Long-term ecological monitoring has contributed substantially towards advancements in theoretical and applied ecology. However, the costs to maintain a long-term monitoring site are enormous. ...Lightweight unmanned aerial vehicles (UAVs or drones) have been rapidly emerging as a new tool for local-scale monitoring. To evaluate the value of drone applications in long-term ecological studies, we combined drone-derived canopy variables, detailed ground-based stem-mapping data and topographic and edaphic variables from a 20-ha forest dynamics plot in a species-rich subtropical forest. Specifically, we evaluated the relative importance of these variables in explaining local-scale variation in forest stand and species measures. We found that drone-derived canopy variables contributed substantially towards explaining local patterns of biodiversity and more specifically in supporting a gap dynamics hypothesis in structuring observed forest biodiversity. Stand basal area was positively related with canopy closure, indicating the importance of protecting old-growth forests as carbon sinks. The importance of topographic and edaphic variables was also demonstrated, supporting a niche differentiation hypothesis in structuring patterns in biodiversity. Species-level analyses illustrated that light-demanding species were more strongly correlated with canopy variables than shade-tolerant species. We provide convincing evidence that drones can add substantial value to long-term ecological monitoring by providing low cost, high resolution data. Drones should be included in the ecologist's toolbox to complement traditional field surveys.
•We used a lightweight drone to map in detail forest canopy structure across a 20-ha subtropical forest dynamics plot.•We examined the added benefit of incorporating drone-derived variables in explaining local variation in both stand and species measures.•Drone-derived canopy variables contributed substantially towards explaining spatial patterns in biodiversity.•Species with different light requirements responded to canopy variables supporting gap dynamics successional theories.•Lightweight drone technologies offer great potential for long-term ecological studies.
Winter low temperature disturbance in the southern subtropics has important effects on the weed community structure, but the role of uniquely low temperatures in biological invasions is unclear. ...Here, we examined the competitive effects of an invasive plant,
Bidens pilosa
L., and its native congener,
Bidens biternata
(Lour.) Merr. et Sherff, during high and low temperature seasons to determine whether low temperatures promote the competitiveness of
B. pilosa
in the southern subtropics of China. The growth and physiological responses of the two
Bidens
species to low (10/5 °C) and optimum (30/25 °C) temperatures were examined to determine how the invasive
B. pilosa
responds to low temperature stress
.
Our results showed that the competitive balance index values of
B. pilosa
in low temperature seasons were significantly higher than those in high temperature seasons, which implied that low temperatures may be more beneficial to the competitiveness of
B. pilosa
than high temperatures in the southern subtropics. The smaller decline in the relative growth rate and the photosynthetic ability of
B. pilosa
compared with
B. biternata
under low temperature stress indicated that the former was less negatively affected by low temperature than the latter. A higher DPPH
·
(1.1-diphenyl-2-picrylhy-drazyl) scavenging rate and greater heat-stable protein content in
B. pilosa
under low temperatures might help the invasive plant to maintain more effective physiological functions and thus a higher growth rate. Overall, the uniquely low temperature in the southern subtropics of China is expected to promote the invasiveness of the exotic
B. pilosa
.
1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true ...for forests, which represent a majority of global biomass, productivity and biodiversity. 2. Here, we conduct an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8-50 ha from across the world. The data were collected using standardized protocols, obviating the need to correct for methodological differences that plague many studies on this topic. 3. We found that at very small spatial grains (0.04 ha) species richness was generally positively related to productivity and biomass within plots, with a doubling of species richness corresponding to an average 48% increase in productivity and 53% increase in biomass. At larger spatial grains (0.25 ha, 1 ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04 ha spatial grain, a doubling of species richness corresponded to a 5% increase in productivity and 7% increase in biomass. Productivity and biomass were themselves almost always positively related at all spatial grains. 4. Synthesis. This is the first cross-site study of the effect of tree species richness on forest biomass and productivity that systematically varies spatial grain within a controlled methodology. The scale-dependent results are consistent with theoretical models in which sampling effects and niche complementarity dominate at small scales, while environmental gradients drive patterns at large scales. Our study shows that the relationship of tree species richness with biomass and productivity changes qualitatively when moving from scales typical of forest surveys (0.04 ha) to slightly larger scales (0.25 and 1 ha). This needs to be recognized in forest conservation policy and management.
What causes variation in species abundance for a given site remains a central question in community ecology. Foundational to trait-based ecology is the expectation that functional traits determine ...species abundance. However, the relative success of using functional traits to predict relative abundance is questionable. One reason is that the diversity in plant function is greater than that characterized by the few most commonly and easily measurable traits. Here, we measured 10 functional traits and the stem density of 101 woody plant species in a 200,000 m
2
permanent, mature, subtropical forest plot (high precipitation and high nitrogen, but generally light- and phosphorus-limited) in southern China to determine how well relative species abundance could be predicted by functional traits. We found that: (1) leaf phosphorus content, specific leaf area, maximum CO
2
assimilation rate, maximum stomata conductance, and stem hydraulic conductivity were significantly and negatively associated with species abundance, (2) the ratio of leaf nitrogen content to leaf phosphorus content (
N:P
) and wood density were significantly positively correlated with species abundance; (3) neither leaf nitrogen content nor leaf turgor loss point were related to species abundance; (4) a combination of
N:P
and maximum stomata conductance accounted for 44% of the variation in species’ abundances. Taken together, our findings suggested that the combination of these functional traits are powerful predictors of species abundance. Species with a resource-conservative strategy that invest more in their tissues are dominant in the mature, subtropical, evergreen forest.
Environments in both biotic and abiotic ecosystems have been affected by the colonization of non-native flora. In this study, we examined the effect of Bidens alba invasion on different land-use ...types along a coastline in southern China. Bacterial communities in each site were determined using 16S rDNA sequencing, and soil physicochemical properties were analyzed using standard methods. Although our results indicated that B. alba invasion did not have a significant effect on the alpha diversity of bacteria, it caused significant differences in soil bacterial community composition between invaded and uninvaded soil across different land-use types. Beta diversity and several physicochemical properties in forest, orchard and waterfront environments were recorded to be more susceptible to B. alba invasion. A high proportion of the variation of bacterial communities can be explained by a combination of environmental variables, indicating that environmental selection rather than plant invasion is a more effective process in coastal microbial assemblages. By comparing topological roles of shared OTUs among invaded and uninvaded soil, keystone taxa in invaded soil were identified. Acidobacteria was the major phyla involved in the invasive process which could be driven by environmental selection. How key phyla react in our experiment should be verified by further studies.
Climate is widely recognised as an important determinant of the latitudinal diversity gradient. However, most existing studies make no distinction between direct and indirect effects of climate, ...which substantially hinders our understanding of how climate constrains biodiversity globally. Using data from 35 large forest plots, we test hypothesised relationships amongst climate, topography, forest structural attributes (stem abundance, tree size variation and stand basal area) and tree species richness to better understand drivers of latitudinal tree diversity patterns. Climate influences tree richness both directly, with more species in warm, moist, aseasonal climates and indirectly, with more species at higher stem abundance. These results imply direct limitation of species diversity by climatic stress and more rapid (co‐)evolution and narrower niche partitioning in warm climates. They also support the idea that increased numbers of individuals associated with high primary productivity are partitioned to support a greater number of species.
Plant functional traits are rarely used in tree species classification, and the impact of vertical canopy positions on collecting samples for classification also remains unclear. We aim to explore ...the feasibility and effectiveness of leaf traits in classification, as well as to detect the effect of vertical position on classification accuracy. This work will deepen our understanding of the ecological mechanism of natural forest structure and succession from new perspectives. In this study, we collected foliar samples from three canopy layers (upper, middle and lower) and measured their spectra, as well as eight well-known leaf traits. We used a leaf hyperspectral reflectance (LHR) dataset, leaf functional traits (LFT) dataset and LFT + LHR dataset to classify six dominant tree species in a subtropical evergreen broad-leaved forest. Our results showed that the LFT + LHR dataset achieved the highest classification results (overall accuracy (OA) = 77.65% and Kappa = 0.73), followed by the LFT dataset (OA = 74.26% and Kappa = 0.69) and the LHR dataset (OA = 69.06% and Kappa = 0.63). Along the vertical canopy, the OA and Kappa increased from the lower to the upper layers, and the combination data of the three canopy layers achieved the highest accuracy. For the individual tree species, the shade-tolerant species (including Machilus chinensis, Cryptocarya chinensis and Cryptocarya concinna) produced higher accuracies than the light-demanding species (including Schima superba and Castanopsis chinensis). Our results provide an approach for enhancing tree species recognition from the plant physiology and biochemistry perspective and emphasize the importance of vertical direction in forest community research.
Climate‐driven changes in phenology have widespread effects on ecological interactions and species' abundances. Most predictions of changes in phenology and the consequences for ecology and ...conservation are based on research in temperate systems. Climate‐driven changes in phenology are largely undocumented in subtropical regions, which host much of the world's biodiversity. Factors important to regulating phenology in temperate systems (e.g. winter chilling requirements) are likely weak or absent in subtropical ecosystems; plant phenology in these regions could respond to climate differently than in the temperate zone. Here we examine flowering phenology data for 105 plant species based on herbarium specimens and photographs from 1911 to 2015 in the southern subtropical Nanling region in south China. Temperatures in this region warmed 0.3°C over the 105‐year study period, and most plant species flowered earlier over time, although species varied substantially in the magnitude of phenological response to warming temperatures. Spring flowering times advanced in response to warming temperatures in late summer and early autumn and in early spring, with late summer and early autumn temperatures having almost twice as strong an effect on spring flowering times as early spring temperatures (−4.7 versus −2.5 days °C−1). This strong effect of late summer and early autumn temperatures is very different from temperate systems and has substantial implications for anticipating future changes in phenology. The temperatures in late summer and early autumn may affect spring phenology by accelerating bud formation or initial growth. Warming January temperature delayed summer flowering and advanced winter flowering. Increases in precipitation during April to June also tended to delay summer flowering. Autumn flowering species showed inconsistent responses to warming. These results highlight important differences between climate‐driven changes in phenology in temperate and subtropical areas. Understanding these differences will be important in understanding the effects of climate change on vegetation phenology and ecosystem processes.
Functional diversity is considered a key link between ecosystem functions and biodiversity, and forms the basis for making community diversity conservation strategies. Here, we chose a subtropical ...forest community in China as the research object, which is unique in that other regions of the world at the same latitude have almost no vegetation cover. We measured 17 functional traits of 100 plant species and calculated seven different functional diversity indices, based on functional richness, evenness, and divergence. We found that most functional diversity and species diversity indices significantly differed with plant habit. There was a significant positive correlation among functional richness indices. However, functional divergence indices, multidimensional functional divergence (FDiv), and Rao’s quadratic entropy index (RaoQ) were significantly negatively correlated, and RaoQ and functional divergence indices (FDis) were uncorrelated. The correlations between three types (richness, evenness, and divergence) of functional diversity indices and three species diversity indices were different. Lineage regression results generally showed that three functional richness indices (Average distance of functional traits (MFAD), Functional volume (FRic) and Posteriori functional group richness (FGR)) were increased with three species diversity indices (species richness (S), Shannon-Wiener index (H) and Pielou index (E)). The functional evenness index (FEve) decreased with species richness (S), Shannon-Wiener index (H) and increased with species evenness (Pielou index (E)), but the change trends were small. All three types of functional diversity indices declined with altitude, although altitude had a weak influence on them. Other environmental factors affected the functional diversity of the community. Here, soil total phosphorus (TP) was the most critical environmental factor and the convex had the least effect on functional diversity in our subtropical forest community. These results will contribute to our understanding of functional diversity in subtropical forests, and provide a basis for biodiversity conservation in this region.
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