Cessation Of Cultivation Research Articles

Long‐term ecological legacies in western Amazonia

Abstract Modifications of Amazonian forests by pre‐Columbian peoples are thought to have left ecological legacies that have persisted to the modern day. Most Amazonian palaeoecological records do not, however, provide the required temporal resolution to document the nuanced changes of pre‐Columbian disturbance or post‐disturbance succession and recovery, making it difficult to detect any direct, or indirect, ecological legacies on tree species. Here, we investigate the fossil pollen, phytolith and charcoal history of Lake Kumpaka, Ecuador, during the last 2,415 years in c. 3–50 year time intervals to assess ecological legacies resulting from pre‐Columbian forest modification, disturbance, cultivation and fire usage. Two cycles of pre‐Columbian cultivation (one including slash‐and‐burn cultivation, the other including slash‐and‐mulch cultivation) were documented in the record around 2150–1430 cal. year BP and 1250–680 cal. year BP, with following post‐disturbance succession dynamics. Modern disturbance was documented after c. 10 cal. year BP. The modern disturbance produced a plant composition unlike those of the two past disturbances, as fire frequencies reached their peak in the 2,415‐year record. The disturbance periods varied in intensity and duration, while the overturn of taxa following a disturbance lasted for hundreds of years. The recovery periods following pre‐Columbian disturbance shared some similar patterns of early succession, but the longer‐term recovery patterns differed. Synthesis. The trajectories of change after a cessation of cultivation can be anticipated to differ depending on the intensity, scale, duration and manner of the past disturbance. In the Kumpaka record, no evidence of persistent enrichment or depletion of intentionally altered taxa (i.e. direct legacy effects) was found but indirect legacy effects, however, were documented and have persisted to the modern day. These findings highlight the strengths of using empirical data to reconstruct past change rather than relying solely on modern plant populations to infer past human management and ecological legacies, and challenge some of the current hypotheses involving the persistence of pre‐Columbian legacies on modern plant populations.

Recovery potential of microwetlands from agricultural land uses

SummaryMany ecosystems located within agricultural landscapes are in decline, particularly woodlands, grasslands and wetlands. Surviving remnants are generally fragmented and unrepresentative of pre‐disturbance states. Here, we investigate the potential for recovery of ecosystem function in a grassy woodland–wetland mosaic in south‐eastern Australia. We focus on the Plains Woodland/Herb‐rich Gilgai Wetland Mosaics which have declined in extent by 85%. The gilgai soils form a distinctive microrelief of mounds and depressions which become seasonally waterlogged, providing important habitat for a large range of aquatic and dryland species. We surveyed 10 remnants subject to agricultural intensification and seven remnants subject to passive restoration (four with cessation of cultivation and three with livestock removal). Gilgai microrelief was homogenized by cultivation, showed some recovery after release from cultivation, and was insensitive to grazing pressure. Floristic diversity, assessed through indicator species, was vulnerable to grazing. Indicator species were more prevalent in previously grazed sites, but further study is required to determine whether this reflects recovery or differing overall management history. We conclude that passive restoration is possible for recovery of wetland function and some biodiversity values. These conservation actions should be encouraged given the important role these microwetlands play in landscape connectivity and as drought refugia.

A prioritization process for invasive alien plant species incorporating the requirements of EU Regulation no. 1143/2014

When faced with a large species pool of invasive or potentially invasive alien plants, prioritization is an essential prerequisite for focusing limited resources on species which inflict high impacts, have a high rate of spread and can be cost‐effectively managed. The prioritization process as detailed within this paper is the first tool to assess species for priority for risk assessment (RA) in the European Union (EU) specifically designed to incorporate the requirements of EU Regulation no. 1143/2014. The prioritization process can be used for any plant species alien to the EU, whether currently present within the territory or absent. The purpose of the prioritization is to act as a preliminarily evaluation to determine which species have the highest priority for RA at the EU level and may eventually be proposed for inclusion in the list of invasive alien species of EU concern. The preliminary risk assessment stage (Stage 1), prioritizes species into one of four lists (EU List of Invasive Alien Plants, EU Observation List of Invasive Alien Plants, EU List of Minor Concern and the Residual List) based on their potential for spread coupled with impacts. The impacts on native species and ecosystem functions and related ecosystem services are emphasized in line with Article 4.3(c) of the Regulation. Only those species included in the EU List of Invasive Alien Plants proceed to Stage 2 where potential for further spread and establishment coupled with evaluating preventative and management actions is evaluated. The output of Stage 2 is to prioritize those species which have the highest priority for a RA at the EU level or should be considered under national measures which may involve a trade ban, cessation of cultivation, monitoring, control, containment or eradication. When considering alien plant species for the whole of the EPPO region, or for species under the Plant Health Regulation, the original EPPO prioritization process for invasive alien plants remains the optimum tool.

Microbiological indicators of soil quality and degradation following conversion of native forests to continuous croplands

Deforestation resulting from forest conversion to agricultural land use is an important issue worldwide. This phenomenon is known to influence the activity and size of soil microbial community due to changes in environmental conditions with subsequent losses of soil organic matter (SOM) and soil quality degradation. The objective of this study was to investigate the relationship between soil organic carbon (SOC) losses and enzyme activities following land use conversion from native forests to continuous croplands. The amount of soil microbial biomass carbon (SMBC) and the activity of five soil enzymes (i.e., urease, invertase, alkaline phosphatase, acid phosphatase and arylsulfatase) were measured in croplands derived from forests and adjacent natural forests all on similar soil type at Gorgan site located in Northeast Iran. The content of SMBC decreased (47–83%) with deforestation at both soil sampling depths (0–20 and 20–40cm). With the exception of phosphatases, the absolute activities of soil enzymes (activity on a soil mass basis) tended to decrease significantly (15–35%) with continuous cultivation. However, the specific enzyme activities expressed either per unit of SOC or SMBC tended to increase (about 1.5–5.5 times) with conversion of forestlands to croplands. The significant positive correlation between enzyme activity per SMBC and C turnover rate may imply that a faster C cycle and loss due to deforestation is related to a greater enzymatic activity by a smaller size of microbial biomass in cropland soils. In brief, the specific activities of soil enzymes could be used to reveal SOM losses and soil degradation in natural forest ecosystems, and to identify changes in soil quality and fertility following deforestation. Changes or improvements in soil management such as cessation of cultivation or implementing agricultural practices that stop or minimize soil disturbance are most likely needed to stop further soil degradation, restore soil quality and rebuild SOC stocks to offset CO2 emissions in these ecosystems.

The Impact of Olive Orchard Abandonment and Rehabilitation on Pollen Signature: An Experimental Approach to Evaluating Fossil Pollen Data

For millennia the olive was an important cultivated tree in the southern Levant, as evidenced by numerous archaeological finds and Holocene pollen assemblages. However, the impact of abandonment and rehabilitation of olive orchards (a recurrent historical process) on the fossil pollen record has not been studied. We documented quantitative differences in the olive pollen signature in a well-managed traditional olive orchard, an abandoned orchard, and an orchard rehabilitated after decades of abandonment, establishing the biological basis for understanding the olive pollen signature. The results indicate a strong decline in flowering and pollen production for decades following the cessation of cultivation and a rapid increase following rehabilitation. This strong response suggests that the fossil pollen curves are a reliable marker for determining the extent of olive oil production in ancient times. In terms of agricultural/economic efficiency, rehabilitation of an orchard takes much less time than establishing a new orchard. This could have been one of the reasons why the same sites were reoccupied during peaks of settlement activity in antiquity. The recent field results are compared to fossil pollen data from the Sea of Galilee during the Bronze and Iron Ages.

Colonization and Recovery of Invertebrate Ecosystem Engineers during Prairie Restoration

AbstractAnts (Hymenoptera: Formicidae) and earthworms (Oligochaeta) are considered ecosystem engineers because they form biogenic structures in the soil that influence resource supply. The objectives of this study were to quantify recovery dynamics of these invertebrate groups across a chronosequence of restored prairies and elucidate whether changes in the abundance and biomass of ants and earthworms were related to key plant and ecosystem properties. We sampled ants and earthworms from cultivated fields, grasslands restored from 1 to 21 years, and native prairie. Ant abundance and biomass peaked between 5 and 8 years of restoration and abundance was 198 times greater than cultivated fields. Earthworm abundance increased linearly across the chronosequence and became representative of native prairie, but all earthworm populations were dominated by European species. Ant abundance and biomass were positively correlated with plant diversity and plant richness, whereas earthworm abundance biomass was only related to surface litter. These results demonstrate that earthworm abundance increases with time since cessation of cultivation and concomitant with prairie establishment, whereas the abundance and biomass of ants are more related to the structure of restored plant communities than time. The dominance of exotic earthworms in these restorations, coupled with their capacity to alter soil properties and processes may represent novel conditions for grassland development.

Soil aggregate stability increase is strongly related to fungal community succession along an abandoned agricultural field chronosequence in the Bolivian Altiplano

Summary Soil aggregate stability is an important ecosystem property which deteriorates overtime due to agricultural practices. The cessation of cultivation allows the potential recovery of soil aggregate binding agents such as soil micro‐organisms and biochemical properties. Consequently, an increase in soil aggregate stability is expected. However, this outcome is difficult to predict because the response of each individual soil component and its contribution to soil stability varies. This study utilized a chronosequence of 12 ex‐arable fields in the Bolivian Altiplano, representing six soil ages of abandonment after cessation of potato cultivation, to examine whether soil aggregate stability increases after abandonment and the extent to which changes in soil bacterial and fungal community composition and soil chemical properties are involved in stability recovery. Fields with the longest time since disturbance (15 and 20 years) have a greater proportion of water‐stable aggregates than more recently abandoned fields (1 and 3 years) and exhibit larger differences in bacterial and fungal composition. Total N, , C and organic matter also increased with time since the last intensive agricultural practice. Water‐stable aggregates were strongly correlated with soil fungal community composition. Analysis of covariance is also consistent with the soil fungal community being an important mediator of the recovery of aggregate stability. Synthesis and applications. Soil aggregate stability increased by 50% over the 20 years following disturbance. This recovery was associated with shifts in soil fungal community composition, as is consistent with fungal mediation of this recovery. Land management strategies focusing on restoration of the soil fungal community may enhance soil aggregate stability, a key aspect for soil conservation, restoration, sustainability of agroecosystems and erosion prevention.

Effects of cultivation and abandonment on soil carbon content of subalpine meadows, northwest China

Land use changes have a significant impact on soil carbon emission and sequestration worldwide. Accurate evaluation of the effect of land use change (cultivation and abandonment) on soil carbon content of subalpine meadows is required to monitor the soil carbon dynamics of rangeland ecosystems in China. Based on collection of soil cores and vegetation, investigations of four types of land use (undisturbed natural meadow, land cultivated for 20 years, land abandoned for 3 years following cultivation, and land abandoned for 10 years following cultivation) were undertaken in the headwater area of the Heihe River in northwest China. Three soil carbon fractions [soil organic carbon (SOC), light fraction organic carbon (LFOC), and microorganism biomass carbon (MBC)] were determined in the laboratory, and the relative abundances of LFOC/SOC and MBC/SOC were calculated. Repeated cultivation by ploughing reduced the carbon content of the top soil layer, resulting in more uniform vertical distribution of soil organic matter. Ten years after cessation of cultivation, the organic carbon content within the top 10-cm soil layer (0–10 cm) had reached 90 % of the content in native meadows, equivalent to a mean annual sequestration rate of 1.73 t C ha−1. The rate of LFOC restoration was faster than that of SOC restoration. The variation in the ratio of MBC to SOC (0.91–1.07 %) was small. The activity of cultivation reduced all indicators of soil carbon status, which were not completely restored to the level of natural meadow, even after abandonment of cultivation for 10 years. Nevertheless, abandonment of cultivation is a practical, even if long-term, means of improving carbon sequestration in subalpine meadow of China.

Soil properties and C dynamics in abandoned and cultivated farmlands in a semi-arid ecosystem

Land abandonment might be an alternative management for restoring soil conditions and C from prolonged cultivation and agricultural practices. In the present study, the influence of 18–22 years of land abandonment on soil properties, C dynamics and microbial biomass was evaluated in closely situated wheat and alfalfa farmlands, and abandoned lands on calcareous soils, Central Iran. Soil properties of the 0–15 and 15–30 cm depths from abandoned lands were compared to those from conventionally cultivated lands (i.e., continuous wheat–fallow and alfalfa–wheat rotation) common in calcareous soils of Central Zagros Mountains. Soil bulk density in the 0–15 and 15–30 cm layers decreased significantly while total porosity increased significantly in abandoned lands. Generally, soil aggregate stability tended to increase within the abandoned fields owing to increased water-stable macro-aggregates. Soil organic C (OC) contents (g kg−1) and pools (Mg ha−1) in the 0–15 cm soil layer increased significantly in abandoned lands compared with cultivated lands, with no effect in the 15–30 cm soil layer after 18–22 years of land abandonment, suggesting the restoration of C is pronounced in the upper 0–15 cm soil depth . The total C accumulation in abandoned lands was 7.0 Mg C ha−1 for the entire sampling depth (0–30 cm) over the 18–22 years of land abandonment, which was 26% greater relative to cultivated lands. Carbon mineralization (Cmin) followed a trend similar to organic C, whereas C turnover (Cmin/OC ratio) was slightly greater in wheat fields. However, soil microbial biomass C (MBC) did not vary considerably among the three land uses. In brief, improvements, albeit slowly, in soil properties of the top layer with the cessation of cultivation indicated that land abandonment may result in enhanced soil C sequestration, and would maintain fertility and productivity of the farmlands of semi-arid climates.

A conceptual model of plant community changes following cessation of cultivation in semi‐arid grassland

AbstractQuestion: Can vegetation changes that occur following cessation of cultivation for cereal crop production in semi‐arid native grasslands be described using a conceptual model that explains plant community dynamics following disturbance?Location: Eighteen native grasslands with varying time‐since‐last cultivation across northern Victoria, Australia.Methods: We examined recovery of native grasslands after cessation of cultivation along a space for‐ time chronosequence. By documenting floristic composition and soil properties of grasslands with known cultivation histories, we established a conceptual model of the vegetation states that occur following cessation of cultivation and inferred transition pathways for community recovery.Results: Succession from an exotic‐dominated grassland to native grassland followed a linear trajectory. These changes represent an increase in richness and cover of native forbs, a decrease in cover of exotic annual species and little change in native perennial graminoids and exotic perennial forbs. Using a state‐and‐transition model, two distinct vegetation states were evident: (1) an unstable, recently cultivated state, dominated by exotic annuals, and (2) a more diverse, stable state. The last‐mentioned state can be divided into two further states based on species composition: (1) a never‐cultivated state dominated by native perennial shrubs and grasses, and (2) a long‐uncultivated state dominated by a small number of native perennial and native and exotic annual species that is best described as a subset of the never‐cultivated state. Transitions between these states are hypothesized to be dependent upon landscape context, seed availability and soil recovery.Conclusions: Legacies of past land use on soils and vegetation of semi‐arid grasslands are not as persistent as in other Australian communities. Recovery appears to follow a linear, directional model of post‐disturbance regeneration which may be advanced by overcoming dispersal barriers hypothesised to restrict recovery.

The Nature and Longevity of Agricultural Impacts on Soil Carbon and Nutrients: A Review

Since the domestication of plant and animal species around 10,000 years ago, cultivation and animal husbandry have been major components of global change. Agricultural activities such as tillage, fertilization, and biomass alteration lead to fundamental changes in the pools and fluxes of carbon (C), nitrogen (N), and phosphorus (P) that originally existed in native ecosystems. Land is often taken out of agricultural production for economic, social, or biological reasons, and the ability to predict the biogeochemical trajectory of this land is important to our understanding of ecosystem development and our projections of food security for the future. Tillage generally decreases soil organic matter (SOM) due to erosion and disruption of the physical, biochemical, and chemical mechanisms of SOM stabilization, but SOM can generally reaccumulate after the cessation of cultivation. The use of organic amendments causes increases in SOM on agricultural fields that can last for centuries to millennia after the termination of applications, although the locations that provide the organic amendments are concurrently depleted. The legacy of agriculture is therefore highly variable on decadal to millennial time scales and depends on the specific management practices that are followed during the agricultural period. State factors such as climate and parent material (particularly clay content and mineralogy) modify ecosystem processes such that they may be useful predictors of rates of postagricultural biogeochemical change. In addition to accurate biogeochemical budgets of postagricultural systems, ecosystem models that more explicitly incorporate mechanisms of SOM loss and formation with agricultural practices will be helpful. Developing this predictive capacity will aid in ecological restoration efforts and improve the management of modern agroecosystems as demands on agriculture become more pressing.

Soil Organic Matter Recovery on Conservation Reserve Program Fields in Southeastern Wyoming

AbstractSoil 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. Löve 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−2 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.

Secondary succession, soil formation and development of a diverse community of oribatids and saprophagous soil macro-invertebrates

Investigations into different stages of secondary succession (from a wheat field to a beechwood on Threstone; Northern Germany) demonstrated the formation of a carbon rich top soil in later successional stages. Parallel to changes in plant species and soil formation, there were also changes in species composition and diversity of saprophagous macro-invertebrates (Lumbricidae, Diplopoda, Isopoda) and oribatid mites (Acari: Oribatida). Diversity of diplopod and isopod species increased after cessation of cultivation, but in a late successional stage (ca 50 y-old fallow, ash-dominated wood) species number of diplopods and isopods declined strongly. In comparison with the other soil invertebrate groups, species composition of earthworms among the sites was more similar. Accumulation of soil C was assumed to be related to wood formation and occurrence of woody debris and recalcitrant leaf litter of beech trees. Incorporation of recalcitrant litter materials by earthworm species living in the upper mineral soil presumably contributed significantly to accumulation of soil C. Accumulation of soil C was accompanied by the development of an oribatid mite community rich in species. In early successional stages oribatids predominantly colonized the litter layer, while most oribatid mites of the beechwood inhabited the upper mineral soil. Maximum diversity of oribatid mites in the beechwood is assumed to be related to instability of the mineral soil caused by earthworm activity. Changes in species composition and diversity are discussed considering succession theory. Even soil invertebrates of similar trophic groups appear to respond very differently to successional changes. It is concluded that conservation strategies to maintain high diversity of soil invertebrates are most likely to be successful if a wide range of habitats of different successional stages is included.

Changes in the lumbricid coenosis during secondary succession from a wheat field to a beechwood on limestone

During the autumns of 1986 and 1988 earthworm populations and biomasses were determined at five different sites [a wheat field, a 4 and 11 yr old fallow, ca 50 yr old fallow (ash-dominated wood) and a beechwood], all of which were located on a limestone plateau near Göttingen (northern Germany). The sites were chosen to represent different stages of a secondary succession after cessation of cultivation. The beechwood forms the climax ecosystems on limestone in the submontane belt of Central Europe. The earthworm fauna was determined by a combination of two methods: earthworms inhabiting the litter layer and the upper 6 cm of the mineral soil were extracted by heat. Deeper dwelling species were sampled using formalin expulsion. Changes in populations, biomasses and dominance structure of earthworms during succession are documented and discussed in relation to vegetation and abiotic factors. Earthworm density was low in the field and the 11 yr old fallow and high in the 4 yr old fallow, the ca 50 yr old fallow and the beechwood. Earthworm biomass in the field, the 4 yr old fallow and the beechwood exceeded that of the 11 and the ca 50 yr old fallow considerably. Changes in density and biomass of anecic and endogeic species during succession were different from that of epigeic species. The most important factor for the small populations of endogeic species in the wheat field is assumed to be deeper freezing of the upper soil horizons during winter caused by the absence of a litter layer. Low biomass of earthworms in the ca 50 yr old fallow site is considered to result from the absence of a leaf litter layer between early summer and autumn, i.e. by the lack of food substrate.

Nutrient cycles and successional changes following shifting cultivation practice in moist semi-deciduous forests in Nigeria

The nutrient contents of moist semi-deciduous forest, successional regrowth and cultivated soils were studied along with successional changes following clear-cutting and burning. Water-soluble N, P, Ca, Mg and K were measured in the primary forest, successional regrowth, cultivated soils and soils of secondary forests ranging from 1 to 6 years after cessation of cultivation. Clearing and burning of the forest releases stored essential nutrients to soils under cultivation. K and N seem to be lost more rapidly in soils under cultivation than in soils under successional regrowth. It was observed that under shifting cultivation essential nutrients build up temporarily; P and Ca rapidly build up in cultivated soils to values much higher than their original values in the forest soils. Six years after the cessation of cultivation, the soil nutrient level of the successional regrowth was still far from being restored to the level of the primary forest soils. Seedlings and resprouts were equally important in the vegetation recovery of burnt and unburnt clear-cut forest. Seedlings of pioneer woody species established themselves in the burnt and unburnt plots within 4 months. Secondary regrowth in the burnt plot appeared better than in the unburnt plot, although resprouts played a more significant role in the unburnt plot.