Linking Forest Diversity, Structure and Functions along the Climate and Soil Conditions across Pakistan

Abstract

In recent decades the relationships between forest diversity, structure, and function have been one of the major topics in the field of ecosystem functioning research. The relationship between forest diversity, structure, and function might vary in different ecosystems. The Variation is not only because of the natural processes and anthropogenic disturbance but is great because of changes in environmental conditions i.e. climate and soil. To understand the effect of various climatic and soil conditions on forest diversity, structure, and function it is important to predict how forests will respond to global environmental change and influence forest function and services. At a small or local scale forest diversity, structure, and function might not be determined by climatic conditions e.g. temperature and precipitation but might be determined by topographic and soil conditions. At large regional scale forest diversity, structure, and function might be greatly associated with climatic conditions and less extent to soil conditions. In the current research work, we evaluate the relationship between forest diversity structure and function along the climate and soil conditions across Pakistan. We collect forest inventory data from 220 forest plots and use the structure equation model a powerful integrative tool to evaluate the relationship between forest diversity structure and function along the climate and soil conditions across six forest types of Pakistan i.e., subtropical thorn forests, sub-tropical broad-leaved forests, moist temperate mix forests, dry temperate conifer forests, dry temperate Quercus forests, and dry temperate Pinus gerardiana (Chilgoza) forest. The objectives of the current study are as follows; (1) to describe the relationship between Environment, Diversity, and Aboveground Biomass (AGB). (2) Relationship between, stand structure diversity, and aboveground biomass in single and multi-species forests. (3) To clarify the role of big trees in the natural forest ecosystem of Pakistan. (4) To understand the role of multiple biotic and abiotic drivers of aboveground biomass in the natural forest ecosystem of Pakistan. (5) To disentangle the carbon sequestration and its biotic and abiotic determinants in different forest ecosystems of Pakistan. The findings underscore the significant impact of climatic and soil conditions, topography, and stand structure diversity on AGB and carbon sequestration. Favorable climates, characterized by higher precipitation and moderate temperatures, along with nutrient-rich soils, are identified as key contributors to increased AGB. Stand structure diversity, particularly Shannon diversity, is highlighted as a facilitator of aboveground biomass productivity, emphasizing the positive influence of both overstorey and understory diversity. The study reveals that single and multi-species forests respond similarly to aboveground biomass dynamics, with big trees positively affecting AGB but potentially limiting the growth of other trees. Topographical factors, such as isolation, play a role in the distribution of big trees, impacting AGB dynamics. Biotic variables, including communityweighted traits mean and stand structure diversity, emerge as crucial determinants across forest types. Abiotic variables, such as soil composition and climate, interact with biotic determinants to influence aboveground biomass. Soil micronutrients and precipitation are identified as major contributors to biomass productivity, while soil macronutrients, wind pressure, and relative humidity have adverse effects in terms of carbon sequestration, climatic factors, especially temperature, precipitation, relative humidity, and wind pressure, play substantial roles, with soil characteristics, particularly in harsh climates, significantly contributing to carbon sequestration. Overall, our study provides comprehensive insights into the complex relationships shaping forest ecosystems in Pakistan, shedding light on the role of diversity, structure, and environmental factors in determining aboveground biomass and carbon sequestration. Based on the current research more detailed studies are required to investigate the complex relationship between forest diversity structure and function in different forest ecosystems of Pakistan.