Climate and human induced 2000-year vegetation diversity change in Yunnan, southwestern China

Abstract

Understanding long-term vegetation diversity patterns and their potential responses to climate and/or human driven processes are important for ecosystem modeling and conservation. Late-Holocene fossil pollen assemblage and associated vegetation diversity estimates provide an opportunity to explore the interactions among vegetation, climate, and human activities. A continuous 2000-year palynological record was obtained from the Beihai Wetland, southwestern China, to represent regional vegetation history, particularly the vegetation diversity changes. The results indicate that regional vegetation was dominated by deciduous broadleaved forest components (e.g. Alnus, deciduous Quercus), which showed a gradual decrease accompanied by expansion of herbaceous taxa (mainly Poaceae) after AD 800. Such progressive decline of forest was attributed to regional deforestation driven by intensified human activities, which was further confirmed by the increasing non-pollen polymorph abundance, particularly an abrupt rise after AD 1350. Vegetation diversity based on the Hill numbers ( N0, N1, and N2) showed a dramatic decline between ca. AD 200–400, which was triggered by regional fire events as shown by increased charcoal abundance from a nearby lake. The vegetation diversity reduced gradually after AD 800, especially the vegetation richness reflected by N0, revealing the transitional process from climate-driven to human-dominated vegetation changes. Minor increases of vegetation diversity occurred during Chinese dynastical transitions, probably due to reduced human activities following war-induced population crises. On the multidecadal scale, variations in vegetation diversity correlated significantly with climate fluctuations (revealed by synthesized temperature of China and stable oxygen isotope record from Dongge Cave) before AD 800, indicating a climate dominant condition. Then, the correlation between vegetation diversity and climate declined after AD 800, representing a progressive transition to human-dominant condition. In addition, the compositional turnover based on DCCA of the fossil pollen assemblage revealed a stepwise decrease, indicating reduced vegetation turnovers under anthropogenic influences.

A 1640-Year Vegetation and Fire History of the Lake Haixihai Catchment in Northwestern Yunnan, Southwest China

“…At this substage, the Lake Erhai basin was governed by separate tribes and Yunnan had a low population (Figure 9h,i) [60,61], implying the least impact on vegetation from human activities over the last 1640 years. Less human-induced impact on vegetation at this substage was also revealed by pollen records from Lakes Erhai [12], Tiancai [22], Tengchong Qinghai [24,62,63], Lugu [64], and Xingyun [15] as well as the Beihai wetland [8,65] in Yunnan. The Lake Haixihai catchment witnessed the densest vegetation consisting of more pine and hemlock forests and less evergreen broadleaved forests at substage III-2, when both regional temperatures and precipitation underwent a process of dropping, lower than the present, and rising to higher than the present although they did not change in completely synchronous way.…”

“…Environmental changes involve vegetation or land cover change and fire or biomass burning variability. Previous studies have shown that spatial and temporal patterns of vegetation and fire driven by natural and anthropogenic forcings are significantly different on various spatial scales in the world, China, and even Yunnan over the last two millennia [5][6][7][8]. Obviously, more records are needed to develop a detailed picture of regional vegetation changes and fire regimes so that we may understand their global temporal and spatial patterns and dominant driving forcings over the last two millennia.…”

Analysis of Indigenious Vegetation Diversity in Urban Area of Bekasi Regency

“…Debouk et al (2015) emphasized the significance of comprehending the reaction of community plant functional traits to rising temperatures and their contribution to the stability of vegetation. The study conducted by Wang et al 2021) demonstrates a substantial association between changes in vegetation diversity and fluctuations in climate, suggesting a climate-dominant condition.…”