Vegetation Management Policies Research Articles

Human‐Climate Coupled Changes in Vegetation Community Complexity of China Since 1980s

AbstractVegetation community complexity is a critical factor influencing terrestrial ecosystem stability. China, the country leading the world in vegetation greening resulting from human activities, has experienced dramatic changes in vegetation community composition during the past 30 years. However, how China's vegetation community complexity varies spatially and temporally remains unclear. Here, we examined the spatial pattern of China's vegetation community complexity and its temporal changes from the 1980s to 2015 using two vegetation maps of China as well as more than half a million field samples. Spatially, China's vegetation community complexity distribution is primarily dominated by elevation, although temperature and precipitation can be locally more influential than elevation when they become the factors limiting plant growth. Temporally, China's vegetation community complexity shows a significant decreasing trend during the past 30 years, despite the observed vegetation greening trend. Prevailing climate warming across China exhibits a significant negative correlation with the decrease in vegetation community complexity, but this correlation varies with biogeographical regions. The intensity of human activities have an overall negative influence on vegetation community complexity, but vegetation conservation and restoration efforts can have a positive effect on maintaining vegetation composition complexity, informing the critical role of vegetation management policies in achieving the sustainable development goal.

Evaluation of Spatio-Temporal Soil Moisture Variability in Semi-Arid Rangeland Ecosystem, Maasai Mara National Reserve, Kenya

Aim: To evaluate the spatio-temporal soil moisture storage and retention capacities in semi-arid rangeland ecosystem, Maasai Mara National Reserve (MMNR), Kenya
 Study Design: Randomized complete block design (RCBD) of reference Cosmic Ray Neutron Sensor (CRNS) station, ten-(10) spatially distributed (soil moisture and temperature capacitance) probes (5TM-ECH20) sites.
 Place and Duration of Study: Kenya, MMNR, the oldest natural semi-arid rangeland ecosystem and globally unique for the great wildebeest migration, between May 2017 and April 2019.
 Methodology: Soil moisture (SM) variation data was collected using (CRNS) at spatial and point-scale 5TM-ECH2O probes, and gravimetric water content from (10) spatially distributed stations. Both CRNS and 5TM-ECH2O probes were used to monitor near-real time moisture levels at different soil layers ranging between 0-5cm, 5-10cm, 15-20cm, 35-40cm, and 75-80cm. Soil physical and chemical properties were laboratory analyzed. Calibration and validation datasets were obtained from 5TM-ECH2O probe and gravimetric soil samples extracted from respective layers and sites.
 Results: The pedological characteristics of the investigated ecosystem soil profile indicate decreased bulk density by 2.1% to 11.12% from upper layers (0-5cm) to deeper layers at (75–80 cm). Across the rangeland, 70% of soil textural classes were sandy clay loam (SCL) with higher clay percent and 30% sandy clay (SC) and soil porosity varied between 30.1% and 51% in the ecosystem. Moreover, volumetric
 
 
 
 
 
 
 
 
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 water content (VWC) of spatially distributed 5TM-ECH2O probes ranged between 0.11m3m-3 and 0.32m3m-3 during wet season with mean VWC of 0.16m3m-3, however, the VWC ranged between 0.04 m3m-3 and 0.17m3m-3 during the dry season with a mean volume of 0.11m3m-3 across the rangeland ecosystem.
 Conclusion: In this study, SM exhibited an annual periodicity of seasonal variation of spatial and temporal moisture partitioned as moisture gaining, losing, and a moisture stable period. This probably could be a consequence of increased movement of water to deeper layers caused by high precipitation and less evaporative demand caused by lower temperatures. The calibrated CRNS probe provided good estimates of spatial soil moisture variation when calibrated with 5TM-ECH20 and gravimetric sampling in relation to precipitation events and that deeper soil layers showed higher amount of soil moisture than shallow layers. The findings of the study will provide better formulation of the ecosystem vegetation management policies, conservation and planning for sustainable wildlife tourism industry.

Quantifying the impact of vegetation changes on global terrestrial runoff using the Budyko framework

The global hydrological cycle is undergoing unprecedented changes with the intensifications of climate change and human activities. In particular, the impact of vegetation changes on the catchment hydrological processes has recently attracted widespread scientific attention. Although such impact in different regions of the globe has been extensively investigated, a comprehensive understanding of the impact across the entire globe remains elusive. In this study, we quantify the impact of vegetation change on surface runoff (Q) based on the Budyko framework over the global terrestrial environments (excluding Antarctica and northern high latitudes) during 1982–2014. Using long-term hydrometeorological observations and satellite-derived leaf area index (L) from 663 strictly selected catchments globally, we quantify the sensitivity of the Budyko parameter n to changes in L (Sn_L) at individual catchments. We find that Sn_L is closely correlated with catchment aridity index (φ) and soil water holding capacity (θp), with higher (lower) Sn_L found in more arid (humid) catchments and catchments having smaller (larger) θp values. Based on this, an empirical model relating Sn_L to φ and θp is developed, which is further combined with the Budyko model to quantify the L and climate elasticities of Q and to attribute global Q changes over 1982–2014. Results show that the L elasticity of Q is higher and can be even greater than the climate elasticities of Q in relatively dry regions. Averaged over the globe, an increase in Q (+15.5%) induced by precipitation increases are largely offset by a decreased Q (−14.9%) caused by L increases over the last three decades. The vegetation greening-induced Q declines are manifested in global drylands. Over the study period, increases in L have led to Q reductions of 48.0%, 33.2% and 20.2% in global arid, semi-arid and sub-humid regions, respectively, which are larger than climate change-induced Q changes in these three regions. Our findings highlight the importance of vegetation change in regulating the long-term Q changes in relatively dry regions and call for cautions when conducting and/or planning future revegetation activities in these areas and needs for developing appropriate vegetation management policies to better inform water resources management in the context of global change.

Spatial and temporal patterns of land clearing during policy change

Environmental policies and regulations have been instrumental in influencing deforestation rates around the world. Understanding how these policies change stakeholder behaviours is critical for determining policy impact. In Queensland, Australia, changes in native vegetation management policy seem to have influenced land clearing behaviour of landholders. Periods of peak clearing rates have been associated with periods preceding the introduction of stricter legislation. However, the characteristics of clearing patterns during the last two decades are poorly understood. This study investigates the underlying spatiotemporal patterns in land clearing using a range of biophysical, climatic, and property characteristics of clearing events. Principal component and hierarchical cluster analyses were applied to identify dissimilarities between years along the political timeline. Overall, aggregate landholders’ clearing characteristics remain generally consistent over time, though noticeable deviations are observed at smaller regional and temporal scales. While clearing patterns in some regions have shifted to reflect the policy’s goals, others have experienced minimal or contradictory changes following regulation. Potential ‘panic’ or ‘pre-emptive’ effects are evident in the analysis, such as spikes in clearing for pasture expansions, but differ across regions. Because different regions are driven by different pressures, such as land availability and regulatory opportunity, it is imperative that the varying spatial and temporal behavioural responses of landholders are monitored to understand the influence of policy and its evolution. Future policy amendments would benefit from monitoring these regional responses from landholders to better assess the effectiveness of policy and the potential perversities of policy uncertainty.

Modeling fire spread in cities with non-flammable construction

City-scale models of urban fires were developed for countries where most construction is highly flammable, such as the US, China and Japan. Essential adjustments of existing models are required for modeling fire spread at the city scale in urban areas where construction is non-flammable and the space between buildings is filled by flammable vegetation, as in Mediterranean and Middle Eastern cities. We develop a spatially explicit city-scale model of urban fire spread for cities consisting of non-flammable buildings and apply it to different areas of the city of Haifa, Israel. We demonstrate that adequate modeling of fire spread inside non-flammable buildings demands accurate partition of the intra-building space into apartments and corridors. We present and evaluate the algorithm for establishing such partition based on standard GIS layer of the buildings footprints.Based on the model, we demonstrate that fire spread in cities consisting of non-flammable buildings is highly sensitive to the structure of urban vegetation within the immediate surroundings of each building and investigate the effects of vegetation management policies on fire spread mitigation. We discuss the use of the model for establishing the procedures of firefighters’ response during routine and multiple ignition scenarios.

Geometric correction and accuracy assessment of Landsat-7 ETM+ and Landsat-5 TM imagery used for vegetation cover monitoring in Queensland, Australia from 1988 to 2007

A range of programs exist globally that use satellite imagery to derive estimates of vegetation-cover for developing vegetation-management policy, monitoring policy compliance and making natural-resource assessments. Consequently, the satellite imagery must have a high degree of geometric accuracy. It is common for the accuracy assessment to be performed using the root mean square error (RMSE) only. However the RMSE is a non-spatial measure and more rigorous accuracy assessment methods are required. Currently there is a lack of spatially explicit accuracy assessment methods reported in the literature that have been demonstrated to work within operational monitoring programs. This paper reports on the method used by the Statewide Landcover and Trees Study (SLATS) to georegister and assess the registration accuracy of Landsat-5 Thematic Mapper (TM) and Landsat-7 Enhanced Thematic Mapper (ETM+) imagery in Queensland, Australia. A geometric baseline with high accuracy (a statewide mean RMSE of 4.53 m) was derived by registering Landsat-7 ETM+ panchromatic imagery acquired in 2002 to a database of over 1600 control points, collected on the ground using a differential global positioning system. Landsat-5 TM and Landsat-7 ETM+ imagery for 12 selected years from 1988 to 2007 was registered to the baseline in an automated procedure that used linear geometric correction models. The reliability of the geometric correction for each image was determined using the RMSE, calculated using independent check points, as an indicator of model fit; by analysing the spatial trends in the model residuals; and through visual assessment of the corrected imagery. The mean RMSE of the statewide coverage of images for all years was less than 12.5 m (0.5 pixels). Less than 1 percent of images had non-linear spatial trends in the model residuals and some image misregistration after applying a linear correction-model; in those cases a quadratic model was deemed necessary for correction. Further research in the development of automated spatially explicit accuracy assessment methods is required.

Tree species and environment associations within hemlock-silverbell stands treated for hemlock woolly adelgid in Great Smoky Mountains National Park1

The hemlock-silverbell (Tsuga canadensis-Halesia tetraptera) association is endemic to several small stands in federally protected lands in the southern Appalachian Mountains and is currently threatened by the hemlock woolly adelgid (Adelges tsugae). Pre-infestation stand structure was still evident at the time of the study but hemlock mortality and associated vegetation responses portend rapid changes in this system. In order to guide potential future restoration efforts and impact assessments, a study was implemented to determine the structure of hemlock-silverbell stands and to identify environmental variables associated with differences in stand composition in areas of Great Smoky Mountains National Park treated to control hemlock woolly adelgid. Halesia tetraptera and T. canadensis exhibited even-aged and uneven-aged stand structures, respectively. Forest composition varied as a function of environmental variables within the hemlock-silverbell association with overstory H. tetraptera relative density positively correlated with higher water availability (Beers aspect and slope) and overstory T. canadensis was negatively correlated with Beers aspect. Relative density of H. tetraptera and T. canadensis in the understory were similarly associated with higher and lower productivity conditions, respectively. In the understory, Acer pensylvanicum relative density was negatively associated with that of understory T. canadensis. The results suggest that partial canopy removal resulting from the loss of T. canadensis due to hemlock woolly adelgid may benefit aggressive tree species such as A. pensylvanicum. The United States Park Service vegetation management policies, here and in other natural areas where non-native invasive species are controlled (but native species responses are unaccounted for), will need to address this phenomenon if T. canadensis restoration is to be accomplished in the event adelgid control can be achieved.

The role of community policies in defensible space compliance

Recently enacted federal and state policies provide incentives, including financial assistance, for local jurisdictions to manage risks associated with wildland fire. This has led to an array of local-level policies designed to encourage homeowners to create fire-safe landscapes. This qualitative study collected data from focus group interviews with homeowners in three diverse communities and used the theory of reasoned action to interpret dimensions of local-level wildland fire policies that are associated with homeowner acceptance of or compliance with defensible space guidelines or regulations. Common factors emerged in two policy evaluation categories: acceptance and compliance. WUI homeowners are more accepting of policies that are seen as fair and part of a more comprehensive risk reduction strategy. Topics that shaped acceptance of voluntary versus mandatory approaches included perceived risk severity, views about the proper roles of government, and beliefs about alternatives to regulatory approaches (e.g. private insurance, education, ignition source reduction). Program characteristics that were found to be related to beliefs about defensible space and acceptance included provision of one-on-one expert consultation, direct mail communication modes, needs-based financial assistance, and enhanced yard waste disposal options. Homeowner compliance is related to the feasibility in terms of household costs and yard waste disposal options, neighborhood norms, competing land use objectives, insurance considerations, and whether or not the policy is mandatory. These findings led to a proposed conceptual model of vegetation management policy acceptance and compliance that local governments can use to develop or amend defensible space vegetation management policies to increase policy acceptance and compliance.

Integration of visual quality considerations in development of Israeli vegetation management policy.

This article deals with the visual quality of Mediterranean vegetation groups in northern Israel, the public's preference of these groups as a visual resource, and the policy options for their management. The study is based on a sample of 44 Mediterranean vegetation groups and three population groups of local residents, who were interviewed using a questionnaire and photographs of the vegetation groups. The results of the research showed that plant classification methods based on flora composition, habitat, and external appearance were found to be suitable for visual plant classification and for the evaluation of visual preference of vegetation groups by the interviewed public. The vegetation groups of planted pine forests and olive groves, characterizing a cultured vegetation landscape, were preferred over typical Mediterranean landscapes such as scrub and grassed scrub. The researchers noted a marked difference between the two products of vegetation management policy, one that proposes the conservation and restoration of the variety of native Mediterranean vegetation landscape, and a second that advanced the development of the cultured landscape of planted olive groves and pines forests, which were highly preferred by the public. The authors suggested the development of an integrated vegetation management policy that would combine both needs and thus reduce the gap between the policy proposed by planners and the local population's visual preference.

Likely effects of land use changes on the runoff and aquifer recharge in a semiarid landscape using a hydrological model

A hydrological model for the estimation of the water balance components was developed for a semiarid landscape of Spain. These components were: the soil water content, the actual evapotranspiration ( E ta), and both the aquifer recharge (deep drainage) and runoff, which reflected water recharge, human use and soil erosion impacts. Combining the model predictions with the land cover vegetation units on the aquifer recharge area, created through a GIS (IDRISI), we compared the effects of some management policies on the deep drainage and runoff in five simulation scenarios. These scenarios included wildfires and vegetation management policies (afforestation and land abandonment). In order to implement the simulations, three precipitation levels were taken into account: mean annual rainfall in the area (300 mm), a wet year with 400 mm, and a very wet year (553 mm), where one of the rainfall events was an extreme rainfall event (153 mm), with a very high intensity. The results indicated that afforestation would produce a reduction of both the annual aquifer recharge and the runoff for the next 20 years and a wildfire would cause dramatic increases in the present aquifer recharge at current annual average precipitation. The results were not so marked if we took into account wet years and extreme rainfall events. Substantial variation occurred with the increased effect of wildfire on the risk of erosion at current annual average precipitation, but extreme precipitation during a wet year led to a higher erosion risk.

Park Management of Exotic Plant Species: Problems and Issues

Abstract: Vegetation management policies in public parks in the United States call for the removal of exotic species to the extent feasible. The underlying goal is to preserve samples of wilderness by restoring plant communities to the “natural state” that existed prior to extensive human influence. With limited budgets, park managers are necessarily selective in targeting exotic species for control. If the focus is on the more readily controlled species, however, park landscapes may gradually become populated by more resistant exotics Further, because plants exhibit some redundancy in ecosystem function, exotic plant species can substitute in part for natives in performing a range of ecosystem functions, including wildlife support and soil binding. Consequently the removal of exotics can result in significant perturbations to certain ecosystem functions during the period of transition to native cover. The individualistic paradigm of plant distribution implies that the impact of exotic plant species on invaded communities will vary. Choosing which species to remove requires careful evaluation of the impact of the removal on ecosystem structure and function. The effective balancing of park management goals for wilderness maintenance and recreational use requires clearer recognition of the adaptive response of ecosystems to invasion and a rethinking of the bases for prioritizing which species are to be removed.

Managing Vegetation within U.S. National Parks: A Policy Analysis

The development of U.S. national park vegetation management policies is briefly traced from 1872, when Yellowstone National Park was created, to the present. Ambiguities in legislative policies are described and partially resolved. Alternative vegetation management objectives, consistent with those policies, are evaluated using quantitative data from a giant sequoia-mixed-conifer forest community in Kings Canyon National Park. It is concluded from an analysis of this data that structural maintenance objectives are biologically infeasible in this forest community because the community does not have a fully regulated or steady-state distribution of aggregation types. Since such a steady-state distribution of aggregation types is probably not present in most forest communities, the Park Service is generally restricted to pursuing process maintenance objectives for vegetation within national parks and monuments. It is also pointed out that implementation of some process maintenance objectives is complicated by the need to return the forest community to its pre-fire exclusion state before reintroducing fire to the ecosystem. To do otherwise would perpetuate the changes in species composition and structure that have resulted from more than three-quarters of a century of fire exclusion. A new alternative for managing vegetation in national parks that is based on a high resolution description of the presettlement forest community, called the reconstruction-simulation approach, is also presented.