The Indiana Climate Change Impacts Assessment (IN CCIA) is a collaborative effort to provide professionals, decision makers, and the public with information about how climate change affects state and local interests throughout Indiana, USA. This assessment effort has three interrelated goals: (1) analyze and document the best available climate change impacts research, (2) develop and maintain a network of stakeholders and experts, and (3) start a dialog about climate change throughout Indiana. The project adopted a process that prioritized stakeholder engagement, re-envisioned traditional dissemination approaches, and that had limited state government involvement, setting the IN CCIA apart from most other state climate assessments (SCAs) in the USA. This overview describes the motivations, principles, and processes that guided the IN CCIA development, explores how Indiana's approach compares with those of other SCAs, and briefly summarizes the papers presented in this special issue. As interest in SCAs grows in non-coastal and politically conservative locations, the IN CCIA serves as one example of how a bottom-up assessment with limited funding can deliver credible climate science to diverse stakeholder groups in the absence of state-level mandates or direction and attract public attention over an extended period of time.

As Earth's climate rapidly changes, species range shifts are considered key to species persistence. However, some range-shifting species will alter community structure and ecosystem processes. By adapting existing invasion risk assessment frameworks, we can identify characteristics shared with high-impact introductions and thus predict potential impacts. There are fundamental differences between introduced and range-shifting species, primarily shared evolutionary histories between range shifters and their new community. Nevertheless, impacts can occur via analogous mechanisms, such as wide dispersal, community disturbance and low biotic resistance. As ranges shift in response to climate change, we have an opportunity to develop plans to facilitate advantageous movements and limit those that are problematic.

While all sectors of the economy can be impacted by climate variability and change, the agricultural sector is arguably the most tightly coupled to climate where changes in precipitation and temperature directly control plant growth and yield, as well as livestock production. This paper analyzes the direct and cascading effects of temperature, precipitation, and carbon dioxide (CO2) on agronomic and horticultural crops, and livestock production in Indiana through 2100. Due to increased frequency of drought and heat stress, models predict that the yield of contemporary corn and soybean varieties will decline by 8-21% relative to yield potential, without considering CO2 enhancement, which may offset soybean losses. These losses could be partially compensated by adaptation measures such as changes in cropping systems, planting date, crop genetics, soil health, and providing additional water through supplemental irrigation or drainage management. Changes in winter conditions will pose a threat to some perennial crops, including tree and fruit crops, while shifts in the USDA Hardiness Zone will expand the area suitable for some fruits. Heat stress poses a major challenge to livestock production, with decreased feed intake expected with temperatures exceeding 29 degrees C over 100 days per year by the end of the century. Overall, continued production of commodity crops, horticultural crops, and livestock in Indiana is expected to continue with adaptations in management practice, cultivar or species composition, or crop rotation.

In the face of ongoing and projected climatic changes, precipitation manipulation experiments (PMEs) have produced a wealth of data about the effects of precipitation changes on soils. In response, researchers have undertaken a number of synthetic efforts. Several meta-analyses have been conducted, each revealing new aspects of soil responses to precipitation changes. Here, we conducted a comparative analysis of the findings of 16 meta-analyses focused on the effects of precipitation changes on 42 soil response variables, covering a wide range of soil processes. We examine responses of individual variables as well as more integrative responses of carbon and nitrogen cycles. We find strong agreement among meta-analyses that belowground carbon and nitrogen cycling accelerate under increased precipitation and slow under decreased precipitation, while bacterial and fungal communities are relatively resistant to decreased precipitation. Much attention has been paid to fluxes and pools in carbon, nitrogen, and phosphorus cycles, such as gas emissions, soil carbon, soil phosphorus, extractable nitrogen ions, and biomass. The rates of processes underlying these variables (e.g., mineralization, fixation, and (de)nitrification) are less frequently covered in meta-analytic studies, with the major exception of respiration rates. Shifting scientific attention to these less broadly evaluated processes would deepen the current understanding of the effects of precipitation changes on soil and provide new insights. By jointly evaluating meta- analyses focused on a wide range of variables, we provide here a holistic view of soil responses to changes in precipitation.

Tropical vegetation influences local, regional, and global climates, largely through its relationship with the atmosphere, including seasonal patterns of photosynthesis and transpiration. Removal and replacement of natural vegetation can alter both of these processes. In the Amazon, land use/land cover change (LULCC; e.g. deforestation) started decades ago and is expected to continue, with potentially strong effects on climate. However, long-term data on tropical photosynthetic activity and transpiration are scarce, limiting our ability to estimate large-scale effects of LULCC. Here, we use remote sensing data to analyze the impact of LULCC on seasonal patterns of photosynthetic activity and transpiration in the southern Amazon. This region, naturally dominated by forest and Cerrado, has seen high rates of LULCC. Within each of these two ecosystems, we compare estimates of photosynthetic activity (from GOME-2 and GOSIF solar induced fluorescence, SIF) and transpiration (from the Global Land Evaporation Amsterdam Model, GLEAM) in paired sites with high and low rates of LULCC. In forest-dominated regions, deforestation has reduced photosynthetic activity and transpiration, particularly during the dry season, and replaced dry season greening with dry season browning. The SIF datasets disagree on wet season responses; SIF increases with deforestation according to GOME-2, but decreases according to GOSIF. In Cerrado-dominated areas, LULCC has increased photosynthetic activity during the wet season. In both ecosystems, LULCC has resulted in a higher seasonal or annual range of photosynthetic activity levels. The observed effects are often stronger in regions with more extensive LULCC. We found large differences between the two SIF products in both forest- and Cerrado-dominated pixels, with GOME-2 consistently providing higher maximum SIF values. These discrepancies merit further consideration. This analysis broadly characterizes the effects of LULCC on photosynthetic activity and transpiration in this region, and can be used to validate model representations of these effects.

Ongoing climate change is increasing rainfall variability in many parts of the world; in particular, the heaviest rainfall events are becoming heavier. In terrestrial ecosystems, nitrogen deposition is increasing as a result of emissions from fossil fuel burning and volatilization of nitrogen-based fertilizers. These changes in the timing and rate of resource inputs can impact plant communities by altering competitive dynamics, succession, and community composition. In many systems, these are occurring alongside successional dynamics, making it difficult to tease apart mechanisms. Here, we resampled a nitrogen by rainfall variability manipulation experiment in a restored tallgrass prairie to examine the relative role of background community dynamics and treatment effects on plant diversity. During the treatment period, nitrogen addition and increased rainfall variability reduced diversity. Here, four and five years after the treatments were halted, we found similarly low levels of diversity across all treatments-an effect driven by dominance of a tall, fast-growing, clonal forb, Solidago canadensis. The convergence of plots toward a low diversity state suggests that all experimental communities were gradually becoming dominated by S. canadensis, including in the absence of rainfall or nitrogen treatments. In contrast to short-term findings from the same experiment, we conclude that our treatments accelerated succession toward a tall, clonal forb-dominated community along an existing sere, but did not fundamentally alter longer-term community composition-a result that was only apparent several years after the conclusion of the experiment. These findings reinforce the need to interpret the results from short-term experimental manipulations within the context of long-term successional change.

Theories of plant invasions predict that plant communities should be more easily invaded when resources increase and/or competition decreases. We tested this with an experimentally introduced plant population by manipulating precipitation and resident community biomass. We used a spatially explicit demographic approach to develop a new population-level metric of invasibility that quantifies the invasible habitat fraction (IHF) across the landscape. The existing community was essentially uninvasible (median IHF approximate to 0%), but experimental manipulations greatly increased the range of outcomes, with maximum observed IHF values over 50%. However, changes in invasibility were often context-dependent, resulting in some outcomes that aligned with existing theory, and others that were not readily predicted. Moreover, variation in invasibility was often driven by specific sets of invader demographic vital rates. Removing competitors revealed the capacity for strong biotic resistance, but this interacted with precipitation such that little biotic resistance was detected under drought conditions. Adding precipitation typically had little positive effect on invasibility, and moderate drought relief led to relatively high invasibility. However, the latter was driven to a large extent by interactions with mammal herbivory that otherwise inhibited invasion in one year. Synthesis. Our findings show that interactions between abiotic and biotic factors, as well as legacy effects, can strongly mediate invasibility. This study also highlights the importance of incorporating spatial heterogeneity into population-level assessments of invasion, as initial population declines do not necessarily indicate resistance to invasion.

The significant portion of global terrestrial biodiversity harboured in the mountains is under increasing threat from various anthropogenic impacts. Protecting fragile mountain ecosystems requires understanding how these human disturbances affect biodiversity. As roads and railways are extended further into mountain ecosystems, understanding the long-term impacts of this infrastructure on community composition and diversity gains urgency. We used railway corridors constructed across the mountainous landscapes of the Kashmir Himalaya from 1994 to 2013 to study the effects of anthropogenic disturbance on species distributions and community dynamics. In 2014 and 2017, we collected vegetation data along 31 T-shaped transects laid perpendicular to the railway line, adopting the MIREN (Mountain Invasion Research Network) road survey methodology. Plant communities shifted significantly from 2014 to 2017, potentially because of an ongoing species redistribution after railway construction, driven mainly by declines in both native and non-native species richness, and an increasing abundance of a few non-native species, especially in areas away from the railway track. These patterns indicate an advancing succession, where initially-rare-pioneer species are replaced by increasingly dominant and often non-native competitors, and potentially suggest a trend towards delayed local extinctions after the disturbance event. Native and non-native species richness was negatively correlated with elevation, but that relationship diminished over time, with the abundance of non-natives significantly increasing at higher elevations. Synthesis and applications. Transport corridors seem to facilitate the spread of non-native species to higher elevations, which has serious implications considering the warming mountain tops. Our results indicate that the plant communities next to railways do not reach equilibrium quickly after a disturbance. More than 10 years after railway establishment within Kashmir Himalaya, succession continued, and signs pointed towards a landscape increasingly dominated by non-native species. Our study indicates that the single disturbance event associated with constructing railway in this Himalayan region had large and long-lasting effects on plant communities at and around this transport corridor and suggests the need for a long-term region-wide coordinated monitoring and management program.

Crops worldwide are simultaneously affected by weeds, which reduce yield, and by climate change, which can negatively or positively affect both crop and weed species. While the individual effects of environmental change and of weeds on crop yield have been assessed, the combined effects have not been broadly characterized. To explore the simultaneous impacts of weeds with changes in climate-related environmental conditions on future food production, we conducted a meta-analysis of 171 observations measuring the individual and combined effects of weeds and elevated CO2, drought or warming on 23 crop species. The combined effect of weeds and environmental change tended to be additive. On average, weeds reduced crop yield by 28%, a value that was not significantly different from the simultaneous effect of weeds and environmental change (27%), due to increased variability when acting together. The negative effect of weeds on crop yield was mitigated by elevated CO2 and warming, but added to the negative effect of drought. The impact of weeds with environmental change was also dependent on the photosynthetic pathway of the weed/crop pair and on crop identity. Native and non-native weeds had similarly negative effects on yield, with or without environmental change. Weed impact with environmental change was also independent of whether the crop was infested with a single or multiple weed species. Since weed impacts remain negative under environmental change, our results highlight the need to evaluate the efficacy of different weed management practices under climate change. Understanding that the effects of environmental change and weeds are, on average, additive brings us closer to developing useful forecasts of future crop performance.