Conversion Of Natural Forest Research Articles

Assessing the Effects of Land-Use and Land Cover Change and Topography on Soil Fertility in Melka Wakena Catchment of Sub-Upper Wabe-Shebelle Watershed, South Eastern Ethiopia

This study was conducted in Melka Wakena catchment; south eastern Ethiopia to assess land use/cover change (LULCC) and topographic elevation effect on selected soil quality/fertility parameters. 144 soil samples collected from 0 - 30 cm depth under three land cover types across three elevation gradients were analysed for selected soil quality/fertility parameters. Data were statistically analyzed using analysis of variance (ANOVA) and mean comparisons were made using Least Significant Difference (LSD). The soil properties examined generally showed significant variations with respect to land-use/land cover changes and elevation. Soil particles, soil organic carbon, total N, pH, available phosphorus, potassium and calcium content significantly decreased as forestland is converted into cropland/grassland. Heaviest soil deterioration was recorded in soils under cropland and followed by grassland soils. The conversion of natural forest to different land uses without proper soil conservation and management practices resulted in the overall decline of soil fertility quality. Thus, integrated land resource management approach is indispensable for sustaining agricultural productivity and the environmental health of the Melka Waken a catchment.

基于土地利用变化的热带植物群落功能性状与土壤质量的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 基于土地利用变化的热带植物群落功能性状与土壤质量的关系 DOI: 10.5846/stxb201703290541 作者: 作者单位: 中国科学院生态环境研究中心,中国科学院生态环境研究中心,海南鹦哥岭国家级自然保护区管理站,中国科学院城市环境研究所,中国科学院生态环境研究中心,中国科学院生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0503401）；国家自然科学基金项目（41871217） Relationships between plant community functional traits and soil quality based on land use changes in tropical region Author: Affiliation: Research Center for Eco⁃Environmental Sciences，Chinese Academy of Sciences,Research Center for Eco⁃Environmental Sciences，Chinese Academy of Sciences,Hainan Yinggeling National Nature Reserve,nstitute of Urban Environment，Chinese Academy of Sciences,Research Center for Eco⁃Environmental Sciences，Chinese Academy of Sciences,Research Center for Eco⁃Environmental Sciences，Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了明确热带天然林转变为橡胶林和槟榔后土壤质量变化，揭示土地利用变化下植物群落功能性状对土壤质量影响。在海南中部山区，以原始林（PF）、次生林（SF）、槟榔（Areca catechu）林（AP）、纯橡胶（Hevea brasiliensis）林（RP）和橡胶益智（Alpinia oxyphylla）林（RAP）为对象，探索天然林退化后土壤性质和质量变化，分析了植物群落功能性状（凋落物量、郁闭度、根长密度、细根密度和比根长）对土壤质量影响。结果表明：1）与原始林相比，其他土地利用类型凋落物量、根长密度、细根密度、土壤总孔隙度、最大持水量、土壤有机碳和总氮显著降低，土壤容重显著增加。人工林土壤碱解氮明显降低，但总磷、总钾和缓效钾明显升高（P < 0.05）。2）与原始林相比，次生林、槟榔林、纯橡胶林和橡胶益智林土壤质量指数分别降低63.4%、85.8%、81.2%和84.1%，随原始林、次生林和人工林梯度土地利用强度的增加，土壤质量显著降低（P < 0.05），但人工林间土壤质量无显著差异。3）凋落物量、郁闭度、根长密度和细根密度均与土壤质量指数显著正相关（P < 0.05），细根密度对土壤质量的直接影响效应最大，凋落物间接影响效应最大。天然林转变为橡胶和槟榔林显著改变土壤性质和质量，群落性状细根密度和凋落物可较好解释土壤质量变化，强化人工林林下植被和凋落物管理有利于土壤质量改善。 Abstract:To reveal the effects of plant community functional trait changes, resulted from the land use conversion from primitive forest to secondary forest or plantations, on soil quality in tropical region, an investigation was conducted in five typical land use types in the central mountainous area of Hainan Island. The land use types include primitive forest (PF), secondary forest (SF), areca plantation (AP), pure rubber plantation(RP) and rubber intercropping Alpinia oxyphylla plantation (RAP).The changes of soil qualities after the natural forest conversion to secondary forest or plantations and the relationships between plant community functional traits (litter fall, canopy density, root length density, fine root density, and specific root length) and soil quality were analyzed. Compared with those of primitive forest, the litter fall, root length density, fine root density, total soil porosity, maximum water holding capacity, soil organic carbon, and total nitrogen of other land use types decreased significantly (P < 0.05), but soil bulk density increased significantly(P < 0.05). Soil alkaline hydrolysis of nitrogen in all plantations decreased obviously, whereas soil total phosphorus, soil total potassium, and slowly available potassium increased significantly(P < 0.05) during the conversion. With increasing of land use intensity, the soil quality decreased significantly(P < 0.05). The soil quality indexes of SF, AP, RP, and RAP decreased by 63.4%, 85.8%, 81.2% and 84.1%, respectively, compared with that of PF. However, there were no differences in soil quality among the plantations. The litter fall, canopy density, root length density, and fine root density had the positive and significantly correlations with the soil quality index(P < 0.05). Moreover, fine root density had the largest direct effect on soil quality, and litter had the largest indirect effect. Our results suggested that the transformation of tropical primitive forests to rubber and areca plantations significantly changed soil properties and soil quality, which was mainly explained by the plan community functional traits of fine root density and litter fall. Improving the management of litter fall and understory plant community, which influences fine root density, will help increase soil quality in plantations in tropical region. 参考文献 相似文献 引证文献

Temporal changes in fertility and microbial properties of soil in forest-converted oil palm plantations in Okomu forest reserve, Nigeria

ABSTRACTEvidence of the impacts of land-use change on soil biological activities, a determinant of nutrient cycling in soil, will provide a better understanding of soil health and productivity. The study investigates temporal changes in soil chemical and microbial properties in a forest converted to oil palm plantation. Soil samples from four locations: native forest and Elaeis guineensis plantations of 2-, 13- and 14-year were collected. Total carbon C and N were significantly higher (p < 0.05) in the native forest (NF) followed by 14- and 13-year E. guineensis plantations respectively. Microbial biomass carbon (MBC) and nitrogen (MBN) in NF were significantly higher (p < 0.05) than in the E. guineensis plantations. There were no significant differences in the microbial biomass phosphorus (MBP) among the E. guineensis plantation of all ages. The qCO2 in the 13- and 14-year E. guineensis plantations was higher than in NF and 2-year E. guineensis plantation. There was a positive correlation between MBC, MBN, MBP and pH, P, TC, and TN. These results indicated that conversion of native forest to E. guineensis plantation affected soil nutrient and microbial properties. And there could be a return to healthy soil condition as age of E. guineensis plantation increased.

Aggregation, carbon, and total soil nitrogen in crop-livestock-forest integration in the Eastern Amazon

ABSTRACT Sustainable agricultural production systems can improve physical attributes of soil as well as increase carbon and nitrogen stocks in soils. The objective of this study was to evaluate changes in the stability of soil aggregates and contents and stocks of carbon and nitrogen after the conversion of native forest to crop-livestock-forest integration systems in the region of Western Pará. Soil samples from five management systems (including a control) were collected at three depths in a randomized block design, with five replications. The stability of the aggregates, soil density, particle density, and total soil porosity, as well as total carbon and nitrogen and their respective stocks were evaluated. The native forest had the highest percentages of macroaggregates, followed by the integration system with African mahogany. At a depth of 0-0.10 m, the contents and stocks of carbon were higher in the agricultural area and in the integration system with cumaru, whereas nitrogen contents and stocks were higher in the native forest, followed by the integration systems with mahogany and cumaru. Compared to the other systems, the pasture area stored more carbon at depths of 0-0.10 and 0.10-0.20 m.

Soil moisture integrates the influence of land-use and season on soil microbial community composition in the Ethiopian highlands

Conversion of old-growth natural forest to crop land or grazing land and then to eucalyptus plantation is prevalent under the present socio-economic conditions in Ethiopia. To investigate the soil microbial and soil biochemical properties among the different land-use types in the highlands of the Northeastern Ethiopia, we measured soil microbial biomass and the potential activities of six extracellular enzymes. The soil microbial biomass was higher in natural forest than in plantation and grazing land, which was explained by the higher soil C concentrations. The microbial C:N ratio was higher in the dry (C:N 11–19) than in the wet season (C:N 5–10), indicating more fungal biomass in the dry season. The strong positive correlation between the microbial C:N ratio and chitinase activity supports the interpretation that the microbial C:N ratio reflects the dominance between fungi and bacteria in soil. The C:N ratio was negatively correlated with soil moisture within and between seasons, indicating that soil moisture considerably influenced the microbial community. Our study demonstrated that land-use affects soil microbial properties and enzyme activity. Nonetheless, the increase in the microbial C:N ratio after land-use change is driven mainly by soil moisture (which is influenced by land use) rather than by changes in vegetation or soil properties.

Soil Organic Carbon Depletion from Forests to Grasslands Conversion in Mexico: A Review

Land use change from forests to grazing lands is one of the important sources of greenhouse gas emissions in many parts of the tropics. The objective of this study was to analyze the extent of soil organic carbon (SOC) loss from the conversion of native forests to pasturelands in Mexico. We analyzed 66 sets of published research data with simultaneous measurements of soil organic carbon stocks between native forests and pasturelands in Mexico. We used a generalized linear mixed effect model to evaluate the effect of land use change (forest versus pasture), soil depth, and original native forest types. The model showed that there was a significant reduction in SOC stocks due to the conversion of native forests to pasturelands. The median loss of SOC ranged from 31.6% to 52.0% depending upon the soil depth. The highest loss was observed in tropical mangrove forests followed by highland tropical forests and humid tropical forests. Higher loss was detected in upper soil horizon (0–30 cm) compared to deeper horizons. The emissions of CO2 from SOC loss ranged from 46.7 to 165.5 Mg CO2 eq. ha−1 depending upon the type of original native forests. In this paper, we also discuss the effect that agroforestry practices such as silvopastoral arrangements and other management practices like rotational grazing, soil erosion control, and soil nutrient management can have in enhancing SOC stocks in tropical grasslands. The results on the degree of carbon loss can have strong implications in adopting appropriate management decisions that recover or retain carbon stocks in biomass and soils of tropical livestock production systems.

Simulated leaf litter addition causes opposite priming effects on natural forest and plantation soils

The conversion of natural forests to tree plantations alters the quality and decreases the quantity of litter inputs into the soil, but how the alteration of litter inputs affect soil organic matter (SOM) decomposition remain unclear. We examined SOM decomposition by adding 13C-labeled leaf-litter of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) to soils from a natural evergreen broad-leaved forest and an adjacent Chinese fir plantation converted from a natural evergreen broad-leaved forest 42 years ago. Over 195 days, we monitored CO2 efflux and its δ13C, microbial biomass, and the composition of microbial groups by phospholipid fatty acids (PLFAs). To distinguish priming mechanisms, partitioning of C sources in CO2 and microbial biomass was determined based on δ13C. Leaf-litter addition to natural forest increased microbial biomass and induced up to 14% faster SOM decomposition (positive priming) than that in soil without litter. In contrast, negative priming in soils under plantation indicated preferential use of added leaf-litter rather than recalcitrant SOM. This preferential use of leaf-litter was supported by an increased fungal to bacterial ratio and litter-derived (13C) microbial biomass, reflecting increased substrate recalcitrance, the respective changes in microbial substrate utilization and increased C use efficiency. The magnitude and direction of priming effects depend on microbial preferential utilization of new litter or SOM. Concluding, the impact of coniferous leaf-litter inputs on the SOM priming is divergent in natural evergreen broad-leaved forests and plantations, an important consideration in understanding long-term C dynamics and cycling in natural and plantation forest ecosystems.

Assessment of hydrological pathways in East African montane catchments under different land use

Abstract. Conversion of natural forest (NF) to other land uses could lead to significant changes in catchment hydrology, but the nature of these changes has been insufficiently investigated in tropical montane catchments, especially in Africa. To address this knowledge gap, we aimed to identify stream water (RV) sources and flow paths in three tropical montane sub-catchments (27–36 km2) with different land use (natural forest, NF; smallholder agriculture, SHA; and commercial tea and tree plantations, TTP) within a 1021 km2 catchment in the Mau Forest complex, Kenya. Weekly samples were collected from stream water, precipitation (PC) and mobile soil water for 75 weeks and analysed for stable isotopes of water (δ2H and δ18O) for mean transit time (MTT) estimation with two lumped parameter models (gamma model, GM; and exponential piston flow model, EPM) and for the calculation of the young water fraction. Weekly samples from stream water and potential endmembers were collected over a period of 55 weeks and analysed for Li, Na, Mg, K, Rb, Sr and Ba for endmember mixing analysis (EMMA). Solute concentrations in precipitation were lower than in stream water in all catchments (p &lt; 0.05), whereas concentrations in springs, shallow wells and wetlands were generally more similar to stream water. The stream water isotope signal was considerably damped compared to the isotope signal in precipitation. Mean transit time analysis suggested long transit times for stream water (up to 4 years) in the three sub-catchments, but model efficiencies were very low. The young water fraction ranged from 13 % in the smallholder agriculture sub-catchment to 15 % in the tea plantation sub-catchment. Mean transit times of mobile soil water ranged from 3.2–3.3 weeks in forest soils and 4.5–7.9 weeks in pasture soils at 15 cm depth to 10.4–10.8 weeks in pasture soils at 50 cm depth. The contribution of springs and wetlands to stream discharge increased from a median of 16.5 (95 % confidence interval: 11.3–22.9), 2.1 (−3.0–24.2) and 50.2 (30.5–65.5) % during low flow to 20.7 (15.2–34.7), 53.0 (23.0–91.3) and 69.4 (43.0–123.9) % during high flow in the natural forest, smallholder agriculture and tea plantation sub-catchments, respectively. Our results indicate that groundwater is an important component of stream water, irrespective of land use. The results further suggest that the selected transit time models and tracers might not be appropriate in tropical catchments with highly damped stream water isotope signatures. A more in-depth investigation of the discharge dependence of the young water fraction and transit time estimation using other tracers, such as tritium, could therefore shed more light on potential land use effects on the hydrological behaviour of tropical montane catchments.

Land use changes: a key ecological driver regulating methanotrophs abundance in upland soils

Land use changes have been recognized as one of the key ecological drivers in regulation of methane (CH4) consumption from dry upland soils. This study investigated the impact of land use changes and different soil depths (0–10, 10–20 and 20–30 cm) on soil physicochemical properties and methanotrophs abundance in dry tropical region of Vindhyan uplands. Four different land use types (agriculture land, mixed forest, savanna and natural forest) were selected for a comparative study. Among the different land uses and soil depths, results indicated significantly higher soil moisture (SM), organic-C, inorganic nutrients, water holding capacity (WHC) and methanotrophs abundance at 0–10 cm depth of natural forest compared to other sites. Across different land uses, number (8.11 × 107 pmoA copies g−1 of dry soil) of methanotrophs isolated from the natural forest soil was statistically higher than the soils of other land use types. The variations in pmoA gene numbers across different land uses and soil depths were significant (P mixed forest > savanna > agriculture land. The result suggest that land use changes (conversion of natural forest to agricultural land) alter the major soil properties (SM, WHC, organic matter, C/N ratio, etc.) and significantly reduce the methanotrophs and pmoA gene numbers. The land use management practices (application of bio-fertilizers in place of chemical fertilizers), especially for the degraded agricultural soils, could be beneficial option to mitigate the negative impacts on soil methanotrophs and their CH4 sink activity in the upland soil of Vindhyan region.

Effects of land-use change on Nitisols properties in a tropical climate

El cambio en el uso de la tierra, especialmente la conversión de bosques nativos en tierras cultivadas ejerce un impacto sobre las propiedades físicas, químicas e hidrofísicas de los suelos. El objetivo de este estudio fue evaluar la influencia de diferentes sistemas de manejo de un suelo tropical reflejado en algunas de sus propiedades físicas, químicas e hidrofísicas. Se evaluaron nueve perfiles de un suelo Nitisol agrupado en tres categorías: (I) bosque nativo (Referencia &gt; 30 años); (II) suelos anteriormente cultivados y luego convertidos en pastizales (Conservados &gt; 10 años); y (III) suelos bajo cultivo continuado (Agrogénicos &gt; 50 años). Las variables analizadas fueron materia orgánica, densidad aparente, densidad real, porosidad, capacidad de campo, textura e índice estructural. Los resultados determinaron que la acción de las técnicas agrícolas tradicionales en ambientes tropicales produce una excesiva degradación de las propiedades del suelo. El contenido de materia orgánica e índice estructural muestran una relación lineal con un alto grado de dependencia (R2=0,99). La densidad aparente promedio para los perfiles (I) y (II) fue menor (P&lt;0,05) que los valores de densidad aparente del perfil (III). En los análisis de regresión a medida que aumenta la densidad aparente disminuye la capacidad de campo y la tendencia observada para (I) y (II) es lineal, mientras que para (III) es polinómica con (R2=0,83), pudiendo estar influenciado por los valores más altos de la densidad aparente, mayor compactación, menor índice estructural, materia orgánica y porosidad en correspondencia con los otros perfiles.

Indonesia's Moratorium on Palm Oil Expansion from Natural Forests: Economy-Wide Impacts and the Role of International Transfers

Indonesia has introduced a moratorium on the conversion of natural forests to land used for palm oil production. Using a dynamic, bottom-up, interregional computable general equilibrium model of the Indonesian economy, we assess several scenarios of the moratorium and discuss its impacts on the domestic economy as well as on regional economies within Indonesia. We find the moratorium reduces Indonesian economic growth and other macroeconomic indicators, but international transfers can more than compensate the welfare losses. The impacts also vary across regions. Sumatra, which is highly dependent on palm oil and is home to forests that no longer have a high carbon stock, receives fewer transfers and suffers the greatest economic loss. Kalimantan, which is relatively less dependent on palm oil and has forests with a relatively high carbon stock, receives more transfers and gets greater benefit. This implies that additional policy measures anticipating the unbalanced impacts of the moratorium are required if the trade-off between conservation and reducing interregional economic disparity is to be reconciled.

Plant-Soil Properties Associated with Nitrogen Mineralization: Effect of Conversion of Natural Secondary Forests to Larch Plantations in a Headwater Catchment in Northeast China

To understand the relative importance of plant community composition and plant-induced soil properties on N transformations, the soil N mineralization, ammonification and nitrification characteristics of natural secondary forests (Quercus mongolica-Juglans mandshurica forest: QJF, and Quercus mongolica-Populus davidiana forest: QPF) and the adjacent larch plantations (Larix kaempferi forest: LF1 and LF2) were studied during the growing season. All of the forest types showed seasonal dynamics of N mineralization rates. The total cumulative N mineralization was significantly higher in QPF (73.51 kg hm−2) than in LF1 (65.64 kg hm−2) and LF2 (67.51 kg hm−2) (p &lt; 0.05). The total cumulative nitrification from May to November was significantly higher in QJF (65.16 kg hm−2) and QPF (64.87 kg hm−2) than in LF1 (52.62 kg hm−2) and FL2 (54.17 kg hm−2) (p &lt; 0.05). Based on the variation partitioning, independent soil properties were the primary determinants of the N transformations (13.5%). Independent climate conditions explained 5.6% of the variations, while plant variations explained 3.2% of the variations in N transformations. We concluded that different forest types with various plant community compositions have different influences on the litterfall quantity and quality and the nutrient availability, and these differences interact with seasonal climate conditions that in turn drive the differences in N mineralization.

Plant diversity of Betel Leaf Agroforestry of South Meghalaya, Northeast India

Tynsong H, Tiwari BK, Dkhar M. 2018. Plant diversity of Betel Leaf Agroforestry of South Meghalaya, Northeast India. Asian J For 2: 1-11. Large areas of lowland tropical forests of South Meghalaya have been converted into betel leaf agroforestry systems by the tribal people living in the area. The betel leaf agroforestry with diverse and structurally complex shade canopies conserve a significant portion of the original forest biodiversity. The impact of land use change on the biodiversity was studied using standard vegetation analysis and biodiversity estimation methods. A total of 160 plant species were recorded in natural forests out of which 75 were trees, 40 shrubs, and 45 herbs, while in betel leaf agroforestry, a total of 159 plant species, 94 trees, 17 shrubs and 48 herbs were recorded. A total of 34 tree species, 13 shrub species, and 14 herb species were common in both the land uses. All the plant species were native species. The study revealed that the conversion of natural forest to betel leaf agroforestry in South Meghalaya has no significant impact on tree and herb diversity. However, the basal area and density are affected to some extent. The land use change has also affected the density and diversity of shrubs. The study concludes that betel leaf agroforestry in South Meghalaya developed by the indigenous War Khasi tribe through experiential learning over several generations has emerged as a fairly sustainable agroforestry system causing minimal impact on plant diversity.

Identification of indicators for evaluating and monitoring the effects of Chinese fir monoculture plantations on soil quality

Globally, forest conversion is known to affect soil quality. In the present study, we developed a soil quality index (SQI) to quantify the changes in soil quality due to conversion of native forests into Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in southern China. We selected 11 Chinese fir stands of different ages (12-, 21-, 40-, and 97-year-old in the first rotation; 1-, 12-, 21-, and 31-year-old stands in the second rotation; 13- and 21-year-old stands in the third rotation; and a 10-year-old stand in the fourth rotation) from sub-tropical forest plantations in Nanping, Fujian Province, China. Soil samples were collected from different depths (0–20, 20–40, 40–60, 60–80, and 80–100 cm) and 20 soil properties were analysed. SQI was computed from the minimum data set derived from principal component analysis (PCA). Although the PCA included many soil properties, we identified total phosphorus (TP) and labile carbon pool II (LP-II-C) as key soil quality indicators, because they contributed 36.2 and 34.9% to SQI, respectively, followed by labile nitrogen pool I (LP-I-N) and soil pH. SQI values showed that continuous replanting of Chinese fir at the same site decreased soil quality significantly at 0–100 cm depth. Increasing rotation cycle (from first to fourth) strongly reduced LP-II-C (48.8%), LP-I-N (56.6%), labile nitrogen-II (70.2%), nitrate-nitrogen (67.7%), and available phosphorus (48.4%), indicating that successive rotation degrades soil quality. Thus, our results demonstrate that Chinese fir cultivation should be limited to only two rotations in the same site to preserve soil quality. We conclude that TP, LP-II-C, LP-I-N, and pH can be used as effective indicators in temporal soil quality monitoring programs under forest plantations.

Tree plantations displacing native forests: The nature and drivers of apparent forest recovery on former croplands in Southwestern China from 2000 to 2015

China is credited with undertaking some of the world's most ambitious policies to protect and restore forests, which could serve as a role model for other countries. However, the actual environmental consequences of these policies are poorly known. Here, we combine remote-sensing analysis with household interviews to assess the nature and drivers of land-cover change in southwestern China between 2000–2015, after China's major forest protection and reforestation policies came into effect. We found that while the region's gross tree cover grew by 32%, this increase was entirely due to the conversion of croplands to tree plantations, particularly monocultures. Native forests, in turn, suffered a net loss of 6.6%. Thus, instead of truly recovering forested landscapes and generating concomitant environmental benefits, the region's apparent forest recovery has effectively displaced native forests, including those that could have naturally regenerated on land freed up from agriculture. The pursuit of profit from agricultural or forestry production along with governmental encouragement and mobilization for certain land uses – including tree planting – were the dominant drivers of the observed land-cover change. An additional driver was the desire of many households to conform with the land-use decisions of their neighbors. We also found that households' lack of labor or financial resources, rather than any policy safeguards, was the primary constraint on further conversion of native forests. We conclude that to achieve genuine forest recovery along with the resulting environmental benefits, China's policies must more strongly protect existing native forests and facilitate native forest restoration. Natural regeneration, which thus far has been grossly neglected in China's forest policies, should be recognized as a legitimate means of forest restoration. In addition, social factors operating at the household level, notably the pursuit of profit and conformation to social norms, should be harnessed to promote better land-cover, biodiversity, and environmental outcomes. More generally, for China and other countries to succeed in recovering forests, policies must clearly distinguish between native forests and tree plantations.

Efeito da conversão da vegetação nativa em áreas agrícolas sobre variáveis biofísicas na região de transição Cerrado-Amazônia

The objective of this work was to evaluate the effect of the conversion of native vegetation on agricultural areas based on Normalized Difference Vegetation Index (NDVI), surface albedo (α), brightness temperature (Tb) and net radiation (Rn) in Cerrado-Amazon transition area with Landsat images 8. The classes of land use studied were: Native forest (FN), Irrigated area (AI) and Not irrigated (AN) with agronomic crops in scenes 331 of 2015, 094 and 206 of 2016 of a farm in the North Center of the state of Mato Grosso. From the information obtained from the images together with the Automatic Smile Meteorological Station (EMA) - MT, was calculated the net radiation. The conversion of native forest to agricultural areas in the Cerrado-Amazon transition region exerts an increase in the surface albedo and the brightness temperature values and a decrease in the NDVI, consequently the reduction of the values of the net radiation. The mean values of NDVI, α, Tb and Rn found in the FN (0,86, 0,16, 24,44 °C and 598,80 W m²), AI (0,79, 0,22, 24,90 °C and 549,74 W m²) and AN (0,53; 0,28, 28,78 °C and 486,48 W m²) evidences the effect of the conversion of native vegetation in agricultural areas based on biophysical indices.

Collapse of ecosystem carbon stocks due to forest conversion to soybean plantations at the Amazon-Cerrado transition

Abstract Deforestation to establish monocrops in the tropics is causing massive reductions in ecosystem C stocks. Amazonia is a principal targets of this process, owing to the expansion of the agribusiness frontier throughout the transition with the Cerrado biome, the zone known as the “Arc of Deforestation”. In this vast contact region between the two largest South American biomes, the conversion of primary forest to soybean and pasture systems has led to the deforestation of nearly five million hectares since 1980. Despite this, we lack precise understanding of the effects of land use on ecosystem C stocks and pools in this region. Addressing this knowledge gap is crucial to improve predictions and fit models for different land use scenarios in Amazonia. To reduce uncertainty regarding the magnitude of the impacts of deforestation on the C cycle, we evaluated ecosystem C stocks in contrasting land-use systems across a topographically, climatically, and edaphically near-homogeneous landscape in southern Amazonia. We investigated the soil, litter, fine root and aboveground biomass (AGB) C stocks of soybean plantations and compared them to those of remnant native forests and rubber plantations; the latter is considered a priori as a cropping system with low impact on the C cycle. We found that the conversion of native forest to soybean plantation caused a 130.5 Mg C ha−1 loss, about threefold higher than the loss when forest is converted to rubber plantations, 48.5 Mg C ha−1. While 30-year old rubber plantations had recovered 84% of forest carbon stocks, all plantation types induced sustained losses of at least one-third of the original soil carbon. Fine root allocation changed sharply in the two crops following conversion, indicating an alteration in plant nutrient dynamics. Our results show that perennial and annual monocrops have very different impacts on the C cycle, which need to be accounted for in carbon-climate models as well as in public policies regulating land use in Amazonia. Our results show that while silviculture has the potential to restore most of the above-ground C stocks of previously forested areas, but neither silviculture nor conventional agriculture may ever restore Amazon soil C stocks once they become vulnerable and oxidized after deforestation. If such conversion-driven soil carbon losses were scaled across the Amazon they would induce a cumulative loss of more than 5 Pg in soil carbon by 2050.

Effects of land use change on soil physicochemical properties in selected areas in the North West region of Cameroon

BackgroundLand use changes from natural ecosystems into managed ecosystems may have deleterious effects on soil structure and quality. This study characterise the soils under, and assesses the effects of different land use systems on selected soil physicochemical properties in the North West region of Cameroon. Six land use systems including: natural forest, natural savanna, grazing land, afforested land, farmland and Eucalyptus plantation were identified. Ninety soil samples were collected from each at the 0–15 cm depth. Fifteen soil physicochemical properties were measured.ResultsThe conversion of natural forest or savanna to farmland reduces the silt contents, moisture content, organic matter, organic carbon, total nitrogen, available phosphorus, pH, cation exchange capacity and exchangeable bases, but increases bulk density, electrical conductivity, exchangeable acidity and sand content significantly (P < 0.05). The results revealed that deforestation and subsequent cultivation of soil had negative effects on the measured soil properties.ConclusionsLand use change has ruined soil quality in the North West region. To reverse soil degradation and promote restoration, emphases should be placed on promoting the use of sustainable land management practices within the savanna, grazing, agricultural and forest management systems.

Anthropogenic disturbance of tropical forests threatens pollination services to açaí palm in the Amazon river delta

Abstract The açaí palm Euterpe oleracea Mart. in the Amazon river delta has seen rapid expansion to meet increased demand for its fruit. This has been achieved by transforming lowland forest habitats (floodplains) into simplified agroforests and intensive plantation in upland areas. As açaí palm makes an important contribution to the economy and food security of local communities, identifying management approaches that support biodiversity and ecosystem processes that underpin fruit production on açaí farms is essential. We compared flower‐visitor communities and açaí fruit production in floodplain forests and upland plantations, across gradients of local management intensity (i.e. açaí density per ha) and surrounding forest cover. The relative contribution of biotic pollination and degree of pollen limitation were assessed using insect exclusion and hand‐pollination experiments. We found that açaí flower visitors are highly diverse (c. 200 distinct taxa) and had variable responses to disturbance. Bee visitation was higher in floodplains and positively related to surrounding forest cover, but other flower visitors, including specialised curculionid beetles, were unresponsive to changes in surrounding forest cover. However, intensive management practices (i.e. high açaí palm densities) in floodplains and uplands had contrasting effects on flower‐visitor communities, with flower‐visitor richness being lower on intensively managed floodplain farms and ant densities being higher on intensive upland farms. Pollination experiments revealed açaí palm to be highly dependent on biotic pollination. Fruit set in open‐pollinated inflorescences was positively related to flower‐visitor richness and specialised curculionid beetle visitation, whereas the presence of ants on inflorescences had a negative effect. Synthesis and applications. Our study shows that pollinators are essential for açaí fruit production, but that intensive farming practices have eroded the relationship between surrounding forest cover and ecosystem function in floodplains (i.e. conversion of native forest into simplified agroforests) and increased the frequency of antagonistic interactions in uplands (e.g. high ant densities). These findings underline the value of extensive management practices, such as the maintenance of other tree species within farms and adjacent unmanaged forest patches, to ensure the long‐term sustainability of açaí fruit production in the Amazon river delta.

Soil Organic Carbon and Nitrogen Stocks Following Land Use Changes in a Sub-Humid Climate

There has been an incessant conversion of natural forests to agricultural land uses such as farmlands, grasslands and parkland agro-forestry in Africa during the last century. This study investigated changes in soil organic carbon (SOC) and total nitrogen (TN) stocks following the conversion of a natural forest to coffee-based agro-forestry, grazing grassland and well-managed maize farm in a sub-humid tropical climate of Ethiopia. Soil samples (up to 1m depth) were taken from each of these four land use types. Taking the natural forest as a baseline and with duration of 35 years since land use conversion, the total SOC and TN stocks were not significantly different (P &gt; 0.05) among the different land use types when the entire 1m soil depth was considered. However, in the upper 0-10cm soil depth, the SOC and TN stocks were significantly higher (P &lt; 0.05) in the natural forest than the agricultural land use types. There were different patterns of SOC and TN distributions along the soil depths for the different land use types. The SOC stocks decreased with depth in natural forest, but did not show any increasing or decreasing trends in maize farm, grazing grassland, and coffee-based agroforestry. The results of this study revealed that the negative effects of converting natural forests to agricultural land use types on SOC and TN can be prevented through appropriate land management practices in cultivated and grazing lands and use of proper agroforestry practices in a sub-humid tropical climate.