Combined Effects Of Land-use Change Research Articles

Responses of soil organic carbon mineralization and its temperature sensitivity to re-vegetation in the agro-pastoral ecotone of northern China

Re-vegetation of cropland is an important measure for carbon (C) sequestration, while the combined effects of land-use change, re-vegetation type and time on soil organic C (OC) turnover and temperature sensitivity have been less studied. Here, we investigated soil cumulative OC mineralization (Cmin), specific OC mineralization (Cmin/C0, normalized by initial OC) and temperature sensitivity (Q10) with an 84-d incubation experiment after the conversion of cropland to artificial grassland (6, 10, 15 and 20 yr), to natural grassland (6, 10 and 20 yr) and to pea shrub woodland (10, 20 and 40 yr) in the agro-pastoral ecotone of northern China. Results showed that re-vegetation significantly increased Cmin (from 38.21 to 57.79 mg kg−1 soil, +51%) at the 0–10 cm depth but not the 10–20 cm depth, with greater increases after the conversion of cropland to artificial grassland (+77%) than the other two patterns but similar among different conversion years for each pattern. Variations in Cmin among different re-vegetation patterns and times were mostly explained by changes in total nitrogen concentration (TN) in the macro-aggregate fraction. Across all treatments, 6.20–20.29 g kg−1 OC was mineralized during the incubation and Q10 was 1.16–2.40. The Cmin/C0 and Q10 changed not significantly during the post-agricultural re-vegetation chronosequences for each pattern, which were mostly due to the unchanged TN concentration in silt and clay fraction. Re-vegetation also changed the dependence of Cmin, Cmin/C0 on N availability, with significant relationships in re-vegetated artificial grassland and pea shrub woodland which may due to the influence of legumes on microbes. In conclusion, OC mineralization increased with conversion, varying by re-vegetation type, while OC decomposability and temperature sensitivity were stable regardless of re-vegetation type and time, indicating the similar biodegradability and stability in face of warming.

Land Use Changes, Disturbances, and Their Interactions on Future Forest Aboveground Biomass Dynamics in the Northern US

Land use change (LUC), disturbances, and their interactions play an important role in regional forest carbon (C) dynamics. Here we quantified how these activities and events may influence future aboveground biomass (AGB) dynamics in forests using national forest inventory (NFI) and Landsat time series data in the Northern United States (US). Total forest AGB predictions were based on simulations of diameter growth, mortality, and recruitment using matrix growth models under varying levels of LUC and disturbance severity (low (L), medium (M), and high (H)) every five years from 2018 to 2098. Land use change included the integrated effects of deforestation and reforestation/afforestation (forest [F]→agriculture [A], settlements [S, urbanization/other], and A&S→F), specifically, conversion from F→A, F→S, F→A&S, A→F, S→F, and A&S→F. Disturbances included natural and anthropogenic disturbances such as wildfire, weather, insects and disease, and forest harvesting. Results revealed that, when simultaneously considering both medium LUC and disturbances, total forest AGB predictions of LUC + fire, LUC + weather, LUC + insect & disease, and LUC + harvest indicated substantial increases in regional C stocks (± standard deviation) from 1.88 (±0.13) to 3.29 (±0.28), 3.10 (±0.24), 2.91 (±0.19), and 2.68 (±0.17) Pg C, respectively, from 2018 to 2098. An uncertainty analysis with fuzzy sets suggested that medium LUC under disturbances would lead to greater forest AGB C uptake than undisturbed forest C uptake with high certainty, except for LUC + harvest. The matrix models in this study were parameterized using NFI and Landsat data from the past few decades. Thus, our results imply that if recent trends persist, LUC will remain an important driver of forest C uptake, while disturbances may result in C emissions rather than undisturbed forest C uptake by 2098. The combined effects of LUC and disturbances may serve as an important driver of C uptake and emissions in the Northern US well into the 21st century.

Natural disasters and land-use/land-cover change in the southwest coastal areas of Bangladesh

Natural hazards and major land-use/land-cover change can have significant impacts on humans around the world. If these two concerns exist together in a coastal area, the consequences for people and the environment may be severe. This study investigated the combined effects of land-use changes and natural disasters in the southwest coastal area of Bangladesh. Satellite images were analyzed to detect changes in land cover in the study period of 13 years (1999–2012). Three areas were selected for ground data collection. Household surveys and focus groups were conducted to discover the type, level and effects of disasters. Probit regression analysis was performed to assess the relationship between various disasters with overall income, agricultural production and outward migration. Results from image analysis showed an overall 30 % increase in shrimp culture ponds in the past 13 years. Agricultural land and vegetation decreased by 48 and 3 %, respectively. Barren and built-up areas increased by 73 % due to both land-use activity and natural hazards. Analysis of household data showed cyclones and storm surges had important effects on income, agricultural production and migration. Sustainable management and enhancement of resilience capacity of this area will be crucial in the near future.

The effects of deer herbivory and forest type on tree recruitment vary with plant growth stage

Understanding the combined effects of land-use changes and expanding generalist herbivores on the recruitment of tree species is critical to predict forest community dynamics and for fulfilling conservation purposes. We assessed how deer herbivory and forest-type affected the diversity of seedlings and saplings of dominant tree species in a temperate forest of Eastern USA, during four consecutive years. Fenced and unfenced plots were established in hardwood and pine forests and tree seedlings and saplings identified and monitored annually. Tree recruitment patterns varied widely from year to year, particularly for seedlings. Sapling communities were richer in species, more diverse and with lower indexes of dominance than seedling communities. The diversity of seedlings and saplings was significantly affected by inter-annual variation of tree recruitment but not by deer herbivory or forest type. Herb cover was reduced for more than fourfold in unfenced hardwood plots. Results show that inter-annual variation of recruitment, herbivory and forest type can combine to shape the composition of tree seedlings and saplings. When assessing effects of deer on tree recruitment interactions between biotic (e.g. herbivory) and abiotic (e.g. forest type) factors need to be considered. The outcome of such interactions depends on seedling or sapling life stage.

The possible combined effects of land-use changes and climate conditions on the spatial–temporal patterns of primary production in a natural protected area

Multifunctional landscapes are characterized by various functions and values that sustain directly or indirectly the quality of human life, through the provision of natural capital flow. Primary production (PP), representing a measure of the solar energy captured by the system and available to drive its functioning, is recognized as a fundamental supporting service. Several biophysical modification and conversion altering the primary production are due to land-use change. Natural protected areas with a sustainable management of land-use could be able to guarantee the persistence of structure and processes (primary production) fundamental for the provision of natural capital. In this context, the aims of this paper are to investigate the spatial–temporal patterns of PP variability (1986–2010) in the Natural Protected Area of “Torre Guaceto” (southern Italy), taking into account land-cover change and climate conditions and looking at PP as a supporting service able to guarantee natural capital flow. In dealing with this issue, this paper aims at testing whether NDVI (Normalized Difference Vegetation Index) integrated with NDII (Normalized Difference Infrared Index) can be suitable surrogates for the assessment of shifts in the spatial–temporal dynamics of PP, useful to explore possible feedbacks related to conservation management choices in supporting natural capital flow. Therefore, the assessment of the complex spatial–temporal dynamics of natural vegetation has been performed by using NDVI and NDII. The results showed that after the establishment of the Natural Protected Area of “Torre Guaceto” in 2000, there has been an increase of NDVI that could represent an increase of PP. However, since PP depends also on water content, measured by NDII, a Pearson correlation analysis between NDII and land Surface Temperature (TS) has been carried out, demonstrating that low level of PP in 2005 was not imputable to climate conditions but to the worse quality of vegetation associated to the wetland due to aging phenomenon. In conclusion, to make the conservation management more effective it is not enough to identify and quantify the major landscape transformations and the underlying causes, but rather to detect the capability of new landscape patterns, in terms of configuration and composition, to sustain ecosystem services. The analysis of conservation management based on NDVI and NDII, used as surrogate to detect the maintenance of PP, appears to be very promising in order to develop better strategies for the adaptive management of natural protected areas.

Dominance of an invasive earthworm in native and non-native grassland ecosystems

More attention is currently being focused on earthworm invasions; however, in many ecosystems the relative abundance of native and invasive earthworm species is unknown. We characterized earthworm populations of two grassland types within the Palouse region: native prairie remnants and Conservation Reserve Program (CRP) set asides planted with exotic grasses. The earthworm community in both grassland types was completely dominated by the exotic-invasive Aporrectodea trapezoides. Only one individual of a native species, Driloleirus americanus (the giant Palouse earthworm), was found in a prairie remnant. No differences were found between prairie remnants and CRP sites for mean earthworm density (24–106 individuals m−2) or fresh weight (12–45 g m−2). Our results suggest that the combined effects of land-use change, habitat fragmentation and competitive interactions have resulted in the decimation of native earthworm populations and dominance of invasive earthworms in native and non-native grasslands of the Palouse region.

Application of a spreadsheet hydrological model for computing the long-term water balance of Lake Awassa, Ethiopia

The water balance of the closed freshwater Lake Awassa was estimated using a spreadsheet hydrological model based on long-term monthly hydrometeorological data. The model uses monthly evaporation, river discharge and precipitation data as input. The net groundwater flux is obtained from model simulation as a residual of other water balance components. The result revealed that evaporation, precipitation, and runoff constitute 131, 106 and 83 × 106 m3 of the annual water balance of the lake, respectively. The annual net groundwater outflow from the lake to adjacent basins is 58 × 106 m3. The simulated and recorded lake levels fit well for much of the simulation period (1981–1999). However, for recent years, the simulated and recorded levels do not fit well. This may be explained in terms of the combined effects of land-use change and neotectonism, which have affected the long-term average water balance. With detailed long-term hydrogeological and meteorological data, investigation of the subsurface hydrodynamics, and including the effect of land-use change and tectonism on surface water and groundwater fluxes, the water balance model can be used efficiently for water management practice. The result of this study is expected to play a positive role in future sustainable use of water resources in the catchment.