon stocks across Great Britain's 448 saltmarshes (451.66 km 2). The saltmarshes of Great Britain contain 5.20 ± 0.65 Mt of organic carbon, 93% of which is in the soil. On average, the saltmarshes store 11.55 ± 1.56 kg C m-2 with values ranging between 2.24 kg C m-2 and 40.51 kg C m-2 depending on interlinked factors such as geomorphology, organic carbon source, sediment type (mud vs sand), sediment supply, and relative sea level history. These findings affirm that saltmarshes represent the largest intertidal blue carbon store in Great Britain, yet remain an unaccounted for component of the United Kingdom's natural carbon stores.
... The conversion of primary natural forest to other land use types disturbs the equilibrium between carbon inflows and outflows in soils until a new equilibrium is eventually established in the new land use types (Guo and Gifford 2002). Deng et al. (2016) affirmed that during this process, soil C stocks could be affected positively or negatively, as the new ecosystem or land use type could act either as a carbon source or as a carbon sink. ...
Background and Aims
Monitoring temporal trends in soil properties under rice paddy ecosystems is key for efficient soil management interventions toward sustainable and climate-smart rice production. The objectives of this study were to thoroughly investigate the temporal variations of measured soil properties and evaluate the changes in carbon stocks and soil fertility over a 12-year period under intensively managed rice paddy fields.
Methods
A total of 2110 sampling points in paddy rice fields under the same agronomic management were identified. Composite soil samples from the topsoil (0 – 15 cm depth) were collected from each sampling point in each sampling year (2007, 2011, 2015, and 2019) and comprehensively analysed.
Results
After 12 years of intensive rice cultivation, soil organic matter significantly increased from 25 g kg-1 to 29.3 g kg-1, with an annual rate of change of 0.33 – 0.34 g kg-1. Within the 12-year period, available phosphorus significantly increased from 130.87 to 140.80 mg kg-1, with a rate of change of 0.83 – 0.95 mg kg-1 year-1. The C stocks increased in the subsequent years with a relative change ratio of 0.94 and 3.91% in 2015 and 2019, respectively.
Conclusion
In a span of 12 years, intensive rice cultivation resulted in an increase in soil fertility. Among the identified soil factors, soil pH, organic carbon, exchangeable calcium, and available silicate were positively associated with soil fertility improvement. This study is crucial for the development of sustainable soil management interventions and climate-smart agricultural systems in intensively cultivated rice paddy ecosystems.
... Intensive farming with an annual application of fertilizers, the use of plant-protection chemicals, and various types of tillage and erosion all cause losses of the total soil carbon reserve, leading to an increase in the release of gases into the atmosphere, namely, N 2 O and CO 2 [1][2][3][4][5][6][7]. ...
Soil bacterial and fungal communities were investigated in relation to soil type and farm management practices after vegetation harvesting in autumn. Soils from felds cultivated with Phaseolus vulgaris (bean) and Pyrus comminus (pear) and nonarable, natural areas were studied. Microbial diversity was analysed using cultivation-dependent methods (isolation of pure cultures) and cultivation-independent methods (direct extraction of DNA from soil, followed by PCR amplifcation of the 16S rRNA and 18S rRNA genes). Te use of cultivation-dependent methods revealed that there were no diferences in the biodiversity of the soil bacterial and fungal communities between felds cultivated with bean plants and pear trees. However, the use of cultivation-independent methods showed that there were clear soil and crop type-specifc efects on the composition of the soil bacterial and fungal communities. Te density of the bacterial population was two times higher in northern mountain-valley serozem (NMVS) soil samples than in light chestnut (LC) soil samples. In contrast, the densities of the fungal communities were almost equal in the studied soil types. Te density of the actinomycetes community was almost two times higher in LC soil than in NMVS soil under bean plants. Te Shannon index values showed that the bacterial biodiversity in the NMVS soil samples was greater than that in the LC soil samples. Soils under fallow appeared to have diverse bacterial communities that mainly consisted of local au-tochthonous microfora and a small amount of zymogenic microfora (since fresh plant residue does not enter the soil). Te Shannon index results revealed two interesting facts: (1) the soil bacterial community was highly diverse in soils that supported bean plants and (2) the soil fungal biodiversity was high under pear trees in both soil types.
... Environmental variables (e.g., soil type, climate), crop type and management practices (e.g., sowing date of cover crop) will all be important. Cover crops, particularly perennial and/or leguminous crops, may increase SOC sequestration [28,66]. Although N 2 O emissions may decrease in the short term, they may increase in the longer-term due to interactions with the C cycle [67]. ...
The European Union’s ‘Green Deal’ proposes an ambitious roadmap towards climate neutrality by 2050 and the adoption of a circular economy. Functional AgroBiodiversity (FAB) measures, which balance food production with minimised impacts on nature, are a promising way to achieve this on farmland. Here, we undertake a rapid evidence assessment to highlight Functional Agro-Biodiversity (FAB) management measures which help to realise biodiversity, climate neutrality, efficiency in use of natural resources and the circular economy. We report evidence on the effectiveness of 10 common FAB measures employed in Europe following a resurgence of interest and increased availability of data on their impact. The review found that the outcomes of implementing FAB measures were largely positive, with a number of mixed effects. There are evidence gaps, e.g., the impact of FAB measures on yield, the magnitude and timescale of impacts, the effect of landscape context. We signpost the most relevant and well-documented FAB measures, providing a reference for land managers and practitioners to select FAB measures to achieve specific ecological and agricultural outcomes. It is also important to note that a combination of measures implemented in a strategic way can enhance the output success.
... Previous studies have shown that the conversion of natural forests to artificial forests resulted in a 13% decline in SOC stocks, while the transformation of forests into cultivated lands led to a more significant reduction of approximately 25-42% (Don et al. 2011;Guo and Gifford 2002;Murty et al. 2002). In addition to deforestation, farming activities such as cultivation, harvesting, weeding, and intensive tillage practices contribute to the decline in SOC and N stocks in cultivated land by accelerating the decomposition of soil organic matter (SOM) and reducing C levels (Chen et al. 2016;Guan et al. 2015). ...
Background
The restoration of conventional tea plantations and the adoption of organic farming practices could impact soil organic carbon (SOC) and nitrogen (N) stocks. This study investigated the soil properties, SOC and N contents and stocks, and their vertical distributions of a secondary forest restored from an abandoned conventional tea plantation and a converted organic tea plantation. An adjacent conventional tea plantation employing similar intermediate farming served as a comparison.
Results
Within a 50-cm depth, the secondary forest exhibited a higher SOC stock of 115.53 ± 7.23 Mg C ha− 1 compared to 92.1 ± 8.54 Mg C ha− 1 for the conventional tea plantation. No significant differences in N stocks were seen between the two land uses. Significantly high SOC and N contents and stocks were found in the 0–10 cm layer of the secondary forest compared to the conventional tea plantation. No significant disparities in SOC and N stocks were found between the conventional and organic tea plantations within the 50 cm depth (92.1 ± 8.54 Mg C ha− 1 and 10.06 ± 1.01 Mg N ha− 1 vs. 97.47 ± 1.53 Mg C ha− 1 and 9.70 ± 0.10 Mg N ha− 1). However, higher levels of SOC and N contents and stocks were observed at a depth of 10 cm in the conventional tea plantation and below 10 cm in the organic tea plantation.
Conclusions
The C and N inputs derived from high litter production at the top soil strongly contributed to higher SOC and N contents and stocks in the secondary forest. The application of soybean amendments in the conventional tea plantation and the longer tea plantation age of the organic tea plantation influenced their distribution of SOC and N contents and stocks, respectively. Reverting a conventional tea plantation into a secondary forest contributed to C recovery and reaccumulation. The conventional tea plantation, employing similar intermediate farming practices, increased SOC and N contents and stocks in the surface soil compared to the organic tea plantation. However, adopting organic farming did not significantly increase SOC stocks compared to the conventional tea plantation.
Supplementary Information
The online version contains supplementary material available at 10.1186/s40529-023-00401-z.
... Soil health and nutrient management practices focus on optimizing soil conditions and nutrient levels to support healthy crop growth while minimizing environmental impacts [17] . Soil sensors and sampling methods provide data on soil moisture, temperature, pH and nutrient content. ...
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... As Fig. 4 demonstrates, areas with high carbon storage density were distributed in wetlands and woodland, while cultivated land and grassland presented a weaker carbon sequestration capacity, with urban areas having no carbon storage. The decline in carbon storage is closely related to the degradation of natural ecosystems due to anthropogenic factors (Ouyang et al., 2016;Guo and Gifford, 2002). In other regions, such as the Pearl River Delta urban agglomeration, it has been revealed that carbon storage was slightly reduced by 1.94 % from 2000 to 2018 under urbanization . ...
Understanding how land cover and ecosystem services respond to diverse policies is essential for economic development and ecological conservation. However, few efforts have been made to analyze the policies in conjunction with land cover and ecosystem services in the Poyang Lake Ecological Economic Zone (PYLEEZ), limiting the sustainable improvement of the region. Therefore, this study quantified changes in land cover and four ecosystem services, evaluated the relationships between them, and analyzed how various policies affected land cover and ecosystem services in the PYLEEZ from 2000 to 2020. The results showed that artificial surfaces expanded at the expense of cultivated land. Agricultural encroachment resulted in the loss of most woodland and wetland. Under ecological policies, 2062.19 km 2 of cultivated land have been returned to natural land, leading to a net wetland area increase of 760.8 km 2. In terms of ecosystem services, crop production increased significantly (+151 %) and carbon storage reduced slightly (-2.7 %) under the influence of agricultural policies and rapid urbanization. Furthermore, habitat quality and water yield increased by 252.75 km 2 and 61.3 × 10 8 m 3 , respectively. Carbon storage presented a clear trade-off relationship with crop production, while habitat quality was synergistic with water yield and crop production. Given the current policies in the PYLEEZ, it is worthwhile to focus on water ecological safety and minimize the loss of natural land and ecosystem services driven by economic policies. This study is expected to help achieve the balanced development of the social economy and ecological conservation in the PYLEEZ.
... Forages are also key components of minimum and notill cropping systems in Brazil and Colombia (Lal, 2004). Guo and Gifford (2002) analyzed the results from 74 papers on the effects of land use changes on soil carbon stocks. While soil carbon stocks declined in conversion from pastures to plantations and from forests or pastures to crops, they increased when converting annual crops to plantations, crops to pastures, crops to secondary forest, and, interestingly, forest to pastures. ...
Livestock production is a major source of GHGemissions, and reducing meat consumption or changing from ruminant to non-ruminant meat could have a number of environmental benefits. Improving management of grazing land has the greatest mitigation potential of all agricultural interventions, over 1.5 bt CO 2 equivalents/year, sufficient to offset all the emissions from livestock production. In our view, ignoring the importance of forage-based systems may leave 50-80 per cent of the mitigation potential of agriculture untapped. Thus, improved grassland management and sustainable intensification of forage-based systems (through improved resource use efficiency, improved carbon sequestration, and reduced emissions due to BNI) are key to mitigating GHG emissions from livestock production, and will deliver other co-benefits such as increased productivity, reduced erosion, improved soil quality and nutrient and water use efficiency, resource conservation, reduced costs, and social and cultural benefits.
... The conversion of mangrove forests into shrimp ponds accounts for at least 75.5% of total carbon loss [52]. Soil carbon stock decreased from native forest to plantations (−13%) and native forest to plantations (−42%) [53]. ...
Mangrove forests play an important role in coastal areas from an ecological perspective, being able to store large amounts of carbon through sequestration and inhibiting climate change processes by absorbing CO2 in the atmosphere. In recent years, there have been changes in the land cover of converted and degraded mangrove forests which have resulted in the release of carbon and an imbalance in soil structure, which in turn cause a flux of CO2 into the atmosphere. This research was conducted at the Karang Gading and Langkat Timur Laut Wildlife Reserve (KGLTLWR) in North Sumatra, Indonesia. The study focused on six different land covers, namely natural forests, restoration, mixed agriculture, paddy fields, oil palm plantation, and ponds. This study aimed to measure the total carbon stock of mangrove forests that have been converted to other land covers and estimate the level of CO2 flux in the area. A total of three transects and six plots for each land cover were used in this study; for tree biomass, a non-destructive method was used by recording every DBH > 5 cm, and for soil carbon, drilling was carried out, which was divided into five depths in each plot. CO2 flux was measured using an Eosense Eosgp CO2 sensor with the static closed chamber method. The highest carbon stock was found at 308.09 Mg ha−1 in natural forest, while the lowest 3.22 Mg ha−1 was found in mixed agriculture. The highest soil carbon was found at 423.59 MgC ha−1 in natural forest, while the lowest 50.44 MgC ha−1 was found in mixed agriculture dry land. The highest average CO2 flux value of 1362.24 mgCO2 m2 h−1 was found in mangrove restoration and the lowest in ponds was 123.03 mgCO2 m2 h−1. Overall, the research results inform how much carbon stock is lost when converted to other land covers so that it can be used as a reference for policy makers to provide future management of mangrove forests and develop mitigation measurements to reduce carbon emissions.
... When vegetation was present, FRB was the most influential factor on the content of organic carbon and its components, with a contribution of 69.1%. Guo and Gifford (2002) and Davidson et al. (2011) suggested that root distribution and quality are key determinants of soil organic carbon response to vegetation type because plants transport organic matter to the subsurface through root secretion and abscission, can use their own biomass inputs to modify organic carbon content (Zhou et al., 2022), and can also increase inputs to soil organic carbon sources through their interactions with certain symbiotic bacteria (Wei et al., 2019). Roots can either directly affect SOC or affect SOC and its components by affecting TN content, showing the highest total effect in the structural equation model ( Figure 10B), which also confirms the root contribution to soil SOC. ...
Introduction
The variation of organic carbon content in spoil heaps is closely related to improving soil structure, maintaining soil fertility, and regulating soil carbon cycling balance. Analyzing the soil organic carbon content and related driving factors during the natural vegetation restoration process of spoil heaps is of great significance for promoting the accumulation of soil organic carbon in the spoil heaps.
Methods
we selected spoil heaps with the same number of years of restoration to research the variations in soil organic carbon components under different vegetation types (grassland: GL, shrubland: SL, secondary forest: SF) and compared the results with those on bare land (BL).
Results
Our results showed that vegetation type and soil depth significantly affect the content of soil organic carbon components. There was no difference in soil organic carbon components between SF and SL, but both were considerably superior to GL and BL ( p <0.05), and the particulate organic carbon (POC) and light fraction organic carbon (LFOC) contents of SL were the highest. A significant positive linear correlation existed between SOC and active organic carbon components. Pearson’s correlation and redundancy analysis showed that the available potassium (AK) and total nitrogen (TN) contents and gravel content (GC) in the BL soil significantly impacted soil organic carbon. When vegetation is present, TN, total phosphorus (TP), and Fine root biomass (FRB) significantly affect soil organic carbon. Structural equation modelling (SEM) shows that AK and soil moisture content (SMC) directly affect the organic carbon composition content of BL, When there is vegetation cover, fine root biomass (FRB) had the largest total effect in the SEM. Soil bulk density (BD) has a negative impact on soil organic carbon, especially in the presence of vegetation.
Conclusion
These findings suggest that vegetation restoration can significantly increase soil organic carbon content, FRB, AK, and TN play important roles in enhancing soil organic carbon. Supplementation with nitrogen and potassium should be considered in the bare land stage, and shrubs nitrogen-fixing functions and well-developed roots are more beneficial for the accumulation of soil organic carbon.
... Unfortunately, human activities such as deforestation, urbanization, and unsustainable agricultural practices can disrupt the natural carbon sequestration process and reduce the soil's carbon storage capacity (Yılmaz and Dengiz, 2021). Understanding the impact of different land use management on soil organic matter content and composition is crucial for soil's atmospheric CO2 management (Guo and Gifford, 2002;Murty et al., 2002). Understanding the intricacies of carbon sequestration in soil science is highly important in our global efforts to effectively address climate change. ...
Scientists and researchers have recently turned their attention to the soil's carbon sequestration potential (CSP) in their pursuit of mitigating climate change and its adverse effects. This emerging field within soil science offers promising strategies to combat rising atmospheric carbon dioxide (CO2) levels and global warming. In this study, the CSP of surface soils in agricultural lands where sunflowers are grown under semi-arid climate conditions was determined, predicted using artificial neural networks (ANN), and their relationships with certain soil properties were evaluated. The organic carbon (OC) contents of the soils were found to range from 0.10% to 3.71%, and their CSP varied between 31.60 and 81.54 tons of C per hectare. The CSP of the soils showed low positive correlations with the sand and clay contents of the study area and low negative correlations with soil OC. It was observed that higher OC levels in soils used for sunflower cultivation led to lower levels of CSP. An increase in the amount of OC in agricultural soils was considered to enhance carbon retention in the soil, consequently reducing the CSP. ANN were employed to predict CSP using soil sand, silt, clay, and OC contents as inputs, and the CSP as the target. The results of the prediction indicated that ANN could be used with 99% accuracy in determining soil CSP.
... Ultimately, the capacity of soils to act as a C sink or as a source depends on the balance between C inputs and outputs, and thus it is intrinsically related to the land cover, land use, and management adopted (Amelung et al., 2020). In general, the replacement of native vegetation to agriculture results in SOC loss (Don et al., 2011;Guo and Gifford, 2002), particularly when highly disturbing soil practices (e.g., tillage) are used together with low plant inputs (Amelung et al., 2020). Adopting climate-smart management practices can alter or mitigate SOC loss and even recover SOC levels Paustian et al., 2016). ...
The recent agricultural expansion in the Matopiba region, Brazil's new agricultural frontier, has raised questions about the risk of increasing soil organic carbon (SOC) loss as large areas of native vegetation (NV; i.e., Cerrado biome) have been replaced by large-scale mechanized agriculture. Although sustainable managements, such as integrated crop-livestock (ICL) systems, are considered strategic to counterbalance the SOC loss associated with land-use change (LUC) while keeping food production, little is known about their long-term effects on SOC stocks in the Matopiba region. To this end, we used the DayCent model to simulate the effects of converting the management commonly used in this region, i.e., soybean-cotton rotation under no-tillage (NT), into ICL systems with distinct levels of intensification (e.g., crop rotations: soybean-pasture and soybean-pasture-cotton; soil and crop management: grass irrigation, scarification/harrowing, and length of grass cultivation) on long term SOC dynamics. Additionally, data from two projected climate scenarios: SSP2-4.5 [greenhouse gases emissions (GHG) will not change markedly over time and global temperature will increase by 2.0 °C by 2060] and SSP5-8.5 (marked changes in GHG emissions are expected to occur resulting in an increase of 2.4 and 4.4 °C in global temperature in the middle and at the end of the century) were included in our simulations to evaluate climate change effects on SOC dynamics in this region. Based on a 50-yr-time frame simulation, we observed that SOC stocks under ICL systems were, on average, 23% and 47% higher than in the NV (36.9 Mg ha−1) and soybean-cotton rotation under NT (30.9 Mg ha−1), respectively. Growing grasses interlaid with crops was crucial to increase SOC stocks even when disruptive soil practices were followed. Although the irrigation of grass resulted in an early increase of SOC stocks and a higher pasture stoking rate, it did not increase SOC stocks in the long term compared to non-irrigated treatments. The SSP2-4.5 and SSP5-8.5 climate scenarios had little effects on SOC dynamics in the simulated ICL systems. However, additional SOC loss (∼0.065 Mg ha−1 yr−1) is predicted to occur if the current management is not improved. These findings can help guide management decisions for the Matopiba region, Brazil, to alleviate the anthropogenic pressure associated with agriculture development. More broadly, they confirm that crop-livestock integration in croplands is a successful strategy to regenerate SOC.
... There is growing interest in sustainable soil management practices that promote soil carbon sequestration (Guo and Gifford, 2002;Kämpf et al., 2016;Minasny et al., 2017). Best practices in this area aim to achieve a positive balance in soil organic carbon (SOC) stock by increasing organic C inputs and/or reducing SOC degradation processes. ...
Carbon sequestration in soil has been extensively sought in the agroecosystems through practices which increase organic carbon inputs and/or decrease soil organic carbon (SOC) degradation processes. Less is known about the extent of shallow water table influences in mineral soils, despite being soil moisture a major driver in modifying the C cycle. To examine its effects, a 4-yr lysimetric experiment was set up to measure the C balance components under free drainage and shallow water table at 60 and 120 cm depth. Two levels of N input (250 and 368 kg N ha − 1 y − 1) were also studied, using dry manure in 2011 and 2012 and fresh manure in 2013 and 2014. Carbon balance was estimated through the difference between inputs (C from organic inputs and root residues and exudates) and outputs (heterotrophic respiration, methane, and C leaching). A negative C balance was measured under all treatments (− 3487 kg C ha-1), being respiration not compensated by the consistent C input of organic fertilizer. Furthermore, high N inputs increased SOC mineralization, decreasing the C balance. The role of soil was also observed by the SOC analyses, which confirmed the losses estimated through C balance. The study substantiated also the interacting effect between shallow water table and type of organic carbon, which was revealed crucial for C balance in mineral soils. To conclude, results suggested that water table level around 120-cm depth could limit SOC depletion.
... Soil organic carbon stocks (Mg ha − 1 ) were calculated using the SOC concentration (g kg − 1 ), soil thickness (D, cm), and bulk density (BD, g cm − 3 ) at each site (Guo and Gifford, 2002): ...
A R T I C L E I N F O Keywords: Vegetation succession Recalcitrant organic carbon Soil organic carbon fractions Stable C pools Carbon pools management index A B S T R A C T Vegetation restoration effectively promotes soil quality and enhances soil organic carbon (SOC) sequestration. However, the dynamics and driving factors of SOC fractions during long-term vegetation succession remain unclear. In this study, a complete ~ 160 years successional chronosequence from farmland to climax forest was used to study the dynamics and driving factors of SOC fractions in topsoil (0-20 cm) and subsoil (20-40 cm). The results showed that vegetation succession age significantly affected the SOC and its fractions (p < 0.05). The content of SOC fractions increased with succession age, especially recalcitrant organic carbon (ROC), which accounted for 62%-85% of the total SOC. Long-term vegetation succession enhanced the stability of SOC pools, reduced the proportion of active C, and facilitated the fixation of C. ROC was the best indicator of SOC accumulation within the entire profile. When vegetation succession reached the pioneer forest stage (~110 years), the SOC content and fractions increased significantly (p < 0.05) owing to continuous plant biomass inputs. Moreover, soil C sequestration was controlled by total nitrogen content in the topsoil and by belowground biomass in the subsoil. This study indicates that long-term vegetation succession can effectively improve SOC accumulation and SOC pool quality, emphasizing the need to focus on SOC pool stabilization mechanisms under future climate change.
... Following the IPCC's methodologies (IPCC, 2019), we consider that during land conversion, all carbon contained in the above-ground biomass is emitted in the form of CO 2 . In addition, we assume that 22% of soil organic carbon is emitted; this is a low-range estimate from the literature and based on meta-analyses conducted by Murty et al. (2002) and Guo and Gifford (2002). Land type-specific above-ground biomass data are taken from the IPCC (2019), and soil carbon data is taken from the Harmonized World Soil Database published by the Food and Agricultural Organization of the United Nations (FAO) and other international research organizations (FAO, 2008). ...
Reaching Indonesia’s target of net-zero greenhouse gas (GHG) emissions by 2060 or sooner will depend in part on the decarbonization of the transportation sector, which today is responsible for about 15% of the country’s GHG emissions. Indonesia is considering a range of measures, including shifting from gasoline and diesel internal combustion engine vehicles (ICEVs) to hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), and hydrogen fuel cell electric vehicles (FCEVs), and increasing the use of biofuels.
This report presents a life-cycle assessment (LCA) of the GHG emissions of passenger cars and two-wheelers with different power trains in Indonesia. It assesses vehicles sold in 2023 and hypothetical vehicles sold in 2030, and encompasses emissions from fuel combustion, fuel and electricity production, vehicle maintenance, and vehicle and battery manufacturing. The assessment finds that BEVs offer the lowest life-cycle emissions across all segments and can bring significant emissions reduction in line with the net-zero goal. Importantly, as the electricity mix is expected to decarbonize over time, the GHG emission benefit continuously increases for future BEVs, as illustrated in the figure below. HEVs and PHEVs, meanwhile, do not offer a deep reduction in emissions from the passenger car and two-wheeler fleets in Indonesia, as they remain largely dependent on the combustion of fossil fuels. The findings reflect the same trends observed in previous ICCT analyses of vehicles in China, Europe, India, and the United States.
This report is a valuable resource for policymakers in Indonesia, as reducing transport emissions while the vehicle fleet is likely to expand due to economic growth requires a resolute shift to low-carbon technologies. The authors highlight that with a vehicle lifetime of more than 18 years, a transition to a fully electric fleet by 2060 thus requires that from around 2040, no new combustion engine cars, HEVs, or PHEVs are sold in Indonesia. Beyond GHG emissions, increasing the share of electric vehicles will help mitigate the public health and environmental consequences of air pollution in Indonesian cities, reduce Indonesia’s dependence on oil imports, and reduce public spending on fuel subsidies. As Indonesia is the world’s largest supplier of nickel and has rich reserves of other key battery materials, creating a domestic battery and electric vehicle manufacturing industry is expected to create jobs and grow the economy. The report explores policy options to continuously increase the electric vehicle share in Indonesia and support the development of a domestic battery and electric vehicle supply chain.
... To do this, we first estimated spatial changes in cropland extent at a 2.25 km 2 resolution using satellite data from 2002 to 2012 (MODIS; [28]). We then overlaid this historic spatial change in cropland extent with estimates of above-ground and belowground C stores in natural land covers based on IPCC Tier 1 methodology [29,30], further 40% of soil organic C stores are lost following conversion to agriculture, which is in line with recent estimates of the proportion of soil organic C stores lost following conversion from forest to cropland [31]. This allowed us to derive country-specific estimates of average C stores per hectare in areas that experienced cropland expansion or abandonment in the ten years between 2002 and 2012 (i.e., a different value for cropland expansion and cropland abandonment for each country). ...
Most climate mitigation scenarios point to a combination of GHG emission reductions and CO 2 removal for avoiding the most dangerous climate change impacts this century. The global food system is responsible for ~1/3 of GHG emissions and thus plays an important role in reaching emission targets. Consumers, technology innovation, industry, and agricultural practices offer various degrees of opportunity to reduce emissions and remove CO 2 . However, a question remains as to whether food system transformation can achieve net negative emissions (i.e., where GHG sinks exceed sources sector wide) and what the capacity of the different levers may be. We use a global food system model to explore the influence of consumer choice, climate-smart agro-industrial technologies, and food waste reductions for achieving net negative emissions for the year 2050. We analyze an array of scenarios under the conditions of full yield gap closures and caloric demands in a world with 10 billion people. Our results reveal a high-end capacity of 33 gigatonnes of net negative emissions per annum via complete food system transformation, which assumes full global deployment of behavioral-, management- and technology-based interventions. The most promising technologies for achieving net negative emissions include hydrogen-powered fertilizer production, livestock feeds, organic and inorganic soil amendments, agroforestry, and sustainable seafood harvesting practices. On the consumer side, adopting flexitarian diets cannot achieve full decarbonization of the food system but has the potential to increase the magnitude of net negative emissions when combined with technology scale-up. GHG reductions ascribed to a mixture of technology deployment and dietary shifts emerge for many different countries, with areas of high ruminant production and non-intensive agricultural systems showing the greatest per capita benefits. This analysis highlights potential for future food systems to achieve net negative emissions using multifaceted “cradle-to-grave” and “land-to-sea” emission reduction strategies that embrace emerging climate-smart agro-industrial technologies.
... In this regard, a land use type that can improve SOC and soil N accumulation and protect against the loss of cations through leaching and biological processes should be promoted for better land management and to fght against the undesirable impacts of climate change as well [62,63]. Tus, appropriate management intervention such as controlled or rotational grazing, optimizing livestock number, and addition of organic inputs should be applied to enhance C stock and N stock in grassland [41,64]. Similarly, suitable practices such as conservation tillage, zero tillage, terrace farming, and agroforestry practices should be practiced to improve the carbon storage capacity of cultivated land [36,59,65,66]. ...
Understanding the role of soil carbon (C) dynamics and quantitative changes as affected by various land use patterns is very critical given the significance of carbon sequestration. In this context, the current study was conducted in the Lal Bakaiya watershed in Makawanpur District, Nepal, to assess the variation of soil organic carbon (SOC) and nitrogen (N) stocks in three different land use types, namely, natural forest, grassland, and cultivated land. Incremental soil depths method (i.e., 0–15 cm, 16–30 cm, and 31–45 cm) was applied to collect soil samples in bulk from each of the land use under the study to estimate SOC and N stocks in laboratory. A total of 90 soil samples were collected from three soil layers down the soil profile up to 45 cm for each land uses. The results show that both SOC and N contents decreased with soil depths; however, substantial amount of SOC and N stocks were reported in lower soil depths under land use with natural forest. Both SOC and N contents were found relatively higher at 0–15 cm depth in natural forest soil (1.40 ± 0.20% and 0.26 ± 0.04%) than those in grassland and cultivated land, respectively. The mean total SOC stock and N stock ranged from 46.3 ± 4.24 t ha−1 and 7.11 ± 1.86 t ha−1 in cultivated land to 62.05 ± 9.17 t ha−1 and 11.40 ± 1.92 t ha−1 in the land use with natural forest, respectively. Furthermore, the mean total carbon and nitrogen ratio (C/N ratio) of the soil was found to be higher in cultivated land (7.07 ± 1.93) than that in natural forest (5.75 ± 1.47) and grassland (5.62 ± 1.49), respectively. Two-way analysis of variance results showed that both land use type and soil depth have significantly ( p < 0.05 ) affected the SOC and N stocks in the study. From the results, it is suggested that well-managed land use can contribute significantly in offsetting global carbon emission.
... The perspectives for the use of conservation farming and advanced land use technologies in the management of C sequestration and storage has been the subject of numerous articles in recent years [1][2][3][4][5][6]. As noted by Chenu et al. [1], the term «sequestration», representing negative emission technology, denotes a relatively long duration period, at least 20 years based on the recommendations of the Intergovernmental Panel on Climate Change (IPCC). ...
Arable Сhernozems with high SOC contents have the potential to be significant sources of GHGs, and climate change is likely to increase SOC losses, making the issue of carbon sequestration in this region even more important. The prospect of maintaining SOC stock or increasing it by 4% an-nually under planned management practice modifications for the period up to 2090 was evaluated using a long-term experiment on Haplic Chernozem in the Rostov Region, Russia. In this study, we used the RothC model to evaluate SOC dynamics for three treatments with mineral and organic fertilization under two adaptation scenarios vs. business as usual, as well as under two climate change scenarios. Correction of crop rotation and the application of organic fertilizers at high rates are essential tools for maintaining and increasing SOC stocks. This can maintain SOC stock at the level of 84–87 Mg∙ha-1 until the middle of the 21st century, as the first half of the century is con-sidered the most promising period for the introduction of adaptation measures for the additional accumulation of SOC on Chernozems. Part of the additional accumulated SOC is expected to be lost before 2090.
... For example, Wu 29 estimated that for every 1 hectare of cropland in the United States that is placed in reserve, 0.2 hectare of non-cropland is converted to cropland. Land use conversion is likely to reduce SOC stocks 6,30 , and counteract some of the benefit from setting-aside cropland into reserve. ...
Natural climate solutions provide opportunities to reduce greenhouse gas emissions and the United States is among a growing number of countries promoting storage of carbon in agricultural soils as part of the climate solution. Historical patterns of soil organic carbon (SOC) stock changes provide context about mitigation potential. Therefore, our objective was to quantify the influence of climate-smart soil practices on SOC stock changes in the top 30 cm of mineral soils for croplands in the United States using the DayCent Ecosystem Model. We estimated that SOC stocks increased annually in US croplands from 1995 to 2015, with the largest increase in 1996 of 16.6 Mt C (95% confidence interval ranging from 6.1 to 28.2 Mt CO2 eq.) and the lowest increase in 2015 of 10.6 Mt C (95% confidence interval ranging from − 1.8 to 22.2 Mt C). Most climate-smart soil practices contributed to increases in SOC stocks except for winter cover crops, which had a negligible impact due to a relatively small area with cover crop adoption. Our study suggests that there is potential for enhancing C sinks in cropland soils of the United States although some of the potential has been realized due to past adoption of climate-smart soil practices.
... During the 20th century, the decrease in agricultural land reached a huge scale, the area of land decreased by 2.2 million km 2 , and the largest amount of land (up to 706 thousand km 2 ) was reduced in Russia [30]. The forest zone of the European territory of Russia is characterized by the conversion of arable land to pasture, as well as self-restoration to woodland; with such transformations of the landscape, there is an active deposition of soil organic matter [40][41][42]. The organic matter transformation rate (mineralization and humification) depends on multiple factors-quantity and quality of organic matter, soil type, particle size distribution, temperature, and water regime [32]. ...
The fallow agricultural soils of Northwest Russia represent an evolutionary model of the development of ecosystem components in time and space with multidirectional dynamics of agrogenic impact during the long history of agricultural land development. There has been both large-scale land development and uncontrolled conversion of arable lands to a fallow state along with their removal in recent times. All this has led to the formation of a chrono-series of different-age soils with varying degrees of exposure of agrogenic factors. This paper presents a current review of the humus state of fallow soils in Northwest Russia, and examines the main factors (self-restoration, humus transformation, acidification) influencing the transformation of the soil cover under the process of post-agrogenesis. Effective farming techniques aimed at fixing carbon in soils as part of increasing the sequestration potential to mitigate the impact of climate change are considered. The ongoing process of the transition of lands into a fallow state could lead to organic carbon losses and changes in the main physical and chemical parameters, which negatively affects the self-restoration of fallow lands. We offer some recommendations for the effective rewetting of fallow lands in Northwest Russia with the purpose of carbon sequestration in the soil cover.
Soil erosion has contributed to loss of enormous amounts of top soil worldwide. Since the exact quantification of soil erosion is impossible, numerous researchers across the world have used prediction-based models (such as Revised Universal Soil Loss Equation, RUSLE) for assessing the temporal context of soil erosion at the catchment-scale. This paper has tried to integrate the RUSLE-based empirical soil erosion model and landscape ecology for the soils of a tropical river basin in Eastern India. It is observed that more than 60% of the areas in the studied basin are presently witnessing erosion greater than 11.2 tons/ha/year, which is above the tolerable limit as proposed by Food and Agricultural Organization (FAO). The process was applied for 2011 and 2021 and it was observed that soil erosion was augmented by about 6% during this period. Landscape ecological metrices reveal that the patches of high erosion are getting clustered and coalesced and becoming larger in areal extent, especially in the upper and middle domains of the studied basin. This paper, with the help of the soil erosion status of 2011 and 2021, has tried to predict the future scenario of soil erosion in the next five decades (2021 – 2071) with the help of the Artificial Neural Network, a popular deep learning technology. It is found that if erosion continues at the present rate, the patches may increase in extent by about 50% in the next five decades, which is detrimental. Finally, it is recognized that due to the lower clay content (< 30%) in the upper and middle domains of the basin, the study suggests the use of plot-scale mulching technique as an efficient measure to combat soil erosion in the region.
Introduction
Reforestation is a widely used strategy for ecological restoration in areas facing ecological degradation. Soil bacteria regulate many functional processes in terrestrial ecosystems; however, how they respond to reforestation processes in surface and deep soils remains unclear.
Methods
Artificial Robinia pseudoacacia plantation with different stand ages (8, 22, and 32 years) in a typical fallow forest on the Loess Plateau was selected to explore the differential response of soil bacterial community to reforestation in different soil depths (surface 0–200 cm, middle 200–500 cm, and deep 500-100 cm). Soil bacterial diversity, community composition and the co-occurrence patterns, as well as the functions were analyzed.
Results and discussion
The results showed that alpha diversity and the presence of biomarkers (keynote species) decreased with the increasing soil depth, with a sharp reduction in family-level biomarker numbers in 500–1,000 cm depth, while reforestation had a positive impact on bacterial alpha diversity and biomarkers. Reforestation induced a more loosely connected bacterial community, as evidenced by an increase of 9.38, 22.87, and 37.26% in the average path length of the co-occurrence network in all three soil layers, compared to farmland. In addition, reforestation reduced the hierarchy and complexity but increased the modularity of the co-occurrence network in top and deep soil layers. Reforestation also led to enrichment in the relative abundance of functional pathways in all soil layers. This study sheds light on the strategies employed by deep soil bacteria in response to reforestation and underscores the significant potential of deep soil bacteria in terrestrial ecosystems, particularly in the context of human-induced environmental changes.
Despite optical remote sensing (and the spectral vegetation indices) contributions to digital soil-mapping studies of soil organic carbon (SOC), few studies have used active radar remote sensing mission data like that from synthetic aperture radar (SAR) sensors to predict SOC. Bearing in mind the importance of SOC mapping for agricultural, ecological, and climate interests and also the recently developed methods for vegetation monitoring using Sentinel-1 SAR data, in this work, we aimed to take advantage of the high operationality of Sentinel-1 imaging to test the accuracy of SOC prediction at different soil depths using machine learning systems. Using linear, nonlinear, and tree regression-based methods, it was possible to predict the SOC content of soils from western Bahia, Brazil, a region with predominantly sandy soils, using as explanatory variables the SAR vegetation indices. The models fed with SAR sensor polarizations and vegetation indices produced more accurate results for the topsoil layers (0–5 cm and 5–10 cm in depth). In these superficial layers, the models achieved an RMSE in the order of 5.0 g kg−1 and an R2 ranging from 0.16 to 0.24, therefore explaining about 20% of SOC variability using only Sentinel-1 predictors.
The understanding of soil organic carbon (SOC) storage in agroecosystems are limited in southern Thailand. This study was performed to investigate the amount of SOC storage in the agroecosystem of local durian (Durio zibethinus) and rubber tree (Hevea brasiliensis) plantation in Ban Ta Khun District, Surat Thani Province. Soil samples were collected by non-disruptive and destructive methods at a depth of 0-30 cm from 3 stations of each agroecosystem in July and September 2022. Physical and chemical soil properties including soil bulk density, texture, pH, and SOC were analyzed. The results revealed that most of the soil texture in the local durian
plot was sandy clay loam. The average soil bulk density ranged from 0.97-1.10 g/cm3, soil pH was moderately acid to very strongly acid (pH 4.62- 5.96), the SOC storage and soil organic matter (SOM) were 23.40-72.66 g C/m2
and 1.11-3.31%, respectively. On the other hand, in the rubber plot, the soil texture was silty clay with soil pH that was strongly acid to very strongly acid (4.60-5.39). The bulk density of the soil was in the range of 1.24-1.34 g/cm3. The SOC storage and SOM were 17.21-46.90 gC/ m2 and 0.84-2.10%, respectively. The SOC concentrations were positively correlated with soil moisture (P<0.01; R=0.45), pH (P<0.01; R=0.49), and sand particles (P<0.05; R=0.68), but a negative correlation with silt (P<0.05; R=-0.68) and clay (P<0.01; R=-0.82). However, there was no correlation between the SOC concentration and bulk density nor between SOC and soil electrical conductivity.
Understanding the characteristics and driving factors of soil carbon, nitrogen, phosphorus, and enzyme stoichiometry during land use/cover change is of great significance for assessing microbial nutrient restriction and sustainable land development during the process. China, the world’s largest tea producer, is witnessing a significant expansion of tea plantations into previously forested areas. We performed field sampling in three forest types with the area partially converted to tea plantations in Wuyishan National Park. We examined the changes in soil carbon (TC), nitrogen (TN), phosphorus (TP), and three kinds of extracellular enzyme activities, β-glucosidase (BG), β-n-acetylglucosidase (NAG), and acid phosphatase (ACP). By analyzing the enzyme stoichiometric ratio, vector length (VL), and vector angle (VA), the relative nutrient limitations of soil microorganisms were explored. The results showed that soil TC and TN decreased significantly (p < 0.05), TP increased significantly, and soil carbon (C):nitrogen (N), carbon (C):phosphorus (P), and nitrogen (N):phosphorus (P) ratios decreased significantly after the conversion of forest land to tea plantation. Soil BG, NAG, and ACP contents decreased significantly (p < 0.05). There were no significant differences in enzyme carbon:nitrogen ratios (EC/N), enzyme carbon:phosphorus ratios (EC/P), enzyme nitrogen:phosphorus ratios (EN/P), VL, or VA (p > 0.05). Through the analysis of soil enzyme stoichiometry, it was found that forest soil was generally limited by P, which was, to some extent, relieved after the conversion to tea plantation. Redundancy analysis showed that TC, TN, and the C:N ratio were the main factors influencing enzyme activity and stoichiometry. These results indicated that land use/cover change had significant effects on soil nutrient status, enzyme activity, and stoichiometry. Soil enzyme activity is very sensitive to the changes in soil nutrients and can reflect the restriction of soil nutrients more accurately.
This study aimed to investigate the effect of conversion from natural forest to cinnamon plantation on the top 1 m soil carbon stocks and soil characteristics. The project was conducted on Andosols of Kerinci Regency, Sumatera, Indonesia, sampling the soil profile under natural forests and a chronosequence of cinnamon plantations of different ages (1, 5 and 10 years). SOC stocks were quantified alongside physical properties (bulk density) and chemical properties (carbon, nitrogen, C/N ratio) to investigate the impact of land conversion. SOC stocks increased one year after conversion to cinnamon plantations, but then tended to decrease as the plantations got older. The initial increase was observed alongside decreasing bulk density one year after forest conversion to cinnamon plantation, likely as a result of the fresh input of (less dense) pyrogenic soil organic matter due to slash and burn practices and transport down the soil profile due to leaching. In older plantations SOC stocks were lower, probably because organic matter had been decomposed or leached out of the profile. The free particulate organic matter (fPOM) was isolated from selected topsoil and subsoil layers and analysed for carbon, nitrogen, and FTIR analysis. FTIR analysis revealed that topsoil fPOM contained more aromatic functional groups than subsoils and had a higher degree of decomposition. Aromatic and carbohydrate functional groups were initially lower in recently converted cinnamon plantation, but the trend was reversed 10 years after conversion. The initial flush of fresh organic matter into soils after slash and burn provides fPOM with a lower degree of decomposition but is short‐lived and fPOM becomes more microbially processed as the cinnamon plantation ages. We conclude that, after a short term increase brought about by slash and burn, forest conversion to cinnamon plantation in Kerinci Regency depletes SOC stocks both in topsoil and subsoil.
Forest degradation is increasingly recognized as a major threat to global biodiversity and ecosystems’ capacity to provide ecosystem services. This study examined the impacts of forest degradation on soil quality and function in a seasonally dry tropical forest (SDTF) of Ecuador. We compared soil physical-chemical properties, enzymatic activity, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) along a gradient of SDTF degradation in the dry and rainy season. Our findings showed a consistent and steady reduction in soil quality (total C and N) and function (dehydrogenase and β-glucosidase activity) that paralleled the loss of vegetative structure and diversity along the degradation gradient. Soil physical-chemical properties were less variable and enzymatic activity was generally higher in the dry season compared to the rainy season. We also showed for the first time a significant and uniform decrease in POC and MAOC with ecosystem degradation in a SDTF. The relative proportion of these two components was constant along the gradient except for the most degraded state (arid land), where POC was higher in proportion to MAOC, suggesting that a functional tipping point may be crossed with extreme forest degradation. These findings address an important knowledge gap for SDTFs by showing a consistent loss of soil quality and functionality with degradation and suggest that extreme degradation can result in an alternate state with compromised resilience.
Land-use systems (LUSs) and soil types (STs) are strongly related to factors that influence soil degradation and carbon (C) loss. However, the way in which land use and soil type affects the soil organic C (SOC) pools, and soil aggregation in the Sanjiang Plain, has not been thoroughly investigated. Therefore, this study aimed to investigate soil physic–ochemical properties, soil aggregates, and C management index (CMI) in three different LUSs (grassland, dryland, and paddy field) under two STs (meadow soil and albic soil) of the Sanjiang Plain in northeast China. A total of 60 composite soil samples were collected for laboratory analyses. The results were as follows: soil properties were affected by LUS and ST, especially soil chemical properties; ST had no significant effect on soil aggregates but significantly affected its SOC content, while LUS had a significant effect on soil aggregates (p < 0.01), except for small macro-aggregates (2–0.25 mm); the mean weight diameter (MWD) and SOC in meadow soil was significantly different under different land uses, with grassland being the highest and dryland the lowest. However, there was no significant difference in albic soil. The heterogeneity of grassland, dryland, and paddy field showed that different LUSs had particular effects on SOC and its active components because LUS had significant effects on C pool index (CPI) and CMI, but ST and its interaction had no significant effects on CPI and CMI. Overall, the results showed that LUS was an important factor affecting CMI in the Sanjiang Plain, rather than ST, and the paddy field CMI was optimal in the Sanjiang Plain.
Le sol est la meilleure alternative aux gaz à effet de serre car, selon le GIEC, il constitue le plus important réservoir superficiel à carbone avec plus de 1500 à 2000 Gigatonnes de carbone captés par année. Pendant longtemps, l’évaluation du potentiel de stockage en carbone organique dans les sols du Gabon a été exclusivement orientée dans le milieu forestier. Cette étude vise à évaluer le potentiel en carbone organique des sols dans la province de l’Estuaire, selon 7 types d’occupations des sols, définit par l’Agence Gabonaise d’Etudes et Observations Spatiale (AGEOS). Nous avons comparé les sols sous terres cultivées (TC ; n=11), sous bâtis (BT ; n=12), sous cultures villageoises (CV ; n=8), sous savanes et végétations basses (SVB ; n=6), sous forêts inondées (FI ; n=9), sous forêts secondaires (FS ; n=12), à ceux sous forêts matures (FM ; n =14). Les sols ont été prélevés (n=864) sur une profondeur de 0 à 100 cm avec un pas régulier de 20 cm. Les résultats d’analyses ont montré des spécificités géographique et géologique dans les sols des sites échantillonnés. En effet, tous les sols sont acides (pH<5,01), et les sites proches du littoral (BT, SVB, FI et CV) sont fortement désaturés et remaniés, subissant une forte pluviométrie annuelle (3500 mm à 3000 mm), avec des densités apparentes les plus importantes, mais les teneurs en carbone organique totale (COT) les plus faibles. Tandis que les sites plus éloignés du littoral (FM, FS et TC) reposent sur un socle cristallin, subissent une pluviométrie moins importante (2500 mm à 3000 mm), possèdent des densités apparentes les plus faibles et les teneurs en COT les plus importantes. De plus, la texture argilo-limoneuse à argileuse des sols des sites FM, FS, et TC permet un stockage plus important en COT que la texture sableuse à sablo-limoneuse des sols des sites BT, SVB, FI et CV. English title: Evaluation of the organic carbon of the soils of the province of Estuaire (NW, Gabon) according to the type of occupation Soil is the best alternative to greenhouse gases because, according to the IPCC, it is the largest superficial carbon reservoir with more than 1500 to 2000 Gigatons of carbon captured per year (IPCC). For a long time, the evaluation of the organic carbon storage potential in the soils of Gabon was exclusively oriented in the forest environment. This study aims to assess the organic carbon potential of soils in the Estuary province, according to 7 types of land use, defined by the Gabonese Agency for Spatial Studies and Observations (AGEOS). We compared the soils under cultivated land (TC; n=11), under buildings (BT; n=12), under village crops (CV; n=8), under savannas and low vegetation (SVB; n=6), under flooded forests (FI; n=9), under secondary forests (FS; n=12), to those under mature forests (FM; n=14). The soils were sampled (n=864) over a depth of 0 to 100 cm with a regular step of 20 cm. The analysis results showed geographical and geological specificities in the soils of the sampled sites. Indeed, all the soils are acidic (pH<5.01), and the sites near the coast (BT, SVB, FI and CV) are highly desaturated and reworked, undergoing high annual rainfall (3500 mm to 3000 mm), with the highest apparent densities, but the lowest total organic carbon (TOC) contents. While the sites farther from the coast (FM, FS and TC) rest on a crystalline basement, experience less rainfall (2500 mm to 3000 mm), have the lowest apparent densities and the highest TOC contents. In addition, the clayey-loamy to clayey texture of the soils of the FM, FS, and TC sites allows greater TOC storage than the sandy to sandy-loamy texture of the soils of the BT, SVB, FI and CV sites.
Examination of greenhouse gas (GHG) fluxes (CO2, CH4, and N2O) in soils is crucial for developing effective strategies to mitigate climate change. In this study, we investigated the GHG fluxes in agricultural and forest soils to explore the changes in soil GHG fluxes, and assess the relationships of GHGs with other physico-chemical properties. Results show that forest soils have a higher CO2 flux, while agricultural soils have a higher N2O flux due to fertilizer application and heterotrophic nitrification. Forest soils act as a CH4 sink, which are connected with increased porosity and decreased bulk density. In agricultural soils, CO2 and N2O were strongly linked with NH4+, soil temperature, pH, soil organic carbon, total nitrogen, plant-available phosphorous, and microbial biomass nitrogen (mbN) but were negatively connected with bulk density and microbial biomass carbon (mbC). In contrast to CO2 and N2O, CH4 in agricultural soils exhibited inverse relationships with all physico-chemical properties. In forest soils, CO2 and CH4 were positively correlated with soil temperature and mbC, and mbN and N2O were negatively correlated with bulk density and pH. This study highlights the critical need to comprehend the complex relationship between soil physico-chemical properties and GHG fluxes for effective climate change mitigation.
The current stock of organic carbon in Indian soils (24.3 Pg) can be increased to 34.9 Pg, the difference representing the potential for sequestering additional carbon in soils. Reforestation of 35 m ha of wastelands with suitable tree and grass species can sequester 0.84 and 1.06 Pg of carbon in vegetation and soil respectively. Restoration, maintenance and enlarging the carbon stocks of Indian soils are an urgent developmental priority. -Authors
Selected chemical, biochemical and biological properties of mineral soil (0–30 cm) were measured under a 19 year old forest
stand (mixture of Pinus ponderosa and Pinus nigra) and adjacent unimproved grassland at a site in South Island, New Zealand. The effects of afforestation on soil properties
were confined to the 0–10 cm layer, which reflected the distribution of fine roots (< 2 mm) in the soil profile. Concentrations
of organic C, total N and P and all organic forms of P were lower under the forest stand, while concentrations of inorganic
P were higher under forest compared with grassland, supporting the previously described suggestion that afforestation may
promote mineralisation of soil organic matter and organic P. On the other hand, microbial biomass C and P, soil respiration
and phosphatase enzyme activity were currently all lower and the metabolic quotient was higher in soil under forest compared
with grassland, which is inconsistent with increased mineralisation in the forest soil. Reduced biological fertility by afforestation
may be mainly attributed to changes in the quantity, quality and distribution of organic matter, and reduction in pH of the
forest soil compared with the grassland soil. We hypothesize that the lower levels of C, N and organic P found in soil under
forest are due to enhanced microbial and phosphatase activity during the earlier stages of forest development. Forest floor
material (L and F layer) contained large amounts of C, N and P, together with high levels of microbial and phosphatase enzyme
activity. Thus, the forest floor may be an important source of nutrients for plant growth and balance the apparent reduction
in C, N and P in mineral soil through mineralisation and plant uptake.
The influence of agricultural production systems on greenhouse gas generation and emission is of interest as it may affect
potential global climate change. Agricultural ecosystems can play a significant role in production and consumption of greenhouse
gases, specifically, carbon dioxide. Information is needed on the mechanism and magnitude of gas generation and emission from
agricultural soils with specific emphasis on tillage mechanisms. This work evaluated four different tillage methods on the
short-term CO2 and water vapor flux from a clay loam soil in the Northern Cornbelt of the USA. The four tillage methods were moldboard plow
only, moldboard plow plus disk harrow twice, disk harrow and chisel plow using standard tillage equipment following a wheat
(Triticum aestivum L.) crop compared with no tillage. The CO2 flux was measured with a large portable chamber commonly used to measure crop canopy gas exchange initiated within 5 minutes
after tillage and continued intermittently for 19 days. The moldboard plow treatment buried nearly all of the residue and
left the soil in a rough, loose, open condition and resulted in maximum CO2 loss. The carbon released as CO2 during the 19 days following the moldboard plow, moldboard plow plus disk harrow, disk harrow, chisel plow and not tilled
treatments would account for 134%, 70%, 58%, 54% and 27% respectively of the carbon in the current year's crop residue. The
short-term carbon dioxide losses 5 hours after four conservation tillage tools was only 31% of that of the moldboard plow.
The moldboard plow lost 13.8 times as much CO2 as the soil area not tilled while different conservation tillage tools lost only 4.3 times. The smaller CO2 loss following conservation tillage tools is significant and suggests progress in developing conservation tillage tools that
can enhance soil carbon management. Conservation tillage reduces the extent, frequency and magnitude of mechanical disturbance
caused by the moldboard plow and reduces the air-filled macropores and slows the rate of carbon oxidation. Any effort to decrease
tillage intensity and maximize residue return should result in carbon sequestration for enhanced environmental quality.
An analysis of C pools at the Panola Mountain Research Watershed (PMRW) near Atlanta, GA, indicates that aggrading forests in the U.S. Southeast are an important regional C sink. The forests in this area were cut in the early 1800s and the land was cultivated until the early 1900s, when farming was abandoned and forest regeneration began. Cultivation resulted in extensive erosion, which depleted soil C pools. The rate of soil C sequestration during the 70-yr period of forest regeneration was estimated to be between 0.34 (standard error [SE] = 0.12) and 0.79 (SE = 0.19) Mg C ha -1 yr -1 . There is a large potential for continued C accumulation in the soil at PMRW based on the difference between current measured soil C pools of 82 Mg C ha -1 at PMRW and 122 Mg C ha -1 at the nearby undisturbed Fernbank Forest in Atlanta, GA. The rate of C sequestration in biomass at PMRW was 1.47 Mg C ha -1 yr -1 for the regeneration period, bringing the ecosystem total to between 1.81 and 2.26 Mg C ha -1 yr -1 . Carbon sequestration in temperate forest ecosystems partially mitigates the effects of increased atmospheric loading of CO 2 .
Evaluation of the effects of cultivation on soil properties in Ustic Mollisols has generally been limited to surface horizons. To examine the effects of cultivation on both surface and subsurface horizons, six paired virgin and cultivated pedons of Williams soil (fineloamy, mixed Typic Argiboroll) or variants of Williams from northcentral South Dakota were compared for differences in various chemical and physical properties. When similar horizons were compared, chemical differences between cultivated and virgin pedons averaged as follows: (i) organic C content was 26% less in Ap horizons; (ii) water‐soluble Si was 49, 46, and 21% greater in A, Bt, and Btk horizons of cultivated pedons, respectively; (iii) water‐soluble Mg, Na, and K were 42, 32, and 18% lower in C horizons of cultivated pedons, respectively; (iv) oxalate‐extractable Fe was 28 and 56% higher in Ap and Bt horizons of cultivated pedons, respectively. When similar horizons were compared, physical differences between cultivated and virgin pedons averaged as follows: (i) bulk density was 18% greater in Ap horizons; (ii) Ap horizons contained 38% more very fine sand and 10% less silt; (iii) A and Btk horizons of virgin pedons possessed greater wet aggregate stability; and (iv) A horizons of virgin pedons average 30% more water retained at 0 MPa tension.
Some properties of surface mineral soils under Pinus radiata were compared with those under adjacent pasture at ten farm‐forestry sites in the Manawatu, New Zealand. None of the sites had received lime in the last 10 years. Generally, the soil samples under P. radiata had lower pH and higher extractable aluminium concentrations than their counterparts under pasture. Exchangeable calcium values were lower under P. radiata, by 96–1275 kg/ha. Tree uptake and forest floor development can account for up to 550 kg/ha; at six sites the difference was less than 550 kg/ha, suggesting that calcium generally was conserved by the P. radiata ecosystem. Soil exchangeable sodium and magnesium values were usually greater under P. radiata than under pasture; this probably resulted from the interception of airborne sea‐salt by the P. radiata canopy and subsequent transfer to the soil. There were no general trends in the data for available phosphorus and exchangeable potassium. Total nitrogen was often lower in the samples under P. radiata, and the C/N ratio was generally greater under P. radiata. Loss of soil nitrogen may arise from elimination of legumes, accumulation by the trees, and possibly by leaching. Mineralisation of nitrogen, together with production of organic acids and uptake of excess cations over anions, may be possible causes of soil acidification.
Measurements of carbon stocks and fluxes in Amazon soils were used to model subsurface carbon cycling for the purpose of predicting carbon fluxes associated with deforestation and subsequent pasture management. Isotopic measurement of soil organic matter and soil carbon dioxide, measurements of aboveground and belowground carbon inputs, and estimates of carbon dioxide production as a function of soil depth were incorporated into a model describing turnover times of years, decades, and more than centuries. In degraded pastures, reduced carbon inputs to the soil were observed to cause a reduction in soil carbon inventory and delta carbon 14. Increases in carbon and carbon 14 were observed in managed pastures, which were fertilized and planted with productive grasses, over forest values. Predicted carbon losses from destruction of forest roots more than one meter deep in the soil partially offset carbon inventory increases in the upper meter of managed pasture soils. The major changes in soil carbon inventory after implementation of land management occur within the first 10 years. Due to this short turnover time, land management is an important factor in determining the effects of land use change on the global carbon budget. 54 refs., 7 figs., 5 tabs.
Soil C and N changes following cessation of cultivation in semiarid soils is not well understood. We hypothesized that returning cultivated fields in southeastern Wyoming to perennial grasses through the Conservation Reserve Program (CRP) would (i) increase labile pools of soil organic matter (SOM), and (ii) increase small-scale heterogeneity of SOM. Carbon and N in labile and passive pools of SOM were measured in CRP fields seeded with perennial grasses intermediate wheatgrass (Elytrigia intermedia [Host] Nevski ssp. intermedia), pubescent wheatgrass (Elytrigia intermedia [Schur.] A. Love ssp. barbulata) and smooth brome (Bromus inermis Leysser), and in winter wheat (Triticum aestivum L.)-fallow fields. Mineralizable C increased from 0.37 g m-2 d-1 in wheat-fallow fields to 0.99 g m-2 d-1 in CRP fields; mineralizable N and coarse particulate C were consistently but not significantly higher in CRP fields. Fine particulate and total soil C and N were not significantly different between CRP and wheat-fallow. Within CRP fields, mineralizable C was significantly higher under grasses than in interspaces (1.96 vs. 0.73 g m-1 d-1, respectively), and mineralizable N and coarse particulate C and N were consistently but not significantly higher under grasses than in interspaces. Soil C and N have increased only slightly after 6 yr of CRP management, and future changes in land use management on these CRP fields, including grazing and cropping, may accrue some small benefits associated with improved soil fertility status.
The influence of climate and soil texture on soil organic matter losses due to cultivation are rarely addressed due to lack of appropri-ately paired sites. In addition, soil organic matter recovery on pre-viously cultivated fields is not well understood. In this study, we identified seven sites that have native and abandoned fields and five sites that have native, abandoned, and cultivated fields. All sites are in the northeastern Colorado shortgrass steppe, crossing a precipitation range from 320 to 370 mm, and have sand contents from 36 to 67%. Historical cultivation reduced soil C and N across this region by between 16 and 42%. Although variation in native soil C and N at these sites correlates with climate and soil texture, variation among sites in soil losses due to cultivation is not explained by these variables. We used a statistical model and a simulation model to estimate patterns of soil loss across sites; neither model predicted variation among sites adequately (P > 0.05). We suggest that local-scale variability in organic matter losses due to cultivation are strongly dependent on management practices. With a simulation model and the data from native, aban-doned, and cultivated fields, we estimated that 25 to 120 g C m" 2 have been recovered on the abandoned fields during the past 50 yr. Such rates of recovery are small compared with loss rates due to cultivation. Rates of soil organic matter recovery are constrained by natural pedogenic processes, which cannot reverse disturbance processes at a comparable rate in this semiarid environment.
Although the effects of cultivation on soil organic matter and nutrient supply capacity are well understood, relatively little work has been done on the long-term recovery of soils from cultivation. We sampled soils from 12 locations within the Pawnee National Grasslands of northeastern Colorado, each having native fields and fields that were historically cultivated but abandoned 50 yr ago. We also sampled fields that had been cultivated for at least 50 yr at 5 of these locations. Our results demonstrated that soil organic matter, silt content, microbial biomass, potentially mineralizable N, and potentially respirable C were significantly lower on cultivated fields than on native fields. Both cultivated and abandoned fields also had significantly lower soil organic matter and silt contents than native fields. Abandoned fields, however, were not significantly different from native fields with respect to microbial biomass, potentially mineralizable N, or respirable C. In addition, we found that the characteristic small-scale heterogeneity of the shortgrass steppe associated with individuals of the dominant plant, Bouteloua gracilis, had recovered on abandoned fields. Soil beneath plant canopies had an average of 200 g/m(2) more C than between-plant locations. We suggest that 50 yr is an adequate time for recovery of active soil organic matter and nutrient availability, but recovery of total soil organic matter pools is a much slower process. Plant population dynamics may play an important role in the recovery of shortgrass steppe ecosystems from disturbance, such that establishment of perennial grasses determines the rate of organic matter recovery.
Afforestation may lead to an accumulation of carbon (C) in vegetation, but little is known about changes in soil C storage with establishment of plantation forests. Plantation forest carbon budget models often omit mineral soil C changes from stand-level C budget calculations, while including forest floor C accumulation, or predict continuous soil C increases over several rotations. We used national soil C databases to quantify differences in soil C content between pasture and exotic pine forest plantations dominated by P. radiata (D. Don), and paired site studies to quantify changes in soil C with conversion of pasture to plantation forest in New Zealand. Overall, mineral soil C to 0.10 m was 20–40% lower under pine for all soil types (p < 0.01) except soils with high clay activity (HCA), where there was no difference. Similar trends were observed in the 0.1–0.3 m layer. Moreover, mineral soil C to 0.1 m was 17–40% lower under pine than pasture in side-by-side comparisons. The only non-significant difference occurred at a site located on a HCA soil ( p = 0.08). When averaged across the site studies and the national databases, the difference in soil C between pasture and pine was about 16 t C ha −1 on non-HCA soils. This is similar to forest floor C averaged across our individual sites (about 20 t C ha −1 ). The decrease in mineral soil C could result in about a 15% reduction in the average C sequestration potential (112 t C ha −1 ) when pasture is converted to exotic plantation forest on non-HCA soils. The relative importance of this change in mineral soil C will likely vary depending on the productivity potential of a site and harvest impacts on the forest floor C pool. Our results emphasize that changes in soil C should be included in any calculations of C sequestration attributed to plantation forestry. DOI: 10.1034/j.1600-0889.1999.00015.x
Soils beneath planted Pinus radiata were compared with soils beneath adjacent native Eucalyptus forest at 2 sites with contrasting nutrient status in New South Wales. At the lower fertility site, soil under P. radiata was lower in N, exchangeable Mg and pH, and higher in organic matter and exchangeable Al than soil under native forest. An apparent deficit in total N in the pine ecosystem could be accounted for by the quantity in thinnings. At the higher fertility site, soil under pine had lower concentrations of nitrogen and organic matter than that under native forest, but was not significantly different in other respects. Organic matter content appeared to be the main soil property influenced by plantation establishment; this effect was more pronounced at the poorer site where rooting depth was limited to 30-40 cm by a sharp change in texture. -from Authors
Increasing population in many tropical countries has encouraged settlement of forest lands. While there is little published data on the ecological impact of settlement, some ecologists have suggested that conversion of forest to agricultural lands may have lasting deleterious effects. For example, Holdridge (1959) and Tosi (1964) have postulated that the change from forest to permanent agriculture in Costa Rica might cause rapid deterioration of the soil. The logical basis for this conclusion is well established. High temperatures cause rapid decomposition of soil and litter organic matter, and high rainfall may cause rapid leaching of nutrients from the soil (Aubert and Tavernier, 1972). Thus removal of forest cover could conceivably result in a decline in soil nutrients, since in the intact forest the nutrients are taken up by vegetation immediately upon their release from decaying organic matter (Richards, 1952). The objective of this work was to compare soil characteristics of permanent agricultural fields and forest. The area chosen for the study was a farming community centered around the Centro Rural Metodista along a ridge in the Canton of San Carlos, 8 km north of Cuidad Quesada (Figure 25-1). Soils under three different crops—sugar cane, coffee, and pasture—were studied. Since forests in this region of Costa Rica were first cleared about 22 years ago by settlers moving from the south, fields ranging in age from 22 years to the present were available for study.
Soil fertility at the Tikitere Agroforestry Research Area near Rotorua has been monitored since the site was planted with Pinus radiata D. Don in 1973. Measurements made in 1991 and 1992 showed that after 18 years soil pH had declined and that Olsen phosphorus levels increased with increased tree stocking. Soil magnesium also declined at the higher tree stocking rates. We made further measurements on samples collected in 1991 and 1992 to determine reasons for the change in nutrient status. Soil carbon and soil organic phosphorus in the surface soil (0-75 mm depth) decreased with tree stocking, indicating increased net mineralisation of soil organic matter under P. radiata compared with pasture. Exchangeable cations and cation exchange capacity also declined with tree stocking, which is consistent with the loss of exchange sites in soil organic matter. Total soil inorganic phosphorus declined with increased tree stocking. This was expected because of reduced fertiliserphosphorus input at the higher stocking rates. However, phosphorus fractionation showed that bicarbonate-extractable inorganic phosphorus increased and acid-extractable inorganic phosphorus declined with tree stocking. The latter indicated possible decreases in soil apatite phosphorus. These results were consistent with the mobilisation of soil phosphorus under P. radiata by dissolution of fluorapatite (in parent material deposited during the 1886 Tarawera eruption) due to lower soil pH values and mineralisation of organic phosphorus previously accumulated under pasture. Consequently, Olsen phosphorus has increased despite reduced phosphorus fertiliser applications. Microbiological activity (as indicated by microbial biomass and microbial respiration) and phosphatase activities of soil samples collected in 1995 also decreased with tree stocking, and so mineralisation of organic matter was not a result of microbial activity alone. However, the proportion of soil aggregates > 0.5 mm decreased under P. radiata, indicating there was less physical protection of the soil organic matter than under pasture where soil aggregates were maintained by fine roots.
Soil chemical properties under grassland were compared with those under adjoining first-rotation pine forest aged 20 and 25 years, at coastal and inland hill country sites in Canterbury, New Zealand. The pasture sites had been treated with fertiliser but not limed. Organic carbon, total nitrogen, sulphur, and phosphorus, and exchangeable potassium, calcium, and magnesium levels were lower in soil beneath forest at one or both of the sites. In contrast, available phosphorus and sulphur concentrations were marginally higher beneath forest at both sites despite fertiliser application to grassland. Mineralisable nitrogen also was higher beneath forest at the inland site, but not at the more agriculturally developed coastal site. Differences between sites for total sulphur and exchangeable magnesium were ascribed to greater atmospheric inputs of these elements to forest at the coastal site. At both sites, soils under forest were more acid and had higher exchangeable aluminum levels. Differences between forest and grassland for organic carbon and total nitrogen and phosphorus were confined to the upper soil layers (0-0.1 m), while differences in soil acidity progressed to a depth of 0.2 m, and differences in exchangeable cations were evident to 0.4 m, the greatest depth measured. Soil (< 2 mm) bulk density and nutrient pools were measured at the coastal site, and bulk density was similar beneath forest and grassland. Total nitrogen and exchangeable potassium and magnesium pools to 0.3 m depth were lower under forest than grassland, while the exchangeable aluminium pool was higher under forest. Organic carbon, total phosphorus and sulphur, and exchangeable calcium pools were similar under the two types of vegetation. Lower concentrations and pools of nutrients in soil beneath forest may have been due to uptake and sequestration of nutrients in forest biomass, or to fertiliser application to grassland, although the latter would have been counteracted to some extent by nutrient removals by grazing animals.
Organic C and natural 13C abundance were measured in a forest soil and a soil under corn (Zea mays L.) to assess management-induced changes in the quantity and initial source of organic matter. The total mass of organic C in the cultivated soil was 19% lower than in the forest soil. It was estimated that after 25 yr of continuous corn, 100 Mg C ha-1 was returned to the soil as residues, of which only 23 Mg ha-1 remained in the soil; 88% of the remaining corn-derived C (C4-derived C) was in the plow layer. About 30% of the soil organic C in the plow layer (0-27 cm) was derived from corn. The mineralization of C from native organic matter associated with the coarse silt fraction was the slowest of all particle-size fractions. -from Authors
Intensively managed plantations of trees occupy vast areas of the tropics. The productivity of these forests depends strongly on nutrient supply, and nutrient supply may change rapidly under intensive management regimes. We documented changes in a Hawaiian soil after 32 mo of development of a plantation of eucalyptus [Eucalyptus saligna (Sm.)]. Soil C did not change significantly (average = -23 g C m-2 yr-1 to 30 cm; 95% confidence -139 to +93 g C m-2 yr-1). This lack of change in soil C resulted from a rapid loss of older soil C derived from sugarcane (-191 g C m-2 yr-1) and a rapid gain of new soil C from eucalyptus (160 g C m-2 yr-1). Soil N declined by 19 g N m-1 yr-1 (P = 0.08), despite fertilizer additions of 31 to 70 g m-2. Large reductions in exchangeable Ca and Mg probably resulted from dissolution and leaching of residual lime from prior agricultural management. We conclude that intensive sampling regimes may detect relatively small changes in tropical forest soils, and that expectations of C accumulation in soils following afforestation may need to be reconsidered.
Soil collected from eight locations under exotic conifers and adjacent undeveloped grasslands in the montane zone of the eastern South Island were analysed. Oslen and Bray-2 extractable phosphorus levels were higher under the conifers than under adjacent grasslands at most sites, with the largest absolute increases occurring under older stands on dry soils of the Mackenzie Basin. Soils of the Canterbury region were characterized by large increases in mineralisable N and in SO4. Soil pH declined under conifers at all sites. Mineralisation of organic matter by the pines appears to be the major mechanism for nutrient enrichment of topsoils in the hygrous soils of Canterbury, but a different process, possibly transfer of nutrients from deeper horizons to the soil surface via nutrient uptake and litterfall, may be more important in the dry-hygrous soils of the Mackenzie Basin. -from Authors
Organic matter in the world’s soils contains about three times as much carbon as the land vegetation. Soil organic matter is labile and is likely to change as a result of human activities. Agricultural clearing, for example, results in a decline in soil organic matter. At the present time, there may be a net release of 0.85 × 1015 g C • yr−1 from soils of the world due to agricultural clearing (Houghton et al. 1983; Schlesinger 1984), or about 15% of the annual release from fossil fuels. The release of carbon may have been greater near the turn of the century as a result of more rapid agricultural expansion into virgin areas (Stuiver 1978, Wilson 1978). It is the purpose of this chapter (1) to review briefly the present estimates of the size of the pool of carbon in world soils and (2) to offer a review and analysis of what is known about the effects of agriculture on soil carbon storage.
Pasture development on cleared forest land has been investigated near Ilha de Maracá in northern Roraima, Brazil. Initial forest clearance and burning in the area is followed by short-term crop cultivation, and conversion to pasture based on introduced grasses such as Panicum maximum and Brachiaria humidicola. Derived pasture is initially productive for cattle grazing, but its quality deteriorates over time as woody weed invasion increases. Even so, the quality of older pastures is variable, apparently as a function of grazing intensity and related management practices. Older pastures also appear to vary in respect of their total soil-plant nutrient content, but this is not directly reflected in soil nutrient levels. Local soils are inherently acid in character; they are not excessively degraded by pasture development, but are generally deficient in available phosphorus which is presumably as limiting to pasture productivity as elsewhere in Amazonia. In general, such pioneer ranching is inappropriate on Amazonian forest land; in places, more sustainable livestock rearing might eventually be developed, but the present ranching system is not in the long-term regional interest.
Analyses of soil samples from paired plots under Pinus radiata D. Don and native eucalypt forests show that important changes in soil properties occur under the pines.
Twenty-six cross-sectional and time series studies of soil properties under natural forest and altered vegetation in the United States and ten tropical countries were examined to determine the changes associated with forest clearing. Organic C, total N, exchangeable Ca, Mg, and K, cation exchange capacity, available P, bulk density, and pH were considered. After forest clearing, only bulk density and available P tended to return to preclearing levels. Losses of organic C, total N, and cation exchange capacity were 50 percent larger in soils developed on highly weathered parent materials in the tropics than in the same soils in the United States or in soils developed on young parent materials. Differences in soil response to clearing were related to local effects of temperature, rainfall, vegetation type, and soil acidity on organic matter decomposition.
As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of this paper are (1) to examine the association of SOC content with climate and soil texture at different soil depths; (2) to test the hypothesis that vegetation type, through patterns of allocation, is a dominant control on the vertical distribution of SOC; and (3) to estimate global SOC storage to 3 m, including an analysis of the potential effects of vegetation change on soil carbon storage. We based our analysis on >2700 soil profiles in three global databases supplemented with data for climate, vegetation, and land use. The analysis focused on mineral soil layers. Plant functional types significantly affected the v...
The response of trees to rising atmospheric CO2 concentration ([CO2]) is of concern to forest ecologists and global carbon modellers and is the focus of an increasing body of research work. I review studies published up to May 1994, and several unpublished works, which reported at least one of the following: net CO2 assimilation (A), stomatal conductance (gs), leaf dark respiration (Rd) leaf nitrogen or specific leaf area (SLA) in woody plants grown at while leaf N was reduced only when expressed on a mass basis. This review is the first meta-analysis of elevated CO2 studies and provides statistical confirmation of several general responses of trees to elevated [CO2]. It also highlights important areas of continued uncertainty in our understanding of these responses.
The productivity of Ferrosols used for rainfed agricultural production in the south and central Burnett regions of south-east Queensland was examined in relation to the duration under continuous cultivation. A range of crops grown in on-farm situations during 1986-90 were examined using paired sites to assess the extent of yield decline with time under cropping. The changes in soil chemical characteristics that have occurred during the cropping period were also assessed. All locations showed evidence of a significant reduction in crop growth (50-100%) where continuously cropped sites were compared with sites which had either never been cropped or which had been under grazed grass pasture for >20 years. In the absence of severe late season water deficits, this reduced growth rate was always reflected in lower (21-72%) crop yields at maturity. However, crop dry matter (DM) could interact with crop water use under conditions of late-season water deficit to negate, or even reverse, early growth advantages on previously untilled soil. At least part of the observed yield reduction on continuously cropped soil was due to nutrient deficiencies resulting from depletion of both surface and subsurface reserves during cropping. Long-term cropping has resulted in depletion of soil K and Zn (especially in the subsoil), organic carbon and total N status, and caused significant acidification of both surface and subsoil layers despite the use of lime. The decline in subsoil K status and falling subsoil pH have severe implications for crop performance in dry seasons, when crops rely on subsoil reserves to sustain crop growth. The decline in soil N status has occurred despite a high frequency (>50%) of grain legumes in the crop rotations practised on all farms monitored, and illustrates the small N return from these crops under rainfed conditions. The reduction in soil organic carbon due to cropping was extreme, with continuously cropped areas having organic carbon levels of only 0.9 to 1.5% in the 0-10 cm layer-values which were only 25-40% of levels in untilled soil. Grazed grass leys were only partly successful in restoration of soil organic carbon status.
In the lower montane region of northwestern Ecuador, forest clearing for sugar cane and pasture production occurs simultaneously with recolonization of secondary forest vegetation on abandoned agricultural lands. We estimated the loss of forest-derived soil C (light in 13C) and the accumulation of C from replicate sugar cane and pasture vegetation (heavy in 13C) using a stable C isotope technique. We also measured differences in the proportion of soil C derived from C3 and C4 plants across a land-use progression from agricultural fields through successional communities and undisturbed forest. Total soil C was 23 Mg/ha lower in the upper 30 cm following 50 yr of sugar cane production (24% decrease) compared to old-growth forest. The net change (-0.4 Mg·ha-1·yr-1) in soil C consisted of 1.3 Mg/ha annual losses of original forest C and 0.9 Mg/ha annual gains of C from sugar cane. After 15 yr beneath pasture, soil C was 11 Mg/ha less in the upper 30 cm than beneath forest (12% decrease). During that period, 33% of the original forest C was lost, compared to 68% released during 50 yr of sugar cane cultivation. Rate of forest C loss, C4-C accumulation, and net soil C change differed little between two distinct pasture types. Setaria sphacelata pasture and a traditional mixed-species pasture both contained more total soil C and added C4-C more rapidly than sugar cane. Under second-growth forest, soil C increased by 1.9 Mg·ha-1·yr-1, the result of a 3 Mg/ha annual increase in C3 carbon and a 1.1 Mg/ha annual loss of C4 carbon. The total soil C pool returned to preclearing levels within 20 yr. While widespread reforestation may be thwarted by high demands for land in northwestern Ecuador, agricultural land-use options exist that can contribute to increased soil C stocks.
In a comparative study, the quantity of accumulated organic matter in, and the nutrient composition of the forest floor and topsoil (0–20 cm) of indigenous (beech or podocarp) forests and nearby Pinus radiata plantations in five widely separated forest sites in the South Island of New Zealand were measured. Total mass of forest floors in native and radiata plantation stands ranged from 25 to 464 and 9 to 79 t/ha, respectively. Native forest stands apparently accumulated larger amounts than nearby radiata pine stands, especially in the West Coast forests. In exotic plantations, the nett accumulation was modified by management practices such as burning, during the process of converting native forests to pine plantations, and stand thinning.Except in Nelson forests, forest floors in native stands had larger contents of carbon and nutrients than those of nearby radiata pine sites. No consistent differences were found in carbon and nutrient concentrations in topsoils of native and exotic forests except in the 9-year-old radiata pine stand in the Hochstetter forest, where they were lower than those under the native forest. However, levels of exchangeable cations and Bray-P in top-soils under radiata pine stands were higher than those of native stands. Concentrations of ether-extractable components (lipids), water-soluble carbohydrates and polyphenols in the forest floors under native forest were generally higher than those under radiata pine stands. Consistent differences between concentrations of lipid components and polyphenols in the topsoil under native and exotic forest were not found.
Tree root activity, including fine-root production, turnover and metabolic activity are significant components of forest productivity
and nutrient cycling. Differences in root activity among forest types are not well known. A 3-year study was undertaken in
red pine (Pinus resinosa Ait.) and hybrid poplar (Populus tristis X P. balsamifera cv `Tristis no. 1') plantations to compare belowground root dynamics. We measured fine-root production, mortality and standing
crop, as well as soil CO2 efflux. Pine fine-root production was only 2.9% of that of poplar during three years; 85 pine roots were observed in minirhizotron
tubes compared with 4088 poplar roots. Live-root density oscillated seasonally for both species with late winter minimum and
autumn maximum. Poplar reached constant maximum live-root length within the first growing season, but pine continued to increase
observed fine-root length for three growing seasons. Within the first 100 days following initial appearance, 22% of the pine
roots disappeared and 38% of the poplar roots disappeared. Median fine-root longevity of pine was 291 days compared with 149
days for poplar roots. Fine-root longevity increased with depth in the soil, and was greater for roots with initial diameter
>0.5 mm. The probability of poplar root death from late February to May was more than three times that in any other season,
regardless of root age. Despite the greater poplar root production and live-root length, fine-root biomass and soil CO2 efflux was greater in pine. Greater metabolic activity in the pine stand may be due to greater fine-root biomass or greater
heterotrophic respiration.
Cultivation has substantially reduced the organic matter contents of many prairie soils. This study attempts to quantify the losses of C, N, and P from three prairie soils of different textures during cultivation. For this purpose cultivated and adjacent uncultivated soils (2 Cryoborolls and 1 Cryorthent) were sampled and their C, N, and P contents as well as their bulk densities and horizon depths were compared.
Reductions of about 35% in the C concentration were observed in clay and silt loam soils after 60 to 70 years of cultivation. At the same time reductions in N concentrations were greatly influenced by the presence or absence of legume [alfalfa, ( Medicago sativa L.)] crops grown in the fields and losses varied between 18 and 34%. Phosphorus concentrations were reduced by 12% and all P losses were accounted for by the organic fraction. During a similar period of cultivation a lighter textured sandy loam had experienced greater reductions in C, N, and P concentrations of 46, 46, and 29%, respectively. In this soil P was lost from both the organic and inorganic fractions. Prolonged cultivation of 90 years did not result in a decrease in the rates of losses of C, N, and P on the silt loam soil.
Conversion of concentration data to area based total C, N, and P budgets resulted in a decrease in the differences seen between cultivated and uncultivated soils. This was caused by an increase of soil bulk densities under cultivation and by an increase in the standard deviations of the data due to variability of horizon depths in cultivated fields.
Tropical soils contain large stocks of carbon and nitrogen that can be altered by clearing for agriculture. In the Brazilian Amazon, cattle pasture is the predominant use for cleared forest lands. We examined changes to soil bulk density and C and N stocks in seven chronosequences, each consisting of an intact forest and pastures of different ages created directly from cleared forest (7 forests, 18 pastures), along a 700-km transect in Rondônia in the southwestern Amazon Basin. The transect included sites with a similar climate but a range of soil types. We used soil δ13C distributions to determine the origin of soil C and to infer changes to soil C cycling patterns after forest clearing. Soil bulk density increased under pasture; these increases were significant in 6 of 18 pastures examined. Changes in C stocks to a depth of 30 cm under pasture ranged from a loss of 0.72 kg/m2 to an increase of 1.77 kg/m2. Soil C stocks increased in 14 of 18 pastures, but these increases were significant in only 4 pastures. Changes in soil N stocks to a depth of 30 cm ranged from a loss of 0.25 kg/m2 to a gain of 0.23 kg/m2 and showed a similar pattern to C, except in one site where we measured significant N loss. Five of 18 pastures accumulated significant amounts of N, and one pasture lost a significant amount of N. Soil δ13C values were greater in pastures than in the original forests, and δ13C values increased with a longer time under C4 pasture vegetation. Bulk density increases were greater on soils with higher clay contents. Carbon accumulation increased with pasture age but was independent of soil texture. Soil C increases to a depth of 30 cm of up to 1.77 kg/m2 amounted to an increase of >50% of the original soil C stock and represented up to 12% of the C in the biomass of forest vegetation. In contrast, changes to soil N stocks in the range of 0.25 kg/m2 approximately equaled the N stock in the original forest vegetation. Our results indicated that when site history was controlled by considering only pastures formed directly from cleared forest, C and N accumulation was the dominant trend in pasture soils. Absence of a correlation between C and N accumulation and soil texture suggested that site history and management may be more important than soil type as determinants of the direction and magnitude of changes in soil C and N stocks.
Afforestation in the tropics may sequester soil C and has been proposed as a management tool to aid in controlling rising levels of atmospheric CO2. We measured changes in soil C following afforestation of sugarcane fields with fast-growing Eucalyptus saligna (Sm.) plantations in Hawaii. Using stable C isotopes, we estimated the contributions to changes in total soil C that were due to the loss of C from the prior cane cultivation, and to the gain of C from the new Eucalyptus plantations. Total soil C 10-13 yr after afforestation was 114 and 113 Mg/ha, respectively, in the Eucalyptus and cane plantation. Eucalyptus increased total soil C in the 0-10 cm layer by 11.5 Mg/ha, but that was offset by a loss of 10.1 Mg/ha of cane-derived C from the 10-55 cm layer. The net effect on soil C of afforestation of cultivated lands depends not only on new C gained, but also on C lost from the previous management.
Properties of topsoils collected from beneath a 10‐year‐old Pinus radiata stand were compared with those of soil collected from beneath adjacent unplanted Chionochloa rigida grassland, at a paired catchment study site in the Lammerlaw Range, Otago, South Island, New Zealand. In late summer, the soil moisture content was lower in the planted catchment than in the unplanted grassland, and the air‐filled porosity of the poorly drained Waipori silt loam soil was greater in the planted catchment. Soil bulk density and total porosity were similar in the two catchments. Soil pH and concentrations of total and organic phosphorus (P) and extractable cations were lower in the planted catchment, whereas levels of mineral and mineralisable nitrogen (N) and sulphate‐sulphur (SO4‐S) were higher in the planted catchment. Inorganic and Bray‐2 extractable P levels were similar in the two catchments. Physical and chemical properties of soils collected from beneath tree crowns (0.5 m from the tree base) in the planted catchment were similar to those collected from between tree rows (1.75 m from the tree base). The differences in chemical properties observed between catchments are attributed to increased nutrient uptake by the young pines, and to increased mineralisation of soil organic matter, which may have been promoted by improved soil aeration under the pines. S concentrations in the foliage of tussocks persisting between tree rows in the planted catchment were 3 times those in the unplanted catchment, whereas concentrations of N, P, and Mg were almost double, indicating that the availability of these nutrients to tussocks was substantially higher in the planted catchment.
At 31 sites of solodized solonetz and solodic soil in central Queensland, the total soil nitrogen (N) and organic carbon (OC) levels of pasture and crop areas were compared with matched uncleared areas of A. harpophylla-Dawson gum (Eucalyptus cambageana) forests. Reductions in total N content (kg per ha) occurred only at 8 of the 31 sites and ranged from 16-34% of the virgin levels (about 300 to 700 kg N ha−1). There was no association between changes in N reserves and age of development. Reductions in the concentration (%) of N and OC were measured under pasture (group 1) and crop (group 3) areas but not where pasture areas had been ploughed (group 2). The bulk density of soils developed to pasture was higher than those of the uncleared areas. In a pot experiment, both nitrogen uptake and dry matter (DM) yield were significantly (P< 0.01) correlated (r = 0.78, r = 0.81, respectively) with the percentage N content of soils. Also, reductions in potential DM yield were positively correlated (r = 0.76) with reductions in the N percentage. Old buffel grass (Cenchrus ciliaris) pastures were moderately deficient in nitrogen, and DM yield increased curvilinearly in response to nitrogen applied as NH4NO3 at rates of 0, 40, 80, 120, 160, 200, 240 and 300 kg N ha−1Current pasture production is about 60% below the potential possible if adequate nitrogen is available. Summer yields of 3200 kg DM ha-l were doubled, with a response efficiency of about 31 kg DM per kg N, by applying 120 kg N ha−1The pasture potential of sites of differing N status was influenced by the weather. It is concluded that the deterioration of pastures on brigalow lands is influenced more by reduced nitrogen availability than changes in N reserves.
Soil acidification and related land degradation issues are assuming increasing importance in Australia and challenging the concept of sustainability of current land management systems. In this study, the impacts of tree plantations of 2 species and permanent pasture on soil chemical properties are compared. Soil samples were collected from the top 50 cm (0-5, 5-10, 10-15, 15-20, 20-30, and 30-50 cm depths) from 3 adjacent sites carrying pasture and monocultures of Pinus radiata (radiata pine) and Quercus suber (cork oak) on a deep-surfaced yellow podzolic soil, and differences in soil pH and other soil chemical properties were examined. In the surface 0-5 cm, pH was similar at all 3 sites. Below that depth, soil pH was significantly lower and exchangeable Al greater under the cork oak stand than at the other 2 sites. Consistent with a decrease in soil pH there was significantly less exchangeable Ca under cork oak. Also, less clay was observed under the cork oak stand and this is taken as evidence of the degradational impact of soil acidification. An estimate of Ca in the top 50 cm of the soil implies considerable loss of Ca under oak, probably by leaching and loss of litter down the slope. Evidence is presented to show that there has been more Fe and Al movement under oak than under pasture and pine, this being ascribed in part to the greater Al and Fe mobilising capacity of the water-soluble component extracted from freshly fallen leaf litter of oak. The Fe and Al composition of the oxalate extract from concretionary material at 10-30 cm under oak is consistent with a process similar to podzolisation. Pseudogleying of Fe and Al may have accompanied the leaching of bases from the system and a reduction of pH.
Comparisons of soil samples from virgin sites or sites recently planted to sugarcane (new) with sites that had been under cane production for many years (old) were made to investigate the potential impact of cane production on soil organic carbon (OC) levels and chemistry. The comparisons showed that very little change had occurred in total OC and in `light' fraction (<1.6 Mg/m(3)). Increasing pyrophosphate extractability throughout the profile at some sites, as a result of cultivation, however, suggested that the organic matter generally became more `humified' with long-term cane production. Evidence is presented for a redistribution of OC within profiles under cane production. Old, well-established cane sites had soils with lower OC levels in the surface horizons and higher levels in the subsoils relative to new sites. The overall chemistry of the soil organic matter, as indicated by solid state C-13 nuclear magnetic resonance spectroscopy, did not change significantly at each site even though between site differences were large. Some soils contained substantial amounts of charcoal which was of pre-cane origin. In some of the coarse-textured soils, smaller amounts of charcoal produced during the burning of cane appeared to accumulate below the A1 horizons in the profiles. It also appeared likely that the redistribution of carbon in the upper horizons of some soils resulted from the movement of charcoal within the profile, probably as a result of tillage.
The soil survey was conducted on cropped and uncropped Red Earths (Alfisols), Grey Clays, and Black Earths (Vertisols) in northern New South Wales. The degradation of soil physical properties between the cropped and uncropped reference sites was reflected in declines of 29-86% in hydraulic conductivity (K) and 33-71% in aggregation. Generally there was a substantial loss of carbon with cropping, and the loss of labile carbon (C(L)) was usually greater than the loss of total carbon (C(T)). A Grey Clay which had been cropped for >40 years had lost 63% and 51% of its C(L) and C(T), respectively. An adjacent Grey Clay which had been cleared and cropped for only 2 years had lost 43% and 26% of its C(L) and C(T), respectively, resulting in a C management index (CMI) of 55, indicating that a large proportion of soil C was lost soon after the commencement of cropping. Where well-managed legume leys had recently been grown, the loss of C was reduced, resulting in a higher CMI. A loss of total and available nutrients after cropping was also found, with the magnitude of the losses modified by fertiliser history. A highly significant correlation was found between C(T) or C(L) and the proportion of water-stable aggregates >250 μm for the Red Earth and Grey Clay soils, but this correlation was